216 J. ENERGY VOL. 4, NO. 5

ARTICLE NO. 80-4105

Fuel Property Effects on Life Characteristicsof Aircraft Turbine Engine Combustors

C.C. Gleason* and D.W. BahrfGeneral Electric Company, Cincinnati, Ohio

Results of a program to determine the effects of fuel properties on the life characteristics of twoUSAF/General Electric aircraft turbine engine combustors are presented. Thirteen test fuels were evaluated inan older technology cannular combustion system (J79) and in an advanced-technology, virtually smokeless,compact, annular combustion system (F101) over wide ranges of simulated engine operating conditions. Fuelvariables were hydrogen content, aromatic structure, volatility, and distillation end point. Significant increasesin combustor liner temperatures were observed as fuel hydrogen content was decreased. With fuel hydrogencontents of 14.5,14.0,13.0, and 12.0, the resulting relative combustor liner cyclic life predictions are 1.00, 0.78,0.52, and 0.35 for the J79 combustor and 1.00, 0.72, 0.52, and 0.47 for the F101 combustor, respectively. Basedupon these findings, it is concluded that improved liner cooling design features will be needed in most current-technology combustors to accommodate the projected lower hydrogen contents of future fuels.

NomenclatureTL = combustor liner temperature, KT3 = combustor inlet air temperature, K

Subscriptsmax = maximum (or peak)jp-4 = baseline value, with JP-4 fuel

Introduction

FOR more than 25 years, the primary fuel for U.S. AirForce gas turbine powered aircraft has been JP-4, a wide-

cut distillate with excellent combustion characteristics andlow-temperature capability. However, conversion to lowervolatility JP-8, which is similar to commercial Jet A-l, hasbeen under consideration since 1968 for reasons of NATOstandardization and reduced combat vulnerability.

Domestic crude oil production peaked in 1971 and has beensteadily declining since that time, while demand has continuedto increase. Thus, particularly since 1973, the cost andavailability of high-grade aircraft turbine engine fuels hasdrastically changed. These considerations have spurred ef-forts to determine the extent to which current U.S. Air Forcefuel specifications can be broadened to increase the yield fromavailable petroleum crudes and ultimately permit productionfrom other sources, such as coal, oil shale, and tar sands.Such broadened-specification fuels are expected to havehigher aromatic contents than presently available aircraftturbine engine fuels. Therefore, a key element of these effortsis to assess the impacts of increased fuel aromatic contents, orreduced hydrogen contents, on engine and combustor per-formance and operating characteristics.

Presented as Paper 80-GT-55 at the ASME Gas Turbine Conferenceand Products Show, New Orleans, La., March 10-13, 1980; receivedApril 23, 1980; revision received July 21, 1980. Copyright ©American Institute of Aeronautics and Astronautics, Inc., 1980. Allrights reserved.

Index categories: Alternate Fuels; Combustion and CombustorDesigns; Structural Durability (including Fatigue and Fracture).

* Senior Engineer, Alternate Fuels Technology, Aircraft EngineGroup. Member AIAA.

tManager, Combustion and Emission Control, Aircraft EngineGroup.

As a result of the current and projected fuel situation, theU.S. Air Force has established an Aviation Turbine FuelTechnology Program to determine the properties of anaviation turbine fuel which will result in adequate fuelavailability, minimize the total cost of aircraft systemoperation, and avoid sacrifices in engine performance, flightsafety, or environmental impact.l Engine, airframe, logistic,and fuel processing data are being acquired to develop thesespecifications. As part of these efforts, the General ElectricCompany conducted two contractual programs to evaluatethe effects of possible future fuel property variations on theperformance, pollutant emission, and durability charac-teristics of the J79 and F101 engine combustion systems.2'3This paper summarizes the durability portion of the results.The pollutant emission portion of the results are summarizedin a companion paper.t

Test FuelsThirteen test fuels were supplied by the U.S. Air Force for

evaluation in both the J79 and F101 engine combustionsystems. The fuels included JP-4, JP-8 (which was out ofspecification on freeze point), five special blends of the JP-4,five special blends of the JP-8, and No. 2 diesel. The specialblends were made up by the U.S. Air Force to span the ex-pected possible future reductions in fuel hydrogen content.Three different levels of hydrogen content (12, 13, and about14% by weight) were included in the test fuel matrix. Twodifferent types of aromatics were used to reduce the hydrogencontent of the base fuels: a monocyclic aromatic (xylenebottoms) and a predominantly dicyclic aromatic described bythe supplier as "2040 Solvent" (a naphthalene concentrate). Athird blend component, used to increase the final boiling pointof two blends, is described as "Mineral Seal Oil," apredominantly (88%) paraffinic white oil.

This test fuel matrix was selected to span systematically thepossible fuel variations in key fuel properties that might bedictated by petroleum-derived jet fuel availability and costtrends, the possible change from JP-4 to JP-8 as the primeU.S. Air Force aviation turbine fuel, and the possible futureuse of nonpetroleum sources for jet fuel production. The No.2 diesel fuel was selected to approximate the ExperimentalReferee Broad Specification (ERBS) aviation turbine fuelsuggested by NASA.4 Selected properties of the fuels arepresented in Table 1. Additional properties are given in Refs.2,3, and 5.

JSee pp. 223-226

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Table 1 Combustor test fuel properties

Fuel No.123456789

10111213

FuelDescription

JP-4JP-8JP-8/GMSOa blendJP-8/2040b blendJP-8/XBc blendJP-8/XB blendJP-8/2040 blendJP-4/2040 blendJP-4/2040 blendJP-4/XB blendJP-4/XB blendJP-4/XB/GMSO blendNo.-2diesel

Hydrogencontent,

wt.%(ASTM D3701)

14.514.013.912.013.012.013.012.013.012.013.014.013.1

Aromaticcontent,

volume, %(ASTMD2789-71)

10.912.412.542.031.550.925.341.227.453.435.716.519.9

Naphthalenescontent,

volume %(ASTMD2789-71)

0.80.91.0

24.61.61.0

12.024.413.70.30.40.65.2

Heatingvalue,

MJ/kg(net)(ASTM D240)

43.6043.2143.1941.9542.7242.1342.5642.2042.6342.2042.6843.3742.69

Distillationrange, K

(ASTM D86)338-524444-552436-572449-547423 - 544423 - 541445 - 546340-544339-539346-512339-520341-573444-615

Kinematicviscosityat 31 IK,mm2/s

0.821.561.721.511.221.001.510.990.900.740.740.932.56

aGulf Mineral Seal Oil, a predominately paraffinic white oil. b2040 Solvent, a naphthalene concentrate (dicyclic aromatic). cXylene bottoms, a monocyclicaromatic.

Engine/Combustion SystemsJ79 Engine/Combustor

The J79 is a lightweight, high-thrust, axial-flow turbojetengine with variable afterburner thrust. The engine wasoriginally qualified in 1956, and the model currently in widestuse by the U.S. Air Force, the J79-17A, was the referenceengine for this program. The engine pressure ratio is 13.4.

The J79 combustion system, shown in Fig. 1, is a cannulardesign incorporating 10 combustor liner assemblies. Eachassembly consists of three sheet metal parts (forward outerliner, inner liner, and rear liner) which are riveted together.The forward outer liner serves as an airflow splitter betweenthe inner and rear liners. Cooling air is admitted throughpunched and formed louvers in the inner and rear liners.Combustion and dilution air is admitted through a series ofthimbled holes in the inner and aft liners. Adjacent com-bustors are joined near the forward ends by cross-ignitiontubes to allow propagation of flame from the combustorswhich are equipped with spark igniters. Each combustor isequipped with a dual-orifice, pressure-atomizing fuel nozzle.

The original combustor design features a rich burning zone,which results in excellent relight capability but relatively highinner liner temperatures and high smoke emission levels.During the evolution of the J79 engine family, combustorshaving improved life and low smoke have been developed.However, for this program, the original design without theselow smoke and improved life features was evaluated, since itis the model in most widespread use by the U.S. Air Force.The life-limiting component of the combustor is the innerliner. During service use, these liners develop cracks at thecooling louver ends due to thermal fatigue.

TURBINE INIITSTATOR VANES-

' TRANSITION DUCT-

-INNER LINER rREAR LINER

Fig. 1 J79 engine combustion system flowpath.

SECONDARY DILUTIONHOLES-

PRIMARY DILUTIONHOLESn

-COOLING SLOTCOOLING AIR ENTRY HOLES

-PRIMARY SWIRLER

Fig. 2 F101 engine combustion system flowpath.

F101 Engine/CombustorThe F101 engine is an advanced, lightweight, fully

augmented turbofan engine. The engine completed productverification in 1976. The engine pressure ratio is 26.8.

The F101 combustion system, shown in Fig. 2, is a veryshort-length annular design that features machined ringliners, a step diffuser, and two-stage counter-rotating airswirlers, which permit the use of low-pressure-drop fuelinjectors. The combustor dome contains an annular array of20 air swirlers and transition splash plates which are im-pingement-air cooled. The remainder of the dome and theliner surfaces are film-air cooled. The film cooling air isintroduced through a series of machined slots, which are fedby closely spaced holes.

The combustor design features a relatively lean primaryzone and a high degree of fuel-air mixing uniformity, whichresults in very low smoke emission levels and relatively long

combustor life. The life-limiting components are usually therear sections (panels) of the liners, which are affected by lowcycle fatigue from thermal gradients.

Experimental Facilities and ProceduresTest Facilities and Instrumentation

The combustor tests were conducted in high-pressure rigs,which simulate the engine flowpaths from the compressoroutlet to the turbine inlet planes. Simulated compressordischarge airflows were heated in indirect gas-fired heatersand metered with standard ASME sharp-edged orifices. Fuelflow rates were metered with calibrated turbine flowmeterscorrected for the density and viscosity of each test fuel at themeasured supply temperature. Combustor inlet and exitpressures and temperatures were measured with standardprobes.

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218 C.C. GLEASON AND D.W. BAHR J. ENERGY

The J79 tests were conducted in a single combustor rig,which simulates a one-tenth sector of the engine flowpath.Simulated turbine cooling air (about 16% of compressordischarge flow) was withdrawn through bleed pipes near thecombustor exit and metered in order to duplicate exactly theengine combustor cold-side air velocities. Combustor linertemperatures were measured by an array of 24 thermocoupleslocated in the hottest known regions of the inner liner. Aportion of this thermocouple installation is shown in Fig. 3.

The F101 tests were conducted in a full annular combustorrig, which simulates the engine flowpath. However, turbinecooling airflow (about 18% of compressor discharge flow)was not simulated in this rig, so liner cold-side air velocitieswere low relative to the engine. Combustor liner temperatureswere measured by an array of 33 thermocouples located in thehottest known regions of the liners. A portion of this ther-mocouple installation is shown in Fig. 4.

Test ProceduresThe 13 test fuels were evaluated in each engine combustor

according to the test point schedule shown in Table 2. Datawere obtained at simulated engine idle, cruise, takeoff, anddash operating conditions. At each engine operating con-dition, data were obtained at two fuel/air ratios, which werenormally 80 and 100% of the engine cycle value corrected forthe test fuel heating value.

For the J79 tests, a separate rig buildup and test run wasmade for each fuel in order to assess the carbon builduptendencies as well as to measure combustor performance andemission characteristics. Two identical combustor assemblieswere utilized. Thus, while one was undergoing installationand test, the other one was undergoing inspection, cleaning,and instrumentation refurbishment, as needed. Both com-bustors were tested with the baseline fuel, JP-4. A total of 14test runs were made.

For the F101 tests, the same combustor assembly wasutilized in all tests, and all fuels were evaluated in threecombustor buildup/installations. Between the first andsecond test series, the combustor was utilized for a series ofdevelopment tests in another program, after which it wasreconfigured to the original geometry and reinstrumented forthe final two test series in this program.

Data Analysis ProceduresThe experimental data were analyzed to 1) correct the data

to true engine operating conditions as needed, 2) correlate thedata with combustor operating and fuel property parameters,and 3) determine the effects of properties on combustor life.Details of these analysis procedures are presented in Refs. 2and 3.

For the J79, the tests were run at essentially true engineoperating conditions, so no corrections were needed. Corn-

Fig. 3 J79 combustor inner-liner temperature instrumentation. Fig. 4 F101 combustor inner-liner temperature instrumentation.

Table 2 Combustor test conditionsRig operating conditions

EnginecombustorJ79

F101

Testpoint

1234567812345678

Inletpressure,

MPa0.2480.2480.4710.4711.3591.3591.1911.1910.3900.3900.9770.9771.2531.2531.2451.245

Inlettemperature,

K421421559559664664781781468468678678829829849849

Referencevelocity,

m/s24.224.227.227.228.628.633.533.518.318.321.021.023.523.524.124.1

Fuel/airratio, ag/kg

7.59.4

10.913.616.012.012.812.811.013.818.923.623.028.721.927.4

OperatingconditionIdleIdleCruiseCruiseTakeoffTakeoffDashDashIdleIdleCruiseCruiseTakeoffTakeoffDashDash

Engine simulationInlet

pressure,%

100.0100.0100.0100.0100.0100.075.075.0

100.0100.0100.0100.046.146.136.436.4

Fuel/air ratio,%80.0

100.080.0

100.080.060.080.0

100.080.0

100.080.0

100.080.0

100.080.0

100.0aBased on JP-4 fuel. For other fuels adjust by heating value.

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SEPT.-OCT. 1980 FUEL PROPERTY EFFECTS 219

bustor life predictions were, therefore, based upon themeasured peak metal temperature rise and the louver crackpropagation rate curve shown in Fig. 5. This crackpropagation rate curve was established experimentally bysubjecting a test specimen simulating a small portion of thecombustor liner to thermal gradients with alternating heatingand cooling cycles.

For the F101, the test data were corrected to true engineoperating pressure and cold-side velocity conditions by use ofa two-dimensional finite-element heat-transfer model, itemsof which are shown in Fig. 6. In the region of air entry holes,special conduction and convection inputs to the model aremade to account for local three-dimensional effects.Corrected temperature data were then input to a two-dimensional stress analysis program together with mechanicaland aerodynamic loads to calculate the elastic stressesthroughout the structure. These stresses were then used withthe material low-cycle fatigue properties (Fig. 7) to predictcyclic life to first crack initiation. For the long-life F101combustor design, engine test experience has shown that totalcombustor life is proportional to this calculated first cracklife.

Results and DiscussionJ79 Results

In general, liner temperature data were well ordered and ingood agreement with previous data insofar as comparisonscould be made. A typical measured temperature distributionis shown in Fig. 8. A summary of the peak liner temperaturedata for all fuels and operating conditions is presented inTable 3. The strong effect of fuel hydrogen content on peakliner temperature at takeoff operating conditions is shown inFig. 9. The data correlate within about ±16 K, apparentlyindependent of combustor assembly and any other fuelproperty such as aromatic structure and distillation tem-peratures.

F101 ResultsThe F101 liner temperature data were likewise generally

well ordered and in good agreement with previous data in-sofar as comparisons could be made. A typical measuredtemperature distribution is shown in Fig. 10. Peak tem-peratures always occurred on the outer-liner third panel ateither 18 or 36 deg from top center, positions which are bothmidway between fuel injectors. Figure 11 shows typical testdata for this hottest liner panel, together with computermodel estimates of the temperature profiles along the panel.

10

HASTELLOY X SHEET STOCK

200 300 400 500 600 700

(TL - T3) METAL TEMPERATURE RISE, K

Fig. 5 Effect of temperature gradient on J79 combustor louver crackpropagation rate.

FILM " GAS " ^(TGAS " TCOOLANl)WHERE

7 =FILM EFFECTIVENESS

'GAS = FLAME TEMPERATURE

'COOLANT - COOLANT TEMPERATUREQ/A - R A D I A T I O N

TO CASING

BACK S IDEHEAT TRANSFER TO T,COOLANT

COOLANT FLOW

I -KATI I—T

————fc-h GAS SIDE9 HEAT TRANSFER

TFILM BOUNDRY

Q/A -FLAME RADIAT ION

Fig. 6 Node model for F101 combustor panel heat-transfer andstress analysis.

100

• HASTELLOY X SHEET STOCK• STRAIN CYCLINGr AVERAGE PROPERTIES

Fig. 7

I04

CYCLES TO F A I L U R EMaterial fatigue diagram for F101 combustor life analyses,

105

400-

300

200

100-

0

800

O

O 60°D 300°

O

A A 164°A O 196°

ANGULARLOCATIONAFT LOOKINGFORWARD

• JP-4FUEL•TAKEOFF OPERATING

CONDITIONS

Fig. 8 Typical J79 combustor measured temperature distribution.

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220 C.C. GLEASON ANDD.W. BAHR J. ENERGY

A good match is indicated. Based upon a series of similarcalculations, the corrections for rig to engine operatingconditions were determined to be 0, -16, + 35, and + 50 K atidle, cruise, takeoff, and dash operating conditions,respectively. A summary of the corrected peak liner tem-perature data for all fuels and operating conditions ispresented in Table 4; the takeoff data are plotted against fuelhydrogen content in Fig. 12. The general level of the dataobtained in buildup 1 seems to be about 32 K higher than thatfrom buildups 2 and 3, probably due to the reconfigurationand reinstrumentation; but the slopes of the two curves ap-pear to be about the same. The data for buildups 2 and 3 liewithin about the same 16 K band exhibited by the J79 data,and again the strong effect of fuel hydrogen content and noeffect of aromatic structure are evident. There does, however,appear to be a minor effect of fuel distillation range in thesedata, which was not evident in the J79 results. The No. 2diesel and JP-8 fuel blends tend to produce slightly highertemperatures than do the JP-4 blends, for the same hydrogencontent.

Comparison of ResultsThe two engine combustors utilized in these investigations

differed greatly in design technology:1) The J79 combustor is a cannular design, with louver-

cooled sheet metal liners, a rich primary zone, pressureatomizing fuel injectors, and relatively high smoke emissionlevels.

2) The F101 combustor is an annular design with advancedfilm-cooled machined ring liners, a lean primary zone, air-

Table 3 J79 liner temperature results

FuelNo.

1123456789

10111213a Rig dat£

Combustorassembly

No.12121212221212

i, as measured.

Table 4Combustor

(7i,max--T3)*Peak inner liner temperature rise, K

Idle180212210210265245305260370314345295224310

Cruise315340340340428395420365440409420410342410

Takeoff425440428450502482382446478471480465450482

Dash450475465495545515528476506495520495480500

F101 liner temperature results

( TL.max -T3)*Instrumentation

FuelNo.

123456789

10111213

buildupNo.

1112222223333

Peak liner temperature rise,Idle166161157179156161169177169166161163155

Cruise270282283308275296278291272283270261280

Takeoff383409414437401432395409385405387370410

KDash383405408432397425393407385402385371405

blast-type fuel injection and very low smoke emission levels.This combustor is designed to meet long cyclic liferequirements.

In spite of these significant design and performance dif-ferences, the effects of fuel property variations on peak linertemperatures were very similar. Both combustors are sensitiveto fuel hydrogen content and virtually independent ofaromatic structure and distillation temperatures, within therange tested. As shown in Figs. 9 and 12, peak liner tem-perature rises at takeoff operating condition are about 70 Klower for the F101, but the slopes are about the same (-23K/% hydrogen) for both combustors. This finding suggeststhat the increased flame radiation levels associated withreduced fuel hydrogen contents result in generally linearincreases in liner temperatures, in the case of conventionalcombustors designed to operate at high power with near-

<LUQ.

1

600

500

400

300

RIG DATA MEASURED AT TRUE ENGINE TAKEOFFCONDITIONS

+ 16 K

O JP-4 FUEL BLENDSD JP-8 FUEL BLENDSA NO. 2 DIESEL FUEL

FLAGGED SYMBOLS: COMBUSTOR ASSY NO. 1UNFLAGGED SYMBOLS: COMBUSTOR ASSY NO. 2

11 12 13 14FUEL HYDROGEN CONTENT, WEIGHT PERCENT

15

Fig. 9 Effect of fuel hydrogen content on J79 combustor inner-linerpeak temperature.

aRig data corrected to engine pressure and backside velocity.

SIMULATEDTAKEOFF

Fig. 10 Typical measured temperature distribution, F101 com-bustor.

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SEPT.-OCT. 1980 FUEL PROPERTY EFFECTS 221

TTi i i r

OUTER LINER3rd PANEL

I I i i 1 1 I "f

CXL

500

400

300

200

100

0

CALCULATED TEMPERATUREDISTRIBUTIONMAXIMUM-^AVERAGE-

MEASUREDTEMPERATURE

t SIMULATED TAKEOFFOPERATING CONDITIONS

^ 0 1 2 3 4AXIAL DISTANCE FROM COOLING HOLES, CM

Fig. 11 Typical measured and calculated temperature match, F101combustor outer liner, third panel.

600

500

400

O JP-4 FU^L B L E N b s ' ' ' 'D JP-8 FUEL BLENDS

- A NO. 2 DIESEL FUELFLAGGED SYMBOLS: BUILDUP NO. 1UNPEGGED SYMBOLS: BUILDUP NO. 2 & 3

RIG DATA CORRECTED TO ENGINE TAKEOFF CONDITIONS

+ 16 K

300 11 1512 13 14FUEL HYDROGEN CONTENT, WEIGHT PERCENT

Fig. 12 Effect of fuel hydrogen content on F101 combustor linerpeak temperature rise.

Table 5 Predicted effect of fuel hydrogen contenton combustor cyclic life

Fuel hydrogenwt.%14.514.013.012.0

J791.000.780.520.35

Predicted relativecombustor life

F1011.000.720.520.47

stoichiometric primary combustion zones. Although thesedata show that fuel hydrogen content strongly affects the linertemperature and life of both an older technology high-smokecombustor and an advanced-technology low-smoke com-bustor, it should not be assumed that these effects can begeneralized for all combustor designs. For example, it wasfound in the investigations described in Ref. 6 that, for ad-vanced low-emission staged combustor designs having verylean primary combustion zones, peak liner temperatures werevirtually independent of fuel hydrogen content over the rangetested (12.2-13.8%). Also, it should be noted that it may bepossible to somewhat reduce the fuel hydrogen content effecton J79- and Fl01-type combustor designs by modifying thecooling airflow distribution slightly.

Blazowski and Jackson7 developed a nondimensional linertemperature parameter for correlating previous combustordata involving such combustion systems at cruise operatingconditions. The parameter is:

T —T1 £,max l L.max, JP-4

^L.max, JP-4 ~~ T3

which represents the increase in liner temperature over thatobtained with the baseline (JP-4) fuel normalized by the linertemperature rise with the base fuel (JP-4). Figure 13 comparesthe data obtained in this investigation to the data presented inRef. 7. As expected, the J79 data lie within the Ref. 7 databand. The F101 data, however, exhibit less sensitivity to fuelhydrogen content. This is because the F101 combustor, inorder to meet its long cyclic life requirements, was designed tooperate with a lower TLfinax-T3 differential than oldertechnology combustors.

+0.8 ——i————i———|—O J79 TEST DATA

- a F101 TEST DATA

+0.6

+0.4

+0.2

' -0.2-

0.4

DATA BAND,BLAZOWSKI & JACKSONREFERENCE 8(T56, J79, J78D, CJ805AND J57 TEST DATA)

J79

9 10 11 12 13 14 15 16 17

FUEL HYDROGEN CONTENT, WEIGHT PERCENT

Fig. 13 Effect of fuel hydrogen content on liner temperatureparameter at cruise conditions.

Combustor Cyclic Life PredictionsCombustor cyclic life predictions, based on the data in Figs.

9 and 12, are presented in Table 5. As shown, the impact offuel hydrogen content on cyclic life was found to besignificant and similar in percent for both combustors. Atleast within the range of tests, no other fuel property, such asaromatic structure or distillation range, was found to haveany significant impact on combustor life. These predictedimpacts on the cyclic life characteristics of the two com-bustors are generally similar. The similarity derives from thefact that, to a first approximation, cyclic life is dependent onthe differential between maximum liner temperature andcombustor inlet air temperature (TL max-T3). It should benoted that the liner cyclic life impacts shown in Table 5 in-volve percentage changes. On an absolute basis, with any fuelhydrogen content, the cyclic life capability of the F101combustor is considerably greater than that of the J79combustor.

ConclusionsPeak temperatures of the J79 and F101 engine combustor

liners increased significantly with reductions in fuel hydrogencontent. Other fuel properties, such as aromatic structure(predominantly monocyclic or dicyclic) and distillationtemperatures, did not affect liner temperatures.

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222 C.C. GLEASON AND D. W. BAHR J. ENERGY

Based upon these observed increases in liner temperature,the impacts on relative liner life associated with the use offuels with hydrogen contents of 14.5, 14.0, 13.0, and 12.0%are predicted to be 1.00, 0.78, 0.52, and 0.35 for the current-design J79 combustor and 1.00, 0.72, 0.52, and 0.47 for thecurrent-design F101 combustor. It may be possible to lessenthe impacts of reduced hydrogen content somewhat bymodifying the cooling airflow distributions.

The findings suggest that improved liner cooling designfeatures will be needed in most current-technology com-bustors to accommodate expected reductions in the hydrogencontent of future fuels.

AcknowledgmentsThe work described was conducted under Contracts

F33615-77-C-2042 and -2043. Sponsorship and guidance wereprovided by the Air Force Aero Propulsion Laboratory,Wright-Patterson Air Force Base, Ohio, under the technicaldirection of Thomas A. Jackson. Albert E. Meyer, DonaldW. Bahr, and Clifford C. Gleason served as the GeneralElectric Program Manager, Program Technical Manager, and

Principle Investigator, respectively. Milton J. Kenworthydirected the combustor heat transfer and life analyses.

ReferencesChurchill, A.V., Delaney, C.L., and Lander, H.R., "Future

Aviation Turbine Fuels," Journal of Aircraft, Vol. 15, Nov. 1978, pp.731-734.2Gleason, C.C., et al., "Evaluation of Fuel Character Effects onJ79 Engine Combustion System," AFAPL-TR-79-2015, June 1979.3Gleason, C.C., et al., "Evaluation of Fuel Character Effects onthe F101 Engine Combustion System," AFAPL-TR-79-2018, June1979.

4 Long well, J.P., ed., "Jet Aircraft Hydrocarbon FuelsTechnology," NASA CP-2033, Jan. 1978.

5Hodgson, F.N. and Tobias, J.D., "Analysis of Aircraft Fuels andRelated Materials," AFAPL-TR-2016, March 1979.6Gleason, C.C. and Bahr, D.W., "Experimental Clean CombustorProgram Alternate Fuels Addendum-Phase II Final Report," NASACR-134972, Jan. 1976.

7Blazowski, W.S. and Jackson, T.A., "Evaluation of Future JetFuel Combustion Characteristics," AFAPL-TR-77-93, July 1978.

From theAIAA Progress in Astronautics and Aeronautics Series

ALTERNATIVE HYDROCARBON FUELS:COMBUSTION AND CHEMICAL KINETICS—v. 62

A Project SQUID Workshop

Edited by Craig T. Bowman, Stanford Universityand J<j>rgen Birkeland, Department of Energy

The current generation of internal combustion engines is the result of an extended period of simultaneous evolution ofengines and fuels. During this period, the engine designer was relatively free to specify fuel properties to meet engine per-formance requirements, and the petroleum industry responded by producing fuels with the desired specifications. However,today's rising cost of petroleum, coupled with the realization that petroleum supplies will not be able to meet the long-termdemand, has stimulated an interest in alternative liquid fuels, particularly those that can be derived from coal. A widevariety of liquid fuels can be produced from coal, and from other hydrocarbon and carbohydrate sources as well, rangingfrom methanol to high molecular weight, low volatility oils. This volume is based on a set of original papers delivered at aspecial workshop called by the Department of Energy and the Department of Defense for the purpose of discussing theproblems of switching to fuels producible from such nonpetroleum sources for use in automotive engines, aircraft gasturbines, and stationary power plants. The authors were asked also to indicate how research in the areas of combustion, fuelchemistry, and chemical kinetics can be directed toward achieving a timely transition to such fuels, should it becomenecessary. Research scientists in those fields, as well as development engineers concerned with engines and power plants, willfind this volume a useful up-to-date analysis of the changing fuels picture.

463pp., 6x9illus., $20.00Mem., $35.00List

TO ORDER WRITE: Publications Dept., AIAA, 1290 Avenue of the Americas, New York, N. Y. 10019

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