NASA CR-121094FR-5295

FINAL REPORT

EFFECT OF FUEL ZONING AND FUELNOZZLE DESIGN ON POLLUTION

EMISSIONS AT GROUND IDLE CONDITIONS FOR ADOUBLE-ANNULAR RAM-INDUCTION COMBUSTOR

ByT. R. Clements

PRATT & WHITNEY AIRCRAFTFLORIDA RESEARCH AND DEVELOPMENT CENTER

Prepared For

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

NASA Lewis Research Center

Contract NAS3-11159 t% 7--\

Reproduced by -vc )NATIONAL TECHNICAL - . ,INFORMATION SERVICE ,s,-

US Department of CommerceSpringfield, VA. 22151

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1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

NASA CR- 1210944. Title and Subtitle 5. Report Date

Effect of Fuel Zoning and Fuel Nozzle Design on Pollution Emissions February 1973at Ground Idle Conditions for a Double-Annular Ram-InductionCombustor 6. Performing Organization CodeCombustor

7. Author(s) 8. Performing Organization Report No.To R. Clements FR-5295Approved: J. H. Shadowen

10. Work Unit No.9. Performing Organization Name and Address

Pratt & Whitney AircraftDivision of United Aircraft Corporation 11. Contract or Grant No.Florida Research and Development Center NAS3-11159West Palm Beach, Florida 33402

13. Type of Report and Period Covered12. Sponsoring Agency Name and Address

National Aeronautics and Space AdministrationWashington, D. C. 20546 14. Sponsoring Agency Code

15. Supplementary Notes

Project Manager, P. J. Perkins, Air Breathing Engine Procurement Section,NASA Lewis Research Center, Cleveland, Ohio

16. Abstract

An exhaust emission survey was conducted on a double-annular ram-induction combustor at simulatedground idle conditions. The combustor was designed for a large augmented turbofan engine capable ofsustained flight speeds up to Mach 3.0. The emission levels of total hydrocarbon (THC), carbon monoxide(CO), carbon dioxide (CO 2 ) and nitric oxide (NO) were measured. The effects of fuel zoning, fuel nozzledesign, and operating conditions (inlet temperature and reference Mach number) on the level of theseemissions were determined. At an overall combustor fuel/air ratio of 0. 007, fuel zoning reduced THCemissions by a factor of 5 to 1. The reduction in THC emissions is attributed to the increase in localfuel/air ratio provided by the fuel zoning. An alternative method of increasing fuel/air ratio would be tooperate with larger-than-normal compressor overboard bleed; however, analysis on this method indicatedan increase in idle fuel consumption of 20%. The use of air-atomizing nozzles reduced the THC emissionsby 2 to 1.

17. Key Words (Suggested by Author(s)) 18. Distribution StatementCombustor, Ram-Induction, Short-Length,Double-Annular, Exhaust Emissions, Ground Idle, Unclassified - UnlimitedReduction

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price*

Unclassified Unclassified 56 $3. 00

* For sale by the National Technical Information Service, Springfield, Virginia 22151

This docu.. ment printed on recycled paper

NASA-C-168 (Rev. 6-71)

Preceding page blankFOREWORD

This report was prepared by the Pratt & Whitney Aircraft Division ofUnited Aircraft Corporation under Contract NAS3-11159.

The contract was administered by the Air-Breathing Engine ProcurementSection of the National Aeronautics and Space Administration, Lewis ResearchCenter, Cleveland, Ohio.

The period of performance for the contract was June 1968 throughAugust 1972. This report summarizes the technical effort performed duringthe period September 1971 through August 1972. The earlier phases of thecontract are discussed in references 1 and 2.

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Preceding page blankTABLE OF CONTENTS

Page

SUMMARY . ................ ..... 1

INTRODUCTION ...... ..... ........................ 2

SCOPE OF THE INVESTIGATION ......................... 2

Fuel Zoning ................................... 2Fuel Nozzles ................................... 3Measured Parameters ............................ 7Test Conditions ................................. 7

COMBUSTOR DESIGN ........... . .................. 7

Combustor ............................ .... 7Diffuser ...................................... 8

CALCULATIONS ..................................... 12

Reference Mach Number ........................... 12Combustion Efficiency ............................ 12Total Pressure Loss . ..................... 13Outlet Temperature Pattern Factor (TPF) ............... 13Outlet Radial Temperature Profile ............ ......... 13Exhaust Specie Emission Index .. ....... 14Fuel/Air Ratio Calculated From Exhaust Emission

Measurements ...................... ..... ... 14

RESULTS AND DISCUSSIONS ................. ........... 17

Fuel Zoning ................................... 17

THC Emissions ............................. 17CO Emissions .......... ...................... 19

Fuel Nozzles .................................. 20Inlet Temperature and Reference Mach Number . ........... 25Nitric Oxide Emissions ................... . ....... 25Compressor Bleed. .. ........................... 25Sampling Technique .................... ........ .. 27

SUMMARY OF RESULTS ........ ..................... 31

APPENDIX A - EQUIVALENT CONICAL ANGLE ............... 33

Definition ........................... .......... 33Application .................................... 33

'd',P..%ECT}IN G P;h, E DL'A'. N 7S, :..'.L m I

TABLE OF CONTENTS (Continued)

Page

APPENDIX B - TEST FACILITY AND TEST RIGDESCRIPTION .......................... 35

Test Facility ............. . ... 35Test Rig Description ........................... 35Flow Straightener ............................ . 35Venturi .................................. . 36Preheater ................................... 36Plenum Chamber .................... ... 36Instrumentation Section ........................... 36Diffuser-Combustor Case ...... ............ 36Traverse Case ...... . ....................... 36Exhaust Duct ........................... ... 36Exhaust Valve ...... .................. 36

APPENDIX C - INSTRUMENTATION ........... 37

Basic Performance Instrumentation . ......... .... 37Airflow ..................... 37Fuel Flow ............................ 37Test Section Inlet ........................... 39Combustor Outlet ............ .... . .. .. . .... . 39Gas Sample Instrumentation ........................ 40Fixed Exhaust Duct Gas Sampling Rake .......... 40Traversing Gas Sampling Rake ................... ... 42Sample Transfer Line .......... ........ ......... 42Sample Analyzing Instrumentation ................... 42

46REFERENCES ......................................

SUMMARY

An exhaust emission survey has been conducted on a double-annular ram-induction combustor operating at simulated ground idle conditions. The combustorwas designed for a large augmented turbofan engine capable of sustained flightspeeds up to Mach 3. 0. The emission levels of total hydrocarbon (THC), carbonmonoxide (CO), carbon dioxide (CO 2 ) and nitric oxide (NO) were determined.

Testing was conducted in a full-scale, 90-deg (1. 57 radian) sector rig. Thetest conditions were set at a combustor inlet pressure of two atmospheres and atinlet temperatures and reference Mach numbers from 200°F (366°K) to 350°F(450°K) and 0.06 to 0. 08, respectively. Emission data were obtained both witha stationary, 5-point sample rake located in the test rig exhaust duct well down-stream of the combustor outlet, and with a circumferentially traversing, 5-pointsample rake located in the combustor outlet. The traversing data taken in thecombustor outlet, when averaged, compared closely with the stationary rakedata taken in the exhaust duct where the combustion products were well mixed.However, large circumferential variations in emission levels were observedwith the traversing rake in the combustor outlet. Thus, a small number ofstationary probes at this location could give highly erroneous results.

Previously reported development efforts on this combustor have resulted ina configuration with good performance at the sea level takeoff and cruise designpoints (references 1, 2 and 3). The effort reported herein investigated variousmethods of reducing the emissions of the objectionable pollutants, THC and CO, atthe ground idle condition by: (1) fuel zoning, whereby a portion of the combustorfuel nozzles are shut down, and all of the fuel passed through the remaining noz-zles, and (2) fuel nozzle design. Three nozzle designs were tested: (1) a conven-tional pressure atomizing nozzle, (2) an air blast nozzle in which the fuel wasatomized by a stream of high velocity air; the airflow driving potential beingnormal combustor pressure drop and (3) an air assist nozzle which also atomizedthe fuel with high velocity air, but with the air supplied by an external source.The effect of combustor inlet temperature and reference Mach number on the ex-haust emissions was also investigated.

Fuel zoning proved to be very effective in reducing the emission levels ofthe objectionable pollutants. At an overall combustor fuel/air ratio of 0. 007,fuel zoning reduced THC emissions by a factor of 5 to 1. The reduction in THCemissions is attributed to the increase in local fuel/air ratio provided by thefuel zoning. An alternative method of increasing fuel/air ratio would be tooperate with larger-than-normal compressor overboard bleed; however, analysison this method indicated an increase in idle fuel consumption of 20%.

The use of air-atomizing nozzles reduced the THC emissions by 2 to 1.The effect of combustor reference Mach number was dependent on the test con-ditions and the type of fuel zoning employed. In general, decreasing referenceMach number reduced THC and CO emissions. Increasing combustor inlettemperature reduced THC and CO emissions.

The NO emission index was small, being less than 2. 0 lbm/1000 Ibm fuel(g/kg) at all test conditions and fuel injection modes.

1

INTRODUCTION

With the growing public concern over the quality of the air it breathes,Government agencies and private industry have begun to take action to reducethe emission of dangerous or objectionable materials into the atmosphere. Al-though the contribution of aircraft to the total pollution problem is small inrelation to other sources (reference 4), the atmospheric pollution in and aroundair terminals is largely the result of aircraft operations (reference 5). Duringground idle and taxi operations the primary objectionable exhaust emissionsfrom gas turbine engines are carbor monoxide and unburned hydrocarbons(reference 6). These products are the result of poor combustion efficiency atthe idle condition. The poor idle efficiency of current engines is due to lowcombustor inlet temperatures, low fuel/air ratios, inadequate fuel atomizationand inadequate mixing of the fuel and air.

One method of increasing combustion efficiency during idle is to increasethe local fuel/air ratio in those regions where combustion is taking place. Thiscan be accomplished by: (1) controlling the combustor airflow by some suitablemeans so as to alter the primary zone airflow to maintain a high primary zonefuel/air ratio, or (2) bleeding overboard large quantities of compressor dis-charge air at idle to raise the combustor fuel/air ratio, or (3) by zoning the fuelflow to obtain a locally high fuel/air ratio. The first course of action requiresa variable area combustor, which is a major and complicated addition to anyengine. The second method, while easy to design into a new engine, requiresa major modification (new diffuser cases, etc. ) if it is to be retrofitted on anexisting engine. This method also requires an increase in idle fuel flow to main-tain a constant idle thrust. The third method requires only a relatively minoraddition to the fuel control system. For this reason, fuel zoning was selected forstudy since it offers a quick, practical method of reducing the THC and CO emis-sion levels during idle and taxi operation on both new and existing engines.

In addition to fuel zoning, the method by which fuel is injected into thecombustor can influence the emissions of THC and CO. Data reported in theliterature (references 7 and 8) show that these emissions can be reduced by usingair atomizing nozzles. Since a change in fuel nozzles represents a relativelyminor engine modification, two types of air atomizing nozzles were investigated.

The test program was conducted at the Pratt & Whitney Aircraft FloridaResearch and Development Center in a full-scale rig that was a quarter sectionof a full annulus.

SCOPE OF THE INVESTIGATION

The emission levels of unburned hydrocarbons, carbon monoxide, carbondioxide and nitric oxide were determined in a double-annular combustor operatingat simulated idle conditions. The effects of fuel zoning, fuel nozzle design, andoperating conditions on these emissions were determined.

Fuel Zoning

Two methods of fuel zoning were investigated in addition to the normal mode(all nozzles flowing). They were:

1. Radial zoning, all of the fuel was injected into the inner com-bustion zone of the double-annular combustor.

2

2. Circumferential zoning, all of the fuel was injected throughevery other nozzle in both the inner and outer combustionzones. The outer zone nozzles were staggered relative tothe inner zone nozzles. See figure 1.

Fuel Nozzles

Three types of fuel nozzles were studied. They were:

1. A conventional pressure atomizing nozzle as shown in figure 2.This nozzle was used with the axial flow swirler shown in thefigure. The flow curve for this nozzle is shown in figure 3.

2. An air blast type air atomizing nozzle as shown in figure 4.This type nozzle atomizes the fuel with a stream of highvelocity air. The airflow driving potential is simply com-bustor pressure drop. The fuel flow curve is shown infigure 3.

3. An air assist type air atomizing nozzle as shown in figure 5.This type nozzle also atomizes the fuel with a stream ofhigh velocity air, however, the nozzle airflow is providedby an external source. The fuel flow curve is shown infigure 3.

* Flowing Nozzles

0 Nonflowing NozzlesView Looking Upstream

Figure 1. Staggered Circumferential Fuel Zoning FD 63821

3

Gasket (Nicke

0.1875 in.

(0.476-cm) dia

0.015 in. d j a

(0.038-cm) 0.3745

(0.951-cm) dia

0.250 in. max

(0.635-cm)

90-deg (1.575 rad) Spray Angle

(0.629-cm)

Swirler (£

r- A i r f low

Figure 2. Simplex Fuel Nozzle and Axial Flow Swirler

FD 63822

L 4

h Air Blast Nozzles

: Simplex Nozzles

— Air-Assist Nozzles

Flowrates Given are the Sums of Eight Nozzles

2 3 4 5 NOZZLE PRESSURE DROP - psi (Hundred)

NOZZLE PRESSURE DROP - N/m2 (Thousand)

Figure 3 . Nozzle Fuel Flow Curves DF 92624

Fuel and Air

Swirler Air

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Figure 4. Air Blast Nozzle FD 63824

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Measured Parameters

The test rig was instrumented to measure the following:

1. Combustor airflow

2. Combustor fuel flow

3. Inlet total and static pressure

4. Inlet total temperature

5. Outlet total temperature

6. Outlet total pressure (outlet static pressure was calculated)

7. Exhaust emission species CO 2 , CO, THC and NO at twolocations in the test rig. One location was in the exhaust ductat a distance of 13 L/D's downstream of the combustor outletand the other was at the combustor outlet.

Test Conditions

The test conditions used in the program were designed to cover the rangeof ground idle conditions observed on many turbojet/turbofan engines in use orunder development. All of the testing was conducted at an inlet total pressureof 2 atmospheres. The remaining test parameters were:

1. Inlet total temperature - 200 ° to 350°F (367 ° to 450°K)

2. Reference Mach number - 0. 06 to 0. 08

3. Fuel/Air Ratio - 0. 007 to 0. 014

COMBUSTOR DESIGN

C ombustor

The combustor used in this program was a double-annular ram-inductioncombustor. This term was coined from the general design details of the com-bustor as well as the fundamental process by which air is admitted into thecombustion zone. The combustor was constructed with two annular combustionzones arranged concentrically around each other. This arrangement increasesthe effective length to height ratio of the combustor thus allowing considerablereductions in combustion length to be realized. Each combustion annulus had itsown separate fuel supply. In contrast with more conventional systems in whichair is made to flow into the combustion zone by a static pressure difference acrossthe combustor walls, the air in this combustor is forced into the combustor by theram pressure of the inlet flow. The air entry ports are constructed as vanedturning elbows or scoops to aid in efficiently turning the air into the combustor.Figure 6 is a cross section of a typical double-annular ram-induction combustor.A more complete description of the ram-induction concept is presented in ref-erence 9.

7

The test combustor (figure 7) had an effective flow area of approximately256 in 2 , (0. 165m 2 ). The area distribution is shown in figure 8. The combustorhad 256 scoops in a full annular design with 32 scoops in the primary and 32 inthe secondary for each liner air entry. The scoop pattern was fully staggeredas shown in figure 9 with the pattern repeating for each nozzle spacing. Theprimary scoops on the inner liner of the ID annulus and on the outer liner of theOD annulus were fitted with shroud capture hoods (figure 10) to aid in turningthe air into the primary zone.

Diffuser

The diffuser used with this combustor (figure 11) is defined as a 7 deg(0. 122 rad) equivalent conical angle (ECA, Appendix A for definition) snout-typediffuser. As shown in figure 11, the combustor inner and outer liners wereextended into the diffuser thus providing three flow paths. The bulk of the dif-fusion occurred in the region from the diffuser inlet to the snout inlet. Diffusionwas at a rate of 7 deg (0. 122 rad) giving an area ratio of 1. 245. Some additionaldiffusion was provided in the snout center passage to reduce dump losses. Thesnout inner and outer walls were contoured so that there. was no diffusion in theinner and outer passages.

Scoops

Firewalls

-Scoops

Vanes

Figure 6. Ram Induction Concept in a Double-Annular Combustor

FD 36572B

8

Primary Zone Film Cooling Slot Thumb Nail

Cooling Lou

Fuel Nozzle Ports (Nozzles Removed)

Figure 7. Test Combustor (View of Annular Segment, Looking Upstream)

FE 100226C

Figure 8. Flow Area Distribution of Test FD 31997A Combustor (Percent)

5 deg 37 min 30 sec (0.098 rad) O Primary Scoops

Q Secondary Scoops

( ) Fuel Nozzle Locations

Figure 9. Staggered Scoop Pat tern FD 36587

OD Primary Scoop Capture Hood

Outer Shroud

Ai r f low to Primary Scoop

Air f low to Secondary Scoops

Liner

Firewall

Fuel Nozzle Port (Nozzle Removed)

Figure 10. Capture Hoods (View of Annular Segment, Looking Downstream)

FE 100223C

10

Fuel Supply Tubes

Alnlet = 184.32 in.2 (0.1189 m2 )AExit = 228.3 in.2 (0.1473 m2 )

(Location Denoted /-- Outerby -.- . O .') Shroud

Outer LinerDiffuserStrut

Center Liner

Alnlet i

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Diffusion Inner

Length Shroud

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cm

Figure 11. 7-deg (0. 122-rad) ECA Snout-TypeDiffuser

FD 56939B

11

CALCULATIONS

Performance calculations included the determination of Reference Machnumber, combustion efficiency, total pressure loss, the outlet temperatureuniformity parameter, TPF, exhaust specie emission indices, and fuel/airratio from the measured concentrations of CO2 , CO, and THC.

Reference Mach Number

Reference Mach number is calculated from continuity using the averageinlet static pressure and assuming one-dimensional isentropic flow. Therefore,the Reference Mach number is determined by

Wa t3 / _ R

MREF Ps3 AREF + 71 ) M2] (1)[1+ ~2 M2EF]

where:

M = Mach number

Wa = Airflow

Tt 3 = Average diffuser inlet total temperature

Ps 3 = Average diffuser inlet static pressure

A = Area

Y = Ratio of specific heats

R = Gas constant

The numerical subscripts refer to engine station. The subscript "RE F" refersto reference area. The reference area is defined as the annular area betweenthe inner and outer combustor shrouds. The reference area is equal to 711 in2

(0.459 m2 ) in a full-annular combustor.

Combustion Efficiency

Combustion efficiency is defined as the ratio of the measured temperaturerise to the theoretical temperature rise. The theoretical rise is calculated fromthe fuel/air ratio (based on measured quantities of fuel and air flow), fuel proper-ties, and inlet temperature. The efficiency is expressed as:

T -TTt4m t3

Effmb = T (3)t4w t3

12

where:

Effmb = Combustion efficiency

Tt4m = Mass weighted average of 105 outlet total temperatures

Tt 4w

= Theoretical outlet total temperature

Total Pressure Loss

The combined diffuser-combustor total pressure loss is given by:

Ap Pt4 Pt3(4)

P Pt3

where:

AP= Total pressure loss expressed as a percentage of inlet

total pressure

P = Mass weighted average of 25 diffuser inlet total pressures

Pt4 = Mass weighted average of 105 combustor outlet total pressures

Outlet Temperature Pattern Factor (TPF)

Outlet Temperature Pattern Factor (TPF) is defined as the ratio of themaximum positive deviation from the average outlet temperature to the averagetemperature rise, or:

T -TTt4 max - t4

TPF = t4 t(5)t4 t3

where:

TPF = Temperature pattern factor

Tt4 max Maximum temperature at any location in thecombustor outlet

Tt4 = Average combustor outlet temperature

Outlet Radial Temperature Profile

Outlet Radial Temperature Profile is determined from the average of21 outlet total temperatures measured circumferentially at each of 5 radialpositions.

13

Exhaust Specie Emission Index

Exhaust Specie Emission Index is defined as the Ibm (grams) of any exhaustspecie per 1000 Ibm (kilograms) of fuel burned.

When the specie is measured as ppm by volume the EI is given by:

103 [ Me ) a )]

where:

EI = Emission index, Ibm (g) of specie per 1000 lbm (kg)of fuel

X = Volume concentration of specie, ppmsM s = Molecular weight of specie

M = Molecular weight of exhaust gases = moleculareweight of air

f/a = Fuel/air ratio (from measured values of fueland air flow)

If the exhaust specie is measured in percent volume then the EI is given by:

EI = 10Xs [( M) (1+ f/a)]

Where the volume concentration, Xs, is expressed as a volume percent.

Fuel/Air Ratio Calculated From Exhaust Emission Measurements

The combustor fuel/air ratio was calculated from the concentrations ofCO2 , CO and THC by the following equation:

CO + M ( 1 + THCh(C) 14 2 216 4

where:

THC = Concentration of hydrocarbons in ppmv (wet basis)

CO = Concentration of CO in ppmv (dry basis)

CO2 = Concentration of CO2 in % (dry basis)

f/a = Fuel/air ratio

14

H/C = Hydrogen/carbon ratio of fuel

Mc

= Molecular weight of carbon

Mh = Molecular weight of hydrogen

Ma = Molecular weight of air

This equation was derived assuming:

1. Dry intake air

2. No free H2 in exhaust

3. Hydrogen/carbon ratio of unburned hydrocarbons equals thehydrogen/carbon ratio of fuel. Also, the molecular weightof the unburned hydrocarbons equals the molecular weightof the fuel.

4. The combustion of the fuel in air yields only the products CO,CO2 , CaHb, H 2 0, 02, NO and N2

5. The perfect gas law applies.

RESULTS AND DISCUSSIONS

An exhaust emission survey has been conducted on a double-annular ram-induction combustor operating at simulated ground idle conditions. Measure-ments of CO, CO2 , THC, and NO were made. Various methods of reducing theemissions of CO and THC were investigated. These included: (1) fuel zoning,(2) fuel nozzle design, and (3) operating conditions. The results, that are dis-cussed below, are summarized in table I. Two methods of extracting gassamples from the flow were investigated and the results compared.

Fuel Zoning

THC Emissions

Figure 12 shows that radial fuel zoning reduced the emission levels of THCby over 5 to 1. This result was obtained with the simplex nozzles operating inthe radial (ID annulus only) injection mode. For a given overall combustorfuel/air ratio each ID annulus fuel nozzle was flowing twice the amount of fuelthat it would normally flow if both OD and ID annuli were operating. The testcondition was set at Tt3 = 200 ° to 226°F (366 ° to 381°K), MREF = 0. 057 - 0. 060and fuel/air ratio = 0. 007 - 0. 008. As the fuel/air ratio was increased theeffects of fuel zoning became less, as expected, until at the 0. 014 f/a point therewas no benefit in zoning the fuel flow.

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Figure 12. Comparison of Exhaust Emission Indices DF 92672for Simplex Nozzles Operating in Normal,ID Annulus Only, and Staggered Modes:Data Obtained With Fixed Rake Only

17

The staggered circumferential zoning (figure 1) did not reduce the THCemissions as well. This is probably due to excessive quenching of the combustionprocess brought about by the very large nozzle spacing of this arrangement. Eachpocket of burning gases is completely surrounded by a region of cold, nonreactinggases. Consequently, heat rejection to the surroundings is increased, resultingin premature quenching of the flame. By radially zoning the fuel to the innerannulus the exposure of the hot combustion gases to cold surroundings is greatlyreduced. This suggests that circumferential zoning of the type shown in fig-ure 13 would result in a reduction of THC emissions comparable to that of radialzoning.

* Operating Half

[ Nonoperating Half

Figure 13. One Method of Circumferential Fuel FD 63823Zoning

CO Emissions

The effect of fuel zoning on the emission levels of CO was quite different.At the 0. 007 f/a test points, normal mode fuel injection (all nozzles flowing)produced the lowest CO emissions. As the fuel flow was increased the normalmode emission level increased to a peak at a f/a around 0. 010, after which itbegan to fall, whereas in the radially zoned mode the emission level was highestat the 0. 007 f/a and decreased with increasing f/a. The reason for this differencein CO emissions between the zoned and unzoned injection modes can be explainedby examining the behavior of the combustion efficiency with f/a. Figure 14 is aplot of combustion efficiency for the test points of figure 12. The normal modeefficiency at the 0. 007 f/a point is so low (35%) that the bulk of the fuel passedout of the combustor unburned, consequently, very little CO was produced. Asthe f/a (and efficiency) increased, the production of CO increased. At a f/a ofapproximately 0. 010, the oxidation rate of CO to CO2 became large enough toresult in a decrease in CO. When the fuel is zoned, the combustion efficiencyat the low f/a point is improved to the point where a larger production of COresults.

18

ei X ....1,

60 (3673K) :--057-0,0:. i .:' .: t: i' lt It

-t !

-t--i -- <1AT --1 -Hi X ' S q

.. ,..4

Figure 14. Effect of Fuel Zoning on Combustion DF 92629Efficiency

A possible problem associated with fuel zoning is the effect of the distortedoutlet radial or circumferential temperature profiles on the structural integrityof an engine's hot sections. Figure 15 is a plot of the radial temperature profileobtained with the radially zoned injection mode at a f/a of 0. 014. The profiledistortion is not severe and the maximum profile temperature is well within thecapabilities of current turbine materials.

Fuel Nozzles

Three types of fuel nozzles were investigated. They were: (1) a simplex-type pressure atomizing nozzle, (2) an air blast air atomizing nozzle, and (3) anair assist air atomizing nozzle. For the sake of clarity, the differentiationbetween air blast and air assist nozzles is presented again. Air blast refers tothose air atomizing nozzles that operate on combustor pressure drop. Airassist refers to those air atomizing nozzles that receive their atomizing airfrom an external source.

19

l- . lD

- -- 90-

- 70

-60

--40

- - 30

- 20

10

_ - D-5 -4 -3 -2 -1 0 1 2 3 4 5

OUTLET RADIAL TEMPERATURE PROFILEDEVIATION FROM AVERAGE°F (Hundred)

__ .I I I I I I I

-3 -2 -1 0 I

OUTLET RADIAL TEMPERATURE PROFILEDEVIATION FROM AVERAGE OK (Hundred)

Figure 15. Outlet Radial Temperature ProfileRadially Zoned Fuel Injection

2 3

DF 92675

A comparison of the results obtained from each of the three nozzles isshown in figure 16. The nozzles were operating in the normal fuel injectionmode at an inlet temperature between 217°F and 242°F (376°K and 390°K). Thereference Mach number was between 0. 080 and 0. 082. The air assist nozzlewas operated with a nozzle air pressure drop of 20 psi (13. 8 x 104 N/m2 ).

At the lower f/a test point, both of the air atomizing nozzles gave lowerTHC emissions. The data of figure 16 show that reductions in THC emissionsof 2 to 1 were obtained with the air-atomizing nozzles. The CO emissionsfollowed the same trend described in the discussion of fuel zoning. As the f/awas increased the performance of the air blast nozzle became worse in relationto the other nozzles. This is apparently due to the test procedure. The testswere conducted at a constant airflow and pressure at all fuel/air ratios, con-sequently, the air energy available for atomization was constant. As the fuelflow was increased the air atomization energy per unit of fuel flow decreased.This resulted in a decrease in atomization quality with increasing fuel flow.This indicates that fuel zoning would not be as effective with this nozzle as withthe Simplex nozzle. Zoned fuel injection tests with the air blast nozzle were notconducted. The air assist nozzle did not suffer from this because a portion ofthe fuel atomization was accomplished conventionally by fuel pressure drop; asfuel flow was increased the pressure atomizing energy also increased.

20

Average Temperature12290 F (939OK) i_ _ 7j I t -a - _ I _

.1 Test.Conditions -

Inlet Temperature = 305 0 F (425-IK)CReference Mach No. - 0.060

' Fuel-AitrRatio 0.0138 - -

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t".,- ~~~~~~~~~~~~~~~~~~~~~~:<.ie-, :T 120:ps(38~

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-J~~~~~~~~~~~~~~~~~~~~~~~~;;

~. ~.d.;d,:~ :':.~: : : .=:>:: .z:':.~<,:4_;: ',' .-', '

Com ~.~. ' ' :-'.-l

Figure 16. Comparison of Emission Characteristics DF 92673of Three Fuel Nozzle Types Using NormalFuel Injection Mode: Data Obtained WithFixed Rake Only

21

si~ ~ ~~~::{ '- ;~.. : :.: :-:~>'::x'. 'i '-''.',i-:--: - :.'.:~-' -¥'

"i·~~~~ ~~.. .....- .,. ......~~~~~~~~~~~~~~~i:,':~'.=~o': :-:¥i :,::i::

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' : ~ ''

.

'= ' - " :

Figure 16. Comparison of Emission Characteristics DF 92673of Three Fuel Nozzle Types Using NormalFuel Injection Mode: Data Obtained WithFixed Rake Only

21

The effect of air assist nozzle air pressure drop is shown in figure 17.The THC emission index is plotted against fuel/air ratio for various air assistpressure drops. Figure 17 shows that increasing the nozzle airflow reducedthe THC emissions.

A comparison of the air assist and Simplex nozzles operating in the radiallyzoned fuel injection mode is shown in figure 18. The data were obtained at thelow inlet temperature (200 F, 367 K) and high reference Mach number (0. 08)test condition. Two important points are evident in the data: (1) by fuel zoning,the Simplex nozzles achieved emission levels as low as those achieved with theair assist nozzles without their attendant complexities, and (2) the fuel loadingin the inner combustion zone has exceeded the maximum allowable for peakefficiency. That this should occur at such a relatively low f/a ratio is evidentlydue to the high reference Mach number and the low inlet temperature. At the highreference Mach number the residence time is reduced; there is less time for fuelvaporization, ignition and reaction. The low inlet temperature inhibits fuel vapor-ization and reduces the chemical reaction rate. Together these two effects act toreduce the allowable fuel loading for peak efficiency.

AIR ASSIST AP - psi (NIcm 2 )

20 10 0(3.8) (6.9) (0)

I: -~ -- I ~-

i

500

400

1 200

x 100

zzo

F 50

0.05

Test Conditions

Tt3 - 211 - 242OF (373-3900 K)Mtef = 0.080 - 0.082

0.010FUELJAIR RATIO

0.015 0.019

Figure 17. Effect of Air Assist AP on THCEmission Levels

22

DF 92628

Et

i I

Figure 18. Comparison of Simplex and Air-Assist DF 92674Nozzles, Radially Zoned Fuel Injection:Data Obtained With Fixed Rake Only

23

Inlet Temperature and Reference Mach Number

The effect of inlet temperature and reference Mach number (MREF) on THCemissions is presented in figures 19 and 20. Figure 19 is plotted for the Simplexnozzles in the radially zoned mode. Figure 20 is plotted for the Simplex nozzlesin the normal mode. The data of both figures show that an increase in inlet tem-perature reduces THC emissions. This is the result of an improvement in fuelvaporization and an increase in chemical reaction rate brought about by the highertemperature. The effect of MREF is not so clear cut. In the radially zoned in-jection mode an increase in MREF resulted in an increase in THC emissions.However, in the normal injection mode the THC emissions decreased with in-creasing MREF. This shift in the influence of MREF on the THC emissions isapparently due to the decrease in fuel atomization brought about by the lower fuelflows at the lower MREF.

Nitric Oxide Emissions

The data for nitric oxide are very scattered as table I shows. Little canbe discerned in the data except that the emissions are very low, less than 2 lbm/1000 lbm fuel (g/ kg fuel).

Compressor Bleed

As stated in the introduction, idle emissions of THC and CO can be reducedby bleeding overboard large quantities of compressor discharge air. This raisesthe combustor fuel/air ratio, thus raising the combustion efficiency and loweringthe levels of the emissions. However, idle fuel consumption is increased ifidle thrust is maintained. Figure 21 shows the increase in fuel flow requiredfor a P&WATM JT8D-9 turbofan engine to maintain a constant thrust of 840 lb(3737N) for overboard bleeds up to 30%. At the above thrust level an overboardbleed of 30% gives a combustor fuel/air ratio of 0. 014, which is high enoughto effect considerable reductions in THC and CO emissions. This combustorstudy showed a reduction in THC emission index from 500 to 30 when the f/awas increased from 0. 007 to 0. 014. Depending on customer service bleed re-quirements, an overboard bleed of 30% requires almost a 20% increase in idlefuel flow. However, idle fuel consumption is such a small portion of aircraftoperating expense that this is not a large increase in overall cost. A moresignificant expense, as far as current engines are concerned, is the retrofittingof new or modified diffuser cases to provide the higher bleed flows. For futureengines, no significant cost increase should result if this feature is included inthe original design.

24

, A - ---- .- ;'S "i jt

.-' A- +T"4~~---..rxL- I

_ t -X-S, * ,I; z t t *vt

., * .. -,4. '' ---' 0 ' : -.2 , _ , 9 ,

i I-i~~~~~-

~~~~~~~~~~I *%-1---: .-,I- -:i :.4- 1i

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_:1. t t4WgS-_ R_ 'i4

:'-:-. . . -

if~f.--- 1*L~L [4·; I:

_ -Y;~2 D: ~4:L:9q2; r-i 42;5 ! t-~:i -

-F i ll " '' 3 -t :: I' "i=, . . ..

Figure 19. Effect of Inlet Temperature and ReferenceMach Number on THC Emission Index,Simplex Nozzles Radially Zoned

- 2~ L j : 2I0 4 '" 3'; _J LL :_- i i - : -

s:_:: .4 O: ............425 ............ ....t 375a_ a t )-ti- X: , 4 ,~~~. . .:,: t.,!,._'_-,,- ,.: . ' _

24 'T4T:.' ;.: .. T

7

t, ,°- . ,:l..:. :' :' '' :i

Figure 20. Effect of Inlet Temperature and ReferenceMach Number on THC Emission Index,Simplex Nozzles Normal Mode

.::200

' .

j,.

-- ~-I0

- -

' .'i ;

=-_ _ . _:_

''-| .:'wi A

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DF 92631

25

7.

-__ i_---- --"1:-ta '---'-2 7. +.t-:--i j-T.- -.- -

50i-. 0 ---- _- /i:ac .. =-

.*- ~: ' '.L4 -- i -.-5- 'X: .. 1. t A ... .1- - ; l'-44 ....

q_-~ IL- -'s. Idl :, - -t. ,' · . -- i ' . , .e 4 _ _ ,: .-V .. - . , !-- ~ . , . <: ' . · t .-- .t ' 't -: ' ': - i

.,..E:. I .., · I , -I .... =.:... .. .: j '4 .

- +-j---'- --t'-- - - .OVERBOARD BLEE --__---ty r---:-. - ,-t- -.. .::----:- --- 1- ..

Figure 21. Fuel Flow vs Percent Bleed - P&WA DF 92676JT8D-9 Turbofan Engine

Sampling Technique

Gas samples were extracted from the exhaust stream at two locations:(1) at the combustor outlet and (2) in the test rig exhaust duct approximately 13duct L/D's downstream from the combustor outlet. At the combustor outletthe sample was obtained by traversing with a 5-point, air-cooled rake. A morecomplete description of the sampling equipment is presented in Appendix C. Thefive sampling tips were connected to a common manifold so that an average radialsample was obtained at each circumferential location. The sample was thenvolume weighted to account for temperature variations, and an average emissionindex for each exhaust-specie of interest calculated. In the exhaust duct thesample gas was extracted at a fixed location with a 5-point, air-cooled rake. Thesample points were uniformly spaced across the duct.

Although traversing the combustor outlet is the most accurate method ofobtaining emission data, it is a time consuming process. Test time was almostdoubled when a sample traverse was taken. Consequently, the primary reasonfor using the fixed rake was to reduce test time. Use of this rake may incurslight errors due to the increased reaction time provided by the additional ductlength, and condensation of unburned hydrocarbons on the duct walls. To reducethe latter, the exhaust duct was uncooled for most of the tests except in the imme-diate vicinity of the combustor outlet. A comparison of the THC and CO 2 dataobtained with each rake is shown in figures 22 and 23. The data from the fixedrake are within 10% of being in exact correspondence with the traversing rake.Consequently, most of the data taken during the test program were obtained withthe fixed exhaust duct rake.

26

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Figure 24 shows typical circumferential profiles of emission index for thevarious exhaust species measured during the program. The data were taken withthe traversing rake during test No. 235 (table I). Note the extreme variation inthe emission indices across the combustor outlet. If fixed sampling rakes wererandomly installed across the combustor outlet the errors in the data could havebeen as large as 167% for the example given.

Lii:i j Rl" . ._ ., h .- .' " : . .... t' i eEi ;-k :'''

i- --- - i?- 1l ---- :

F -w-o4 .- 0 :-- - f

-: - .i *- -. .i.- I2 ' ~-' i. -. !. -i- "- t : i

IR --MO -i -N--1

__ __ 400 .'J _ ..... ,., _7-', _;, * _ i____ *~t/":', F

Figure 24. Circumferential Profiles of Exhaust DF 94460

28

_ -' 3tiS.- , -r t -- ;

L- 3 - ri

: 00/. .i .Ii ., -iV..-- ---- !---1 -+

-0- 1 LtS3 I 40 -1 j *

Figure 4. Circmferenia Poie ofi Exhus DFi 94460:1~-iLiIndces TetNo 3

28 ~ ~ 0i,, , .ib!,:1:ii; ·

A measure of the accuracy of the emission data is presented in figure 25.The bulk of the sample calculated fuel/air ratios fall within 10% of the fuel/airratios determined from measured fuel and airflows.

F F ' j ' 1 5 ' t,- .. ..... . ,: t ....

.j . . 1 :i--- - I__ 4 I

_ -OTt3 -=300-350 F (422-450 °K); MREF 0.080.082 ' 1: ·. {1]Tt3 =!200-240 OF (366-389 OK); MREF 0.08-0.082 '

.....- - t: -. .Tt3

=-300-350 OF (422450 OK); MIREp-F 0.0570.062 ---- . Tt3 = 200-230 OF (366-383 OK); MREF = 0.0570.,062 /:

.............. - *+10% 4Diation From , : , "//

'

-ExactCorrespondenc e

-. . .- .--5 - -;. -- - w--' -- -- --- |

' ; .Exact Correspondence

~0~~j- : i -0 i

'/ J . I0~ ~ -1 Deviation From'Exact

IO. -- g-~~0,~ ~~0.1 01 0 0i ; ,-0.015--V7 .oo:---. - -- g oo o~ -- 1 , ~ : -o~ms I i :¥F--

- 4: f : :i

Figure 25. Comparison of f/a Calculated From DF 92627Emission Data With f/a CalculatedFrom Measured Fuel and Airflows

29

SUMMARY OF RESULTS

An exhaust emission survey has been conducted on a double-annular ram-induction combustor operating at simulated ground idle conditions. The emissionlevels of CO, CO2 , unburned hydrocarbons and NO were measured. Variousmeans of reducing these emissions were investigated including (1) fuel zoning,(2) fuel nozzle design and (3) operating conditions. Following is a summary of theimportant results:

1. Fuel zoning is an excellent method of reducing the emissions ofCO and unburned hydrocarbons. By radially zoning the fuel flow(passing all of the fuel through the inner combustion annulus) areduction in unburned hydrocarbon emissions of 5 to 1 wasdemonstrated.

2. To achieve the best results with fuel zoning, widely separatedpockets of burning gases should be avoided since this causespremature quenching of the flame.

3. Use of air atomizing nozzles can reduce idle emissions ofunburned hydrocarbons and CO. Reductions in hydrocarbonemissions of 2 to 1 were demonstrated.

4. The air blast nozzle suffered from a decrease in fuel atomi-zation with increasing fuel flow due to the constant airflowand pressure test condition. This result indicates that fuelzoning would be less effective with this type of nozzle.

5. The THC emission levels obtained with the Simplex nozzles usedherein in the radially zoned fuel injection mode were as low as thoseobtained with the air assist nozzles in the same fuel zoning mode.

6. Increasing the combustor inlet air temperature decreasesthe THC and CO emission levels.

7. The effect of combustor reference Mach number on theemission levels of CO and THC is dependent upon the changein fuel atomization quality with changing Mach number. Ifthe atomization quality remains high a decrease in referenceMach number results in a decrease in the above emissions.If, however, the fuel atomization quality deteriorates signifi-cantly with a decrease in reference Mach number, becauseof lower required fuel flow, the emissions will increase.

8. The outlet radial temperature profile obtained with the radiallyzoned fuel injection mode poses no problem to the structuralintegrity of an engine's hot sections.

9. The nitric oxide emissions were low (less than 2. 0 Ibm/1000 lbm fuel (g/kg) for all test conditions and fuelinjection modes.

30

10. A reduction in hydrocarbon emissions similar to that obtainedwith fuel zoning should also be obtainable by operating withhigher-than-normal compressor bleed flow. However, analysisindicates a 20% increase in idle fuel consumption is incurredwith this approach.

11. Large circumferential variations in emission levels wereobserved at the combustor outlet. Accurate emissionmeasurements can be obtained at the combustor outlet onlyby traversing the entire outlet or using a very large numberof stationary probes.

31/32

APPENDIX AEQUIVALENT CONICAL ANGLE

Definition

The equivalent conical angle (ECA) is defined as the included angle of aconical diffuser that has the same area ratio, inlet area, and wetted surfacearea as the diffuser under investigation. For annular diffusers, ECA may beapproximated by the following equation:

A2

A1

ECA = 2 tan - 1 L (+ R2 + R3 + R4 )

where the symbols are defined by:

]

Application

The above equation for ECA does not consider the presence of struts inthe diffusing passage. The equation was used only to arrive at an area ratio fora given ECA and diffusing length assuming that no struts were in the passage.In adding struts, the diffuser wall exit radii were adjusted to maintain the samearea ratio.

33/34

APPENDIX BTEST FACILITY AND TEST RIG DESCRIPTION

Test Facility

All combustion tests were conducted on test stand D-33B at the P&WAFlorida Research and Development Center. Combustion air was supplied bybleeding the compressor discharge of a JT4 turbojet engine. Airflow rate wascontrolled by a pneumatically operated 10 in. (25.4 cm) inlet butterfly valvewith vernier control by a 4 in. (10. 16 cm) pneumatically operated supply linebleed valve.

The test stand fuel system was capable of supplying each of three com-bustion zones with 300 pph (136. 08 kg/hr) of ASTM-A1 type fuel at 750 psig(517 N/cm2 ) fuel pressure. Control room monitoring of fuel pressure andtemperature was provided for each zone.

The test facility had high pressure air service available for cooling thegas sample rakes.

Test Rig Description

A brief description of the major components of the combustor test rig ispresented below. For reference, a cross section of the rig is presented infigure 26. The rig was constructed entirely of AISI type 300 Series stainlesssteel.

Exhaust Valve

Flow Spreader

Airflow

I trst

VenturiFlow

Straightener

PstPtTt

HeaterBurner

Chamber

PstTt

Pt

TraverseAssembly

Pt

TtPst

40 ft (12.2 m)of Straight Pipe

InstrumentationSection

Figure 26. Double-Annular Combustor Test Rig FD 13874D

Flow Straightener

This section was designed to smooth out any irregularities in rig inlet air-flow and to provide a near stagnation region for accurate measurement of inlettotal pressure and temperature. The flow straightener was fabricated from a12 in. (30.480 cm) diameter cylinder 24 in. (60.960 cm) long. A bank of1.5 in. (3.81 cm) diameter tubes 12 in. (30.480 cm) long was used to straightenthe inlet airflow.

35

Venturi

This section provided accurate airflow measurement with minimum pres-sure loss. The rig airflow entered through a constant radius inlet to a 4. 7483 in.(12. 0607 cm) diameter throat. Transition from the venturi throat to the preheaterinlet was provided by a conical diffusing section 40. 840 in. (103. 7 cm) long witha 12 deg, 31 min (0. 218-rad) included angle.

Preheater

The preheater was not used in this portion of the test program. The inlettemperature to the combustor was simply that obtained from the JT4 slave enginecompressor bleed air.

Plenum Chamber

The plenum chamber functioned to provide airflow to the rig test section atuniform temperature and pressure. This was accomplished by discharging theairflow from the preheater through a multihole flow spreader into a large volumecontainer. The plenum was fabricated from a cylinder 29. 250 in. (74. 295 cm)in diameter and 48 in. (121. 920 cm) long. To ensure a uniform profile into therig test section, a bellmouth flange was incorporated to transition from theplenum exit area to the test section inlet area. Bosses were installed near theexit of the plenum for the installation of temperature sensors to measure thecombustor inlet temperature.

Instrumentation Section

This section housed the instrumentation used to determine the diffuser inlettotal pressure, static pressure, and pressure profiles. It was designed tosimulate a quarter section of the compressor discharge of a full-scale engine.

Diffuser-Combustor Case

This section housed the combustor hardware and functioned to direct theinlet airflow into the combustor liners.

Traverse Case

This section housed the outlet temperature and pressure traversing rakeand the traversing gas sample rake.

Exhaust Duct

This section housed the fixed gas sample rake. It was sufficiently long tothoroughly mix the exhaust gases and to develop a uniform flow profile.

Exhaust Valve

This was an electrically driven valve used to back pressure the test rig.

36

APPENDIX CINSTRUMENTATION

Basic Performance Instrumentation

Instrumentation was provided to measure the following parameters.

1. Combustor airflow

2. Fuel flow for each combustion zone (combustor outer andinner annuli)

3. Fuel temperature and pressure for each zone

4. Combustor inlet total temperature, total pressure and staticpressure

5. Combustor outlet total temperature and pressure. Theoutlet static pressure was assumed to be ambient.

6. Miscellaneous diffuser and combustor total and static pres-sures.

A cross section of the test rig, showing the location of the various instru-mentation planes, is shown in figure 27. A brief description of the instrumenta-tion and monitoring equipment used is described below.

Airflow

As mentioned in the section on test rig hardware (Appendix B), the com-bustor airflow was measured with a venturi meter. The inlet total temperatureand pressure sensors were located in the flow straightener approximately 12 in.(30.480 cm) upstream of the venturi throat. Two chromel-alumel, shieldedthermocouples spaced 180 deg (3. 141 rad) apart measured total temperature,and two kiel-type pressure probes spaced 180 deg (3. 141 rad) apart measuredtotal pressure. The static pressure at the venturi throat was measured withtwo wall taps spaced 180 deg (3. 141 rad) apart.

The venturi inlet temperature was monitored on a 0°F to 1600 F (255. 4 Kto 1144. 3 ° K) indicating potentiometer, and the total and static pressures on0 to 80 in. (0 to 2. 03 m) mercury-filled, U-type manometers.

Fuel Flow

Fuel flow to each of the two combustion zones was measured by turbine-type flowmeters. The data from these meters were monitored on a 5-channel,preset digital counter. Fuel temperature was measured by a chromel-alumelimmersion thermocouple and monitored on an indicating potentiometer. Fuelpressures were measured by wall static pressure taps located in the inlet supplylines and were monitored on 0 to 1000 psig (0 to 699. 6 N/cm2 ) pressure gages.

37

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Test Section Inlet

Instrumentation to measure airflow proper t ies at the test section inlet included:

1. Four, shielded, chromel-a lumel thermocouples located as shown in figure 27. These thermocouples were monitored on a 0 to 1600 °F (225.4 °K to 1144. 3 °K) indicating potentiometer.

2. Five, 5-point, total p r e s su re rakes (figure 28) located as shown in figure 27. The data from these rakes were monitored on 0 to 80 in. (0 to 2.03 m), mercury-f i l led U-type manomete r s .

3 . Five wall s tat ic p r e s su re taps located as shown in figure 27. The data from these sensors were monitored on 0 to 80 in. (0 to 2.03 m), mercury-f i l led , U-type manomete r s .

Figure 28. 5-Point Inlet Total P r e s s u r e Rake FE 92891

Combustor Outlet

Airflow proper t ies at the combustor outlet were measured with a 5-point total t empera ture and p r e s s u r e rake (figure 29). The tempera ture measu re ­ments were obtained with aspirated platinum - 20% rhodium/platinum -5% rhodium thermocouples. The p re s su re difference between test p r e s su re and ambient served to asp i ra te the thermocouples. The temperature data were taken in 3 deg (0. 052 rad) increments a c r o s s the combustor outlet and were measured on 0-10 millivolt digital vol tmeter .

The outlet total p r e s su re was measured by the five 1/8 in. OD tubes shown in figure 28. These tubes were cupped on the end to increase the acceptance angle at which accurate data could be obtained. These p r e s su re data were measured on 0 to 80 in. (0 to 2.03 m), mercury-f i l led , U-type manometers . The outlet static p r e s s u r e was calculated using measured airflow, total p r e s ­sure and t empera tu re .

39

Figure 29. Outlet Total Tempera ture and Total P r e s s u r e Rake

FE 55370

Gas Sample Instrumentation

Exhaust gas samples were extracted from the test r ig at two locations: (1) in the exhaust duct 13 L / D ' s downstream from the combustor outlet and (2) at the combustor outlet.

Described below a re the rakes used in collecting the samples and the equipment used to measure the concentrations of the exhaust species of interes t .

Fixed Exhaust Duct Gas Sampling Rake

This rake , figure 30, was a 5-point rake with all the sample ports connected to a common manifold. The probe was constructed as a double-walled tube, the center tube being the gas sample manifold. High p re s su re a i r at approximately 100° F (311°K) is passed through the annular passage between the sample mani­fold and the outer tube to cool both the probe and the sample gas . The cooling airflow was regulated to maintain the sample tempera ture within 300 to 400°F (422 to 478°K).

40

Sample Gas Out-- db111

Cooling Air In Cooling Air In

0 Cooling Air Out

Figure 30. Exhaust Enclosure Stationary GasSampling Probe

FD 47396A

:41

Traversing Gas Sampling Rake

This rake, figure 31, was a 5-point rake with all of the sample portsconnected to a common manifold. As shown, the rake attached directly to thetotal temperature rake so the same actuating mechanism could drive both rakes.The sample ports were spaced at the same radial locations as the temperatureand pressure sensors. The sample rake was mounted 6 deg from the temper-ature and pressure rake. Since data were taken in 3 deg increments, temper-ature and pressure data were available at each sample point. From this thesample data could be volume weighted to account for temperature and pressurevariations across the combustor outlet. The sample gas was cooled in thesame manner as the fixed exhaust duct rake. The sample manifold tube wasplaced inside another tube and high pressure cooling air was passed throughthe annular gap between the two. The cooling airflow could be regulated tomaintain the sample temperature within 300 to 400°F (422 to 478°K). Thisassembly was placed in a water-cooled housing to protect it from locally hightemperatures which result from zoned fuel injection.

Sample Transfei Line

The sample transfer line (figure 32) was an electrically heated teflon lineapproximately 10 ft (3. 048 m) long. The line was insulated with foam rubber andasbestos insulation. A plastic tube outer covering served as a weather protection.

Sample Analyzing Instrumentation

The sample measuring instruments used in the program were all of theon-line continuous monitoring types. The concentration of unburned hydro-carbons was determined with a flame ionization detector (FID). The concen-trations of CO, C0 2 and NO were measured with NDIR (Nondispersive Infrared)instruments. The concentrations of NO2 , when taken, were obtained with aNDUV (Nondispersive Ultraviolet) instrument. These instruments were mountedon a mobile cart (figure 33) to place them as close to the test rig as possible.A plumbing schematic of the equipment cart is shown in figure 34.

42

•5 Point Pt-20Rh/Pt-5Rh Total Temperature and Pressure Rake

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Asbestos Insulation

Plastic Tube for Weather Protection

Foam Rubber Insulation

Teflon Sample Tube

Electric Heating Wire

Figure 32. Cross Section of Sample Transfer Line FD 63828

Figure 33. Gas Analysis Equipment Cart FC 25301

VENT

VACUUM VACUUMPUMP PLENUM

1. 10MICRON FILTER 6. CALIBRATION GAS 11. CARBON MONOXIDE ANALYZER

2. DIERITE CYLINDER 7. HYDROCARBON ANALYZER 12. CARBON DIOXIDE ANALYZER3. PARTICULATE TRAP 8. WATER VAPOR ANALYZER 13. COOLING COIL AND ICE BATH

4. CALIBRATED ORIFICES 9. NITRIC OXIDE ANALYZER 14. WATER SAMPLE TAP

5. OVEN TEMPERATURE 10. NITROGEN OXIDE ANALYZER 15. 50-MICRON FILTER

(i TEMPERATURE SENSOR ( PRESSURE SENSOR

Figure 34. Flow Schematic - Gas Analysis FD 58417Equipment Cart

45

RE FERENCES

1. Clements, T. R., "Interim Report - 90-Degree Sector Development ofa Short Length Combustor for a Supersonic Cruise Turbofan Engine,"NASA CR-72734, 1970.

2. Clements, T. R., "Second Interim Report - Development of a ShortLength Combustor for a Supersonic Cruise Turbofan Engine Using a90-Degree Sector of a Full Annulus, " NASA CR-120908, 1972.

3. Perkins, Porter J., Donald F. Schulz, and Jerrold D. Wear, Full-Scale Test of a Short-Length Double-Annular Ram-Induction TurbojetCombustor for Supersonic Flight, " NASA TN-D6254, 1971.

4. Sawyer, Robert F., "Reducing Jet Pollution Before it Becomes Serious,"Astronautics and Aeronautics, April, 1970.

5. Anon., "Nature and Control of Aircraft Engine Exhaust Emissions,"Report No. 1134-1, Northern Research and Engineering Corp., 1968.

6. Heywood, John B., James A. Fay, and Lawrence H. Linden, "JetAircraft Air Pollutant Production and Dispersion, " Paper presented toAIAA 8th Aerospace Sciences Meeting, New York, New York, 1970.

7. Norster, E. R., and A. H. Lefebvre, "Effects of Operating Conditionand Fuel Injection Method on Gas Turbine Combustor Emissions,"Cranfield Institute of Technology, Date Unknown.

8. Grobman, Jack, "Effect of Operating Variables on Pollutant EmissionsFrom Aircraft Turbine Engine Combustors," NASA TMX-67887, 1971.

9. Chamberlain, John, "The Ram-Induction Combustor Concept," presentedto AIAA third Propulsion Joint Specialist Conference, Washington, D. C.,1967.

46