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RM No. E8L16

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RESEARCH MEMORAND1.——

MINVESTIGATION OF CERA~C, GRAPHITE, AND CHROME -PLATED

GRAPHITE NOZZLES ON ROCKET ENGINE

By George R. ~ey and William G. Lidman

Lewis Flight Propulsion LaboratoryCleveland, Ohio

NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS

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. NACA RM NO. 36L16

Ei%lifiiglli4357a

. IwlmNAL AmIsaRY cOMMrrmE FOR LERONAUCS

RESEARCXmmmmg& ImEsTIuTIaT al?CERAMIc j GRAPmmzj m CHROME-FIW!ED

GRAPHITENOZZLESON ROCKETENGINE .

~ GeorgeR. IClnneyand !IilliemG. Lidmm

SUMMARY

A brief investigationwas conductedregardingthe use ofceramicmaterialfor rocketnozzlesand the effectivenessin pre-venti~ oxidationand erosionof graphitenozzlesby chrome-platingthe internalsurface. The investigationwas conductedon a1000-pound-thrustacid - anilinerocket. The estimted combustion-gas teqeraturesfor the runswere ~&mm 2000°to 2400°F. Nozzleswere mountedin a steelhousing,whichwas attachedto the ccm-Imstionchamber.

A ceramic,which containeda hi@ percentageof sillimsnite,was investigatedin the form of a Win-wall nozzle (approximately“/~ Q in. thick]backedwiti plasterof paris. The convergentsection

* of the nozzlecrackedduringan initialrum, but it was operatedasecondtimewithoutfurthercrackingor dsmge. A thin chromeplatingon the internalsurfaceof graphitenozzleswas effectivein

● preventingoxidatfonand erosion_&at occurredduringa run withunprotectedgraphite.

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‘Be use of ceramicsand otherrefmctory materialsfor rocket-engineconstructionis being investigatedat the NACA Lewislaboratory%ecausesuchmaterialsreduceheat transfer to the engine walls.Desirablepropertiesof mterials b be used me high strength,luwtilermlconductivity,hi@ heat capacity,high meltingpoint,andgoodresistanceto tihemmlshock,oxidation,end erosicm. lherearecemmice that satisfymost of theserequirementsbut have a lowresistanceto thermalshock. Some gradesof graphite have goodresistanceto thermalshockend otherdesiredpropertiesbut have alow resistance to oxidationend erosion. Describedherein iS aninvestigationof (1) the thermal-shockresislxmceof a ceramic

. rocketnozzlecontaininga high percentageof siIMmsnite, (2) theusefulnessof a ceramicnozzlecrackedduringpreviousoperation,and (5) tileeffectivenessin preventi~ oxidation-anderosionof

●Waphite nozzlesby chrome-platingthe internalsurface.

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AImRM’us AND PRcmDuRE

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Equipmnt f’roma10~-pomd-thrust take-offassistaotd -anilinerocketunitwas used for the investi~tion. We propellant&u&s, controlequipmnt, and engineasseniblywere munted m athruststand. me propellant-injectionsystemprovidedfor fourpairsof impingingjets;for the designacid - anilineratioof 1.5,the resultantdirectionof the impingingjetswas approximatelyaxial. For an acid - anilineratioof 3, however,the resultantdirectionof the @inging jetswas about9° inward. Zhe combustimchmiberwas 4 inchesin diameter- 13 incheslcng. Chroml-alumdthermocoupleswere presseda@nst the outersurfaceof the nozzlesat the throatposttim.

The operatingcmditims and the nozzlematerialsfor the fiverunsare listedin tableI. !lheceramicinvestigatedoontainedaMf$l percentageof stlUmnite and had an aluminum-oxideenriched@.aze. Zhe thin-wall(approximately3/8 in. thick)ceramicnozzlewas held in a plaster-af-parissupport,which couldbe insertedtitea steelhousingthatwas directlymountedon the rocketcozibustionchamber(fig.1). The graphitenozzleswero machinedfrom extzruded~phi~ r~s tith a diameterof 6 fiches. me constructionofthesenozzleswas suchthat they couldbe insertedin the samesteelhousingas usedfor the ceramicnozzle. The chrom plate on theinternalsurfaceof the nozzlesusedfor runs 4 end 5 was approxi-mately0.003inch Wick. !Iheinternaldimensionsof all the nozzlesusedfor the fiverunswere the sameas thosefor themtal nozzlesused on the take-offassistunits.

RESULTSAMODISCUSSION

me resultsof tie nozzle-material.investi~tionere presentedin tableI. The tablealso showsestimatedcombustion-gastempera-tures,whichwere relativelylow (2000°to 2400°F) for rocketappli-cation. me trendsof the results,however,em significant.Theestimatedconibustion-gastemperatureswere law becausethe actualper-formanceof the rocketfor all the runs exceptrun 4 was onlyapprox-imately65 percentof the theoreticalperformance.!lheconibustion-gas temperaturesfor theserunswere estimatedat 45 percentof thetheoreticaltemperatures.Zhe low performanceof the runswasattributedto the conditionof the nitiicacid,whichhad been storedfor seveml yearsand was exposedto possiblewaterdilution. Thenitiicacid used for run 4 had been storedonlya shorttimeand theperformancefor thisrun was approxtmtely85 percentof the theo-reticalperformance.me combustion-gas temperature for thisrun wasestimted at 75 percentof the theoreticaltemperature.

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Ceremic nozzle.- me ceramicrocketnozzleafterrun 1 (16-secoperation,fuel-richmixture,estimated@s merature of’20000F) isshownin figure2. The craclchgin the convergentsecticm,whichwas causedby thermalshock~can be seen. No appreciableerosionat the throatend no crackingin the divergentsectionoccurred.The sameceramicnozzleafterrun 2 (10-secadditimal operation,near stoichiometricmMmre ratio,estimated-S temperature.of2400°F] is shownin figure3. No furthercrackingoccumed andthe conditionof the nozzle was littlechangedby the seed run.The nozzleapparentlywithstoodthe secotithermalshockwithoutfurtherdamage. me effectof furtieroperationon erosionorcrackingwas not investigated.Resultsof a similarnatures2-epresentedin reference1 where it was obsemed thata ceramicliningfor a conductionchemibercrackedbut did not fallapartduringoperation. ~ese resultsindicatethata ceramicrocket-nozzlelinercan be successfully opera&d afterit has crackedif it isproperlgsupported.

The ei?fectof crackingof the ceramicnozzleon the perfornkmceof the rocketwas not accuratelydetemined becausethe operatingconditionsof the engineend the cmpmdtion of the propellantswerenot accuratelycontrolled.The experimentsdo indicate,however,thatno largeeffeet on performnce resultedfrcm *9 crackingofthe nozzle. !Ilmextentto which crackingof the rocketnozzlaaffectsengineperformsncedependsupm the location ad the size ofthe cracks. &acks thatresultin an enl-.~gement~f the nozzlethroatwould o%viouslyreduceengineper.ormsnce.

I?roperties of ceramicmaterialsusuallyconsideredfor hQh-temperatureap@ication are strength,meltingpoint,thermalcon-ductivity,heat capacity,resistanceto fractureby thermalshock,end resistanceto erosionsmd oxidation. ~ the applicationofceramicsfor rocket-nozzleor conibustion-chenberliners, strengthof the materialis Un@ortant when the materialbackingthe cersldcis designedto withstaM the operatingpressures. Resistance totherml shockof ceramicmaterialsis dependentupon strength,coefficientof thermalexpansim, modulusof elasticityat fracture,thermalconductivity,end specificheat on a volum basis. Resist-ance to fractureby thermalshockis unnecessaryfor applicationsin whichpropersupportof the ceramicnozzleor the linerpreventsdamagethatwouldeffectperformance.Jh such cases,tie numberofpropertiesto be consideredin the selecticmof a ceramicliningisgreatlyreduced.

4 NACARM NO. E81J.6

C&aphitenozzles.-!lhegraphitenozzlewithoutsurfaceplatingis shownin figure4 afterrun 3 (17-seooperation,near Aoichio-metiicmixture-ratio)estimated“gastemperatureof 24000 l?).Thenozzlecrackedintofourpiecesof nearlyequalsizeand erosionat me cracksis considerable.The surfaceof the @?aphiteshowssignsof oxidationand erosion in other regions, especiallyin theconvergentsection. Zhe erosionobservednear the nozzleentrancebetweenoracksis probablycaused by an excessof oxygenat thoseplaces,whereasthis excess of oxygenhas apparentlydisappearedatthe throat. A locslexcessof oxyg~ couldresultfrom incompletemixingand combustionin the conibustionchaniber.

The graphitenozzlewith chrome-platedinternalsurface,whichwas used duringrun 4 (19-secoperation,fuel-richmixture,estimatedgas %eQeratureof 2200°I’),is shuwnin ffgme 5. The chrome-platedsurfacebecamepittedbut protectedthe gra@ite fmmoxidatton anderosion. No crackingof the nozzleoccuz’red.me @k spots,whichcan he seenon the chrcae-platedsurface,are pits that containedcarbondepositsfram combustion. ~

The ~phite nozzlewith chrome-platedinternalsurfaoe,whichwas usedfor run 5 (17-secoperation,nearstoichiometricmixtureratio,estimatedgas temperatureof 24000F)~ is dhownin figure6.!Ihenozzlecrackedat threeplacesand was held in shapeby themetalhousing. me chrome-platedsurfacewas slightlypittedbutprotected the graphitefrom oxidationand erosion. The chro~platingwas less pittedon thisnozzleaftera more severeoperationthanit was on the nozzleused in run 4.. The nozzleused for run 5probablyhad a betterplattngthanthe nozzleused for run 4.

An X-ray-diffrmtion enalysiswas made of the platedsurfaceof the nozzleafterrun 4 and carbon,chromium,and chromiumoxidewere present. !Ihediffractionresultsthus showedthat the bondbetweenthe graphiteand the chromiumwas physical;no chemicalreactiontookplacebetweenthe chromiumend the graphiteto formchromtumCarbide,whichwouM have provideda desirablechemicallybondedcoating. An examinationof the nozzlesshownby figures4end 5 WMcatad, however,that the physicallybondedchromeplatedid protectthe graphitefrom erosionand oxidation.

Me crackingof the graphiteduringruns 3 and 5 is attributedto the use of extrudedgraphite. As the resultof the extrusionprocess, the final graphite productis non-homogeneousand tendstobe stiiated. Thesestriaewould cause stresses in the graphitethatwould in turn causecracking‘andfracturewhen the graphiteis sub-~ectedto additionalstmesses. The use of moldedgraphitewilleliminateinitialstressesIn the material.

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.NACA RM NO. E81J.6 5

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A brief investigationwas conductedon a 1000-pound-thrustacid - -line rocketto investigateceramicand graphitenaterial.sfor rocket-nozzleconstruction.me operatingconditionsof therocketfor tie investigationresultedin relativelylow codmstion-gas temperatures(2000°to 2400°F) for rocketapplication.The&ends of the fol.lowingresults,however,are sigrdfioant.

1. Zhe convergentsectionof a suppmted,thin.-wall(approxi-?mtely3/8 in. tiick)ceramicnozzlecontaininga high percentageof sillimanitecrackedduringan operationof 16 secondsbut thedsmge was not appreciable.

2. !lhe ceramic nozzle,which crackedduringinitialoperation,was used for a secondoperationof 10 secondswithoutfurthercrackingor apparentdamageto the nozzle.

3. A thin chrcmeplatingon the internalsurfaceof a ~phitenozzlewas effectiveduringa 17-secondoperationin preventingoxidationSna erosion,which oocurredduringa similaroperationwtti an unprotectedgraphitenozzle.

Lewis Flight Propulsionlaboratory,NationalAdtisoryCommitteefor Aeronautics,

Cleveland,Ohio.

1. Woodwsrd,WillismH., and Bobrowslgy,A. R.: PreliminaryInvesti-gationof a Cersmic Lining for a ConibustionChsniberfor Gas-TurbineUse. NAC!AFM No. E7H20,1948.

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TAELEI—@TEWING ccumI!cIaK2 Am REmL!E3 oFHozzm—M!lY221AL~

m Fateriel oyma- adellt - combus- mruct Esti- lio5zle- (hmliticm afnozzl.es

tion fuel tion (lb) idea outer- Sfter opelatilm

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(see) tion-gas t%mp3la-?y%cl tmt&era- tip’e:t

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1 ~~ 16 2.5 285 944 2W2 Ilm cracked in con-

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2 Sme nozzle 10 3.2 255 911 24Cm -------- Samasaftirrunlel’terrlml

3 Qe@ite 11 3.3 250 w 2MXI 330 Cracked into four

newly equally Bizedpieces; surfaceccmbi especially atCracka

4 Obrc@-pL9ted 19 1.5 265 895 220Q 310 Ho Cra!Mng; Chrcmilegrapbi’kl plating potectca

surface from

Croeion; ChrCO?iuiusurface pitti

5 Chrcme-platal 17 3.3 263 MS 2400 140 &ackeLi into three

plw~ nemly equauy sized

pieces; chrcmplating p?otectedeurface ikm erosion;Eurface slil#ltlyDittea

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Ceramlo rocket xbxzle

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Pigum 1. - Methcdof adapting thin-wzllcmamio rdwt nmzlee ta cwburkian c)mmberof r.xketangine.-J

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.NACA RM No. E8L16

‘~Figure 2. - Ceremic rocketOperation,16 seconds;

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nozzle after run 1 showing conditionof convergentsection.fuel-richmixture; estimatedges temperature,2000° F.

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NACA EM No. E8L16

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Figure 3. - Ceramic rocket nozzle (same nozzle used for run 1) after run 2 showing comtion of convergentsection. Additional operation,10 seconds;near stoichiometricIIture ratio; estimatedgas temperature,2400° F.

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NACA RM No. E8L16 13

Figure 4. - Graphiterocket nozzle without surface pl@ng after run 3 showing surfaceconditionof convergentsection. Operation,17 seconds;neex stoichicmetricmixture;estimatedgas temperature,24M0 F.

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. NACA RM No. E8L16 15

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Figure 5. - Chrome-platedgraphiterocket nozzle after run 4 and removal of ccmbuationdepositB from convergentsection. Operation,19 seconds;fuel-richmixhrre; estimatedgas temperature,2200° F.

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NACA RM No. E8L16 17

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Figure 6. - Chrome-platedgraphiterocket nozzle after run 5 and removal of combustiondeposit from convergentsection. Operation,17 seconds;near stoichiometricmixtureratio; esthated gas temperature,2400° F.

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