Stationary Source Enforcement Series
EPA 340/1-78-OOla
APRIL 1978
JET ENGINE TEST CELLS -
EMISSIONS AND CONTROL
MEASURES: PHASE 1
SMI
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Enforcement
Office of General Enforcement
Washington, D.C. 20460
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EPA-340/l-78-001a
April 1978
JET ENGINE TEST CELLS - EMISSIONS AND
CONTROL MEASURES: PHASE 1
by
D. E. Blake
Contract No. 68-01-3158, Task 4
EPA Project Officer: James Herlihy
Acurex Report TR-78-102
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Division of Stationary Source Enforcement
Technical Support Branch
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This report was furnished to the U.S. Environmental Protection Agency by
the Aerotherm Group of Acurex Corporation, Mountain View, California, in
fulfillment of Contract No. 68-01-3158. The contents of this report are
reproduced herein as received from the contractor. The opinions, find-
ings, and conclusions expressed are those of the author and not necessar-
ily those of the U.S. Environmental Protection Agency.
The Enforcement Technical Guideline series of reports is issued by the
Office of Enforcement, Environmental Protection Agency, to assist the
Regional Offices in activities related to enforcement of implementation
plans, new source emission standards, and hazardous emission standards to
be developed under the Clean Air Act. Copies of Enforcement Technical
Guideline reports are available -- as supplies permit from the Air
Pollution Technical Information Center, Environmental Protection Agency,
Research Triangle Park, North Carolina, 27711, or may be obtained, for a
nominal cost, from the National Technical Information Service, 5285 Port
Royal Road, Springfield, Virginia, 22161.
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ACKNOWLEDGEMENT
The author wishes to acknowledge the help and guidance of
Dr. James Herlihy, the Project Officer, and Mr. Charles Seeley of EPA
Region IX. In addition, many persons provided useful information dur-
ing the course of this program. Appendix B presents a list of their
names.
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ABSTRACT
This report discusses the current state of the art of pollutant
emission measurement and cleanup technology related to military jet engine
test cells. Considerable emissions data from jet engines is available,
but data from test cell stacks are sparse. Gaseous emission data for the
major pollutant species (CO, NO, N02, S02, S03) are reliable; partic-
ulate, opacity, and unburned hydrocarbon data are less so.
The five types of test cell cleanup methods that have been experi-
mentally evaluated electrostatic precipitator, nucleation scrubber,
fuel additives, thermal converter, and fuel atomization improvement are
described in detail. Other, less promising methods are briefly discussed.
Several methods are quite effective in reducing test cell emissions. Fuel
additives are effective in reducing test cell plume opacity. Capital and
operating cost data on these methods are presented. For the nucleation
scrubber, the best-developed cleanup technology, three cost estimates from
different sources are given.
Phase II of this study will discuss operating parameters, state
regulations, additional control device cost data, environmental impact,
clean combustor development status, and additional emissions data.
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TABLE OF CONTENTS
Section Page
1 INTRODUCTION 1
2 SUMMARY 3
3 JET ENGINE TEST CELLS PROCESS DESCRIPTION 9
4 LOCATION OF MILITARY TEST CELLS 19
5 EMISSIONS DATA 25
5.1 Opacity 25
5.2 Gaseous Emissions 27
5.3 Participate Emissions 37
6 TEST CELL EMISSION CONTROL TECHNOLOGY 47
6.1 Electrostatic Precipitator 50
6.1.1 ESP Experimental Apparatus 52
6.1.2 Experimental Results 56
6.1.3 Costs 59
6.2 Nucleation Scrubber 60
6.2.1 Scale Model Scrubber Tests 75
6.2.2 Proposed Scrubber Facilities 79
6.2.3 Costs 80
6.3 Fuel Atomization 83
6.3.1 Methane Absorption 83
6.3.2 Emulsions 84
6.4. Thermal Converter 86
6.4.1 Thermal Converter Configuration for Test Cells 86
6.4.2 Pollutant Conversion Performance 89
6.4.3 Costs 90
6.5 Fuel Additives 90
6.5.1 Civilian Airline Additive Use 97
6.6 Other Abatement Methods 99
6.6.1 Cyclone Separators 103
6.6.2 Fabric Filters 103
6.6.3 Venturi Scrubbers 104
vn
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TABLE OF CONTENTS (Concluded)
Section Page
6.6.4 Coanda Noise Suppressor 105
6.6.5 Hush House 107
6.7 Summary of Cleanup Technology 109
REFERENCES Ill
APPENDIX A SCRUBBER RETROFIT COST ESTIMATE 115
APPENDIX B INFORMATION SOURCES 133
vi
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LIST OF ILLUSTRATIONS
Figure Page
1 Stationary Test Cell (Oceana Type Shown) 10
2 Travis AFB Test Cell Building... 11
3 Tinker AFB J79 Engine Test Cell 12
4 Augmenter Tube for Tinker AFB Test Cell 14
5 Test Cell with Open-End Augmenter 16
6 SAE Smoke Number Versus Opacity for Jet Engines 28
7 Relationship Between SAE Smoke Number and Soot
Density for Jet Engines 29
8 NOX Emissions from Jet Engines 32
9 Comparison of Typical Turbine Engine Exhaust Gas
S02 Concentrations with Various Air Pollution
Control District Limits 34
10 Unburned Hydrocarbon (UHC) Tailpipe Emission Levels
of Jet Engines at Idle 35
11 Particulate Mass Loading for Jet Engines, Measured
at the Tailpipe 44
12 Electrostatic Precipitator Experimental Setup --
Black Point No. 1 Test Cell 53
13 Electrostatic Precipitator Test Unit 55
14 Nucleation Scrubber Schematic 61
15 Teller Environmental Systems, Inc. Augmenter 63
16 Nucleation Scrubber at Jacksonville NAS 71
17 Aerial View of Jacksonville Scrubber 73
18 Pilot Scrubber System on Black Point No. 1 Test Cell
at the Jacksonville Naval Air Station 76
19 Schematic Diagram of Basic Thermal Converter
Configuration 87
20 Effect of Ferrocene on Particulates 98
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LIST OF ILLUSTRATIONS (Concluded)
Figure Page
21 Principle of Coanda Device 106
22 Hush House at Miramar Naval Air Station 108
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LIST OF TABLES
Table Page
1 Operational Navy Test Cells and Test Stands 20
2 Operational Air Force Test Cells and Test Stands 21
3 Operational Army Test Cells and Test Stands 23
4 Total Test Cells All Services 23
5 Participate Size Distribution from 057 Jet Engine 39
6 Comparison of Engine and Stack Participate Measurement... 43
7 Jet Engine Test Cell Control Measures 47
8 Emission Data from the Electrostatic Precipitator
at Jacksonville Naval Air Station, Black Point
No. 1 Test Cell J79 Engine 58
9 Nucleation Scrubber at Jacksonville Naval Air
Station, Emission Levels from Black Point
No. 1 Test Cell 65
(
10 Observations During Test Cell Cleanup System Test 68
11 Test Results on Pilot Scrubber at the Black Point
No. 1 Test Cell at Jacksonville Naval Air Station,
Using a J79 Engine 78
12 Scrubber Retrofit Cost Estimate -- Naval Air Systems
Command 81
13 Scrubber Retrofit Cost Estimate Jacksonville NARF 81
14 Comparison of Scrubber Cost Estimates 82
15 Effect of Water/Fuel Emulsion on Combustion 85
16 Thermal Converter Cost Estimate 91
17 Metallic Fuel Additives Evaluated by the Naval Air
Propulsion Test Center 93
18 Engines Suitable for Use with Ferrocene Additives 94
19 Effect of Fuel Additive on Stack Opacity 95
20 Fuel Additive Use by Commercial Airlines 100
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LIST OF TABLES (Concluded)
Table Page
21 Summary of Particulate Abatement Systems 101
22 Comparative Data -- Alternate Gas Cleaning Systems 102
xn
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SECTION 1
INTRODUCTION
Jet engine test cells are used for testing jet engines after main-
tenance or overhaul. They house the instruments, fuel delivery systems,
and noise suppression devices required for the testing. Test cells are
maintained by the U.S. Army, Navy, and Air Force, civilian airline main-
tenance bases, and gas turbine manufacturers. When jet engines are tested,
a dark sooty particulate is produced by the gas turbines. And because
test cells usually have vertical exhaust stacks, these emissions are often
visible from a considerable distance. Several jet engine test cell facil-
ities have recently been cited for violation of local Air Pollution Con-
trol District opacity regulations. Some test cells may be in violation of
particulate mass loading and NO stationary source emission standards as
^
well.
The military services are aware of these problems, and have put
into effect a number of programs to characterize and control test cell
emissions. The U.S. Air Force is primarily responsible for determining
the nature of test cell emissions and how they affect overall military
base and regional pollutant levels. The U.S. Navy has the responsibility
for evaluating ways of reducing emissions and has investigated many dif-
ferent methods. Civilian airlines have not reported any comparable
studies.
-------
This report is limited to military test cells. It considers both
the emissions data available and the current state of test cell cleanup
technology. Because of the great amount of current activity in these
areas, a great deal of recent information has not been published. Accord-
ingly, much of the information in this report was obtained from interviews
with people actively working on test cell emissions programs. Mr. W. C.
Morhard, Environmental Coordinator, Naval Air Systems Command, helped a
great deal in identifying people working on various Navy programs and in
obtaining permission for the author to visit and discuss their work. Ap-
pendix B gives a list of people who provided significant useful informa-
tion. The guidance of the Project Officer, Dr. James Herlihy and Mr.
Charles Seeley of EPA Region IX, is also gratefully acknowledged.
Additional aspects of test cells will be considered in Phase II of
this study. These will include (a) discussion of process variables that
affect emission, (b) summary of state and local regulations, (c) addi-
tional capital and operating costs, (d) environmental impact of test
cells, (e) discussion of clean combustors, and (f) a summary of available
emission data.
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SECTION 2
SUMMARY
In this report, Aerotherm Division of Acurex Corporation analyzes
what is currently k.vjwn about pollutant emissions from jet engine test
cells and about cleanup technology for these cells. This analysis is
limited to military test cells in the United States and was undertaken for
the Stationary Source Enforcement Division of the Environmental Protection
Agency.
To provide a background for discussion of test cell emissions and
control technology, the report begins with a description of typical jet
engine test cells and a discussion of how they operate. This discussion
describes how augmenter tube design and exhaust water spray cooling prac-
tice can affect emissions and cleanup technology. The design of the aug-
menter affects the dilution ratio of the exhaust stream, and therefore the
opacity, while the presence or absence of water spray cooling of the en-
gine exhaust affects particulate and unburned hydrocarbon emissions in
several ways. In addition, the report also points out that test cells are
not standardized, and that similar engines can produce different opacity
levels in different test cell geometries.
Next, U.S. military test cells are
military service, and location. There anex"a total of 130 permanent^-te'st
-------
cells, 88 demountable test cells, and 273 test stands for the Army, Navy
and Air Force.
In Section 5 of the report, the validity of existing data and mea-
surement methods is discussed and analyzed. Opacity, gaseous emission,
and particulate emission data are treated separately. Data on the opacity
of plumes from test cell stacks are found to be widely available. Actual
emission data are given in Section 6 of the report.
The correlation between stack opacity and engine exhaust smoke
number is also discussed. This correlation is not particularly good, but
it still gives useful information about the relationship between engine
particulate output and test cell opacity.
Gaseous emission data from jet engines are also widely available,
but have usually been taken at or immediately downstream from the engine.
Samplings of test cell stacks are sparse. Methods for measuring the con-
centration of NO, NO^, CO, and C02 are reasonably accurate and reli-
able in the hands of knowledgeable analysts. Furthermore, engine tailpipe
data should be readily transformable to stack emissions data by accounting
for augmentation air, because these gaseous pollutant species are sub-
stantially unchanged between engine exhaust and stack outlet. After the
exhaust gases leave the tailpipe, cooling is so rapid that essentially no
more NO is formed. SO is usually not measured but is calculated
A A
from fuel sulfur specifications. Measuring unburned hydrocarbons (UHC)
presents problems. Flame ionization adequately measures overall hydro-
carbon vapor levels. But analyzing individual hydrocarbon species, which
requires collection and subsequent analysis, is complicated by the fact
that UHC can exist in both vapor and particulate form. This means that
the sampling method used to collect the UHC must be carefully chosen.
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Particulate emission data are the most difficult to obtain and are
in general the least reliable. There are almost no good particulate data
obtained by sampling at the top of test cell stacks; and, the present
state of knowledge does not permit accurate prediction of particulate
stack emissions based on particulate measurements at the engine. Special
problems in measuring particulate emissions include particle loss and
reentrainment from noise suppression equipment in the stack and the
inability to account for the effects of exhaust water spray cooling.
In Section 6 of the report, five test cell exhaust cleanup methods
which have been experimentally evaluated are discussed at some length.
Several other possible cleanup methods which have been judged infeasible
-\
are also discussed in less detail.
Fuel additives are generally organometallic compounds added in
small concentrations to the fuel burned in turbine engines. The metallic
component of the additive acts catalytically to improve or at least modify
combustion. The main effect of fuel additives is on opacity, although a
moderate but inconsistent reduction in particulate loading has also been
reported. Both the Navy and the Mr Force are pursuing experimental pro-
grams to evaluate different kinds of fuel additives. The Navy has settled
on an iron-based additive for its engines, while the Mr Force is con-
sidering a manganese-based additive. Both appear able to reduce opacity
of test cells to below 20-percent opacity without damage to the engines
being tested. Problems include toxicity (for the manganese compound) and
thermal sensitization (for the iron compound). The cost of using fuel
additives at test cells would be negligible.
Improving fuel atomization is another exhaust cleanup method now
being tested. With this method, an emulsion of about 10-percent water in
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jet fuel is used for testing in cells. The water globules present in the
emulsion flash in the burners. This causes finer atomization of the fuel,
and thus better combustion. Improvement in particulate and N0x emissions
and opacity have been reported. This work is in a relatively early stage.
A third experimental cleanup method is the thermal converter. A
thermal converter consists of additional fuel burners downstream from the
engine which oxidize CO, carbonaceous particulate, and UHC. In experiments
conducted to date, the thermal converter has proven very effective, reduc-
ing smoke number by a factor of 10. NO production by the additional
A
fuel burners is apparently not a severe problem. The main difficulty with
the thermal converter is its high fuel consumption and operating cost.
Capital cost for a Type A test cell retrofit has been estimated at
$500,000, with a similar amount required annually for operation.
A fourth cleanup device, the electrostatic precipitator (ESP), has
been evaluated in 1/65 scale model tests on a test cell at Jacksonville
Naval Air Station. The ESP showed reasonable collection efficiency,
averaging 59 percent when particulate was measured by EPA Method 5, and
higher (80 to 95 percent) when measured by a dry filter method.
Problems with arcing and high voltage lead failure were noted by
the Jacksonville Naval personnel testing the ESP. These problems were
reported to be related to water droplet carryover into the ESP from the
quench system at the augmentor. Similar problems would be anticipated in
the demonstration of a full-sized test cell ESP unless excess water
carryover is eliminated. On the other hand, operating completely dry (no
quench water) means higher volumetric flowrates in the ESP.
According to reports from Jacksonville Naval Air Station, more
development work is required,to determine if a satisfactory operating
-------
condition can be maintained. The cost of installing an ESP on an existing
500,000 acfm test cell has been estimated at $850,000. Annual operating
expenses are estimated at $32,000.
The fifth cleanup device considered is the wet packed cross-flow
scrubber. It is the only test cell cleanup device that has been given
full-scale evaluation on a cell. A prototype installation on the Black
Point No. 1 cell at Jacksonville NAS is a nucleation scrubber mounted on
the top of the cell stack. Water is injected into the engine exhaust at
the augmenter tube, causing the nucleation and particle growth. The
larger particles are carried up the stack and collected in the packed
scrubber. Limited sampling of the cleaned exhaust showed that at least 90
percent of the particulate had been removed and the opacity reduced to
below 10 percent. More extensive sampling of a scale model packed bed
scrubber showed that 50 to 70 percent (average of 55 percent for all
tests) of the particulates and nearly all of the condensible hydrocarbons
had been eliminated. Two Navy estimates for the cost of retrofitting
500,000 acfm test cell facilities with nucleation scrubbers, including
closed-loop water treatment, are $1,515,000 and $1,944,735. Teller
Environmental Systems, Inc., the system engineer/contractor for the
prototype scrubber, estimates the cost of retrofitting at $705,650.
In summary, several methods are currently available for consider-
ably reducing test cell pollutant emissions. Particulates can be effec-
tively removed by the scrubber, the ESP, and the thermal converter.
Hydrocarbons are substantially removed by the scrubber and the thermal
converter. The major technical issues relate to true capital costs, and
the impact on air quality of controlled versus uncontrolled test cells.
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SECTION 3
JET ENGINE TEST CELLS ~ PROCESS DESCRIPTION
/
Jet engine test cells house the engine and test instrumentation
during engine testing. Test cells are maintained by the military services,
commercial airlines and turbine engine manufacturers. Most test locations
contain only a few cells, although some large engine manufacturers main-
tain up to 70 test cells at their test facilities. Existing test cells
were designed mainly to suppress noise, and they are reasonably effective
at reducing the very high sound levels at the engine tailpipe (in excess
of 180 dB for some engines) to tolerable levels.
Five kinds of test facilities are used by the military for out-of-
aircraft engine testing. These are depot permanent test cells, Type A and
Type C permanent test cells, demountable test cells, and test stands.
Depot cells are permanent masonry structures, fully instrumented. Type A
cells are similar, but less fully instrumented. These kinds of cells are
used to checkout engines that have been overhauled (completely rebuilt).
Figures 1, 2, and 3 are diagrams of typical depot or Type A mili-
tary test cells. While there are superficial differences between the
three cells shown, the basic structures are similar,. The test cell itself
is usually a massive reinforced concrete structure, designed to withstand
the intense vibrations generated by the engine. Air is drawn into the
cell through various kinds of acoustical baffling by the engine acting as
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EXHAUST
OUTLET
SOUND
TREATMENT BAFFLES
AUGMENTING AIR
PRIMARY
ENGINE AIR
TEST ENGINE
MULTIPLE SPRAY RINGS EXHAUST
AUGMENTER TUBE
SECTION B-B
CONTROL
ROOM
&
PUMPING
FACILITIES
SECTION A-A
Figure 1. Stationary test cell (Oceana type shown)
(Reference 10).
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COMBUSTION
AND AUGMENTER AIR
Kv»>XvXvIv>X
pvXv>»Xv»>»
tV.V.V.V.V.V.V.V
V.V.V.V.V.V.V.V.'.V
***
r/ v.v.v %v v.v.v.v
fev>>X%vXvXvv:-
EXHAUST
SOUND TREATMENT7
\.
THRUST
r D A M C
r KM m t
-^
«^
Figure 2. Travis AFB test cell building
(Reference 10).
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(\3
HORIZONTAL ACOUSTICAL BAFFLE
ACOUSTICAL DUCTS
VERTICAL ACOUSTICAL BAFFLES
COMBUSTION AIR
AUGMENTER AIR
EXHAUST
Figure 3. Tinker AFB J79 engine test cell
(Reference 17).
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an ejector. (As with all ambient-pressure test cells, no booster fans are
used.) Although not shown on the figures, adjustable dampers are often
provided near the inlet-air acoustical baffler to control the engine
airflows and test cell interior pressure levels.
The test engine is fastened to a thrust frame or stand. This is in
turn firmly anchored to the cell. The thrust frame contains the instru-
mentation used to monitor engine thrust. Immediately behind the engine is
mounted the augmenter tube, so named because it augments the flow of air
through the cell. The augmenter is simply an ejector that serves several
purposes: (1) powered by the high energy engine exhaust stream, the aug-
menter reduces the test cell pressure to a level equivalent to the pres-
sure at the engine compressor inlet; (2) the air drawn over the engine
provides some of the cooling normally obtained by the motion of the air-
craft in flight; and (3) the air entrained by the augmenter cools and di-
lutes the engine exhaust. The cooling produced protects the integrity of
the test cell by keeping the concrete below the spall ing temperature of
350°F to 400°F, and protects the noise control equipment. Since a
test cell augmenter must be used with many different types of engines,
each with its own air pumping characteristics, exhaust diameter, and
exhaust temperature, the main concern is usually to assure that thermal
damage to the test cell is minimized, rather than to optimize the aug-
menter 's airflow properties.
A typical augmenter tube is shown in Figure 4. The bellmouth posi-
tion is adjustable so that the spacing between the engine and the aug-
menter can be varied according to the type of engine being tested. The
engine exhaust gas and entrained air are carried down the steel augmenter
tube to a position under the exhaust stack. The augmenter tube is usually
13
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MOVABLE BELLMOUTH
EXHAUST GAS
K \ /i
' t
5 FT 6 IN.
I
'W
1
1
1
1
X
COOLING SPRAY RINGS"
"T
1
1
!
1
1
._!
y
^t
i
8 FT 4IN.
ooooooooooooooooooooooooooo\
oooooooooooooooooooooooooooA
OOOOOOOOOOOOOOOOOOOOOOOQOOOO
oooooooooooooooooooooooooooo
oooooooooooooooooooooooooooo*
oooooooooooooooooooooooooooo
OOOOOOOOOOOOOOOOOOOOOOOOOOOOl
0000000000000000000000000007
nnnnrmnnnnnnrinnnnnnnnnnnnnn/
/ PERFORATED BASKET
Figure 4. Augmenter tube for Tinker AFB test cell
(Reference 10).
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perforated at this point to allow the gas to diffuse out more or less uni-
formly. This prevents hot spots which could cause damage to the concrete
cell.
Some augmenters, however, are open-ended. Figure 5 shows a test
cell with an open-ended augmenter. Exhaust gases are directed up the
stack by permanently mounted turning vanes. The Black Point No. 1 cell at
Jacksonville Naval Air Station, where considerable work on scrubber and
electrostatic precipitator cleanup devices has been done, is of this type.
The cooling spray rings shown in Figure 4 provide important addi-
tional cooling at high engine power settings. The cooling spray rings
have nozzles mounted on the inside surface that spray water radially into
the hot gas stream. Water spray cooling is universally used during after-
burner operation. In most test facilities, water spray is used at all
engine power settings above idle, but some test cell operators choose to
use cooling water only at military (100-percent) power and afterburner
settings. In some test cells, cooling water is automatically turned on
when the exhaust gas reaches a predetermined temperature (usually 350°F).
Water spray cooling of exhaust gases affects pollutant emission in
several ways. First, the water spray scrubs some particulate out of the
exhaust stream. Excess runoff water flowing out of the augmenter is often
quite black. Second, under some operating conditions (idle and after-
burner), considerable amounts of unburned hydrocarbon vapors are found in
the exhaust. Quenching the exhaust stream with water causes the condensa-
tion of these vapors to form additional particulate. Third, if excess
amounts of water are sprayed, a saturated or supersaturated condition is
attained. Water vapor condenses on particulate nuclei, causing particle
growth. In addition, water droplets present in the stream will not
15
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Exhaust gases
Combustion and
augmentation air
suppresson
baffles
Engine
Augmenter
Turning
'vanes
Figure 5. Test cell with open-end augmenter.
16
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evaporate. The result, often seen when too much spray cooling water is
used, is a dark, heavy plume that settles rapidly, causing considerable
annoyance to those downwind of the test cell.
After the exhaust gases move out of the perforated basket (or col-
lander) section of the augmenter tube, they leave the cell through a ver-
tical stack. These stacks are often quite large: 200 to 400 square feet
in cross-sectional area and 40 to 60 feet high are common dimensions. The
stack is fitted internally with sound baffling and absorbent structures.
Permanent test cells in the United States are not standardized.
While all cells share the same operational features (air inlet, engine
test room, augmenter, stack, sound deadening structures), their internal
arrangement can vary considerably. Stack diameters, engine-to-stack
spacing, turning vane design, and augmenter tube design in general differ
from cell to cell.
Differences in augmenter design have a particularly significant
effect on air pollution control. As the design of the augmenter is more
art than science, each test cell designer makes such changes in the
augmenter as he thinks appropriate. As a result the air pumping charac-
teristics and water spray cooling pattern of each augmenter seems to be
unique. The augmentation ratio of test cells (air entrained divided by
engine exhaust) is adjustable, usually by varying the engine-to-augmenter
distance. It ranges from about 0.6 to 3, depending on engine power level.
But the pattern of airflow in the augmenter tube and the water pattern are
not adjustable. The amount of particulate scrubbed out of the exhaust
stream, the amount of hydrocarbon vapor condensed, the particulate wall
losses, and the overall dilution ratios are therefore generally differ-
ent from one cell to another, even when the same engine is being tested.
17
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This is a complicating factor both in determining emissions from test
cells and in designing control devices.
Other Types of Test Facilities
Like Type A cells, Type C cells are usually constructed of rein-
forced concrete. Some, however, are made of metal. They are permanent
fixtures, similar in shape to Type A cells but commonly only 70 to 80
percent of their size. Type C cells are not fully instrumented, and often
lack thrust measurement instrumentation. They are used for testing en-
gines that have undergone intermediate level repair -- that is, repair
that does not involve the hot section of the engine.
Demountable test cells are of metallic construction and are usually
smaller than Type C test cells. These cells can be taken apart and moved
if necessary, although they are large enough and complex enough that mov-
ing them is not a simple matter. They are instrumented to about the same
extent as Type C cells.
Test stands are simply unenclosed frames designed to hold the en-
gine while simple tests are performed. In test stands, the engine ex-
haust is not confined.
18
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SECTION 4
LOCATION OF MILITARY TEST CELLS
Military jet engine test facilities are widely dispersed throughout
the United States. Tables 1 through 4 show a census taken in July 1975.
"Cells" include both Type A and Type C permanent test cells.
19
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TABLE 1. OPERATIONAL NAVY TEST CELLS AND TEST
STANDS (Reference 18)
Location
Alaska
Arizona
California
Florida
Georgia
Hawaii
Louisiana
Maine
Maryland
Massachusetts
Mississippi
New Jersey
North Carolina
Pennsylvania
South Carolina
Texas
Virginia
Washington
TOTAL
Cells
1
31
7
1
1
9
10
1
9
2
72
Stands
2
2
16
10
2
6
2
1
3
1
3
1
6
3
1
7
6
1
73
20
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TABLE 2. OPERATIONAL AIR FORCE TEST CELLS AND TEST STANDS (Reference 18)
Location
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
roil,- Demountable
Cel1s Cells
2
4
2
8 9
1
1 2
4 3
3
1
2
1
1
2
1 1
1
3
4
2
2
1
1 1
1
5
1 1
Stands
3
3
11
5
18
3
1
10
5
4
3
5
3
2
4
6
6
2
4
4
7
2
3
2
4
1
3
6
5
21
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TABLE 2. CONCLUDED
Location Cells
North Carolina
North Dakota
Ohio
Oklahoma 15
Oregon
Pennsylvania
South Carolina 1
South Dakota
Tennessee
Texas 10
Utah 3
Vermont
Virginia
Washington 1
West Virginia
Wisconsin
Wyoming
TOTAL 47
Demountable
Cells
1
2
2
3
3
1
15
2
1
3
1
88
Stands
5
3
10
2
1
3
6
1
1
12
2
5
1
1
188
22
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TABLE 3. OPERATIONAL ARMY TEST CELLS AND TEST STANDS (Reference 18)
Location
Cells
Stands
Pennsylvania
Texas
Virginia
12
TOTAL
10
1
11
12
JNS
CO
TABLE 4. TOTAL TEST CELLS - ALL SERVICES (Reference 18)
Navy
Air Force
Army
Cells
72
47
11
Demountable c*a^«.
Cells Stands
73
88 188
12
TOTAL
130
88
273
-------
SECTION 5
EMISSIONS DATA
This section discusses each of the three main classes of jet engine
test cell pollutants -- visible, gaseous, and particulate emissions. Pol-
lutant measurement methods are analyzed, problems and drawbacks are
pointed out, and an assessment of the general validity of published data
is made. Actual emission data are given in Section 6, Test Cell Emission
Control Technology. A compilation of emission data will be included in
Phase II of this study.
5.1 OPACITY
The typical plume from a jet engine test cell is quite dark, be-
cause of the carbonaceous nature of the particles that are emitted. It
can be easily seen by anyone in the area. Plume opacity is the only basis
to date upon which test cells have been cited for violation of local Air
Pollution Control District requirements. Plume opacity varies with the
engine tested, the type of cell, the power setting used, and the kind of
fuel being burned.
A basic problem exists in attempting to predict the opacity of the
plume produced by the same engine tested in a different cell. In general,
different opacities will result in some cases, markedly different.
There are several reasons for this. One is the physical differences that
exist between the test cells. Another is the different methods used in
25
-------
operating test cells. And a third reason is the modification of particle
size distribution that occurs between engine tailpipe and cell stack exit
plane.
Test cells are individually designed and constructed, as are their
augmenter tubes, exhaust quench spray devices, and noise abatement equip-
ment. Accordingly, different cells, when testing the same engine, will
show different augmenter air dilution ratios, exhaust gas quench rates,
stack velocities, and opacities. Particle residence time will thus vary,
as will unburned hydrocarbon condensate particle size distribution, and
stack wall loss and reentrainment rates. The result will be different
particle mass loadings and size distribution for different cells testing
the same engine. In addition, the opacity of the plume can be affected by
the augmentation ratio (ratio of entrained air to engine exhaust).
Because of these many variables, not only will a given engine give
different opacity readings in different test cells, but the same engine in
the same cell can from time to time give different readings because of
variations in operating procedures.
Another parameter used to measure opacity is called the smoke
number. The smoke number is usually used to quantify the opacity of the
gas stream at or near the engine tailpipe. There are several methods for
measuring smoke number. Although they are generally similar, they none-
theless result in different values for the smoke number of an engine
(Reference 21).
The Society of Automotive Engineers (SAE) has established Committee
E-31 which is responsible for development of recommended practices for
measuring smoke emissions. Aerospace Recommended Practice (ARP) 1179 has
resulted from their efforts (Reference 24). The technique for quantifying
26
-------
smoke emission specified by ARP 1179 requires sampling and transfer of the
exhaust stream, filtering of a known quantity of the sample gas through
filter paper, and measurement of the reflectance of the soiled filter
paper. A quantitative number (SAE smoke number between 0 and 100) is
produced as a result of this technique.
The U.S. Navy has established a similar procedure (Method AS 1833)
to give an opacity characteristic called the Navy smoke number. Although
the SAE smoke number is more commonly reported, Navy smoke numbers can be
converted to SAE smoke numbers by means of a good correlation (Reference
22).
Figure 6 shows the experimentally determined relationship between
SAE smoke number and opacity. It is important to remember that the smoke
number is measured at the engine, while the opacity is measured at the
stack. As can be seen, the correlation is only approximate.
A correlation also exists between SAE smoke number and particulate
mass concentration, the Champagne correlation (Reference 23). Figure 7
shows this correlation compared to actual engine data. Using Figures 6
and 7, particulate mass loadings at the engine can be compared to opacity
readings at the stack.
5.2 GASEOUS EMISSIONS
There is a very large body of data for jet engine gaseous emis-
sions. Most of these data have been collected at the engine tailpipe or
somewhat downstream. Little data have been obtained by sampling at test
cell exhaust stack exits. In spite of this lack of data, there is evi-
dence that concentration measurements for gaseous emissions made at the
stack exit are consistent with those made at the tailpipe when allowance
27
-------
A-134878
100
80 -
60 -
Q.
o
40 -
20
5.0
TF 30-P-6
TF 30-P-8 (smokeless)
J 52-P-6A
J 52-P-8A
J 65 (clean)
T 56-A-10
J 57-P-8
correlation
40 60
SAE smoke number (engine)
Figure 6. SAE smoke number versus opacity for jet engines
(Reference 22).
28
-------
O T56 (501) £ T65-GE-413
0 J57-P-8 Q T58-GE-10
Q JT8D (conventional) J52-P-6A (conventional combustor) smoke numbei
O JT8D (smokeless) J52-P-8A (clean combustor) smoke number
A T4-0 (max particulates) at max power
100
5-
01
0)
O
CT.
E
in
c
O)
"O
O
O
10.0
1.0
0.1
0
vo
20 40 60
SAE smoke number (ARP 1179)
80
100
Figure 7. Relationship between SAE smoke number and
soot density for jet engines (Reference 22).
29
-------
is made for entrained air (Reference 25). This conclusion seems reason-
able because the major gaseous pollutants CO, C02, NOX, SOX are
unlikely to react chemically or to be adsorbed or absorbed between the
engine tailpipe and the top of the cell stack. Unburned hydrocarbons are
an exception to this rule in those cases where water spray causes
condensation.
There are many data on gaseous emissions from jet engines in Refer-
ences 22, 26, 27, 28, 29, and 30. Although it is beyond the scope of this
report to reproduce these data, each major pollutant gas is identified and
briefly discussed in the following sections. In some cases, emission
factor data are summarized.
Nitrogen Oxides
The nitrogen oxides NO and N02, which appear with limited amounts
of NpO and N^Oc, are emitted from jet engine test cells, sometimes in
significant concentrations. Nitrogen oxides are formed primarily in high
temperature, high pressure combustion reactions like those that take place
in jet engines at the higher power settings. Data taken in all studies
confirm this prediction. The larger, newer jet engines (which burn with a
higher combustion zone temperature) tend to have noticeably higher concen-
trations of NOX in the exhaust, principally NO and NOo. N02 consti-
tutes 45 to 100 percent of NOX at low engine power settings, and 10 to
30 percent at maximum power settings (Reference 30).
NO is eventually converted to N02 in the atmosphere by a slow
oxidation reaction. Therefore, nitrogen oxide concentrations are usually
reported as "total nitrogen oxides expressed as N02". Since concentra-
tions are reported by volume, this means adding concentrations of NO and
N02 plus twice the concentrations of N20 and N20g.
30
-------
Large variations in NOX concentration levels have been found for
different engines, and even between engines of the same type. Figure 8
gives NOX tailpipe concentration measurements (ppm actual) for several
common engines. All measurements were made with the engine at intermedi-
ate power level which typically gives the highest N0₯ concentration
A
levels.
The Society of Automotive Engineers' standard test method ARP 1256
specifies techniques for detecting various gaseous pollutant species. The
instrumentation method specified for measuring NO is nondispersive infra-
red (NDIR). For measuring N02, nondispersive ultraviolet (NDUV) is
preferred.
Recently, however, a considerable amount of data has been gathered
using chemiluminescent techniques to measure NO concentrations. In
A
fact, most NO measurements are currently made using chemiluminescent
A
monitors. NOX measurements made by NDIR, NDUV, and chemiluminescent
methods are believed to be reasonably accurate. The problems involved in
measuring NO for gas turbines are not significantly more difficult than
n
for other combustion processes.
Sulfur Oxides
Sulfur oxide concentrations in jet engine exhaust streams are in
general far lower than the most stringent current Air Pollution Control
District regulations. Based on maximum fuel sulfur content allowed by the
fuel specifications, the greatest fuel/air ratio (in maximum afterburner
mode), and no dilution by augmenter air, the maximum possible S02 con-
centration in the engine exhaust is on the order of 100 ppm by volume,
This theoretical value is a factor of three less than the most stringent
current S02 standards (San Diego APCD).
31
-------
Range of scatter of experimental
measurements
200 1
150
_ 125-
o
E 100'
o.
Q-
x 7C
o 75
z.
50'
25-
V^M
I
m
I
I |
^P-
I
s
?
J
^
A
J79
J52 J57-P-8 TF30
T56
Figure 8. NOX emissions from jet engines
(Reference 22).
32
-------
Measurements of SOX at the top of test cell stacks have been made.
Concentration levels far below the theoretical tailpipe concentrations
have always been recorded. Figure 9 compares actual stack measurements
made at Albany Naval Air Station with theoretical tailpipe concentrations
and several APCD limits. The stack measurements are low because of the
dilution by augmentation air, and also because the fuel had a lower sulfur
content than specifications required.
Sulfur oxide concentrations in gas turbine exhaust streams are
usually determined by standard wet-chemical methods. A recent measure-
ment (Reference 31) indicates that the ratio of S03 to S02 in aircraft
turbine engine exhausts was 0.138.
The conclusions to be drawn regarding SO emissions by jet engine
test cells seem clear: (1) because of the very clean fuel used, SO con-
A
centrations are well below regulatory requirements; and (2) measurement
methods are well developed and reasonably accurate.
Unburned Hydrocarbons
Unburned hydrocarbons (UHC) are emitted from jet engines as a
result of incomplete combustion. The UHC include gases and condensible
vapors. Jet engines usually emit the highest concentration of UHC at
idle, although the maximum amounts (Ib/hr) are emitted in afterburner
mode. Figure 10 shows UHC levels measured at the tailpipe of several
engines (Reference 22} at idle. The engines are either in compliance or
marginally in violation of Bay Area Air Pollution Control District (BAAPCD)
standards, except for the J57. At all engine power settings above idle,
UHC concentration falls to insignificant levels (Reference 19).
Unburned hydrocarbon emissions are typically measured by flame
ionization detectors. Both condensible and noncondensible hydrocarbons
33
-------
500
400 '
300
*:
100
80 '
60
40
20
tic
iy Area HI'LIJ i inn L
|
San Diecio County APCD limit
t l -
i
o
<
F
0
(^ Maximum SO;? in gas turbine engine exhaust based on maximum
specification sulfur content of fuel and maximum fuel/air
ratio (afterburning)
LJ SO;? measured at stacks by Source Emissions Team at Albany
Naval Air Station (J79 with afterburner)
Figure 9. Comparison of typical turbine engine exhaust gas
SOp concentrations with various air pollution
control district limits (Reference 22).
34
-------
I
= Range of scatter of experimental
measurements
1200
o 1000
j| 800
o
= 600
400
230
BAAPCD limit
IT
in
J79 J52 J57-P-10 J57-P-8 TF30 T56
Figure 10. Unburned hydrocarbon (UHC) tailpipe emission levels
of jet engines at idle (Reference 22).
35
-------
are included in these emissions, a fact which complicates the measurement
of particulates and (in some cases) of UHC.
In the case of particulate measurement, differences between the EPA
and Los Angeles Air Pollution Control District (LAAPCD) particulate sam-
pling trains (discussed in more detail below) can make significant differ-
ences in particulate concentrations, depending on whether condensible UHC
is considered to be particulate. In the case of UHC itself, test cell
operating procedures can significantly affect the readings obtained. For
example, the water sprayed to cool exhaust gas can cause considerable con-
densation of UHC so much so that at idle power settings, more condensed
UHC aerosol than solid particulate may be present. Some of this condensed
material will be scrubbed out by the spray water, but most of it will be
carried out the test cell stack. If sampling is being done at the cell
stack, the condensed UHC may be measured as particulate, as total hydro-
carbon, or not at all, depending on the way in which the sampling train is
set up. Some of the UHC measurement discrepancies reported in the litera-
ture have been ascribed to this cause (Reference 25).
Carbon Monoxide
Jet engine CO emissions range from 2 to 15 lb/106 Btu for various
engines at idle (Reference 19) and fall to insignificant values at higher
power settings. CO concentrations are commonly measured by nondispersive
infrared techniques. Unless scrubbers are used, concentrations measured
at the tailpipe should be very much the same as stack concentrations
(taking into account augmentation air). This is because almost no CO is
converted to C02 at the low stack temperatures common in test cells.
36
-------
5.3 PARTICULATE EMISSIONS
Mass emissions from jet engine test cells are much more difficult
to measure accurately than visible or gaseous emissions. There are three
main reasons why: (1) the nature of the particulate emitted; 2) the fre-
quent confusion between condensed unburned hydrocarbons and solid particu-
late; and (3) the fact that particles emitted by jet engine change in size
as they move away from the tailpipe. In addition to these fundamental
problems, there are several operational difficulties that arise. Jet
engine test cell stacks are often 20 feet in diameter or larger. Isokin-
etic sampling conditions are difficult to assure, because the presence of
sound baffling grossly distorts the velocity profiles, setting up large
velocity gradients and even backflows. Because of these difficulties par-
ticulate emission data tend to be incomplete.
Nature of Jet Engine Particulate
The particles emitted by jet engines are about 95 percent carbon by
weight, and 5 percent oxygen and hydrogen (Reference 32). These carbon
particles, which rapidly grow into soot in the tailpipe region, oxidize
completely at the high temperatures downstream of the tailpipe unless
quenching occurs. In turbine systems, the formation of very large soot
particles is prevented by the vigorous mixing that occurs. In gas turbine
burners, back mixing to recirculate combustion products with unburned
liquid droplets in the primary zone is deliberately induced. Quenching
occurs because combustor walls, turbine blades, and other engine internals
are cooled with excess air. Any soot particles which come into contact
with these cooled engine parts are quenched immediately.
Measuring the size of particles emitted by jet engines is compli-
cated by several factors (References 33, 34, 12). At the tailpipe, as has
37
-------
been stated, most of the participate is in the form of soot. Further away
, from the engine, however, particles composed of condensible hydrocarbons
begin to become significant, particularly at low power settings. The soot
particles are substantially submicron (on both a number and a mass basis)
at the engine tailpipe, and grow slowly by agglomeration as they move away
from the engine. By contrast, the condensed hdyrocarbon particulate rap-
idly agglomerates into particles on the order of 10 microns in diameter
(Reference 19). At high power settings, however, the exhaust stream
remains hot enough so that condensible hydrocarbon aerosols do not form.
The size of the particles emitted by jet engines has not been fully
established. Collecting and characterizing these particles under the ex-
treme conditions in the engine exhaust is a difficult task. Tests carried
out to date report average particle diameters of 0.02 to 0.06 micron, with
some instances of particles with diameters up to 0.12 micron (on a number
median basis). On a mass basis, particles are reported to average between
0.2 to 0.4 micron in diameter.
Electron photomicrography shows that soot particles from jet en-
gines are more or less spherical. Usually several particles are grouped
to form a chain. This agglomeration is probably the main reason for the
growth in size observed as soot particles move away from the engine.
Table 5 shows, for a J57 engine, the average size of soot particles at
varying distances from the engine tailpipe.
There is at present very litte information about size distributions
of the aerosol produced by condensation of hydrocarbon vapor.
38
-------
TABLE 5. PARTICULATE SIZE DISTRIBUTION FROM J57 JET ENGINE
(Reference 35)
Downstream Location from
Nozzle in Nozzle Outlet
Diameters
0
2-1/2
10
Engine Power
Approach
75% Normal
Cruise
Approach
75% Normal
Cruise
Approach
75% Normal
Cruise
Geometric Mean
Diameter, ym
0.053
0.052
0.084
0.084
0.076
0.096
-
0.13
Standard Deviation
Mean in.
1 .63
1.46
1.33
1.40
1.51
1.38
-
1.40
39
-------
Sampling Methods
The participate emitted by jet engines has been sampled mainly at
three locations in test cells. Some data has been obtained at the engine
tailpipe or a few nozzle diameters downstream, where temperatures, vibra-
tion levels, and thrust loads are very high. Because gas velocities are
also extremely high here, isokinetic sampling is difficult. Most sam-
pling at the tailpipe has been done at a fixed location and a single sam-
pling flowrate. A Method 5 sampler capable of isokinetic sampling at
supersonic velocities with full traversing capability has recently been
developed by the Aerotherm Division of Acurex Corporation with support
from the Naval Aircraft Environmental Support Office and the Air Force
Civil Engineering Center. This sampling instrumentation should soon pro-
vide much better particulate data than now exists.
Sampling conditions are much better 15 to 20 feet away from the
engine, near the end of the augmenter tube. The augmentation air is by
this point well mixed with the engine exhaust stream; the combined gas
stream is considerably cooler and is moving more slowly. Most of the par-
ticulate emission data that have been reported were collected under these
conditions.
Measurements made 15 to 20 feet from the engine tell more about
engine emissions than test cell emissions, for two main reasons. First,
the cell is almost always run dry (without exhaust cooling spray water)
V,
when sampling is done at the augmenter, so that the water spray does not
affect particulate concentration. This means that no particulate is
scrubbed out of the exhaust stream and there is no nucleation leading to
particle growth or condensation of hydrocarbon vapor. Second, the exhaust
gas is sampled before it passes through the stack with its acoustic
40
-------
baffling. As a result, the wall losses and particle reentrainment which
occur as gas passes through the stack are not taken into account.
The third location where sampling has been done is at the top of
the test cell stack. Very few attempts have been made to sample particu-
late at this location. In fact, to our knowledge, no successful attempt
has ever been made to obtain complete particulate emission data by multi-
point isokinetic sampling at the exhaust plane of a Type A test cell.
There have been a very limited number of samplings made at the exhaust
plane of smaller cells. Reference 25 discusses a very complete sampling
at the exhaust plane of a test cell with a small (6-foot diameter) stack,
testing a J57 engine. Partial sampling of a large (700 sq. ft.) test cell
stack has recently been reported (Reference 36).
A joint effort by the Environmental Protection Agency, the Coordi-
nating Research Council, the U.S. Air Force and the U.S. Navy (Reference
25) to completely characterize the emissions from a small test cell illus-
trates some of the problems that can arise'in particulate sampling from
test cells. Eight sampling points were selected at the top of the 6-foot
diameter stack. Based on the velocity profiles, this was probably not
enough to assure a completely representative sampling.
Sampling for particulate was done using both the EPA sampling train
and the LAAPCD train. The EPA train consists of a heated probe and filter,
four impingers, an ice bath, and an exhaust gas metering system. The probe
and filter are kept heated to 250°F to prevent condensation of water. As
a result, most hydrocarbon vapor does not condense. The particulate catch
is the total amount of material on the filter and in the probe. The sys-
tem is designed so that only solid particulate and hydrocarbons condensing
41
-------
above 250°F are captured on the filter and upstream of it. Hydrocarbons
condensing between 70°F and 250°F are captured in the impingers.
The LAAPCD train consists of three impingers in a 70°F bath, fol-
lowed by a filter thimble and an exhaust gas metering system. The tested
gas is thus cooled before filtration, and condensible UHC knocked
out. Unlike the EPA train, however, the condensible gaseous material col-
lected in the LAAPCD train is included as particulate. Because of this
difference, one would expect the particulate concentrations measured by
the LAAPCD method to be consistently higher than those measured by the EPA
method. In fact, just the opposite result was obtained during this
testing program. One possible cause for this anomalous result is that the
EPA matted filter is highly efficient and may exceed the capability of the
LAAPCD thimble. Generally, however, data reported in the literature for
test cell sampling shows that the LAAPCD train does give higher particu-
late mass loadings than the EPA train, as expected.
This test result shows that condensible .hydrocarbons can have a
significant effect on particulate emissions measurement. It also shows
that confusing and contradictory results can be obtained even by
experienced and knowledgeable sampling crews following standard practices.
Particulate Emissions Data
Three kinds of particulate emissions data are obtained from jet
engine test cells: tailpipe, uncontrolled stack, and controlled stack
emission measurements.
Tailpipe data are defined as measurements taken at or immediately
downstream of the engine exhaust nozzle. Because of the extremely high
gas velocities, temperatures and pressures existing in this region, mea-
surement of particulate loadings and size distributions are difficult to
42
-------
obtain. Those participate data that do exist are somewhat questionable,
because it is doubtful that isokinetic conditions were maintained during
sampling. Instrumentation is now being developed (see Sampling Methods,
Section 5.3) which will soon allow accurate tailpipe particulate data to
be obtained. Figure 11 shows representative tailpipe data for several
engines tested at two different power settings. More complete tailpipe
emission data will be presented in the report of Phase II of this study.
Uncontrolled stack data are very sparse, due mainly to the diffi-
culty of accurately sampling the very large stacks common to test cells
(see discussion in Section 5.3). Table 6 gives data obtained on a rela-
tively small (6-ft diameter) metal stack in one of the few carefully per-
formed sampling tests that have been conducted.
TABLE 6. COMPARISON OF ENGINE AND STACK PARTICULATE MEASUREMENT
Measurement Method
EPA sampling train
LAAPCD sampling
train
J57 Engine
Power Setting
IDLE
CRUISE
IDLE
CRUISE
Particulate
Engine Tai
0.041
0.076
0.025
0.016
Concentration, Grains/DSCF
Ipipe Stack Exit Plane
0.009
0.013
0.009
0.012
Tailpipe data, which were obtained simultaneously with the stack
data, are presented in Table 6 for comparison. Note that both measurement
methods used (EPA and LAAPCD) show a considerable reduction in particulate
mass loading from the engine to the stack. This is due to dilution by aug-
mentation air, by expansion of the gas at the lower downstream pressure,
43
-------
U. £U
£ 0.15 -
oo
o
c
i
(O
en
en °'10
c
-o
(O
o
1/5
1/5
£ 0.05 -
D
O
J79
D
O
D
D
>-k p~i
0 DO u
O
01
J52-P-8A J57-P-10 J57-P-8 TF30 T56-A-7
O Maximum power setting
f~l TH1 e nnu/or cottinn
P-6
P-8
P-408
Figure 11. Particulate mass loading for jet engines, measured at the tailpipe
(Reference 22).
-------
and probably also to wall losses. A summary of available stack emission
data will appear in the report of Phase II of this study.
Controlled stack data are nearly nonexistent. Only one full sized
controlled test cell stack exists (the scrubber-equipped Black Point No. 1
cell at Jacksonville Naval Air Station), and only one attempt has been
made to sample the cleaned exhaust gases. Various operational difficulties
during sampling make the results obtained of very limited value; this test
is discussed in detail in Section 6.2.1.
45
-------
SECTION 6
TEST CELL EMISSION CONTROL TECHNOLOGY
The military services recognize emissions from jet engine test
cells as a serious problem requiring investigation and solution. The U.S.
Navy, which has responsibility for investigating control technology, has
funded many research programs in this area. As a result of their research,
a variety of methods for controlling jet engine test cell emissions have
been suggested. Table 7 shows the different control technologies that
have been proposed.
TABLE 7. JET ENGINE TEST CELL CONTROL MEASURES
Thermal Converters
Electrostatic Precipitators
Fuel Additives
Fuel Atomization Improvement
Nucleation Scrubbers
Spray Towers
Packed Towers
Cyclone Separators
High Spray (Ejector) Towers
Venturi Scrubbers
Wet Cyclones
Filters
Impingement Separators
Acoustic Precipitators
Magnetic Filters
47
-------
The Navy has determined that the first five of these control tech-
nologies warrant experimental study. Most of the remaining methods have
been briefly explored and then discarded because of obvious deficiencies.
In this section, each of the five control technologies that have been
evaluated is described in some detail. A description of the method, the
current state of its development, and capital and operating cost estimates
are presented. In addition, some of the less promising concepts are
briefly described.
Control technologies are considered here mainly as retrofit devices
for existing test cells. In view of th'is, any control device must be able
to function within the operative parameters of the test cell to which it
is added. The pressure drop of the control devi ce^for example, is one of
the most important considerations: The operational characteristics of the
x^engine under test can be affected when back pressures exceed about 20-inch
water (Reference 10). Current acoustical treatment of the exhaust stream
causes a back pressure of about 10-inch water. This means that a control
device fitted to the exhaust stack should not cause a pressure drop of
greater than about 10 inches since a mechanical means of exhausting the
test cell to overcome high control device pressure drops is very expensive
due to the extremely high gas flowrates involved.
Any control device considered for jet engine test cells must be
able to withstand the very high sound levels existing in the gas exhaust
stream. Average sound levels at the augmenter range from 170 dB for a J57
up to 180 dB for a J75 (Reference 16). The reinforced concrete walls of
test cells crack fairly frequently.
Water availability is an important consideration for some cleanup
devices, particularly wet scrubbers. At many installations, the water
48
-------
supply is limited. Any device which uses large amounts of water would not
be feasible at these locations. Nucleation scrubbers, for example, have
the highest water usage of the cleanup devices considered here. Even
though the scrubber packing irrigation water can be continuously cleaned
and recycled, a good deal of water is lost in the quench spray system.
Nucleation scrubbers must saturate the exhaust gas downstream of the aug-
menter in order to produce the nucleation and particle growth necessary
for particle collection. The amount of water evaporated to saturate the
exhaust gas varies with engine power setting, but in general will always
be greater than that required for an uncontrolled cell.
The physical dimensions of a cleanup device and its support equip-
ment are also important for retrofit installation. Test cells are commonly
built side-by-side in pairs sharing control and ready areas. In some
cases (for example at Tinker AFB) many cells are positioned in a row with
minimal clearance betweeen them. A control device which takes up a lot of
room on either side of the cell stack will probably not be suitable for
pairs or groups of cells. Similarly, the space required for support
systems could become a factor. In some locations, the ground space neces-
sary for the cooling tower, pumping station, and water cleanup plant asso-
ciated with nucleation scrubbers, for example, may be unavailable.
These restrictions and limitations, combined with the diversity in
test cell design noted earlier, make a standard cleanup device for all
test cells impractical (with the obvious exception of those methods such
as fuel additives that require no alteration of the test cell structure).
Different cleanup technologies may be required in different locations
because of water availability, fuel cost, electricity cost, physical space
availability, and local air pollution control regulations.
49
-------
6.1 ELECTROSTATIC PRECIPITATOR
The electrostatic precipitator (ESP) is an obvious choice for a
test cell cleaning device. It is efficient in collecting the micron- and
submicron-sized particles that make up the test cell exhaust plume. It is
capable of operating at elevated temperatures and is a well developed,
proven method in current use in a number of diverse applications. ESP's
are also low pressure drop devices, an important consideration for the
test cell application.
Particle collection in an ESP is accomplished by allowing the
particulate-laden gas to pass close to a wire, point, or sharp edge which
is raised to a high enough electrical potential in relation to other
nearby parts of the apparatus to continuously ionize the gas near the
wire. The ions thus created rapidly sweep through the gas to be cleaned.
Particles present attract and then adsorb the ions, acquiring an electro-
static charge. In a single-stage precipitator, the charged particles are
carried to nearby low potential surfaces by the field which exists between
the ion source and the collecting surfaces. In a two-stage ESP, the par-
ticles are charged as described and then collected downstream in a separ-
ate high-field region.
The efficiency of the ESP is limited by the ion flux density in the
charging zone, the particle size, the magnitude of the field in the col-
lecting zone, the distance a particle must travel to a collecting surface,
the particle resistivity, and the residence time of a particle in both the
charging and collecting zone. The designer has little control over charg-
ing and collecting fields. These are always the maximum values which can
be attained without excessive sparkover. The performance of an ESP for a
given gas stream is thus determined by the residence time of a particle in
50
-------
the ESP, or by the gas velocity and available collection area for any spe-
cific precipitator.
In industrial applications, gas velocity commonly ranges between 3
and 15 ft/sec (Reference 8) with 8 ft/sec (500 ft/min) being considered a
maximum for good practice in most applications. This low operating veloc-
ity is a drawback of test cell use. For a cell designed for 500,000 acfm
(typical of a TF 30 engine with conventional augmenter), the required pre-
cipitator cross-sectional area to maintain a 500 ft/min gas velocity in
the ESP would be 1000 ft2. Providing this large an area is the main rea-
son for the high cost of installing retrofit ESP's on test cells.
There are several peculiarities of test cell operation that con-
strain ESP design. The carbonaceous nature of the particulate makes fire
a real danger if the precipitator is operated dry. This danger is increased
by the inevitable sparking that occurs between high voltage elements in
precipitators. In general, however, because the exhaust gases are usually
cooled by water sprays at the augmenter, the gas leaving a test cell often
contains liquid water in the form of entrained droplets and condensation.
This water creates several severe problems for the designer of an
ESP for a test cell. First, the damp or wet particulates make a sticky
paste that clings tenaciously to collecting surfaces. Some effective
means of removing this material must be provided. Secondly, and more
seriously, the carbonaceous particles, when dampened with water, make a
f
very conductive paste. If conductive material is allowed to build up on
insulating components inside the precipitator, arcing and system failure
may occur. Some means of periodically cleaning all internal parts of an
ESP designed for test cells is therefore necessary. Wet ESP's, that
51
-------
operate with a continuous flow of water over the collection plates, may
solve these problems. However, there is no present experience with wet
ESP's on test cells.
6.1.1 ESP Experimental Apparatus
An experimental program to evaluate the performance of an electro-
static precipitator has been conducted at Jacksonville Naval Air Station
by United Engineers and Constructors, Inc. A final report on the results
of the program is due to be issued in March 1976.
The test cell which has been used for the ESP tests was Black Point
No. 1 at Jacksonville Naval Air Rework Facility. This is the same test
cell on which the prototype nucleation scrubber is mounted. As shown in
Figure 12, a bypass port is provided in the back wall of the test cell. A
12 inch by 12 inch duct extends into the cell exhaust area, approximately
coaxial with the augmenter. A venturi section immediately outside the
cell is used to measure the gas flow through the experimental test setup.
The gas stream is then expanded to 30 inches by 48 inches, the cross-
section of the ESP. A 25-foot length of duct stabilizes the gas flow, at
which point a sampling port is provided. After passing through the pre-
cipitator, the gas enters another section of straight duct, toward the end
of which is another sampling port. The gas is then exhausted to the
atmosphere.
The gas flow through the test duct is powered by the positive pres-
sure in the test cell exhaust space. No auxiliary blowers are required,
but note that the test duct expands from 12 inches by 12 inches at the gas
takeoff to 30 inches by 40 inches at the ESP. This is because the gas
must be slowed down for effective operation of the precipitator. For most
of the tests that were made, the gas flowrate in the test section was about
52
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AUGMENTS* TUBE
TFST EM6INE -I
cn
CO
66' 0"
8'0 8'0" 6'0 37
FALSE BOTTOM .
IN DUCTWORK
CAS DISTRIBUTION.
BAFFLE
.PROTOTYPE
PRECIPITAT0R
OUTLET SAMPLING
POUT
Figure 12. Electrostatic precipitator experimental setup -Black
Point No. 1 test cell (Reference 9).
-------
9000 scfm. Since gas flow in the test cell stack is about 600,000 scfm,
the test apparatus was about 1/65 of full scale.
Figure 13 shows details of the ESP, which was provided by American
Air Filter, Inc. As shown in the plan view, the precipitator is a double
two-stage ESP. In effect, it is two identical units in series. This
design increases the overall collection efficiency of the device (compared
to a single ESP).
The dirty gas enters the precipitator through a distribution plate
and flows past wash nozzles to the ionizing section. The ionizer section
consists of a parallel array of tungsten wires, separated by grounded
metal plates. The wires are raised to a potential (about 13,000 V) high
enough to cause ionization of the air near the wires, and movement of air
ions in the space between the wires and the grounded metal plates. Ions
attach themselves to particles passing through this region of high-ion
density, giving the particles an electrostatic charge.
The gas, carrying the charged particulate, then enters the collect-
ing section. This is a parallel array of metal plates which are alter-
nately grounded and raised to about 6000 volts. The electrical field
between the plates in the collecting section causes the charged particles
to migrate to one of the plates, where they are deposited.
After leaving the collecting region, the gas passes through an
identical charge/collection section, where some of the particulate not
collected in the first stage is trapped. The gas then leaves the
precipitator.
After the ESP has been in operation for some period of time, the
accumulated deposit on the collection plates and on the insulating compo-
nents must be removed. The method used in the Jacksonville tests was
54
-------
CJ1
en
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Elevation
Legend
Plan
Gas distribution baffle
Ionizing section
Collecting section
Trans former-rectifier
Wash nozzles
Deterpent pump
Solenoid valve
Wash control unit
Flexible duct connection
Support legs w/vibration isolators
Figure 13. Electrostatic precipitator test unit (Reference 9).
-------
to direct a high pressure spray of water and detergent at the interior
parts of the ESP- Wash nozzles were premanently mounted inside the
precipitator, and a fully automatic sequencer performed the washdown. The
manufacturer of the ESP recommended washdown every 8 hours. Somewhat more
frequent cleaning was found to be desirable.
6.1.2 Experimental Results
A fairly extensive series of tests of the scale model ESP were per-
formed at Jacksonville. Sampling for particulate was done using Method 5
procedures at the ports marked "inlet sampling port" and "outlet sampling
port" on Figure 12.
Collection efficiency varied considerably from one test to another.
ESP efficiencies ranged from over 95 percent in some cases to very low or
even negative values in others. To add to the confusion, two different
types of efficiency data were collected during evaluation tests of the
scale model ESP- The manufacturers of the ESP (American Air Filter Com-
pany) performed single point isokinetic sampling measurements immediately
upstream and downstream of the ESP- Their method measured dry particulate
only; typically, efficiencies between 80 and 95 percent were recorded.
Another series of efficiency measurements was made by Jacksonville
NARF personnel, using EPA Method 5. For these tests, particulate was
determined by combining the filter catch with the impinger catch. Con-
densibles were thus defined as particulate. The Method 5 tests used a
20-point sampling grid at the inlet and outlet of the unit. An average
particulate removed by the ESP of 59 percent was measured for all of the
Method 5 determinations.
Comparison of the efficiency results obtained with the AAF method
and EPA Method 5 is not really meaningful, since dry particulate was being
56
-------
measured in the first case, and dry participate plus condensibles in the
second. Also, the AAF tests were done at a single point, rather than over
a grid.
Finally, Jacksonville NARF personnel believe that inability to
maintain constant engine loads during the long times required for Method 5
sampling may have affected those data. For purposes of discussion, the
EPA Method 5 results will be used, since their data were obtained using
equipment and procedures specified by most regulatory authorities.
Table 8 shows three measurements on a J79 engine. The operating
personnel at Jacksonville consider these "good" data, representative of
the overall performance of the system. The overall particulate removal
efficiency of the ESP varied between about 52 percent and 65 percent for
the data shown in Table 8.
There are several possible reasons for the low collection efficien-
cies in these tests. As indicated in Table 8, the gas velocities at the
duct were 700 fpm. This means that at the ESP, they would have been about
500 fpm. This velocity is at the top of the range commonly used and may
have contributed to low efficiency, especially for small particles.
Smaller particles move toward the collection plates at a lower velocity
than do large ones. As a result, small particles (such as those emitted
by turbine engines) are more likely than large ones to pass uncollected
through an ESP if the gas velocity is too high.
There were several operational problems noted during the evaluation
of the ESP device. One was a recurring problem with shorting in the first
ionizing section. Operating personnel believe that this problem was
caused by excessive water droplets carried over from the exhaust cooling
sprays, and that a mist eliminator upstream of the ESP would be necessary
57
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TABLE 8. EMISSION DATA FROM THE ELECTROSTATIC PRECIPITATOR AT JACKSONVILLE NAVAL
AIR STATION, BLACK POINT NO. 1 TEST CELL - J79 ENGINE
on
CO
Date
Scrubber water flow at #1 sump gal /mi n
Vol. of dry gas sampled, scf
Stack flowrate, scfm, dry
Stack gas velocity, at stack
conditions, fpm
Moisture, % by volume
Stack gas temp, degree F.
Isokinetic sampling rate, %
Parti cul ate Results
(a) Probe and filter catch
grains/scf dry, x TO"3
(b) Total catch
grains/scf, dry, x 10~3
(c) Parti cul ate from #1 sump water sample
grains/scf x 10~3
Particulate Removal Efficiency
Based on air sample (a), %
Based on air sample (b), %
Based on total (air and water, a+c), %
Based on total (air and water, b+c), %
Entrained Water Removal, %
Inlet Outlet
4-17 4-17
9.66
92.79 81.66
9276.0 8149.4
763.8 665.8
15.75 15.15
132 131
97.5 97.6
6.17 2.90
7.30 3.54
5.41
53.0
51.5
74.9
72.1
11.5
Inlet Outlet
4-18 AM 4-18 AM
9.89
87.99 83.31
8404.3 7621.5
703.8 620.5
17.13 14.89
132 131
102.0 106.0
3.48 1.05
3.92 1.20
5.64
69.8
64.9
88.5
86.8
44.8
Inlet Outlet
4-18 AM 4-18 AM
9.61
84.27 84.82
8607.6 7920.2
698.0 698.3
16.66 15.39
132 131
95.0 104.3
3.14 1.05
3.21 1.27
5.14
66.6
60.4
87.3
84.8
22.7
-------
for a full-scale unit. There was also a problem with the automatic wash-
ing system: an increase in water pressure over that originally provided
was required for satisfactory operation. After proper water pressure was
supplied, the cleaning system appeared to work satisfactorily. The clean-
ing cycle took about 20 minutes and appeared to remove deposited particu-
late from the ESP as it was designed to do. The precipitator could be run
immediately after the cleaning cycle. If the ESP was allowed to stand
unused for a long enough time to completely dry the collection plates,
however, residual particles not removed by the automatic cleaning system
would be reentrained into the gas stream and substantially lower the
apparent efficiency in subsequent test runs.
6.1.3 Costs
United Engineers and Constructors, Inc., have estimated the capital
and operating costs for retrofitting test cells with electrostatic precip-
itators capable of attaining performance levels similar to those reported
here. The following is quoted from Reference 9:
"Capital costs for a pollution abatement system incorporating
the precipitator concept would be on the order of $850,000 for a
500,000 acfm system or $1,690,000 for a 1,200,000 acfm system based
on a 500 fpm design velocity.
Annual operating costs for a pollution abatement system incor-
porating the precipitator concept can be on the order of $32,000
for a 500,000 acfm system testing 500 J79 engines per year or
$65,000 for a 1,200,000 acfm system testing 500 350-lb/sec engines
per year."
These costs are based on complete installation of a double two-
stage ESP system, including an automatic washing system and a pressure leaf
59
-------
filler for removing participate from the washwater. The operating costs
include maintenance and electric power consumption. Operating personnel
at Jacksonville NARF have stated that they expect much higher maintenance
cost, based on their experience with the scale-model ESP, but they could
not provide expected maintenance cost figures.
6.2 NUCLEATION SCRUBBER
At the present time, only one test cell cleanup method has been
evaluated in full scale tests. This is the Teller Environmental Systems,
Inc., (TESI), nucleation scrubber installed on the Black Point No. 1 test
cell at the Jacksonville Naval Air Station. This scrubber consists of
three parts: (1) an exhaust gas pretreatment section, in which the size
of the particles is increased by nucleation of water vapor; (2) a proprie-
tary packed bed scrubber section where the particulate is transferred to
the scrubber water; and (3) a water cleanup and sludge removal system (not
provided as part of the Jacksonville prototype scrubber facility).
A schematic diagram of the prototype system installed at Jackson-
ville is shown in Figure 14 (Reference 10). Exhaust gases leaving the
engine are carried into the augmenter tube, where quench water is injected.
This water changes the dew point of the gas to the proper conditions for
nucleaction. Nucleation occurs in the augmenter tube and stack. The
exhaust gas then passes through a packed bed scrubber section where irri-
gating water removes the particulate from the gas. Dirty scrubbing water
is piped to a nearby river.
A special augmenter was designed and installed in the TESI system
to keep the volume of exhaust gases to a minimum. With conventional
augmenters, the ratio of entrained air to engine exhaust gas is about 2.5
60
-------
Scrubber
water
inlet
Augmenter
tube
ttttt
Exhaust gases
Packed
bed
Demist
section
Wind
screens
Used
scrubber
water
Figure 14. Nucleation scrubber schematic.
61
-------
in afterburner mode. With the special augmenter (Figure 15), the flow is
choked down to give a ratio of 1.0. This significantly reduces the flow-
rate of gas to be cleaned, which means that the superficial scrubber area
is also smaller. The TESI augmenter is also designed for efficient quench-
ing of the exhaust gas stream.
The augmenter is designed with a converging throat and a vena con-
tracta section with pentrating radial sprays and width large enough to
permit recycle. It also has a diverging zone with circumferential sprays
and an annulus between the diverging zone and the outside shell to permit
recycle of gas and entrained water droplets to the vena contracta zone.
The quantity of water injected and the engine exhaust and entrained air
flows are such that the submicron particles emitted by the engine act as
condensation nuclei for water vapor in the saturated or supersaturated
regions downstream of the augmenter. In this way, particles grow to a
size of 3 to 5 microns (Reference 11).
After leaving the augmenter, turning vanes direct the exhaust gases
vertically up the cell stack. At the top of the stack, other turning
vanes direct the gas horizontally into two packed scrubbing beds con-
structed on the periphery of the stack. Each bed is 30 feet long by 18
feet high by 6 feet thick. The inner 5-1/2 feet of each bed consist of
2-inch Tellerettes ( a proprietary packing material), irrigated with face
sprays and overhead distributors. The outer 9 inches is a demisting sec-
tion. It is packed with 1-inch Tellerettes and is not irrigated.
The maximum irrigation rate of the two packed beds is 8300 gpm (used
during operation of the J79 engine in the afterburner mode). This flow is
reduced to 400 gpm in military mode, and only quench water is required
below cruise levels. Because of the high cost of electricity to provide
62
-------
Augmenting
air
Engine exhaust
CO
Augmenting
air
Outlet flow
Figure 15. Teller Environmental Systems, Inc. augmenter.
-------
scrubber irrigation water at maximum irrigation levels, it is important to
reduce water flowrates as much as possible.
Unfortunately, accurate particulate emission data from the proto-
type scrubber is not available. Sampling at the face of the scrubber bed
is a formidable task, and has only been attempted once. For this one
test, multiple sampling nozzles were arranged in parallel at 12 test
points on the outlet side of the paced bed. Isokinetic sampling condi-
tions were not maintained. .Instead, a constant nozzle suction velocity of
8 ft/sec was held. Under ideal conditions, exhaust gas exit velocities of
6 to 10 ft/sec were expected. In reality, however, the wind caused severe
disturbances. Air sampled by the nozzles were carried through manifold
pipes to a sampling train.
A sampling run consisted of the following sequence: (1) start
flushing water flow; (2) engine start to idle; (3) engine runup to desired
thrust; (4) take sample; (5) engine runup to blow out gases; (6) engine
shutdown; (7) stop flushing water flow. During all this time the sampling
nozzles were in place. Although the gas samples were drawn through the
nozzles for only a part of this time, particulate material could
accumulate on and in the nozzles and their manifold during the entire
time. Since the material accumulated in the nozzles and manifold could
not be distinguished from the rest of the sample, accumulation was added
as an unwanted but unavoidable portion of the sample. In addition, a
great deal of water was sprayed into the gas stream upstream of the
scrubber and the intake nozzles. During the sampling, some of this water
could be seen passing down the flexible tubing to the wet impinger, where
it accumulated, contributing to the sample.
64
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With these sorts of problems, the validity of the participate sam-
pling data obtained is questionable. The results are shown in Table 9.
TABLE 9. NUCLEATION SCRUBBER AT JACKSONVILLE NAVAL AIR STATION,
EMISSION LEVELS FROM BLACK POINT NO. 1 TEST CELL
Engine
J79
TF30
J79
Mode
Idle
Normal
Military
Idle
Normal
Military
Idle
Normal
Military
Max. A/B
Part icu late
Emissions
Grains/scf
0.0024
0.0029
0.0024
0.0019
0.0014
0.0018
0.0052
0.0029
0.0062
0.0033
Ringelmann
Less than 1/2
H ii n
ii n n
n n n
n n n
n n n
n n n
n n n
n n n
n n n
Attempts were also made to determine the concentration of CO, S0£
and hydrocarbons with the same sampling system used for particulate col-
lection. Because of various equipment failures and analytical difficul-
ties, reliable gaseous emission data were not obtained.
In spite of the lack of reliable quantitative data, independent
observers were impressed by the performance of the TESI nucleation scrub-
ber system. The following is quoted from Reference 10.
"During a visit to Jacksonville Naval Air Station by the Con-
tractor, a TF30 was tested in the cell. The test cell cleanup
system was run under two modes of operation, scrubber water on and
scrubber water off. One immediate effect of the presence of
65
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the scrubber system regardless of the operating mode was the
lowering of the noise level. In an adjacent cell, a TF411 engine
(15 000 Ibs thrust) was being run at military rating. The noise
was such that even at a distance of over 500 feet conversation was
almost impossible. When this engine was shut off and the TF30 run
at military rating it was possible to converse within 50 feet of
the test cell without difficulty.
The test cell was first operated with the scrubber water in
use. During engine idle it was noticed that despite the 1100 gpm
being injected into the augmenter tube and the 8000 gpm being
showered down on the scrubber section, the exhaust (gas) was
noticeably dirty. Yet the scrubber exhaust water was only slightly
blackened by the collected particulate matter. Little, if any,
water vapor appeared at the scrubber exhaust ports. Since one side
of the scrubber section contained only the demisting section, this
side tended to produce the water vapor mist. Considerable dirtied
water was being exhausted from a tube placed in the rear of the
augmenter tube during idle. This seemed to indicate that the
injected water had condensed prior to exiting the augmenter tube.
As the engine power was increased to military rating, a
dramatic difference in the exhaust was noticed. The scrubber
exhaust became black with particulate matter. The water ceased
flowing from the augmenter tube drain and air began being sucked
into the rear of the augmenter tube through the drain. This last
occurrence would indicate that the water vapor no longer was
condensing in the augmenter tube but was being carried further
downstream. The exhaust from the test cell became quite clean and
heavily laden with water vapor. By standing under the plume, a
slight mist could be felt. Nevertheless, it was mentioned that
there had been no ill effects experienced from the mist at the
base. Prior to installing the cleanup system, the vapor plume
would extend hundreds of feet and the resulting mist and noise were
objectionable. Despite the lack of the 5-1/2 feet packing on one
side of the scrubber, the plume from both sides seemed to be
equally dense and equally as long.
For the second phase of the test, the 800-gpm scrubber water
was turned off with only the 1100 gpm of augmenter water being left
on. At idle power the same phenomena of dirty exhaust gas and the
slight wisps of water vapor were again observed. The scrubber
exhaust water (the water vapor carried downstream from the aug-
menter tube and being condensed without benefit of scrubbing water)
was much dirtier than observed earlier at idle when the scrubbing
water was on, but the flow was less. The augmenter tube exhaust
water exited through the drain was just as dirty to the naked eye
as observed previously.
Lastly, the engine was increased to military rating. The
scrubber exhaust behaved as before at military rating, producing a
100-foot plume of clean water mist.The augmenter tube drain
behaved as before, ceasing flow and sucking air in. Only the
scrubber exhaust water changed characteristics. It became dirty as
before, but the flow increased from a light flow experienced under
idle rating to a more moderate flow under military rating."
66
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Table 10 presents a summary of these observations. Note that the
performance of the scrubber was observed to be about the same with and
without scrubber irrigation water. Personnel at Jacksonville NAS have
also suggested that the amount of irrigation water and the thickness of
the packing can probably be considerably reduced without lowering system
performance. This, if confirmed, would have some effect on capital cost,
and a major effect on operating costs.
Personnel from Acurex and EPA viewed the scrubber system in opera-
tion on February 4, 1976. A TF41 engine was being tested in Black Point
No. 1, and a similar engine was being tested in a nearby cell, which was
identical except for the scrubber. The scrubber irrigation water and
quench water were turned on first. The engine was then started, held
briefly at idle, and then moved up to the 90-percent power setting where
it was held for about 5 minutes. A very heavy white plume was produced at
the faces and top of the scrubber. The plume lasted for about 100 feet
downwind in the very light winds prevailing. After the steam plume evap-
orated, no trace whatever of a pollutant cloud could be detected. A very
rough visual estimate was made that perhaps 20 to 30 percent of the steam
produced came from the top of the scrubber assembly (presumably through
leaks) rather than through the faces of the scrubber beds. The color of
the plume coming from the top was no darker than the plume coming from the
faces.
After a few minutes of operation at 90-percent power setting, the
engine was reduced to idle setting for about 5 minutes more. At idle, the
velocity of the plume from the scrubber was markedly lower, but it looked
about the same as the plume from the 90 percent power setting. A clean
white plume persisted about 50 feet downwind, where the water evaporated
67
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TABLE 10. OBSERVATIONS DURING TEST CELL CLEANUP SYSTEM TEST
(Reference 10)
Scrubber Mode
Scrubbing water
on (8000 gpm)
Scrubber water
off
Engine Mode Test Cell Exhaust
Idle Dirty mist
Water vapor wisps
through unpacked
sides
Military Clean cloud
Water vapor plume
about 100 ft long
Idle Dirty mist
Water vapor wisps
through unpacked
sides
Military Clean cloud
Water vapor plume
about 100 ft long
Scrubber
Water Exhaust
Slightly dirty
Heavy f 1 ow
Dirty
Heavy flow
Slightly dirty
Light flow
Dirty
Medium flow
Augmenter Tube
Water Exhaust
Dirty
Heavy flow
No flow, air
being sucked in
Dirty
Heavy flow
No flow, air
being sucked in
68
-------
No trace of a residual pollutant plume could be observed. Relative humid-
ity was very high, however, and this made steam plumes very dense and per-
sistent. By the time the stream dissipated the plumes were greatly spread
out. This may have contributed to our inability to detect a residual pol-
lutant plume.
After the scrubber-equipped cell was shut down, a series of test
were begun in the adjacent uncontrolled cell on a nominally identical TF41
engine. This provided an interesting opportunity to compare plume appear-
ance directly. At idle, the plume from the uncontrolled cell was essen-
tially invisible, with only a slight darkening apparent. At 100-percent
power setting, a very definite dark plume was visible. Several Ringelmann
readers present agreed that, although proper conditions for accurate opac-
ity determination were not present, the plume opacity corresponded to
approximately 20 percent. The excellent scrubber performance must there-
fore be weighed against the fact that a relatively clean engine was being
tested. Jacksonville NARF personnel observed that the TF41 opacity of 20
percent at military power setting was consistent with past experience at
the relatively small, close-coupled, metal Black Point cells. They said
that if the same engine were to be tested in a longer concrete cell a few
hundred yards away, the plume at military power would have an opacity of
at least 40 percent.
Figures 16 and 17 show the Black Point No. 1 test cell and nuclea-
tion scrubber in operation. These pictures were taken in 1971, but
represent the plume appearance we saw fairly accurately. Figure 16 also
shows the ductwork extension out the back of the cell that was used to
test the scale model scrubber and electrostatic precipitator.
69
-------
Figure 16. Nucleation scrubber at Jacksonville NAS.
-------
CO
Figure 17. Aerial view of Jacksonville scrubber.
-------
6.2.1 Scale Model Scrubber Tests
Even through good sampling data from the full-scale prototype
scrubber is lacking, considerable information has been obtained on a 1/50
/
scale model known as the pilot scrubber, attached to the Black Point No. 1
test cell at Jacksonville NAS. Essentially the same ductwork was used for
the pilot scrubber tests as was later used for the electrostatic model
experiments. The differences were that for the scrubber tests the inlet
duct size was 4 feet x 4 feet in cross section and gas flow measurement
was achieved with an adjustable orifice. The ESP tests were conducted
with a 30 inch x 48 inch inlet duct and a venturi upstream of the ESP.
Figure 12 shows the ducts which led engine exhaust from the cell to the
scrubber. Figure 18 (Reference 13) shows the pilot scrubber.
The pilot scrubber was designed expressly to overcome the sampling
problems noted with the full-scale prototype scrubber. Gas velocities and
scrubber bed thicknesses on the pilot scrubber were made similar to those
on the full-scale prototype unit. Pilot model sampling procedures were
evaluated by EPA representatives, and were determined to be satisfactory.
It is therefore believed that the data obtained with the pilot scrubber
are representative of actual nucleation scrubber performance.
In a sample run, an engine was set at a constant power level. Air
flow through the pilot scrubber was set by adjusting the orifice at the
entrance to the system ductwork. The flow of water in the augmented and
pilot scrubber were set and stabilized. Air sampling was done at the
locations marked "inlet sampling port" and "outlet sampling port" on
Figure 12. At each sampling port, air samples were taken at 25 locations
specified by a 5 x 5 grid uniformly spaced within the 4 feet by 4 feet
duct. Isokinetic sampling methods and train components were as required
75
-------
Flowmeter
Inlet gas
sampling port
Drain for
Sump No. 1
Outlet gas
sampl ing .port
Packing box.
4' x 4' x 6'
Drain control valve
Drain for
Sump No. 2
Figure 18. Pilot scrubber system on Black Point No. 1 test cell at the Jacksonville
Naval Air Station.
-------
for Method 5. Air was sampled before and after the scrubber section. In
addition, water samples were taken at the locations marked "Sump No. 1"
and "Sump No. 2" on Figure 18. The sample from the No. 1 sump gave the
concentration of particulate which was removed by the action of the water
sprayed into the exhaust stream at the engine tailpipe, by particle im-
pingement on the augmenter tube and all stack internals, and by the water
condensation and fallout that occured between the tail pipe and the
scrubber face.
Part of the difficulty in assessing the performance of any scrubber
system requiring exhaust gas quenching is that the augmenter with its
water spray system removes particulate independently of the packed
scrubber bed. Therefore, while the overall system may be highly efficient
in removing particulate, the scrubber section (as measured by air sam-
pling) may be much less effective. The relative particle-removing effi-
ciency of a fully quenching system, compared to a conventional augmenter
with water spray cooling is unknown. In the data reported in Reference
13, and repeated here, both scrubber efficiencies (based on air sampling)
and overall efficiencies (including particulate collected in the No. 1
sump) are presented.
Table 11 shows a representative set of data obtained with the pilot
scrubber system on three different days. Particulate removal efficiency
of 51 to 62 percent for the packing section, and overall efficiency, in-
cluding both packing and augmenter spray collection, of 77 to 81 percent
were representative of the much larger number of data points given in
Reference 13.
Among the parameters investigated in the pilot model scrubber tests
were type of packing, effect of packing thickness, and effect of water
77
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TABLE 11. TEST RESULTS ON PILOT SCRUBBER AT THE BLACK POINT NO. 1 TEST CELL
AT JACKSONVILLE NAVAL AIR STATION, USING A J79 ENGINE (REFERENCE 13)
00
1
Date
No. ft. of packing
Engine operating condition
Flow at #1 Sump gal./min.
Flow at #2 Sump gal./min.
Vol. of dry gas sampled, SCF
Stack flowrate, SCFM, dry
Stack gas velocity, at stack
conditions, f.p.m.
Moisture, % by volume
Stack gas temp, degree F.
Isokinetic sampling rate, %
Particulate Results
(a) Probe and filter catch
Grains/SCF, dry, x 1CT3
(b) Total catch
grains/scf, dry, x 10 3
(c) Particulates from #1 Surnj^ water
grains, scf, x 10'3
Particulate Removal Efficiency
Based on air sample (a), %
Based on air sample (b), %
Based on total (air and water, a+c),
Based on total (air and water, b+c),
Entrained Water Removal, %
Inlet
1-30
3
Normal Rating
12.3
.2
73.04
6539.8
542.4
16.6
129.6
104.4
6.90
7.27
sample
10.69
55.2
53.1
% 82.4
% 81 . 0
42.5
Outlet Inlet
1-30 1-31
3
Normal Rating
16.2
.5
62.75 91.46
5448.0 8919.5
437.1 746.1
14.1 17.4
126.8 130.2
107.7 95.9
3.09 6.67
3.41 6.85
9.33
62.0
60.9
84.2
83.5
75.3
Outlet Inlet Outlet
1-31 2-1 AM 2-1 AM
3
Normal Rating
14.7
75.0
85.15 91.89 75.01
8075.4 9046.4 7510.6
638.8 760.4 566.4
12.9 17.7 10.5
127.6 131.0 115.4
98.60 95.0 93.4
2.53 6.55 3.20
2.68 7.06 3.74
9.30
51.2
47.0
79.8
77.2
67.0
-------
irrigation rates over the packing. It was found that none of these vari-
ables, within the ranges tested, significantly affected the scrubber bed
collection efficiency for particulate. These findings suggest that the
full-scale prototype scrubber and the four new scrubber-equipped cells
under construction at Jacksonville and Norfolk may be overdesigned. All
were designed with thick packing beds and high scrubber water irrigation
rates, which may not be necessary.
Gaseous emission measurements of the pilot model scrubber were con-
ducted by personnel from the Aircraft Environmental Support Office, Naval
Air Rework Facility, North Island, California. Measurements of carbon
monoxide, carbon dioxide, nitric oxide and total nitrogen oxides were made
at both the inlet and outlet sides of the scrubber. The effect of water
flowrate and packing depth on gas concentrations was investigated. For
all tests, the average change in the concentration of each of the gases
from the inlet to the outlet sides of the scrubber varied from 0 to 5 per-
cent. It was concluded that the scrubber had little or no effect on the
removal of CO, C02, NO, and NOX (Reference 14).
6.2.2 Proposed Scrubber Facilities
Based on the results obtained with the prototype scrubber on the
Black Point No. 1 test cell, four new scrubber-equipped test cells are now
under construction two at Jacksonville NAS and two at Norfolk NAS.
These are very large cells, designed for engines in the 70,000-lb. thrust
category, whereas typical Type A cells are designed for 20 to 25,000 Ib.
thrust engines. The cells themselves, therefore, and the associated
scrubber systems are considerably larger than the Black Point No. 1 cell.
The new cells will be equipped with complete scrubber installations,
including water cooling and water treatment systems that
79
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allow closed-loop water recyle. Each cell scrubber bed will be supplied
with 14,000 gpm of irrigation water, compared to 8,000 gpm maximum for the
prototype scrubber. Initial engine testing at the new Jacksonville cells
is scheduled for fall 1976, with full operation scheduled for December
1976. The Norfolk cells are approximately 1 year behind.
6.2.3 COSTS
Since a full scale prototype retrofit scrubber has been in opera-
tion for several years, and four new scrubber-fitted test cells are near-
ing completion, it might be thought that the cost of providing scrubbers
for retrofitting existing test cells could be readily established. Unfor-
tunately, this is not the case. We requested separate estimates from the
Navy and a private contractor and found these to differ considerably.
These differences existed despite the use of a uniform cost estimation
basis through the stipulation of the following conditions:
The scrubber was to be retrofitted to a Type A permanent test
cell capable of testing engines of up to about 20,000-lb. thrust
A complete facility was to be provided including scrubber,
cooling tower, water cleanup plant, all site modifications, and
installation of all equipment
§ Costs of bringing utilities (water, electric power) to the test
cell site were not to be included
Three cost estimates were received. An estimate prepared by the
Naval Air Systems Command (Reference 15) in early 1975 is shown in Table
12. A separate estimate prepared in January 1976 by personnel at Naval
Air Rework Facility, Jacksonville, is shown in Table 13. A very detailed
cost proposal prepared by the original system contractor for the
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TABLE 12. SCRUBBER RETROFIT COST ESTIMATE -- NAVAL AIR SYSTEMS COMMAND
Item
Cost
Packed scrubber
Cooling tower basin
Cooling tower
Water system for irrigation and quench
Water treatment plant
Exhaust stack modifications
Electrical work
$ 515,000
160,000
250,000
280,000
160,000
50,000
100.000
Total $1,515,000
TABLE 13. SCRUBBER RETROFIT COST ESTIMATE -- JACKSONVILLE NARF
Item
Cost
1. Cooling tower well
2. Water treatment system
3. Scrubber and quench water
system including cooling tower
4. Cooling tower and water
treatment stairs
5. Water treatment building
(miscellaneous)
6. Columns, beams, and
miscellaneous for cooling
tower pipe support
7. Cooling tower and water
treatment building --
general construction work
8. Upper concrete work for
scrubber enclosure including
additional foundation
9. Additional piles for
building structure
10. Extra electrical work on
outside and inside of cell
Total
$ 31,138
250,000
731,000
21,995
1,560
60,450
251,515
250,000 (due to pollution abate-
ment). Prorated from a
larger figure.
40,000 (due to pollution abate
ment). Prorated from a
larger figure.
307,077 (due to pollution abate-
ment). Prorated from a
larger figure.
$1,944,735
81
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Jacksonville prototype scrubber, Teller Environmental Systems, Inc., is
reproduced in Appendix A.
Direct comparison of these three cost estimates is difficult, be-
cause equipment costs have been grouped in different ways. Examination of
the bottom line costs (Table 14) shows considerable variation, however.
It is beyond the scope of this task to specify which, if any, of these
estimates is "correct."
TABLE 14. COMPARISON OF SCRUBBER COST ESTIMATES
Complete Cost
Estimate One Cell Retrofit
Jacksonville NARF $1,944,735
Naval Air Systems Command 1,515,000
Teller Environmental Systems, Inc. 705,650
Although some inconsistencies may be noted between the two Navy
estimates, the main difference between their analyses and the TESI
estimate reflects a difference in the quality of construction specified,
particularly for supporting and ancillary structures. The Navy estimates
are based on construction of reinforced concrete stack modifications and
concrete structures to house the water pumping and water treatment equip-
ment. The TESI estimate is based on provision of minimum construction
consistent, in their view, with satisfactory equipment performance and
reliability. A more detailed cost breakdown and analysis will appear in
the Final Report to Phase II of this study.
An estimate for annual maintenance and operating costs has been
made by Naval Air Systems Command (Reference 15). Based on two engine
82
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tests per day, 250 days per year, annual maintenance was estimated at
$50,000 and annual operating costs for the scrubber and cleanup system
were roughly estimated at $80,000 (operating costs will vary with type of
engine and length of tests). The electrical power cost, which is the
major nonlabor operating cost, is $18,400 per year, based on 300 hp pump
capacity, two tests per day, 250 days per year, and $0.035 per kw-hr (the
cost of power at Jacksonville NAS). This assumes maximum water flow at
all times. In fact, maximum water flow is used only at afterburner engine
settings, which constitute a very small fraction of test hours. Also, as
noted previously, there is reason to believe that the water flowrates
originally specified for the system can be reduced with no loss of perfor-
mance. These considerations indicate that actual power costs will be less
than $18,000 per year.
6.3 FUEL ATOMIZATION
The fuel atomization improvement concept for reducing jet engine
emissions involves attempts to introduce fuel into the engine in a more
highly atomized state than is presently the case. The premise is that
this finer atomization would bring about more efficient combustion and,
hence, reduced emissions. This concept has been experimentally evaluated
in two distinct forms -- methane absorption and water or alcohol emulsion.
Both programs have been sponsored by the Naval Air Engineering Center,
Trenton, New Jersey.
6.3.1 Methane Absorption
A series of experiments has been conducted in which methane gas is
dissolved in the fuel at high pressure. When the fuel stream is exposed
to the low pressure and elevated temperature existing just downstream from
the fuel nozzles, the methane is expected to flash out of solution and,
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hence, aid in the atomization process. In fact, it was observed that the
methane gas tended to slowly bubble out of solution when the pressure was
reduced, rather than violently disrupting the liquid as had been antici-
pated. In a series of tests using a single burner, methane concentration
was varied between 0 and 2 percent by weight in JP5 or Jet A fuels. Pol-
lutant emissions monitored were NO, NO UHC, CO, C0?, and smoke num-
/\ £
ber. No significant change in any of these emissions was observed when
methane gas was added to the fuel.
6.3.2 Emulsions
In this concept, an emulsion of an immiscible liquid with the reg-
ular fuel is created. The liquid in the discontinuous phase (water or
ethanol in the experiments conducted to date) is in the form of small
globules which flash after the fuel stream leaves the nozzles. This
vaporization of the volatile globules disrupts the fuel stream, leading to
finer atomization and more complete combustion.
A series of combustion tests using a single burner indicated that
the presence of water or alcohol droplets in the fuel stream can signifi-
cantly affect the pollutant emission (Reference 3). A standard milk
homogenizer was used to prepare emulsions of water or ethanol of 0 to 10
percent by volume in JP5. Table 15 shows a representative sample of the
results obtained. It should be noted that the energy value of the fuel is
reduced proportionately to the water concentration.
These results were reasonably repeatable in similar tests. The
results show that opacity and particulate concentration were significantly
reduced, NOX was slightly reduced, CO was nearly unaffected, and unburned
hydrocarbon significantly increased. The data in Table 15 raise several
84
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TABLE 15. EFFECT OF WATER/FUEL EMULSION ON COMBUSTION
Fuel
JP5
JP5
Water
Cone.
0%
10%
NOX
Ppm
66.5
54.5
UHC
ppm
2.5
5.3
CO
%
0.038
0.039
Smoke
No.
33.6
23.8
Particulate.
Conc., gm/m
5.55
3.11
questions. The reduction in smoke number and particulate with the water
emulsion are consistent with the proposed mechanism of better atomization
and combustion, but the increase in unburned hydrocarbon is difficult to
understand. It is also not clear whether the reduction in NO is due to
A
the finer atomization, or simply due to the lower combustion temperature
of a 10-percent water in JP5 fuel mixture compared to straight JP5.
There are two main problems inherent in the implementation of a
fuel emulsion system for test cell use, even if further testing confirms
the lower smoke numbers and pa£tjj:uj!ie-jnassJ4>^^ the spe-
cific gravity pf-a-iO^pefcent water in JP5 emulsion is sufficiently
ferejj^from straight JP5 that modification to the engine fuel control
/system may be required for some engines. Second, the engine thrust and
other performance parameters are different for an emulsion than for JP5.
Since the emulsion would be used only for test cell operation, careful
calibration would be required so that an engine's performance in a cell
\sing an emulsion could meaningfully be compared to that same engine^:
operation in the field on JP5.
Despite these problems, the emulsion concept is considered suffi-
ciently promising that further investigation, probably involving full-
scale engine tests, are now being planned.
85
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6.4 THERMAL CONVERTER
The thermal converter, sometimes called an afterburner (not to be
confused with the afterburner stage of a jet engine), raises the tempera-
ture of the exhaust stream with a secondary burner stage. The exhaust
stream is maintained at an elevated temperature for the length of time
needed to oxidize combustible components of the exhaust CO, hydro-
carbons, and carbonaceous particulate to C02 and H^O.
6.4.1 Thermal Converter Configuration for Test Cells
A thermal converter used in an engine test cell and installed in an
in-line arrangement takes the general form illustrated in Figure 19. The
high-velocity exhaust jet from the engine and the induced secondary air
from the test cell both enter the cylindrical section called the mixer.
In this section the two streams mix together to achieve as uniform a
velocity profile as possible. The flow leaving the mixer is then diffused
to the full cross-sectional area through a simple conical diffuser. This
reduces the average velocity of the stream to an acceptable level. In the
burner, the required amount of fuel is added and ignited, and the result-
ing flame is stabilized. Basically, the burner consists of a row of fuel
spray bars followed by a row of vee-gutter flameholders.
The converter is located immediately downstream from the burner.
It consists of a cylindrical section long enough to complete combustion of
the added fuel and oxidation of the pollutants. The region identified as
the combustion zone in Figure 19 represents the length required to com-
plete combustion and attain a uniform temperature distribution. In the
reaction zone, the temperature is maintained at a selected level for the
length of time needed to achieve the required degree of pollutant
conversion.
86
-------
00
Movable Sleeve
Outer Liner
Tailpipe Induced Cooling^
Induced Secondary Air
Combustion
Zone
Reaction
Zone
Burner
Converter
Cooler
Water Spray
Bars
Back-Pressure
Control Device
(Exducer)
Stationary
' Plug
Figure 19. Schematic diagram of basic thermal converter configuration
(Reference 6).
-------
The flow from the converter then passes through a water spray sys-
tem which consists of a row of pipes that inject water into the stream.
In the cooler, the evaporated water reduces the gas temperature enough to
protect the exhaust stack. Before entering the exhaust stack, the flow
passes through a variable-area device located at the exit of the cooler.
This consists of a stationary plug and a movable sleeve which can be used
to adjust the exit flow area. This device serves two functions. Its
primary function is to control the backpressure on the thermal converter.
This makes it possible to adjust the amount of secondary induced air enter-
ing the converter to the desired level for any given engine. The back-
pressure control device also acts as an ejector. It induces cool ambient
air to flow through the annulus between the outer liner and the thermal
converter shell. This air provides the necessary convective cooling of
the shell during operation.
As described in Reference 7, the operation of a thermal converter
installed in a test cell would be virtually automatic. In starting a test
sequence, the engine is first mounted on the test stand. The converter's
adjustable-length mixer section is then locked into place as a predeter-
mined distance from the engine's tailpipe. The backpressure control
device is also locked into a predetermined setting. Both adjustments
would be determined empirically and would be standard for a given engine
model. For an engine being tested in the afterburning mode, the tempera-
ture of the exhaust is high enough to achieve oxidation of the pollutants
without supplying additional fuel in the thermal converter, provided the
amount of induced air is maintained at a low value. The burner system is
designed so that upon command of the operator it can be retracted for
protection just prior to ignition of the afterburner and replaced at the
88
-------
conclusion of the afterburning sequence. In all other cases, the thermal
converter would be operated automatically. Its control system would ini-
tiate and adjust the flow of fuel to the burner and water to the spray
system to maintain the required performance.
6.4.2 Pollutant Conversion Performance
The emissions of gaseous pollutants and particulate from the ther-
mal converter have not been adequately determined. However, sufficient
testing has been done to show that the thermal converter is quite effec-
tive in reducing smoke number (that is, solid particulate is largely
eliminated). It was also found that NOX emission is not unduly in-
creased. Specifically, data presented in Reference 6 show that a reduc-
tion in smoke number by a factor of 10 is readily achieved. While no
measurement of particulate mass loading was made, the reduction in smoke
number probably implies a substantial reduction in particulate emission.
NO emission from the thermal converter was measured at about 1 lb/1000
Ib. fuel burned. This is small compared to the NO output of most jet
A
engines. The emissions of CO and UHC from the thermal converter were not
adequately measured. But it seems unlikely that the converter would
markedly increase the emission of these pollutants over emissions of the
jet engine itself, and it may actually lower the concentration of CO and
UHC.
Based on the information presented in References 6 and 7, the
thermal converter would be effective in greatly reducing the opacity of
the exhaust plume, would probably significantly lower particulate emis-
sions, and would not greatly increase emission of gaseous pollutants.
89
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6.4.3 Costs
Table 16 (Reference 6) shows the capital and operating costs for a
thermal converter retrofit to a standard type A test cell. The capital
cost is relatively low compared to other emission control methods con-
sidered. However, the operating costs are very high, due primarily to the
high fuel consumption of the thermal converter burners. As a rough rule of
thumb, it requires as much fuel to operate the thermal converter as it does
to operate the engine being tested. It should also be noted that the costs
in Table 16 are based on a fuel cost of $0.35/gal. It seems likely that
this figure considerably underestimates fuel cost during the next 5 to 10
years. The availability of the additional fuel that would be required if
thermal converters were in wide use is also a matter of concern.
6.5 FUEL ADDITIVES
Organometallic fuel additives used to modify the character of emis-
sions from combustion processes have been studied for many years. Many
additives, containing such metals as barium, manganese, iron, calcium, and
various rare earths, are sold in the United States by a number of manufac-
turers. The primary market for these additives is conventional fixed power
generation equipment, although there is a growing market in turbine-powered
processes.
The emission modification produced by additives is apparently due to
the catalytic activity of the metallic component, although the exact mechan-
isms have not been determined. Reductions in emissions of SCL (40 to 50
^"*" ___^ ~ -
percent reduction with No. 5 fuel oil ),"^T~~(2Q to 30 percent reduction
x ^
with pulverized coal), and parti culate^^percent reduction with ^pulver-
ized coal) have recently been reported for stationary power plants (Refer-
ence 1). An additional benefit from using fuel additives is reduction
90
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TABLE 16. THERMAL CONVERTER COST ESTIMATE (Reference 6)
Capital Costs
Total Equipment a $305,000
Assembly and Installation 88,000
Management 84,000
General Contractor Profit 14,000
Total Installed Cost $491,000
Daily Operating Costsb
J52 J57 TF30
Fuel $2010 (5740 gal) $2760 (7890 gal) $4960 (14,100 gal)
Water 23 (188,000 gal) 25 (214,000 gal) 35 (289,000 gal)
Power 11 (500 kW-hr) 12 (520 kW-hr) 16 (610 kW-hr)
Purge Nitrogen 6 (270 scf) 8 (320 scf) 4 (160 scf)
Total Cost $2050 $2805 $5015
Includes material, fabrication, labor, pumps, and controls.
Based on two 120-minute test cycles per day for each of the specified
engines.
in plume opacity. This reduction is probably due mainly to a change in the
particle size distribution, rather than to a reduction in particulate mass
emissions.
The first time fuel additives were used to modify turbine aircraft
engine emissions occurred in Southeast Asia during the 1960's. Some of the
dirtier jet engines were at a disadvantage in combat situations because
their trajectory could be followed easily. A manganese-containg additive,
91
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CI-2 (Ethyl Corporation), was quite successful in reducing the opacity of
the exhaust plume. For awhile, this additive was used extensively in com-
bat operations. But several serious problems with CI-2 led to curtailment
of its use. CI-2 is toxic in bulk form and is easily absorbed through the
skin. Also the prolonged use of CI-2 damaged engines by causing a buildup
of deposits on turbine blades and other engine parts. These deposits lead
to hot spots and engine burnouts.
In a number of programs, the Naval Air Propulsion Test Center
(NAPTC) has investigated usage of organometallic fuel additives to modify
jet engine emissions. In one program, different additives were compared to
determine their ability to reduce plume opacity. One engine (a J57-P8) was
used for all of the tests. The test procedure was to gradually change the
concentration of the additive being evaluated, while a Ringelmann reader
observed the opacity of the test cell plume. The engine was operated at a
power level known to give the maximum plume density. Since the Navy used
proprietary compounds and information in conducting the tests, the complete
ranking of the effectiveness of the various additive compounds was not
released. The most effective compound (lowest percent metal in fuel to
produce a Ringelmann No. 1 reading) was CI-2. Next in effectiveness, and
only slightly belpw CI-2, was Fe55 (Araphahoe Chemical Company), usually
referred to a^fFrroceneT^ Table 17 shows the additives evaluated and their
manufacturers.
Because ferrocene is effective in reducing plume opacity, and be-
cause it is low in toxicity, a program to evaluate ferrocene in various
engines has been under way for some time at the Naval Air Rework Facility
at Alameda Naval Air Station. A final report on this work is now in the
final stages of preparation at NAPTC. It is scheduled for completion in
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TABLE 17. METALLIC FUEL ADDITIVES EVALUATED BY THE
NAVAL AIR PROPULSION TEST CENTER3
Trade Name Manufacturer
Smokeless #9 Ellis Chemical, Inc.
DGT-2 Apollo Chemical Co.
E/C 200 G&M International
Technol D Oil Technology Corp.
Technol T Oil Technology Corp.
Technol TT Oil Technology Corp.
Fe55 Arapahoe Chemical Co.
RS 211242 Arapahoe Chemical Co.
RS 20521 Arapahoe Chemical Co.
PD 1471 Arapahoe Chemical Co.
PD 1472 Arapahoe Chemical Co.
CI-2 Ethyl Corp.
PSP MC955 Petroleum Specialty Products Co.
PSP MC900 Petroleum Specialty Products Co.
Cerium United Technology Research Center
Rare Earths Mixture United Technology Research Center
aNot necessarily in order of effectiveness.
93
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June 1976. Some of the findings of the report are presented here, along
with results from a recently presented paper (Reference 2).
, " It has been es^atTf^heTthaTmost Navy~engTnTs are~not-a^.etsely
Effected by the use of ferrocene additives, as long as the ferrocene con>
ckntration is kept at reasonable levels (0.1 percent) and additive use is
conf>ne4^to testing opej:atmo5_njiL_e^medlnj_2.._to 4JIQUES...-Table 18 shows
a list of the engines that have been tested with ferrocene additive. For
each of the listed engine and model types, it has been found that ferrocene
additive at an appropriate concentration can reduce the test cell plume
density to Ringelmann No. 1 or below. It was also found that ferrocene use
during testing is not injurious to engine performance or life; further
testing is required to determine the effects of continued or long term
use. Currently, approved test durations with ferrocene range from 0.75
hour for the TF41 engine to 2 hours for the 052.
TABLE 18. ENGINES SUITABLE FOR USE WITH FERROCENE ADDITIVES
Engine Model Type
J79
J52
J57
TF30
TF41
T56
T56
aSuitability for
consideration.
GE8a
P6
P10
P6
A2
A10
A16
use with
Smokeless Combustion
Model Type
GE10-C
P408, P8B
P8, P408, P412
ferrocene additive is under
94
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Table 19 shows, for various engines, the observed stack opacity
without additive at the "dirtiest" engine power setting. The table also
shows the ferrocene concentration required to reduce the plume opacity to
20 percent (Ringelmann No. 1) at the same power setting. These tests were
conducted at the Alameda Naval Air Station test cells. Repeating the same
tests at another cell or with a different engine of the same type might
give somewhat different results. Also, the differences betweeen the find-
ings of Reference 2 and Reference 38 indicate that these test results are
not very reproducible. The tests do indicate, however, that adding small
concentrations of ferrocene to the fuel can significantly reduce plume
opacity for the engines tested.
TABLE 19. EFFECT OF FUEL ADDITIVE ON STACK OPACITY
Engine
J57-P10
J52-6
TF41-A2
T56-A16
TF30-P6
J79-GE8
T56-A10
Maximum Smoke Opacity
(without additive)
40%
55%
40%
30%
35%
50%
35%
% Ferrocene for
Ref. 2
0.05%
0.10%
0.02%
0.02%
0.04%
0.04%
0.03%
20% Opacity
Ref. 38
0.05%
0.06%
0.02%
0.02%
0.06%
0.10%
0.03%
The toxicity of the additive CI-2 has been a major reason why the
Navy has stopped using it. Concern has also been expressed about dis-
persion of manganese (the metallic component of CI-2) by the test cell ex-
haust gases. The toxicity of ferrocene, the additive the Navy feels is
95
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most suited to replace CI-2, has been evaluated recently. The NAPTC re-
ceived a report of tests conducted at the U.S. Navy Toxicology Unit of the
National Naval Medical Center. Tests completed include:
Ocular and dermal irritation with
~ Ferrocene (dicyclopentadienyl iron)
-- Five percent ferrocene in JP-5
Twenty percent ferrocene in toluene
Inhalation studies with
-- Ferrocene dust
-- JP-5 with ferrocene
-- Toluene with ferrocene
-- Xylene with ferrocene
Acute oral toxicity of ferrocene (l-D)
Acute peritoneal toxicity of ferrocene
The results of the study are summarized by the following quotation
(Reference 39):*
"Ferrocene alone and in solution causes very little if any ocular
irritation. Irritation studies on both abraded and unabraded skin
were negative. Rat ID for ferrocene is 1890 mg/kg (oral) and
1520 mg/kg (intraperitoneal ). Studies with ferrocene dust showed
no significant toxic symptoms during and following exposures of up
to 150 mg/m . Acute exposures to ferrocene and the solvents
showed no increase in toxicity over the solvents alone."
*The ferrocene tested in this study was Arapahoe Fe 55R which is a
specially purified form of ferrocene. The intraperitoneal rat ID
data presented here are somewhat higher than reported by other
laboratories with other sources of ferrocene.
96
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The health effects of emissions from test cells in which CI-2 or ferrocene
is being used have not been determined. _
The effect of ferrocene additive on gaseous and particulate emi
si on has been studied in the Alameda NAS tests. For gaseous emissions
/ (CO, S0x> C02, NOX> UHC), the additive produced no changes in pgj
t i on . Howev«*v-£^-i-wj-3^d4^^^ reduction in
particulate emissions when ferrocene was used. Figure 20 shows particle
mass loading as a function of engine power setting, with and without the
additive. In Figure 20, NR refers to Normal Rating power level, and MR
means Military Rating power level. These data were collected at one sam-
pling location at the exit plane of the test cell stack. EPA Method 5
sampling was used.
One problem related to continuous (inflight) use of ferrocene is
the reduced thermal stability with ferrocene-treated fuel. A high temper-
ature (400-500°F) thermal stress test indicated that ferrocene an
oxidation catalyst ~ causes significant increases in carbon and sludge
deposition. A similar, though less severe, problem occurred with the
manganese additive. As a result of an extensive experimental program at
Wright Patterson AFB, the Air Force now believes that manganese based
additives with minor amounts of a barium compound to promote stability
offers the best compromise between effectiveness and reducing opacity,
freedom from operational problems, and safety. Air Force personnel
believe that this additive is also capable of reducing test cell plumes
from most engines in their inventory to 20 percent opacity or lower.
6.5.1 Civilian Airline Additive Use
Although this study was primarily concerned with military test
cells and test cell pollution abatement programs, a brief investigation of
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IO
CO
-------
commercial airline practices was conducted. Letters were also sent to the
executives responsible for the maintenance operations of the major air-
lines. These letters requested information about any methods or devices
used to control test cell emissions. Requests were also made for any
information specifically related to their use of fuel additives. Replies
were received in most cases. The responses are shown in Table 20. In
general, additives are used by those airlines with a significant inventory
of older dirtier, OT3, JT4, and JT8 engines. Several airlines stated that
the additives would be phased out in the near future as they switched over
completely to smokless combustor engines.
6.6 OTHER ABATEMENT METHODS
During the approximately 8 years that test cell emission abatement
has been seriously pursued, numerous techniques and devices have been pro-
posed. The five methods previously discussed -- nucleation scrubbing,
fuel additives, thermal converter, fuel atomization, and electrostatic
precipitation -- are the ones the Navy has considered promising enough to
warrant experimental investigation. Many other methods have been con-
sidered and ruled out because of some clearcut technical or economic
problem. The characteristics, costs, and application to test cells of
many of these methods are summarized in References 10, 17, 19, and 20.
Table 21 (Reference 10) shows the relative characteristics of a
number of abatement methods. Table 22 (Reference 17) is more quantita-
tive. It includes estimates of capital and operating costs as of mid-
1973. The control equipment in Table 22 is sized to baseline gas flow of
1,200,000 acfm. This is a much higher airflow than is commonly encoun-
tered in cells. For example, the workhorse J79 engine produces stack gas
flow of about 500,000 acfm at military power setting and 700,000 acfm in
99
-------
TABLE 20. FUEL ADDITIVE USE BY COMMERCIAL AIRLINES
o
o
Airline
United
National
Bran iff
Western
American
TWA
North Central
Pan American
Allegheny
Delta
Continental
TWA does overhauls
The concentration
for a given engine
Additive used
Apollo DGT-2
See below3
CI-2
CI-2
NONE
CI-2
NONE
CI-2
NONE
NONE
CI-2
data included in
of additive is that
type.
Engines with which Amount of Approximate % Engine
additives are used Additive used tests using additive
JT4, JT8, JT30, JT3, JT4 Technician's
discretion
All JT3D and some JT8D - -
JT3D 15 drops/ 50%
1000 gal fuel
- - -
JT4, JT3D 0.05-0.1% 15%
by volume
- - -
JT3D, JT4, JT8D Technician's 44;i
discretion^
- - -
- - -
JT3D, JT8D 1 gal/ -
1000 gal fuel
TWA figure.
which past experience has shown to give adequate plume opacity control,
-------
TABLE 21. SUMMARY OF PARTICULATE ABATEMENT SYSTEMS (Reference 10)
^ E
85 '<
PARTICULATE
ABATEMENT METHOD
H . High
M Modsrat*
L " LOT
A- Bat Applicable
Dry Cyclone L
Fabric Filter H
Acoustical Filters L
Magnetic Filters H
Vet Scrubbers
Spray L
Venturi H
Plate H
Baffle L
Impingement H
Moving Bed H
Filter Bed N
Packed Bed H
Centrifugal H
Electrostatic
Dry H
Vet H
L H L
H L H
ILL
MIL
L
H
L
L
L
M
L
H
H
NA
L
H
H
H NA
L NA
H NA
L MA
HA
M
H L
M L
M H
M H
NODE H H L
UHC( liquid) H M H
NONE H H H
NONE H H H
CO, UIIC
CO, UHC
CO, UHC
co. imc
CO, UHC
CO, UUC
CO. UHC
CO, UHC
CO, UHC
HONE
CO, UHC
H H
L N
Would not neet visibility or case enisslon goals
Potential high AP if clogged, Potential fire hazard with
UHC - only noderate visibility emission abatement
Vould not meet visibility or mass emission goals
Very early development stage - requires massive auxiliaries
used only as secondary system
All comments predicated on exhanst preconditioning
Would not meet visibility goal
Will not handle test cell flow variations - high AP could r»atilr» auxlllmrr fan
Vould not meet visibility goal
Vould not meet visibility goal
AP could require auxiliary fan
Does not easily handle test cell flov variations
Vould not meet visibility goal
Mow In use on prototype Installation
Potential for fcest cell use - minlnixed vatar losses
Vould not meet visibility goals - high lost
Preconditioning enhances performance - potential for test eell. nac
Incineration
Conventional
Innovative
Infrared
M H M H L NA M L CO. UHC L H
H H H H H NA M M CO, UHC L H
H HMHKNAM H UHC (liquid) M H
Livlted particulate removal - high cost
Development required - moderate potential for test cell use - ctmld salt
Requires large development effort - costs could be high - effectiveness
on visible emissions questionable
-------
TABLE 22. COMPARATIVE DATA - ALTERNATE GAS CLEANING SYSTEMS (Reference 17)
DIRECT FLAME AFTERBURNER
FLOATING BED SCRUBBER
VARIABLE THROAT VENTURI
fMPINGEMENT PLATE SCRUBBER
REBOUND ENTRAPMENT SCRUBBER
JET SCRUBBER
NUCLEATION/PACKEO BED
SCRUBBER
IRRIGATED PRECIPITATOR
DRY SINGLE STAGE PRECIPITATOR
INTERMITTENTLY WASHED TWO -
STAGE PRECIPITATOB
BAGHOUSE
VISCOUS FILTER
POLLUTANTS
ABATED
SMOKE, SOL. & Lia PART.
CO, GASEOUS C,Hy
SMOKE. SOLID PART.
SOME NO2& LIO- PART.
SMOKE, SOLID PART.
SOME N02& LIQ. PART.
SMOKE. SOLID PART.
SOME NO2 & LIO. PART.
SMOKE. SOLID PART.
SOME N02 & LIO. PART.
SMOKE. SOLID PART.
SOME NOj & Lia PART.
SMOKE, SOL ID PART.
SOME N02& Lia PART.
SMOKE. SOL. & Lia PART.
SOMEN02
SMOKE. SOL. PART.
SOME Lia PART.
SMOKE, SOL. & Lia
PART.
SMOKE, SOL. PART
SOME Lia PART.
NONE
DESIGN PARAMETERS
MAX. GAS
FLOWHI
(ACFMI
3.320.000
1,200.000
1,200.000
1.200,000
1.200.000
1,200,000
1,200.000
1.200.000
1.460.000
1,200.000
1,460,000
1.200,000
MAX. GAS
TEMPERATURE
°F
1500
167
167
167
167
167
167
167
400
167
400
167
MAX. GAS
VELOCITY
IFPMI
1500
BOO/
800
400/ 121
500
400/
500
600/
650
400/ «l
500
600
1200/
1400
300/
350
300/
350
3-6
500
GAS FLOW
AREA
IFT2)
900/
1000
1500/
2400
2400/ 121
3000
2400/
3000
1B50/
2000
2400/ «)
3000
2000
B50/
1000
4200/
4850
3400/
4000
244.000/
485,000
2400
MAX. GAS
PRESS, DROP
(INHjOl
0
1012
4070
6-10
2-3
PROVIDES
HEAD
2-3
5-S
0.5-1
05-1
3-5
0.3-0.5
WATER
REQUIREMENTS
PRETREATMENT
SPRAY
(GPMI
2000131
200013)
2000(31
2000(3)
2000131
2000(31
2800(4)
2800(4)
2000(3)
2800«l
2000(3)
2800(41
GAS
CLEANING
IGPM)
_
60,000
8.400
4,800
11.000
7.200
14,000
4,200
60
_
_
POWER
REQUIREMENTS
WATER
PUMPING
IKWI
_
3450
700
510
1950
3710
1100
574
250
350
250
350
OTHER
(KW)
_
_
-
-
-
300
250
1900
120
100
100
TOTAL
(KW/1000CFM)
2.90
0585
0.425
1.63
3.10
1.16
0.685
1.79
0.35
a 29
a 375
COSTS
CAPITAL
COSTS
10* t
1.0 - 1.5
1.2- 1.5
1.2- 1.5
10- 1.2
1.2- 1.5
1.2- 1.5
0.9- 1.2
2.5 -3.0
1.5-20
0.9 1.2
2.5 - 3.0
0,2-0.3
ANNUAL
OPERATING
COSTS'*)
103 $
1300/
1500
80.'
90
im
25
IS.'
20
45/
55
90'
100
25'
35
20'
25
20'
30
to/
IS
91
13
IS/
20
o
no
11) LEAVING EQUIPMENT
(2) LIQUID/GAS SEPARATION COMPONENT
(31 BASED ON 400°F ENTERING EQUIPMENT
14) BASED ON 167°F (SAT.) ENTERING EQUIPMENT
(5) BASED ON 500 TESTS/YR OF 350 LB/SEC ENGINE:
EXCLUDES MAINTENANCE AND SOLID&LIOUID SEPARATION
-------
afterburner mode, including augmentation airflow. The J79 is one of the
larger engines tested in military test cells. The cost figures in Table
22 should be used cautiously as they are only rough approximations based
on an "average" test cell.
Discussed below are some of the test cell cleanup methods
considered, but not experimentally evaluated, by the Navy.
6.6.1 Cyclone Separators
Cyclones are inertia! particle collection devices in which carrier
gas containing particles is spun rapidly within a closed cylindrical
shell. Centrifugal force moves the particles to the wall of the cyclone.
From there they move to lower velocity regions of the device and are col-
lected. Cleaned gas exits at the center of the cyclone cylinder. Cyclone
dust collectors are commonly used because of their low capital cost, abil-
ity to run hot, and good collection efficiency for particles with dia-
meters greater than about 5 microns. It is easy to design cyclones that
can efficiently collect particles in the submicron range (such as those
found in test cells); however, this cannot be done without incurring an
increased pressure drop. For effective collection of 0.5 microns, for
example, simple calculations show that for reasonably sized cyclones,
pressure drops on the order of 100 to 300 inches of water would be re-
quired. This is far in excess of the 10 to 20 inches of water allowed for
a test cell cleanup device.
6.6.2 Fabric Filters
Fabric filters are commonly used to separate solid particles from
liquid or gaseous media. These filters are capable of collecting par-
ticles much smaller than the space between the filter fibers. This is due
to the fact that most of the filtration is accomplished by the coating of
103
-------
material already collected, rather than by the fibers themselves. If
glass cloth fabrics are used, fabric filters can operate at temperatures
approaching 600°F. Fabric filters are simple, effective, and well
developed for numerous applications. However, there are several charac-
teristics of test cells that make these filters of doubtful value as
cleanup devices.
Fabric filters are low velocity devices. When fiberglass cloth is
used, superficial velocities of about 2.0 acfm/ft2 should not be
exceeded (Reference 37). This means that for a J79 engine with sufficient
augmentation air to drop the gas stream temperature to 550°F, about
400,000 feet2of filter area would be required. With water spray cool-
j
ing (which introduces other problems), a filter area of about 250,000
9
ft would still be required. Considering the various constraints on bag
arrangement, bag cleaning devices, and dust hopper arrangement, a baghouse
to handle this flow would have dimensions of about 110 ft. x 110 ft. x
40 ft. high (Reference 10). This is comparable to the size of the test
cell. Finding space for such an installation would be impossible in most
cases. The installed cost of such a baghouse would be about $2.50/acfm,
or $1 to $1.5 million. Finally, maintenance costs due to bag tearing and
blinding have been estimated at twice that of wet scrubbers or ESP'.s.
Fabric filters pose other problems, also. They create a fire hazard
because of the large area coated with carbonaceous particles. Also,
filters do not work well in conjunction with exhaust water spray cooling
because the water can blind the fabric. Considering all of these factors,
fabric filtration does not seem to be a promising approach to test cell
cleanup.
104
-------
6.6.3 Venturi Scrubbers
Venturi scrubbers are particulate collection devices in which the
gas to be cleaned is accelerated to a high velocity, then sprayed with
water droplets. The high relative velocity between water droplets and
particles in the gas causes impaction between the particles and the water
drops. The dirty water drops are collected in a demisting section down-
stream from the venturi scrubber. Collection of the particulate is en-
hanced if condensation is induced by saturating the gas in the reduced
pressure region at the venturi throat. Water vapor condensation on the
particles causes particle growth and increased probability of collection.
Venturi scrubbers are very effective for collecting particles with
diameters greater than about 1 to 2 microns. But to collect smaller parti-
cles, large gas pressure drops are required. To effectively collect par-
ticles of 0.5 micron requires a water pressure drop from 40 to 80 inches.
These pressure drops increase operating cost and tend to make venturi
scrubbers less competitive with packed scrubbers.
6.6.4 Coanda Noise Suppressor
The Coanda system (References 4 and 5) is designed to control
noise, but if affects pollution control systems in several ways. The
Coanda can best be understood by studying Figure 21. Figure 21(a) shows a
freestream jet exhaust. The hot gases are confined to a cone with its
apex at the exhaust nozzle. Because of the high temperature in the gas
stream, the noise is refracted away from the exhaust. This is the reason
a jet engine sounds much louder 45° off-axis than directly behind the
engine.
Figure 21(b) shows the principle of the Coanda system. When a
curved plate is placed directly above the engine exhaust outlet, the hot
105
-------
Noise
a. Unconfined jet exhaust
Hot gases
Sound-
absorptive
material
I/ ///////////// /Tl.A
b. Coanda gas-noise separator
Figure 21. Principle of Coanda device.
106
-------
gases of the exhaust stream cling to the plate (the Coanda effect). The
noise is refracted away from the gas stream and is absorbed in sound-
absorptive material. The sound-absorptive material is not exposed to
thehot gas stream, as is the case in conventional test cells. This is the
primary advantage of the Coanda system. The hot gas stream and the noise
are separated, and each can be handled separately and, hopefully, more
effectively than when both must be controlled simultaneously.
One obvious advantage to separating the gas flow and noise is that
the test cell does not require water spray cooling of the exhaust. In
conventional cells, this water cooling is needed to protect the sound
suppression equipment. Elimination of water cooling of the exhaust may
significantly reduce the opacity of the test cell plume. As a further
advantage, dry operation allows a much wider choice of sound absorptive
material.
A full-scale Coanda cell is now being tested. A final report on
these tests is scheduled to be issued sometime in March 1976. In addition,
there is a current project at the U.S. Naval Academy to consider the ef-
fects on test cell operation of pollution control devices that could be
installed on a Coanda-equipped test cell stack.
6.6.5 Hush House
The hush house is simply a room large enough to contain an entire
aircraft. There is a long, wide-mouthed exhaust tunnel with a deflector
baffle at the end which directs the exhaust vertically. Figure 22 shows
the hush house at Miramar Naval Air Station. The hush house was designed
to suppress noise when testing engines in aircraft. There is, however, an
unexpected additional result. Opacity readings from the hush house stack
are lower than readings from the same engine tested in a conventional test
107
-------
o
CO
//
\
\
r
-91
J
rfi
i
4.
Deflector baffle
19'«-)
Mpch room
Control rooni
Figure 22. Hush house at Miramar Naval Air Station.
Cross-section
-------
cell. In fact, the opacity readings from all engines tested in the hush
house are less than 20 percent, except for the J79 engine in the F4, which
has an opacity of about 20 percent.
The lower plume opacity from the hush house is apparently due to
exhaust stream dilution brought about by the large quantity of air en-
trained. The wide-open exhaust tunnel entrance (no augmenter is used),
combined with the great length of the tunnel, produces a diluted, well
mixed plume with a relatively low opacity.
6.7 SUMMARY OF CLEANUP TECHNOLOGY
Several exploratory studies of possible test cell cleanup methods
have been made. Based on these studies, the Navy, which has been given
responsibility for military test cell cleanup device development, has
sponsored experimental work in five areas. These areas are:
Electrostatic precipitators
Nucleation scrubbers
Thermal converters
Fuel atomization improvement
Fuel additives
A sixth method, clean combustion engine modifications, will be discussed
in Phase II of this study.
Of the above five methods, only two -- nucleation scrubbers and
fuel additives are reasonably well developed. Fuel additives reduce
test cell plume opacity, and may reduce particulate loadings somewhat.
Use of fuel additives is easily and inexpensively implemented. They do
not seem to cause serious engine performance degradation when employed
within recommended time and concentration limits. The extended use of
some fuel additives (e.g., CI-2) is known to be detrimental to engine
109
-------
life. The point at which the extended use of ferrocene will cause detri-
mental engine changes is not known. Both the Navy and the Air Force are
now studying this question. A nucleation scrubber is the only test cell
cleanup device that has been experimentally evaluated on a full-scale test
cell. Incomplete emissions sampling indicates that particulate and
condensible hydrocarbons are substantially removed.
The electrostatic precipitator, fuel atomization improvement, and
thermal converter concepts have been tested experimentally only in small
scale models. All seem to be capable of reducing test cell emissions.
Their drawbacks are high operating cost (thermal converter), operating
problems (ESP), and limited pollutant reduction (fuel atomization). Each
of these three methods would require further development before it could
be considered ready for full scale demonstration.
Several concepts not experimentally evaluated by the Navy
cyclones, fabric filters, venturi scrubbers are briefly considered. It
is concluded that none of these methods seems worthy of experimental
study. Two recent noise control concepts are discussed because their
implementation would impact the other cleanup technologies. These are the
hush house and Coanda nose control systems.
Cost data for each of the five experimentally-evaluated test cell
cleanup methods is presented. For the nucleation scrubber, the most
developed method, three different cost estimates were obtained. These
estimates differ by a factor of nearly 3 to 1.
Foreign test cell cleanup technology was not investigated directly.
No such cleanup technology was discovered in the literature or in the
discussions with the people listed in Appendix B.
110
-------
REFERENCES
1. Kikin, I. and R. Bennett, "Chemical Reduction of S03, Particulates,
and NOx Emissions," presented at The International Energy
Engineering Congress, Chicago, November 4-5, 1975.
2. Klarman, A. F. and J. E. Horling, "Participate Sampling from Gas
Turbine Engines," Paper 27-5, presented at the Third International
Conference on Environmental Sensing and Assessment, Las Vegas,
Nevada, September 14-19, 1975.
3. Moses, C. A., "Reduction of Exhaust Smoke from Gas Turbine Engines
by Using Fuel Emulsions," Interim Report AFLRL No. 68, July 1975.
4. Naval Air Engineering Center Report No. NAEC-GSED-80, Final
Technical Report, "Initial Model Studies/Coanda Refraction Noise
Suppression Concept Exploratory Development," May 1974.
5. Naval Air Engineering Center Report No. NAEC-GSED-81, "Final
Technical Report, "Scale Model Studies/Coanda Refration Noise
Suppression Concept -- Exploratory Development," May 1974.
6. Demetri, E. P., "Model Testing of a Thermal Converter for the
Control of Exhaust Emissions from Navy Jet Engine Test Cells,"
Northern Research and Engineering Corporation Report No. 1219-1 for
Naval Air Engineering Center, July 11, 1975.
7- Northern Research and Engineering Corporation, "Preliminary Design
of a Thermal Converter for the Control of Exhaust Emissions from
Navy Jet Engine Test Cells," Report No. 1188-1, 1973.
8. White, H. J., "Industrial Electrostatic Precipitation,"
Addison-Wesley, REading, Pennsylvania, 1963, p. 359.
9. United Engineers and Constructors, Inc., "Test and Evaluation of a
Pilot Two-Stage Precipitator for Jet Engine Test Cell Exhaust Gas
Cleaning," Final Draft Report, September 1975.
Robson, F. L., et al., "Analysis of Jet Engine Test Cell Pollution
Abatement Methods," AFWL-TR-73-18, May 1973. Available from NTIS
as AD-763119.
11. Teller, A., "Turbine Emission Control A Systems Approach,"
Teller Environmental Systems, Inc., Worchester, Massachusetts.
12. Teller Environmental Systems, Inc., "Jet Engine Test Cell TESI
Augmenter-Scrubber System," Contract No. N62467-70-C-0240, December
1971.
13. Kemen, R. J., et al., "Jet Engine Test Cell Pollution Abatement
Efficiency Tests," Naval Air Rework Facility, Jacksonville,
Florida, March 1973 - May 1974
111
-------
14. Krimmel, J. A. and B. A. Longley-Cook, "The Effect of a Model
Scrubber on Gaseous EMissions from a Gas Turbine Engine Test Cell,
Report No. AESO 113-74-1, August 1973.
15. Morhard, W.D., "Joint Navy-Air Force Jet Engine Test Cell Study,
Phase II Draft Report." Final report scheduled for issuance in
July 1976.
16. Bailey, D. L. and P. W. Tower, "Production Test Facilities for
Turbojet and Turbofan Engines 1975 to 1995," Naval Postgraduate
School Report No. NPS-57Ba-FO-72061A.
17. Ferner, J. A., et al., "A Study of Means for Abatement of Air
Pollution Caused by Operation of Jet Engine Test Facilities," Naval
Facilities Engineering Command No. 5685-000, August 1973.
r^
( 18J Morhard, W. C., Naval Air Systems Command. Private Communication.
19. Kelly, C. M., "Air Pollution Abatement for Jet Engine Test
Systems," Naval Air Engineering Center Report No. NAEC-GSED-64.
20. C. F. Braun and Co., "Turbojet Aircraft Engine Test Cell Pollution
Abatement Study," Naval Facilities Engineering Command Report No.
CR74.001.
21. Lindenhofen, H. E., "State-of-the-Art Review of Gas Turbine Engine
Exhaust Smoke Monitors," Naval Air Propulsion Test Center Report
No. NAPTC-AED-1956, August 1971.
'\22. j Lindenhofen, H. E., "A Survey of the Air Pollution Potential of Jet
^_^' Engine Test Facilities," Naval Air Propulsion Test Center Report
No. NAPTC-PE-3, October 1972.
23. Champagne, D. L., "Standard Measurement of Aircraft Gas Turbine
Engine Exhaust Smoke," ASME Paper No. 71-GT-88.
24. SAE Aerospace Recommended Practice 1179, "Aircraft Gas Turbine
Engine Exhaust Smoke Measurement," Society of Automotive Engineers,
New York, N.Y., May 4, 1970.
25. Klarman, A., "Gas Turbine Engine Particulate Measurement Technique
Summary of Coordinating Research Council Program," Interim
Report, Naval Air Propulsion Test Center, November 6, 1974.
26. Bogdan, L., et al., "Analysis of Aircraft Exhaust Emission
Measurements," Cornell Aeronautical Laboratory, October 15,
1971. Available from NTIS as PB204.879.
27. "Aircraft Engine Emissions Catalog," Report No. AESO 101 --
Revision 3, June 1974.
112
-------
28. Environmental Protection Agency, "Compilation of Air Pollutant
Emission Factors," 2nd Edition, USEPA, Research Triangle Park,
N.C., April 1973.
29. Poth, E. W. and E. R. Lozano, "Air Pollution Emissions from Jet
Engines," USAF Regional Environmental Health Laboratory, Kelly AFB,
Texas, February 1967.
U.S. Bureau of Mines, "A Field Survey of Emissions from Aircraft
Turbine Engines," USBM Report No. R17634, May 1972.
Slusher, G. R., "Sulfur Oxide Measurement in Aircraft Turbine
Engine Exhaust," National Aviation Facilities Experimental Center
Report No. FAA-NA-75-10, September 1975.
32. Faitani, J. J., "Smoke Reduction in Jet Engines through Burner
Design," SAE Paper 680348, 1968.
33. DeCroso, S. M., et al., "Smokeless Combustion in Oil Burning Gas
Turbines," ASME Paper 67-PWR-5, 1967.
34. Lieberman, A., "Composition of the Exhaust from a Regenerative
Turbine System," JAPCA 18, pp. 149-153, 1968.
35. Stockman and Betz, "Study of Visible Exhaust Smoke from Aircraft
Engines," SAE Paper 710429, May 1971.
36. Grems, B. C., "Plume Opacity and Particulate Emissions from a Jet
Engine Test Cell," M.S. Thesis, University of California, Davis,
1975.
37. Spaite, P. W., et al., "High Temperature Fabric Filtration of
Industrial Gases," JAPCA, May 1961.
38. Klarman, A., Naval Air Propulsion Test Center. Private
communication, January 17, 1976.
113
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APPENDIX A
SCRUBBER RETROFIT COST ESTIMATE
The following detailed cost estimate is reproduced as received from
Teller Environmental Systems, Inc.
115
-------
ESTIMATED COST FOR A TELLER ENVIRONMENTAL SYSTEMS, INC.
EMISSION CONTROL SYSTEM
FOR
A STANDARD JET ENGINE TEST CELL
(J 79 ENGINE)
14 January 1976
by Charles B. Wyman
Denis R. J. Roy
116
-------
I. INTRODUCTION
The size of the Nucleation scrubber system is predicated on
testing the J-79 jet engine in its maximum afterburner mode
(17,500 Ibs. thrust). Also, the use of a TESI designed aug-
menter is assumed in order to reduce the amount of dilution
air required.
Basis for the estimate is the prototype installation now
operational at the Black Point test cell number one (1) NARF-
JACKSONVILLE, FLORIDA. The estimate reflects refinements in
material selection as well as improvements in design developed
from operation of the prototype unit.
The cost per cell was established using the following
assumptions:
1. A common cooling tower is to be used for two test cells.
2. The Cooling Tower is located between the two test cells
(Est. 200 ft. between cells).
3. One solids treatment system would be required for two
test cells.
4. Structural design - no snow loads incorporated.
The flow sheet attached is representative of typical flow
conditions for gas and liquid streams.
117
-------
fTI
0
0
o
I
o
0
2
o
M
(/> fff o
r
I
2
E
n
z
<
§
Z
PI
z
>
r
(A
(fl
fl
01
Z
0
-------
I.I. SYSTEM DESCRIPTION
The Nucleation system to be employed for emission control
would consist of five major components:
1. TESI Augmenter
2. Quench System (Existing)
3. Nucleation Scrubber System
4. Recycle Cooling System
5. Solids Treatment System
The TESI Augmenter (proprietary) has approximately the
same physical size as the conventional augmenters (6 feet
diameter x 12 feet overall lenght). It has a similarity
in the converging inlet section and quench spray ring.
The main differences are quench design, the diverging
section, and the recycle gas system. Material of construc-
tion would be carbon steel with the quench ring of stainless
steel.
The quench systems employed with the present augmenters
could be adapted to the new TESI augmenter at minimal cost.
The Nucleation Scrubber (proprietary) design is essentially
the same as the prototype design, that is the scrubber
consists of two identical sections mounted with independent
supports parallel to sides of the exhaust stack. Typical
overall scrubber dimensions can be approximately 22 feet
119
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II. SYSTEM DESCRIPTION (CONT'D)
,>
long x 27 ft high x 28'-6" wide including discharge
louvers. Although dimensions can be modified to adopt
to orientations. Typical packed sections have a face
dimension of 20 ft wide x 24 ft high and each would con-
tain a 4 ft depth of 2 inch nominal polypropylene
Tellerettes followed by a divider support plate and a
one ft depth of 1 inch nominal polypropylene Tellerettes,
Each side would be made of three 6'-8" wide modules
constructed of FRP material. The 2 inch packing is to
be irrigated from above by two spray headers with poly-
propylene nozzles and from the inlet side with face sprays.
Above the center of the exhaust stack outlet would be lo-
cated turning vanes to distribute the gas flow to the
packed beds. These vanes would be carbon steel with a
high grade epoxy coating.
The gas are discharged to the atmosphere at an angle of
45° upward via gull wings (stationary louvers) constructed
of FRP and mounted on the scrubber section. The sides
and top of the unit would be enclosed with a heavy duty
corrugated FRP sheathing.
The liquid effluent is collected in clopped bottom troughs
containing baffles to prevent gas bypass. The collected
120
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II. SYSTEM DESCRIPTION (CONT'D)
liquid is discharged by gravity to the cooling tower
sump. These troughs would be constructed of carbon
steel with epoxy coating inside and outside.
All structural steel would be of ASTM A-36 specifica-
tions and would be prepared for and coated with an
epoxy paint system.
All piping is carbon steel schedule 40 and includes
recycle water lines between the scrubber system and
the cooling tower. Two pumps with drives capable of
delivering each 5500 GPM at 110' TDK would be installed.
Carbon steel wetted parts would be employed.
Instrumentation would provide for local indication of
liquid flow, pressures, temperature and level as well
as alarm circuits.
The recycle cooling system is comprised of a tower
capable of handling the peak thermal load of two test
cells, with the J-79 engines in afterburner mode.
A standard cooling tower approximately 90 ft x 60 ft
constructed of wood or plastic with a concrete sump
would be required. Thermal load on the unit would be
of the order of 840 M BTU/hr for both cells. The re-
mainder of the cooling system would be comprised of
121
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II. SYSTEM DESCRIPTION (CONT'D)
level, temperature and pressure indicators, miscellaneous
piping and structural steel for access ladders and plat-
forms.
The solids treatment system would consist of a 500 gallon
mix tank (FRP) with agitator, a lime feeder (40 #/hr
normal), a 5000 gallon (FRP) settling tank and a rotary
vacuum filter (400 ft filter surface, wetted parts 304 s.s)
Connecting piping and pumps would be mild steel construc-
tion. Instruments would include a flow control loop and
a level control loop. Structural supports for feeder
would be to ASTM A-36 specifications and would be prepared
for and coated with an epoxy paint system.
122
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ENGINEERING SERVICES PROVIDED BY TEST
Process Flow Diagrams
Piping and Instrument Diagram
General Arrangement Drawings
Equipment List and Specifications for Purchased Equipment
Fabrication Drawings for Manufactured Process Equipment
Isometric Piping Drawing in
Plan and Elevation Piping Drawings Including Supports § Hangers
All Foundation and Concrete Design
All Structural Steel Design Including Pipe Supports and Hangers,
Platforms etc.
All Painting
All Electrical Work (including one line and elementary diagrams,
specifications, etc.) Required For Installation, Including
Local and National Codes etc.
All Instrumentation and Electrical Location Plans.
Lighting
Noise Silencing Provisions that may be Required in the system with
such equipment as a vacuum pump
All Erection Specifications
All Erection Supervision and Inspection
Purchasing of All Equipment and Materials
Operating and Maintenance Manuals
Recommended Spare Parts Lists
Preparation and up-dating monthly of a schedule for the job
showing key milestones, activities and action dates.
Total Responsibility For All Erection and Construction
123
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ENGINEERING SERVICES PROVIDED BY TESI (CONT'D)
Total Responsibility For Receiving, Unloading, Inspecting, and
Storing All Equipment and Materials Delivered to Job Site.
Turnkey - Engineering
Cost For Two Test Cells, One Cooling Tower, One Solids
Treatment System, and TESI Augmenter $225,000
All Engineering Listed Above Including (but does not
include direct construction labor cost or equipment cost)
Supervision of Erection $ Purchasing
Performance Guarantee
<10I Opacity
<0.004 gr/scf
All services and equipment to bring system into per-
formance guarantee.
Equipment Guarantee
Equipment guaranteed for one (1) year from date of start-up
Life expectancy of the unit 15-25 years.
124
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SUMMARY OF COSTS
SECTION TOTAL COST
TESI Augmenters $ 36,600
Nucleation Systems 526 200
Cooling System 336,000
Solids Treatment System 179,500
Sub-Total $1,078,300
Contingency 10% 108,000
Engineering & Royalty 225,000
TOTAL COST FOR INSTALLED SYSTEMS ON
TWO JET ENGINE TEST CELLS $1,411,300
EQUIVALENT COST PER TEST CELL $ 705,650
125
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BREAKDOWN OF COSTS FOR ONE TEST CELL
Nucleation Scrubber
TESI Augmenter
Cooling Tower
Solids Treatment System
Piping
Pumps
Instruments
Electrical
Miscellaneous
101 Contingency
Engineer ing
(Prop-Rated from Cost
of two cells)
$ 167,600
17,800
125,000
50,600
70,500
10,000
19,900
52,500
24,750
538,650
54,500
593 ,150
112,500
$ 705,650
126
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ESTIMATED COST OF TEST EMISSION CONTROL SYSTEM FOR A STANDARD JET ENGINE TEST CELL
ITEM
MATERIAL
COST
LABOR
COST
FREIGHT
COST
(J-79 Engine)
TOTAL
Nucleator System For One Test Cell
Nucleation Scrubber - Modular construction
6 - 6'-8" modules x 27' high
Packing - 2" Tellerettes-Polypropylene
4032 ft
1" Tellerettes-Polypropylene
1056 ft
Spray Nozzles - Polypropylene
Est. 100 nozzles
_, Scrubber Side Walls $ Top Covers
2000 ft2 FRP
Stationary Louvers - FRP
21' long x 6' wide Approx. 700 ft
Structural Supports - incl.
Framework for module
Turning Vanes
Sump Steel
Pipe Supports
Support Legs
Side Plate Reinforcing M0,000#
All steel primed § epoxy coated
Piping § Valves - incl.
Manifolds for nozzles
Piping to and from cooling tower
Strainers. Carbon Steel Sch. 40
25,000
56,000
27,000
2,500
20,000
16,000
800
2,000
2,000
28,300
22,000
10,000
2,000
17,000
2,200
1,000
400
50
3,500
600
1,200
400
50
500
400
24,200
10,800
2,100
21,000
3,200
78,000
45,000
-------
ESTIMATED COST OF TESI EMISSION CONTROL SYSTEM FOR A STANDARD JET ENGINE TEST CELL
ITEM
MATERIAL
COST
LABOR
COST
FREIGHT
COST
(J-79 Engine)
TOTAL
Instrumentation - incl.
Pressure Gauges
Orifice Meter
Temperature Indicators
Level Indicator
Pumps - includes
5500 GPM at 110' TDH pumps w/drive
Carbon Steel Wetted Parts
200 HP
Electrical - incl.
Starter for one - 200 H.P. motor
Wiring $ conduit
Painting - incl.
Instruments - incl.
Pressure Gauges
Temperature Indicators
Level Indicators
Alarms
3,600
6,000
13,500
4,000
500
10,000
5,000
5,500
400
500
500
500
8,000
7,000
24,000
Touch-up and finish
TOTAL NUCLEATOR SYSTEM
Cooling System For Two Test Cells
Cooling Tower to handle 840M BTU/hr
approx. 90' x 60'
Misc. Structural Steel for ladder,
platforms and supports
1,400
185,700
190,000
17,000
10,000
68,550
20,000
12,000
100
8,850
10,000
1,000
11,500
263,100
220,000
30,000
11,000
-------
ESTIMATED COST OF TESI EMISSION CONTROL SYSTEM FOR A STANDARD JET ENGINE TEST CELL
ITEM
MATERIAL
COST
LABOR
COST
FREIGHT
COST
"(J-79 Engine
TOTAL
ro
Piping and Valves - incl.
Strainers
Electrical - incl.
Starters for tower fans
Wiring and conduit
Painting - incl.
Touch-up and finish
Site-Prep for Tower
TOTAL COOLING SYSTEM
Solids Treatment System For Two Test Cells
Lime Feeder - 304 SS
40#/hr normal capacity
Mix Tank - 500 gallon (FRP)
Settling Tank - 5000 gallon (FRP)
Agitator for mix tank - 304 SS
impeller and shaft
Rotary Vacuum Filter - 3,04 SS
Wetted Parts 400 ft surface incl.
vacuum receiver and vacuum pump
Pumps -
1 - 160 GPM @ 50' TDH
2 - 80 GPM @ 50' TDH
Mild Steel wetted parts
11,500
24,000
900
75,000
1,000
2,500
8,000
14,000
100
3,000
500
1,000
500
2,000
100
2,000
500
500
20,000
40,000
450
1,500
249,450
2,800
500
4,800
5,000
8,000
72,500
500
50
500
50
-
14,050
200
50
200
5,500
9,500
336,000
3,500
600
5,500
1,100
80,000
2,000
4,000
-------
ESTIMATED COST OF TEST EMISSION CONTROL SYSTEM FOR A STANDARD JET ENGINE TEST CELL
ITEM
MATERIAL
COST
LABOR
COST
FREIGHT
COST
(J-79 Engine)
TOTAL
Piping § Valves - incl.
All inter connecting piping between
filter tower, and tanks.
Carbon Steel
Instruments - incl.
Pressure gauges
2 - Flow control loop
Level control loop
Alarms
Structural Steel - incl.
Access platform for tanks
Support for feeder
Electrical - incl.
Starters for agitator - pumps
o Wiring § conduit
Painting - incl. touch-up and finish
Site Prep - incl. foundation for tanks
and filter
TOTAL SOLIDS TREATMENT SYSTEM
00
15,000
15,000
1,000
31,000
6,000
6,000
9,000
450
1,000
124,950
6,000
4,000
7,000
5,000
5,000
47,650
800
500
1,000
50
-
6,900
12,800
10,500
17,000
5,500
6,000
179,500
TESI Augmenter For One Test Cell
Augmenter tube consisting of a converging
and diverging section with integral Quench
Ring.
6' diameter x 12' long
Shell Carbon Steel
Quench Ring Stainless Steel
16,000
1,000
800
17,800
Note: Electrical costs do not include sub-station costs if required.
-------
APPENDIX B
INFORMATION SOURCES
The following is a list of persons contacted during the course of this
study who provided significant useful information. Their assistance is
gratefully acknowledged.
Mr. Dominic Croce
Naval Air Engineering Center
Lakehurst, New Jersey 08733
(Coanda device, hush-house)
Major Peter S. Daly
Air Force Civil Engineering Center
Tyndall Air Force Base
Florida 32401
(Emissions)
Mr. Richard J. Keman
Code 610
Naval Air Rework Facility
Jacksonville Naval Air Station
Jacksonville, Florida 32212
(Nucleation scrubber, electrostatic
precipitator)
Mr. Anthony Klarman
Code PE-71: AFK
Naval Air Propulsion Test Center
Trenton, New Jersey 08628
(Fuel additives)
Dr. Barbara Longley-Cook
Naval Air Rework Facility
North Island Naval Air Station
San Diego, California 92135
(Emissions)
Mr. Larry Mihalic
Naval Air Rework Facility
North Island Naval Air Station
San Diego, California 92135
(Emissions)
Mr. Don Munson
United Engineers and Constructors
100 Summer Street
Boston, Massachusetts 02110
(Electrostatic precipitator)
Mrs. Sarah H. O'Brien
Naval Air Rework Facility
Jacksonville Naval Air Station
Jacksonville, Florida 32212
(Nucleation scrubber, electrostatic
precipitator)
Lt. Alfred Roth
Wright-Patterson Air Force Base
Dayton, Ohio 45433
(Fuel additives)
Mr. R. J. Salazar
Naval Air Rework Facility
Alameda Naval Air Station
Alameda, California 94501
(Emissions, test cell operation)
Dr. Wayne Sule
Naval Air Engineering Center
Lakehurst, New Jersey 08733
(Thermal converter, fuel
atomizat ion)
Dr. Aaron J. Teller
Teller Environmental Systems, Inc.
10 Faraday Street
Worchester, Massachusetts 01605
(Nucleation scrubber)
Mr. Ed Thomas
Air Transport Association
1709 New York Avenue, N.W.
Washington, D.C. 20006
(Test cell operations)
Mr. James A. Tomich
Bay Area Air Pollution Control
District
939 Ellis Street
San Francisco, California 94109
(Emissions)
131
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Capt. Dennis F. Naugle Mr. W. W. Wilcox
Air Force Civil Engineering Center United Airlines Maintenance Base
Tyndall Air Force Base South San Francisco
Florida 32401 California 94104
(Emissions) (Fuel additives)
132
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 340/1-78-001 a
2.
3. RECIPIENT'S ACCESSIOWNO.
4. TITLE AND SUBTITLE
JET ENGINE TEST CELLS
MEASURES: PHASE 1
5. REPORT DATE
- EMISSIONS AND CONTROL
January 1978
6. PERFORMING ORGANIZATION CODE
EPAOE; Project 7203
7. AUTHOR(S)
D. E. Blake
8. PERFORMING ORGANIZATION REPORT NO.
ACUREX FINAL REPORT 76-218
1978 Revision
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Acurex Corporation/Aerotherm Division
485 Clyde Avenue
Mountain View, California 94042
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-3158, Task 4
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Division of Stationary Source Enforcement
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final - 8-13-76 - 9-30-76
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Stationary Source Enforcement Series
16. ABSTRACT
This report discusses the current state of the art of pollutant emission measure-
ment and cleanup technology related to military jet engine test cells. Considerable
emissions data from jet engines is available, but data from test cell stacks is
sparse. Gaseous emission data for the major pollutant species (CO, NO, N02, S02*
SOa) are reliable; particulate, opacity, and unburned hydrocarbon data are less so.
The five types of test cell cleanup methods that have been experimentally evalu-
ated -electrostatic precipitator, nucleation scrubber, fuel additives, thermal con-
verter, and fuel atomization improvement -are described in detail. Other, less
promising methods are briefly discussed. Several methods are quite effective in re-
ducing test cell emissions. Fuel additives are effective in reducing test cell plum
opacity. Capital and operating cost data on these methods are presented. For the
nucleation scrubber, the best-developed cleanup technology, three cost estimates
from different sources are given.
ume
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATl Field/Group
t Jet engines
Emission exhaust gases
Jet engine test cells
Enforcement
Jet engine test cells
Air facilities
13B
14D
01E
3. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
133
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