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RESEARCH MEMORANDUM---

THE

.

EFFECT OF INITIAL RATE OF SUBSONIC DIFFUSION ON THE

STABLE SUBCRITICAL MASS-FLOW RANGE

OF A CONICAL SHOCK DIFFUSER

By J.C. Nettles

Lewis FlightPropulsionLaboratoryCleveland,Ohio

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NEME AND

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NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS

WASHINGTONJuly 22,1953

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NATmNAL -ORY cclMmmEEFCIRAERONAUTICS

RESEARCHMEMORANDUM

EmcT OF INITIALRATE OF SUBSONICDJJ?TUSIONON TBE STABLE

SUBCRITICALMASS-FLOWRANGE OF A CONICALSHOCKDIFFUSER

By J. C. Nettles

SUMMARY

Resultsare presentedof a systematicstudymade in the Lewis 8-by 6-footsupersonicwind tunnelto determinethe effectthat axea dis-tributionh the subsonicdiffusermight have on the stabilitysad over-all performance of conical-typesupersonicdiffusers. Drag,pressurerecovq, and mass flow are presentedfor five diffusersdesignedformsxinnmmm fluw at a Wch numberof 2.0. The diffusershad the samesupersoniccompressionbut differentinitialrates of subsonicdiffusion.

Reducingthe initialrate of subsonicdiffusionme effectiveinimprovingthe mass-flowrangethat couldbe achievedwithoutpulsation.The diffuserwith 3.5 hydraulicdiametersof zerodfffuslonlen@h atthe entranceto the subsonicdlffisercouldbe throttledfor a range of

s 46 percentof maximummass-flowratiowithoutoscillation.The inmr-porationof this zero diffusionIn the subsonicdiffuserhad littleifany effecton the critfcalpressurerecoveryat a Mch numberof 2.0

. and zeroangle of attack. The stablerange of the diffus= with3.5 hydraulicdiametersof stabilizinglengthhad a tendencyto improvewtth increasingangleof attackuntila criticalanglewas reached,atwhichpoint the stablermge “suddenlydecreasedto a value dust slightlybetterthan the compar~le diffuserwithoutstabilizinglength.

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Numerouseqerimentershave observedthe tendencyfor diffuserswith externslcompressionto enterinto a st+teof oscillationof boththe sustainedand randomtypewhen the ah flowingthroughthe diffuseris reducedbeluw the maximumvalue. Severaldlfferentconceptshavebeen offeredto eqlain thisphenmenon.

9 The ideaadvancedin reference1 is that the instabilityof super-sonicInletflow Is due to disturbancespropagatingupstreamin a decel-eratingflow emd beccmingtrappedin a regionof sonicflow,thus caus-

U ing a redistributioncm repositioningof .&e shockstructure. This

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2 W RM E53E26

authorconcludesthat the installationof a lengthof constant-areapassageat the entranceto the subsonicpartionof the diffuserwuuldallowthesedisturbancesto be absorbedwithoutcausinga reflectiondownstre~.

b reference2 experimentaldata =e presentedwhichshowthat theinsertionof a constant-areasectionin the throatof a convergent-dlvergentdiffuseroperatingat a Mach numb.qrof 1.65 stabilizedthedynwnicsystemand perndttedthe peak pressurerecovery to be obtained;

b reference3 it is pointedout that a discontinuityin velocityw occurdownsta’e?unof the titersectionof the Inletshockwaves,andthe presenceof th~svelocitydiscontinuitynear the innersurfaceof adiffusercowl actslike a flow separationin the subsonicdiffuserwhich can cause oscillationof the entireflow system. This wthorreasonsthat a cons-t-area passageat the..diffus==-cc @dpromotemixing and wouldtherefm?etendto reducethe effectof the velocIty discontinuity.References3 and 4 showM=t. a.cons~t-=ea see-_tion followingthe cuwl of a conical-typesupersonicdiffis= - effRc-tive in increasingthe steblesubcriticalmass-flowrange.

The stabilitycriterionsof the dyn=ic diffusersystemare studiedIn reference5 in termsof the slopeof the pressure-recoverymass-flowcharacteristicsand the ratio of the oscillating-aticolumnlengthtothe storagevolumeof the diffuserllkenedto a Helmholtzresonatcm.An increasein the oscillating-aticolumulengthis shownto @rovethe stdbility for a givenslupeof the pressure-recoverycurve. Theinstallationof a constant-areapassageat the entranceof the diffusershouldalso increasethe effectiveair columnlength.

!lYxLsrep=t presentsdata on the effeqtof va@ous ratesofsubsonic-diffuser=ea variationon the stql?lesubcriticalmass-flow~“””range of conicalsupersonicdiffhsersdesignedfor operationat a Machnumberof 2.0. Pressurerecoveryend ~ss floware presentedfor five”diffusershavingdifferentinitialratesof subsonicdimsion. Dragcoefficient=d diffuser-dischergeMach number=e includedin ordertoincreasethe utilityof the data. The conf@urationshave the swneover-alllength,combustion-chanibersize,and supersoniccompression.

The investigationwas conductedat the NAM Lewislaboratory.

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APPARATUSm PR(x!EDum

The aeneralarranmment of the modelsused in this Investimtion-—_–. — —-1s the seine as that used for a nuniberof investigationsh the Lewis8- by 6-footsupersonicwind tunnelfirstreportedIn reference6. Aschematicdiagramof the mtiel is shownh figure1. Mve configura-tionsof subsonic-diffuserareavarlatia shuwnIn figure2 wereachievedby two cowlsccmbl.nedwith variousfalrlngsof the centerbody.Half-angleconesof 25° were used for”all c=figurattonsexceptone Inwhichthe helf-anglewas increasedto 30°. Vez’iationsin the cone tipprojectionrelativeto the cowllip were madeby means of spacersinthe centerbodyat a stationwell tisidethe subsonicdiffuser. Thetwo cowlshad the samenominallip diameter~-.butone W.S c~tued f~a mcme rapidincreasein internel=ea than the other. The initialInternaldivergenceangleof the two cowlswas 8° and no, respectively.Both cowlswouldbe classifiedas havl.ngsharplips. The lengthfromthe cowllip to the base was 55.86inchesend w maximumdiameterwas8.125inchesfor all models.

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NACA RM E53E26 5

For conveniencein identificationof the variouscombinatias, acodenunbr has been assignedin the followingmanner: 25-43-12indi-cates,for example,a 25° cone heM-angle, a 43° spike-t%p-to-cowl-lfpangle,and a 12-percentarea changeper initisL hydraulicdiameter;25-43-0(3.5)indicatesthe same supersonicconfigurationas beforewithzerodiffusionfor 3.5 lengthsof I@raulic diameter.

Ah flow throughthe model was controlled by means of a movableplug at the base. The ratto of the mass of ati flowingtlnmughthemodel to the maximumthat couldflowbased on cowl entrance =ea wascomputedby means of the averageof eightstatIc pressuresmeasuredatstation36.7,the flow area at the plug, and Isentropicrelationships.Tot&l-pressurerecoverywas computedby the samemeans. All pressureswere measuredby means of the HACA DigitalAutcnuaticMultiplePressureRecord= .

AxisL farce,normalforce,and pitchingmcunentwere measuredbymeans of an internally mountedself-resoltig deflectionbalance.Remoteindicatim of the forceswas achievedby means of electricstialngagesand servo-amplifier-drivenself-balancingslideties.

The occwrence of mating fluwwas determinedby three sfnultan-eousn&hods. A miniaturevariable-reluctancepressuretransducerwaslocatedat station41 in the model emd connectedto one chemnelof arecordingosclllograph.The exlal-fcmcemeaeurlngcircuitof the bal-~ce was connectedto a secondchannelof the recordingoscilLograph.An observerwas stationedat the viewingscreenof the schllerena~ar-atus. It 1s believedthat the onsetof pulsingwas determinedconsist-entlywithinthe orderof 1 percentof maximummass-flowratio.

RESUUJ!S AND DISCUSSXOlf

Ih orderto establlsha referencefor deterndnlngthe effectof thevariousalterationsto the subsonicdiffuser,a basic filetdesignated25-4342 was Includedin the seriestivestigated.The l%percent areavariationper hydraulicdiametergivesthe same arderof subsonic-diffuserarea mtatlon as the familiar6° equivalentcontcaldiffuser.The performanceof the basic inlet,25-43-12,is presentedh fig-ure 3(a).

Becauseof the uncertaln~ of esttiting the growthof boundary_ With tight inducechokingin a constant-areasectionat theentranceto the subsmic diffuser,an titermedlateerea variationof3.65 percentper hydraulicdiameterwas investigatedin the 25-43-3.65mdel. The performanceof this modelwas takenfromreference7 andts presentedin figure3(b). Reducingthe initialaveragerate of

6 c~ MiCA RM E53E26.

subsonicareavariationfi?mn12 to 3.85 percent Improved the stablerangefrwl about8 to 17 percentat a Mach nuniberof 2.0 with littleIfany changein criticalpressurerecovery. The changeto the 25-43-3.85modelalso involvedchangingfrom the I.l”to the 8° cawl.

The diffusionrate was reducedto essentiallyzero for 3.5 hydrau-lic diametersin the 25-43-0(3.5)inlet. The physicalarea of thissectiau,designatedthe stdblllzinglength,was allxnmdto divergeatthe rate of about1.0 percentper b@raullc diameterin order to com-pensatescmewhatfor the growthof boundarylayer. The perfarmance ofthe 25-43-0(3.5)diffuserIs presentedin figure3(c]. The stablemass-flowrangewas 46 percentfor this diffuserat a Mach nuniber of 2.0.The peak pressurerecoveryfor a Mach numberof 2 occurredat criticalmass-flowratioand was 0.845.

Two configurationshaving1 and 2 hydraulicdiametersof sta-bilizinglength,respectively,were Investigatedin orderto establishthe mlnlmumrequtiementsof thismethodof stablllzlng the Inlet. Thex=f~ ce of the 25-43-O(1)and the 25-43-O(2)Inletsis presentedin figure4.

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The effectof the stabilizinglamP

on the minimumstablemass-flowratio Is mmmr Ized In figure5(a . The bESiC diffuserachievedan 8-percent stablemass-fluwrangeat a Mach nuziberof 2.0. The alter-ationto the centerbodyto prtide 1 bydraulic dlamew of stabili-zinglengthresultedIn a reductlcmof the minimumstablemass-flowratioposstble. Ih fact,the 25-43-O(1)difftaserhad essentiallyno

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subcritlcsJmass-flw rangeat a Mach number of 2. A furtheraltma-tlon of the centerbodyto ~ovlde 2 hydraulicdiametersof stabilizing elen@h had a favorableInfluenceon the flow and permitteda mass-flow-ratiorange of 11 percentwithoutpulsationat a Mach numberof 2.0.The resultsof this studyindicatethat a minimum of 2.25hydraulic

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diametersof stdhilizinglengthis reqplredto achievethe same skblemass-flowrangeas the diffuserwith the 3.85 LWea verlationrate.

Th6 effectof increasingthe stabilizinglengthIndicatedthe sametrendat a Mach numberof 1.8 as at 2.0 with the one exceptionthat thealterationfor the 25-43-O(Z]diffuserIncreasedthe mass-flowregula-tion range slightlyat a Mach nmber of 1.8 ratherthen decreasingtheregulationrangeas was observedfor a Mach mndberof 2.0. The maximummass-flowratiofor all the diffusersdruppedto 0.93 at a Mach mnnber

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of 1.8 becausethe conewas positionedfor the oblfqpeshockto inter-sect the cowl lip at a Mmh nwiberof 2.0. u the inletswere stable -- —-_throughoutthe mass-fluurarq at a Mach nuuiberof 1.5, and thereforethe minimummass-flowratio indicatedon the curvesIs arbitrary.

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HA(2ARM E53E26 H#EBmm& 7

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The additionof the stabilizinglengthat the entranceto the sub-sonicdiffusermightbe ~ected to influencethe subcriticaltote&

. pressurerecoveryin two ways. The pressurerecoverycouldbe reducedbecauseof the additionalfrictionlossesincurredat a sectionin thedlffiserwhere the flowMach nwibersare relativelyhi@. The pressurerecoverymightbe increasedbecauseof the favorableeffecton diffuserefficiencythat the stabilizinglengthmight achieveby reducingveloc-ity differenceswhich existin the enteringflaw. Figure5(b) indi-catesthe effect of stabilizinglengthon criticalpressurerecovery.

i At a Mach numberof 1.5 the Mach number enteringthe subsonicdiffuserIs relativelyhigh,and the additionof stabilizinglengthcausesagradualdeteriorationof pressurerecoveryfrom 0.95 for the 25-43-12diffuserto 0.90 for the 25-43-0(3.5)dtffusm. oAt a Mach numberof1.8 the enteringMach numberis decreased,end the effectis less pro-nounced. At a Mach numberof 2.0 the frictionand mixingeffectssreapparentlycounterb~cing and the pressurerecoveryis essentiallyunaffectedby changesin stabilizinglength.

~ ader to investigatethe effectthat the presenceof the vortexsheetnear the innersurfaceof the cuwlmighthave on the stablemass-flowrange,the cone was movedby smallincrementsto place the obliqueshockslightlyupstream,intersecting,and slightlyInsideof the cowllip. This techniquegivessiguificemtdifferencesin the positionofthe vortexsheetrelativeto the cowl lip for mass-flowratiosnearunity. The performmmesat a Maoh numberof 2.0 for the 25-42-12

* 25-43-12,and the 25-4442 diffusersare presentedin figures6(a~, (b),and (c),respectively.Figures7(a), (b),and (c)presentthe per-formancedata at a Mach nuniberof 2.0 for smallmovaents of the oblique

. shockfor the 25-42-0(3.5),25-43-0(3.5),and the 25-44-0(3.5)dfffusers,respectively.Figure8 summerizesthe effectof oblique-shockpositionon the minimumstablemass-flowratioat q Mach numberof 2.0. Valuesof cowl-positionratioless than 1 indicatethat the InletIs spillingmass flow for criticalconditionsemd that the vortexsheetfrom theshockintersectionis externalto the cowl at supercritlcalcondlti.ons.Valuesof cowl-positionratiogreaterthan 1 indicatethat the obliqueshockis enteringthe cowl for criticalconditimm and thereforeforsteadyflow the vortexsheetis alwaysinsidethe cowl. The diffuserswith12-percentarea veriationwere relativelyinsensitiveto sma12chsmgesin spikeposition. The diffuserswith 3.5 hydraulicdiametersof sta-bilizinglengthwere merkedlyaffectedby the emalLmovementof theobliqueshock. Movingthe obllqueshockfrom insidethe cowl to a cowl-positiohratio of 0.978resultedin a changeIn minimumstablemassflow from 0.45 to 0.79. The full simificance of the sensitivityof

. the 0(3.5) diffusersto oblique-shockpositioncsanotbe readilyevel-uated b view of the fact that the inletwith the 12-percentdiffuserdid not protideany correlationbetweenthe positionof the vortex

. sheetrelativeto the cowl llp and the stablemass-flowrange. The

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8 EACARM E53E26

totallineartravelof the spikeindicatedby the changein the cowl-●

positionratio of figure8 iEI*3.5 percentfrcm the designposition.—

Therefae it is apparentthat a diffusercontrolsystemwhichacts to _ .positionthe conemust have a preciseactionif pulsationIs to be..-avoided. .—..- .

observationsof the schlierenpatternsduringthe testingof the12-percentdiffusers indicatedthat the llmit of stablemass flow ofthesediffuserswas, at least in part,due to separationof the fluw onthe cone surface. b orderto investigatethisphenomenonfurther,the 8cone angle of the 12-percentdiffhser was alteredto the configuration =designated30-4d-12. The performanceof the diffuserwith the alteredcone angle is presentedIn figure9. The 30-48-12configuratlahad aI.&percentstablemass-fluwratiorangeat a Mach numberof 2.0,whichcmpsres with 5 percentfor the 25-42-12ccmflguration.The reductionIn cone surfaceMach nuniberachievedby changingthe ccmehalf-anglewas not sufficientto elimluate separation.

—=The changeIn cone angle

resultedin a reductionof criticalpressurerecoveryfrom0.86 to 0.84.

The performanceof d.1 the inletconfiguraticmswas Investigatedup to a 9° an~e of attack. Figure10 is a summaryplot of the minimumstablemass fluw for variousanglesof attack. The 25-43-O(1)diffuserhad essentiallyno subcriticalmass-flowrangeat any sagleof attack.The curvefor this diffuserrepresentsthe trendof the variationofmaximummass flowwith angleof attackfor all the diffusers.The v?m?-iationof the minimumstablemass-flowratioof the 25-43-12diffuserwas scmwwhaterraticwith changingangleof attack. m general,thisdiffusertendedto oscillateat aboutthe samevalueof absolutemassflow at all saglesof attack. The 25-43-O(2)inletalso consistentlybegan oscillatingat a ~ticulsr mass-flawvaluefor all anglesofattack. h catrast the 30-48-12di.ffus=had essentiallyconstantstablemass-flowrangethroughoutthe angleof attackinvestigated.The25-43-0(3.5)diffuserdispl~ed a radicallydifferenttrend from theotherdiffusersinvestigated.The mass-flowregulaticmrange of thisdiffuseris aboutconstantup to 3.5°,at whichanglethe regulationragge suddenlydecreasedto a valuejust sl@lrtlybetterthan the other25 diffusers. The effectof smallmovementof the cone tip positionpersistedthroughoutthe angle-of-attadkrange. Far the 25-44-0(3.5]diffuserthe stabilizedperformance was maintainedto abouta 5° angleof attack. Ih the angle-of-attackrangefrcnn5° to 6°, the minlmmnstablemass flow achieveddependedon whichdirectionthe testpointswere approached~ as is indicatedby the dlsctitinuousfom of the curve.

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h general,the experimentaldata indicatesthatr~ucing the rateof diffusionat the entrancetb the subsonicportionof an externalcompressionsupersonicinletdid permitvariousdegreesof stablesub-criticalopera.tion. I?oneof the ww?iousthearetlcalconceptsis

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IiACARM E53E26 9

.sufficientlypreciseto pca’mita rationaltreatmentof the effectofstabilizinglengthon the inletfluwwithout~erimentd data. The

. presenceof separationfrom the cone surfaceh -Ious amountswasobservedto have,an inportsntbeartigon the range of stablemass fluwthat couldbe achieved. The relationbetweenthe mechanismof separ-ationand the functionof the stabiltzlmglengthis not as yet fullyunderstood.

SUMMARY OF RESUUl?S

The effectof variousrates of pubqonic-diffuserarea miation onthe stablesubcriticalmass-flowrange of 25° half-angleconicalsuper-scmlcdiffusersdesignedfor operationat a Mach numberof 2.0 can besummarizedas follows:

1. Reducingthe initialrate of subsonicdiffusionper hydraulicdiameterprogressively&cm 12 to 3.85 to O percentwas effectiveInimprovingthe variationof mass flow that couldbe achievedwithoutpulsation. VariationIn lengthof the zero diffusionsection indicatedthat at a Mach nuniberof 2.0 and zeroangleof attack1 hydraulicdiamet~ of stabilizinglengthactuallyreducedthe s~ble mass-flowrange. The additionof stabtllzinglengthgreaterthan 1 hydraulicdiameterprogressivelyImprovedthe stablemass-flowregulationrange.The diffuserwith S.5 hydraulicdiametersof stabilizinglengthhad apulsation-freerange of 46,percent.*

2. The incorporationof stabilizinglengthh the subsonicdiffuserhad llttleIf any effecton the criticalpressurerecoveryat a Mach.number of 2.0 and zero angle of attack. The effectof the stablllztiglengthon the pressurerecoveryof the Mach nuniber2.0 desfgnwas pro-nouncedat a Mach numberof 1.5. The criticalpressurerecoveryofthe inletwith 3.5 hydraulicdlazuetersof stabilizinglangthwas 0.90at a Mach numberof 1.5,which compareswith 0.95 for the diffuserwfth-out stabilizinglength.

5. The stablemass-flowrange of the difftaserwith 3.5 hydraulicdismetersof stabilizinglengthwas very sensitiveto small@emges inconeposition. At a I@ch nuniberof 2.0 and zeroangleof attack,movingthe obliqueshockfrom slightlyInsidethe cowl lip to slightlyoutsidechangedthe minlnnnnstablemass-flowratio frOIJI0.49 to 0.79.

4. The stable mass-flow ramge for the diffhserwith no Etabilizhglengthwas 8 p~cent at a Mach

- Iimreaslngthe cone h&lf-angleflowrange to 15 percent. Thereductionof criticalpressure

n=ber of 2.0 end zeroangleof attack.-fhcun25° to 30° increased,thsstablemass-chdngetn crme singleresultedin arecoveryfrcnn0.86 to 0.84.

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10 ~EmwK N/WARM E53E26

5. The steblerange of the diffuserwith 3.5 hydraulic diametersof stabilizinglen@h had a tendencyto improvewith increasingangleof attackuntila criticalanglewas reached,at-whichpointthe stablerangesuddenlydecreasedto a value$mt slightlybetterthan the com~pea?ablediffuserwithoutstabilizinglength. The criticalan@e ofattackwas 3.5°at a Mach numberof 2.0 for the coneposition whichplacedthe obliqueon the cowl lip. - —

Lewis Flight PropulsionIaboratcmy

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—- .3 “-lIatf&alAd-tisoryCommittee?cm Aeronautics

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Cleveland,‘bhlo,May 3, 1953

REFERENCES

Hantrowitz,Arthur: The Farmatim and Stabilityof IbrmalShockWaves h ChemnelFlum. NACA TN 1225,1947.

~tt , D-quis D., and bCZSk, HenryR.: Am investigationofConvergent-DivergentDiffusersat Mach lbibers1.65. NACARME!XX07, 1951. {SupersedesNACARM E6K21.)

Ferrl,Antonio,and Rucci,LoutsM. : we Origin of AerodynamicEmtability of Supersonicblets at SubcriticalConditions.NACARM L50H30,1951. .B

Dailey,C. L.: Diffuserbstability in SubcriticalOperation.hiV. southern Calif.,Sept.26, 1950. --

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Sterbentz,WilliamH., and Evvard,John C.: criterionsfor *e-dictionand Controlof Ram-JetFluwPulsations.IIACAFtME51C27,1951.

Esenweti,wed T., and Valerino,AMred S.: Farceand PressureCharacteristicsfor a Seriesof I?osehlets at Mach Numbersfrcan1.59 to 1.99. I - Conical-Spike All-External Compression Jhletwith SubsonicCuwlLip. NACARM E5W26, 1951.

Beke,Andrew,and AXlen,J. L.: Force~d -essure-RecoveryChar-acteristicsof a Conic&l-~e Nose hlet

%eratlng at I&ch IWnbers

of 1.6 to 2.0 and at Anglesof Attackto 9 . NAM RM E52130,1952.

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NACA RM E53E26 17

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Ri?ee-etream Maohnumber,~

Tailed a~bols lndi-oate pulsYng

..0

.8L

.6

.4

.2

H+

o

.4

.2

0.2 .4 .6 .8 1.0

Mem-flowratio, IUJW

(b)Twohydreulio diameters;mode123-43-0(2).

Figure4. - Conoluded. (%eraoteristlosof dlfYuEerwith zero diff’uetanZero angle of attaok.

2.6 4wwsmmw - tiCA IM E5fi26

liwe-EitreamG?itioalmass-Maoh number, flow mtio,

MO (q’/@alt .

— 2.0 1.00—.—

1.01.8 .93

\.8

\

\

.6\

\’

.4 \

1

.2

(a)Minimum stablemass-flowratio.

1.0 Free-streamMaohnumber,bio

4) 4k 2.0: 1.8

r ~ —[ ]— 0 1.5.9 ‘ )

(w < \

.8.0 1 2 3 -- 4

Stablllzlng length,De

.—

.-.

---——

.

.-

.—

N

~lb

—

.

.—

—

—

.—*..- —

(b) Critioalpressurereoovery. ‘- .

YQure 5. - I!Heot of OtabillZinglength. zero angle of attaok.

—

w====’ ““” .-,.

!+.5

.4

8

.8 .8 1,0 .8 1.0 1.2 .6 .8 1.0I&lOw nxtio, mJm~

(a~)uP’trDE&2uPPke po9iMal; (b)!gyg B’&*u poaitial; (o)gygmJyi.b po,ith;-. --m -.

-6. - Qmuotmiutiom or lz-peromt diffuaa, m’ee-strum Mnoh nlmllem,2.0; Z6ro angln or Lit&ok.

II

. .

wild uyDbOlm imi.lute timing

.9

-1k- -M p 9 b* @- - -g

/ 4 h

- - -

).7 dw

c

00

.5

.4

.2

s + -

0 .,

.4

.2

.4 .8 .8 1.0 .4 1.0 .414M8.AW Utio;an&

.6 .6 1.0..

(a~mL~4*50aiti.: (b~~ign&i,yitirn;. . (“!oal’%s-af~ .-tin’

m 7. “- ClwMtditiom 0? s8r0-lna-OMt dilYuBar. --Btrum Iac& &, 2.0; m mQ21i d attaak.

.,, 1,;.. ,, i. .1. i I

1

!2

, . 1,

‘) Jllri ● !,..” 11-:, IIV6%i ””,

i,l””l .1 , ‘,! ,,il .,1:,,. .1”1 ~ ~,b, ,’.j.llfil!..,~l~ll .~~, , 1.41 1,

NAOARM E53E26

.

.

.

Model

o 25-42-U❑ 25-43-120 25-44-l.2v 25-42-0(3.5)P 25-43-0(3 .5)~ 25-44-0 (3;5)

cowl positionratio,f3z/cp

mPf38” - Effect of spikepositionm stablemass-flowrange.Free-stream Maoh number,2.0; zeroangle of attaok.

.

.

22.

NACA RM E53E26

.—

— -—

1.0

4IS

.4

0

.4

c!?

.2

0.

&ee-stream Maoh

Tailed s~bols indi---eate pulsl.ng

c)

4 .6 .8 100Mass-flow ratio, m4/~

Figure 9. - Clmraoterlmtioaof12-pbroentdiffuserwith30°oone.MMel 30-48-12;zero@e ofattaok.

,

NJm

s’

. .

—

.

.

—

.—.—

s . .

NACA RM E53E26

.

.

23

.

.

.8

.6

.4

Model

o 25-43-0(3.5)25-43-O(1)

: 25-43-O(2)A 25-43-120 25-44-0(3.5)n 30-48-I.2

<

\

\

\4b

- \

4+#* \Y I

o 2

Figure10. - Variatiauattaok. lhe-stream

8 10Ang:e of attaok~deg

of mtilmumstablemass-flowratiowith angle ofMaoh number,2.0.

.

.