EMISSIONS FROM AND WITHIN
A FILM-COOLED COMBUSTOR
Environmental Protection Agency
Grant No. R-801284 - Final Report
R.A. Shisler, J.H. Turtle, and A.M. Mellor
Report No. PURDU-CL-74-01
THE COMBUSTION LABORATORY
SCHOOL OF MECHANICAL ENGINEERING
PURDUE UNIVERSITY
WEST LAFAYETTE, INDIANA
February 1974
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430R740O1
Emissions I;rom mid Within
A Film-Cooled Combustor
Environmental Protection Agency
Grant No. R-801284 Final Report
by
%
R. A. Shisler, J. H. Tuttle, and A. M. Mellor
Report No. PURDU-CL-74-01
The Combustion Laboratory
School of Mechanical Engineering
Purdue University
West Lafayette, Indiana
February 1974
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I I
ACKNOWLEDGEMENTS
For their aid in instrument set-up and data gathering the
authors would like to thank Messrs. R. Altenkirch, S. Jochem, S.
Plee, and R. Vogt.
Special thanks go to Mr. Thomas Miller for his valuable
assistance in the maintenance and operation of the experimental
facility and to Dr. R. E. Sampson of the Environmental Protection
Agency fOffice of Air Programs) for his aid in the study.
Continuing cooperation from Detroit Diesel Allison Division,
General Motors Corporation in supply of liners, igniters, and
injectors, as well as pertinent design information, is gratefully
acknowledged. Mr. J. M. Vaught, Mr. F. J. Verkamp, and Dr. David
Clark have been particularly helpful.
This research has been financed with Federal funds from the
Environmental Protection Agency under Grant Number R-801284. The
contents do not necessarily reflect the views and policies of the
Environmental Protection Agency, nor does the mention of trade
names or commercial products constitute endorsement or recommendation
for use.
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Ill
TABLE OF CONTENTS
Page
LIST OF TABLES iv
LIST OF FIGURES v
ABSTRACT vii
I. INTRODUCTION AND SUMMARY 1
11. EXPERIMENTAL GAS TURBINE COMBUSTION FACILITY 4
A. Test Cell Hardware 4
1. Air System 4
2 . Fuel System and Injectors 6
3. Combustors and Igniters 7
4. Probe and Probe Positioner 10
5. Uhcooled Gas and Temperature Rakes 11
6. Water-Cooled Gas Rake 12
7. Back Pressure Valve 14
B. Control Room Instrument at j on 14
III. RESULTS AND DISCUSSION 19
A. Combustor Operating Points and Inlet Air Quality. 23
B. Combustor Exhaust Plane Measurements 27
1. Carbon Monoxide and Unbumed Hydrocarbons 27
2 . Nitric Oxide 32
3. Summary 35
C. Internal Measurements 37
1. Flow Model 37
2. Summary 42
IV. FUTURE EFFORTS 44
LIST OF REFERENCES 47
APPENDIX. DETAILED INTERNAL MEASUREMENTS 49
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IV
LIST OF TABLES
Table Page
3-1. Test Combustor Operating Points 24
3-2. Heating Combustor limissions With and
Without Prevaporizing Coil 26
3-3. NO from T-56 Engines 34
3-4. Area-averaged Emissions at Various
Axial Planes 41
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V
LIST ()!•' FIGURES
Figure Page
2-1. Complete combustion facility schematic 5
2-2. Schematic of vaporizer 8
2-3. Details of vapor fuel nozzle 9
2-4. Schematic of gas sampling rake 13
2-5. Sample gas flow path within water-cooled rake 15
2-6. Schematic of gas handling system 16
3-1. T-56 combustor configuration 20
3-2. Axial sampling planes and T-56 air flow split 21
3-3. Location of radial sampling points 22
3-4 . Net CO concentrations versus power setting 28
3-5. Net HC concentrations versus power setting 29
3-6. Net NO concentrations versus power setting 33
3-7. Schematic of T-56 flow model 39
3-8. Temperature contours of Cornelius et al. (1957).... 40
A-l. Axial HC concentration profile,
radial position 1 50
A-2. Axial CO concentration profile,
radial position 1 51
A-3. Axial NO concentration profile,
radial position 1 52
A-4. Axial HC concentration profile,
radial position 6 54
A-5. Axial CO concentration profile,
radial position 6 55
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Figure Page
A-6. Axial NO concentration profile,
radial position 6 56
A-7. Axial HC concentration profile,
radial position 2 57
A-8. Axial CO concentration profile,
radial position 2 58
A-9. Axial NO concentration profile,
radial position 2 59
A-10. Axial HC concentration profile,
radial position 3 60
A-ll. Axial CO concentration profile,
radial position 3 61
A-12. Axial NO concentration profile,
radial position 3 62
A-13. Axial HC concentration profile,
radial position 5 63
A-14. Axial CO concentration profile,
radial position 5 64
A-15. Axial NO concentration profile,
radial position 5 65
A-16. Axial HC concentration profile,
radial position 4 66
A-17. Axial CO concentration profile,
radial position 4 67
A-18. Axial NO concentration profilej
radial position 4 „ 68
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VI 1
ABSTRACT
In order to reduce gas turbine combustor emissions it is
essential to have detailed knowledge of the combustor flow pattern
and zones of chemical reaction. Without this information liner re-
design for minimum pollutants becomes a trial and error process.
Previous internal probing of an Allison J-33 penetration jet
type combustor (Mellor et al., 1972a,b; Tuttle et al., 1973a,b) re-
sulted in a model of the flow pattern and combustion process for
this liner. These data were also used to develop a model for com-
bustion of liquid fuel sprays (Mellor, 1973). Similar internal
measurements of carbon monoxide, unburned hydrocarbons and nitric
oxide concentrations were made at different axial and radial positions
for an Allison T-56 film-cooled liner. In addition, pollutant con-
centrations were measured at the combustor exit plane for liquid and
vapor fuel at various levels of combustor loading.
The internal pollutant concentration profiles were used to con-
struct a flow and combustion model for the T-56 liner. All of the
data gathered were found to be consistant with the model of spray
combustion of Mellor (1973).
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I. INTRODUCTION AND SUMMARY
Air addition for secondary combustion and dilution in gas tur-
bine engine combustors is usually accomplished via penetration jets
or film cooling slots. The Allison J-33 combustor is predominantly
of the former type, and previous work in this laboratory has been
devoted to characterization of the combustion process and emissions
for this liner (Mellor et al., 1972a,b; Tuttle et al., I973a,b). Com-
bustor exhaust plane emissions variations with cycle operating para-
meters have also suggested a general two-part physical model for spray
combustion supported by simplex pressure-atomizing fuel injectors (Mellor,
1973) . The heart of this model is the ratio of two characteristic
times, fuel droplet lifetime to some fluid mechanic time, which determines
the emissions of NO and to a lesser degree those of CO. At engine idle,
this ratio is greater than one, and heterogeneous processes are impor-
tant; at design the contra condition holds and mixing controls. Sub-
sequent work based on the observations of Appleton and Heywood (1973)
implies that similar phenomena apply for air-assist nozzles (Mellor, 1974)
In the present report results of a similar experimental study of a
primarily film-cooled combustor, the Allison T-56 liner, are summarized.
Exhaust plane measurements of unburned hydrocarbons (HC), CO, and NO
were made with both liquid and vapor CJHL as fuel in a vitiated air
O O
facility capable of simulating the actual environment of a typical air-
craft can. In addition, detailed gas sampling for the same species
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within the combustor, in conjunction with temperature profiles re-
ported by Cornelius et al. (1957), allow developing a (Qualitative
picture of the flow pattern at the design point. These measurements
were conducted with liquid C,HR fuel and allow direct comparison with
analytical models of the combustion process, as well as revealing any
significant differences between jet- and film-cooled liners.
The conclusions can be summarized as follows: combustor exhaust
plane emissions showed no significant variations between firing with
liquid and vapor CJi8, a result consistent with the low values of
O O
estimated liquid drop lifetimes for the engine operating points in
question. Comparison of these data with those of other investigators
who sampled at the engine exhaust plane (Vaught et al., 1971; Hare
et al., 1971) indicate that HC and CO reactions continue downstream
of the combustor in an actual engine and that prevaporization of a
less volatile fuel more typical of aviation usage could lead to sub-
stantial reduction in NO emissions.
Internal measurements of HC, CO, and NO suggest a flow pattern
in the T-56 liner similar to that within the J-33 and consisting of a
turbulent diffusion flame with an embedded recirculation zone. This
flame extends almost the length of the combustor and is entirely con-
sistent with the physical model of spray combustion developed for
engine design, where fuel atomization is good (Mellor, 1973) .
Since the T-56 engine is thought to emit significant quantities
of N02 (Vaught et al., 1971; Hare et al., 1971), a non-dispersive
-------
ultraviolet analyzer for NCL was also used during the present study
However, it was found that the extreme sensitivity of this instru-
ment to soot present in the gas sample, both within and at the exit
plane of the combustor, precluded meaningful determinations of NCL.
A review of reported NCL measurements from gas turbine engines, as
well as difficulties in making such measurements with current
sampling techniques and instrumentation, has been published else-
where (Tuttle et al., I973c).
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II. EXPERIMENTAL GAS TURBINE COMBUSTION FACILITY
The gas turbine pollutant emissions data were obtained from a
facility especially designed to simulate gas turbine combustion. The
complete facility has been extensively described by Mellor et al.
(1972a) and Tuttle et al. (1973a). This section therefore will pro-
vide detailed descriptions only of the new equipment and modifications
in previously existing hardware. These include a heat exchanger for
vaporizing the liquid fuel, a water-cooled gas sampling rake for
exhaust plane measurements, and the addition of an ultraviolet nitrogen
dioxide analyzer. For convenience a brief recapitulation of the
entire gas turbine combustion facility will be presented; a schematic
is shown in Fig. 2-1.
The test cell hardware, including the combustor with all of its
support systems, and the probes and rakes will be described in the
first portion of this section. The second portion will be devoted
to the control room instrumentation used to monitor the pollutant
concentrations in the sample gas.
A. Test Cell Hardware
1. Air System
The blowdown type air system had a capacity of 85 cu m and a maxi-
mum pressure of 164 atm. This could provide an air flow rate of 2.72 kg/sec
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Air System
Fuel Svstem
Heating
Combustor
Fuel Svstem
T-56 Test
Combustor
Probe Addition Section
Back Pressure
Valve
Exhaust
Sarple Out
from Water-cooled
Probe or Rake
Fieure 2-1. Complete combustion facilitv schematic
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(6 Ib/sec) for 40 minutes or 2.04 kg/sec (4.5 Ib/sec) for 60 minutes.
Air drying kept the dew point of air entering the first or heating
combustor nearly constant at -57°C; the inlet temperature was approxi-
mately 0°C. The air flow rate was measured with a differential
pressure, orifice type flowmeter and was controlled by a pneumatically
operated air throttle valve.
2. Fuel System and Injectors
Commercial grade propane was used for fuel and forced to each
combustor from pressurized delivery tanks. Flowrates to each combustor
were separately controlled by manual flow control valves and were
measured using Potter turbine flowmeters. The fuel supply system used
for the liquid fuel portion of the experiments was the same as that
described by Mellor et al. (1972a) and Tuttle et al. (1973a).
For the gaseous fueled experiments (exit plane measurements only),
propane vapor was supplied to the test combustor by inserting a heat
exchanger, located directly in the J-33 heating combustor, between
the flowmeter and the test combustor injector. This heat exchanger was
constructed of .95 cm diameter stainless steel tubing wrapped in the
shape of a cylindrical helix with an outside diameter of approximately
8.9 cm. Liquid propane flowed through the combustor housing, through
the 9 coils of the heat exchanger, where it was vaporized, and back out
through the combustor housing. The gaseous propane would then flow to
the test combustor where, just before being injected, its temperature
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and pressure were measured to determine if it were indeed a vapor.
The temperature was monitored with a chromel-alumel thermocouple
mounted through the side of the fuel line. The pressure transducer
was a variable resistance type device that gave a millivolt output
which was a linear function of pressure for the range of interest.
The position of the heat exchanger as well as the location of the
temperature and pressure transducers can be seen in Fig. 2-2.
The test combustor was fitted with a standard T-56 fuel nozzle
for the injection of liquid propane; however, in order to maintain
the same mass flow rate of propane vapor a special nozzle of larger
exit area was constructed. This nozzle was designed to match the
operating characteristics of the standard T-56 nozzle as closely as
possible for vapor fuel mass flowrate. The liquid nozzle injected
fuel very near to the combustor centerline at a half-angle of 52.5°;
since the vapor nozzle orifices were 0.7 cm off the centerline, a
half-angle of 41° was used to match the spray trajectory reasonably
closely. The vapor nozzle was machined from hexagonal stainless
steel stock. The outside physical dimensions of this new nozzle were
identical to those of the standard T-56 nozzle. This allowed them to
be easily interchanged since they had identical threads. Fig. 2-3 is
a drawing of the vapor fuel nozzle, showing all pertinent dimensions.
3. Combustors and Igniters
For the internal measurements, two Allison T-56 turboprop com-
bustors were connected in series by a diffuser section as shown in
-------
Fuel Inlet
Point of Temperature and
Pressure Measurements
Heating Combustor
Test Combustor
Figure 2-2. Schematic of vanorizer
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^
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r
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03 >
.3.89->
12 Equispaced Holes
1.59 01a.
Figure 2-3. Details of vapor fuel nozzle (all dimensions in millimeters)
-------
10
Fig. 2-1. This arrangement used the exhaust of the first or heating
combustor to supply heated vitiated inlet air for the test combustor.
The change to the T-56 rather than J-33 heating combustor for the
internal measurements decreased the emissions in the vitiated air
for the operating point of interest. The standard fuel nozzles and
spark igniters were used in the heating combustors at all times.
Fither the T-56 spark igniter or a methane-oxygen torch type
igniter was used for the T-56 test combustor. The igniters for both
T-56 liners were mounted through the holes designed for them and all
cross-over tube openings were patched.
4. Probe and Probe Positioner
A water-cooled stainless steel probe was inserted into the com-
bustor through the 45° elbow section as shown in l;Lg. 2-1. The body
of the probe was made of three concentric tubes: sample flowed in
the innermost tube, the second was an exit for high pressure cooling
water, and the outer was the cooling water inlet. The gas sample
entrance to the probe was slightly converging as opposed to converging-
diverging in order to maintain mechanical integrity and minimize
blockage by soot. The use of the slightly converging tip as well as
the cooling action of the high pressure water was relied upon to quench
any sample gas reactions.
Local gas temperature estimates were attempted by mounting a
platinum/10% platinum rhodium (.0635 cm wire, MgO insulation, inconcl
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11
sheath) thermocouple to the side of the probe. The .32 cm outside
diameter thermocouple was mounted through holes in "hair-moon"
shaped sections welded to the side of the probe body. The exposed
junction was positioned at about. .16 an ahead of the probe tip.
However, the environment of the T-56 liner proved too severe for
temperature determinations via this technique, and most probing was
accomplished without the thermocouple.
The probe positioning system had two degrees of freedom.
Different radial positions could be sampled as the probe was rotated
since the probe tip was offset from the probe centerline by a
distance of 3.05 cm. The probe was also moveable in the direction
parallel to the combustor axis via a translating carriage which
was remotely moved via a worm gear-electric motor combination. A
complete description of the probe and its positioning equipment can
be found in Mellor et al. (I972aj and Tuttle et al. (1973a).
5. Uncooled Gas and Temperature Rakes
Emissions and gas temperature from the heating combustor were
monitored with two uncooled rakes mounted just upstream of the
test combustor. The temperature rake consisted of eight unshielded,
chromel-alumel thermocouples mounted across the duct in ceramic
insulators through holes in the point of a stainless steel "V" bar.
The thermocouple lead wires were channeled through the "V" bar which
was then filled with ceramic cement to protect the leads from the hot
gases.
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12
The gas sampling rake was a stainless steel "cross" made of
.95 cm diameter tubing. Four sample holes of .16 cm diameter were
located across each spoke so as to give an area averaged sample. No
provision was made for water cooling since the temperatures of the
exhaust gases of the heating combustor were sufficiently low (590°K
maximum) that reaction quenching should have occurred upstream of
the rake. Both the gas sampling and temperature rakes are described
more fully by Tuttle et al. (1973a).
6. Water-Cooled Gas Rake
Area averaged pollutant emissions measurements at the exit plane
of the test combustor were obtained through the use of a water-cooled
gas sampling rake. This rake was mounted through the window in the
elbow section (Fig. 2-1) in place of the previously discussed water-
cooled probe.
Like the upstream rake, the water-cooled rake shown in Fig. 2-4
was in the shape of a cross. Four stainless steel spokes extended
from a central hub. Each spoke was machined from stainless steel stock
and then enclosed in 1.27 cm diameter stainless steel tubing which
served as a flow passage for the cooling water. Four gas sampling
holes, each .16 cm in diameter, were located along each spoke so as
to give an area averaged sample. The internal gas path running from
the outermost hole on each spoke to the hub was .38 cm in diameter.
From the back of the hub, two concentric stainless steel tubes, .95 cm
diameter and 2.54 cm diameter, extended out through the window in the
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/
O 0 0 ° (
V
o
0
0
o
o
0
o
(4 per spoke)
\
JO 0 0 O
X
Figure 2-4. Schematic of gas sampling rake
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14
elbow section. Sample gas flowed from each spoke through the Inner
tube to the analyzing equipment. The outer tube provided a path for
high pressure cooling water to flow to the hub and then outward the
length of each spoke where it was dumped into the combustor housing
through holes on the downstream side of each spoke at its tip. The
internal structure of the water-cooled gas sampling rake can be seen
in Fig. 2-5.
7. Back Pressure Valve
Combustor pressures as high as 10 atm were obtained through the
use of a back pressure valve (described in detail by Mellor et al.,
1972a), which consisted of a conical centerbody which could be moved
into an orifice to reduce the available exhaust area. The position of
the centerbody was controlled by air pressure supplied to three air
cylinders attached to it. To protect it from the hot exhaust gases,
high pressure water was forced through holes in the cone, covering
it with a protective film of cooling water.
B. Control Room Instrumentation
Instruments were used to measure concentrations of CO, NO, N0?
and unburned hydrocarbons (HC). Fig. 2-6 shows the relative position
of each analyzer in the flow system. Sample flow could be extracted
from either the test combustor probe/rake (only one could be used at
a time) or the upstream inlet air rake, by proper operation of solenoid
-------
15
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iiiriifffifft r r
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Figure 2-5. Sanple gas flow path within water-cooled rake
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From Test Combustor
Purge System
^-il
2^ I
Relief
Valve
By pass
Flow-
FT owmeters
NO
Detector
CChem.)
Vacuum
Pump
Analyzer
CNDUV)
I
CO
.Analyzer
CNDIR)
Diluent
Heated
Line
HC
Analyzer
(FID)
Figure 2-6. Schematic of gas handling system
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17
valves. Sample transit time through the all stainless steel line
from the combustor to the analyzing instruments was on the order of
1 sec. All measurements were made on a wet basis.
CO concentrations were measured using a Beckman Model 315A
(short path) NDIR (nondispersive infrared) analyzer. The combina-
tion of three electrometer ranges and two stacked sample cells
(.32 cm and 24.3 cm) gave the CO analyzer a total of six different
sampling ranges, with the most sensitive range 0-250 ppm and the
least 0-20% CO. The repeatability for the NDIR measurements was
guaranteed to 1% of full scale reading by the manufacturer.
The nitrogen oxide concentrations were continuously monitored
using a chemiluminescent analyzer constructed to the specifications
of Fontijn et al. (1969, 1970). The instrument gave a linear output
signal for NO concentration greater than .5 ppm and a response time
of about 45 sec.
Unburned hydrocarbons were measured by flame ionization with a
Beckman Model 402 Total Hydrocarbon Analyzer. All hydrocarbon readings
are reported as ppmC. Various electrometer ranges gave the instrument
a measurement span of 1 to 50,000 ppmC. Response time for the hydro-
carbon analyzer was about one sec.
A Beckman Model 255B (long path) NDUV (nondispers i.ve ultraviolet)
analyzer was used to continuously monitor the N0? concentration Ln the
Lt
sample gas. The analyzer section used a sample cell 88.3 cm in length
for a range of 0-100 ppm. Repeatability and accuracy were guaranteed
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18
by the manufacturer to be ± 1%. Concentrations of NCL greater than
100 ppm were measured by diluting the sample with nitrogen in a metering
manifold. Fig. 2-6 shows schematically the specific NO- flow system.
Sample flow rate through the N0~ detector was maintained at 1600 cc/min.
This flow rate was sufficient to purge the sample cell such that the
response time of the instrument was on the order of 10 sec.
Calibration of all instruments using appropriate span gases was
performed before, during, and after each run. Nitrogen was used for
zero gas. As a check of both the NDUV and the 88 ppm NCL in N? span
L-i LJ
gas available during the present study, a known concentration of NO
X
was prepared in a stainless steel tank by diluting NO with air. Sample
then flowed from this tank to both the chemiluminescent NO detector
and the NDUV. As the NO was oxidized to N02 by the air, the actual
concentration of NCL could be calculated by subtracting the measured
amount of NO from the known and constant NO . In this manner a call-
.A.
bration curve for the NDUV could be constructed and compared to that
supplied by the manufacturer. Both this latter curve and the N0? span
gas analysis were substantiated by this procedure. However, as noted
in Section I, soot particle interference in the NDUV made impossible
any quantitative measurements of NO™ (see Tuttle et al., 1973c) , even
though the recommended techniques for sample filtering were used. Thus
no N0? emissions are reported in Section III.
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19
III. RESULTS AND DISCUSSION
For the Allison T-56 combustor examined in the study, Fig. 3-1
shows the relative size and position of the air addition and dilution
holes and the location of the four corrugated circumferential film
cooling slots. Unseen in the figure is a static ring located at the
periphery of the liner dome which also acts as a film cooling slot.
Note that air addition to this liner is accomplished primarily via
film cooling, as shown in Fig. 3-2.
Gas samples were taken from nine different axial planes within
the combustor and at the combustor exit plane. The location, relative
to the injector tip, of each of the ten sampling planes is shown in
Fig. 3-2. The 27.3 cm and the 32.7 cm planes are directly in line
with large air dilution holes while the 5.82 cm plane is aligned with
a row of smaller air addition holes. As mentioned previously, different
radial positions at any plane could be sampled as a result of the probe
tip being offset from the probe centerline. Fig. 3-3 is a view,
looking upstream from the combustor exit, of the circular trace that
the probe tip made as it was rotated within the combustor. The radial
points labeled 1 through 6 are the positions at which samples were
taken. Point 1 is closest to the combustor wall and aligned with the
penetration jets at 5.8, 14.8 and 27.3 cm, while point 4 is on the
liner centerline. Point 2 is aligned with the jets at 10.5 and 32.74 cm
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bo
a
Figure 3-1. T-56 combustor configuration
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21
100-
75
50-
25-
Figure 3-2. Axial sampling planes and T-56 air flow split
(Dimensions are in centimeters measured from injector)
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22
>• Aligned with three penetration jets
,_ _ v. Aligned with two penetration jets
Figure 3-3. Location of radial sampling points
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23
A. Combustor Operating Points and Inlet Air Quality
Five different combustor power settings were examined in the
study. The pertinent operating parameters used for each power
setting are listed in Table 3-1. Also listed are nominal values for
design operating parameters as extracted from BastianellL (1970).
Burner inlet temperatures were calculated from data for turbine inlet
temperature, fuel to air ratio, air flow rate, and fuel heating value,
assuming complete combustion.
It is important to examine the extent to which the vitiated inlet
air used in this study deviated from standard air. If this difference
is too great, the combustor pollutant formation characteristics could
be significantly changed from those of an actual gas turbine. Vitiated
inlet air creates another problem in that it becomes impossible to
distinguish between pollutants which are actually formed in the test
combustor and those which enter with the inlet air.
The approximate composition of the test combustor inlet air can
be determined by assuming a chemical reaction in the slave burner of
the following form:
C3Hg + 40 02 + 150 N2 + 3 C02 + 4 H20 + 35 QZ + 150 NZ + 8.26 x 10~3
CO + 2.68 x 10"3 NO + 4.03 x 10~3 HC
The molar 09/fuel ratio of 40 in the above reaction was that used in
LJ
the J-33 slave burner for the 100% normal run condition (Table 3-1) using
liquid C,HR for fuel. The air flow rate was 2.40 kg/sec and the test
•3 O
-------
Table 3-1. Test Combustor Operating Points
Power
Setting
Low Speed
Ground Idle
Ground Idle
Flight Idle
75% Normal
100% Normal
Designation
LSGI
GI
FI
75%
100%
Overall
lence
.202
.122
.162
.24
.299
Equiva-
Ratio
b
.1654
.112
.149
.22
.268
Airflow Rate
(kg/sec)
Present Bastianelli
Study (1970)
1.51
2.40
2.40
2.40
2.40
1.13
2.46
2.51
2.51
2.51
Combustor Pressure
(atm abs)
Present Bastianelli
Study (1970)
5.87
8.13
8.85
9.72
9.63
3.5
7.7
—
8.93
9.44
Burner Ii
Temperati
°K
394
544
522
566
584
13
Calculated for CJ-L as fuel, following Zucrow and Warner (1956) and corrected for vitiated inlet air.
^Calculated after Bamett and Hibbard (1956) .
-------
25
combustor inlet temperature was .r>84°K. The concentrations of pro-
ducts CO, NO and HC (as ppmC) were measured experimentally and arc
small enough to balance the reaction assuming complete combustion.
For the internal measurements at the same operating point, but using
the T-56 as the heating combustor, the corresponding mole numbers of
CO, NO, and HC were typically 6.3 x 10~3, 1.65 x 10~3, and 1.6 x 1(T2,
respectively.
The mole fractions of 0? and N? on the product side of the above
Li Li
reaction are .182 and .781 respectively. This is a decrease from
standard air of .73% for N7 and 12.6% for 0?. It is felt that the
t~i L>
magnitude of these differences does not significantly alter the com-
bustion process in the test combustor from that which occurs with
nonvitiated air.
When gaseous propane was burned in the test combustor for ex.it
plane measurements, placement of the prevaporizing coil in the J-33
heating combustor caused its pollutant emissions to change as a re-
sult of the quenching action of the coil on the burner flame. The
magnitude of this change can be seen in Table 3-2 which lists emissions
of the heating combustor with and without the vaporizing coil for
each power setting. Note that 11C shows the most significant variation.
In an attempt to separate the influence of changing inlet gas
composition from that of change In fuel phase for the test combustor,
the term "net emissions" will be used in the following discussion of
exhaust plane measurements. New emissions is defined simply as the
pollutant concentration measured for the test combustor less that of
-------
Table 3-2. Heating Combustor Emissions
With and Without Prevaporizing Coil
Power
Setting
Low Speed
Ground Idle
Ground Idle
Flight Fdle
751 Normal
100% Normal
HC (ppmC)
Without With
56
41
33
22
21
260
131
196
211
317
CO (
Without
74
66
69
41
43
ppm)
With
98
69
62
59
77
NO (ppm)
Without Wit
5
9
9
12
14
9
12
9
13
12
vitiated inlet air and will correspond to emissions formed in the
test combustor only if the incoming pollutants remain unchanged.
Any oxidation of incoming CO or HC will result in a net emissions
value which is a low estimate of the test combustor pollutant forma-
tion. The use of net emissions values for NO is probably more accurate.
The T-56 combustor, because of the way its air addition holes
are arranged, lends itself well to using net emissions to study pollu-
tant formation trends. 54.4% of the effective area for air addition
directs this cooling air parallel to the combustor axis along the wall
(Fig. 3-2) and results in relatively little mixing of this cool air with
the hot gases of the central core. Such a flow configuration is optimal
for using the term net emissions since it presents the least opportunity
for incoming CO or HC to be oxidized.
Uniform inlet air properties were assumed on the basis of tempera-
ture measurements made during each run. The inlet air was sufficiently
-------
mixed such that the maximum temperature difference between any two
points across the duct d:iameter, as measured by the thermocouple rake,
was typically less than 10°K.
B. Combustor Exhaust Plane Measurements
The water cooled area averaging sampling rake was positioned
approximately 3 cm downstream of the combustor exit (39.3 cm plane in
Pig. 3-2) in order to investigate the change in combustor emissions
with change in fuel phase. Recall that for these experiments a J-33
combustor was used as a slave burner to heat the inlet air and
vaporize the fuel. Data were first obtained using a standard T-56
pressure atomizing nozzle and liquid propane. Similar measurements
were then made using propane vapor and the simple nozzle described in
Section If.
1. Carbon Monoxide and Unburned Hydrocarbons
The resulting data for carbon monoxide and unburned hydrocarbons
are presented in graphical form in Fig. 3-4 and 3-5. Concentrations
of CO or HC net emissions are plotted for liquid and vapor fuel at
each power setting; since the trends exhibited by these species are
similar, they will be discussed simultaneously. An arabic numeral
adjacent to a data point indicates the number of overlapping determina-
tions. Also shown on the figure are data reported by Hare et al. (1971)
and averaged results of Vaught et al. (1971), both using aviation fuel
and sampling at the engine exhaust.
-------
28
-
360-
-
320-
280'
240.
200'
1 16°-
g
• H
03
JH H
S
O
g '
8 so-
40.
0-
-40-
XA 4- - vapor C-rlln
• - Liquid ('-rH,,
X - "are ct al . (19 71")
£ - Vaught et al . (1971) "
+
B
4-
•
•
4-
B
+ 4-
+ •
? ; •
is??
" •
•
LSGI
GI FI 75%
Power Setting
Figure 3-4. Net CO concentrations versus power setting
-------
360
320
280
concentration
240
200
160 -
120 -
80 -
40 -
-40
29
+
X
— Vapor C,HQ
_ Liquid CJ-L
~ flare et al. (1971)
- Vaught et al. (1971)
,
+
-2 X
4-
LSGI
100 °
GI FI 75%
Power Setting
Figure 3-5. Net HC concentrations versus power setting
-------
In view of the data scatter (resulting in part from the use
of net emissions), no discernible change in the emissions is observed
as liquid propane is changed to vapor. At ground and flight idle,
the vapor measurements are perhaps greater than the liquid measure-
ments but the difference is slight. At all other power settings, no
significant differences between net emissions for liquid or vapor
propane are evident.
The concentrations reported by the other investigators fall
in the middle of the data obtained with propane fuel for the ground
and flight idle conditions. Nearer design operating conditions, at
75 and 100% normal, the net emissions for propane are greater than
those of Vaught ct al. (1971) and Hare et al. (1971). The opposite
is true at low speed ground idle where the other experimenters
obtained values substantially higher than those for propane fuel.
The discrepancies at the 75 and 100% normal run conditions de-
scribed above are thought to be a result of differences in sampling
location. Results of internal sampling, to be presented in Section
C, show that CO and HC oxidation is not quenched at the combustor exit
plane. Thus samples taken at an/ downstream location, as were those
of Vaught et al. (1971) and Hare et al. (1971) , show a lesser CO and
IIC concentration due solely to oxidation. For the manner in which the
combustor is mounted in an actual engine, the burned gases require
about 2.7 msec to flow from the position defined in the present study
as the combustor exit plane to the turbine inlet and quenching.
-------
7,1
The low values of CO and HC net emissions at low speed ground
idle are thought to be a result of two factors. First, Table 3-1
shows that the equivalence ratio and combustor pressure used in the
present experiments for this power setting are both larger than
those used in the actual engine; both of these increases would be
expected to increase the oxidation rate of HC and CO and result in
the lower indicated emissions.
Another factor which could account for this discrepancy is due
to the present use of net emissions. The decreased air flow rate at
low speed ground idle (Table 3-1) may allow via the increased mean
combustor residence time substantial oxidation of the HC and CO in
the incoming vitiated air. The values reported in Fig. 3-4 and 3-5
as test combustor net emissions would then be low as a result of
attributing too large a fraction of the total test combustor pollutants
to the vitiated inlet air. The occasional appearance of negative net
emissions in the figures emphasizes difficulties with this concept.
For the present study, as shown in Table 3-1, in going from
ground idle to 100% normal the most significant variation in engine
operating parameters is the increase in overall equivalence ratio or
fuel flow rate. This is accomplished by an increase in fuel differ-
ential injection pressure across the pressure-atomizing duplex T-56
nozzle or the simplex fuel vapor nozzle. It has been postulated pre-
viously that near design the turbine combustion process resembles
that of a turbulent diffusion flame of fixed length (Mellor, 1973),
and the observed increases in HC and CO with increasing differential
-------
32
pressure result from a relatively constant amount of HC and CO oxida-
tion obtainable in such a flame. A similar trend is not seen in
the engine exhaust measurements of Vaught et al. (1971) and Hare
et al. (1971) because of the oxidation noted above.between the com-
bustor and engine exit planes.
2. Nitric Oxide
Values of NO net emissions are presented in Fig. 3-6 for each
power setting for liquid and gaseous propane. The corresponding data
of Hare et al.,(l971) and Vaught et al. (1971) are tabulated separately
in Table 3-3 due to the large differences in magnitude. Except for
low speed ground idle, all of the NO net emissions for propane fuel
are substantially less than all of the NO data taken downstream at
the engine exhaust with aviation fuel.
The possibility of significant NO formation downstream of the
combustor exit plane seems slight since the maximum temperature measured
there in the present investigation was approximately 1500°K. Also,
earlier work of Cornelius et al. (1957) measured zones near the exit
of a T-56 liner at temperatures of 1900°K using JP-5 for fuel at the
military power setting. The low values of NO net emissions for propane
must then be due to something else, perhaps fuel characteristics.
A correlation for NO emissions based on results from a penetration
jet cooled combustor using liquid propane was developed previously
(Mellor, 1973). The correlating parameter is Ap/V ,., fuel differential
-------
33
20
16
12
8
PU
O
•P
CO
t 4"
§
O
u
0 "
-
-4 .
-8 -
-in .
+ "Vapor C7H0
MM ^
B —Liquid CJHg
+
. - i * .
• a •
* : *
4-
B
4- ^ " •
"*" 4- +
4- -*-
+
LSGI
GI FI 75%
Power Setting
100%
Figure 3-6. Net NO concentrations versus power setting
-------
Table 3-3. NO from T-56 Engines
(from Vaught et al., 1971 and
Hare et al., 1971)
Power Setting
11 are
et al.
(1971)
a
NO Concentration (ppm)
Vaughth
et al.
(1971)
Vaught
ct al.(
(1971)
Low speed
ground idle 9
Ground idle
Flight idle
751 normal 61
100% normal 93
23
30
42
85
119
a) Measured via chemiluminescent technique.
b) Measured with NDIR instrument.
c) Measured via chemiluminescent technique.
17
21
32
68
100
injection pressure divided by a reference air velocity through the
combustor, and is interpreted as T /T , , the ratio of some character-
X &J cU
istic fluid residence time to the fuel droplet lifetime.
Calculations of droplet evaporation times were made to determine
the difference between the lifetimes of an 80 micron droplet of C,HO
and the same size drop of JP-5 in the same convective conditions. It
was found that at an air temperature of 1500°K the propane droplet
evaporated in .6 msec, the JP-5 droplet in 1.2 msec; at lower air
temperatures, this difference becomes greater.
-------
Mellor (1973) determined that at high values of T , NO is high
since drops may burn at stoichiornetric; as T , is reduced, NO emis-
sions decrease and are determined primarily by T which becomes
I \$J
large compared to T ,
The data for NO in Fig. 3-6 and Table 3-3 are consistent with
this idea. The shorter evaporation or combustion time for liquid
propane results in NO emissions which are lower than those for
aviation fuel. The low value for T , is also responsible for the
fact that little difference is seen in Fig. 3-6 for liquid or vapor
propane; the values for vapor fuel (T , = 0) arc however generally
slightly lower which is consistent with the above argument. Tt follows
that, although little change was seen going from liquid to prcvaporized
propane, the same procedure using JP-5 could result in large reductions
of NO.
Finally, the independence of net NO emissions on load (or differen-
tial fuel injection pressure) between ground idle and 100% normal shown
for propane fuel in Fig. 3-6, as opposed to the trends exhibited in
Table 3-3, also suggest that heterogeneous processes are much less
important for liquid propane than for aviation fuel (see Mellor, 1973).
3. Summary
Measurements of CO, HC and NO area averaged net emissions were made
at the exit of a T-56 combustor for both liquid and vapor propane fuel
at various power settings; little if any difference in pollutant character-
istics was observed for the change of fuel phase.
-------
36
The data for propane were then compared to data available in
the literature for measurements made at the engine exhaust burning
aviation fuel. The following differences were observed: at design
operating conditions CO and HC emissions were higher for propane,
at low speed ground idle the opposite was true, and the NO data for
propane were consistently lower.
The first trend is thought to be due to CO and HC oxidation
continuing downstream of what was termed the combustor exit plane
in the present experiments. The low values of HC and CO at low
speed ground idle are thought to result from possible collapse of
the assumptions used for net emissions (no oxidation of pollutants
in the vitated inlet air) and from the fact that the pressure and
overall equivalence ratio used at this power setting were somewhat
higher than those of the other investigators.
The differences in NO net emissions were found to be con-
sistent with the model of spray combustion of Mellor (1973) . The
low value of evaporation or combustion time for propane resulted in
low values of NO net emissions. This is also the reason for no signi
ficant changes in NO emissions when the propane was vaporized prior
to injection. It was concluded that, due to the greater times
required for evaporation of aviation fuels, prevaporization of such
fuels could lead to reductions in NO combustor emissions.
-------
C. Internal Measurements
Local concentrations of carbon monoxide, unburned hydrocarbons
and nitric oxide were measured at each of the internal points de-
scribed in Fig. 3-2 and Fig. 3-3 by means of the water cooled single
point probe. Attempts at estimating gas temperatures were discontinued
after the inconel sheath of the platinum/10% platinum rhodium thermo-
couple failed several times while the probe was in radial position 2
of Fig. 3-3.
All of the internal data were taken with the T-56 combustor
operating at the 100% normal mode (combustor pressure of 9.63 atm,
inlet temperature of 584°K, air flow rate of 2.4 kg/sec and overall
equivalence ratio of .299, corrected for vitiated inlet air). Liquid
propane was the fuel, and a second T-56 liner served as the slave
burner.
The usual procedure for internal sampling was to start with
the probe at the plane nearest the injector and at the desired radial
position. It would then be withdrawn, keeping the radial position
constant and stopping at each sampling plane. If the entire capacity
of the air system was available, a complete axial traverse of the
combustor could be made during one run.
1. Flow IVbdel
Axial profiles of HC, CO, and NO at the various radial points
-------
38
are presented in the Appendix. Here we shall limit our attention
to the qualitative flow model which results from detailed study of
these data and which is presented as Fig. 3-7; the numbered regions
in the figure correspond to the zones as discussed below.
1. Region 1 is that of the hollow cone liquid fuel spray;
it is bent toward the combustor centerline as a result of the swirled
air flow through the dome and the high combustor pressure.
2. High HC, CO, and NO characterize region 2, which is the
base of the main reaction zone extending through region 3 and closing
to the centerline in region 5. Combustion in region 2 occurs with
the dome and dome slot air as well as film cooling air from the
slot at about 6.5 cm.
3. Mixing of the now vaporized fuel with the film cooling air
from the downstream slots allows combustion to continue into this
region in a configuration resembling a turbulent diffusion flame.
4. Region 4 is the centerline recirculation zone, embedded
within the diffusion flame and defined by relatively constant con-
centrations of HC, CO, and NO.
5. The recirculation zone ends just upstream of region 5, and
thus the flame zone collapses to the centerline of the combustor. In
this region HC and CO oxidation, .and NO formation begin in earnest.
This region also corresponds well with the zone of maximum temperature
reported by Cornelius et al. (1957) for the T-56 liner at a similar
operating point but burning JP-5 (cf. Fig. 3-8).
-------
Radial
Point
4
3 ,5
6
I
QrO-
36.42
-Axial Planes (on. from injector)
Figure 3-"\ Schematic of 1-56 flow model
-------
Figure 3-8. Temperature contours of Cornelius et al., (1957) i
, in deg K
-------
41
6. HC anc CO oxidation and NO formation continue as the flame
spreads across the combustor cross-section, but a core of 11C and CO
persist near the centerline and continue to react downstream of the
combustor.
The area-averaged species concentrations at the various axial
planes, presented in Table 3-4, are generally consistent with Fig.
3-7. HC increases at the first four stations, as the fuel vaporiza-
tion rate exceeds its oxidation rate. NO formation in the base of
the turbulent diffusion flame in this same region is substantial,
Table 3-4. Area-averaged Emissions at
Various Axial Planes
AxJal Plane,
on
3.27
5.80
7.65
13.40
17.98
21.23
24.29
27.30
32.70
36.40
39 . 30b
1 1C,
ppmC
1708
3493
5492
10,059
9456
10,165
8904
3922
1587
686
131b
CO,
ppm
9833
9395
9300
11,081
9726
11,665
12,159
10 , 332
4787
2677
30 8b
NO,
ppm
61.4
46.5
38.3
21.3
21.6
27.2
32.8
28.3
35.5
38.1
16. Ob
Calculated from individual data points given in the Appendix.
Measured via the water-cooled rake.
-------
42
but subsequently the area-averaged concentration decreases due to
dilution by the cooling air. At 18 cm, NO formation increases
sharply, followed by HC oxidation at 21 cm and CO oxidation at
24 cm. Also shown in the table are the values obtained at 39 cm with
the area-averaging water-cooled rake during the combustor exhaust
plane measurements. Although the HC and CO concentrations seem
reasonable, NO seems low by at least a factor of two: the cause of
this discrepancy is unknown, but probably results from the rake's
sampling from all four quadrants of the asymmetric liner, while only
one quadrant was accessible to the probe.
2. Summary
Results of the interal measurements within the primarily film-
cooled Allison T-56 combustor operating near its design point arc
generally consistent with the physical model of spray combiistion
(Mellor, 1973) developed for the penetration jet-cooled J-33 liner:
at design the primary reaction zone resembles a turbulent diffusion
flame, extending well into the secondary and dilution zones of the
combustor, and surrounding a centerline recirculation zone which is
established by the swirl imparted to the dome air. Although liquid
fuel is fed to this flame, average drop lifetimes are sufficiently
small that turbulent mixing controls the combustion process and
emissions of NO (cf. Mellor, 1973).
The similarity of the T-56 flame to the classical turbulent jet
-------
flame is enchanced by the predominant use of film cooling air, which
defines the outer boundary of the flame in the 3 to 21 on region;
the penetration jets of the J-33 liner distort the axisymmetric
character of its flame (see Mellor et al. 1972a,b and Tuttle et al. ,
1973a,b). Some of these penetration jets also flow upstream into
the centerline recirculation zone, and thus in the J-33 this zone
is found nearer to the injector. Likewise, the poor mixing obtained
as a result of this use of substantial film cooling air causes reaction
to continue beyond the combustor exit plane of the T-56 liner. Exhaust
plane measurements with the latter combustor confirm these downstream
reactions and that near the engine idle point injector performance in
large part determines the emissions.
-------
l\l\
TV. PUTlIRE EFFORTS
fJxperimental results obtained from gas sampling within or near
the exit plane of the Allison T-56 combustor generally substantiate
the two-part physical model of spray combustion (Mellor, 1973) , as
was noted in Section TIT. One of the key elements of this model is
the liquid fuel droplet lifetime, which is determined largely by the
characteristics of the fuel nozzle in use. However, it is of interest
to define in a more precise and systematic way how injector design
and operation affect the type of spray combustion and emissions which
result.
One possible method of proceeding would be to select a combustor
can and determine exhaust emissions as a function of injector type and
differential fuel (and air for the airblast nozzle) injection pressure.
However, since the impetus for the work is injector behavior rather
than the aerodynamics of the combustor can, this type of study is inap-
propriate.
Thus, a simpler aerodynamic flowfield will be used so that the
injector effects will not be so masked: the arrangement consists of
a disc flame stabilizer, with the liquid fuel injector mounted at Its
center (McCreath and Chigier (1973) have recently studied spray com-
bustion (not emissions) for one type of pressure atomizing nozzle
with this type of stabilizer). Because the aerodynamics of disc
stabilization are reasonably well known from ramjet technology (see
i
for example Davies and Beer, 1971), the ratio of disc diameter to
-------
45
combustor housing diameter can ho chosen to optimize flameholding.
Note that the flow field established by the disc consists of
a recirculation zone similar to the centerline recirculation zone
used for flameholding in a turbine engine. However, the aerodyna-
mics are much simplified because there is no swirl and no discrete
addition of air through film cooling slots and penetration holes.
In addition, there is no liner to obstruct visual and photographic
observation of the flames. Thus it should be possible to isolate
the influence of injector type and design on not only the spray
combustion, but also the emissions.
Turbine cycle parameters which will be varied independently
are inlet air temperature, pressure, air flow rate, and differential
fuel injection pressure (equivalence ratio variation can be accomplished
via this technique or constant equivalence ratio can be maintained
by appropriate variation of the air flow rate) . In addition, several
types of nozzles will be studied. To simplify the experiment somewhat,
initial work will use pressure-atomizing simplex injectors, to be
followed by duplex injectors. Finally, various types of air-assist
and airblast injectors will be investigated.
For each injector studied, initial measurements will consist of
area-averaged emissions of IIC, CO, and NO, obtained via the water-
cooled stainless steel gas sampling rake mounted near the exhaust of
the test section. Photographic methods will be used as well via win-
dows to be mounted on a new test section.
-------
46
After these survey measurements are made, run conditions will
be selected at which potentially useful information about the
emissions and spray combustion can be obtained. The gas sampling
probe with a side-mounted Pt/PtRh thermocouple will be used to map
out local concentrations of the pollutants itemized above, as well
as estimates of local gas temperatures. In this way significant
understanding of the spray combustion process and its formation and
destruction of pollutants can be obtained.
-------
47
LIST 01-' ly-J-'liW-NCBS
Altenkirch, R. A. and Mellor, A. M., 1973, "Emissions and performance of
gas turbine liners. I: Stability," Report NO. PURDU-CL-73-05, School
of Mech. Eng., Purdue Univ.
Appleton, J. P. and Heywood, J. B., 1973, "The effects of imperfect fuel
air mixing in a burner on NO formation from nitrogen in the air and the
fuel," 777-786, Fourteenth Symposium (International) on Combustion, The
Combustion Institute, Pittsburgh. ' "~
Bamett, H. C. and Hibbard, R. R., 1956, "Properties of aircraft fuels,"
NACA TN 3276.
Bastianclli, D., 1970, "Typical dynamometer characteristics of Series III
T-56 production power sections from February 1967 to December 1969,"
Detroit Diesel Allison Technical Data Report TDR AR 0031-159.
Bowman, C. T. and Cohen, L. S., 1973, "Nitric oxide formation in turbu-
lent methane-air flames stabilized on bluff-bodies," Abstracts from
1973 Technical Meeting of the Combustion Institute, Eastern Section,
Montreal.
Cornelius, W., Burwell, W. G., and Turunen, W. A., 1957, "Progress report
on fundamental gas turbine combustion studies," General Motors Research
Memoranda, 1957-1959.
Davies, T. W. and Beer, J. M., 1971, "Flow in the wake of bluff-body flame
stabilizers," 631-638, Thirteenth Symposium (International) on Combustion,
The Combustion Institute, Pittsburgh.
Fontijn, A., Sabadell, A. J., and Ronco, R. J., 1969, "Feasibility study for
the development of a multi-functional emission detector for air pollutants
based on homogeneous chemiluminescent gas phase reaction," TR-217, Aero-
Chem Research Laboratories.
Fontijn, A., Sabadell, A. J., and Ronco, R. J., 1970, "Homogeneous chcmi
luminescent measurement of nitric oxide with ozone," Anal. Chem. 42, 575.
Hare, C. T., Dietzmann, H. E., and Springer, K. J., 1971, "Gaseous emissions
from a limited sample of military and commercial aircraft turbine engines,"
Report AR-816, Southwest Research Inst.
McCreath, C. G. and Chigier, N. A., 1973, "Liquid spray burning in the wake
of a stabilizer disc," 1355-1363, Fourteenth Symposium (International) on
Combustion, The Combustion Institute, Pittsburgh. ~~
-------
Mellor, A. M., Anderson, R. D., Altenkirch, R. A., and Tuttle, J. H.,
1972a, "Emissions from and within an Allison J-33 combustor," Report
No. PURDU-CL-72-1, School o£ Mech. Eng. , Purdue Univ.
Mellor, A. M., Anderson, R.! D., Altenkirch, R. A., and Tuttle, J. H.,
1972b, "Emissions from and within an Allison J-33 combustor," Comb.
Sci. Tech. 6_. 169.
Mellor, A. M., 1973, "Simplified physical model of spray combustion in
a gas turbine engine," Comb. Sci. Tech. 8_, (3).
Mellor, A. M., 1974, "Spray combustion from an air-assist nozzle,"
Submitted to Comb. Sci. Tech.
Tuttle, J. H., Altenkirch, R. A., and Mellor, A. M., 1973a, "Emissions
from and within an Allison J-33 combustor, II: the effect of inlet
air temperature," Report No. PURDU-CL-73-01, School of Mech. Eng., Purdue Univ,
Tuttle, J. H., Altenkirch, R. A., and Mellor, A. M., 1973b, "Emissions
from and within an Allison J-33 combustor, IT: the effect of inlet air temp-
erature," Comb. Sci. Tech 7_, 125.
Tuttle, J. H., Shisler, R. A., and Mellor, A. M., 1973c, "Nitrogen dioxide
formation in gas turbine engines: measurements and measurement methods,"
Report No. PURDU-CL-73-06, School of Mech. Eng., Purdue Univ.
Vaught, J. M., Parks, W. M., Johnson, S. E. J. , and Johnson, R. L., 1971,
"Final technical report. Collection and assessment of aircraft emissions
baseline data-turboprop engines(Allison T56-A-15)," Report EDR 7200,
Detroit Diesel Allison Division, General Motors Corporation.
Zucrow, M. J. and Warner, C. F., 1956, "Constant pressure combustion charts
for gas turbines and turbojet engines," Purdue University Engineering Experi-
ment Station Bulletin No. 127.
-------
49
APPENDIX. niiTATLTiD INTHRNAL WiASURFMHNTS
On the following pages arc presented axial profiles (based on con-
centration data obtained at the planes shown in Fig. 3-3) of unburned
hydrocarbons (HC) , CO, and NO, grouped by the radial points as shown in
Fig. 3-3. 'Hie order of presentation of the radial points corresponds
to their increasing distance away from the combustor wall, i.e.,
radial point 1 is presented first, and point 4, on the combustor
centerline, last.
A number adjacent to a data point indicates the number of over-
lapping points represented by that point. The area-averaged concentra-
tion of a given pollutant in the vitiated air (as measured by the upstream
gas sampling rake), numerically averaged over the runs during which the
data on that figure were obtained, is shown as the solid horizontal line;
due to scatter, it changes from figure to figure for a given species.
Note that the data points which are plotted arc composite, not net,
emissions.
The general trends exhibited in these figures and which contri-
buted to the development of the flow model shown in Fig. 3-7 are as
follows: at radial position 1 (RP1), HC, CO, and NO are usually near
or somewhat above their inlet area-averaged values, reflecting the
substantial amount of film cooling air adjacent to the combustor wall.
Relative minima in CO and NO at 6, 18, and perhaps at 27 cm (Fig. A-2
and A-3) reflect penetration jets at or just upstream of those axial
positions (Fig. 3-2). CO and NO higher than in the inlet air may reflect
quenching by the film cooling air, and their high values at 3 cm are
-------
~
Q_
Q_
O
t—4
1
l —
CE
o:
i—
LU
1
31
1U ;
5 -
2 -
104 -
5 -
2 -
103 :
5 -
2 -
102 :
5 -
2 -
0
" i \ 1 1 *, j X 1 1 1 1 Isj ^J i 1 i LJ i " X ' \
: < \ \
^TpJ1 T~ fcr
"V^ '
: m
a a °
a C3 a
i i i i i i i
.00 6.00 12.00 18.00 24.00 30.00 36.00 42.00
RXIflL POSITION, (CM FROM NOZZLE)
Figure A-l. Axial HC concentration profile, radial position 1
(base operating point)
-------
21
Q_
QL_
i — i
1 —
CE
1 —
UJ
LJ
LJ
LJ
106 3
5 -
2 -
104 :
5 -
2 -
103 ;
5 -
2
5
2
KHU1HL KUbl 1 ION 1 X ^\
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\^
: S-2
CD
m ° m 0-2 D 00
m n m 00
: m 0 ° a
! CD
1 1 1 1 1 1
0.00
6.00 12.00 18.00 24.00 30.00
RXlf\L POSITION, (CM FROM NOZZLE)
36.00
H2.00
Figure A-2. Axial CO concentration profile, radial position 1
(base operating point)
-------
RflDIflL POSITION 1
iiu.u-
88.0-
21
Q_
Q_
O
CE
1 —
y 44.0-
O
CJ
22.0-
o.o-
\
:^vl.
a
a
[3 Q C3
° CD ° a H m
i i i i i i
0.00
6.00 12.00 16.00 24.00 30.00 36.00
RXIflL POSITION, (CM FROM NOZZLE)
Figure A-3. Axial NO concentration profile, radial position I
(base operating point)
42.00
-------
53
associated witli the base of the flume surrounding the liquid fuel spray
and burning with the dome air. The increase in NO at 36 an suggests
that the flame spreads well across the combustor cross-section by this
plane.
Although RP2 and RP6 are almost equidistant from the centerline,
their profiles are dissimilar since RP2 is directly aligned with pene-
tration jets (cf. relative minima at 13.5 and 32.5 cm in Fig. A-5 and
A-6). Also, the relative minima exhibited at 6 and 27 cm in all the
RP6 profiles indicate that jets along RP1 are spreading rapidly in the
circumferential direction. Values of all species concentrations at
RP2 and RP6 are generally higher than at KP1 as the probe has been
moved out of the film cooling air into the main reaction zone. The
three dimensional nature of the flow is clearly evident from compari-
son of the RP2 and RP6 profiles, especially in the 18 to 24 cm region.
Near the injector CO and NO are again high due to the base flame.
Low values of HC at 3 cm of RP3 (Fig. A-10) and 6 cm of RP5
(Fig. A-13) are most likely a result of substantial liquid fuel at those
stations and are taken to indicate the trajectory of the liquid fuel
spray. Also, the large scatter in HC at RP3 probably indicates the
approximate boundary of the centerline recirculation zone from 8 to 24
cm: the high profile is associated with the recirculation zone (see Fig.
A-13 and A-16), and the low with the main reaction zone and downstream
flow (Fig. A-4 andA-7).
Following Bowman and Cohen (1973) and Altenkirch and Mellor (1973),
-------
Q_
O_
i— i
I—
d
1 —
UJ
nr
106 a
s :
s '•
2 •
103 .
s :
2 -
102 d
5 -
2 -
0
RHDIHL POSITION 6 X X
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X
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X
X
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flXIflL POSITION. (CM FROM NOZZLE)
Figure A-4. Axial HC concentration profile, radial position 6
(base operating point)
-------
s:
Q_
Q_
i — i
-------
RflDIflL POSITION 6
iiu.u-
88.0-
Q_
Q_
§ 66-0-
i— i
i —
cr
cz.
\—
y 44.0-
g
O
ED
22.0-
0.0-
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/ * ^ \
^ - V
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i
X
X
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X
* X
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XX X
X
* X
X *
.00 6.00 12.00 18.00 24.00 30.00 36.00 42
RXIflL POSITION, (CM FROM NOZZLE)
Figure A-6. Axial NO concentration profile, radial position 6
(base operating point)
en
CJv
-------
z:
Q_
Q_
»— i
1 —
CE
1 —
LJ
O
O
O
HI
IDS _ RflDIHL POSITION 2 / X
5 -
2 -
5 -
2 -
103 :
5 -
2
102
5
2
10 l
C
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44- + 4- ':
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* - •* A 1* ft ft J*[ ft ft
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RXIRL POSITION. (CM FROM NOZZLE)
Figure A-7. Axial HC concentration profile, radial position 2
(base operating point)
on
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~
Q_
Q_
i — i
1 —
CT
ct:
i—
LU
O
CJ
CJ
105 a
5 •
2 -
10H :
s :
2 -
103 i
5 •
2 •
102 :
5 -
2 -
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KRD1HL KQSITION 2
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6.00 12.00 16.00 24.00 30.00
RXIflL POSITION, (CM FROM NOZZLE)
36.00
Figure A-8. Axial CO concentration profile, radial position 2
(base operating point)
oo
H2.00
-------
RflDIflL POSITION 2
iiu.u-
88.0-
21
Q_
Q_
ED
i — i
h-
o:
ct:
\—
y 44.0-
o
22.0-
0.0-
1 V 1 1 UX A 1 1 U_ 1 *fc_f *^y JL 1 ^ VM* 1 1 I—
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00
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1 1 1 I 1 1
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6.00 12.00 18.00 24.00 30.00 36.00
flXIRL POSITION, (CM FROM NOZZLE)
Figure A-9. Axial NO concentration profile, radial position 2
(base operating point)
42.00
-------
~
Q_
Q_
0
i — i
h—
d
t—
IjJ
o
CJ
CJ
31
105
5
2
ID*
5
2
ID3
€
2
102
5
2
P RRDIRL POSITION 3
: , ^ — -xi
: A A A 4^ 4- V
A ' N^'T.
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A .
A A A
A A
A
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: A
0.00 6.00 12.00 18.00 24.00 30.00 36.00 42
flXIflL POSITION, (CM FROM NOZZLE)
Figure A-10. Axial HC concentration profile, radial position 3
(base operating point)
o\
o
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2-
Q_
Q_
-^
D
1—4
J—
cr
01
i—
LU
CJ
CJ
CJ
106 ,
5 -
2 -
10H ;
5 -
2 •
ID3 :
5 -
2
102
5
2
ID1
RRDIHL POSITION 3 ,-' ^
A 4(^\
A A \"
A '' \.
A A ^- ^
A A A
A A-2 A A ^
A A
A A
A
A-*A fi ftftAA ^ft
I I I I I I
0.00 6.00 12.00 18.00 24.00 30.00 36.00 42
flXIRL POSITION, (CM FROM NOZZLE)
Figure A-ll. Axial CO concentration profile, radial position 3
(base operating point)
-------
RRDIRL POSITION 3
iiu.u-
88.0-
Q_
Q_
§ 66.0-
1— 1
L—
r
-------
s:
Q_
Q_
i— i
1 —
o:
ce:
i —
UJ
CJ
o
LJ
O
105 3
5 -
2 -
S -
2 -
103 :
5
2
102
5
2
10 l
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Z-2 Z V >2^--&
z z 1 z V^____^ '
z I
z
; z z
z
z
: Z 2
1 1 1 1 1 1
0.00
6.00 12.00 16.00 24.00 30.00 36.00
flXIRL POSITION, (CM FROM NOZZLE)
Figure A-13. Axial HC concentration profile, radial position 5
(base operating point]
42.00
-------
~
Q_
Q_
•2L
\ — i
1 —
CE
C£
1—
UJ
CJ
CJ
o
105 KHU1HL POSITION 5 ^-^,
5 -
2 -
104 :
5 -
2 -
103 :
5 -
2 -
102 :
5 -
2 -
0
: z z z z-s ^° ~ — ^
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2 Z "-^
Z
: 2 z
Z-2
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flXIflL POSITION, (CM FROM NOZZLE)
Figure A-14. Axial CO concentration profile, radial position 5
(base operating point)
-------
RflDIRL POSITION 5
iiu.u-
88.0-
31
Q_
Q_
O
i — i
I—
cc
1—
2
y 44.0-
2
o
CJ
D
22.0-
0.0-
C
jT I \ i 1 1— ' J.lii_l<^/v^rj.l^^JI^^^ \
"Z. ' ^ — •>* \
Z
z
z
z
z
z z z
Z 2-2
Z
z
z
z z
z z 2-2
z
1 1 1 1 1 1 1
.00 6.00 12.00 18.00 2H.OO 30,00 36.00 H2
flXIflL POSITION, (CM FROM NOZZLE)
Figure A-15. Axial NO concentration profile, radial position 5
(base operation point)
-------
31
Q_
Q_
O
i— i
1 —
cr
ct:
i—
LiJ
0
O
CJ
CJ
31
105 q
5 -
2 -
10H :
5 -
2 -
103 :
5 •
2 •
ID2 ;
s :
2 -
101 -
KRDIHL POSITION 4 / \
{ •& ^z. \
; ^ 4'^> !
X \\c.^A /
X X x \ >^^ /
x x xU x \ /7
XrTTl " VT \ X^
X-P ^^^ _^^
X-2 X ^2 X-g ^p
: X X X-g
: x
; X-2
1 I 1 I 1 1 1
0.00
6.00
12.00 18.00 24.00 30.00 36.00
flXIflL POSITION. (CM FROM NOZZLE)
Figure A-16. Axial HC concentration profile, radial position 4
(base operating point)
H2.00
-------
z:
Q_
Q_
O
i— i
1
r—
cr
Cd
H-
UJ
u
5
0
CJ
106 a
S -
2 -
S -
2 -
103 :
5 -
2 -
10s :
5 -
2 -
0
KHU1HL t-Ubl 1 iUN 4
X-3 „ _ X-2 X-2 X X
I X v X X X-2
)( \£«ffl ^ ^« ^f •^ \£
X
j ^7\ ^\
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• ' ^Z^y
.00 6.00 12.00 18.00 24.00 30.00 36.00 42
RXIflL POSITION, (CM FROM NOZZLE)
Figure A-17. Axial CO concentration profile, radial position 4
(base operating point)
-------
RflDIRL POSITION H-
iiu.u-
ee.o-
Q_
Q_
2G£^ rt
U^j • \J
o
• — i
i—
1 1 ll_ 1 Ut_l A 1 1 <-JI 11 / \,
\^V y
'V_^'
x
X X
X
X X
X X
x x
X x
x x x
X
X
X-S x
x x x
x x
X-2
.00 6.00 12.00 18.00 24.00 30.00 36.00 42
flXIflL POSITION, (CM FROM NOZZLE)
Figure A-18. Axial NO concentration profile, radial position 4
(base operating point)
oo
-------
69
approximately constant values of HC, CO, and NO in the 13 to 18 cm
region of RP5 and the 8 to 18 on region of RP4 are taken to define this
centerline recirculation zone. At the downstream edge of the zone,
the flame (or main reaction zone) closes upon itself to the center-
line, as indicated by the rapid HC oxidation, resulting CO oxidation
somewhat farther downstream, and rapid NO formation. Since HC and CO
fall off more slowly at RP4 (on the centerline) than at RP5, the core
of the flow is still fuel rich as a result of the substantial use of
film cooling air; thus mixing and further oxidation persist downstream,
probably to the turbine inlet as discussed in Section III-B.
------- |