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RESEARCHMEMORANDUM-”-

lGNITION=ENERGYREQUIREMENTS

TUBULARGOMBWSTOR

13yHarrq?tmH, Foster

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NATIONAL ADVISORY COMMITTEEFOR AERONAUTCS

WASHINGTONMamh27,1961

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.

.

NAC!ARME51A24

NATION~ADVISORYCOMMITTEEFORAERONAUTICS

RESWCH MEMORANDUM

IGNITION-ENERGYREQUEWMMTSINA SINGLETUBUIARCOMBUST~

By HsmptonH.Foster

SUMMARY

An investigationwasconductedtodetemminetheminimumsparkenergyrequiredforignitionina single“Wbularcon,tnzstor.Datawereobtainedat simulatedstaticsea-levelenginestartingconditionsfora widerangeofsmibienttemperatures,andalsofora rangeofaltitudeinlet-airpressuresandair-flowrates.Theinlet-airpressureandflowrates13mittiimitionarecomparedwiththoselimitingsteady-.-stateburninginthectiustor.Tkw=eimdicatetheeffectoffuelvolatility

A decreaseinazibienti%mperatureengine-crankingconditionsrequiredan0.022to about1.5joulesforignitionvolatilefuelti~estigatedjcomparablevolatilefuels.‘Thealtitudeignitioningthesparkenergy.abovethatofthe’

differentfuelswereusedtoon ignition.

from70°to -60°F at sea-levelincrease in sparkenergyfrominthecodmstorwiththeleasttrendswereobtainedwithmore13mitswereextendedlyincreas-cowentionalsystem.A spark

energyof-approxima~ely10 joulespersparkata sparkingrateof8 persecondgavesatisfactoryignitionat codmstor-inletconditionsclosetothesteady-stateburninglimitsofthecotiustorat lowandinter-mediateair-flowrates.Theignition-energyrequirementsatbothsea-levelandaltitudeconbuptor-inletconditionsgenerallydecreasedwithan increaseinfuelvolatility.

INTRODUCTION

ReMableignitionintheturbojetengineis importantat sea-levelconditionspriortotake-offoftheaircraft.It isparticularlytitalataltitudeforrestartingofm engineinwhichcombustionbl~-outhasoccurredandforthestartingofauxilisrythrustengines.Thealtitudestsrtingproblanhasbecomemorecriticalas thesteady-stateoperationallimitsoftheenginehaveincreased.

Fundamentalexperiments(reference1)haveshownthatdecreasesinpressurerequireverylargeincreasesin ignitionenergyjforexample,witha mixtureofpropaneandairunderidealconditionsforignition

2 NACARME5M24

(optimumcomposition,homogeneous,quiescentmixture)theignitionenergy -mustbe increasedfrom0.27to 34millijoules,orabout125times,fora reductioninpressurefromatmospheric(sealevel)to1/10atmosphe&ic l-lpressure(pressureat55,000-footaltitude).Largeincreasesin igni- Etionenergyarealsorequiredfordepartures’inthefuel-airratiotoeitherthelesmorrichsideofan optimumvaluenearstoichiometric.

-—

Theconditionsintheactualconbustorcanbefarfromtheidealconditionsforignitionrepresentedinreference1. TheturboJet-enginefuelisa liquidthatmustbe sprayedintotheconkmstorina pre-scribedpattern,atomized,vaporized,andsomixedwiththeairinthezoneofthesparkplugthata.favorablefuel-airratioisobtained, .despitetheveryshorttimeavailableasthefuel-airmixtureflows .pastthespark-plugelectrodes. -

ResearchisbeingconductedattheNACALewislaboratoryonfull-scaleenginesandonsinglecombustorsto determinetherelativeimpor-tanceoftheseveralfactorsaffectingignitionfitha viewto ~e~ngthealtitudestartinglimitsoftheengine.(references2 to4). Ref-erences2 and3 reportresultsoftheeffect’offuelvolatilityonthealtitudestartingUm.itsofa full-scaleturbojetengineandasingletubularcodmstor,resl?ecti~elY=Reference4 presentsresultsofan investigationconductedona full-scaleaxial-flowturboJetengine .. intheNACALewisaltitudewindtunnelto determinetheoperationalcharacteristicsofseveralignitionsystems(withconventionalsparkenergiesanddifferentspark-pluglocationsinthecotiustor)forarangeofsimulatedflightconditions.

—.-

-—.—

-.

Theinvestigationreportedhereinwasconductedto determinetheenergyrequirementsforignitionina singletubularconbustor.

.——The

followingdatawereobtainedwiththreeturbojetenginefuelsofdiffer-entvolatility:

1.Theignitionenergyrequirementssimulatingsea-levelenginecr@singforof70°to -60°l?.

2.Theignitionenergyrequirements

forcombustor-inletconditionsansmbienttemperaturerange

fora rangeofcoribustorinlet-airpressuresandflowratesat constantinlet-airandfueltemperatures.

3.Comparisonsofthec@ustor inlet-airpressuresandflowrateslimitingignitionwiththoselimitingsteady-stateburning.

.

*

L NAM tiE51A24

.

3

FUELS

.

Thefollowingthreefuelsof currentinterestforuseinturbojetengineswerechosenfortheignitionstudies:

1. JP-1(MIL-F-5616,NACAfuel48-306),a low-volatilityfuelwitha Reidvaporpressure.ofO - 0.2pound-persquareinch.

2. JP-3(MIL-F-5624,NACAfuel50-174)a high-volatilityfuel,witha Reidvaporpressureof6.5poundspersquareinch.

3.ModifiedJT-3-fuel(NACAfuel49-246)obtainedbyremovingvolatilecomponentsfroma MIL-F-5624stocktoadjusttheReidvaporpressuretoathismtiied

Analysescurvesof the

nominal1.0poundpers@are inch. (Inthisreport,fuelwillbereferredtoasthel-poundfuel.)

ofthethreefuelsaregivenintableI. Distillationthreefuelsarepresentedinfigure1.

APPARATUS

Cotiustor

A diagramofthesingle-codmstorinstallationisshowninfig-ure2. Airflowto theccmibustorwasmeasuredlya sqpare-edgedorificeplateinstalledaccordingtoASMEspecificationsandlocatedupstreamofal-lregulatingvalves.Theinlet-airtemperaturewasregulatedbytheuseofelectricheatersandrefrigeratedair. Thecodmstor-inletairquantitiesandpressureswerereguhtedbyremote-controlvalvesinthelaboratoryair-supplyandexhaustsystems.Instrumentationforindicat-ingtotalpressuresandtemperaturesat theinletandmust oftheccmibustorisdescribedinreference5.

A sectionthroughtheupstresmendoftheconibustorshowingtherelativepositionofthesparkplugandfuel-spraynozzleis showninfigure3. A variable-areafuel-spraynozzle(reference6)wasusedbecausea satisfactoryspraycouldbe obtatiedat considerablylowerfuel-airratiosthanwiththestandardsimplexnozzle.Theimcludedangleoftheconicalspray,as observedinstillair,variedfrom100oto 90°forthefuel-flowraue investigated.Thefuelsystem,describedincontrolsforratestothefuel.

reference3, include~a refrig~ationsystemwithsuitablere@latingtemperatureofthefueltotheburner.Fuelflowconimstorweremeasuredby rotameterscalibratedforeach

.

●

4

.

NACARME51A24 *

IgnitionSystem .

Theignitionsystemconsistedofa specialhigh-energypowersupplyandcontrolssothatthevoltage,condensercapacitance,andsparking gratecouldbe v“~ied.throughwidelimits,allowinga variationinsparkenergyfromseveralmillijoulesto about16 joules.Figure4 showsablockdiagramof$heessentialcircuitconfiguration.A standardaircraft-typesparkplugwasused.Becausethehighsparkmergyerodedtheelectrodepointsveryrapidly,thesparkingtimeforeachignitionstartwaslimitedto 30to 45 secondsandthesparkingratewasmaint-ained at 7 to 8 sparkspersecondexceptwhereotherwisenoted.Pre-liminarytestsindicatedthatignitionlimitswereunaffectedly .—increasingthesparkingratefrm”8to 45persecondat onemoderate(O.72 joule)constantsparkenergy.

Theenergywascalculatedas (reference7)

(1) .—

where

E energy,joules .

c.!capacitance,farads●

v voltage,volts

PROCEDURE .—

Thesea-levelignitiontestsw=.ecopductedat conditionssimu-latinga sea-leveleng~necrankingspeedofabout,9-percentnormalrated ““rpmfora simulatedambienttemperaturerangefrom70°to -60°F. Thecorrespondingcombustorinlet-airpressures,temp~atures,andflowrates(lb/sec/sqftbasedona combustormaximumcross-sectional - -areaof0.267sqft)areshowninfigure5. Fuelatthesimulatedtem-peraturewas&&nittedtothebui?nerby openingthethrottleslowlyuntil =ignitionwasobtained,allowinga maximumthe intervalofabout30 sec- .—

endsforignition.Theoccurrenceofi~itionwas@dicatedby a teii-peratureriseinthecombustor.Thecriterionforsatisfactoryignitionwasthattheflamefilltheconibustorandcontinueburningafterthesparkwasde-energized.

Priortothealtitudeignition@vestigation,thesteady-stateburninglimitsofthecombustorweredeterminedasabasisforjudgi~theignitionrequirementsoftheccmibustor.At conditions(-10°F .

“

— .--.

. inlet-airtemperatureand-40°F fuel-inlettemperature)representativeofinlettemperaturesfor.altitudeengine-windmi~ing,theminimumand

N maximumfuel-flawratesatwhichsteady-stateburningcouldbe obtatiedo weredeterminedfora rangeof inlet-airpressuresandflowrates.~“

Theprocedurein obtainingthealtitudeignitiondatawasto chwsea pressure,higherthantheburning-limitpressure,at eachair-flowrateandby trialto determinetheminimumsparkenergyrequiredforsatisfactoryignition.This”procedurewasrepeatedforsuccessivelylowerpressuresuntila limitingpressurewasreachedwhereignitionwasnotpossible,evenwithan energyof10 joulesperspark.Theinlet-ah andfueltemperaturesweremaintainedatthesamevaluesasinthedeterminationofthesteady-stateburninglimits.

Itwasdesiredto obtainignitionlhitswitha s@em typicalofcurrentpracticeinorderto comparetheselhitswiththoseobtainedwiththenonconventionalhigh-energysystemsinvestigated.Severalcon-ventionalturbojetignitionsystemsprovide’from0.016to 0.033joule”at sparkingratesfrom400to 800persecond.A nunberoftestswerethereforemadewiththeimitionenergysetat0.025jouleandthespsrkingrateattestapp=atlls)j. ignitionsystem.

.

200per;econdthissystemiS

IuiHJlxs

(the=xtiumrateperr&sibletiththereferredto asthellconventionalt*

ANDDISCUSSION

IgnitionatSea-LevelConditions

Theeffectofauibienttemperatureontheminimumsparkenerarequiredforsuccessfulcotius;orignitionat simulatedsea-hvelenginecrankingconditionsisshowninfigure6. Thesparkenergiesrequiredincreasedrapidlywitha decreaseinsnibienttemperattiefor -thethreetestfuels.Forexample,thel-poundfuelrequired0.007jouleforignitionat 27°F,butreqyired1.0jouleat -60°F,or an increaseof143to 1. Themostvolatilefuel,JP-3,requiredtheleastignitionenergyatthelowerambienttemperatures,whichisinagreementwiththetrendspresentedinreference3 withconstantsparkenergy.Thelowvolatilityfuel,JF-1,reqtiredthehighestignitionenergyandtheresultsweretheleastConsistent,as indi-catedbythescatterofthedataforthisfuel.WithJ_P-lfuel,therequiredener~ increasedfrom0.022to 1.5joulesasthesmibienttemperaturewasdecreasedfrcan70°to -6(3°F.

Theresultsshownarefora sparkingrateof8 persecond.At veryhighsparkingratessuchas areusedinconventionalignitionsystemsthesparkenergiesreqtiedwouldprobablybe somewhatlower,particu-larlyinthelowenergyrange.Thedifferencesinsparkenergyrequiredforthe3 fuelsmightalsobe qffectedbylargechangesinsparkingrate.

6 NACARME51A24 *

AltitudeSteady-StateBurningLhits .

Theresultsofthesteady-stateburning-13mitinvestigationareshowninfigure7 forthethreefuels.At anyfuel-airratio,stablecombustionmaybe”obtainedonlyat a pressureabovethelimitingpres- gsureindicatedby thecurve.Thegeneralshapesoftheburninglimitcurvesaresimilar.Theminimumpressureatwhichconibustionmaybemaintaineddecreaseswitha decreaseinair-flowrate.Thefuel-airratiorequiredforburningatminhumpressureswasrelativelyunaf-fectedby airflowexceptatverylowair-flowrates.Thedisplacementofthelowestair-flowcurve(0.37Xb/(sec)(sqft))to higherfuel-air —ratioscanbe attributedtopoorfuel-spraycharacteristicsattheattendantlowfuel-flowrates.

.By replacingthev~iable-areafuel

nozzlewitha smallernozzle(nominal4.5&l/hr at 100lb/sqin.noz-zlepressure)thatwouldproducea satisfactorysprayat lowerfuelflowrates,thecurvefor0.37poundpersecondpersquarefootwasshiftedto lowerfuel-airratioswithlittle‘significantchangeinthemimbmunpressureNt (fig.7(c)).Theminimumpressuresandthecorrespondingair-flowratesframfigure7 sreplottedinfigure8 tocomp~etheburningUmitsat optimumfuel-airratioforthethree

—

fuels.Thesecurvesrepresentthelimitsofsteady-stateburningand,—

hence,thelimitingair-flowratesandpressuresatwhichignitionispossible.Slightlylowerpressurelimitswereobtainedwiththemore

--

volatileJP-3fuel;however,thisdifferenceinlimitingpressurewas—

onlyabout.1.5inchesofmercury. .

AltitudeIgnition

Theminimumignition-energyrequirements,at optimumfuel-airratios,forthethreefuelsareshowninfi@re 9. WiththevolatileJP-3fuel(fig.9(a)),a largeincreasein spark-energyrequir~nts

—

accompaniesa decreaseincombustorpressureuntila limitingpressureisapproachedbelowwhichignitioncouldnotbe obtainedevenwith ._ ~veryhighsparkenergies.Alsoat constantc~ustor-inletpressure,an increaseinair-flawrates(orairvelocity)requiresan increasein sparkenergy.Thesametrendsmaybe obse&vedforthelessvolatilel-poundfuel(fig.9(b))exceptthatthecurveswouldprobablybecomeparallelto theenergy-scaleordinateathigherspsrkenergies.Dataforthelow-volatilityZP-1fuel”areshowninfigure9(c).ExceptionstotheregulartrendofignitionenergywithAirflow,whichwasobservedwiththemorevolatilefuels,arepvidentin figure9(c).Asinthecaseofthesea-leveligmitioninvestigation,ignitionwiththislow-volatilityfuelwaserraticandunpredictable.

.

.

NACARME51A24 7

.

Y12A

.

.

A crossplotoftheignition@ta offigure9 is showninfig-.ure10. Comhustorinlet-airpressureisplottedagainstair-flowrateforconstantsparkenergiesjtheburning-limitcurves(fig.8)”are“ticludedforcomparison.Anypointonan en&rgyMne representstheminhmmsparkenergyrequiredforignitionattheparticularpressureandair-flowcontition.WiththeJP-3andl-poundfue~ (figs.10(a)and(b)),an increasein sparkenergfrcrm0.025jouleto 10 joulesextendedthelhits ofignitionto conditionsapproachingtheburninglimitsoftheconibustor,particularlyat intermediateandlowair-flowrates.Itwouldappearthatonlyverysmallgainscouldbeexpectedforsparkenergiesgreaterthsa10 joulesforthesemorevolatilefuels.

Thedottedcurveinfigure10 showsignitionlimitsobtainedwiththe“conventional”system,0.025joulepersparkand200sparkspersecond.Theimprovementshowninfigure10(a)oftheconventional0.025-joulecurveoverthe0.025-joulecurveobtainedfromthedataoffigure8 isduetothehighersparkingrate(200persecond);however,inpreliminarytestswitha highersparkener~ (0.72joule),increas-ingthesparkingratefrom8 to45persecondhadlittleeffectonigni-tionlimits.Itmaybe surmisedthatignitionofsprayedcoldfuelisaidedwhensparkelectrodesbecomehotenoughtoproduceqpreciablevaporizationofthefueldropletsstrikingthem.For“thelow-e~ergy(O.025joule)case,theincreasein sparkingratemayhaveappreciablyincreasedthetemperatureofthesparkelectrodes,whereasforthehigherenergy(0.72joule)case,theelectrodetemperaturemayhavebeensufficientlyhighdvertherangeofsparkingratesinvestigated.

Withtheconventionalenergyof0.025joule,tgnitioncouldnotbe obtainedat as lowpressures(orhighair-flowrates)withthe

‘ l-poundfuelaswiththeJP-3fuel;howeyer,theresponseto increasesin energywasgreaterwiththel-poundfuel.Thisobservationispos-siblyindicativeofthenecessityforhighsparkenergiestovaporizefuelsincea sparkof1 jouleormoresuppliesa largeexcessof energy -overthatrequiredforignitionofidealmixturesatthepressureencountered(reference1).

Dataforthelowestvolatilityfuel,JP-1,arepresentedinfig-ure1O(C).Increasingthespark-energyfromtheconventional0.025jouleto 10 joulesallowedincreasesintheignitionlimitscom-parableto thoseobtainedwiththel-poundfuelathighandinter-mediateair-flowrates.At lowair-flowratestiththelowestvola-tilityfuel,theconstant-energycurvesshowan increaseinMtingpressurewitha decreaseinair-flowratej thisiscontrarytothe .trendsobservedwiththemorevolatilefuelsandisprobablydueto. insufficientvaporizedfuelinthevicinityofthesparkwhenthelowestvc?latilityfuelissprayedintoa low-velocityairstream.

.

w“””~-

8 NACARME51.A24 *

A comparisonoftheignitionlimitsofthe”ttieefie~ issh~ infigure11fora spqrkenergyof10 joules.Themorevolatilefuel(n-3)hasslightlylowerpressurei~ition.lmts t~ thel-po~dfuel.At intermediateair-flowrates,theignitionlimitsoftheleastvolatilefuel(JP-1)weresimilartothoseofthemorevolatilefuels;atlowandhighair-flowrates,however,theywereinferiortothoseofthemorevolatilefuels. ‘“, -“.

Thedifferencesintheboun&ies ofignitionandtheburninglimitcurvesindicatedinfigure10aresmallestattheintermediateair-flowratesforthelowestvolatilityfuelandattheintermediateandlowair-flowratesforthehighervolatilityfuels.Thelowerair-flowratesrepresent.therangeof cotitionsthatwouldprobablybe encoun-teredinattempted-enginestartsataltitudewindmillingconditions.The”&ctualoperationallimitsoftheturbojetenginewouldoccmatsomewhathigherpressuresthantheburningli@tsthathavebeenpre-sented,becausethecodmstormustnotonlysustaincombustionbutmustalsoproducesufficienttemperatureriseto operatetheengine.A sparkenergyof10 joules,therefore,appearstobe sufficientforignitioninthecombustoratmostengineoperatingconditions.Also,as showninfigure1.1,a sparkenergyof10 jouleswillprovideeqpallysatisfactoryignitionofbothlowandhighvolatilityfuelsovera widerangeofoperatingconditions.

Reproducibility

Thetailedpointsshowninfigures9(a)and9(b)representcheckdataobtainednotonlytoextend,theignition-l~tcurvesbutalsotoindicate,toa limitedextent,thereproducibilityoftheresults.Ingeneral,thereproducibilityimprovedwithan increaseinfuelvolatil-ityandwithan increaseinsparkenergy.SMlarly, ignitionwiththemorevolatile-fuelswasobtainedmoreconsistently,andina shortertimeintervalthanwiththelowervolatilityfuels.

SUMMARYOFRESULTS

Thefollowingresults,wereobtainedfroqan investigationof thespark+nergyrequirementsforignitionina singlettiularturbojet-.engineconibustoroperatedwiththreefuelsofdifferentvolatility..

1.Forignitionat simulatedsea-levelenginecrankingconditions,a decreaseinambienttemperaturefrom70°to -60°F requiredanincreasein sparkener~from0.022toabout1.5joulesforthelowest

.

l-lgN

... -— - . -

—-.

-..—.—

..—

A

—.

—.

volatilityfu~linvest~gated~comparabletrendsmorevolatilefuels.

~

wereobtainedwith **

.

2 NACARME51A.24 9

2.Thealtitudeiggitionlimitswereextendedhy increasingthesparkenergyabovethatoftheconventionalignitionsystem.A sparkenergyofapproximately10 joulespersparkata sparkingrateof”8 persecondgavesatisfactoryignitionat combustor-inletconditionsapproachingthesteady-stateburninglimitsoftheccxibustorat lowandintermediateair-flowrates.

3.Formostoftheconditionsinvestigatedthehighervolatilityfuelrequiredlessignitionenergythanthelowervolati~tyfuels.

LewisFlightPropulsionLaboratory,~

1.

2..

.3.

4.

5.

6.

7.

8.

NationalAd~isoryCommitteef& Aeronautics,Cleveland,Ohio.

REFERENCES

Scull,WilfredE.: RelationshipBetweenInfhanmablesandIgnitionSourcesinticraftEnvironments.NACATN 2227,1950.

Wilsted,H.D.,andArmstrong,J.C.: EffectofFuelVolatilityonAltitudeStsrtingLtits ofa TurbojetEngine.l?ACARME5~10,1950.

RaylejWsrrenD.,andDouglass,HowardW.: “InvestigationOfIgni-tionCharacteristicsofanAN-F-32andtwoAN-F-58aFuelsinSingleCan-TypeTurbojetC!onibustor.NACARME50H16a,1950.

Golladay,RichardL.,andBloomer,HarryE.: InvestigationofAlti-tudeStsrtingandAccelerationCharacteristicsofJ47TurbojetEngine.NACARME50G07,1950.

Dittrich,RalphT.;andJackson,JosephL.: AltitudePerformanceofAN-F-58FuelsinJ33-A-21SingleConibustor.NACARME8L24,1949.

Gold,Harold,andStraight,DavidM.: Gas-Turbine-EngineOperationwithVsriable-AreaFuelNozzles.NAC!ARME8D14,1948.

Swett,ClydeC.,Jr.: SparkIgnitionofFlowingGases.I - Energiesto IgnitePropane-AirMixturesinPressureRangeof2 to 4 InchesMercuryAbsolute.NACARME9E17,1949.

Gooding,RichardM.,andHopkins,RalphL.: TheDetonation ofAromaticsinPetroleumDistillates.PapersPresentedbeforeDiv.PetroleumCWm.,Am.Chem.Sot.(Chicago,IIJ.),Sept.9-13,2.946,pp.X51-141.

-.

10

TABLEI - FUELANALYSIS

ASTMdistillation,%?InitialboilingpointPercentevaporated

5102030 ‘4050607080.90

FinalboilingpointResidue,percentLoss,‘&rcent

Freezingpoint,OFAromatics,percentby volumeSilicaGela

Viscosity,centistokesat-40°F

BrominenumberReidvaporpressure,lb/sqin.Hydrogen-carbon..ratioHeatofccmibustion,Btu/lbSpecificgravityAcceleratedgum,mg/100mlAirjetresidue,mg/100mlSulfur,percentby weight

JT-1MIL-F-5616(I&C~el

340

350355360364367‘“375380384391402440;.1.0.1.0

<-76

15

9.20..

0-0.20.15418,5300.830

01

<0.02

aDetermine&bymodifiedmethodofreference8.

n-3MIL-F-5624(%7~el

114

1281381491601741882042313304395331.01.0-72

5.7

1.650.96.5

0.17218,8000.725------------------

NACARME51A24

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NACARME51A24

600

500

J% 400

.

.

2(X)

1000 20 40 60 80 100

Percentevaporated

Figure1. - Variationof distilhtiontemperaturewithpercentageevaporatadforthreefuels.

11

Fuel NACAfuel Reidvaporpressure 3(lb/sqin.) A

o m-l 48-306 0 - 0.2❑ l-poundfuel 49-246 1.0 -d ~-3 50-174 6.5

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Figure5. - Variationofair-flowparametersforsinglecotiustor.Simulatedenginespeed,9-percentnormalratedrpm;staticsea-levelconditions.

.

NACARMX51A24

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Figure6.-Effectof8mbientt~mpera~ureonIgnitionorthreefuebofdifferentvolatilityatsImlatedenginecrankingspeedof9-percentnormlretedrW andstaticsea-levelcmdltions.

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NACARME51.AZ4 17

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.-

F&ure 7. - Effectofair-flowrateandpressureonburninglimitsofsingletubularcombustor.Wet-air temperature,-10°F; inlet-fueltemperature,-40°F.

18 - NACARME51A24 .

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Figure7. - Continued.Effectofair-flowrateandpressureonburning~hits of singletubularcombustor.Inlet-airtemperate,-10°F;inlet-fueltemperature,-40°F.

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4 I I -0 .01 .02 .03 .04 .05 .06 .07

Fuel-airratio

(c)JP-1fuel(NMA fuel48-306).

Figure7. - Concluded.Effectofair-flowrateandpressureonburninglimitsofsingletubularconibustor.Wet-air temperature,-10°F; inlet-fueltemperature,-400F.

No

16

4

I

I-s /

o Fkl NACAfuel Reid va~❑

. n /(%~o%. )-{ /

A o Jp-1 48-306 0- 0.2

H d ❑ l-pound fuel 49-246 1.0”u & (7P-3 50-174 6.5

NO b# y

I I I I Io

I1.0 2.0 3.0 4.0 5.0 6.0 7.0

1

Air flow, lb/(sec)(sqft)

Figure 8. - Effect of fuel volatility,air-flowrate, andof single tubular combuetor.

~essm m*- hitsInlet+ir temperature,-10 F; inlet-fuel~ture,

-40° F. E~

E

Tecx. *

.

.-lmoal

.

NAM RME51A24

‘“””r

1=1.10.CO8.00

6.00

4.m

F2.0”

r

“LOQL‘O+

B.60.37

.74.40

.20

A

.m

.08

.06

.04

.02

.01. E4

Airhow. 6.40

7

\

\

Lo

1

\

>

\ i

\Y

o

\

\ K

e

=4$2=12 M 20 24

21

.

.

Combustor-W”ettotalpressure,in.Hg abs..

(a)JP-3fuel(NAC!Afuel50-174).

Figure9. - Ef’f~ctof air-flowrateandpressureon sparkenergyrequiredforignitionh singletubulsxcombustor.Inlet-airtemperature,-10°F; inlet-fuelterupmture,-40°F.

—

22 NACARME51.A24

20.00Y \ IAirflow

(lb/(sec)(sqft))3.74

10.00 Ak8.00

6.00

4.CO

2.00

1.30

1.004

.80

.60

I A \zl I \Y I I

.09 \ 1 n \ u

.06 9

.04

.02

=S$=.014 a 12 16 20 24

Canbustor-inlettotalpressure,h. Eg abs.

(b)l-pcundfuel(NAcAfuel49-246).,

Figure9. - Continued.Effeetofair-flowrateand~essureenergyrequiredforignitionin singletubularccmibustor.temperature,-10°F} inlet-fueltemperature,-4ooF.

28

on sparkInlet-air

.

●

.—

.

-“

NACARME51.A24

20.00I I I II I Air‘flov I

(lb/(sec)(sqft)) ~.a1.87 2.80 1.30 .74

10.00 i \8.00 \\ t3.74 \ T

6.00-

4.00

2.00

1.00

~.80 \ L

\.60

i$ .40’

aA

& .20-

.10“

.08-

.06-

I 38 u s 16 20 24 28

Ccm.kmstor-inlettotalpressurejh. Hg abs.

(c) JP-1 fuel (NACAfuel 48-306).

Figure9. - Ccncluded.Effectofair-flowrateandpressureon sparkenergyrequiredf’orignitionin singletubularccsnbustor. Inlet-airtemperature,-10°Fj inlet -fueltemperature,-40°F.

24 NACARMx53.x24 a

.

24:.

.m .025% 20 /

B

i

~ ~~

K i

j

: 12 /

a// BurningMmlts

i // “ p “

18 [i

~

A‘p-- ‘

% 1.0 2.0 3.0 4.0 5.0 6.0 7.0’AirflOW,@(sec)(sQ ft)

(a) JP-3 fuel (NAcAfid50-174).

Figure10.- ComparisonofboundariesofignitionUdburnhg limitsof singletubularcombuator.Inlet-airtemperat,m,-10°Fj inlet-fueltqrature,-@ F.

,j . .

._.-

.7-,. F-..

—..

,.+.●

✎✌mr.

,.=

.

NACARME51A24.

25

(b)l-poundfuel(l?ACAfue149-246).

Fl~e 10.- Continued.Comparisonof boundariesof ignitionsndburninglimitsof

:4&F:*- C-ytor.Inlet-airtemperature,-10°Fj inlet-fuelt~rattie,

NACARM E51A24

.

(c)JT-1fuel(NACAfuel48-306).

—

--

.-

.-L--.:*

.

.b

—

Figure10.- Concluded. Ccqpmisonofboundariesofignitionandburnfngllmitsofsinletubularcombustor.

~ Inlet-airtemperature,-1ooFjitiet-fieltemperature}-40F.

.

.

.

0

\0

Igdt ion~

0/

.#

\ / -

Ho Igol.tion

\ ~ <=-,/

~ II

.5 ~“ Fuel FfJWAfkel Reid wapor

(K/:?%. )/ — JP-1 46-X6 o - 0.2

/ ‘ ---- l-pound fuel 49-246/

1.0—-— J-P-3 50-174 6.5

I I I I I I , 1 1 1 1 1 I1.0 2.0 5.0 6.0 7*O

Air :;$ lb/(sec;& ft)

#&l

Figure Xl. - Ccmmwlson of igoitionllmlte h slngl.etubular combuatorfor three fuelsof ~f~ent volatility. 6park energy, 10 Joulesj spe.rldmgrate, 7 to 8 per seccndj

Me-t-air tempeoxture,-10° F; inlet-fueltempemture, -40° F.

NJ