APTD -
Low NOx Emission Combustor
for Automobile Gas Turbine Engines
(Northern Research and Engineering Corporation)
Prepared By
E. P. Demetri and R. J. Murad
Northern Research and Engineering Corporation
219 Vassar Street
Cambridge, Massachusetts 02139
CONTRACT NUMBER: 68-0^-001?
EPA Project Officers
H. F. Butze and Robert B. Schulz
Prepared For
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Mobile Source Pollution Control Program
Advanced Automotive Power Systems Development Division
Ann Arbor, Michigan ^8105
February 1973
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APTD - 1454
Low NOx Emission Combustor
for Automobile Gas Turbine Engines
(Northern Research and Engineering Corporation)
Prepa red By
E. P. Demetri and R. J. Murad
Northern Research and Engineering Corporation
219 Vassar Street
Cambridge, Massachusetts
02139
CONTRACT NUMBER:
68-04-0017
EPA Project Officers
H. F. Butze and Robert B. Schulz
Prepared For
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Mobile Source Pollution Control Program
Advanced Automotive Power Systems Development Division
Ann Arbor, Michigan
48105
February 1973
-------
APTD - 1454
Low NOx Emission Combustor
for Automobile Gas Turbine Engines
(Northern Research and Engineering Corporation)
Prepa red By
E. P. Demetri and R. J. Murad
Northern Research and Engineering Corporation
219 Vassar Street
Cambridge, Massachusetts
02139
CONTRACT NUMBER:
68-04-0017
EPA Project Offi cers
H. F. Butze and Robert B. Schulz
Prepared For
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Mobile Source Pollution Control Program
Advanced Automotive Power Systems Development Division
Ann Arbor, Michigan
48105
February 1973
-------
The APTD (Air Pollution Technical Data) series of report is issued
by the Office of Air and Water Programs, U.S. Environmental Pro-
tection Agency, to report technical data of interest to a 1 imited
number of readers. Copies of APTD reports are available free of
charge to Federal employees, current contractors and grantees, and
non-profit organizations - as suppl ies permit - from the Air Pollu-
tion Technical Information Center, U.S. Environmental Protection
Agency, Research Triangle Park, North Carol ina 27711 or may be
obtained for a nominal cost, from the National Technical Information
Service, U.S. Department of Commerce, 5285 Port Royal Road, Spring-
field, Virginia 22151.
This report was furnished to the U.S. Environmental Protection Agency
by Northern Research and Engineering Corporation, Cambridge, Massa-
chusetts, in fulfillment of Contract Number 68-04-0017. The contents
of this report are reproduced herein as received from Northern Research
and Engineering Corporation. The opinions, findings, and conc1usions
expressed are those of the author and not necessarily those of the
Environmental Protection Agency.
Office of Air and Water Programs Publ ication Number APTD - 1454
-------
The program reported here was carried out under the technical
direction of Dr. D. M. Dix with Mr. E. P. Demetri assuming project
responsibil ities. Other participants in the program included Mr. R. J.
Murad and Mr. P. R. Smith; Professor A. H. Lefebvre, Professor J. B.
Heywood, and Mr. E. R. Norster served in a consulting capacity during
the course of the program.
This program was sponsored by the Environmental Protection
Agency under Contract No. 68-04-0017. Technical monitoring of the
program was conducted by Mr. H. F. Butze of NASA Lewis and Mr. R. B.
Schulz of EPA.
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!-
TABLE OF CONTENTS
SUMMARY. . .
INTRODUCTION
. . . . .
. . . . .
. . . .
. . . . .
. . . . . .
. . . .
. . . .
. . . .
. . . . . . .
. . . .
. . . . .
Background. . . . . . . . . . . . . . . . . . . . .
Problem Definition. . . . . . . . . . . . . . . . . . . .
Method of Attack
. . . . . . .
. . . . .
. . . . . .
Report Arrangement
. . . . .
. . . . . .
. . . . .
. . . .
DESIGN APPROACH FOR REDUCING EMISSIONS
. . . . . .
. . . . .
. . . .
Emission Goals
. . . . . . .
. . . . . .
. . . . .
. . . .
Major Factors in Emissions of NOx .
Control of NOx Emissions. . . . .
. . . . .
. . . .
. . . . .
. . . .
DESIGN OF COMBUSTORS
. . . . .
. . . . .
. . . . . . .
. . . .
Cycle Conditions. . . .
Combustor Design Conditions. .
Aerothermodynamic Design
. . . .
. . . . . .
. . . .
. . . . .
. . . . . .
. . . . . .
. . . . .
Mechanical Design
. . . . . .
. . . . .
. . . .
COLD-FLOW TESTS. . . . . . .
. . . . .
. . . . . . .
. . . . .
Water-Visualization Tests
Air Flow Distribution Tests. .
. . . . .
. . . . .
. . . . .
. . . .
Nozzle Spray Visualization Tests
. . . .
. . . . . .
COMBUSTION TESTS
. . . . . . .
. . . . .
. . . . .
. . . . .
. . . .
Over-All Approach. . . . . . . . . . . . . . . . . . . . .
Discussion of Test Results for Combustor B . . . . . . . .
Discussion of Test Results for Combustor A . . . . .
Analysis of Results. . .
. . . . . . .
. . .. .
. . . . . .
Experimental Verification of Analysis
. . . . . . . .
Recommended Approaches for Achieving Low Emissions
. . . .
CONCLUSIONS AND RECOMMENDATIONS.
. . . . .
. . . .
. . . . . .
Conclusions. . . .
. . . . .
. . . . . . . . . . .
. . . .
Recommendations. . . .
. . . . . .
. . . . . . . .
. . . .
REFERENCES
. . . . . . . . . .
. . . . .
. . . .
. . . . . . . . . .
- i -
.
4
4
4
6
9
10
10
11
13
19
19
21
25
27
29
29
31
32
35
35
37
42
45
50
53
57
57
59
62
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TABLES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65
FIGURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
NOMENCLATURE. . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
APPEND ICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
I - DESCRIPTION OF EXPERIMENTAL FACILITIES. . . . . . . . 161
II - DATA REDUCT ION. . . . . . . . . . . . . . . . . . . . 167
I I' - NOZZLE SPRAY ANALYSIS TESTS. . . . . . . . . . . . . . 171
- i i -
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L1 ST OF TABLES
Table I: Federal 1975176 Emission Goals . . . . . . . . . . . . 66
Tab1e II: Assumed Cycle Operating Conditions for Design
of Combustors . . . . . . . . . . . . . . . . . 67
Table III: Selected Combustor Design Conditions . . . . . . . . . 68
Table IV: Design Distributions of Ai rflow . . . . . . . . . 69
Table V: Nozzle Design Specifications . . . . . . . . . . . . . 70
Table VI: Metering and Bleed Hole Dimensions . . . . . . . . . . 71
Table VII: Average Values of Effective Flow Areas Calculated
from Results of Co 1 d -A i r Tests . . . . . . . . . 72
Table VIII: Summary of Test Conditions Examined with
Combustor B . . . . . . . . . . . . . . . . . . . . . . 74
Table IX: Results of Combustion Tests for Combustor B wi th
Nozzle B1.1 and "Closed" Variable-Geometry Sett i ng 76
Table X: Results of Combustion Tests for Combustor B wi th
Nozzle B1.1 and "Fu 11 Open" Variable-Geometry
Sett i ng . . . . . . . . . . . . . . . 79
Table X I: Results of Combustion Tests for Combustor B wi th
Nozzle 82. 1 and tIC losed" Variable-Geometry
Sett i ng . . . . . . . . . . . . . . . 82
Tab Ie X II: Results of Combus t i on Tests for Combustor B with
Nozzle B2. 1 and "F u 11 0 pe nil Variable-Geometry
Sett i ng . . . . . . . . . . . . . . . . . . . . . 84
Table X, II: Results of Combustion Tests for Modified Combustor
8 with Nozzle B2. 1 and "Closed" Variable-Geometry
Sett i ng . . . . . . . . . . . . . . . . . . . . . . . 85
Table XIV: Summary of Test Conditions Examined with
Combustor A . . . . . . . . . . . . . . . . . . . . . . 87
Table XV: Results of Combustion Tests for Combustor A with
NozzleA2.1 and IIC losed" Variable-Geometry Sett i ng 88
Table XVI: Results of Combustion Tests for Combustor A wi th
Nozzle A2.1 and "Part Open" Variable-Geometry
Setting . . . . . . . . . . . . . . . . . . . . 91
Table XV II: Summary of Test Conditions Examined with Modified
Combustor A . . . . . . . . . . . . . 94
Table XV III: Calculated Nozzle and Swirler Air Flows for
Modified Combustor A . . . . . . . . . . . . . . 95
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Table
XIX:
Table
Table
XX I:
Table XXII:
Table XXIII:
Table XXIV:
Table XXV:
Tab le XXVI:
XX:
Results of Combustion Tests for Modification No.1
of Combustor A with Nozzle A2.2 and "Closed"
Swirler Setting. . . . . . . . . . . . . . . . . . . .
Results of Combustion Tests for Modification No.1
of Combustor A with Nozzle A2.2 and l'Open"
Swi r 1 er Sett i ng . . . . . . . . . . . . . . . . . . . .
Results of Combustion Tests for Modification No.2
of Combustor A with Nozzle A2.2 . . . . . . .
Hot-Test Measurements
. . . . . .
. . . .
. . . .
Radial Coordinates of Exit Temperature Traverse
for Each Thermocouple Probe. . . . . . . .
Specifications of the Emission Instruments
Hot Rig Flow Conditions Modeled in Conducting
Spray Analysis Tests of Nozzle A2.2 . . ; . .
Experimentally Determined Droplet Size Distribution
for Nozz 1 e A2. 2 . . . . . . . . . . . . . . . . . .
- i v -
96
98
. . 100
101
. . . 102
. . . 103
. . 104
. . 105
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Figure
Figure 2:
Figure 3:
Figure 4:
Figure 5:
Figure 6:
Figure 7:
Figure 8:
Figure 9:
Figure 10:
Figure 11:
Figure 12:
Figure 13:
Figure 14:
F i gu re 15:
Figure 16:
F i gu reI 7 :
Figure 18:
Figure 19:
Figure 20:
LI ST OF FIGURES
1 :
Effects of Fuel Distribution on predicted NO Emission
Rate for Representative Aircraft Gas Turbine
Combustor (Ref 2) . . . . . . . . . . . . . . . . . . . . 107
Combustion Performance Map for Fixed and Variable-
Geometry Combustors. . . . . . . . . . r . . . . . .
. . 108
109
General Configuration of a Pi loted Airblast Nozzle
Diagrammatic Representation of Class A and Class B
Cyc 1 es . . . . . . . . . . . . . . . . . . . . . . 110
General Confi"guration of Combustors. . . . . . . . . . . 111
Final Design Configurations . . . . . . . . . 112
Radial SwirlerDesign........... ....113
Airblast Nozzle Configuration. . . . . . . . 114
Estimated Axial Distributions of Liner Temperature. . . 115
Variable-Geometry Configuration. . . . . . . . . . . . . 116
General Flow Pattern Observed in Flow Visualization
T es t s . . . . . . . . . . . . . . . . . . . . . . .
. . . 117
Variation of Effective Primary-Zone Flow Rate for
Combus tor A . . . . . . . . . . . . . . . . . . .
Variation of Effective Primary-Zone Flow Rate for
Combustor B . . . . . . . . . . . . . . . . . . .
. . . . 118
. . . . 119
Effects of Nozzle Air Pressure Drop on Spray
Performance. . . . . . . . . . . . . . . . .
. . . . . . 120
Effects of Axial Position of Nozzle on Spray
Performance. . . . . . . . . . . . . . . . . . . . . . . 121
Summary of NOx and CO Emissions for Combustor B . . . . . 122
Summary of Hydrocarbon Emissions (HC) and
Combustion Efficiency ('7c) for Combustor B . . . . . . . 123
Typical Effect of Residence Time on NOx and CO
Emissions for Combustor B . . . . . . . . . . . . . . . . 124
Typical Variation of NOx Emissions with Flow
Conditions"for Combustor B . . . . . .
. . . . . . 125
Effect of Nozzle Air/Fuel Ratio on NOx and CO
Emi ss ions. . . . . . . . . . . . . . . . . .
. . . . . . 126
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Figure 21:
Figure 22:
Figure 23:
Figure 24:
Figure 25:
Figure 26:
Figure 27:
Figure 28:
Figure 29:
Figure 30:
Figure 31:
Figure 32:
Figure 33:
Figure 34:
Figure 35:
Figure 36:
Figure 37:
F i gu r e 38:
Figure 39:
Figure 40:
F i gu re 41:
Figure 42:
Figure 43:
Figure 44:
Figure 45:
Figure 46:
Figure 47:
Comparison of NOx and CO Emissions for Original
and Modified Combustor B Configurations.
Weak Extinction Limit for Combustor B . . . . .
Summary of NOx and CO Emissions for Combustor A . .
Summary of Hydrocarbon Emissions (HC) and
Combustion Efficiency ('7c) for Combustor A . . . . . . . 130
Typical Variation of NOx Emissions with Flow
Conditions for Combustor A . . . .
. . 127
. . 128
129
. . . . . 131
132
. . . . . . . . . . . . 133
134
. . . . . . . . . . . 135
. . . . . 136
137
Weak Extinction limit for Combustor A . . .
Combustor Flow Pattern Schematic
. . . .
Fuel-Air Distribution in Primary-Zone Inlet Region
Calculated Results for Combustor B
Calculated Results for Combustor A
Modifications of Combustor A Tested
. . . .
. . . .
(omparison of NOx and CO Emissions for Original
and Modified Combustor A . . . . . . . . . . . . . . . . 138
Effect of Pressure Drop and Residence Time on NOx
Emissions for Modified Combustor A . . . .
. . . . 139
Effect of Fuel Injection on NOx Emissions for
Modified Combustor A . . . . . . . . . . . . 140
F10w Schematic of Water Rig. . . . . . . . . . . . 141
Flow Schematic of Cold-Air Test Rig. . . . . . . . . . . 142
Nozzle Mounting for Fuel Nozzle Tests. . . . . . . . . . 143
Air Flow Schematic for Combustion Test Rig. . . . 144
Fuel Flow Schematic for Combustion Test Rig. . . . . . . 145
Combustion Test Section. . . . . . . . . . . . . . 146
Thermocouple Probe. . . . . . . . . . . . . 147
Spacing of Thermocouple Probes. . . . . . . . . . 148
Relative Circumferential Orientation of Thermocouple
Probes. . . . . . . . . . . . . . . . . . . . . . . . . 149
Spacing of Gas Sampling Rakes. . . . . . . . . . . . . . 150
Relative Circumferential Orientation of Gas Sampling
Probe 5 . . . . . . . . . . . . . . . . . . . . . . .
. .151
152
Design of Gas Sampling Rakes. . . . . . . . . . .
Sampling Train of Existing NREC Engine Exhaust
Sampling Facility. . . . . . . . . . . . . . . . . . . . 153
- vi -
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Figure 48:
Figure 49:
Experimentally Determined Variation of Mean Droplet
Size with Air Pressure Drop for Airblast Portion
of Nozz I e A2. 2 . . . . . . . . . . . . . . . . . . . . . 154
Experimentally Determined Radial Distributions of
Spray for Airblast Portion of Nozzle A2.2 . . . . . . . . 155
- vi i -
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SUMMARY
This report describes a program sponsored by the Environmental
Protection Agency under Contract No. 68-04-0017 as part of the continuing
research and development effort aimed at demonstrating an automotive gas
turbine engine capable of meeting the Federal 1975/76 emission standards.
The program consisted of the design and testing of two low-emission
research combustors for automotive gas turbine appl ications, one of which
was representative of low pressure-ratio, regenerative gas turbine cycles
and the other representative of high pressure-ratio, nonregenerative
cycles. The goal in the de,sign of the combustors was to achieve emission
levels not exceeding one-half of the Federal 1975/76 emission standards.
The over-all objective of the program was to develop design guidel ines
on the basis of detailed experimental data which could be used to design
automotive gas turbine combustors capable of achieving the specified
emission goals.
The approach adopted for control 1 ing the emissions involved
extensive modifications to conventional combustor configurations, but
made direct use of existing combustor design technology. The specific
approach uti 1 ized was selected on the basis of results obtained in
previous programs conducted by NREC deal ing with the predicti~n and
control of NOx emissions, and consisted of designing both combustors
to operate with a lean, well-mixed primary zone over the full range of
operating conditions. The necessity of operating with a lean primary zone,
required the use of variable geometry to control the combustor air flow
distribution 50 as to maintain stable and efficient combustion over the
combustor operating range. Inasmuch as the uniformity of the fuel/air
mixture depends on the aerodynamic design of the combustor as well as
the manner in which fuel is introduced, both variable-geometry combustors
were designed for a relatively high value of pressure-loss factor in
order to promote aerodynamic mixing.
The diameter of each combustor was
somewhat oversized to accompl ish the high-pressure loss factor and also
to aid in reducing CO and HC emissions. With regard to fuel injection,
the approach adopted was to use an airblast type of fuel nozzle which
was expected to aid in achieving a reasonably uniform fuel/air mixture
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2
combustors
Full-scale
in the primary zone of the cqmbustor.
Using the over-all approach discussed above, each of the two
was designed as a single-can, throughflow configurati~:>n.
models of both combustors were fabricated and tested over
wide ranges of operating conditions representative of typical driving
cycles. Two types of tests were conducted-- cold-flow tests to measure
aerodynamic performance and detailed combustion tests to measure emission,
combustion, and thermal performance.
The test results showed that in general the NOx emissions
obtained were higher than the goal whereas CO and HC emissions were
satisfactory along with the measured values of the more conventional
combustor performance parameters such as combustion efficiency, stabil ity
I imits, pressure loss, exit temperature traverse qual ity, and combustor
wall temperature. A critical analysis of the test data was performed to
determine the effects of the major parameters on emission performance and
to identify specifically the causes of the high NOx emissions. This
analysis included use of the analytical model previously developed by
NREC for predicting the formation and emission of NOx in gas turbine
combustors. Both the experimental and analytical results indicated that
the high NOx emissions were principally due to inadequate fuel/air mixing
in the primary zone. This in turn was due to inadequate distribution of
the fuel spray in the nozzle and swirler airstreams and insufficient
proportion of the primary-zone air flow through the nozzle/swirler assembly
relative to the flow through the secondary holes. These conclusions
were verified experimentally by conducting an additional series of tests
with modified combustor configurations.
The results of this test series
indicated that the NOx emission goals could be met by improving the
uniformity of the primary-zone fuel/air distribution. Specific modifica-
tions of the method of fuel injection were identified which if imple-
mented should result in achieving the emission goals with the existing
combustor configurations.
Despite the fact that not all of the emission goals were met,
the experimental evidence obtained in the program demonstrates that the
variable-geometry concept util ized has the potential of producing the
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3
necessary reductions in emission levels.
The major conclusion reached
on the basis of the program results is that the specified emission goals
can be achieved with modifications of essentially conventional combustor
configurations uti I izing the approaches identified in the program, and
that further development of this concept is warranted.
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4
INTRODUCTION
Backqround
The motor vehicle is the greatest single contributor to the
increasingly serious health hazard of air pollution, producing some
60 per cent of the pollutants released into the atmosphere in the United
States. In recognition of this fact and in accordance with the require-
ments of the Clean Air Act of 1970, the Environmental Protection Agency
has prescribed standards regulating the emissions of nitrogen oxides,
carbon monoxide, and hydrocarbons from new motor vehicles effective with
the 1975/76 model years.
Although research, development, and legislation
are resulting in significant reductions in pollutant emissions from con-
ventional internal combustion engines, it is possible that in the long
term these may be replaced by alternative power units. The gas turbine
engine represents an attractive alternative as a source of power for
automotive appl ications because of its inherently low level of pollutant
emissions. For this reason, the Environmental Protection Agency is spon-
soring a number of programs representing a concerted research and devel-
opment effort aimed at demonstrating a practical automotive gas turbine
engine which meets the Federal 1975/76 emission goals. Since the com-
bustor is the critical factor with regard to emissions, most of this
effort has been directed towards establ ishing a combustor design concept
capable of achieving the specified emission goals. The program described
in this report was sponsored by EPA under Contract No. 68-04-0017 as
part of this effort and consisted of the design and testing of two low-
emission research combustors for automotive gas turbine appl ications.
Problem Definition
Two types of gas turbine cycles having potentially different
emission characteristics are the primary candidates for use in automotive
appl ications-- the regenerative cycle and the simple or nonregenerative.
cycle. In both cases, the combustor is the major component from the
standpoint of emissions.
The most practical and direct approach to the
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5
control of all pollutant species is to design the combustor itself properly
rather than attempt to treat the exhaust products. A major problem in
designing for a low over-all level of emissions is the fact that operating
conditions leading to a reduction in some pollutant species favor the
formation of others. For example, decreasing the temperature of the primary
zone reduces the production of nitric oxide, the major pollutant problem
in gas turbine engines, but may tend to increase the emissions of carbon
monoxide and unburned hydrocarbons. An additional compl icating factor
is that a gas turbine engine for automotive appl ications does not have a
single operating point, but must function efficiently over a wide range
of conditions.
The combustor has a major effect on cycle performance
and fuel economy over the entire operating range and therefore has to be
designed to satisfy both pollution and performance requirements. Unfor-
tunately, al.l of these requirements are by no means mutually compatible,
and an effective compromise among them must be achieved.
The gas turbine combustor has been studied quite extensively in
the past, particularly with regard to its appl ication in aircraft engines.
Consequently, a great deal of information on the design and development
of conventional combustors is available, and the technology is fairly
well-establ ished. However, until recently, a relatively smal I proportion
of the effort expended on combustors has been devoted to investigating
their emission performance and determining the major factors governing
the formation and emission of the pollutant species of concern. The
program described in this report was oriented towards bridging this gap
in the state-of-the-art by providing information which could be appl ied
directly to the future design and development of low-emission combustors.
This program involved the design and development of two combustors suitable
for automotive gas turbines with the objective of achieving emission levels
not exceeding one-half of the Federal 1975/76 emission goals.
The program consisted of three major tasks. The first
task consisted of the design of the two research combustors, one of
which (designated as Combustor A) was representative of low pressure
ratio, regenerative gas turbine cycles, and the other (designated as
Combustor B) representative of high pressure ratio, nonregenerative cycles.
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6
The primary goal in the design of these combustors was to obtain con-
figur~tions which would be capable of meeting the specified emission
standards. The second task involved fabricating full-scale models of
the selected configurations and preparation of facil ities for their
testing. The final task consisted of detailed testing of the two con-
figurations and critical evaluation of the results obtained.
Method of Attack
Obiectives
The major objective of the program conducted by NREC was to
develop design data and guidel ines which could be used to design auto-
motive gas turbine combustors capable of achieving the specified emis-
sion goals. Thus, an approach was adopted which involved extensive mod-
ifications to conventional combustor configurations, but which made direct
use of present technology; similar1y, the prcgram consisted of designing
the two combustors with the goal of meeting the emission standards insofar
as possible and evaluating the potential of the selected approach by test-
ing the combustors over operating conditions representative of automotive
gas turbine engines.
It was recognized from the outset that, while considerable
reductions in over-all emission levels could be achieved with this
approach, there could be no guarantee that the specified standards could
be met during the course of the program-- the program was not directed
toward the investigation of any novel concepts, representing radical
departures from current practice, which ultimately might have been
required to satisfy the specified emission goals. It was felt strongly
that the latter approach would require development costs and time beyond
the scope of the desired effort, and that in any case the recommended
program was an essential step for the practical solution of the problem
of achieving acceptable emission levels in automotive gas turbine engines.
The major purpose of the program was then to obtain experimental infor-
mation which would identify specifically the steps required to achieve
acceptably low emission levels and provide a firm basis for the 5ub-
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7
sequent design of practical gas turbine combustors which can meet the
specified emission goals.
Desiqn
The major problem in the design of the two combustors was to
arrive at configurations which were capable of achieving low emission levels
of nitrogen oxides (NOx). Evidence obtained by NREC in previous studies
(Refs I, 2, and 3) of this problem showed that NOx emission is a function
of three major factors which can be control led by the combustor designer:
primary-zone equivalence ratio, uniformity of the primary-zone fuel/air
mixture, and residence time. Emissions of NOx decrease as the primary-
zone equivalence ratio departs from unity, the fuel/air mixture is made
more uniform, and the residence time is reduced.
The first two of these
factors have" a significantly greater effect than residence time.
Therefore,
the approach selected for reducing emissions was to design for a lean,
well-mixed primary zone at all operating conditions.
The necessity of operating with a lean primary zone required
the use of variable geometry both to control the combustor air flow
distribution and to maintain low carbon monoxide (CO) and hydrocarbon (HC)
emissions, as well as stable combustion, over the required combustor
operating range. Inasmuch as the uniformity of the fuel/air mixture depends
on the aerodynamic design of the combustor as well as the manner in which
the fuel is introduced, both variable-geometry combustors were designed
for a relatively high value of pressure-loss factor (defined as the
ratio of the pressure drop to the reference dynamic head), in order to
promote aerodynamic mixing.
With regard to fuel injection, the ideal situation would be to
premix the fuel with air prior to entering the combustor. The actual ap-
proach adopted was to use an airblast type of fuel nozzle which was expected
to aid in achieving a reasonably uniform fuel/air mixture in the primary
zone of the combustor.
Since this type of nozzle is still in the develop-
ment stage, it was not possible to specify the required design characteris-
tics exactly. Therefore, six nozzles (two for Combustor A and four for
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8
Combustor B) differing primarily in the amount of nozzle air flow were fab-
ricated for testing.
As wi 11 be shown in a subsequent section of this re-
port, experimental results have indicated that this fuel injection system
is the major deficiency in the over-all approach and requires improvement.
Testinq and Evaluation
Using the over-all approach discussed above, each of the two
combustors was designed as a single-can, throughflow configuration. Full-
scale models of both combustors were fabricated and tested over a wide
range of operating conditions representative of typical driving cycles..
Two types of tests were conducted-- cold-flow tests to measure aerodynamic
performance and detailed combustion tests to measure emission, combustion,
and thermal performance.
The cold-flow tests consisted of flow visual-
ization tests of the combustors and nozzles with water as the flow medium
and pressure loss and flow distribution tests with air.
The combustion
tests consisted of taking complete performance measurements for independ-
ent variations of combustor geometry, fuel nozzle, fuel flow rate, air
flow rate, and combustor inlet temperature and pressure.
The performance
variables measured included air and fuel inlet conditions and flow rates,
exhaust concentrations of the major pollutant species, pressure loss,
I iner temperature, and exhaust gas temperature distribution.
The experimental evaluation of both combustors provided detailed
information on the variations of combustor performance with geometry and
operating conditions. The results obtained were analyzed in detail to
determine the effects on performance (particularly emissions) of independ-
ent variations in the major test parameters. This analysis included
the use of the NOx prediction model previously developed by NREC (Refs 1,
2, and 3) to isolate the major factors contributing to the formation
and emission of NOx. On the basis of the conclusions reached in this
analysis, the original Combustor A configuration was modified for the
purpose of reducing NOx emissions. These conclusions were then verified
experimentally by conducting an additional series of tests with the mod-
ified configuration. The critical evaluation of all of the test results
obtained in the experimental program identified specifically the measures
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9
which must be taken to achieve the emission goals with a practical
combustor configuration.
Report Arranqement
The design approach selected for achieving reduced emissions
is presented in the next section of this report. This is fol lowed by
a section which describes in detail the design procedures employed and
the resulting configurations of the two combustors. The cold-flow tests
and combustion tests are discussed separately in the next two sections.
Each of these two sections contains a description of the tests conducted,
a complete presentation of the results obtained, and a detailed discussion
of the analysis of these results. The final section contains the major
conclusions reached on the basis of the program results and recommenda-
tions regardi~g the appl ication of these results to future efforts in the
design of low-emission gas turbine combustors. The details of the exper-
imental rigs, methods of data analysis, and results of nozzle spray tests
are presented in three appendices.
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10
DESIGN APPROACH FOR REDUCING EMISSIONS
Emission Goals
The major pollutant species of concern with regard to emissions
from gas turbine engines are nitrogen oxides (NOx), carbon monoxide (CO),
hydrocarbons (HC), and particul~tes. The general factors leading to the
emissions of these species are discussed below.
Nitrogen-oxide emissions from gas turbines arise from the
reaction of nitrogen and oxygen in the high-temperature flame region in
the combustors. Nitric oxide, NO, is usually the predominant species
formed in the combustor.
This is oxidized outside the engine to produce
nitrogen dioxide which is the form that plays a large part in the photo-
chemical oxidation of hydrocarbons to produce photochemical smog. Nitric
oxide is formed through the Zeldovich chain reaction mechanism and the
amount produced is kinetically controlled. The formation of nitric oxide
is increased by high oxygen content in the burned gas and long residence
time at high temperature. In terms of the design variables, nitric oxide
formation is increased in various degrees by high combustor air inlet
temperature, high combustor pressure, primary-zone fuel/air ratio near
stoichiometric, and long primary-zone residence time.
The rate of
quenching in the dilution zone is important when the primary-zone mixture
is stoichiometric or richer than stoichiometric.
Carbon monoxide emissions are usually due to the too rapid
quenching of the burned gases. The oxidation of carbon monoxide to
carbon dioxide is the last and slowest step in the kinetic chain of
hydrocarbon combustion, and sufficient time must be available for these
reactions to come to equil ibrium before quenching with dilution air
begins. At the high burned gas temperatures corresponding to near-
stoichiometric combustion in the primary zone, chemical equilibrium
is attained quite rapidly. However, significant amounts of carbon
monoxide are present even when equil ibrium is establ ished. The initial
rate of dilution then should be sufficiently slow so that the carbon
monoxide has time to maintain pace with the equil ibrium shift caused by
the addition of air to the combustion gases. When lean primary zones
are used, the amount of carbon monoxide at equil ibrium is relatively
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11
small.
However, at the lower burned gas temperatures corre?ponding to
the lean conditions, the carbon monoxide oxidation rate is low.
Therefore,
the slow carbon monoxide oxidation in the hydrocarbon reaction chain
is the dominant factor for lean primary zones.
Unburned hydrocarbons are usually caused by local fuel-rich
regions or by fuel droplets which impinge on the I iner walls or are
entrained in the film-cool ing air stream and pass through the hot reaction
zone. Combustion of this fuel does not occur and the fuel is carried
through the combustor without reacting. Some unburned hydrocarbons
arise from the quenching of the hydrocarbon reactions before they have
reached completion.
Particulate emissions from gas turbines are principally in the
form of soot particles (smoke). Soot is usually formed in the fuel-
rich regions flear the fuel nozzle in designs with rich primary-zone
equivalence ratios. A large proportion of the soot formed in this
region is usually consumed in the dilution zone of the combustor.
Smoke
emissions can be controlled by correct attention to el iminating fuel-rich
areas in the combustor primary zone.
The Federal 1975/76 Emission Standards (Ref 4) prescribe maximum
allowable exhaust levels of NOx, CO, and HC based on a specified repre-
sentative driving cycle.
The goals in terms of the emissions from the
combustor are given in Table I. For the program described in this report,
the emission goals in the design of the combustors were to achieve exhaust
levels not exceeding one-half the Federal 1975/76 emission standards.
Although standards for the emissions of particulates have not been
specified as yet, efforts are proceeding to define such standards.
Therefore, it was considered necessary to attempt to reduce particulate
emissions as well as the other species in the design of the combustors.
Maior Factors in Emissions of NOx
As noted previously, the achievement of low emission levels of
nitrogen oxides is
1 ing of emissions.
bustors.
NREC has
the most difficult problem with regard to the control-
This then dictated the conceptual design of the com-
conducted a number of programs (Refs 1, 2, and 3)
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12
deal ing with this problem. The most relevant of these is one sponsored
by the Federal Aviation Administration and the Environmental Protection
Agency which involved the development of improved techniques of predicting
and control I ing the formation of NOx in gas turbine combustors (Refs I and
2). This program has consisted of developing an analytical model of the
kinetic processes by which NO is generated in a combustor and verifying
the model experimentally by conducting emission performance tests of two
representative combustors. The model treats the primary zone as a
partially stirred reactor with a Gaussian distribution of fuel/air
ratios. The uniformity of this distribution is characterized by a mix-
edness parameter*(~o) defined as the ratio of the standard deviation of
the distribution to the mean value of the fuel/air ratio. In accordance
with this definition, decreasing the value of So corresponds to improving
the uniformit.y of the fuel/air distribution; a value of ~= 0 represent-
ing a perfectly mixed system. The evidence obtained by NREC in the
previous studies of NOx has shown that NOx emission is a function of
three
major factors which can be control led by the combustor designer:
I. Primary-zone equivalence ratio ( 4)p , defined as fuel/air
ratio divided by stoichiometric fuel/air ratio).
2. Uniformity of primary-zone mixture (degree of '8mixedness"
as characterized by the value of 50).
3.
Primary zone residence time.
Emission of NOx is also strongly dependent on the combustor inlet tem-
perature. However, this quantity is usually fixed by the cycle conditions
and cannot be altered significantly without compromising cycle efficiency.
Emissions of NOx decrease as the primary-zone equivalence ratio
departs from unity, the fuel/air mixture is made more uniform, and the
residence time is reduced.
It has been found that primary-zone equiv-
alence ratio and degree of mixing have significantly greater effects
on NOx emissions than residence time.
The variation of NOx emissions
with residence time is at most I inear. The combined effects of primary-
zone equivalence ratio and degree of mixing are illustrated by Figure I
which is taken from Reference 2. The results given in the figure were
"
See NOMENC LATURE fa 11 awi ng ma in body of report.
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13
obtained using the analytical model previously developed by NREC and
show the predicted variations of NO emissions with degree of mixedness
at selected values of primary-zone equivalence ratio for a represent-
ative aircraft gas turbine combustor operating at full-power conditions.
At low values of So (well-mixed primary zone), the emission rate decreases
rapidly as the mean primary zone equivalence ratio is decreased from the
stoichiometric value ( CPp = I ); a similar but less rapid decrease in
emissions is observed for values of ;p above unity. At the higher
values of So corresponding t.o a poorly-mixed' primary zone, the effect
of equivalence ratio on emissions is significantly lessened and all but
very lean mixtures would appear to have roughly the same emission level.
Control of NOx Emissions
Potential Approaches
emissions,
Before describing the methods selected for controlling NOx
it is worthwhile to discuss a1ternative methods which were
considered and discarded for a variety of reasons.
In general, low NOx
emissions can be achieved by reducing oxygen concentrations in the primary
zone, insuring that the combustion reactions are carried out at low tem-
perature, attaining very short residence times, or combinations of these
approaches. The only practical way to 1 imit oxygen concentrations would
be to operate with a fuel-rich primary zone. With this approach, the fuel/
air ratio would pass through the stoichiometric value at some point in
the combustor, and it is doubtful whether this transition could be accom-
pI ished quickly enough to avoid generating excessive amounts of NOx; in
addition, the use of a fuel-rich primary zone would create a problem with
respect to smoke emissions.
It is estimated that combustion temperatures
must be 1 imited to about 3400 deg F or lower if the NOx goals are to be met.
Possible methods of accompl ishing this are by burning only very weak mix-
tures, by abstracting heat from the combustion zone by convection, con-
duction, or radiation! or by admi~ing with a heat-ab.sgrbing inert fluid. COI1-
tinous combustion at mixture strength below the lean flammabil ity 1 imit can
only be achieved by passing the mixture through a catalyst matrix or by ,
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14
continuously admixing it with the high-temperature products from a pilot
flame. Such techniques are used in the control of combustible emissions
from industrial processes by the use of so-called "afterburners" (Ref 5).
The use of a catalyst matrix in a gas turbine combustion system is precluded
by volume and cost considerations. Control of combustion temperatures
by radiation is not feasible due to the large amount of heat that needs
to be removed. Heat removed by convection would presumably require the
use of a large amount of convective surface in the combustion zone. This
would rapidly become fouled by coke formation', if a fuel spray injection
system is used. Fuel pre-vaporization would be required and the con-
vective surface would need to be internally cooled by what is conven-
tionally dilution air. The resulting system would become overwhelmingly
complex. Heat removal by conduction could be achieved by the use of an
air-cooled porous plug burner, but this would need to be excessively
large.
Exhaust gas recirculation is not a feasible system for automotive
gas turbines as the exhaust gases would have to be cooled and recompressed
if flame temperatures are to be kept sufficiently low.
Water i nj ect ion
into the flame zone would be a feasible system, but since the water flow
rate required would be of the order of the fuel flow rate, this would
correspond to a significant penalty on the vehicle. Appropriately large
reductions in effective residence time do not appear to be feasible due
to the time required to evaporate and mix the fuel and allow completion
of the hydrocarbon reactions. A multiple swirl-can combustor concept
(Ref 6) was considered by NREC, but was el iminated on the grounds that
low NOx emissions could only be achieved by programming the fuel to
individual swirl cans which would operate with an equivalence ratio of
near 0.7. Such programming would require continual ignition and
extinction of the individual cans leading to excessive hydrocarbon
emissions. A particularly promising concept considered by NREC consisted
of employing a pre-vaporization chamber which evaporates and intimately
mixes most of the design fuel flow and injects the resulting very lean
mixture at high velocity into the exhaust of a pilot burner (Ref 7). It
was felt that this concept stood the best chance of success in ultimately
achieving the emission goals. However, since this approach would have
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15
represented a radical departure from conventional combustor designs, it
was felt that the amount of development time and effort required for its
successful appl ication would be beyond the scope of the program.
Selected Approach
The method adopted for achieving low emissions was selected on
the basis of the considerations discussed above and the evidence obtained
by NREC in previous programs.
In general terms, the selected approach
consisted of designing each of the two combustors to operate with a lean,
well-mixed primary zone over the ful I range of operating conditions.
The problem with designing a standard combustor for lean primary-
zone operation is illustrated schematically in Figure 2 which shows a typi-
cal plot of blow-out limits including contours of constant combustion effi-
ciency versus primary-zone equivalence ratio and combustor loading parame-
ter (/,I~). With fixed combustor geometry, the air flow split is essen-
tially independent of the operating conditions and so the primary-zone air/
fuel ratio is proportional to the over-all air/fuel ratio. This latter may
increase by as much as a factor of four from design point to idle con-
ditions. The slope of the operating 1 ine for a standard fixed-geometry
combustor is then fixed by the cycle conditions. For this reason, a
standard combustor is usually designed to have an approximately stoichio-
metric primary-zone fuel/air ratio ( 'p= I )at the full-power condition
in order to achieve an acceptable stabil ity margin. A higher design-
point value of ~p is usually precluded by the necessity of avoiding
smoke at high power. Under these conditions, the idle point often falls
fairly close to the lean blow-out I imit in a region of low combustion
efficiency. Typically, NOx emissions are high at the design point (full
power) and low at idle, while hydrocarbon and carbon monoxide emissions
are low at full power and high at idle. If a standard combustor were
designed to operate lean at the ful I-power point, the operating range
would be unacceptably narrow, since most of the operating points would
fall below the lean blow-out I imit. In addition, the low-power points
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16
would be in the region C>f low combustr6nefficiency resulting in excessive
HC and CO emissions. In order to achieve efficient lean primary-zone
operation at all conditions, it is necessary to resort to variable
geometry to control the distribution of air flow in the co~bustor. The
use of variable geometry provides an additional degree of freedom allow-
ing the slope of the combustor operating 1 ine to be made independent of
the cycle conditions as indicated in Figure 2. With this approach, the
operating conditions of the combustor can be controlled so as to minimize
over-all emissions while maintaining an acceptable operating range.
The uniformity of the fuel/air mixture in the primary zone
depends mainly on the aerodynamic design of the combustor and the manner
in which the fuel is introduced. From the standpoint of aerodynamic
design, the degree of mixing (hence, the uniformity of the primary zone)
improves wit~ increasing values of the pressure-loss factor defined as
the ratio of the combustor pressure loss (~P) to the dynamic head based
on the reference flow area of the combustor ( ~tVf)' For a given set of
inlet conditions and flow rate,
AP
-
1ref
.,
0( AP . I:>~f
,
where Dt-ef is the reference diameter. Increasing the combustor
pressure loss improves mixing by increasing the energy of the air jets
entering the combustor 1 iner which serve the function of "stirring'l the
main flow. Increasing the reference diameter has the effect of reducing
the through-flow velocity in the combustor; within reasonable 1 imits, this
improves mixing by allowing the entering air jets to penetrate more easily
into the main flow stream. The combustor pressure loss has a significant
effe~t on over-all cycle efficiency. Therefore, attaining significant
improvements in mixing by increasing the design value of combustor pressure
as
loss woul d
4-
D f
re
be achieved most
not appear to be a practical solution. Since l1~fh!f varies
, it was felt that an acceptable mixing performance could
effectively by a moderate increase in the combustor
diameter. The approach adopted for obtaining good mixing then was to
design for a value of pressure loss typical of automotive gas turbine
appl ications and somewhat oversize the diameter to achieve a relatively
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17
high value of
diameter is
6.p/~ret .
to increase the primary-zone residence time.
A consequence of increasing the combustor
This would tend
to increase NOx emissions and reduce HC and CO emissions.
However, as
mentioned previously, achieving a lean, well-mixed primary zone has a
significantly greater effect in reducing NOx emissions than residence
time.
Therefore, a moderate increase in residence time was considered
acceptable for the sake of obtaining good mixing, particularly since it
would aid in reducing HC and CO emissions.
With regard to fuel injection, the ideal situation would be to
pre-vaporize the fuel and pre-mix it with air prior to entering the com-
bustor. The actual approach adopted consisted of using an airblast type
of fuel nozzle which was expected to aid in achieving a reasonably uniform
fuel/air mixture in the primary zone of the combustor.
The airblast fuel
nozzle differs from conventional air-assisted nozzles primari ly in that
it operates with the avai lable pressure drop across the combustor liner
and does not require an external source of high-pressure air. The princi-
ple of operation of the airblast nozzle is indicated by the sketch shown
in Figure 3 which illustrates the general design features of this type of
nozzle. The airblast nozzle is usually designed to operate in conjunction
with the main combustor swirler. The main fuel is introduced downstream of
the nozzle swirler forming a film along the inside wall of the nozzle.
The angles of the main combustor swirler and the nozzle swirler are
chosen such that the air streams through these components are counter-
rotating as they enter the combustor. The fuel film enters the combustor
in the resulting high-shear region between the two swirler flow streams.
Break-up of the fuel film into droplets occurs just downstream of the
nozzle exit with the atomization energy being supplied by the dynamic
pressure of ' the two swirler streams. The mean droplet size obtained
with,this type of atomization is characteristically very small, on the
order of one-half of the values typical of a conventional fuel-pressure
atomizer.
Consequently, the airblast nozzle has relatively narrow
stability limits.
The stabil ity performance can be improved by the use
of a conventional single-orifice pilot atomizer as shown in Figure 3.
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18
Effects on Emissions of Other Species
Although the design approach util ized was dictated by the require-
ments for reducing NOx emissions, it was necessary to insure that in so
doing the emissions of the other pollutant species were not increased
beyond acceptable 1 imits. The use of a lean primary zone was expected to
el iminate smoke formation provided that care was taken to avoid local
fuel-rich regions. Burning lean mixtures would tend to increase the
emissions of CO and HC by virtue of the reduced flame temperatures.
However,
it was expected that the increased residence time resulting from the use
of an oversized combustor diameter would be sufficient to counteract the
effect of reduced temperature. In general, it was felt that the selected
approach was capable of achieving acceptable emission levels of all
pollutant species of concern.
J
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19
DESIGN OF COMBUSTORS
The methods uti1 ized in designing the two combustors are described
in this section. In general, these methods are fairly standard and are
based On information documented in a two-volume handbook (Refs 8 and 9)
on the technology of combustor design. This handbook was produced by NREC
and is widely used in the gas turbine industry by those organizations who
have sponsored its compi lation. The selection of the design conditions
is discussed first. This is followed by a description of the aerothermo-
dynamic and mechanical design of the two combustors. Although the elements
of the design process are discussed separately below, the actual design
process involved an iterative approach to determine the relative trade-
offs and arrive at the necessary compromises among the various performance
requirements. .
Cycle Conditions
As mentioned previously, the combustors were designed so as to
be representative of two different automotive gas turbine cycles-- a 10w-
pressure-ratio, regenerative cycle (designated as Class A) and a high-pressure
ratio, nonregenerative cycle (Class B). These two cycles are shown
schematically in Figure 4. The cycle operating conditions relevant to
the design of the combustors were selected on the basis of an engine
power rating of 150 hp for both cycles. The estimated nominal values
of these conditions are given in Table I I.
The main purpose of defining the cycle performance was to
provide a nominal set of operating conditions on which to base the design
and subsequent testing of the combustors.
In so doing, the primary
requirement was to insure that the combustor designs and measured per-
formance were representative of the two types of gas turbine cycles con-
sidered. The combustors were not intended for use in any specific engine,
but instead were to be capable of beIng tested over wide ranges of op-
erating conditions. In addition, the design approaches to be uti I ized
represented moderate but significant advances in combustion technology
which were as yet untried in terms of their measured effects upon perform-
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20
ance.
Therefore, the use of sophisticated analysis procedures to determine
the cycle operating conditions to any great degree of accuracy was not
warranted.
The values of the combustor inlet temperature and pressure and
exit temperature at the design point (full-power operation) were selected
in accordance with the criteria specified in the contract. The design-
point values of the other operating conditions were estimated on the basis
of approximate cycle calculations using assumed typical values of com-
ponent efficiencies which might be achievable for the given pressure
ratios. These calculations were simpl ified by ignoring entrance, exit,
duct, and mechanical losses. Although this approximation results in
optimistic values of fuel flow rate, it had I ittle effect on the sizing
of the combustors, since specific power (hence air flow rate) is relatively
insensitive to these losses (Ref 10). For both cycles, a 3 per cent
pressure drop and 100 per cent combustion efficiency were assumed for the
combustor. The calculations for the regenerative cycle assumed a com-
pressor and turbine isentropic efficiency of 85 per cent, a regenerator
effectiveness of 89 per cent, and regenerator pressure losses of I per cent
on the cold side and 4 per cent on the hot side; for the nonregenerative
cycle, the compressor and turbine isentropic efficiency was assumed to
be 80 per cent. The off-design cycle conditions given in Table I I were
estimated by approximately scal ing data available in the 1 iterature (Refs 11
through 17) for existing gas turbine engines of the regenerative and non-
regenerative type and data obtained in previous programs by NREC. This
approach consisted of normal izing the available data on off-design con-
ditions with respect to the values at design point and assuming that the
operating conditions for the two cycles of concern followed the same
general trends.
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21
Combustor Desiqn Conditions
General Confiquration
Both combustors were designed as single-can, throughflow con-
figurations, since this type is su.itab1e for most simple cycle and
regenerative engines and is simpler to fabricate and test than alternative
arrangements. The general configuration of both combustors is depicted
in Figure 5, and, as can be seen, is typical of conventional gas turbine
combustors.
The major components consist of a casing, I iner, dome, and
radial-inflow swir1er. Fuel is injected by means of an airblast nozzle.
The ignition source consists of a standard high-voltage gas turbine spark
plug. Essentially al I of the combustion occurs in the primary zone, a
highly turbulent region with a recirculating mean flow path and a low
mean axial velocity. The recirculating flow pattern is estab1 ished by
the swirler air and reinforced by the secondary jets. The intermediate
zone provides a region of relatively high temperature for the completion
of the combustion reactions and the recombination of any dissociated
products of combustion. The bulk of the remaining air enters the liner
through the dilution holes and mixes with the combustion gases as the
flow passes through the dilution zone thus lowering the temperature to
the required turbine inlet value and achieving the desired exit tem-
perature profile. Cool ing of the flametube 1 iner and dome is accompl ished
by four film-cool ing slots, one for the dome and one for each of the
three major zones of the combustor; additional cool ing of the downstream
portion of the 1 iner is accomp1 ished by allowing some flow to bleed
through keyhole-shaped holes in the piece joining the I iner to the casing
at the exit of the combustor.
Most of the air participating in the combustion process occurring
in the primary zone is suppl ied by airflow through the fuel nozzle and swirler
( W1~w and M~w ) and part of the air entering through the secondary holes
.
( ~~~p ). The combustors are variable-geometry configurations by virtue
of the fact that the airflow through the swir1er and secondary holes
(hence, the primary-zone equivalence ratio) is controlled by adjusting
the flow areas of these components. For the secondary holes, this area
adjustment is accomp1 ished by means of a movable sleeve fitting around
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22
the 1 i ne r.
The flow area of the radial-inflow swirler is adjusted by
an annular cup which fits over the swirler and fuel nozzle.
These
variable-geometry devices are described in more detail in the subsequent
discussion of the mechanical design of the combustors given in this
section of the report.
. .
Selected Values of Design Parameters
The values of the pertinent design conditions selected for the
combustors are given in Table I I I, and the design distributions of air
flow are given in Table IV.
The inlet flow conditions, temperature rise,
and heating rate follow directly from the cycle design-point conditions.
The values of the other design parameters were selected on the basis of
the considerations discussed below.
The exit temperature traverse qual ity is defined as the difference
between the maximum and mean values of the exit gas temperature profile
divided by the temperature rise in the combustor. The selected value for
both combustors is typical of the design goal for standard gas turbine
combustors. The maximum allowable wall temperature was selected to pro-
vide acceptable durabil ity with reasonable construction materials. As
discussed in the previous section, it did not appear justified to design
for a large pressure loss in order to achieve good mixing; instead, the
selected approach consisted of moderately oversizing the combustor diameter.
Therefore, the selected pressure loss is also a value typical of automotive
gas turbine combustors.
The pressure-loss factor (AP!,.re/) is usually on the order of
thirty for standard combustors. The approach adopted for obtaining good
mixing consisted of choosing a larger than standard design value of the
pressure-loss factor. Ideally, this choice should involve a trade-off
between the opposing effects of mixing and residence time on NOx emissions.
The effect of residence time was examined with the aid of an approximate
NOx emission model previously developed by NREC (Ref \8) which assumes
perfect mixing. However, no information was available on the quantitative
effect of ,1pA .,on the degree of mixedness. The final design value
for both combu!Idrrs then was chosen somewhat arbitrarily to be about three
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23
times larger than the standard value. This design value was felt to be high
enough to achieve acceptable mixing without increasing the residence time
excessively. The ~ressure-loss factor also affects combustion efficiency
(hence, CO and HC emissions) in that it fixes the size (diameter) of the
combu<; tor.
Within the accuracy of the available correlations of combustion
efficiency (Refs 8 and 9), the size of each combustor dictated by the
se I ected des i gn va I ue of j).P>/'f('t.{- was cons i dered suff i c i ent to ach i eve
the combustion efficiency goals.
The principal consideration in choosing the primary-zone
equivalence ratio was the requirement of minimizing NOx emissions. From
this standpoint, it was desirable to select as Iowa value of ~ as
possible. In order to obtain acceptable ignition performance and flame
stabil ity, ~f should not be lower than about 0.5. This is the value
that was chosen for Combustor A. With the lower air/fuel ratio of Com-
bustor 8, less air was available for dilution and cool ing. Therefore, a
higher value of ~ was required in order to achieve adequate dilution
and cool ing performance.
The values of air flow through the nozzle, swirler, and secondary
holes I isted in Table IV were chosen to provide the required amount of
primary-zone air flow for the selected values of ~. This was done assum-
ing that the primary-zone air flow participating in the combustion process
(MpJefI) consisted of the total air entering through the nozzle, swirler,
and dome film-cool ing slot and 50 per cent of the air entering through
the secondary holes and primary-zone film-cool ing slot. The proportion
of the air entering the primary zone through the swirler was selected in
accordance with conventional design practice (Refs 8 and 9) to be on the
order of 30 per cent of the primary-zone combustion air. The remainder
of the air not required by the primary zone was divided so as to achieve
an acceptable compromise between dilution and cool ing performance.
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24
Fuel Nozzle Desiqn Specifications
As mentioned previously, one aspect of the selected approach
to obtaining good mixing consisted of using a piloted airblast type of
fuel nozzle. The major design parameters for the airblast nozzle are
the nozzle air/fuel ratio, spray cone angle, flow number, and spray
characteristics (mean droplet diameter, droplet size distribution, and
spray distribution). Since this type of nozzle is still under develop-
ment, it was not possible to specify the required characteristics exactly.
Instead, six different nozzles (two for Combustor A and four for Combus-
tor B) were obtained from the Parker-Hannifin Corporation and investigated
experimentally in the testing phase of the program.
From the standpoint
of controlling emissions, the principal nozzle variables were expected
to be the spray characteristics, the amount of air flow surrounding the
fuel (nozzle air/fuel ratio), and the weak extinction performance. With
the airblast nozzle, the general spray characteristics (particularly
mean droplet diameter, SMD) are principally dependent on the available
dynamic head of the air which is proportional to the combustor pressure
loss. In addition, the effect of spray characteristics on emissions is
known only in a qualitative sense. Therefore, it was felt that specify-
ing nozzle designs with significant variations in spray characteristics
was not warranted. The desired spray characteristics of all the nozzles
were then specified in terms of achieving a well-developed fuel spray
at all operating conditions with a mean droplet diameter (SMD) of less
than sixty microns; the droplet sizes achieved from the nozzles for the
two combustors were estimated to be on the order of 45-68 microns for
Combustor A and 12-42 microns for Combustor B assuming negligible wet-
ting of the combustor dome.
The six nozzles specified then consisted
of pi loted and unpiloted configurations having different design values
of nozzle air/fuel ratio.
The desired specifications for the nozzles are given in Table V.
The values of air/fuel ratio were chosen to be 2-4 times higher than con-
ventional airblast nozzles in order to aid in achieving a low mean equiva-
lence ratio; it was felt that still higher values would aggravate the sta-
bility problems inherent in this type of nozzle. The spray cone angles were
selected essentially on the basis of conventional design practice. A wide
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25
main spray angle would be beneficial from the standpoint of allowing suffi-
cient time for the fuel and air to mix before combustion. However, too
high an angle can result in an excessive amount of fuel impinging on the
internal surfaces of the combustor and increasing the emissions of unburned
hydrocarbons. A 90 degree angle is generally considered to represent a
reasonable compromise. A relatively narrow pilot spray cone angle is
desirable to provide a small local fuel-rich region for the purpose of
improving flame stabil ity. The flow number of the pressure atomizing
pilot was selected to be as small as practicable in order to achieve acceptable
atomization at low fuel flow rates. The flow number of the main airblast
portion of the nozzle was unspecified, since this factor has virtually
no effect on atomization qual ity.
Aerothermodvnamic Desiqn
Final ConfiQurations
The final configurations and dimensions for Combustors A and
B resulting from the design
schematically in Figure 6.
used in both combustors are
specifications discussed above are shown
The dimensions of the radial-inflow swirler
given in Figure 7.
In each combustor, the
dome is cooled by a combination of impingement and film cooling. The
dome film-cool ing slot is fed by a number of circular metering holes
spaced so as to provide uniform impingement cool ing. The liner film-
cool ing slots are also fed by circular metering holes spaced uniformly
around the circumference of the I iner. Additional cool ing of the down-
stream end of the I iner is provided by allowing air to flow through a
number of keyhole-shaped bleed holes located in the annulus at the com-
bus tor ex it.
The numbers and dimensions of these holes are given in
Table VI.
As mentioned previously, six airblast nozzles were
suppl ied by Parker-Hannifin Corporation. All of the nozzles
to have the same external space envelope so that they could
designed and
were designed
be tested in
either of the combustors.
The general nozzle configuration and external
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26
dimensions are presented in Figure 8. The nozzle length was made larger
than would be conventional in order to accommodate the required travel
distance of the device used to control the flow through the radial-
inflow swirler.
Sizinq
The casing (reference) diameter for each combustor was calculated
from the selected design values of pressure loss and pressure-loss factor
using the definition of APh~ . The flametube liner diameter was
selected to provide a reasona~~ amount of convective cool ing of the 1 iner
by the annulus airflow without seriously compromising jet penetration.
The total combustor length is the sum of the lengths of the primary, inter-
mediate, and dilution zones. A primary-zone length equal to one-half the
I iner diameter. was selected to provide a recirculating flow pattern in
the primary zone corresponding to a toroid of zero inner diameter. The
major function of the intermediate zone is to allow sufficient time for
the reaction of carbon monoxide to reach completion before quenching
with dilution air.
In accordance with general design practice, an
intermediate-zone length of approximately one-half the 1 iner diameter
was selected as being sufficient for this purpose. The length of the
dilution zone was chosen to provide the selected design value of exit
temperature traverse qual ity using standard correlations of traverse
qual ity versus pressure-loss factor and length given in References 8
and 9.
The various openings in the combustor were sized to provide the
selected air-flow distributions and pressure drop. In performing these
calcu1ations, the standard equation for flow through a row of holes was
used along with discharge coefficients obtained from available correlations
and data for different hole types and flow configurations (Refs 8, 9,
and 19). The secondary holes were designed as plunged slots to provide
good penetration and to simpl ify the means of varying their flow area.
Both the swirler and secondary holes were oversized in order to allow
sufficient flexibil ity in obtaining variations in primary-zone flow rate
during testing. The dilution holes were designed using the approach
described in Reference 20 to provide as close to optimum penetration of
the dilution jets as possible with the available dilution air.
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27
Thermal Analysis
A thermal analysis involving calculations of the temperature
distributions of the combustor surfaces was performed for the final con-
. figuration and air-flow distribution of each combustor. Standard correl-
ations (Refs 8, 9, and 19) were used in determining the values of heat-
transfer coefficients, flame radiation properties, and film-cool ing ef-
fectiveness.
The calculated axial distributions of 1 iner temperature for
both combustors are plotted in Figure 9 for both a nonluminous and a
luminous flame. With the airblast nozzle, it was expected that a relatively
nonluminous flame would be obtained. As can be seen, the estimated maxi-
mum temperatures were lower than the selected maximum allowable value
(1700 deg F). It was decided not to reduce the amount of cool ing any
further and to remain with a somewhat conservative cool ing approach.
The
results described here were obtained for the design point which corresponds
to a relatively lean primary zone. During testing of the two combustors,
it was planned to examine primary-zone equivalence ratios higher than the
design values which would result in higher flame temperatures. Therefore,
being somewhat conservative in terms of cool ing at the design point allowed
greater latitude in the conditions which could be examined safely during
testing.
Mechanical Desiqn
The major task in the mechanical design of the combustors con-
sisted of selecting the method to be used in control 1 ing the flow areas
of the swirler and secondary holes.
The variable-geometry configuration
used for both combustors is illustrated in the sketch of part of the primary-
zone region given in Figure 10. The device for control 1 ing the flow through
the swirler (swirler flow throttle) consists of an annular cup which fits
over the swirler and fuel nozzle as shown in Figure 10. This piece contains
blades which fit into the slots of the swirler and is supported and
adjusted by means of four rods which pass through a spider mounting
attached to the casing. A seal is provided to minimize leakage through
the clearance between the throttle and the nozzle. The combustor dome
is also supported by a spider attached to the casing.
The device for
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28
controlling the flow through the secondary holes (secondary flow throttle)
consists of a movable sleeve around the I iner. The diameter of the sleeve
is large enough to maintain a positive clearance between the sleeve and the
I ine~. The sleeve is supported on the I iner by four spring clips; the
axial position of the sleeve is maintained by four adjustable straps
attached by lockscrews to the upstream end of the I iner. In the design
of the variable-geometry elements, it was not intended to achieve a
mechanized, operational system for use in the program. However, the
specific devices utilized for control I ing the swirler and secondary flow
streams were selected so as to represent a real ist.ic approach which ultimately
could be mechanized in a fairly straightforward manner.
As mentioned previously, the swirler throttle and combustor dome
are supported by spiders attached to the casing. The downstream end of the
I iner is supported by the conical-shaped piece containing the bleed holes
which is attached to the casing by screws. A seal ing ring is attached
to the upstream end of the 1 iner. In assembl in9 the combustor, this
ring fits over and rests on the dome. This mounting arrangement allows
for relative axial growth of the I iner and dome, since they are not
rigidly attached to each other. The I iner, upstream seal ing ring, dome,
and secondary flow throttle are fabricated of Hastelloy. The remaining
components are fabricated of 310 stainless steel.
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29
COLD-FLOW TESTS
In addition to detai led combustion experiments, four different
series of tests were conducted under nonburning conditions. These were
primari ly of a diagnostic nature and provided information which aided in
determining what modifications to the combustor configurations were re-
qui red and interpreting the results obtained in the subsequent combustion
tests. The specific purpose of these cold-flow tests was to measure the
aerodynamic performance of both combustors and examine the spray perfor-
mance of the airblast nozzles.
The four types of tests conducted were:
1.
2.
Flow visualization tests with water as the flow medium.
Pressure loss and flow distribution tests with nominally
ambient air as the f10w medium.
3.. Qualitative spray performance tests with air supplying the
The tes ts
atomization energy and water as the nozzle test fluid.
4. Spray analysis tests providing quantitative information on
droplet size and spray distribution.
conducted and results obtained in each of the first three series
are discussed in this section, and the experimental rig and instrumenta-
tion uti lized are described in Appendix I.
described in Appendix I I I.
The spray analysis tests are
Water-Visualization Tests
The objective of these tests was to determine the jet penetra-
tion and mixing in the combustion and di lution zones by observing the flow
patterns in each of the two combustors for different flow rates and vari-
able geometry settings (~""and L~y as shown in Fig 10). A11 of these
tests were conducted with full-scale transparent models of the two combus-
tors which were as close in detail as possible to the actual combustors.
The flow conditions were chosen so as to simulate Reynolds number approxi-
mately. The'effects of variable-geometry settings were investigated sys-
tematically by observing the flow patterns obtained for variations in the
secondary-h01e setting (1st) at each of a number of different swirler set-
tings (J?sw)' In each test, electrically generated hydrogen bubbles were
used as the f10w tracers. The flow patterns and jet penetration were
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30
observed by illuminating flow planes in the combustor containing the axis
and the center lines of diametrically opposite pairs of secondary holes
and di lution holes. Observations were also made by illuminating planes
normal to the combustor axis at different axial positions along the length
of the combustor.
The results of the water tests were essentially qualitative in
nature and consisted of observations regarding the flow patterns and degree
of mixing achieved in the various regions (particularly the primary zone)
of the combustor. The initial tests indicated that a modification of the
swirler assembly was required in order to achieve a strong recirculatory
flow pattern in the primary zone. The final swirler configuration described
previously is the result of the modifications made on the basis of the
water tests. In addition, the early tests indicated that the clearance
between the Jiner and the sleeve used to control the secondary-hole flow
was too large. This resulted in excessive leakage and reduced the ef-
fectiveness of the control, a fact confirmed by the cold-air tests. In
all subsequent tests, this leakage was reduced to an acceptable value by
inserting 0.015 inch thick shim stock between the sleeve and the liner.
The general flow pattern observed in the flow-visual ization tests
is shown in Figure 11. As can be seen, this corresponds to the classic
flow pattern for a well-designed gas turbine combustor. In general, the
results indicated that vigorous mixing in the primary zone and good pene-
tration of the dilution jets was achieved for the final configurations of
both combustors. This appeared to be true for all variable-geometry settings
except those in which the secondary sleeve was nearly closed; that is, when
the secondary sleeve was in a position such that the shape of the secondary
holes was virtually circular. For these closed settings, the secondary
jets were diverted more strongly by the upstream flow. Therefore, the jets
entered the liner at a shallower angle and did not penetrate to the com-
bustor center line. As a result, the amount of flow recirculating back
into the primary zone was reduced along with the degree of mixing achieved
in this region. For a given variable-geometry setting, the flow rate
(hence, pressure drop) seemed to have no discernible effect on the general
flow patterns observed. However, as would be expected, increasing the flow
rate increased the apparent strength of the mixing by virtue of the higher
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31
velocity levels in the combustor. The.general conclusions reached on the
basis of the flow-visualization tests were that the degree of mixing and
general flow patterns achieved in both combustor configurations appeared
to be satisfactory for virtually all variable-geometry settings.
Air Flow Distribution Tests
The principa1 objective of these tests was to obtain experimental
information which could be used to determine the distribution of air flow
in each of the two combustors for any given flow condition and variable-
geometry setting. Basically, this required measuring the variation of ef-
fective flow area (defined in general here as the product of discharge
coefficient and actual flow area) for each set of openings into the com-
bustor liners.
Determining the effective flow areas involved measuring the
'.
flow rate through and pressure drop across each set of openings. The ap-
proach selected for accomplishing this consisted of testing each set of
openings independently. All of these tests were performed with the actual
combustors. In each test, all of the openings were blocked off except the
set being tested. The air flow rate into the combustor was then varied
over a predetermined range and the combustor pressure loss measured at a
number of different values of flow rate. This approach is somewhat inac-
curate, since the discharge coefficient (hence, effective flow area) de-
pends to some extent on the conditions into which the flow through the
holes is discharging. However, information given in References 8 and 9
indicates that the inaccuracy due to this effect is at most on the order
of ten per cent. The magnitude of this effect was estimated to be negli-
gible by conducting some tests with various combinations of openings. An
additional approximation involved in this approach is that the static pres-
sure in the liner is constant and equal to the exit value.
to assuming that the pressure changes due to combustion and
losses in the liner flow are negligible in comparison to the
across the openings in the liner. Estimates of the relative
This corresponds
f r i c t i ona 1
pressure drop
magnitudes of
these losses showed that the accuracy of this assumption was acceptable for
both combustors.
The air flow and pressure-drop data obtained in these tests were
used to compute the values of effective flow area 5AA,1V) for each set of
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32
.openings. In general, the results showed that the effective area did not
vary significantly with flow rate and an average value for each set of
openings was sufficiently accurate for calculation purposes. The average
values of effective flow area are listed in Table VI I.
These values were
used to calculate the anticipated distributions of air flow in both com-
bustor configurations as functions of the variable-geometry settings of
the swirler (~w) and secondary holes (.isy). The results of these
calculations showed that the values of flow rate obtained for each set of
openings were reasonably close to the selected design values.
As mentioned previously, it was assumed in the design of the two
combustors that the portion of the primary-zone flow which participates in
the combustion process ( ~p,~) consists of the air flow entering through
the nozzle, swirler, and dome cooling-film slot and 50 per cent of the flow
entering through the secondary holes and the primary-zone (film-cooling)
slot. The results of the water flow-visualization tests and preliminary
combustion tests indicated that a more reasonable estimate of the effective
primary-zone flow would be
WlpJe{I = rY>rN + t¥1,sw 'f-o.4 M~y
The values of ~PJ~ were calculated on this basis and are plotted versus
variable-geometry setting in Figures. 12 and 13 for the two combustors. As
can be seen, the variable-geometry approach utilized provides a variation
in effective primary-zone flow (hence, ~~) of a factor of about 3.3 for
Combustor A and 2. I for Combustor B. Examination of the estimated cycle
conditions given in Table I I shows that the values of over-all air/fuel
ratio vary by factors of approximately 2.7 for Combustor A and 2.0 for
Combustor B. Therefore, in order to ma'intain a constant primary-zone
equivalence ratio, the variable-geometry shoufd provide corresponding
variations in the effective primary-zone flow of about the same order.
The selected variable-geometry approach appears to be capable of providing
adequate control of the primary-zone equivalence ratio.
Nozzle Spray Visual ization Tests
The objective of these tests was to examine qualitatively the gen-
eral spray performance of the airblast nozzle configuration. The nozzle and
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33
radial-inflow swirler assembly were mounted in a test fixture connected
to an air supply as described in Appendix I. Initial tests were conducted
for two different nozzles. However, no difference in performance was ob-
served. Consequently the bulk of the tests were performed for one nozzle
(A2.1). Each test consisted of varying the air and water flow rate for a
given configuration. A high-intensity light source provided the neces-
sary illumination for observation of the spray; photographic records of
the spray patterns obtained were made for a number of selected tests. The
effects on atomization quality of nozzle air pressure-drop and air/fuel
ratio, swirler setting, and axial position of the nozzle were examined in
this series of tests.
As for most of the cold-flow tests, the spray visualization
results obtained are primarily qualitative consisting of observations of
the spray cone angle, mean droplet size, and spray distribution. As would
be expected, the variable having the major effect on spray performance was
the air pressure drop. The effect of pressure drop is illustrated in Figure
14 which contains photographs of the spray obtained for three different
pressure drops. At low values of AP, the spray is not well-developed and
consists principally of individual streams of large droplets. As~P is
increased, the mean droplet size decreases rapidly and the spray becomes
more uniform. In all cases, the observed spray cone angle was approximately
equal to the design value of 90 degrees. The effect of nozzle air/fuel
ratio on atomization quality was similar to that of pressure drop. In-
creasing the nozzle air/fuel ratio decreased the mean droplet size and im-
proved the uniformity of the spray. Increasing the amount of air flow
through the radial-inflow swirler by opening the swirler setting (.~"' )
had a similar but less noticeable effect on the spray.
A number of tests were conducted to examine the effects of the
relative axial position of the nozzle. In the design position, the exit
of the nozzle coincides with the inlet of the swirler air to the primary
zone of the combustor as shown in Figure 6. The results of moving the
nozzle axially approximately 0.1 inch in eith~r the upstream or the
downstream direction are shown in Figure 15.
As can be seen, moving
the nozzle in a downstream direction does not appear to have any signifi-
cant effects on the spray. However, moving the nozzle in the upstream
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34
direction results in a marked reduction in. spray cone angle.
This indi-
cates that in order to achieve the desired. spray characteristics, care
must be taken to insure that the relative position of the nozzle does not
change significantly during operation of the combustor.
In all cases, including those at high values of ~I', the fuel
fi 1m leaving the nozzle lip persisted for a significant distance into the
combustor as indicated by the photographs in Figures 14 and 15. This re-
sults in a high fuel/air ratio and nonuniform distribution in the vicinity
of the nozzle exit. Appreciable burning can occur in this region result-
ing in significant increases in the amounts of NOx produced. This conclu-
sion is borne out by the results of the detai led combustion tests dis-
cussed in the next section of this report.
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35
COMBUSTION TESTS
This section of the report describes the detailed combustion
tests performed with the final configurations of both combustors. The
general approach used in conducting the experimental program is discussed
first. This is followed by a presentation of the experimental results
obtained from each combustor and observations regarding performance made
on the basis of these results; the results for Combustor B are discussed
first, since this was chronologically the first of the two combustors
tested. Next, a critical analysis of the results is presented, and a
series of tests conducted to confirm the conclusions reached on the basis
of this analysis is discussed. Finally, the recommended approaches for
achieving IOW'emissions developed on the basis of the results of the experi-
mental program are'presented. The experimental rigs and instrumentation
uti 1 ized in conducting the combustion tests and the relations used in
reducing the data are described in Appendices I and I I.
Over-All Approach
The major objectives of the experimental program were to obtain
detailed experimental data which could be used in determining the effects
on combustor performance (particularly emissions) of the principal design
and operating variables, and to demonstrate the potential effectiveness of
the selected design approach in ultimately achieving the Federal 1975/76
emission goals.
This involved testing variations of the final con-
figurations of both combustors over wide ranges of flow conditions repre-
sentative of the anticipated operating conditions of the two gas turbine
cycles on the basis of which the combustors were designed. As mentioned
previously, the major factors with regard to NOx emissions are the com-
bustor inlet temperature, primary-zone residence time, mean primary-
zone equivalence ratio, and degree of mixing. The principal variables
with regard to these parameters are the combustor size (diameter and
length), ai r flow inlet conditions ( n1~, ~3' and ~3)' fuel flow
rate, variable-geometry setting (~sw and ~~y ), and the fuel nozzle.
The combustor diameter and length have a major effect on residence time.
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36
However, in the program described in this report, variations in diameter
or length were not investigated for either of the two combustors. The
combustor air flow rate primarily affects residence time and liner pres-
sure drop. The inlet pressure and temperature affect not only residence
time and pressure drop, but also the kinetics and chemical equi librium of
the combustion reactions occurring in the combustor. The major effect of
fuel flow rate is to govern the mean primary-zone equivalence ratio for a
given configuration and set of inlet conditions.
The variable-geometry
setting affects the degree of mixing by altering the pressure-loss charac-
teristics of the combustor and the mean primary-zone equivalence ratio and
residence time by controlling the amount of air flow into the primary zone.
The characteristics of the fuel nozzle uti lized affect primari ly the de-
gree of mixing achieved in the primary zone by virtue of their effects on
the preparation of the fuel/air mixture entering the combustor.
On the basis of the considerations discussed above, the general
approach selected for conducting the combustion tests consisted of meas-
uring performance for independent variations in each of the inlet flow
. - ,::)
conditions (~, 103, and 1;;;1)' the primary-zone equivalence ratio, and
the combustor configuration (variable-geometry setting and fuel nozzle).
The general procedure employed was as follows. With the combustor inlet
conditions, the variable-geometry setting, and fuel nozzle fixed-, the
combustor performance was measured at a number of different fuel flow
rates starting from the minimum value capable of sustaining combustion.
This was repeated at a number of different sets of inlet conditions
covering the desired testing range for a number of different variable-
geometry settings and fuel nozzles. Each test consisted of taking com-
plete performance measurements of a given combustor geometry and fuel
nozzle for single values of fuel flow rate, air flow rate, and combustor
inlet temperature and pressure.
The variables measured in each test in-
cluded air and fuel inlet conditions and flow rate, combustor pressure
drop, exhaust gas temperature distribution, and exhaust gas concentrations
of C02, CO, HC, NO, and NOx. Detailed measurements of the exhaust gas
temperature distributions were made only at the highest value of fuel
flow rate tested for each run (defined as a single set of inlet
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37
conditions); in all other cases, a four-point measurement was made. Smoke
emissions were measured for a selected number of tests and found to be
negl igible as expected with the selected design approach. Therefore, fur-
ther detailed smoke measurements did not seem to be warranted. The 1 iner
surface temperature was measured using thermal paints; the 1 iner was
examined at the conclusion of each series of runs for a given combination
of variable-geometry setting and fuel nozzle. The test results obtained
are discussed separately below for each of the two combustors.
Discussion of Test Results for Combustor B
Description of Tests
A total of thirty-six runs consisting of approximately 175 de-
tailed tests were conducted with Combustor B.
.
These tests covered the
following nominal ranges of flow conditions:
Pressure level
Inlet temperature
53 - 88 psia
510 - 900 degF '
0.30 - 0.84 Ibm per see
56 - 212
Air flow rate
Over-all air/fuel ratio
Additional tests at higher pressures were planned originally, but were
eliminated per direction of EPA. The tests were performed for two dif-
ferent variable-geometry settings ("closed", corresponding to what would
be approximately an idle setting, and IIfull open", corresponding to a 100
per cent power setting) and two fuel nozzles (81.1 and 82.1 differing in
nozzle air/fuel ratio). The approach adopted in selecting the combinations
of flow conditions was to tp.st at a number of different constant values
of the standard combustion efficiency parameter (e). The nominal test
conditions examined in each run are listed in Table VI I I; the results ob-
tained in each test are given in Tables IX-XIII.
Emission Performance
The pertinent results are summarized in Figures 16 and 17 which
show plots of emissions (NOx, CO, and HC) and combustion efficiency v,ersus
over-all air/fuel ratio.
As can be seen, the NOx emissions are higher than
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38
the goal in all cases, ranging from a maximum emission index of about 12 mg
per gm fuel to a minimum of about 3 mg per gm fuel.
At the same time, the
carbon monoxide and hydrocarbon emissions are relatively low, most of the
data fall ing below the goals. The combustion efficiency is correspondingly
high-- very close to 100 per cent for most conditions. The data presented
in the figures illustrates the effect of variable-geometry setting on
emissions. As the swirler and secondary holes are opened allowing more
air into the primary zone, NOx emissions decrease somewhat and CO and He
emissions increase.
This effect is most noticeable with regard to CO,
as seen in Figure 16.
The general trends of the data are as would be expected, NOx
emissions increasing as the residence time and inlet temperature and
pressure are increased and decreasing as the combustor pressure drop and
over-all ai~/fuel ratio are increased; basically, variations in these
quantities have an opposite effect on CO and HC emissions.
The major
variations in emissions of CO and HC are observed near the weak extinction
1 imit where the emissions of these species rise sharply with increasing
air/fuel ratio.
The general effect of residence time is shown in Figure 18.
As can be seen, varying the residence time while maintaining the pressure
drop constant has a somewhat less than 1 inear effect .on NOx emissions, but
a strong effect on CO emissions. Although part of the difference in.eO
levels shown in Figure 18 can be attributable to the differences in inlet
temperature, it would seem apparent that the major factor is residence
time.
The typical effects of variations in the other parameters on NOx
emissions are illustrated in Figure 19; the variations of CO emissions
with these parameters are difficult to determine from the data obtained
with Combustor B due to the observed, strong effect of residence time.
The combined effect of pressure drop and residence time on NOx emissions
at approximately constant inlet temperature and pressure can be seen by
comparing the results for Run 23 with the base curve (Run 30). As can be
seen, decreasing the air flow rate so as to decrease the pressure drop
and increase the residence time produces an increase in NOx emissions.
Although it is difficult to separate the effects of residence time and
pressure drop, it would appear from the data that these two factors.have
about the same order-of-magnitude effect on NOx emissions. The curve for
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39
the higher temperature (Run 26 on Fig 19) exhibits a higher NOx level than
the base curve, illustrating that NOx emissions increase with inlet tem-
perature.
The curve for the higher pressure (Run 27) also shows a higher
NOx level than the base curve.
Part of the observed increase in NOx emis-
sions for the higher pressure can be attributed to the fact that the val-
ues of inlet temperature and residence time were also somewhat higher than
for the base curve. However, taking into account the effects of inlet
temperature and residence time, it would appear that the net effect of in-
creasing inlet pressure is to increase NOx emissions.
The data obtained
for Combustor A discussed subsequently exhibit the effects of inlet tem-
perature and pressure more clearly.
An additional parameter investigated was the relative amount of
air flow surrounding the fuel as it is injected into the primary zone.
Increasing this quantity by increasing the relative amount of air flow
through the nozzle and/or swirler would be expected to reduce NOx emis-
sions by shielding the fuel sheet from the flame and reducing the amount
of fuel burned at high values of equivalence ratio. This parameter was
examined by testing two nozzles having different air/fuel ratios. The
effects of nozzle air/fuel ratio are illustrated in Figure 20 which con-
tains plots of NOx and CO emissions for the two nozzles at comparable flow
conditions. The results show that increasing the nozzle air flow produces
an increase in CO emissions. The effect on NOx is not, very noticeable;
however,
it would appear that a slight decrease in NOx emissions was ob-
tained. Since relatively small variations in the amount of nozzle air
flow were investigated, the observed magnitude of this effect is not very
I a r ge .
A series of tests was conducted to examine further the effects
of pressure drop on emissions.
For this purpose, Combustor B was modified
so as to increase the pressure drop for a given set of inlet conditions.
The modification consisted of blocking off one-third of the metering holes
for each of the film-cool ing slots in the primary and intermediate zones
and decreasing the diameter of the dilution holes to 0.25 inches. The
effects of this modification were to increase the pressure drop by a
factor of about two and increase the total primary-zone flow rate (decrease
the primary-zone residence time) as calculated from the cold flow data by
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40
a factor of about 1.3. The modified configuration was then tested at the
same conditions previously examined with the original configuration. The
results obtained with the modified configuration are given in Table XI I I;
the results obtained with the original configuration at the same con-
ditions are those 1 isted in Table XI.
The NOx and CO emissions obtained
with the original and modified configurations of Combustor B are presented
for comparison in Figure 21. As shown previously (Fig 18), residence time
has a somewhat less than 1 inear effect on NOx emissions. Therefore, the
results given in Figure 21 would seem to indicate that the significant
reduction in NOx emissions observed is primari Iy due to the effect of in-
creasing the pressure drop. The apparent strong effect of pressure drop
is not confirmed, however, by the data obtained in other tests. A possi-
ble explanation for these results lies in the effect of the modification
on the discMarge coefficient of the secondary holes. The'primary-zone
flow for the modified configuration was calculated assuming this discharge
coefficient remained constant.
In the modified configuration, the amount
of di lution flow was significantly reduced, thereby decreasing the annulus
air flow at the secondary holes and increasing the local value ofAP/i~.
In general, the discharge coefficient for a row of holes increases with
APi!' at the point of injecti.on. It would seem then that the actual
value of secondary flow and the relative proportion recirculating back
into the primary zone were higher than those calculated assuming a con-
stant discharge coefficient. Consequently, the data for the modified
configuration were obtained at significantly lower values of ~p than as-
sumed which would account for the discrepancy with regard to the effect
of pressure drop.
Other Performance Parameters
concern,
Although the emission performance of the combustor is of primary
the values of the other more conventional combustor performance
parameters must also be acceptable in terms of their effect on over-all
engine performance, This is necessary in order to insure that the emis-
sion goals are met with a practical combustor configuration which could
be utilized directly in an automotive gas-turbine engine. In this regard,
the major performance parameters are combustion efficiency, stabi lity
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41
limits, pressure loss, exit temperature traverse quality, and combustor
wall temperature. In general, the experimentally determined values of
these quantities show that the design goals set at the outset of the
program have been achieved.
As indicated previously (Fig 17), the combustion efficiency was
acceptably high at virtually all conditions investigated. The stabil ity
performance of Combustor B is shown in Figure 22, which consists of a
plot of the blow-out values of primary-zone equivalence ratio versus com-
bustor loading defined a~ the inverse of the combustion-efficiency para-
meter, 8 . Also indicated on the figure is the variation in combustor
loading over the operating range of the cycle. The relatively large
amount of scatter in the data is primarily due to the inherent difficulty
in obtaining an accurate determination of blow-out conditions. In the
design of the combustor, one of the requirements was that it be capable
of operating stably at a mean primary-zone equivalence ratio of 0~65
over the desired range of operating conditions. As can be seen, this
requirement was met.
Combustor B was designed to give a 3 per cent pressure drop
at full-power conditions. The actual value of pressure drop achieved,
of course, depends on the variable-geometry setting. At the 11full openll
setting corresponding to what would be typical of the setting for
design-point operation, the measured values show that the pressure drop
which would be obtained at the design-point flow conditions would be
around 2.7 per cent, approximately 90 per cent of the design value. The
dilution zone of the combustor was designed to provide an exit temperature
traverse qual ity of 0.2.
The data given in Tables IX-XI I I show that the
experimentally determined traverse qual ity
most values fall ing below the design goal.
)
formance achieved was quite satisfactory.
ranged between 0.10-0.26 with
Therefore, the dilution per-
The design objective with
regard to cool ing performance was to maintain the combustor surface tem-
perature below 1700 degrees F. The 1 iner temperature was measured using
thermal paints. Inspection of the liner showed that a maximum metal tem-
perature of about 1900 degrees F was reached in the dilution zone; in
the primary and intermediate zones the maximum metal temperature observed
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42
was on the order of 1700 degrees F, the design goal. Examination of the
test resu1ts shows that an appreciable number of tests were conducted at
primary-zone equivalence ratios close to or greater than 1.
In these
tests, the gas temperature in the dilution zone would be
significantly higher than would be encountered in normal
would account for the relatively high metal temperatures
expected to be
operation.
This
observed in the
d i 1 ut ion zone.
In any event, the cool ing performance achieved is quite
reasonable for an initial design and could be corrected if necessary with
a relatively minor expenditure of development effort.
Discussion of Test Results for Combustor A
A total of sixteen runs consisting of approximately 110 detailed
tests of Combustor A were conducted.
nomina1 ranges of flow conditions:
These tests covered the following
Over-all air/fuel ratio
24 - 88 psia
700 - 1200 deg F
0.32 - 1.39 1bm per sec
60 - 480
Pressure level
Inlet temperature
Air flow rate
The tests were performed for two different variable-geometry settings
('~Iosed'r, corresponding to what would be an approximately idle setting,
and "part open", corresponding to approximately a 50 per cent power setting)
and one fuel nozzle (A2.l). It had been planned to conduct additional
tests at a "full-open" setting. However, the initial results indicated
that this would not add significantly to the understanding of the emission
problem.
Instead, then, a number of tests were conducted with various
modifications of the original combustor configuration which proved quite
fruitful as described subsequently in this section of the report. The
results obtained with Combustor B showed that emissions varied more sig-
nificantly with combustor pressure loss and residence time than with the
standard combustion-efficiency parameter originally selected as the major
correlating parameter. Therefore, the approach adopted in selecting the
combinations of flow conditions for Combustor A was to test at a number
of different approximately constant values of absolute pressure loss and
residence time.
The nomin~l test conditions examined in each run are
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43
listed in Table XIV, the results obtained in each test are given in Tables
XV and XVI.
Emission Performance
The pertinent results are summarized in Figures 23 and 24 which
show plots of emissions (NOx, CO, and HC) and combustion efficiency ver-
sus over-all air/fuel ratio. The level of NOx emissions for Combustor A
is significantly higher than that obtained for Combustor B primarily due
to the higher temperatures at which the tests were conducted. As can be
seen, the NOx emissions are higher than the goal in all cases, ranging
from a maximum emission index of about 25 mg per gm fuel to a minimum of
around 5 mg per gm fuel. The carbon monoxide and hydrocarbon emissions
are significantly lower than those obtained with Combustor B, almost all
of the poinfs falling well below the goals. The combustion efficiency is
essentially 100 per cent at virtually all conditions investigated.
The general trends of the data are again as would be predicted;
. increasing residence time, temperature, and pressure and decreasing pres-
sure drop and over-all air/fuel ratio produce increases in NOx emissions
and have the opposite effect on CO and HC emissions. The effect of resi-
dence time on NOx emissions is essentially the same as observed for Com-
bustor B; that is, the variation with residence time is somewhat less than
linear.
The typical effects of inlet temperature and pressure and com-
bustor pressure drop on NOx emissions for Combustor A are illustrated by
the curves shown in Figure 25. Although increasing pressure or tem-
perature increases the over-all level of NOx emissions, it also widens
the stabil ity margin considerably allowing operation at much higher
values of air/fuel ratio (lower values of ~p ). Consequently, the
minimum value of NOx achievable using variable geometry to control the
primary-zone equivalence ratio is relatively independent of pressure or
temperature.
As the pressure drop is increased, the mixing in the com-
bustor improves resulting in a more uniform fuel/air distribution.
Al-
though it is difficult to isolate the effect of residence time, some
indication of the effect of improved mixing can be obtained by comparing
the curves for Runs 61 and 60 shown in Figure 25. As can be seen, im-
proving the mixing tends to produce a steeper slope of NOx versus air/fuel
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44
ratio. As a result, achieving a more uniform distribution tends to pro-
duce an increase in NOx at low values of air/fuel ratio and a decrease at
higher values.
Other Performance Parameters
As in the case of Combustor B, the major performance parameters
of concern other than emissions are combustion efficiency, stabil ity
1 imits, pressure loss, exit temperature traverse qual ity, and combustor
wall temperature.
In general, the experimentally measured values of these
parameters either matched or surpassed the selected design goals.
A combustion efficiency of essentially 100 per cent was observed
in all cases. The stabil ity performance of Combustor A is shown by the
plot of blow-out values of primary-zone equivalence ratio versus combustor
loading given in Figure 26. The design goal in terms of stabil ity was
that the combustor be capable of operation at a mean primary-zone equiv-
alence ratio of 0.5 over the range in loading parameter indicated in
Figure 26. As can be seen, this requirement was satisfied by the final
combustor configuration.
In terms of pressure-loss characteristics, the design goal for
the combustor was a 3 per cent pressure drop at full-power conditions.
Although the combustor was not tested at a variable-geometry setting
corresponding to the design point, the data obtained at the '~losed"
(idle) and "part open" (50 per cent power) settings Can be extrapolated
to determine the value of AP which would be achieved at the design point.
The data obtained show that the pressure drop at full-power conditions
would be quite close to the design goal.
The results given in Tables XV and XVI show that the measured
values of exit traverse quality ranged between 0.06 and 0.26. Most of
these values fall well below the design goal of 0.2 indicating that the
di lution zone performance was quite satisfactory and that more than enough
di lution air was avai lable for achieving the desired exit temperature
profi Ie. Thermal-paint measurements indicated that the liner temperature
was approximately 200 degrees F higher than the design goal of 1700 de-
grees F in the primary zone and about equal to the design goal in
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45
the intermediate zone.
The liner temperature in the dilution zone was
significantly lower, on the order of 1500-1600 degrees F.
This trend is
not surprising in view of the somewhat more conservative cooling approach
used in the di lution zone (see Fig 9). The relatively high values of
liner temperature observed in the primary zone are most likely due to the
fact that a significant number of tests were conducted at primary-zone
equivalence ratios near stoichiometric resulting in higher flame tempera-
tures than would normally be encountered. In any case, this situation
could be alleviated easily if necessary by using some of the excess di-
lution air avai lable to increase the amount of film cooling in the pri-
mary and intermediate zones.
Analysis of Results
The experimental results clearly show that the singularly un-
satisfactory feature of the existing combustor configurations is their
excessive NOx emission-- other combustor performance parameters,
including
other emissions, can be considered satisfactory and in fact the variable-
geometry concept can also be judged successful from the standpoint that
all emissions can be made relatively independent of power level. Thus,
the primary questions to be resolved in the critical analysis of the
data concerned the source of the present NOx emissions, and the el im-
ination of this source.
Potential Causes of Hiqh NOx Emissions
Fundamentally, there are four possible causes of excessive NO
formation in these combustors (see Fig 27).
1.
Insufficient Primary Zone Air Flow - If the air flow which
participates in the primary-zone combustion process
(primarily M~N' ~SW' and W1~.Ip) is inadequate, the mean
primary-zone equivalence ratio will be too high to suppress
2.
NO formation.
Excessive Residence Time - If in conjunction with a fuel/
air ratio distribution which produces an appreciable
fraction of the primary-zone mixture with an equivalence
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46
ratio in excess of approximately 0.7, the residence time
in the primary zone is too long, substantial quantities of
NO wi 11 be formed.
This residence time can be character-
3.
ized by the transit time of a mixture element along the
streamline S-SY in Figure 27.
Improper Fuel Atomization - Inadequate atomization, alone,
could reduce NO production in the primary zone due to de-
creased fuel vaporization and hence leaner mixtures.
If,
however, inadequate atomization is accompanied by a de-
crease in effective cone angle of the fuel spray such that
fuel is injected directly into the recirculation zone, the
4.
resulting higher equivalence ratios wi 11 result in greater
NO production.
Inadequate Fuel/Air Mixinq - If the fuel is inadequately
mixed with the primary-zone air, then local regions in the
primary zone will be at relatively high equivalence ratios,
and substantial NO will be produced. In the present com-
bustors, the qual ity of mixing is best displayed by the
fuel/air ratio profile across the section A-A in Figure 27.
As shown in Figure 28, a poorly mixed profile can provide
a substantial maximum in local fuel/air ratio.
The experimental data obtained, in conjunction with an analytical exam-
ination of the NOx emissions from the combustors, permit some con-
elusions with respect to the relative importance of these possible
sources.
Experimental Observations
Considering the four possible causes in order, the experimental
data obtained
1.
permit the following interpretations:
Insufficient Primary-Zone Air Flow - The behavior of the
NOx emissions as a function of over-all air/fuel ratio ( Z. )
indicates that this is not a major cause of excessive NO
formation for these combustors. For example, for the data
point shown in Figure 23 for Combustor A at an over-all
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47
air/fuel ratio of 479, the most pessimistic (that is, low-
est) estimate of primary-zone air flow would yield a mean
primary-zone equivalence ratio of 0.3; given a reasonable
distribution of fuel/air ratio in the primary zone, vir-
2.
tually no NO should be produced.
Excessive Residence Time - Although the experimental data
do indicate the expected effect of increasing NO production
with increasing residence time, the effect does not appear
to be very substantial (see Fig 18). Further, referring
again to the 2 = 479 point in Figure 23, given a reason-
able fuel/air distribution, virtually no NO should be
produced regardless of residence time. It 15 als~ clear that
to satisfy the NOx emission objectives, a reduction of as
much as a factor of ten is required; this obviously could
not be accompl ished by merely reducing the primary-zone
residence time.
3.
Improper Fuel Atomization - As mentioned previously, poor
fuel atomization, alone, would not seem to account for
excessive NO production. However, poor fuel atomization in
conjunction with a smaller effective cone angle is a
likely cause; unfortunately, there is no direct experimental
evidence which sheds I ight on the importance of the cause.
Characteristics of airblast atomizers are such that the
effective cone angle is relatively constant, and the spray
visual ization tests described previously indicate
that the cone angle is satisfactory except at very low
pressure differentials across the nozzle. The fact that
Combustor A sustains combustion at very high values of
over-all air/fuel ratio is however an indication of a
4.
possible reduction in effective spray angle.
Inadequate Fuel/Air Mixinq - From the preceding discussion,
it can be inferred that the fuel/air mixture in the primary
zone is highly nonuniform-- this is virtually the only
possible explanation. Unfortunately, there is again little
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48
direct experimental evidence that this is the case.
For
example, it would be expected that the pressure loss at
which the combustors were operated would have an appre-
ciable influence on NOx emission; although the experi-
mental data exhibit some influence of pressure drop,
there is no clear trend in this regard. The absence of
such a t rend does i nd i cate, however, that if Jnadequate .
mixing is a problem, it most 1 ikely occurs in the im-
mediate vicinity of the nozzle. This view is also
supported by both the basic characteristics of the ai~
blast nozzle, which reI ies on the swirler and fuel nozzle
air to distribute the fuel, and the fact that in the present
combustors the ratio of the fuel flow to the sum of nozzle
and swirler air is well above the stoichiometric value.
Additional confirmation of this view is provided by the re-
sults of the spray analysis tests described in Appendix III
which show that a relatively nonuniform fuel/air distribu-
tion is obtained from the nozzle.
Thus, on the basis of the experimental data obtained, it can be concluded
i.
that the excessive NOx levels are due to either inadequate fuel/air mix-
ing in the vicinity of the nozzle or possibly due to an insufficient fuel
spray angle.
Results of Analvtical Modell inq
..
In order to clarify further the possible sources of NOx
emissions in the two combustors, the analytical model previously de-
veloped by NREC (Refs 1 and 2) for predicting NOx emissions from gas-
turbine combustors was used to obtain analytical estimates of NO produc-
tion in the two combustors. As described earlier in this report, the
model is based on the concept of a primary zone which behaves as a
partially stirred reactor, in which combustion occurs over a speci-
fied Gaussian distribution of fuel/air ratios. The parameter governing
the fuel/air ratio distribution is the mixedness parameter, So , which
defines the distribution of fuel/air ratios about the mean fuel/air
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. .
49
ratio in the primary zone. The larger the parameter
is the mixing in the primary zone.
The analytical results for Combustor B, for two values of the
So , the poorer
mixedness parameter, are compared with the experimental data in Figure 29.
On the basis of the slope of the analytical results as compared to the data,
it can be concluded that the empirical value of So for Combustor B is some-
what greater than unity. This represents a poorly mixed primary zone (values
of ~o for typical aircraft combustors have been found to be in the range of
0.3 to 0.7). To appreciate further the significance of the value of £0' the
results obtained from the analytical model can be approximately related to the
percentage of the mixture in the primary zone which burns at equivalence ratios
greater than 0.8. Although previous experience with the analytical model has
indicated that it somewhat underpredicts NO formation at lower inlet tempera-
tures (a fac~ also indicated by the discrepancy between predicted and measured
results here), it nevertheless seems certain from the combination of analytical
and experimental data that a substantial fraction of the injected fuel is burn-
ing at equivalence ratios greater than 0.8.
Simi lar results are presented for Combustor A in Figure 30.
Here a value of So slightly less than unity is indicated, and it can
be deduced from the results of the model that approximately 30 per cent
of the injected fuel burns at equivalence ratios greater than 0.8 for
all air/fuel ratios.
Although the analytical model is undoubtedly subject to some
uncertainty, the nature of the results clearly indicates that in the
two combustors a substantial fraction of the injected fuel burns at
equivalence ratios greater than 0.8, even though the mean primary-zone
equivalence ratio may be less than 0.4.
Maior Conclusions
The preponderance of the evidence indicates that the source of
excessive NOx emissions in the present combustors is inadequate fuel/air
mixing in the primary zone.
This in turn is due both to inadequate dis-
tribution of the fuel spray in the swirler and nozzle air streams, and
to an inadequate proportion of air to the nozzle and swirler relative to
the flow through the secondary holes.
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50
Experimental Verification of Analysis
Description of Tests
A number of tests were conducted with modifications of the
original Combustor A configuration in order to confirm the conclusions
discussed above regarding the source of the high NOx emissions. The
previous experimental and analytical results indicated that the amount
of air flow in the vicinity of the fuel spray must be increased and
the mixing of the fuel with the air prior to burning must be improved
to achieve the required reductions in emissions. The simplest method
of accompl ishing this effect without excessive alterations to the
original configuration was to increase the amount of air flow and
pressure drop through the nozzle and the swirler. This was done by
placing a p~rforated plate with an open area of about 1.9 square inches
across the combustor flow annulus to redistribute the flow and pressure
drop as desired. Essentially two modifications as shown schematically
in Figure 31 were investigated:
I. Placing the perforated plate at an axial position just
downstream of the nozzle inlet to increase the amount of
air flow and pressure drop through the nozzle only (Fig 3Ia).
2. Placing the plate at an axial position just downstream of
the swir1er inlet to increase the air flow and pressure
drop through both the nozzle and swirler (Fig 3Ib).
In addition, the diameter of the dilution holes was reduced to 0.625 inches.
Nevertheless the pressure drop across the portion of the combustor down-
stream of the plate was nominally the same as would be obtained with the
original configuration.
A total of 15 runs consisting of approximately 80 tests were
performed. All of the tests were conducted with the piloted version of
the Combustor A nozzle (A2.2), with a fixed setting of the secondary-
flow control sleeve (about half open), and at a nominal inlet tempera-
ture of 900 degrees F. The tests were performed with a number of values
of air flow rate at each of two different pressure levels. An additional
parameter investigated was the relative proportion of fuel flow through
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51
the pilot and main airblast portion of the nozzl~.
The nom i na 1 tes t
conditions examined in each run are 1 istedin Table XVI I; the calculated
values of nozzle, swirler, and primary-zone air flow for the variable-
geometry settings examined are given in Table XVI I I for each of the two
modifications.
The results obtained in each test are given in
Tables XIX-XXI.
Discussion of Results
The pertinent results obtained in these tests are presented
in Figure 32 which shows NOx and CO emissions plotted versus over-all
air/fuel ratio for the two pressure levels investigated. Also included
in the figure are the results obtained previously with the original
Combustor A at comparable flow conditions. As can be seen, the NOx
emissions have been reduced quite dramatically by a factor ranging
between 4 and 8. The minimum value of NOx emission index achieved with
the modified configuration falls close to or below the goal for both
pressure levels investigated. The CO emissions have also been reduced
somewhat over a major portion of the range of conditions examined.
However, with the modified configuration lean blowout occurs at lower
values of air/fuel ratio, thus reducing the stability limits.
Several important observations can be made on the basis of a
detailed examination of the test results obtained with the modified con-
figuration.
In all cases, increasing the amount of air flow in the
vicinity of the fuel spray led to significant reduc.tions in NOx emis-
sions without seriously compromising CO emissions.
The effect of in-
creasing the nozzle air flow is to reduce the local fuel/air ratio (see
Fig 28) near the flame thus decreasing the relative proportion of fuel
burned at high equivalence ratios. Increasing the air flow and pressure
drop through the swirler increases the relative velocity and shear be-
tween the counterrotating swirler and nozzle streams thus improving the
loca.l mixing achievable for a given pressure loss.
This effect is indi-
cated by the results obtained for an increased swirler flow (Table XXI)
where approximately the same emission level was achieved at a signifi-
cantly lower pressure loss.
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52
Although increasing the air flow and pressure drop through the
nozzle/swirler assembly reduced emissions, increasing the pressure drop
and decreasing the residence time by increasing the total air flow rate
did not seem to have any significant effect on emissions. This is shown
by the results plotted in Figure 33 for two different values of total
air flow rate.
As can be seen, increasing the pressure drop by about
50 per cent and decreasing the residence time by approximately 25 per cent
had no discernible effect on the emissions.
This indicates that the amount
of mixing which can be achieved by purely aerodynamic means (that is,
increasing pressure loss for a given configuration by increasing air flow
rate with a corresponding increase in fuel flow rate) is limited. These
results also support the conclusion previously reached that reducing
residence time is not a practical method of control 1 ing NOx emissions.
The NOx emission curves for the modified configuration shown
in Figure 32 exhibit a reduction in slope at the high values of air/fuel
ratio. For the tests conducted at these values of air/fuel ratio a major
portion or al1 of the fuel was injected through t~e pilot in order to
maintain stable combustion; in addition, the total fuel flow was com-
paratively low. A characteristic of the pilot, which is a pressure
atomizer, is that the spray cone angle decreases as the fuel flow is
reduced leading to a local increase in the equivalence ratio in the
vicinity of the nozzle. This effect of a deterioration in the uniformity
of the fuel/air distribution would explain the observed behavior of the
curves.
The relative effects of the main airblast and. pilot portions of
the nozzle are illustrated by the results presented in Figure 34 which
shows the NOx emissions obtained for three different types of fuel in-
jection: main airblast operating alone, pilot operating alone, and the
main operating in conjunction with the pilot. In the latter case, the
fuel-flow rate through the pilot was maintained constant at approximately
12 Ibm per hour. At a given value of air/fuel ratio, the NOx emissions
achieved with the main airblast portion of the nozzle are considerably
lower than with the pilot; however, flame blow-out occurred at relatively
low values of over-all air/fuel ratio (1 ). As can be seen, introducing
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53
a small amount of fuel through the pilot has the desired effect of ex-
tending the range of air/fuel ratio over which stable combustion can be
maintained.
At low values of 2
where the ratio of pilot to main fuel
flow is relatively small, the NOx emissions achieved with the main/pilot
combination are approximately the same as with the airblast portion alone.
The emission performance of the combination approaches that of the pilot
at higher values of l where proportionately more fuel flows through the
pilot. It would seem apparent from these results that there is some
optimum combination of main and pilot fuel flow rates which would extend
the operating range of the nozzle and achieve an improvement in NOx
emissions.
All of the experimental evidence obtained in these tests showed
that improving the uniformity of the primary-zone fuel/air distribution
by increasin9 the mixing and el iminating insofar as possible local fuel-
rich regions produced the desired effect on emissions.
In summary, the
test results confirm the conclusions previously reached regarding the most
effective means of achieving the necessary reductions in emissions.
Recommended Approaches for Achievinq Low Emissions
Although not all of the emission goals were achieved in the
present program, the results obtained were sufficiently promising to
demonstrate that th~ concept originally selected has the ultimate po-
tential of producing reduced emission levels which will meet the Federal
1975/76 emission goals. Initial considerations of the problem of NOx
control had suggested that novel concepts representing radical departures
from conventional design practice would be required. However, on the
basis of the test results and a critical analysis of the data, it is
now felt that the emission goals can be achieved with modifications of
essentially conventional combustor configurations. Therefore, the
general guidel ines for control 1 ing emissions presented here are discussed
in terms of this type of approach.
Control of Primary-Zone Equivalence Ratio
By far the most important factor with regard to NOx emissions
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54
has been shown to be the mean value of primary-zone equivalence ratio and
the distribution about this mean value.
In order to achieve the specified
NOx emission level, most of the fuel injected into the primary zone must
burn at a uniformly lean value of equivalence ratio.
In fact it would
appear that the primary zone of the combustor must operate at equivalence
ratios very near the weak extinction I imit over the full range of cycle
conditions.
There is I ittle doubt that in order to accompl ish this the
operating conditions in the primary zone of the combustor must be capable
of being controlled independently of the cycle conditions. The approach
investigated in this program of using variable geometry has been shown to
be an effective means of providing the necessary additional degree of
freedom. An alternative to variable geometry would be some form of
staged injection. However, since this concept was not examined, no con-
clusions reg.arding its appl icabil ity can be made.
The test results also showed that increasing the combustor inlet
temperature and pressure has a major effect on increasing NOx emissions
for a given primary-zone equivalence ratio.
However, the minimum achievable
values of NOx emissions appeared to be relatively insensitive to the
inlet pressure and temperature due to the fact that increasing P~3 and
~3 allows operation at considerably lower values of primary-zone
equivalence ratio. In fact, there is some evidence to indicate that
these parameters have a greater effect on flame stabil ity than on
emissions. Therefore, the emiss;ons can be made virtually independent
of combustor inlet conditions by using variable geometry to control the
primary-zone equivalence ratio as required by the operating conditions
of the specific cycle being considered.
In choosing the variable-geometry method to be used for any
particular configuration, it should be noted that simply control I ing
the mean value of primary-zone equivalence ratio is not sufficient to
achieve the necessary reductions in emissions.
It has been found that
it is most important to control the air flow in the immediate vicinity
of the fuel as it is introduced into the combustor. Therefore, the
variable-geometry approach utilized should be coordinated with the
selected method of fuel injection to insure that its primary function
is accompl ished effectively.
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55
Reduction of CO and HC Emissions
The necessity of burning at a lean primary-zone equivalence
ratio aggravates the problem of achieving low levels of CO and HC emis-
sions (that is, high combustion efficiency). The results have shown
that residence time has a significantly greater effect on the emissions
of these species than on the emissions of NOx. The approach for control-
I ing CO and HC adopted in the design of the two combustors was based on
this effect and consisted of oversizing the combustor diameter 50 as to
increase the residence time. This approach appears to have been success-
ful in that low emissions of these species were achieved. It would seem
worthwhile to augment the specific approach util ized by lengthening the
intermediate zone (moving the dilution holes further downstream).
Mixinq
As mentioned above, it is necessary to achieve a uniform fuel/
air distribution in the primary zone in order to reduce NOx emissions to
the specified level. This requires that most of the fuel be mixed suf-
ficiently well with the primary-zone air participating in the combustion
process prior to combustion. The results of the program show that simply
increasing the pressure drop to achieve the desired degree of mixing by
purely aerodynamic means is not an efficient or practical approach.
Excessively high values of pressure drop would be required which would
represent an unacceptable penalty on cyc1e performance.
The selected
approach which consisted of oversizing the combustor diameter to achieve
a relatively high pressure-loss factor at reasonable values of pressure
drop did appear to provide an adequate over-all degree of mixing as
determined by the results of flow visual ization tests conducted. However,
it seems apparent that improving the over-all level of mixing in the
primary zone is insufficient un1ess care is also taken to el iminate
local ized regiQns of high fuel/air ratio such as exist at the point of
fuel injection. The ultimate solution to the problem of achieving an
acceptably uniform fuel/air mixture I ies in the method of introducing the
fuel into the combustor.
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56
Fuel Iniection System
One of the major conclusions reached on the basis of the test
results is that the fuel injection system is the critical factor in
determining the uniformity of the fuel/air distribution which can be
achieved for a given configuration. An ideal solution to the problem
of attaining a uniform distribution remains pre-mixing the fuel with
a sufficient quantity of air prior to entering the combustor.
This
pre-mixing can be accompl ished in a variety of ways; for example, injecting
the fuel at multiple points, using a mixing chamber of sufficient length
to achieve the desired degree of uniformity, mechanically distributing
the fuel over the flow cross-section of the airstream, or combinations
of these approaches. An alternative to pre-mixing is to use the more
conventional approach adopted in the program of preparing and introducing
the fuel in 'such a form that it will mix with sufficient air within the
primary zone prior to undergoing combustion. In doing so, test results
have demonstrated clearly the necessity of el iminating extensive regions
of high fuel concentration. However, it has also been found that a small
proportion of the fuel must be introduced at relatively high values of
equivalence ratio in order to maintain stable combustion at the lean
primary-zone conditions needed to achieve low NOx emissions.
This then
requires some form of piloting in which a part of the fuel is injected
directly into the recirculation zone. Unfortunately, the information
available is insufficient to establ ish the proportion of main/pilot
fuel flow required to achieve the optimum compromise between emission
performance and combustion stabil ity.
All of the results obtained indicate, at least reasonably con-
clusively, that the NOx emissions from the existing combustor can be sub-
stantially reduced by improving the fuel/air mixing in the primary zone
in the immediate vicinity of the exit of the fuel nozzle.
The only ef-
fective way to accompl ish this is to modify or replace the existing fuel
injector in an appropriate manner.
It is felt that the implementation
of this recommendation wi I I demonstrate the full emission reduction po-
tential of the variable-geometry concept and will show that the emission
goals can be satisfied with the exi,sting combustors.
-------
57
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
A design approach for achieving low emissions in gas turbine com-
bustors has been selected and appl ied in the design of two combustors for
automotive gas turbine appl ications. Basically, the approach utilized has
consisted of designing both combustors to operate with a lean, wel I-mixed
primary zone over the full operating range. The relevant features of the
approach included the use of variable geometry for control 1 ing the air
flow distributions in the combustors so as to maintain efficient and stable
combustion at all operating conditions, a relative\y \arge combustor diam-
eter to achieve a high combustion efficiency and to promote aerodynamic
mixing, and an airblast fuel nozzle to improve the uniformity of the fuel/
air distribution in the primary zone.
An experimental program involving
both cold-flow and combustion tests has been conducted to determine the
detailed performance of the final configurations of both combustors. The
principal conclusions reached on the basis of a critical analysis of the
program results are given below:
1.
The aerodynamic performance of both combustors as determined
from the results of the cold-flow tests was satisfactory.
The
flow patterns observed in the flow visual ization tests showed
good penetration of the secondary and dilution jets and a vigor-
ous over-all level of mixing in the primary zone at all condi-
tions.
The ambient air tests indicated that the flow distri-
butions achieved were essentially as desired and that the
variable-geometry approach util ized was capable of providing
sufficient control of the effective primary-zone air flow rate.
Qualitative spray tests of the airblast nozzles consisting
2.
of visual observations of the spray indicated that the
spray cone angle obtained with this type of nozzle does
not depend significantly on flow conditions.
However,
the cone angle is quite sensitive to the axial position
of the nozzle with respect to the inlet of the primary
zone. For all flow conditions examined, the fuel fi 1m
-------
58
leaving the nozzle persisted a significant distance into
the primary Zone resulting in a localized region of rela-
tively high fuel concentration near the nozzle lip. The
results of quantitative spray analysis tests (see Appendix
1'1) confirm that the fuel/air distribution provided by
3.
the nozzle is relatively nonuniform.
In general, the over-all levels of NOx emissions for both
combustors were significantly higher than the specified
goal. The emissions of CO and HC were generally below
the specified goals except ~t conditions very near the
weak extinction limit where the emissions of these species
rose sharply with increasing air/fuel ratio.
The measured
values of the other major performance parameters (combus-
. tion efficiency, stability limits, pressure loss, exit tem-
4.
perature traverse qual ity, and combustor wall temperature)
were quite satisfactory and essentially equal to the selected
design goals.
The general effects of combustor inlet temperature and pres-
sure on emissions are as would be expected, NOx emissions in-
creasing and CO and HC emissions decreasing as temperature
and pressure are increased at a constant value of air/fuel
ratio.
However) at high values of combustor inlet temperature
5.
and pressure, the stability limits are greatly extended al-
lowing operation at significantly lower values of primary-
zone equivalence ratio. The use of variable geometry to
control the primary-zone equivalence ratio as required has
been found to be an effective means of making the emissions
relatively independent of combustor inlet conditions.
Residence time has a somewhat less than linear effect on NOx
emissions but a strong effect on CO and HC emissions.
There-
fore, reducing residence time does not represent a practical
6.
means of
The most
reducing NOx emissions to the level required.
important factors with regard to NOx emissions are
primary-zone equivalence ratio and the distribution
the mean
-------
59
about this mean value.
An extremely uniform fuel/air dis-
tribution is required in order to meet the NOx emission goals.
Although a reasonable value of combustor pressure drop is
necessary to obtain adequate mixing, the use of an excessively
high value of AP in itself is not a practical or effective.
approach to attaining the uniform primary-zone fuel/air
distribution required. The solution to the problem of
achieving an acceptably uniform fuel/air distribution lies
in the design of the fuel injection system. The high
values of NOx emissions observed in the two combustors have
been demonstrated to be due to inadequate fuel/air mixing
in the primary zone. The test results have indicated that
this is primarily due to the method of fuel injection used
and to an insufficient proportion of the primary-zone air
introduced in the vicinity of the fuel spray.
Despite the fact that not all of the emission goals were achieved, the
experimental evidence obtained in the program has demonstrated that the
variable-geometry concept selected and utilized in the design of the two
combustors has the potential of producing the necessary reductions in
emission levels. A major conclusion on the basis of the program results
then is that the specified emission goals can be achieved with modifications
of essentially conventional combustor configurations utilizing the ap-
proaches described in this report.
Recommendations
A number of general recommendations regarding design approaches
for achieving low emissions were presented in the previous section of this
report.
These are summarized below:
I .
In order to achieve the necessary reductions in NOx emissions,
most of the fuel must be burned at low values of equivalence
ratio. Variable geometry is the approach recommended for
attaining stable and efficient combustion at these conditIons
over the full operating range of the combustor. The use of
-------
60
staged injection offers a potentially attractive alternative
to variable geometry, and it is recommended that some develop-
ment effort be devoted to investigating the feasibility of
this concept.
3.
Since NOx emissions appear to be less sensitive to residence
time than CO or HC emissions, designing for a relatively high
residence time is suggested as the most practical method of
achieving the necessary control of CO and HC emissions.
The uniformity of the primary-zone fuel/air disttibution is
the major factor in control I ing NOx emissions. The key to
obtaining necessary uniformity in the fuel/air distribution
is in the proper design of the method of introducing the
fuel into the combustor. In general, the major requirement
2.
of the fuel injection system is that the fuel be mixed
uniformly with a sufficient amount of air prior to combustion.
In doing so, care must be taken to avoid producing localized
regions of relatively high fuel concentration. The ideal
solution to the problem of achieving a uniform distribution
is to pre-mix the fuel and air before entering the combustor.
An alternative to pre-mixing is to use essentially conventional
injector configurations modified to achieve a more rapid dis-
persal of the fuel in the primary-zone air prior to combustion.
The program results have indicated that the variable-geometry con-
cept utilized has the ultimate potential of achieving emission levels which
will meet the Federal 1975/76 emission goals. Analysis of these results
has pointed out specific areas in which further development effort is re-
quired in order to obtain the necessary reductions in emissions. With re-
gard to the configurations investigated in the program, the major aspect
requiring improvement is the method of fuel injection. It is felt that
the replacement or modification of the existing fuel injector to achieve
a more uniform fuel/air distribution in the primary zone should result
in achieving the emission goals. The ability to meet the emission stand-
ards in what is essentially a conventional combustor configuration with
a single point of fuel injection and most likely a single variable-
geometry element has an obvious advantage. Subsequent designs could rely
-------
61
heavily on the extensive background and experience available on the design
technology of conventional combustor configurations. For these reasons,
it is strongly recommended that development of the emission-control ap-
proach utilized in the design of the two combustors be continued to demon-
strate fully the capabi lity of this concept in meeting the emission goals.
. ,
-------
62
REFERENCES
1.
Fletcher, R. S. and Heywood, J. B., A Model for Nitric Oxide Emis-
sions from Aircraft Gas Turbine Enqines (AIAA Paper No. 71-123),
American Institute of Aeronautics and Astronautics, New York, 1971.
2.
Fletcher, R. S., Siegel, R. D., and Bastress, E. K., The Control of
Oxides of Nitroqen Emissions from Aircraft Gas Turbine Engines, Volume
1: Proqram Description and Results (NREC Report No. 1162-1), Northern
Research and Engineering Corporation, Cambridge, Mass., December, 1971.
3.
Bastress, E. K., et aI, Control of Nitroqen Oxide Emissions from Diesel
Enqines: A Theoretical Analysis (NREC Report No. 1160-1), Northern
Research and Engineering Corporation. Cambridge, Mass., June 8, 1971.
4.
"Exhaust Emission Standards and Test Procedures", Federal Reqister,
Washington, D. C., vol. 36, no. 128, July, 1971.
5.
Control Techniques for Particulate Air Pollutants (NAPCA Publ ication
No. AP-5l) National Air Pollution Control Administration, Department
of Health, Education, and Welfare, January, 1969.
6.
Butze, H. E. Trout, A. M., and Moyer, H. M., Performance of Swirl-
Can Turboiet Combustors at Simulated Supersonic Combustor-Inlet
Conditions (NASA TN D-4996) National Aeronautics and Space Adminis-
tration, Washington, D. C., January, 1969.
7.
Low NOx Emission Combustor for Automobile Gas Turbine Enqines (NREC
Report No. 959-111), Northern Research and Engineering Corporation,
Cambridge, Mass., January 25, 1971.
8.
The Desiqn and Performance Analysis of Gas-Turbine Combustion Chambers,
Volume I: Theory and Practice of Desiqn (NREC Report No. 1082-l},
Northern Research and Engineering Corporation, Cambridge, Mass.,
Decembe r, 1964.
9.
The Desiqn and Performance
Volume 1': Desiqn Methods
1082-2), Northern Research
MHSS.. December, 1964.
Analysis of Gas-Turbine Combustion Chambers,
and Development Techniques (NREC Report No.
and Engineering Corporation, Cambridge,
10.
Investigation of Gas-Turbine Enqine Components, Part I: Over-all
Cycle and System Studies, (NREC Report No. 1099-1), Northern Research
and Engineering Corporation, Cambridge, Mass., July 15, 1966.
11.
Cornelius, W., Stivender, D. lo, and Sullivan, R. E., A Combustion
System for a Vehicular Reqenerative Gas Turbine Featurinq Low Air
Pollutant Emissions (SAE Paper No. 670936) Society of Automotive
Engineers, Inc., 1967. .
-------
22.
23.
24.
63
12.
Montgomery, J. E., Furst, D. G., and Schelp, H. R., 200-300 HP Gas
Turbine Enqine Family for the U. S. Army (SAE Paper No. 795A) Society
of Automotive Engineers, Inc., 1964.
13.
Kahle, G. W., The Turbine Powered Vehicle -- Promises or Profit (SAE
Paper No. 660171) Society of Automotive Engineers, 1965.
14.
Haasis, J. M., Development of the Combustion System for the AiResearch
TPE331 Turboprop Enqine (ASME Paper No. 67-GT-25) The American Society
of Mechanical Engineers, 1967.
15.
Collet, P. J., A 3-Shaft Versus a 2-Shaft Cycle in Automotive Gas
Turbines (SAE Paper No. 670955) Society of Automotive Engineers,
1967.
16.
Bell, L. E., Desiqn Requirements of Small Hiqh-Temperature Rise
Combustors (SAE Paper No. 680447) Society of Automotive Engineers,
1968.
17.
Wright, E. S., The Potential of the Gas-Turbine Vehicle in Alleviating
Air Pol"lution (ASME Paper No. 70-WA/GT-8) The American Society of
Mechanical Engineers, 1970.
18.
A Rapid Estimation Method for Nitric Oxide Emissions from Gas
Turbine Combustors (NREC Internal Technical Memorandum), Northern
Research and Engineering Corporation, Cambridge, Mass., January 4, 1971.
19.
Computer Proqram for the Analysis of Annular Combustors (NREC
Report No. 1111), Northern Research and Engineering Corporation,
Cambridge, Mass., Sponsored by NASA Lewis Research Center under
Contract No. NAS3-9402, January 29, 1968.
20.
Lefebvre, A. H. and Norster, E., R., '~he Design of Tubular Gas
Turbine Combustion Chambers for Optimum Mixing Performance'.,
Proceedinqs of the Institution of Mechanical Enqineers, vol. 183,
part 3N, 1968-69.
21.
Instruments and Apparatus: Chapter 4 Flow Measurement, Part 5 -
Measurement of Quantity of Materials (Supplement of ASME Paper No.
PTC 19.5; 4) The American Society of Mechanical Engineers, 1959.
Aircraft Gas Turbine En ine Exhaust Smoke Measurement (SAE Paper No.
ARP 1179 Society of Automotive Engineers, 1970.
Findl, E., Brande, H., and Edwards, H., Study of Physiochemical
Properties of Selected Mil itary Fuels, (AD 274623) Armed Services
Technical Information Agency, 1960.
Hougen, O. A., Ragatz, R. A., and Watson, K. M., Chemical Process
Principles, Part I: Material and Enerqy Balances, 1954.
-------
64
25.
Simmons, Harold C. and Lapera, Dominic J., A High-Speed Spray Analyzer
for Gas Turbine Fuel Nozzles, Presented at Session 26 of ASME Gas Tur-
bine Conference, Cleveland, Ohio, March 12, 1969.
26.
ort for Oro let Size Measurement and Anal sis
Hannifin, Cleveland, Ohio, September, 1972.
-------
65
TABLES
-------
66
TABLE I
FEDERAL 1975/76 EMISSION GOALS
Vehicle Emission
Goals (qrams/mi1e)
Combustor Emission
Goa1s* (mq/q fue1)
Hydrocarbons (HC)7~~
Carbon Monoxide (CO)
Oxides of Nitrogen (NOx)***
0.41
. 3.4
0.40
1.42
11.8
1. 38
For 10.0 miles/gal fuel economy and Jp-4 jet fuel (5. G. =
.763)
Total hydrocarbons plus total aldehydes
NOx computed as N02
--k
;':-;t~
;'~':,,;'~
-------
67
TABLE II
ASSUMED CYC LE OPERATING CONDITIONS FOR DESIGN OF COMBUSTORS
Net
Power
Output. . 1;:3
Per Cent ri1~ MF ~ ~4
of Desiqn ( 1 bm/ see) ( 1 bm/h r) Z (atm) ( deq F) (deq F)
Combustor A
Design 100 1.56 51 . 1 110 4.00 1100 1700
75 1. 25 37.8 119 3.31 1160 1700
50 1. 03 27.6 134.5 2.69 1200 1690
25 .845 17. I 178 2. II 1200 1670
Idle 0 .765 9.2 299 1.60 1200 1420
Combustor B
Design 100 . 1,.43 89.6 57.5 12~ 0 760 1900
75 1 . 17 68. 1 62.0 9.60 565 1625
50 .915 46.6 70.7 8.15 540 1475
25 .658 26.9 88.0 7.31 527 1280
Idle 0 .400 12.6 115.0 5.28 442 1019
-------
TABLE III
68
SELECTED COMBUSTOR DESIGN CONDITIONS
Inlet Temperature, deg F
Inlet Pressure, atm
Air Flow Rate, Ibm per sec
Temperature Rise, deg F
Heating Rate, Btu per hr
Exit Temperature Traverse Quality
Maximum Combustor Wall Temperature, deg F
Pressure Drop, per cent of inlet pressure
Pressure-Loss Factor (
AP /fr~f )
Combustion Efficiency, per cent
Primary-Zone Equivalence Ratio (
fr> )
Combustor A Combustor B
1100 760
4 12
1.56 1.43
600 1140
6 6
0.96 x 10 1 . 68 x 1 0
,2 .2
1700 1700
3 3
90 90
99.8 99.8
.5 .65
-------
69
TABLE IV
DESIGN DISTRIBUTIONS OF AIRFLOW*
Flow Rates,
Per Cent of Total
Combustor A Combustor B
Secondary Holes,
Dilution Holes,
Sw i r 1 e r , ..v, .
~"\I'
.
rv\!o Y
.
W1,{.: I
24.2 35.6
40.0 26. I
6. 2~', ~': 1 o. 3~'o',
3 . 6 ~':~': 7 . O~b':
2.0 2.0
6.0 5.0
6.0 5.0
8.0 5.0
.5 .5
3.5 3.5
Fue I Nozz 1 e, vv,p#
Dome Film-Cooling Slot, '~cfld
Primary-Zone Film-Cooling Slot, tV,d ..
--r' {-
Intermediate-Zone Film-Cooling Slot, ,,.1,,,.
. LTJ ~
Dilution-Zone Film-Cooling Slot, ty.tJ. .1./
~ "I .i"" .
Plug Cooling, ~
~p
Flow, .VI,
bl~.(...,
Spark
Bleed
*See Figure 5 for definition of flow streams.
**These values are for a nozzle air/fuel ratio of 4.
-------
TA8LE V
NOZZLE DESIGN SPECIFICATIONS
Desiqn Nozzle
Nozzle Desiqn Nozzle Ai r Flow,
Desiqnation Desc r i pt ion Air / F ue I Rat io Per Cent of Total
A2. I No pi lot nozzle 4 3.6
A2.2 With pilot nozzle 4 3.6
8 I . I No pi lot nozz I e 2 3.5
8 1.2 With pilot nozzle 2 3.5
82. I No pilot nozzle 4 7.0
82.2 With pilot nozzle 4 7.0
Notes:
I .
The "A" nozzles were designed for Combustor A and the "8"
nozzles for Combustor 8. However, nozzles 82. I and 82.2
were capable of being tested in both combustors.
2.
For all nozzles:
Main spray cone angle = 90 degrees
Pilot spray cone angle = 70 degrees
Pilot flow number = 0.42 gal per hr per psi 0.5
70
-------
TABLE V I
METERING AND BLEED HOLE DIMENSIONS
Meterinq Holes
71
Combustor A
Combustor B
No. of Hole
Cool i nq Slot Location Holes Diameter, in
Dome 54 .065
Primary Zone 40 .133
Intermediate Zone 40 .133
D i 1 uti on Zone 40 .154
No. of
Holes
30
40
30
30
I.
Bleed Holes
rJ..
__L_~.l
rJ-YC .~w
No. of d I W
Holes in 112 112
Combustor A 24 .063 .320 .032
Combustor B 24 .052 .312 .025
Hole
Diameter, in
.0455
.0628
.0725
.0725
-------
TABLE VII
.72
AVERAGE VALUES OF EFFECTIVE FLOW AREAS
CALCULATED FROM RESULTS OF COLD-AIR TESTS
Flow Element
Dome Slot
Primary Zone Slot
Intermediate Zone Slot
Dilution Zone Slot
Dilution Holes
Bleed Holes
Spark Plug
Nozzle: J A2. 1, A2.2
Sw i r 1 e r: .{5i.\F .0
.2
.4
.6
.8
Secondary Holes: tsy =
Combustor A
.0
.3
.6
.9
1.2
Itt{f sq ft
1. 03
2.71
2.75
3 70
16.52
1.03
.35
1. 25
.18
.79
1.42
2.03
2.50
1.00
4.17
7.31
10.46
12.61
x 10-3
-------
73
TABLE VII (CONTINUED)
AVERAGE VALUES OF EFFECTIVE FLOW AREAS
CALCULATED FROM RESULTS OF COLD-AIR TESTS
Flow Element
Dome Slot
Primary Zone Slot.
Intermediate Zone Slot
Dilution Zone Slot
Dilution Holes
Bleed Holes
Spark Plug
Nozzle: B1.1, B1.2
B2.1, B2.2
Swirler: . .t~w = .0
.05
.15
.25
.35
Seconda ry Ho 1 es : fs:J =
Combustor B
.0
.20
.40
.60
.75
() II 3
I11rJlfr.Sq ft x 10-
.211
.665
'.713
..661
2.83
.551
.300
..358
.763
.151
.738
.552
..798
1.095
.350
1. 56
2.79
4.00
4.92
-------
TABLE VI II
SUMMARY OF T :S'. CONDITIONS EXAMINED WITH COMBUS'.) ~ B
AP
Run ~'w in A.y Fb3 {;3 per cent of Lp
No. Nozzle in psia deq F MG.,.. Ibm per see in 1 et pressure msec
13 81.1 .1 .3 68 515 .305 1.1 22
14 1 725 .375 2. 1 14
15 735 ..425 2.6 13
16 735 .480 3.4 11
17 705 .545 4.3 10
18 890 .840 9.1 5
19 88 730 .770 5.4 9
20 53 730 .320 2.5 13
29 78 530 .390 1.3 19
21 B1.1 .35 .75 68 520 .305 .5 16
22 j 700 .390 1.1 11
23 710 .420 1.4 10
24 695 .485 1.8 9
25 690 .545 2.2 8
26 875 .840 6.3 4
27 88 710 .775 2.8 7
28 53 700 .320 1.3 10
30 68 695 .850 5.6 5
31 78 510 .390 .7 15
37 B2.1 .1 .3 68 700 .390 1.9 13
38 ! 700 .430 2.3 12
39 690 .545 3.8 9
40 78 515 .390 1.2 18
41 68 890 .840 10.8 5
42 88 705 .785 4.7 8
32 B2.1 .35 .75 68 700 .385 1.0 10
33 I 1 1 705 .435 1.2 9
34 690 .590 2.2 7
35 78 520 .385 .6 14
36 88 705 .780 2.6 6 -.....J
~
-------
TAB_: VIII (CONTINUED
SUMMARY OF TEST COND I TI ONS EXAM I NED WITH COMBUSTOR B
.6P
Run t!'V in .tY"in f63 per cent of
No. Nozzle psia 0:> deq F 1111.:1. Ibm per see inlet pressure
4 3~': B2. I . 1 .3 67 695 .385 4.0
44 1 1 1 68 695 .430 4.9
45 68 715 .540 8.1
46 77 515 .390 2.6
47 68 900 .660 13.8
48 87 680 .625 6.1
rp
msec
10
9
7
14
4
8
*Runs 43-48 were for modified configuration in which one third of the metering holes for the primary and intermediate
cooling slots were blocked off and the diameter of the dilution holes was reduced to 0.25 in.
II.
\1
-.....J
V'1
-------
- -~--
TAB_: x
RESUL"S 0; COMBUST I ON .. :STS ;OR COMBlS"OR B WITH
NOZZLE Bl. 1 AND IICLOSEDII VAR I ABLE-GEOMETRY SETT I NG
Design Nozzle Air/Fuel Ratio = 2:1
Swirler Setting, ~w = .1 in
Secondary-Hole Setting, ~y = .3 in
Estimated Effective Primary-Zone Flow Rate = 18.3 per cent
Pc.3 rpp EINO £IN~ £l(;.o ELlie. Ata I-!c.
7,;~ J"7c..t, rY1/.... t:.
Run mg per mg per mg per mg per
No. ~ deq F Ibm per sec Ibm per hr qm fuel qm fuel qm fuel qm fuel pe r cent per cent IQ
13 67.8 507 .292 18.5 60. I 1. 35 4.11 7.08 2.07 .00 .99 .048 .14
67.9 510 .303 15.9 74.8 1.08 3.84 6.50 2.78. .12 1.08 .076
67.9 518 .313 14.7 78.3 1.03 3.86 6.54 2.76 .16 1. 10 .079
67.9 520 .312 12.2 94.4 .86 4.15 7.27 2.76 .07 1.06 .071
67.9 523 .301 9.0 120.0 .67 3.26 6.14 4.44 .26 1. 15 .128
14 68.2 722 .348 14.5 86.7 .93 6.90 11 .27 2.2 .00 2.04 .051
67.4 721 .390 16.0 87.7 .92 6.98 10.70 2.74 .57 2.20 .118 .15
68.0 726 .347 12.1 103. I .78 6.68 11.23 2.21 .00 2.10 .051
67;9 730 .406 11.3 129.4 .63 6.48 10.76 2.14 .00 2.21 .050
68.2 729 .381 9.7 142.0 .57 5.92 9.87 1.93 .00 1.97 .045
15 67.6 733 .423 20.1 75.8 1.07 6.84 11.33 2.52 I. 13 2.76 .167 . 1 2
67.6 734 .414 18.5 80.4 1. 01 7.08 12.14 2.36 .35 2.51 .088
67.5 736 .431 16.4 94.4 .86 6.71 11. 51 2.30 .29 2.65 .081
67.5 736 .422 13.9 109.0 .74 6.49 10.82 2.18 .20 2.61 .070
67.2 733 .430 12.5 123.7 .65 5.55 9.4 1.93 .19 2.69 .063
67.7 733 .423 8.2 186.0 .44 4.26 7. 12 2.35 .23 2.54 .076
16 67.7 737 .473 22.7 75.0 1.08 6.53 11.22 2.79 . 1 7 3.36 .081 .10
67.7 739 .479 20. I 85.6 .95 6.90 11.68 3. 10 .09 3.45 .081
6].7 737 .479 18.3 94.3 .86 6.51 11.04 3.04 .09 3.54 .079
67.7 736 .479 16.5 104.6 .77 6.34 10.89 3. 11 .16 3.36 .088
67.7 738 .479 12.6 137.3 .59 5.15 9.0 2.34 .32 3.34 .084
67.9 735 .480 9.2 187.6 .43 4.39 6.73 3.01 .66 3.18 .133
.........
0"\
-------
TABLE IX (CONTINUED)
RES J - TS OF COMBUSTION TESTS FOR COMB.STOR B W TH
NOZZLE Bl. 1 AND "CLOSED" VAR I ABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 2:1
Swirler Setting, lsvJ = .1 in
Secondary-Hole Setting, ..Is" = .3 in
Estimated Effective Primary-Zone Flow Rate = 18.3 per cent
~3 -,;;~ #7a. ' t4 E l' NO EINo", £I c.v '~.l b,? 1-1<:..
Mf... 2 ~ Ate
Run mg pe r mg per mg per mg per
No. ~ deq F 1 bm per sec 1bm per hr - qm fuel qm fuel qm f ue 1 qm fuel per cent per cent IQ
17 68.1 699 .542 26.3 74.2 1.09 4.98 8.36 3.34 4.32 .078 .11
68.0 702 .548 24.2 81.6 .99 5.05 8.52 3.59 4.40 .083
67.8 705 .547 22.0 89.6 .90 5.15 8.62 3.32 4.28 .077
67.8 709 .546 \9.5 100.6 .80 4.94 8.39 3.14 4.30 .073
6y.8 711 .538 15.8 122.9 .66 4.36 7.28 2.51 4.15 .058
67.8 711 .538 12. I 160.5 .50 3.51 5.89 1.87 4.08 .043
18 67.8 888 .840 31. 6 95.5 .85 5.09 8.42 5.97 9.06 .138 .16
67.8 892 .836 28.6 105.0 .77 5.05 8.41 5.33 9.06 . I 24
68.0 888 .842 27.9 108.8 .74 4.55 7.32 4.88 9.08 .113
67.8 891 .840 25.2 120.0 .67 4.38 7. II 4.56 9.08 .106
68.1 892 .837 23.3 129.6 .62 4.06 6.63 4.29 9.11 . 100
19 88.8 721 .764 3]. 2 88.1 .92 5.26 9.19 2.50 5.29 .058 .10
87.7 731 .770 30.3 9.1.5 .88 5.17 9.10 2.59 5.43 .060
87.8 729 .771 28.2 98.3 .82 5.14 9.14 2.40 5.39 .056
87.4 728 .779 25.9 108.4 .75 5.10 8.86 2.22 5.40 .051
87.8 729 .771 24.3 114.3 .71 4.65 8.23 1.89 5.28 .044
20 52.8 722 .308 15.9 69.6 1. 16 5.41 8.97 3.07 2.63 .071 ,.17
52.8 733 .322 14.5 80.1 1.01 5.46 9.01 3.37 2.56 .078
53.2 731 .318 11.8 97.4 .86 5.8 9.52 3.33 2.47 .077
53.0 731 .323 10.9 106.7 .76 5.57 9.23 3.23 2.54 .075
52.8 730 .322 9.2 126.6 .64 4.36 7.29 2.47 2.56 .057
-...J
-...J
-------
TAB_: IX (CO~TINUED)
RESULTS OF COMBUSTION TESTS FOR COMBUSTOR B WITH
NOZZLE Bl. 1 AND "CLOSED" VARIABLE-GEOMETRY SETTING
Estimated
Design Nozzle Air/Fuel Ratio = 2:1
Swirler Setting, .J;.w = .1 in
Secondary-Hole Setting, ~Sj = .3 in
Effective Primary-Zone Flow Rate = 18.3
per cent
E I,.;v EJA/iJ/l EI C.D £ I 11<:. AP 1-'1G
Po; , \ ~p
Run r;;~ WIe:\. ~ Z mg per mg per mg per mg per
No. ~ deq F 1 bm per sec Ibm per hr - qm fuel qm fuel qm fue 1 qm fuel per cent I!)er cent IQ.
29 77.9 529 .388 18.8 74.4 1. 09 4.13 7.18 2.62. 2.24 1. 34 .275 .11
77.9 531 .396 16.5 86.6 .93 4.08 7.23 2.79 .06 1. 39 .070
77.9 531 .388 14.9 93.9 .86 4.23 7.38 2.80 .08 1. 30 .073
77.9 531 .388 12.8 108.9 .74 3.98 7.15 2.97 .09 1. 33 .077
78.1 531 .378 12.5 108.9 .74 3.75 6.80 3.45 .10 1. 24 .090
.......
00
-------
Run
No.
21
22
23
24
Pc, 3
£.ili.
68.2
68.1
68.0
67.5
67.5
68.2
67.6
67.8
67.8
67.6
68.0
67.8
68.0
67.8
67.8
67.7
67.6
67.5
67.5
67.6
67.6
7;3
deq F
509
521
523
526
527
689
697
700
705
705
714
728
713
706
702
699
697
697
697
696
697
Mo..
Ibm per see
.308
.301
.301
.304
.299
.398
.395
.373
.394
.394
.429
.406
.414
.429
.430
.416
.479
.491
.491
.479
.491
TA L: X
RESl LTS OF COMBUSTION TESTS FOR COMBUSTOR B WITH
NOZZLE BI.1 AND I I FULL OPEN" VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratia = 2:1
Swirler Setting, ~w = .35 in
Secondary-Hole Setting, ~t = .75 in
Estimated Effective Primary-Zone Flow Rate = 27.7 per cent
,
~
Ibm per hr
19.5
15.7
13.9
I I .2
8.1
20.3
20.0
17.3
16.7
11.6
24.2
20.6
19.2
17.7
14.0
10.4
25.6
23.9
21.4
19.0
13.7
2
56.9
69.2
77.8
97.6
132.9
70.5
71.0
77.7
84.8
122.3
63.8
71.0
77.7
87.3
110.2
144.1
67.4
73.9
82.5
91.0
129.0
,I.. £ Ifoj'
'r~ mg pe~
- qm fuel
.94
.77
.69
.55
.40
.76
.75
.69
.63
.44
.84
.75
.69
.61
.49
.37
.79
.72
.65
.59
.41
2.64
2.47
2.53
2-30
1. 32
5. 11
5.14
5.38
5.69
3.70
5.30
5.22
4.93
4.03
3.30
5.10
4.96
4.93
4.95
3.26
££11)0"
mg per
qm fuel
6.25
6.35
6.38
6.57
5.63
8.85
9.03
9.25
10.35
8.22
8.85
10. 17
9.25
8.96
8.29
7.37
8.90
8.68
8.62
9.05
7.22
E(~o
mg per
qm fuel
14.39
13.89
13.18
15.05
35.97
17.48
3.48
3.80
4.56
12. I
2.57
2.99
3.73
5.03
10.53
13.59
3.50
4.13
4.92
5.86
13.31
;';1#,-
mg per
qm fuel
1. 32
1.66
1.48
1.44
9.97
.04
.02
.02
.03
.47
.05
.00
.02
.03
.29
.53
.04
.00
.03
.06
.47
AP
per cent
.54
.52
.52
.51
.49
1. 14
1.08
1.02
1.03
1.06
1. 36
1.40
1. 34
1. 34
1. 31
1. 75
1.82
1.84
1. 76
1.82
1- 1..:-
per cent
.IQ.
.26
.460
.481
.447
.486
1.786
.410
.083
.091
.108
.327
.17
.064
.069
.088
.119
.272
.366
.085
.096
.117
.141
.354
.17
.16
-....J
'!>
-------
TABLE x (CONTINUED)
R~S.LTS OF COMBUSTION TESTS FOR COM 3. STO ~ 3 WIT.
NOZZLE B1.1 AND "FULL OPEN" VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 2:1
Swirler Setting, ~.., -::: .35 in
Secondary-Hole Setting, ~i = .75 in
Estimated Effective Primary-Zone Flow R~te = 27.7 per cent
~~ '1;,3 \ \ 4Y~ ( 1 Nt,) £ 'I,.;4. £ It:c.I £ j.~
-------
TAB LE X (:OITINUED)
~ES J - TS 0; COMBUSTlO' TESTS FOR CO'BJSTOR 8 WITH
NOZZLE 81.1 AND "FULL OPENL1 VARIABLE-GEOMETRY SETn NG
Design Nozzle Air/Fuel Ratio = 2:1
Swirler Setting, -Isv' ': .35 in
Secondary-Hole Setting, .L$' = .75 in
Estimated Effective Primary-Zone Flow Rate = 27.7 per cent
~:& 703 ' " ~f' EI/'IO E£N1J. !Efc:.D ~ IHc.. AP 1-1.
,111 Cl. n1fo.. Z ;(
Run mg pe r mg per mg per mg per Co
No. ~ deq F Ibm per sec Ibm per hr - qm fuel qm fuel qm fuel qm fuel per cent per cent .N
30 67.5 692 .853 31.9 96.3 .55 2.92 6.02 22.47 1.33 5.85 .648 . 13
67.5 694 .847 27.5 111.0 .48 1.97 5.33 34.07 3.06 5.76 1.083
67.5 692 .853 24.0 127.8 .42 1.47 4.60 46.28 6.06 5.66 1.653
67.7 694 .854 19.9 154.7 .35 .98 3.95 58.66 8.51 5.48 2.174
67.5 693 .853 17.5 175.4 .30 .95 3.64 66.46 9.38 5.44 2.437
31 77.6 517 .385 19.2 72.3 .74 6.63 6.90 .45 .71 .203 . 15
77.4 510 .386 16.0 86.5 .62 2.72 6.81 12.01 .93 .70 .367
77.2 508 .398 14.0 102.2 .52 2.14 6.55 18.04 1.72 .72 .583
77.4 507 .398 11.5 124.3 .43 1.75 6.36 22.27 2.78 .75 .782
77.6 506 .387 11.3 123. 1 .43 1.99 6.50 19. 18 2.19 .71 .654
00
-------
TABLE XI
RESULTS OF COMBUSTION TESTS FOR COMBUSTOR B WITH
NOZZLE B2.1 AND "CLOSED'I VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 4:1
Swi r1er Setting, .Is...; = .1 in
Secondary-Ho1 e Sett i ng ,~t = .3 in
Estimated Effective Primary-Zone Flow Rate = 21.8 per cent
Po~ . .. £. i ,\10 ;;.1 tJo. £1C<) £1 He. AP i - '2c.
Run ~3 PtIA. M l.
-------
TABL~ XI (COHINJ~))
RESULTS OF COMBUSTION TESTS FOR COMBUSTOR B WITH
NOZZLE B2. I AND "CLOSED" V AR I ABLE-GEOMETRY SETT I NG
Design Nozzle Air/Fuel Ra t i a = 4: I
Swirler Setting, ~w = . I in
Secondary-Hole Setting, ~s1 = .3 in
Estimated Effective Primary-Zone Flow Rat~ = 21.8 per cent
\ q;,P e1/Vv £j.-'fIkJ" £ [cZ I-~
Poe, "1':\ ;Y, 2
Run Q. """'-f... mg per mg per mg per mg per '" . ~
No. lli2 deq F Ibm per sec Ibm per hr qm fuel qm fuel qm f ue 1 qm fuel per cent pe"r cent. I9.
41 67.9 889 .845 31.0 98.2 .69 5.65 9.61 4.22 10.46 .098
68.2 887 .838 29 0 104.1 .65 5.22 8.50 3.96 10.85 .092
68.2 889 .840 27.6 109.5 .62 5.03 8.24 3.63 10.41 .084
68.1 886 .842 24.5 123.6 .55 4.38 7.31 3.85 11.01 .089
67.9 895 .838 22.9 131.9 .51 3.44 5.69 6.93 10.90 .161 .17
42 87.9 707 .773 38.9 71 .5 .95 5.86 10.59 1.89 .00 4.57 .044
87.9 706 .780 32.0 87.8 .77 5.70 9.86 1. 63 .00 4.80 .038
88.1 705 .792 29.0 98.2 .69 5.03 8.82 I. 34 1.81 4.80 .204
87.9 699 .776 23.3 119.9 .57 3.75 6.14 5.49 .86 4.75 .210 .10
87.9 701 .789 21.1 134.5 .50 2.38 4.84 19.37 6.59 4.59 1.078
0.:>
v.J
-------
TABLE XII
RESULTS OF COMBUSTION TESTS FO ~ COM 3. STO ~ 3 WIT,
NOZZLE B2.1 AND "FULL OPEN" VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 4:1
Swirler Setting,~w = .35 in
Secondary-Hole Setting,~~::.75 in
Estimated Effective Primary-Zone Fl0 Rate = 30.0 per cent
~:l .. \ ~p £1' No If 1/11D;t G.I~ E jilt:. AP 1-1G.
Run '~3 fYlw.. rr7j.. 2 mg per mg per mg per mg per
~ ~ deq F lbm per sec Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent. per cent IQ
32 67.8 697 .385 18.7 73.9 .67 5.66 9.52 3.91 .06 .98 .096 .18
67.6 697 .384 15.9 87.2 .57 6.02 10.50 6.73 .07 1.02 .163
67.8 697 .385 13.3 104.2 .47 4.25 8.68 10.87 .27 .98 .278
67.6 697 .384 10.7 129.3 .38 2.97 7.24 24.30 4.95 .99 1.036
67.8 700 .395 10.3 138.1 .36 .89 3.31 33.05 20.28 1.00 2.703
33 68.3 701 .432 20.4 76.1 .65 5.58 9.79 3.50 .05 1. 20 .086 .18
67.6 703 .444 18.3 87.4 .56 3.39 6.60 8.97 .43 1. 31 .249
68.0 703 .431 12.8 1 21 . 1 .41 2.72 6.78 18.40 1. 65 1. 22 .584
67.9 704 .430 12.7 122.3 .40 L85 5.48 30.49 9.36 1. 26 1.602
34 68.1 692 .563 29.2 69.5 .71 3.72 6.65 4.56 1. 71 2.15 .269 .16
68.0 692 .61"3 29.1 75.8 .65 3.42 5.54 6.31 2.57 2.17 .391
35 77.8 515 .385 18.3 76.0 .65 3.27 7.21 12.56 .72 .67 .361 .23
77.2 525 .382 12.7 108.3 .46 2.60 7.46 17.84 1.99 .67 .604
77.3 520 .383 12.8 107.7 .46 1.69 6.21 29.82 3.63 .64 1.039
77.6 523 .395 9.0 157.5 .31 .98 3.52 ;' 76.6 60.17 .60 > 7.523
77.8 524 .384 8.0 171 .7 .29 .97 3.29 783.5 73 .I. 6 .61 ? 8.953
36 87.7 702 .779 31.1 90.2 .55 4.62 8.39 5.64 .72 2.59 .200 .15
87.5 702 .778 30.3 92.5 .53 4.35 8.16 6.32 .77 2.58 .220
87.7 703 .779 26.7 105.0 .47 3.51 7.40 11. 16 2.06 2.52 .456
87.8 702 .780 25.9 108.5 .46 4.30 8.34 9.41 1. 36 2.49 .349
87.1 705 .776 23.6 118.4 .42 2.32 6.06 21.68 5.62 2.58 1.040
00
+-
-------
"ABLE XIII
~::SUL"S OF eOMBUS" m TESTS FOR MODIFIED em BUS' 'OR B WITH
NOZZLE B2.1 AND IICLOSED" VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Rat i a = 4: I
Swirler Setting, ..tsw = .1 in
Secondary-Hole Setting, ~y= .3 in
Estimated Effective Primary-Zone Flow Rate = 29.6 per cent
" ' if, £ Z"'o E I,.;o", ££<:0 £ L~c. AP
Run Po3 -1;3 r1? A. ~~ r. mg per mg per mg pe r mg per 1-1,
No. .eili ' deq F 1 bm per see Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent per cent IQ
43 67.4 691 .385 32.6 42.5 I. 18 5.74 10.01 .46 .98 4.03 . 105 .19
67.4 680 .387 30.4 45.8 1.09 4.84 8.35 .54 1.08 3.97 .116
67.4 697 .384 27.0 51.3 .98 4.54 7.46 .56 .13 3.99 .025 .19
67.0 700 .382 23.6 58.4 .86 3.94 6.51 .80 1.46 4.05 .158
67.2 700 .383 18.9 73.0 .68 3.45 5.75 I. 79 .13 3.89 .054
I
I 44 67.6 694 .430 26.5 58.3 .86 3.93 6.50 .97 4.91 .023
67.8 694 .430 21.8 71.0 .70 3.05 5.25 5.14 4.90 .119 .22
67.6 694 .430 21. 5 71.9 .70 2.94 5.32 6.41 4.91 .149
45 67.9 725 .535 41.9 45.9 1.09 4.18 7.67 I. 13 7.82 .026 .21
67.4 695 .547 33.8 58.3 .86 3.44 5.84 1.49 8.19 .035 .22
67. I 696 .546 30.8 63.8 .78 2.95 5.35 2.88 8.56 .067
II 67.8 741 .538 29.6 65.3 .77 3.43 5.90 3.97 7.85 .092
46 77.4 510 .380 26.8 51.1 .98 2.64 6.12 .96 . I 3 2.50 .034 .15
I 77.4 520 .395 24.5 58.1 .86 3.30 5.63 1.48 4.04 2.63 .420
I 77.4 519 .396 18.4 77.4 .65 1.05 4.11 28.17 11.43 2.56 1.745
, 77.4 513 .397 18.1 78.9 .63 I. 65 4.31 18.20 .90 2.67 .508
77.4 515 .384 14.4 96.2 .52 .48 3.01 > 46.5 33.94 2.51 > 4. 343
I 47 67.9 895 .657 42.7 55.4 .90 4.32 7.70 I. 58 13.41 .037 .25
67.7 897 .656 36.3 65.0 .77 3.69 6.28 2.17 13.59 .050
67.5 898 .666 31. 6 75.8 .66 2.74 4.87 4.30 14.21 .100
67.4 897 .665 29.9 80.0 .63 2.68 4.76 5.79 14.10 .134 ex>
V1
-------
TABLE XIII (CONTINUED)
RESl LTS OF COMBUSTION TESTS FOR MOD IF I ~D COHillS"OR B WITH
NOZZLE B2. 1 AND "CLOSED" VAR I ABLE-GEOMETRY SETT I NG
Design Nozzle Air Fuel Ratio = 4:1
Swirler Setting, ~w = .1 in
Secondary-Hal e Sett i ng, .t;y = .3 in
Estimated Effective Primary-Zone Flow R?te = 29.6 per cent
~ El {I/o ;;11.;0 ELce; e fife. ~p 1-1(;.
Run ~~ 7;;~ rvl.:1,. ~k 2 mg pe r mg pe r- mg per mg per
No. ~ deq F Ibm per see Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent per cent IQ
48 87.4 682 .618 36.4 61.1 .82 3.86 6.56 1. 50 5.92 .035 .21
87. 1 682 .626 33.8 66.6 .75 3.50 5.95 2.55 6.05 .059
87.0 682 .625 30.2 74.5 .67 2.81 5.27 11.37 6.22 .264
86.9 680 .629 27.7 81.6 .61 1.11 3.93 >39.5 6.27 >.916
ex>
()'\
-------
TABLE XIV
S JMMARY OF . "ES" CO, ) T IONS EXAM I NED WI'"H :OMBUS"O, M:
tJ,p
Run .1st per cent of
No. ~w in in ~~ psi a ~i deq F Mc1. 1 bm per see inlet pressure off msec
49 .2 .4 24 700 .920 6.5 19
50 900 .315 .9 51
51 900 .840 6.6 18
52 1100 .790 6.7 17
53 1185 .775 6.9 17
54 59 895 .500 .4 80
55 1 870 .910 1.2 45
56 900 1 .310 2.5 30
60 .3 .7 40 900 .435 .6 55
61 900 1.145 3.7 20
62 1100 1.070 3.7 19
63 1150 1.055 3.6 20
64 59 905 .53 .3 67
65 1 900 .955 1.1 37
66 895 1.390 2.4 25
68 88 890 .655 .2 81 00
--..J
;':A 11 tests were performed with Nozzle A2.1.
-------
. "ABLE XV
RES. L"'S OF COMBUSTION TESTS FOR COMBUSTOR A WITH
NOZZLE A2.1 AND I'CLOSED" VAR I ABLE-GEOMETRY SETT I NG
..
Design Nozzle Air/Fuel Ratio = 4:1
Swirler Setting. ~w =.2 in
Secondary-Hole Setting, ~~ = .4 in
Estimated Effective Primary-Zone F1 Rate = 11.8 per cent
a "'0 E.LlliOA cl'eo E /;'c. I1P /-1<:-
' ' ? rip
~~ 7';,; ~a. n1
Run -f... mg pe r mg per mg per mg per
No. ~ deq F Ibm per see Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent per c:.ent lQ.
49 24.1 701 .924 45.9 72.5 1.89 3.95 6.65 10.36 6.45 .240 .08
24. I 698 .920 41.5 79.8 1. 71 4.01 6.93 10.46 6.45 .243
50 23.9 899 .318 19.3 59.4 2.30 7.00 11.50 2.57 6.93 .060 .13
23.8 901 .317 17.4 65.6 2.09 7.30 12.47 2.77 6.96 .064
23.8 900 .317 14.6 78. I 1. 75 6.87 11.04 2.90 6.90 .067
23.8 900 .317 11.4 100.2 I. 37 7.33 11.72 3.13 6.89 .072
23.8 899 .317 8.6 132. I 1. 04 7.72 12.25 3.60 6.86 .083
51 23.6 899 .837 39.1 77.0 1. 78 5.98 10.15 7.76 6.69 . 180 .10
23.5 902 .841 34.9 86.8 1. 58 5.81 10.03 8.31 6.67 .193
23.6 899 .841 32.6 92.8 1.47 5.83 9.83 8.70 6.58 .202
23.5 898 .842 31. 2 97. I 1.41 5.69 9.65 9.38 6.71 .218
23.5 901 .841 27.5 110.3 1. 24 5.76 9.19 9.35 6.72 .217
23.6 901 .841 24.3 124.7 I. 10 5.46 8.98 8.99 6.55 .208
23.5 900 .842 22.7 133.4 1.02 4.73 8. 11 8.83 6.60 .205
23.6 900 .841 19.2 157.4 .87 4.26 7.04 10.25 6.51 .238
I
52 23.7 1098 .787 39.2 72.4 1.73 8.73 14.67 4.82 .60 6.45 .169 .14
23.7 1099 .786 35.4 80.0 I. 57 8.55 14.27 4.85 .32 6.75 .143
23.6 1098 .788 31.8 89.1 1. 41 8.76 14.58 5.48 .14 6.86 .141
23.6 1101 .787 29.1 97.3 1. 29 8.65 14.35 5.41 . 10 6.80 .135
23.7 1097 .790 25.9 109.9 1. 14 8.61 13.91 5.25 .05 6.72 .125
23.6 1101 .787 20.2 139.9 .90 7.59 11.86 4.77 .00 6.75 .111
23.6 1097 .788 18. I 156.7 .80 6.69 10.76 4.87 .00 6.70 . II 3
00
00
-------
.- --- ----- -- -------------------
TABLE XV (CQt'"INUED)
~ESJ_'.S OF COMBUSTION TESTS FOR COMffiS'"O~ A W T.
NOZZLE A2.1 AND I'CLOSED" VARIABLE-GEOMETRY SETTING
Design Nozzle Air Fuel Ratio = 4:1
S w i r 1 e r S e tt i n 9 . ,~w = . 2 i n
Secondary-Hole Setting, ~1 = .4 in I 1 . 8 pe r ce n t
Estimated Effective Primary-Zone Flow Rate =
~J ~f" t4 £ IIIIo EI NOJ{ E leo PI AP /-tzc.
"1:;; M l _. He.
Run ~ mg pe r mg per mg pe r mg per
No. ~ deq F Ibm per sec 1 bm pe r h r qm fuel qm fuel qm fuel qm fuel per cent pe r cent IQ
53 23.7 1184 .769 40.9 67.6 1.86 9.94 17.42 3.71 .28 6.72 .113 . 16
23.8 1182 .771 36.1 76.8 1.63 10.31 17.67 3.99 .50 6.64 .140
23.5 1182 .787 32.5 87.3 1.44 9.96 16.81 4.52 .02 7.28 .107
23.6 1181 .768 27.9 99.1 1. 27 10.36 17.48 4.64 .00 6.78 .108
23.6 1182 .775 25.6 108.9 1.15 8.98 14.82 4.35 .00 6.99 .101
23.6 1185 .768 24.3 113.6 1. 11 9.13 14.91 3.98 .eo 6.87 .092
23.6 1184 .773 20.3 137.3 .92 8.30 13.60 3.87 .00 6.94 .090
23.8 1183 .770 17.5 157.9 .80 8.06 13. 1 2 3.68 .eo 6.61 .085
23.6 1182 .768 12.9 214.5 .59 6.24 9.92 4.16 .00 6.68 .097
23.7 1185 .769 10.8 256.6 .49 5.12 8.38 4.73 .00 6.61 .110
54 59.5 896 .503 23.6 76.7 1. 78 10.78 17.88 1.65 .37 .038 .14
58.3 898 .498 21.3 84.0 1.63 11.08 18.07 1.81 .34 .042
58.2 892 .498 18.1 99.3 1. 38 11.41 18.30 2. 13 .39 .049
58.7 896 .500 15.3 117.4 1. 1 7 12.01 18.98 2.75 .37 .064
58.7 893 ~500 14.5 124.3 1. 10 10.77 17.70 3.03 .37 .070
59.0 896 .501 11.9 152.1 .90 12.36 21.39 4.59 .33 .106
I' 59.0 893 .501 8.7 208.0 .66 13.63 22.56 4.85 .32 . 11 2
55 59.0 873 .906 28.9 113.0 1. 21 10.62 17.19 2.86 1. 19 .066 .16
59.1 872 .910 27.0 121. 5 1. 1 3 10.77 17.88 3.19 1. 22 .074
59.3 870 .910 24.5 133~ 8 1.02 10.74 17.54 3.39 1. 20 .079
59.1 871 .908 22.6 144.9 .94 10.87 17.59 3.38 1. 25 .078
59.3 872 .909 19.9 164.1 .83 10.59 17.29 3.83 1. 22 .089
59.3 873 .906 17.2 189.2 .72 9.84 15.69 4.96 1. 19 .115
59.2 873 .908 15.2 214.3 .64 8.69 14.69 5.62 1. 18 .130 OJ
'-D
59.4 869 .911 13.7 238.8 .57 8..94 14.84 5.79 1. 16 .134
59.2 871 .909 10.7 305.0 .45 6.97 11.66 7.39 1. 14 .171
59.4 869 .911 7.5 434.9 .31 2.89 6.78 34.53 1. 1 2 .801
-------
TABLE XV (CONTINUED)
RESJ_TS OF COMBUSTION TESTS FOR COMBUSTOR A WITH
NOZZLE A2.1 AND "CLOSED" VAR I ABLE-GEOMETRY SETT I NG
Design Nozzle Air Fuel Ratio = 4:1
Swirler Setting, ~vJ = .2 in
Secondary-Hole Setting, ~t = .4 in
Estimated Effective Primary-Zone Flo Rate = 11.8 per cent
Pc, 1 \ \ szS," £[";0 £FNO", £Icu EIH~ At> I-I{c..
7";3 tJ1<::!, ~ '2
Run mg pe r mg per mg per mg per
No. ~ deq F Ibm per sec Ibm per hr - qm fuel qm fuel qm f ue I qm fuel per cent per cent IQ
56 58.8 903 1.316 43.0 110.2 J. 14 9.66 15.70 .97 .17 2.61 .038 . 13
58.9 902 1.315 39.8 118.9 1.06 9.80 15.60 .93 . I 2 2.58 .033
58.9 902 1.315 36.9 128.3 .98 9.90 15.80 .75 . 10 2.58 .027
58.6 903 1. 311 33.9 139.3 .90 9.44 15.36 .75 .10 2.57 .027
58.9 903 1.302 32.1 146.0 .86 8.83 14.24 .78 .12 2.52 .030
58.7 898 1.304 22.1 212.3 .59 7.06 11.51 2.47 .97 2.47 .150
58.6 896 1. 311 20.9 226.2 .55 6.59 10.82 2.41 .17 2.48 .072
58.3 899 1.309 18.6 253.7 .50 6.33 10.51 2.71 .07 2.54 .069
58.5 898 1. 311 17.7 266.6 .47 6.09 10.19 3.10 .00 2.47 .072
58.3 899 1.308 13.5 350.1 .36 4.00 7.52 13.90 .59 2.49 .379
58.7 897 1.307 10.8 437.1 .29 J. 81 5.01 47. 40 9.98 2.41 2.053
\.D
o
-------
TABLE XVI
RESU - TS 0 ~ CO~BUSTION TESTS FO~ COMBUSTOR A W '"f
NOZZLE A2. I AND "PART OPEN" VARIABLE-GEOMETRY SETTING
Design Nozzle Air Fuel Ratio = 4:1
Swirler Setting, 4\01 =.3 in
Secondary-Hole Setting, Is" = .7 in
Estimated Effective Primary-Zone Flow Rate = 14.8 per cent
~z '-y:; ~ ' ' rpp £ I No £I;;o;; £I<':'D E [He. Af> j-Ife,
M WI L
Run Q. .~.... mg pe r mg per mg per mg per
No. ~ deq F Ibm per sec 1 bm per hr - qm fuel qm fuel qm fuel qm fuel per f:.ent per c.ent lQ.
60 39.5 900 .424 18.8 81.4 1. 23 11.09 17.66 .72 . 10 .54 .026 . II
39.4 899 .436 16.7 93.6 1. 07 12.53 19.67 .73 .21 .57 .037
39.5 897 .438 14.0 113.1 .88 9.45 14.85 .77 .21 .54 .038
39.5 897 .438 12.2 129.8 .77 8.26 13.08 .88 .21 .58 .040
39.8 898 .437 8.1 193.0 .52 6.83 11.08 1. 31 .24 .51 .053
61 39.5 899 1.139 48.3 84.9 1. 18 12.54 20.19 1. 74 .18 3.75 .058 .10
39.5 899 1.141 41.0 100.2 1. 00 10.06 16.06 1.76 .12 3.72 .052
39.2 899 1.141 36. I 113.7 .88 8.31 13.65 1.66 .09 3.81 .047
39.7 897 1.147 34.7 118.8 .84 7.32 11 .79 1.50 .07 3.72 .042
39.8 894 1.152 30.2 137.4 .73 6.59 10.54 1.74 .08 3.68 .048
39.6 897 1.147 26.5 155.7 .64 6.00 9.70 2.12 .09 3.70 .057
I 62 40.0 1105 1.074 47.3 81.7 1. 22 15.41 24.94 1. 04 .15 3.74 .038 .06
40.0 1099 1.072 37.6 102.7 .97 14.48 23.30 1.25 .13 3.64 .041
39.6 1099 1.071 32.4 118.8 .84 13.39 21.30 1. 39 . II 3.76 .043
39.8 1097 1.070 28.8 133.9 .75 10.33 16.17 1. 56 .12 3.63 .048
39.7 1099 1.072 23.1 166.8 .60 7.73 11.99 1. 78 .14 3.58 .055
39.4 1096 1.069 17.7 216.9 .46 6.09 9.68 2.63 .07 3.63 .067
63 39.9 1150 1.057 35.0 108.7 .92 12.60 20.01 1.80 .61 3.72 .10 .26
40.2 1150 1.061 31.2 122.6 .82 10.62 16.48 1. 61 .22 3.63 .058
40.0 1147 1.063 28.4 134.8 .74 9.42 14.65 .98 .23 3.42 .044
39.8 1153 1.055 22.2 171.0 .58 7.48 11.46 .66 .29 3.50 .043
1154 1.051 18.0 210.4 .48 6.35 9.90 1.02 .32 3.53 .054 \.0
39.5
39.4 1149 1.051 16.4 231.3 .43 5.89 9.58 1.68 .42 3.54 .079
-------
TABL: XVI (CONTI NUED)
RESU -'.S OF COMBUST 0' TESTS FOR COMBl S' 'OR A W ".
NOZZLE A2.1 AND "PART OPEN'~ VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 4:1
Swirler Setting, ..LsvJ = .3 in
Secondary-Hole Setting, .4'1 = .7 in
Estimated Effective Primary-Zone Flow Rate = 14.8 per cent
Pc'J EIIJD £. r NO'lL £~o EZ;.;c:.. l:>.P i -?c:.
'To"! 1')1
-------
TA3L: XVI (CONTINUED)
RESULTS OF COMBUSTION TESTS FOR COMBUSTOR A WITH
NOZZLE A2.1 AND "PART OPEN" VARIABLE-GEOMETRY SETTING
Design Nozzle Air/Fuel Ratio = 4:1'
Sw i r 1 e r S e tt i ng, "tsw = . 3 in
Estimated Secondary-Hole Setting, 1sy = .7 in
Effective Primary-Zone Flow Rate = 14.8 per cent
Pc, 3 \ . r4 EtNO E 1"'0" EZco IE I He. ~p i-~G.
I;,~ tt1~ fYI, ?
Run k mg pe r mg per mg per mg per
! fu2.:. £.ill. deq F 1 bm per sec Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent per cent IQ.
68 87.2 890 .654 36.6 64.3 1. 56 12.83 22.27 .50 .13 .22 .024 . 1 3
88.0 890 .657 26.6 88.9 1. 1 3 10.98 18.98 .61 .04 .21 .017
87.5 891 .655 22.5 104.7 .95 11.49 20.14 .66 .02 .24 .018
86.7 889 .652 18.9 124.5 .80 12.73 22.30 .85 .02 .24 .021
87.7 887 .656 14.3 165.6 .60 13.79 23.80 1. 13 .03 .24 .029
87.9 887 .657 11.4 208.3 .48 13.22 23.36 1.52 .05 .23 .040
87.5 886 .656 7.5 314.8 .32 11. 11 19.04 3.51 . 14 .25 .095
87.9 888 .657 7.3 324.4 .31 11.79 20.66 4.40 . 19 .23 .120
\D
, v.J
-------
'"ABLE XVII
SUM 1ARY OF TEST COND IT IONS ::XAM I N ED W '"H 100 F ED CO 1 ~l STOR M:
Nozzle Ai r
Pressure
Drop, APND;J
Run Modification Nozzle per cent of
No. No . ':,,': Comb i na t i on~':~',,': ..e "-'4 in 1'00 psia 1:.'~ deq F ~ 1 bm/sec inlet pressure -'l~ msec
.
71 M . 3 29 880, .595 23.8 18
72 P ~ 880 .605 25.3 17
73 P 52 890 .85 14.1 25
74 M 1 885 .85 14.3 25
75 M+P 905 .855 13.9 24
76 M 56 900 1. 11 21. 0 19
77 p ! 900 1. 11 21..2 18
78 M .6 32 905 .63 20.9 18
79 P 1 1 905 .63 21.1 18
80 M 35 915 .755 29.5 14
81 P ~ 915 .755 29.5 14
82 2 M .4 28 910 .575 12.4 17
83 1 P 1 1 910 .58 1-2.3 17
84 M+P 910 .58 12.3 17
85 M+P 30 905 .785 19.2 13
-::All tests conducted with Nozzle A2.2 and secondary-hole se tt i ng ( Lsy ) of O. 6 in.
~':;':S ee Figure 31.
i':'i':-;.'\'M - Fuel through main airblast portion of nozzle only.
P - Fuel through pilot only.
M+P - Fuel through both pilot and main.
\.D
~
-------
TABLE XV III
CALCULATED NOZZLE AND SWIRLER AIR
FLOWS FOR MODIFIED COMBUSTOR A
Swirler \ '
Setting,~'::-;': m,,# f11w YI1pJ elf
Modification No. ~': .L3"" in per cent per cent per cent
0.3 9.4 2.8 21.3
0.6 9.4 5.8 23.5
2 0.4 8.6 9.8 . 2-6.4
~':See Fi gure 31.
~~~In all cases, the secondary-hole setting ( ~1 ) was 0.6 in.
95
-------
TABLE XIX
RESULTS OF COMBUSTION TESTS FOR MODIFICATION NO. ] OF em Bl S'.O ~ A W ".
NOZZLE A2.2 AND "CLOSED" SWIRLER SETTING
Design Nozz]e Air/Fue] Ratio = 4:]
Swir]er Setting,,/:>'/'J =.3 in
Secondary-Hole Setting, ~5i = .6 in
Estimated Effective Primary-Zone F]ow Rate = 2].3 per cent
~") "1;3 ' n1.+", 2 rpp £ l/IJo £ ItJo'/l. £ I c.cJ Ellie. APNDc 1-70:.
m
Run "l mg per mg per mg per mg per
No. ~ deq F Ibm per sec Ibm per hr qm f ue] qm fuel qm fuel qm fuel per cent Rer cent
7] 28.7 880 .599 27.3 79.0 .88 4.97 8.38 I. 78 24.4] .04]
28.7 880 .605 24.4 89.2 .78 3.92 6.44 1.96 25.43 .045
29. ] 880 .587 21.3 99.3 .70 2.91 4.93 2.03 22.67 .047
29. ] 880 .587 ]9.0 ]] ] .2 .63 I. 74 2.97 4.23 22.67 .098
72 28.9 880 .608 24.5 89.2 .78 4.48 7.45 2.27 25.57 .053
28.7 880 .605 20.5 ]06.] .65 2.44 4.25 4.50 25.75 . ]04
28.9 880 .603 ] 7.9 ] 2].4 .57 .96 1.94 ] 6.3] 24.52 .378
73 51.7 889 .85] 27.] ]] 3.] .6] 4.49 7.24 I. ] 0 ]4.5] .026
51. 7 888 .848 26.6 ] ]4.9 .60 3. ] 2 5.24 1.90 ] 3.9] .044
51.6 890 .85] 24.6 ]24.4 .56 2.34 4.08 2.79 ]4.]4 .065
52.0 889 .850 23.5 ]30.5 .53 2.]8 3.88 3.8] ]4.03 .088
! 74 51. 5 885 .85] 34.6 88.6 .78 8.44 ]3.50 .43 ]4.57 .0]0
51.6 882 .854 29.6 ]03.7 .67 4.77 8.]4 .56 ]4.32 .0] 3
51.6 884 .848 28.6 ]06.7 .65 2.68 4.53 3. ] 2 ]4.]4 .072
75 52.0 904 .844 39.8 76.4 .9] ] 2.9] 20.53 .97 ]3.63 .023
52.0 905 .860 36.0 86.0 .8] 9.28 ]4.64 1.09 ]4.42 .025
52.0 905 .850 28.] ]09.0 .64 5.0] 8.2] I. 38 ] 3.82 .032
51.9 904 .856 25.6 ]20.2 .58 2. ] 3 3.62 ] .64 ]4.04 .038
51.7 903 .860 23.3 ]33.0 .52 1.73 3.08 2.20 ]3.90 .05]
51.7 903 .860 22.5 ]37.4 .5] 1.43 2.74 2.54 ] 3.90 .059 U)
51.7 903 .860 ]8.8 ]64.9 .42 I. ] 0 2.26 9.94 ]3.90 .230 Q"\
5] . 7 903 .860 ] 7.9 ]72.6 .40 .83 2. ] 2 ]5.76 ] 3.90 .366
-------
TABLE XIX (CONTINUED)
RESl _TS O~ COMBUSTION TESTS FOR MODIFICATION NO. OF CO '1 3l S' .0 ~ A W .'H
NOZZLE A2.2 AND "CLOSED" SWIRLER SETTING
Design Nozzle Air/Fuel Ratio = 4:1
Swirler Setting, /.sw =.3 in
Secondary-Hole Setting, ~y =.6 in
Estimated Effective Primary-lone Flow Rate = 21.3 per cent
EItJO ~ J.~o £ Leo -1 ~r:vc ;= I - 1<:-
~3 ~3 W\Q. . 2 ~ i:. lie.
Run t\I,\~ "" J(
mg per mg per mg per mg pe r
No. .E.ili. deq F Ibm per sec Ibm per hr qm fuel qm fuel qm fuel qm fuel per cent r>er cent
76 56.0 906 1. III 50.6 79.0 .88 10.8 17.3 1. 159 21.1 .027
56.4 903 1.108 44.7 89.3 .78 8.69 13.9 l. 177 20.7 .027
56. 1 902 l. 112 39.9 100.2 .69 6.08 9.56 1.271 21.0 .030
56.4 900 1. 116 36.5 11 0.1 .63 3.91 6.53 1.525 21. 2 .035
56.4 900 1. 116 35.7 112.4 .62 2.70 4.41 2.85 21. 2 .066
77 56.0. 900 1.107 36.9 107.9 .64 6.09 9.68 1.473 20.9 .034
56.0 900 1.113 36.8 109.0 .64 4.44 7. 16 l. 743 21. 6 .040
56.1 901 1. 113 32.6 122.9 .57 2.95 4.82 2.75 21.4 .044
56.4 902 1.109 27.7 144.2 .48 l. 58 3.22 13. 18 21.1 .306
\.0
-....J
-------
. "ABLE XX
RESULTS OF COM 3US" ON TESTS :O~ MODIFICATION NO. OF C01BUSTOR A WITH
NOZZLE A2.2 AND "OPEN" SWIRLER SETTING
Design Nozzle Air/Fuel Ratio = 4: 1
Swirler Setting, ~.., =.6 in
Secondary-Hole Setting, .Isy = .6 in
Estimated Effective Primary-Zone Flow Rate = 23.5 per cent
, ~r E [/110 E[ '() £.1.c::.o £1' He. L\'No~ 1- 2c..
~3 --r;;.!. M(.4. N,.
Run W1-f'\ ~ mg per mgper mg per mg per
~ ~ deq F 1 bm per sec Ibm per hr qm fuel qm fuel qm fuel qm fuel pe r cent per cent
78 31. 7 905 .630 27.9 81.4 .77 4.26 6.80 1. 15 .00 20.7 .027
31.7 904 .630 25.6 88.5 .71 2.96 4.97 1.43 .00 21.7 .033
31. 7 906 .626 22.7 99.2 .64 1.91 3.05 3.05 .00 20.7 .071
31.8 907 .625 20.4 110.1 .57 1. 15 2.38 34.87 .00 20.6 .809
79 31.8 906 .627 33.2 67.9 .93 6.21 10.17 1. 26 . 12 20.7 .041
32.1 907 .633 28.3 80.5 .78 5.73 9.31 1.46 .01 20.8 .035
32.2 908 .630 25. 1 90.4 .70 4.92 7.83 1. 72 .00 21.0 .040
32.0 910 .628 20.5 110 .57 2.22 3.79 3.97 .00 20.9 .092
31.9 906 .631 19.6 115.9 .54 1. 75 3.06 6.66 .00 21. 2 .155
31.9 906 .633 18.0 126.5 .50 .369 1.62 59.8 3.10 21.5 1.684
31.9 906 .633 16.7 136.3 .46 .291 1.42 :> 66. 4 22.90 21. 5 > 3.727
31.9 906 .633 16.2 140.4 .45 .293 1. 12 768.3 51.60 21.5 76.512
t 80 34.7 913 .750 41.9 64.4 .98 5.82 9.76 1. 65 .20 29.1 .057
34.6 914 .755 38.2 71.1 .89 5.07 8..46 1. 71 .11 29.5 .050
34.6 915 .753 33.7 80.5 .78 4.05 6.72 1. 69 .00 29.2 .039
34.7 915 .759 32.5 84.0 .75 3.43 5.73 1.80 .00 29.7 .042
34.7 917 .760 29.6 92.3 .68 2.30 4.15 2.48 .00 29.7 .058
34.7 919 .753 25.7 105.3 .60 0.92 1.94 18.69 .90 29.5 .520
\.D
ex>
-------
TA~L: xx (CONTINUED)
~ESU_TS 0; COMBJST ON TESTS FOR MODIFICATION NO.1 OF COM~lSTOR A W "1
NOZZLE A2.2 AND "OPEN" SWIRLER SETTING
Design Nozzle Air/Fuel Ratio = 4:1
Sw i r 1 e r Se tt i ng , Psw = .6 in
Secondary-Hole Setting, 1~' = .6 in
Estimated Effective Primary-Zone Flow Ra,te = 23.5 per cent
~3 "7;,3 mA. . ~ £IN>:> £lNDIl EIe-a E I He.
Run m.,1oo. ~ mg per mg per mg per mg per
No. ~ deq F Ibm per sec 1 bm pe r hr - qm fuel qm fuel qm fue 1 qm fuel
81 34.6 917 .757 35.7 76.4 .82 5.29 8.84 I. 55 .24
34.7 915 .750 32.7 82.6 .76 4.68 7.70 I. 58 .06
34.5 916 .751 29.7 91.1 .69 3.62 6.14 1.95 .00
34.6 915 .758 27.5 99.2 .63 2.70 4.61 2.41 .00
34.7 918 .753 24.9 108.9 .58 1.82 3.23 3.62 .00
34.5 915 .752 24.0 112.6 .56 1. 0 1 1.98 10.75 .00
34.5 915 .752 23.4 115.8 .54 .75 1.61 19.74 .53
34.5 915 .752 23.0 117.4 .54 .64 I. 56 24.14 .65
34.5 915 .752 22.6 119.6 .53 .41 1.42 36.10 1.83
34.5 915 .752 22.4 120.7 .52 .27 I. 35 50.18 3.70
6.f' NQ~ j-fc.
per cent per cent
29.8 .058
29.1 .043
29.6 .045
29.5 .056
29.1 .084
29.6 .249
29.6 .509
29.6 .622
29.6 I. 013
29.6 1.517
1..0
1..0
-------
--~ . ~ - -- - --.- ~-~- ---------
I
TABLE XXI
RESULTS OF COMBJSTION TESTS FOR MODIFICATION NO. 2 OF COMBUSTOR A
WITH NOZZLE A2.2
Design Nozzle Air/Fuel Ra t i a = 4: 1
Swirler Setting, tsw = .4 in
Estimated Secondary-Hole Setting, 4,/ = .6 in
Effective Primary-Zone Flow Rate = 26.4 per cent
Po3 . , ErNo £1~ Elco E.IHt:. APNoi! I-Ij~
.;;~ MCI,. tY7, ~ ~
Run .f... mg per mg per mg per mg per
No. ~ deq F Ibm per sec 1bm per hr - qm fuel qm fuel qm fuel qm fuel per cent per cent
82 27.8 914 .568 31.1 65.8 .85 4.98 8.38 I. 13 12.27 .026
27.9 912 .582 27.2 77.0 .73 3.71 6.31 1.73 12.70 .040
27.9 911 .580 25.1 83.2 .67 3.31 5.55 3.90 12.54 .091
27.9 911 .580 24.0 86.8 .65 2.73 5.09 7.55 1 2. 54 .175
83 28.0 909 .577 25.8 80.5 .70 5.23 8.53 1. 38 12.44 .032
28.0 910 .581 23.6 88.5 .63 4.58 7.67 1.99 12.46 .046
28.0 909 .573 21.0 98.3 .57 3.65 6.06 3.93 12.15 .091
27.8 909 .586 17.9 118.2 .47 1. 11 2.69 35.91 12.78 .833
27.8 909 .586 17.4 121. 5 .46 .79 2.59 49.12 12.78 1.140
27.8 909 .586 16.4 128.3 .44 .40 1.85 >62.0 12.78 ~1.438
84 27.9 908 .578 34.5 60.3 .93 6.53 11.28 .98 12.15 .023
28.0 908 .581 30.3 69.0 .81 5.00 8.33 1.01 12.29 .023
27.8 908 .579 26.5 78.7 .71 3.96 6.70 1.04 12.58 .024
27.8 906 .578 25.6 81.4 .69 3.80 6.08 I. 07 12.38 .025
27.9 907 .583 23.8 88.2 .64 3.14 5.23 1. 33 12.54 .031
27.8 905 .585 19.4 108.7 .52 1.87 3.13 6.94 12.60 . 161
27.8 905 .585 18.7 112.6 .50 I. 53 2.88 10.32 12.60 .239
27.8 905 .585 18.4 114.5 .49 1.48 2.82 11.92 12.60 .277
27.8 905 .585 18.3 115.0 .49 1. 20 2.61 23.30 12.60 .541
85 30.1 906 .781 43.6 64.5 .87 4.47 7.79 .70 18.75 .016
30.0 907 .784 38.7 72.8 .77 4.01 6.79 .89 19.49 .021
30.0 904 .790 33.9 84.0 .67 3.21 5.60 1. 19 19.45 .028
30.0 905 .780 29.1 96.6 .58 2.22 3.95 I. 70 19.19 .039
30.1 905 .785 26.4 107.1 .52 1. 39 2.57 7.05 19.05 .163 a
a
-------
Parameter
Air-flow rate
Fuel-flow rate
Inlet pressure
Pressure difference
across combustor
Inlet temperature
Temperaiure distri-
bution at exit of
combustor
Temperature of
combustor liner
Chemical composition
of exhaust products
TABLE XX II
HOT-TEST MEASUREMENTS
Instrument
Orifice plate
Flow meter
Static pressure tap and
pressure gauge
Static pressure taps and
manometer
Thermocouple
High-temperature probes with
two-dimensional traversing
mechanism
Temperature sensitive paints
Two fixed rakes with
continuous analysis of
sample
101
-------
102
TABLE XXIII
RADIAL COORDINATES OF EXIT TEMPERATURE TRAVERSE
FOR EACH THERMOCOUPLE PROBE
Radial Coordinate, in
Combustor A
Combustor B
0.76
1.84
2.39
2.84
3.22
0.44
1.06
]. 38
1. 63
-------
103
TABLE XXIV
SPECIFICATIONS OF THE EMISSION INSTRUMENTS
Pollutant Instrument
Species Method Model Ranqes Accuracy
N i tr i c Chemiluminescent TECO Mode I 2.5, 10, 25, 100, .:!: 1%
Oxide and lOA 250, 1000, 2500, Full-scale
Total NOx 10,000, ppm or better.
Carbon Nondispersive Beckman 0 - 100 ppm .:!: 2% full-scale
Monoxide Infrared (ND I R) Model 315A 0 - 500 ppm .:!: 1% full-scale
Carbon NDJR Beckman 0 - 2% .:!: 1% full-scale
Dioxide Model 315A 0 - 5%
Total Flame loniza- Beckman xl, 5, 10, 50, 5 ppm to 10%
Hydro- tian Detector Model 402 100, 500, 1000, full-scale as
carbons (FID) 5000 CH4
Smoke ARP 1179 Photovolt 0 - 100 i 1/2%
(Ref 22) Model 670
-------
104
TABLE XXV
HOT RIG FLOW CONDITIONS MODELED IN CONDUCTING SPRAY
ANALYSIS TESTS OF NOZZLE A2.2
. . IJ.p
Swirler Setting, &3 ~3 IY}Q". 1?1;t(
I!.s.w (in) (psia) Ldeg F) ( 1 bm pe r sec) ( 1 bm pe r hr) (per cent)
...'~ 24 1180 11 6.8
0.2 0.77
...I...'~
0.3"" 40 1150 1. 05 28 3.5
~': "Closed" corresponding to idle setting.
...I~...t-
"" lip art open" corresponding to 50 per cent power setting.
-------
105
TABLE XXVI
EXPERIMENTALLY DETERMINED DROPLET SIZE
DISTRIBUTION FOR NOZZLE A2.2
Size Grou Per Cent of Per Cent of
(microns Total Drops Tota 1 Fuel Mass
(a) "-sw = 0.2 in
SMD = 54 microns
8-16 31.35 0.8
16-32 25.84 5.2
32-64 41.98 67.4
64-128 0.64 8.2
128-192 0.13 7.7
192-256 0.07 10.7
(b) Lsw = 0.3 in
SMD = 57 microns
8-16 41.27 1.1
16-32 24.94 5.5
32-64 32.65 57.4
64 - 1 28 0.95 13.3
128-192 0.13 8.7
192 -256 0.04 7.1
320-384 0.01 6.9
-------
106
FIGURES
-------
Q)
::I
4-
E
0'1
.........
0'1
E
W 10
....,
(I)
a:::
c
o
VI
VI
E
w
o
z:
20
o
0.5
0.2
0.4
0.8
0.6
Mlxedness PBrameter, (~)
FIGURE 1 - EFFECTS OF FUEL DISTRIBUTION ON PREDICTED NO EMISSION RATE
FOR REPRESENTATIVE AIRCRAFT GAS TURBINE COMBUSTOR (REF 2)
107
1.0
-------
o
0-
......
to
c::
(1)
u
c: 1.0
(1)
to
>
::J
CT
UJ
(1)
c:
0
N
I
>-
....
to
E
....
c..
0.0
108
BlowOut ( 1,:: 0 ) ,
---
-- -
-- --
- - - - - ~8~
-- --
-- ---- --9%""",,-
-- ~
-- -- -- -.29% ........ ........"
-.. .................."
- - --" ~.S% " '- "" ,.
--""""- " "" "
........ '- ,,"-
,99'9% ' ." '" "-
,-0 ,," "-
---- "."" \ \
~, ~ \ \\
, . \ \, \
" 100% \ \ \ \
\ \ \ \
- - - - -t - - ~ - - f- - - -1- - ,. t- l-
I I J / / /
/ I / / / /
,/ ,/ Low / I / /
,/ /' ./ Power./' / / /
,.,/ // //,/ /
~ r,r ./ ,/
///
..,..,/ /"
,,- /" /'
,., ,/
,.,"- ,,- ,.,
--
-
Fixed Geometry
Geometry
0.1
1.0 10
Combustor Loading Parameter* (~ )-1 x 108
100
.
I ""4.-
-=
(} - /'!} I. 7S"A f) 0.75'. ("7- I' J)
"03 t'1/' 1-12/ exp '1>3 0
.'.
" Typical values plotted in Ibm, Ibf, ft, see, deg R units
FIGURE 2 - COMBUSTION PERFORMANCE MAP FOR FIXED AND VARIABLE-GEOMETRY COMBUSTORS
-------
---.
~
/
/
---
" "'",
.:;:.:,0; ;;
,,~"::.' ,:1.
,. I,.. ,', " ~ . ,
,~:: ~ '.' "'-
' I' ,'"
':~
~i;.:r
. . ~ ,
Ma i n Sw i r I e r
t.
---+
Main Swirler Air
Main Spray
Nozzle Swi rler
JI
/
/
/
/
--
~
,. ,..-
.'
/,.;"<,
Pilot Spray
Pi lot
Fuel
-Ii'>
.
-9>
""'...
."'.."..:-."...
.. .:::.:-
-.
- ---.,
Nozzle Air
-- -,
Fuel Fi 1m ,
,
~
Fi lming Surface
-, .
" .::~,.
" '.",....",
...:,,~,.
'" '...........'..
'~:~"r...".....
.. .-\ .. .. ... ,-..
"..:.~:~.. :.
,.... .-,'"
.." ::'
Ma in'
Fuel
FIGURE 3 - GENERAL CONFIGURATION OF A PILOTED AIRBLAST NOZZLE
o
\D
-------
Compressor
CD
Air Flow
Compressor
CD
Air Flow
Combustor
110
Turbine
Fuel
@
Regenerator
FIGURE 4 - DIAGRAMMATIC REPRESENTATION OF CLASS A AND CLASS B CYCLES
a.
Class A Cycle (Reqenerative)
/combustor
Fuel
4
b.
Class B Cycle (Nonreqenerative)
-------
Radial-lnf1ON
$w i r 1 e r
(variable area)
Sw i r 1 e r -
Flow Throttle
.,y, 5W
I
I
Ai r-B1ast
Fuel Nozz1e
Dome Fi1m-Co01ing
S10t
Secondary Flow
Throttle
---
F10N Streams
ug
Secondary Ho es
(variab1e area)
--
,;,
~ ~¥'PII I I
~'/, ,~~ t I I I I
~~ q:p
I A -
. I J, '- '
V1~lrl- I - -. ''1Jj J~
-""M I L-
Ftl I
-------
112
Sp s. Sa,'1
(.
0 T
c:::=:>
of dJil DL,
WSYl
TC:::>
~ ~ I$y 0
'D c:::::> Dc
}.
Lp L' Ldi /
L
Dimensions, in Combustor A Combustor B
Dc 8.3 4.4
DL 6.8 3.5
Lp 3.4 1.8
L' 3.4 1.8
L
LDiJ 7.8 4.4
I,y 1.2 0.75
W'sy 0.24 0.15
deli 1 0.77 0.47
Sp 0.20 0.10
S. 0.20 0.10
l
Stlil 0.20 0.10
SD 0.10 0.10
'D 2.4 0.60
No. of Secondary Holes 8 8
No. of Di lution Holes 8 4
FIGURE 6 - FINAL DESIGN CONFIGURATIONS
-------
1-
2.75 in
1.75 in
6'9'ees
0.094 in
FIGURE 7 - RADIAL SWIRlER DESIGN
0.4 in
10.9 ;n
Combustor B
Combustor A
r- ...
I
-
-
I
v.J
-------
Fuel Struts
Ai r ... r
1.0 in
Fue1 a.-
Air 1.44 in l
..
Axial
Swi rler
Fuel Line
Centerbody or
Pilot Nozzle
Fuel
Entry
Holes
2.10 in
1.66 in
FIGURE 8 - AIRBLAST NOZZLE CONFIGURATION
4="
-------
1600
IL 1400
en
.,
"'C
(l) 1200
L.
:J
~
ru
L.
Q)
~1000
Q)
f-
L.
Q)
c
:; 800
1600
1L1400
en
a)
"'C
a)
~1200
~
ru
L.
a)
0..
E
~1000
L.
a)
c
-I 800
600
600
~nluminous Flame
Combustor A
40 60
Per Cent Length
80
o
20
100
Combustor B
o
o
20
40 60
Per Cent Length
100
80
FIGURE 9 - ESTIMATED AXIAL DISTRIBUTIONS OF LINER TEMPERATURE
115
-------
----,-
"
rrr------
L',__----
\-
Secondary FION
Throttle
Adjustme~t >-
.Strap
Lock
Screw
Swirler Flow Throttle
Fuel Nozzle
Swirle-r Flow
Throttle Setting
I I
! c(----~'( .
: ., Seconda ry Hole
t -
j I
I '
I _-.J
-..f6 ,
I /J. .,. Secondary Flow
. J-Lsy --r- Thrott 1 e Se tt ; n9
~
FIGURE 10 - VARIABLE-GEOMETRY CONFIGURATION
0'
---- --
-------
Air Blast
Nozz I e
/. -;.... r=-Jll\\\~ ~\\\\\ ~ ~---'-- --=--
~ /: I" h ~ \ \ "- r ~ ~ \ \ " ::::::::::::::: - ,-------
/;~)((~ ~ ~(~~~\\ ~ ~ ~ -::-~ -
III ~ l \' ~//m\\\ ~ -- ----' ,,,'" ~ ~- -
l\ ~ --~ 1) ---" " "-...........:::-----"'::' - ---
-1 \' -'-::-t:) ~~'-~::::::.:::_~ ~ ~-=, --~
-~"--~~~~-~~~-- --- -
--~ ~---~~--~---
,,\~?5 ~'\"~;::~ :---~-----~~- -~-
\,\\' (/-r-~ \,~,,- ~-:::./ ~ ~ -- - -
~"~I J;!J ~?)) ~ %'; - -=-~ :- - - -
~ I ~--..... / /~/ I ( /' ~ ~ ----- -
. - (~ /1. r--__- ~ -
Movable
Sleeve
Liner
Casing
Sw i r I e r
Movable
Boss
Secondary
Holes
D i 1 uti on
Holes
~
--..J
FIGURE 11 - GENERAL FLOW PATTERN OBSERVED IN FLOW VISUALIZATION TESTS
-------
.....
c 10
Q)
u
...
Q)
a..
~>
.~~' 5
~
Q)
.j..J
IU
Q:
~
I.L.
~ 20
o
N
I
>-
...
IU
E
L. 15
a..
Q)
>
.j..J
u
Q)
::: 10
UJ
Nozzles B2.1, B2.2
20
15
118
~,., .I ir1.
0.8
0.6
0.4
0.2
0.0
g~, ;r1.
0.8
0.6
0.4
0.2
0.0
1.2
FIGURE 12 - VARIATION OF EFFECTIVE PRIMARY-ZONE FLOW RATE FOR COMBUSTOR A
o
Nozzles A2. I, A2.2
5
o
o
.4 .6 .8
Secondary-Hole Setting, ~J
.2
1.0
, in
-------
119
Nozzles B1. 1, B1.2
30 i'sw J i".
0.35
0.25
0.15
- 0.05
0.0
~ 20
c
Q)
u
'-
Q)
a..
'f: 10
,
. 'f. Q..
.
Q)
~
ru
0::
::;: 0
0
l.L. Nozzles B2. I, B2.2 RsvJ I it?
Q)
c 30 0.35
o
N 0.25
I
>-
'- 0.15
ru 0.05
E
'- 0.0
CL
Q) 20
>
~
u
Q)
......
......
UJ
10
o
o
.2
.4
.6
.8
Secondary-Hole Setting, ,f~1' in
FIGURE 13 - VARIATION OF EFFECTIVE PRIMARY-ZONE FLOW RATE FOR COMBUSTOR B
-------
a . bJ"' ~ O. 2 1 psi
b. Dr.: 0.65 psi
c.
/~I'" :: 1 .44 ps i
FIGURE 14 - EFFECTS OF NOZZLE AIR PRESSURE DROP ON SPRAY PERFORMANCE
N
a
-------
a.
Nozzle Moved Axially
Downstream (into
Combus tor)
b.
Nozzle at Design
Position
c.
Nozzle Moved Axially
Upstream (out of
Combus tor)
FIGURE 15 - EFFECTS OF AXIAL POSITION OF NOZZLE ON SPRAY PERFORMANCE
N
-------
C1)
;:J
~ 60
E .
01
'-
01 0
E
.
x
C1) 40 L
"'0
C
C
0
V1
V1
E
UJ
0
u 20
o r
I
15 ,
r
C1)
;:J 10 I-
ll--
E
01
'-
01
E
.
x
C1)
"'0
C
C
0
V1
V1
E
UJ
X
0
:z:
5 l
i
!
I- -
o i
.
,
I
!
I
!
I
i
I
122
Variable-Geometry Settinq
"Closed" (Idle)
"Full Open II (100 Per Cent Power)
o ~ I
l.lTD.
i
I
I
I
I
I
i
I
I
---I
I
I
,
I
I
I
I
!
I
i
I
--
---
Federal
1975/76
Goa I - - - -
--
--
--- ---
o
I
50
I
100
200
I
150
Over-All Air/Fuel Ratio
FIGURE 16 - SUMMARY OF NOx AND CO EMISSIONS FOR COMBUSTOR B
-------
123
.
Variable-Geometry Settinq
"Closed" (Idle)
"Full Open" (100% Power)
o
30
-
u
c: 0.02
-------
Q)
::I
~
E
01
........
01
E 10
x
Q)
"'C
C
c
o
.~ 5
VI
E
w
o
u
Q)
::I
~
E
01
........
~ 10
~
x
Q)
"'C
C
c
.~ 5
VI
VI
E
w
x
o
z:
Run
~
-14
---25
15
o
15
o
o
M.a. '1;3 ~J ~p 1:,
Ibm/see deq F ~ per cent ~ 124
O. 11 730 68 2 14
0.21 690 68 2 8
"
"
" " ~ Run 25
"-
.......
......
......
'........
......
......
"- Run 14
Run 14
.....----- ~Run-25
0.3
0.4
0.7
0.8
0.6
0.5
Primary-Zone Equivalence Ratio
FIGURE 18 - TYPICAL EFFECT OF RESIDENCE TIME ON NOx AND CO EMISSIONS FOR COMBUSTOR B
-------
125
. !;,! ~3
Run mo.. 6P Tp
No. lbm/sec deq F ,gill. per cent ~
- 23 0.42 710 68 1.3 10
-.- 26 0.84 880 68 6.3 4
--- - 27 0.78 710 88 2.7 7
---30 0.85 690 68 5.6 5
10
, /Run 23
Q) 8 ~
;:]
4-
E ~. '~Run 27
01
'-
01
E ~ "
~ 6 "" . '-........ ~ Run 26
x
Q)
"'0
C ".
" ----
c .......
0 4 ?"-.....
V1
V1 Run 30 --
E
l.i.J
X
0
:z 2
o
50
,
1.0
100 J 50
Oyer-AI \ Air/Fuel Ratio
.5 ;4. ..
Primary-Zone Equivalence Ratio
200
250
300
.7
FIGURE 19 - TYPICAL VARIATION OF NOx EMISSIONS WITH FLOW CONDITIONS FOR COMBUSTOR B
-------
Q)
:J
.......
E
.;:: 3 0
0\
E
x
Q)
i:J
C
c 20
o
V1
V1
E
L.IJ
a
u
Q) 10
:J
4-
E
0\
........
0\
E
x
Q)
i:J
C
c
o
V1
V1
E
L.IJ
x
a
z
Nozzle
.
o
B1.1
62.1
126
Design Value of
Nozzle Air/Fuel Ratio
Run No.
10
o
5
o
2
4
22, 23, 25,. 27
32, 33, 34, 36
a
61.1
1.0
Primary-Zone Equivalence Ratio
I I
200 100 75
Approximate Over-All Air/Fuel Ratio
50
FIGURE 20 - EFFECT OF NOZZLE AIR/FUEL RATIO ON NOx AND CO EMISSIONS
-------
127
Run No.
. 37-42 - Original Configuration
o 43-48 - Configuration Modified
. to Increase AP and m~
o
o
Q)
:J
4-
E .30.
., t11.
........
t11
E
~
x
Q)
"0
C
c 20
o
f/)
f/)
E
UJ
0
u
10
Q)
:J
4-
E
0'1 10
........
0'1
E
~
x
Q)
"'0
C
C
0
f/) 5
f/)
E
UJ
X
0
:z
o
0.6
0.8
1.0
1.2
Primary-Zone Equivalence Ratio
FIGURE 21 - COMPARISON OF NOx AND CO EMISSIONS FOR ORIGINAL
AND MODIFIED COMBUSTOR B CONFIGURATIONS
-------
128
2.0
o
...
co
ex:
(1)
g 1. 5
(1)
Decreasing
Powe r
co
>
:I
IJ
UJ
(1)
g 1.0
N
I
>-
I..
co
E
Operating Range
I..
0..
0.5
00
0 0 00 00 0 0
«0 0
0 0 eo
0 0°
0
0 1 2 3 4 5 6 7 8
Combustor Loading, 9-1 x 108, Ibm, Ibf, ft, see, deg R units
o
I
.
/Y1Q.
D/.7$"A r,0.75" (T. /)
'03 r~ Ur~ e.X? 03/b
--
I) -
FIGURE 22 - WEAK EXTINCTION LIMIT FOR COMBUSTOR B
-------
C1)
::J
4- 60
E
0'\
........
0'\
E
x
C1)
~
.= 40
c
o
V'I
V'I
E
LLJ
o
u 20
C1)
::J
4-
E
0'\
........
~ 20
x
C1)
~
c
c
o
V'I
V'I
'E 10
LLJ
x
o
z
129
.
o
Variable-Geometry Settinq
o
"Closed" (Idle)
"Part Open" (50% Power)
o
30
._----
.
o
.
.
.
o . 80
000 .
o .
.
o
-----
Federal 1975/76
---- Goal -----
----
o
o
200 300 400
Over-All Air/Fuel Ratio
FIGURE 23 - SUMMARY OF NOx AND CO EMISSIONS FOR COMBUSTOR A
100
500
-------
C1)
:J
4-
E 3
0'\
.........
0'\
E
x
"'
~
c:
c:
0
VI
VI
E
w
0.03
~
I
>-
u 0.02
c:
C1)
u
4-
4-
C1)
c:
c: 0.01
o
....,
VI
:J
.D
E
o
u
.
o
Variable-Geometry Settinq
"C1osed" (ld1e)
"Part Open" (50% Power)
2
Federa 1 1975/76
Goa1 - - - - - -
130
--------
o
o
100
200 300
Over-All Air/Fue1 Ratio
400
FIGURE 24 - SUMMARY OF HYDROCARBON EMISSIONS (HC)
AND COMBUSTION EFFICIENCY (r ) FOR COMBUSTOR A
500
-------
131
. AP Lp
Run 'fIf"Io... 1;;3 Pc, 3
No. 1bm/sec deq F .I?lli per cent msec
~
61 1. 15 90.0. 40. 3.7 20.
- - - 66 1. 39 895 59 2.4 25
-.-63 1.0.6 1150. 40. 3.6 20.
- - - 60. 0..44 90.0. 40. 0..6 55
25
20
\
\ \
, \.
\V Run 63
"'- \. \..
'~" Run
~~ /
Run 61 ~~/
~~
Run 66->---
60.
(])
:J
......
E
0'\
"-
~15
c:
.
x
(])
\j
c
c
o
";; 10.
111
E
w
x
o
:z
5
0.
0. 50. 10.0. /150. 20.0. 250. 30.0.
I I. I
o.ver-AII Ai r/Fue1 Rat i 0
11.0. 10..7
0..5 0..4
Pr i ma ry-Zone Equivalence Rat i 0
FIGURE 25 - TYPICAL VARIATION OF NOx EMISSIONS WITH FLOW CONDITIONS FOR COMBUSTOR A
-------
132
2.0
Decreasing
Power
o
+-J
I'D
ex::
OJ
u
c
OJ
1.5
Operating Range
I'D
>
:1
CT
W
OJ
C
o
N
I
>-
I.-
I'D
E
1.0
I.-
Q..
o
0
0.5
8
0
00 0 0
0
0 2 4 6 8 10 12 14
Combustor Loading, 9-1 x 109, Ibm, lbf, ft, see, deg R units
.
J - n?Q,
B :: f!../' 7~ nO. 'l/" (7:. II}
0.1 Ar¥ ul-¥ eXf OJ ')
FIGURE 26 - WEAK EXTINCTION LIMIT FOR COMBUSTOR A
-------
.
MFN
.
lw
... .
'--
M
St
+
"'
Reci rcu I at ion
Zone
--f
FIGURE 27 - COMBUSTOR FLOW PATTERN SCHEMATIC
--
.--
--
~
v.>
v.>
-------
Fuel-Air
Rat i 0
I
I
I
I
I I
I I
1---,-
I I
I
I
Sw i r 1 e r
S t rea m
Nozzle
Stream
134
Mixed P/rof i 1 e
I I
I I
I Perfectly Mixed
~.--d
I I
I
I
I
Prof i 1 e
Recirculatio
Stream
Transverse Distance
FIGURE 28 - FUEL-AIR DISTRIBUTION IN PRIMARY-ZONE INLET REGION
-------
13
12
11 .
- 10
OJ
:J
<= 9
..."
......
E'
. 8
><
OJ
"C 7
c
C
o 6
\11
\11
E 5
lL1
x
,...
4
3
2
o
40
1.0
Combustor B
Po3= 67.6 psia
:T0,3= 7000 F .
:~= 0.45 lb/sec '
Range of
Experimental Data
Calculated Primary-
Zone Emiss ions
0.8
0.6
160
100 120
Over-All Air-Fuel
I I
0.45 0.375
Primary-Zone Equivalence
Rat i 0
FIGURE 29 - CALCULATED RESULTS FOR COMBUSTOR B
s. = 2. 0
so= 1.0
180
0.30
135
200
-------
(
30
28
26
24
22
20
18
16
14
12
10
8
6
4
: r I
80 1 QO
I '
! I
1.2 1.0
Combustor A
Po3= 58.8 psia
1;,3= 9000 F
M~= 1.0 lbm/sec
Range of
Experimental Data
Calculated Primary-
Zone Emissions
I
120
I
I
0.8
I I
1 60 1 80
Ai~-Fue1 Riatio
'I I
O 6 0 c;'
. . ,,,",'
Primary-Zone Equivalence
I
200
I
0.50
Ratio
I
140
Over-A 11
FIGURE 30 - CALCULATED RESULTS FOR COMBUSTOR A
136
so= 1.0
II
~o = o. 5
I
220
240
0.45
-------
Radial
Inflow
Swi rler.\
o
o
o
Nozzle
I I
I ,
, c::::::>
I !
I c::::>
, .
I I
I I
I cp:>
, I
Sw i r I e r
Flow
Thrott Ie
a.
Mod i fica t i on No.1
Radial
Inflow
. Sw i r I e r
Perforated Plate
I I
. I I 0
I q::==>
I I
I I 0
I a:::::::)
I I
I I
I' 0
Nozzle I
-------
20
138
QJ 15 i r
::J I
......
I I
E I 0 I Federal
0">
......... - - -_. - - - - _1975;76
0">
E ./ Goa
~
x dO - ~1D
QJ
-c .
c:
.
c: 0 I I
0
V1
V1 t,
E 5 !
UJ ~. ......
o 0 d.~ ~ I
u I
.. OJ I
\
~ '
,
I
o I !
--..____L-- ._-~
d Symbol Run No. Conf i gura t ion I
. 51 0 rig i na 1 ,
\ 0 71-72 Mod. 1 ~
6 78-81 Mod. 1
QJ 15 o. 82-85 Mod. 2
::J
...... ~D 0 rig i na 1
E . 55
0"> 0 73-77 Mod. 1
.........
0">
E I
X \-)~original
QJ 10 Combustor A
-c
c:
c
0
V1 O~ '.
V1
E
UJ
5 -1
x
0 ~ f I
Z A "'LJ~ Federal 1975176
p . G~1
lJJ.'i. ....,
- A --- -- -- ------ -- --
o
0 100 200 300 00 500
Over-A 11 Ai r/Fuel Rat io
FIGURE 32 - COMPARISON OF NOx AND CO EMISSIONS FOR ORIGINAL AND MODIFIED COMBUSTOR A
-------
139
Run 6P Wlt>.. "!:'p
Symbol No. per cent Ibm/see msecs
. 74 14.3 0.85 25
o 76 21.0 1. 11 19
20
(I)
::J
4-
5
~15
........
01
E
.
x
(I)
\:)
c
610
V1
V1
E
LLJ
x
o
:z
o
o
Over-All
I
J.O
100
I
Air/Fuel
I
0.7
150
200
Ratio.
0.5
0.4
Primary-Zone Equivalence Ratio
FIGURE 33 - EFFECT OF PRESSURE DROP AND RESIDENCE TIME ON NOx EMISSIONS FOR MODIFIED
COMBUSTOR A
-------
140
e
82
83
84
Type of
Fuel I niection
Pi lot On 1 y
Symbol
.
Run No.
o
Main Aira1ast Only
Ma i n P I us Pi lot
(Pi. lot Flow ~ 12 1bm/
hr)
15
(1)
::J
~
E
Cj)
........
Cj)
E
Main + Pilot~
x
(1)
-g 10
c:
o
VI
VI
E
UJ
Main
x
~ 5
o
o
200
I
1.0
Over-All Air/Fuel Ratio
I I I
0.7 0.5 0.4
Primary-Zone Equivalence Ratio
FIGURE 34 - EFFECT OF FUEL INJECTION ON NOx EMISSIONS FOR MODIFIED COMBUSTOR A
-------
141
Collection Tank
----- Hydrogen Bubb1e
Pum B ass Generator
(3) Vent ~settl iog
~I Tank
" k--
I
Q) Or i f i ce Drain
Pump Outside
. Water
Supply
Combustor Model
FIGURE 35 - FLOW SCHEMATIC OF WATER RIG
-------
Ambient 0-
Air~
Settl ing
Tank
250 psig
Plenum
Chamber
P
FIGURE 36 - FLOw SCHEMATIC OF COLD-AIR TEST RIG
Test
See t i on
tmospheric
Exhaus t
+:-
N
-------
Air Supply
.....
Water
Supply
. Swirler F10N Control
Radial-Inflow Swirler
Airblast Nozzle
Flow Meter
~ .
'"'"
FIGURE 37 - NOZZLE MOUNTING FOR FUEL NOZZLE TESTS
-------
.
High-Pressure
(6 atm) Air
Supply
Low-Pressure
(2.5 atm) Air
Supply
Atmospheric
Vents -
@ .
Heater Bypass Line
Combustor
Test
Section
FIGURE 38 - AIR FLOW SCHEMATIC FOR COMBUSTION TEST RIG
ass Line
Exhaust
to Atmosphere
-l="
-l="
-------
Fuel.
Tank
Bypass Li ne
Flow Meter
T
p
Flow Meter
FIGURE 39 - FUEL FLOW SCHEMATIC FOR COMBUSTION TEST RIG
N i't rogen
pJrge
Gas
To Main Nozzle
To Pilot Nozzle
+:-
V1
-------
Spacer -
Spool
Transition ~
Section.
Ai r
Flow
,~
r '---'--::1
-(- C --ii i ----_J~
'. .... i; -------1 ..
.J --
-~"----
I
Combustor Liner. Water-Cooled Reducer
~~amp I i n9 ~ Sect ion
System
'I rt., .
rf I r J ,_.
l__,._.L_L__.n 11
,.--=. -=-=-==..~..- ..' l I I: " -
/ I I --'-'r-~
/ I I I: I / _..:;-- To .
[ I : :: : 1:>< - / Exha us t
'- ... - -- - _. --..- ..J:: I I ------, I
~8 KV Probes
Fuel. ..' . Water-Cooled
Flow Ignition Gas Sampling
System. Probes
---- .
Combus tor. -
Water-Cooled
Instrument Section..
Nozz I e
Mounting
Section
_\-
Nominal Dimensions
Diameter
in
Spacer Spool:
Combustor A
Combustor B
Transition Sec-
tion
Nozzle Section
Instrument Sec-
tion
ReduGer Section
4
4
9
9
9
9-6
FIGURE 40 - COMBUSTIO'N TEST SECTION
Length
in
17.00
23.50
19.50
6.25
+:-
'"
1-.5.00
12.00
-------
Gas Flow
25 in
~
147
Wire length
"
,
1/8 in Diameter Inconel Tube
, ,
.
3/16 in Diameter Inconel Tube
Insulation
Chromel Alumel
0.03 in Thermocouple Wire
:. ,'..
, .
. ..
" .
, .
, '
1 "
'. '
.: ..:
" .
. ,
.. '
.' ..
, '
"
. "
. ,
, "
. '
"
" '
, "
'. ..
"
.
; ,
,. .t
, ,
, "
, ,
Bleed Hole
r
~
FIGURE 41 - THERMOCOUPLE PROBE
-------
Combustor
Casing
Combustor
Liner
Flanges
f; rect ;on
of Travel
Thermocouple Probes
.
Thermocouple Probes
~ 0.39 in
Combustor
Exit
FIGURE 42 - SPACING OF THERMOCOUPLE PROBES
Spa rk Plug
P 05 i t i on
~
00
-------
- -
.8 = 1 72. 5°
9 = 82. 5°
9= 82.5°
149
9 = 1 72 . 5°
- _9 = 0
9 = 22. 5°
-- 6. 0
The rmocoup 1 e '
Probes ..
."- - .-.-.--.--- ,--'.
e = 232.5°
.
9= 112.5°
e = 67.5°
e = 11 2. 50
(J = 22.5°
() = 22.5°
- -9 = 0
i
--8= 01
Dilution Holes.
S = 337. 5;" S-"~-20~ 50
I) = 247.5°
8= 292.5°
e = 292.5°
e = 11 2. SO
9= 112.5°
"e=22.So
--
9 = 22. 5°
9 := 157.5°
e= 157.5°
9= 202.5°
--9= O~
Secondary Holes
9 ~ - 337 ~50--e~-i62. 50
e = 0 .
e = 337.50
Spe rk
Plug
Position
B= 247.5°
Spark
Plug
Position
C«>mb.us t6r A
Combus tor B-
FIGURE 43 - RELATIVE CIRCUMFERENTIAL ORIENTATION OF THERMOCOUPLE PROBES
-------
l-~
Thermocouple
Probes
Flanges
I .
0.39 i
Combustor
Casing
Combustor
liner
"
~~
,
I
I
I
,
I
I
I
Gas Samp I i n9
Rakes
I I
I I
,.],
::JI,
J'
;J'
'., I
,J I
" I
I ,
,J t
'.,
I I
S,I
" I
,-
:1 1
-, I
I I
: I
5,1
.,1
.-JI
;:J
'., 1
JI
il
)1
,I
;'1
:' I
)1
",
I I
in
I
I Spa r k P I u 9
Position
Combustor
Exit
V1
o
FIGURE 44 - SPACING OF GAS SAMPLING RAKES
-------
8 = 1 12 . 5°
9 = 145°
e = 112.5°
e = 145°
151
8=0
Samp 1 i ng .
Probes
6='0
.
I) = 112.5°
9 = 67.5°
e = 11 2. 5°
e = 22. So
G = 157.5°
B= 202.5
9=22.5°
e =0 -
D i 1 ut i on Ho 1"es', -,r
<9';; '337: 50-' A -
. ~= 202.5°
8=0
9= 157.5°
G = 292. SO
e = 67.5°
e = 292. 5°
{J = 247. 5°
'8 = 112.5°
e = 22.5°
s= 157.5°
e = 22.5°
8=0
9= 202.5°
8= o.
Secondary Holes
9= 337.5° '8 = 202~5°
(7= 337.5° ,
9= 247.50
Spark
Plug
Position
9= 247.50
Spa r k
Plug
Pos i t ion
Combustor A
Combus tor B '
FIGURE 45 - RELATIVE CIRCUMFERENTIAL ORIENTATION OF GAS SAMPLING PROBES
-------
Gas
Sample
:
Water Flow
-i
E
]
t ~
2.23 in C ~
1.22 in
A
t
0.50 in
3.06 in
D
0.052 in
--i
rO in
1.2: in]
L
1.60 In B ~
j ~
2.23 in C ~
j .dJ
D]
3.06 in
E
0.187 in
0.500 in
FIGURE 46 - DESIGN OF GAS SAMPLING RAKES
152
-------
PR
Shop
Ai r
Heat ZJ
Trace
NREC
Smoke
Sampler
CV
,
,----------"1
I. R Vent I
I V F I
BD I H~a -; 7" - -l
L______--~--, ,Trace:
I
CV
Refr i gera ted
Condenser
Vent
Drain
Trap
CO
Analyze
Beckman'
Model
FI GURE 47 - SAMPll NG TRA I N OF EX I ST I NG NREC ENG I NE EXHAUST -SAMPll NG F AC IllTY
Hydrocarbon
Ana 1 yze r
Beckman
Model 402
NO-NOx
Ana I yzer
TECO Model
I A
PR - Probe
BV - Ball Valve
CV - Control Valve
F - Filter
BD - BICM Down
R
- Regulator
CV
CV
\J1
W
-------
154
120
100
Swirler Setting,,(sw, in
0.2
o
6
0.3
t/1
C
0
'-
u 80
.-
E
-.
0
L ~
V>
.........
'-
Q) 60
....
Q)
E
ro
0
c
ro
Q)
L
'- 40
Q)
....
:J
ro
V>
20
o
O. 7
0.8
0.9
1.0
1.1
1.2
Ratio of Air Pressure Drop to Nominal Value of Air Pressure Drop'
Note:
Nomina1 test conditions correspond to simulation of hot
rig conditions given in Table XXV
FIGURE 48 - EXPERIMENTALLY DETERMINED VARIATION OF MEAN DROPLET SIZE WITH
AIR PRESSURE DROP FOR AIRBLAST PORTION OF NOZZLE A2.2
-------
7
Nominal Test Conditions
155
c:
6 "-
-
"')
/
\
......
.....
~
Air Pressure Drop 22.5.Per Cent
Above Nominal Value
V1
:J
"'0
!'O
a::
5
-L
--
4
-
--:>
--
-
--
-
-
--
...--"
..-
_r-
-
3
oT
.L_..,
(a) .1sw= 0.2 in
7
c:
Nominal Test Conditions
6
V1
:J
"'0
ru
a::
5
Air Pressure Drop 10 Per Cent
Above Nominal Value
4
o
o
2
4
3
5
Note:
Ratio of Local to Average Fuel Mass
( b) L $W = o. 3 i n
Nominal test conditions correspond to simulation of hot
rig conditions given in Table XXV
FIGURE 49 - EXPERIMENTALLY DETERMINED RADIAL DISTRIBUTIONS OF SPRAY
FOR AIRBLAST PORTION OF NOZZLE A2.2
-------
Symbo 1 s
~11
Il eff
h.,
;,
Arej
AT
b
Cd
%
])ril
£I
F
3
is""
l~t
MW
m~
W\b,~~J
.
rn c/; d
NOMENCLATURE
Description
Physical flow area of a'single set of
openings (for example, row of holes or
swirler) into the combustor liner
Effective flow area (C~Ah ) of a single
set of openings into the combustor 1 iner
Reference flow area (casing flow area)
Sum of effective flow areas
openings into the combustor
(E. Ah;'f/- )
of all
1 i ner
Inlet temperature factor (see p. 170)
Discharge coefficient
Carbon-to-hydrogen weight ratio of
the fuel
Reference diameter (inner diameter
of cas i ng)
Emission index (computed as N02 for
NOx and as C3Ha for HC)
Mole fraction
Proportional ity constant in
Newton's law (32.2)
Swirler flow throttle setting
(see Figure 10)
Secondary-hole flow throttle
setting (see Figure 10)
Molecular weight
Total mass flow rate of air
Mass flow rate of air through
bleed holes
Mass flow rate of air through
dome fi 1m cooling slot
156
Units
sq ft
sq ft
sq ft
sq ft
deg R
ft
mg per gm fuel
Ibm ft per
lbf sec2
in
in
1 bm pe r 1 bm
mole
1 bm per sec
per cent of
total air flow
per cent of
total air flow
-------
Symbols
(Y)cl, J i./
t1?Cf .
I £.
mcf.
,p
mdL/
"
m t: N'
vi?
fu
VYlp
rr1 f' / ell-
.
fflSr
""'s w
.
rn Sj
m .
s.:JJi.
~~p
p
fpm
~
157
Description
Units
-
Mass flow rate of air through
dilution zone film cooling slot
per cent of
total air flow
Mass flow rate of air through
intermediate zone fi 1m cooling
slot
per cent of
total air flow
Mass flow rate of air through pri-
mary zone fi 1m cooling slot
per cent of
total air flow
Mass flow rate of air through di-
lution holes
per cent of
tota 1 air flow
Mass flow rate of air through
fuel nozzle
per cent of
total air flow
Total mass flow rate of fuel
Ibm per hr
Total mass flow rate of air
through primary zone
per cent of
total air flow
Effective primary-zone flow rate
(portion of air flow participat-
ing in the combustion process)
per cent of
total air flow
Mass flow rate of air through
spark plug cooling holes and
through clearance between spark
plug and liner
per cent of
total air flow
Mass flow rate of air through
swirler
per cent, of
total air flow
Mass flow rate of air through
see onda ry ho I es
per cent of
total air flow
Portion of air through secondary
holes flowing downstream
per cent of
tota 1 air f low
Portion of air through secondary
holes recirculating upstream into
primary zone
per cent of
tota 1 air flow
Total pressure
psia
Volumetric concentration of a
chemical specie expressed as
parts per mi 11ion
ppm
Dynami c head
psia
-------
Symbols
'l-a..Ht1k/...~
~('e{
R
So
..
'G"
x
:t
z
1lH,:
AP
A PNN.
4~1
~t:
e
Description
Dynamic head based on annulus
flow a rea
Dynamic head based on reference
flow area
Gas constant
Degree of "mixedness" of fuel!
air distribution in primary zone
defined as standard deviation of
mixture ratio (Ibm fuel per Ibm
total mixture) distribution
divided by mean value
Total temperature
Exit temperature traverse qual ity
defined as difference between
maximum and mean values of com-
bustor exit temperature profile
divided by temperature rise in
combustor (see Appendix I I)
Number of carbon atoms in one
molecule of fuel (CxHy)
Number of hydrogen atoms in one
molecule of fuel (CxHy)
Air/fuel ratio' (air flow rate
divided by fuel flow rate)
Lower heating value of fuel
Pressure drop across 1 iner
Air pressure drop across fuel
nozzle
Pressure-loss factor
Combustion.efficiency (see
Appendix I J)
Combustion-efficiency parameter
(-it!. ,.~JA 0.75 (; '1 J' )
8 = I-i!)3 ref Dre! eJ
-------
Symbols
Description
f'
If
Gas density
Approximate primary-zone residence
time calculated on basis of inlet
temperature and pressure
~
Primary-zone equivalence ratio
(stoichiometric air/fuel ratio
divided by actual air/fuel ratio)
Subscript
a
Ai r
co
Carbon monoxide
COz
Carbon dioxide
F
Fuel
HC
Total hydrocarbons expressed as C3Ha
Nitric oxide
NO
NOx
Total nitrogen oxides expressed as NOZ
st
Stoichiometric value
03
04
Combustor inlet
Combustor exit
159
!!!lili
Ibm per cu ft
msec
-------
160
APPENDICES
"
-------
161
APPENDIX I
DESCRIPTION OF EXPERIMENTAL FACILITIES
The testing phase of the program was conducted using basically
three different test rigs: a water rig for the combustor flow visual iza-
tion tests, a cold-air rig for the air distribution and spray visual iza-
tion tests, and a hot-test rig for the detailed combustion tests.
The
experimental apparatus and instrumentation used in each of these rigs are
described in this appendix.
Water Riq
The f'low schemat i c of the water rig is shown in Figure 35.
The closed-loop system is connected to the main laboratory water supply
and was drained and refilled at the start of each day of testing. The
materials used in the water rig were selected to insure acceptable water
clarity.
All tanks in the system were constructed of aluminum and the
water was directed through flexible rubber hoses and stainless steel pip-
ing.
The settl ing tank was designed to damp any turbulence generated
by the pump and to straighten the flow through a set of twenty-mesh
screens. The bleed valve in the settl ing tank was used to relieve air
trapped in the tank during the fill ing and start-up of the system. In
each test, hydrogen bubbles were used as the flow tracers. These were
generated electrically by a straight-I ine grid of stainless steel wires
located just upstream of the inlet to the combustor model. The flow pat-
terns in the combustor were observed by illuminating a longitudinal dia-
metrical plane in the transparent combustor model by a high-intensity
sl it I ight source. An adjustable Plexiglas duct between the combustor
exit flange and the collection tank was used to compensate for the dif-
ference in length between the two combustor models tested. The water
exiting from the combustor entered the open collecting tank which served
to vent the hydrogen to the atmosphere.
The major measurement taken during the flow visual ization tests
was that of the water flow rate.
This flow rate was measured by a square-
edge orifice plate designed to ASME specifications.
(Re f 21).
The or i-
-------
l~
fice size was 1.40 inches in diameter in a 4-inch pipe.
The temperature
upstream of the orifice was measured with a thermometer and the pressure
drop across the orifice with a mercury manometer.
Cold-Air Riq
The cold-air test rig was used for both the air flow distribution
tests and the spray visual ization tests. The general flow schematic of
the test rig in shown in Figure 36. Air was suppl ied by a large pres-
surized tank that was continuously replenished by an air compressor during
operation of the rig. The test section used for the air flow distribution
tests consisted of the actual metal combustors. For the spray tests the
test section consisted of the specially constructed nozzle mounting section
shown schematically in Figure 37. Water was used in place of the fuel,
and the spray pattern was observed and photographed by illuminating with
a high-intensity 1 ight source.
The air flow rate was measured using a standard ASHE square edge
orifice section. Orifices ranging from 0.5 inch diameter to 1.45 inch diame-
ter in a 2-inch pipe were used for flow rates from 0.005 to 0.3 lbm/sec air.
The air temperature was measured with a thermometer and the pressure drop
across the orifice with a 30-inch manometer carrying 1.75 specific gravity
fluid. The same type of manometer was also used to measure the static
(total) pressure in the transition (or settl ing chamber).
Combustion Test Riq
Air Supply
A schematic of the air flow system is given in Figure 38. Air
was supplied by either of two gas-turbine driven compressors. The high-
pressure unit was capable of delivering up to 6.5 Ibm per sec of air at
6 atm and the law-pressure unit up to 3 Ibm per sec at 2.5 atm. The air
from either source was heated by passing through a FECOR gas-fired indirect
heater capable of heating up to 3 Ibm per sec of air to 1200 degrees F.
The temperature of the air leaving the heater was automatically controlled
at the set point which could be adjusted to give air temperature in the
-------
163
range 500-1200 degrees F. The piping system consisted of 4-inch diameter
pipe. Carbon steel pipe was used up to the heater inlet and well-
insulated stainless steel pipe from the exit of the heater to the inlet
of the combustor test section.
Fuel Supply
The fuel used in all of the combustion tests was Jp-4 jet fuel
(MIL-J-5624F) stored in an underground 200 gallon capacity tank. The
schematic of the fuel supply system is shown in Figure 39. The fuel pump
was continuously in operation during testing and was capable of del ivering
up to 60 gph at 600 psi. The fuel del ivery pressure was adjusted manually
by opening or closing the valve in the bypass line. The fuel flow to the
main and pil~t nozzles was controlled by needle valves contained in the
flow meters.
Test Section
section.
Figure 40 shows the major components and dimensions of the test
The spacer spool was used to compensate for the difference in
length between the two combustors tested.
The transition section was de-
signed to allow for diffusion of the incoming air entering the combustor
section. It was also designed to give a plenum chamber effect for measure-
ment of inlet total pressure.
The nozzle mounting section was designed to
support the fuel nozzle and provide access to the inlet end of the com-
bustors.
The instrumentation used to measure the combustor exit pressure
and temperature dIstribution and the probes used to obtain the exhaust
gas sample were mounted in the instrument section. The conical reducer
section provided the transition in diameter between the instrument sec-
tion and the pneumatically controlled back-pressure valve.
The instru-
ment section and the reducer section were both water-cooled.
Instrumentation
The general methods used to conduct the measurements for the
combustion tests are listed in Table XXI I. Specific details of the in-
-------
164
strumentation are discussed below.
Flow Rates
The mass flow of air was measured indirectly by a 3-inch diameter
square-edge orifice designed to ASME specifications. The fuel flow to the
main nozzle was measured by a Brooks Instrument Company floating-ball
type flow meter cal ibrated for JP-4 fuel and having the range 0-24 gph
with 2 gph divisions. The fuel flow through the pilot was measured in-
directly by the del ivery pressure and directly by a similar flow meter
cal ibrated for water and having the range of 0-9 gph of water with I gph
divisions.
Pressures
The following pressure measurements were taken during each of
the combustion tests:
1. Pressure drop across the orifice plates.
2. Pressure drop across the combustor.
3. Static (total) pressure at the combustor inlet.
4. Static pressure at the combustor exit.
5. Total pressure at the combustor exit.
Items 1 and 2 in the above 1 ist were measured with a 100-inch
manometer containing 1.75 specific gravity fluid.
Static and total pres-
sures were measured with 0-100 psig range Heise gauges having 0.1 psig divisions.
Inlet pressure and exit static pressure were measured by static pressure
taps at the downstream end of the transition section and at the combustor
exit plane in the instrument section, respectively.
The combustor
exit tota1 pressure was measured using the gas sampl ing rakes in a no-
flow mode.
couples.
All stream temperatures were measured with chromel-alume1 thermo-
Temperature measurements were taken at the following stations.
1. Upstream of the orifice plates leading to the heater inlet,
the heater by-pass I ine, and the combustor test section.
2. Fuel temperature at the inlet to the fuel nozzle.
-------
165
3.
Gas sampling stream at the inlet to the gas-analysis con-
sole.
Combustor exit plane.
4.
The millivolt outputs from the thermocouples were read using a digital
voltmeter (DORIC Model No. DS100). The thermocouples were cal ibrated at
two points-- 32 dcigrees f (ice bath) and 212 degrees.f (boil ing water).
The exit temperature distribution was measured by four thermo-
couple probes of the type shown in Figure 41. These probes were placed
in remotely actuated traversing mechanisms mounted on the outside of the
instrument section at the combustor exit plane. The probes were spaced
in the circumferential direction such that two opposite quadrants of the
combustor exit area could be traversed as shown in Figure 42 and 43.
Each probe was traversed in the radial direction and readings were taken
at the radial. positions given in Table XXI I I. These positions were se-
lected by dividing the combustor exit into equal areas and choosing ap-
proximately the radial midpoint of the equal area rings.
Liner temperatures were measured using a number of different
thermal paints each of which undergoes a phase change at a specific value
of temperature. The paints were selected to provide temperature indica-
tions in the range 1400-1900 ~egrees F in approximately 50 degrees F in-
tervals. The paints were appl ied to the outside surface of the 1 iner in
longitudinal stripes.
Exhaust Gas Composition
A 1 ist of the chemical species measured and the instruments
used is given in Table XXIV.
The gas sample for analysis was obtained
using two water-cooled sampl ing rakes extending across the diameter of
the instrument section as shown in Figures 44 and 45. The design of each
of the two rakes is shown in Figure 46. The radial spacings of the tubes
and the orifice sizes were chosen to provide equal increments in flow
through each tube. The two outer tubes on both ends of each rake (D and
E in Fig 46) were blocked off with a tight fitting cap when Combustor B
was being tested. A sample could be obtained from either of the two
-------
166
rakes independently or both together. Initial tests showed that the
latter approach provided a representative sample; therefore, this was the
approach util ized.
A schematic of the sample handling system is given in Figure 47.
The la-foot stainless steel I ine from the water-cooled rakes to the tem-
perature controlled heated box was heated with electrical tapes to an av-
erage temperature of 370 degrees F. The heated box which contained the
filter and regulatory station was maintained at a temperature of 400
degrees F. The I ines from the heated box to the hydrocarbon analyzer and
the NO-NOx analyzer were also heated. The I ine to the CO and C02 analyzers
passed through a refrigerated condenser to el iminate water vapor from the
sample. The sample collected at the combustor exit was divided among the
various analyzers shown in Figure 47 to provide continuous and simul-
taneous analysis of the various pollutant species. When smoke measure-
ments were conducted, the I ine to the analyzers was closed and the sample
was passed through the smoke meter.
-------
'-
167
APPEND I X I I
DATA REDUCTI ON
The equations used in computing the major performance parameters
from the test data are presented in this appendix.
Fuel Properties
All of the tests were conducted using JP-4 jet fuel (MIL-J-5624F).
The pertinent properties of this fuel were obtained from data given in
References 8, 9, and 23. The values of these properties used in the re-
duct ion of the test data are as follows:
l:1HF' = 18,752
C/H = 6
MWF = 11 2
2'.:It- = 14.8
Btu per Ibm
Representing the fuel by the general molecular formula CxHy and using the
values of carbon-to-hydrogen weight ratio (C/H) and molecular weight ( ~WF)
I isted above gives:
x = 8
y = 16
Air Flow Distribution
The values of air flow rate through the individual sets of open-
ings in the combustor were computed using the data obtained in the cold-
air tests. These data consisted of the variations of mass flow and pres-
sure drop for each set of open i ngs and 'the pressure and temperature of
the flow.
The measured values were used to compute the effective area
of each set of
openings by the relation,
J ,.~ r' )7°'~
M" = ccllt" [~ ~ fAr = IJItJi(. l!- 9 f II fj
where the density, jP , is calculated from the pressure and temperature as;
p
f:: .-
R-r
-------
168
The fraction of the total air flow rate through each set of openings was
computed as,
where
rY7
:.:.!!- :=
ri1.,.
the total
fI~J4I.
IIr
air flow
rate and ~T is the sum of the values of
The effective primary-zone flow rate
M- is
I
flh,C' ~ X) O;z. -+ X C~ + 1 ~ 1-6.0
CI( HI + (f.;. .f) O;t ~ >( CO + ~ '11120
CX H~ -I- ~ (~- ~3X) 0,..--+ f (C31-18) + i (~- ~3X) HitO
C3 H8
in the last of the re~
actions I isted above because this is the form on which the reading from
the hydrocarbon analyzer is based. The resulting equation for % is:
where
1 = X ( MWCl \
. HWF )
0(;: ~ /4 X
I-f- ~.~c>~ - (k -~) {::o - 3 (i - ~) tlk:.
fc:o~ + {'co +:StHC.
and .f stands for the mole fract ion of
each species as
determined from the emission
r -:: PPM, X IO-~
teo;:. cQ..z.
feD = pf"Wlco 'I iO-b
fifC, :: pp Mile. X' ICJ-h
analysis readings,
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Primary-Zone Equivalence Ratio
The expression used to calculate
4'p
is
~ ' (-:::<{{)
25 f-
"2
whe re Wtp/ eft.
as percentage of total air flow rate.
is the effective primary-zone air flow rate expressed
Emission Index
The values of the emission index in mg per gm fuel for each of
the pollutant species were computed from the following general relation:
IJ (' M 1..1.' ( '5
EJi = . i. MW~) l.+f) X ID
where the subscript Ilill stands for each of the species, NO, NOx (expressed
as N02), CO, and HC (expressed as C3H8).
Combustion Efficiency
The combustion efficiency was computed from the measured emis-
sions of hydrocarbons and carbon monoxide with the relation
f/ = /- ~ ( MWF ) (£[ ~ ID-3" - (. ~HH~O) (El )( ItJ..3)
(c X "Ii i"(. He. J ~ F CO
I-' -'He'
where AHco is the heat of combustion of carbon monoxide, 4,348 Btu per
Ibm CO (Ref 24).
Exit Temperature Traverse Qual ity
The traverse qual ity was calculated from the measured exhaust
gas temperature distribution as
TQ ;:
t;;4-; mo./(" - 7;.
7;;.. - ~.3
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where
~~~~~ maximum measured value of exhaust gas temperature
7;.
~ average exhaust gas temperature
1";,3 -= inlet gas temperature
Combustion Efficiency Parameter
The combustion efficiency parameter used in correlating the
blow-out data was calculated as
where
1.15" 0.7S"
e = 11."3 firer I>ref ekP(r;5/b)
"';'4.-
, the inlet temperature factor (Refs 8
and 9) was approximated
b
by the 1 inear equation
b: 59' ~ deg R
and evaluated at the design value of
tpp
for each combustor.
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171
APPENDIX I II
NOZZLE SPRAY ANALYSIS TESTS
At the conclusion of the combustion testing portion of the pro-
gram, a series of tests was conducted to determine the spray performance
of the airblast portion of the nozzle designated as A2.2 (see Table V).
The results obtained for this specific nozzle should be fairly typical,
since all of the nozzles examined in this program are essentially of the
same general design. The spray analysis tests were performed by the Ac-
cessories Division of Parker Hannifin Corporation using a high-speed spray
analyzer (Ref 25) which has the capability of providing detailed informa-
tion on droplet size and distribution. The tests and results obtained
are described in detai 1 in Reference 26 and are summarized in this appen-
dix.
Description of Tests
The nozzle was tested at two swirler settings ("closed" and
"part open") under cold-flow conditions (essentially ambient air tempera-
ture and pressure) selected so as to model hot-rig operation at the two
sets of conditions given in Table XXV.
These swirler settings and hot-
rig flow conditions correspond approximately to idle and 50 per cent power
operation. In addition to these tests, the effect of air pressure drop
on spray performance was examined by varying the air flow rate about the
nominal value for each of the two swirler settings.
Results
At the nominal flow conditions corresponding to simulation of
the hot-rig conditions, the distributions of droplet size and mean values
are as given in Table XXVI for each
variations of SMD with air pressure
general trends of the data indicate
of the two swirler settings. The
drop are shown in Figure 48. The
that atomization improves (that is,
the mean droplet size decreases) as the air pressure drop is increased.
The radial distribution of the fuel spray was measured at an
axial distance 4 in downstream of the nozzle.
The distributions obtained
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at the nominal test conditions for the two swirler settings are shown in
Figure 49. As can be seen, both distributions are relatively nonuniform
exhibiting a number of sharp peaks. The effect of increasing the air
pressure drop on the spray distribution is also shown in Figure 49. In
general, the uniformity of the spray improves as the air pressure drop
is increased.
Visual examination of the atomizer assembly both during and
after testing led to the following observations:
I. The nozzle contains eight fuel ports and eight swirler
va nes.
2.
Eight corrosion patches were present on the I. D. of the
nozzle indicating that combustion had occurred previously
within the confines of the prefilming cylinder of the noz-
zle.
3.
At high values of air pressure drop, eight separate and
distinct fuel streaks were observed.
At low values of air pressure drop, the eight streaks co-
4.
alesced into three oscillating streaks.
As the air pres-
sure drop was reduced to even lower values, the oscilla-
tion became more severe and fuel could be observed in
puddles on the Q. D. of the prefilming cylinder.
Cone 1 us ions
The nozzle as tested under modeled hot-rig conditions exhibited
poor atomization quality which can be reasonably attributed to fuel streak-
ing. Although the specific causes of the fuel streaking cannot be deter-
mined precisely, it is likely that the observed corrosion patches and
possible inefficiency of the radial inflow swirler are contributing fac-
tors.
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