REG NASA-CR-135307-1977 Aerodynamic performance of conventional and advanced design labyrinth seals with solid-smooth abradable and honeycomb lands.pdf

1、NASACR-135307EI)R9339_,:ISO_ POOR QUALIrYxii1978019484-011Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page72 LTSDOptimizedAdvancedSealConfiguration 10873 Comparisonof AdvancedSteppedSeal 109. Performancewith a ConventionalSteppedSeal- Clearance=

2、.025cm (.010in.)74 Comparisonof AdvancedSteppedSealPer- 110formancewith a ConventionalSteppedSeal-Clearance= .051cm (.020in.)75 Sketchof Full-Notch,Half-Notch,and 111No-NotchLandConfigurationsTested76 LandNotchEffecton theLeakageThrough 112theLTSDOptimumAdvancedSealClearance= .025cm (.010_ .)77 Land

3、NotchEffecton theLeakageThrough 113theLTSDOptimumAdvancedSealClearance= .051cm (.020in.)78 Effectof theNumberof Kniveson the 114 LeakageThroughthe LTSDOptimumAdvancedSealClearance= .025cm (.010in.)79 Effectof theNumberof kniveson the 115LeakageThroughtheLTSDOptimumAdvancedSealC1earat_ce= .051cm (.02

4、0In.)80 Effectof Distance-to-Contact(DTC)and 116Numberof Kniveson LeakageThroughtheOptimumAdvancedSealat a Clearance.051cm (.020in.)81 STLDOptimizedAdvancedSealConflguratlon 11782 Solid-Smooth Land of the Optimized 118AdvancedSeal for the 3D Rtg83 “Abradable A“ Land of the Or_tmtzed 119AdvancedSeal

5、for the 3D Rig i84 HoneycombLand of the Optimized 120AdvancedSeal for the 3D Rtg“ 85 LTSDRotor of he Optimized Advanced 121Seal for the 3D Rtgxttt1978019484-012Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page86 STLDRotorof theOptimizedAdvanced 12

6、2Sealforthe3D Rig87 FourKnifeLTSDOptimumAdvanced 123SealwithSolid-SmoothLand88 FourKnifeSTLDOptimumAdvanced 124Sealwith Solid-SmoothLand89 FourKnifeSTLDOptimumAdvanced 125Sealwith“Abradab!eA“ Land90 FourKnifeSTLDOptinumAdvanced 126Sealwith ._sgcm (.062in.)CellHoneycombLand91 Effectof FlowDirectionon

7、Optimized 127AdvancedSealPerformance92 Effectof Rotationon Optimized 128AdvancedSealPerformance93 Effe,.tof AbradableandHoneycomb 129Landson OptimizedAdvancedSealPerformance94 Non-ConstantPitchAdvancedSeal 13595 ActualSealRotorPowerVersus 139Seal InletPressurefor a FourKnlfeStraightSealQmCRIcSI,_/_L

8、 PAGE .:_,_ LOORQUALIT_xiv1978019484-013Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LISTOF TABLESTable Pagei Typical2D RigTestConditions. 152 Typical3D RigTestConditions. 163 Comparisonof SmoothandAbradableLands 48, Performanceat VariousOperating

9、Conditions.4 Effectof LandRoughnesson FourKnife 48Straight-ThroughLabyrinthSealPerformance.5 Effectof LandRoughnesson SingleKnife 49Straight-ThroughLabyrinthSealPerformance.6 “AbradableA“ PorosityandSurfaceRoughness 49Results.7 “AbradableB“ PorosityandSurfaceRoughness 50Results.8 Effectof Rotationon

10、 thePerformanceof Four 50 KnifeStraightSealsat a PressureRatio= 2.0witha SmoothLandandan AbradableLand.9 Comparisonof Solid-Smooth,Non-Grooved 61Abradable,andGroovedAbradableLandPer-formanceat .013cm (.005in.)Clearanceinthe2D TestRig.lO Comparisonof Solid-Smooth,Non-Grooved 61Abradable,andGroovedAbr

11、adableLandPer-formanceat .025cm (.OlOin.)Clearanceinthe2D TestRig.II Comparisonof Solid-Smooth,Non-Grooved 62Abradable,andGroovedAbradableLandPer-formanceat .051cm (.020in.)Clearanceinthe 2D TestRig.12 Effectof RubGroovingon LeakageUsinga Four 62KnifeStraightSealwith “AbradableA“ Land.13 Comparisono

12、f SmoothandHoneycombLandPerformanceat PressureRatiosof 2.0 and3.0. 7214 Effectof Rotationon thePerformanceof a Four 72 iklKnifeStraightSealat a PressureRatioof 2.0with a SmoothLandandHoneycombLand.XV1978019484-014Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr

13、om IHS-,-,-Table Page15 Comparison of Abrdable and HoneycombSeal Lands 73Performance with Solid Land at Pressure Ratio 2.016 Effectof Rotationon the Performanceof a Four 86KnifeStraightSealat a PressureRatio= 2.0.17 Comparisonat a PressureRatio= 2.0of a Honeycomb 86andan AbradableLandwithSolidLandSe

14、alPer-formanceStaticallyandDynamically.18 SpecificValuesof GeometricParametersInvesti- 130gatedinthe2D SealRig to OptimizeAdvancedSealPerformance.Ig Effectof LandNotchon AdvancedSealPerformance 131at a PressureRatioof 2.0.20 Summaryof AdvancedDesignLabyrinthSealDis- 131chargeCoefficientsat a Pressur

15、eRatioof 2.0.21 Summaryof RotationalEffectson Advanced 132SealPerformance.22 PerformanceComparisonof AbradableandHoneycomb 132Landswith a Solid-SmoothLandfortheAdvancedSealDesign.23 Comparisonof Non-ConstantGeometryTestResults 136at PU/PD= 2.0.24 Summaryof RotationalPowerAbsorptionforSmooth, 140Abra

16、dable,andHoneycombLandswith FourKnifeStraight-ThroughSealRotors.25 Comparisonof RotationalPowerAbsorptionas a 141Functionof Clearance,Pitch,andLandSurfaceina FourKnifeStraight-ThroughSeal. ,.26 Summaryof PerformanceImprovementFromUsinga 142HoneycombLandInsteadof a SmoothLandin aFourKnifeStraightSeal

17、for anAdvancedHighBypassRatioTurbofanEngir_.27 Summaryof RotationalPowerAbsorptionfora 142Smooth,Abradable,andHoneycombLandUsinga FourKnifeAdvancedLabyrinthSeal.xvi1978019484-015Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARYThe objectives of

18、 this program were to obtain additional knowledgeregarding the parameters that affect the performance of conventionallabyrinth seal configurations and to optimize the performance of anadvanced labyrinth seal.Rig testing was conducted to determine labyrinth air seal static anddynamic leakage performa

19、nce for solid-smooth, abradable, and honeycomblands using a conventional four knife straight-through seal and anadvanced seal design. The effects of land surface roughness, abradableland porosity, rub grooves, honeycomb cell size and depth, and rotationon seal performance were determined using the c

20、onventionalstraight-through seal. The effects of rotation on optimum seal knifepitch were also investigated. Selected geometric and aerodynamicparameters for an advanced seal design were evaluated to derive anoptimized performance configuration.Seal rotational energy requirements were also measured

21、to determine theinherent friction and pumping energy absorbed by the various seal knifeand land configurations tested in order to properly assess the net sealsystem performance level.The major results obtained in this program include the following:o An advanced labyrinth seal design was developed th

22、at reduced leakage26.9% compared to a conventional stepped seal.FLOW_ _“ _ _ % %“ 4114CONVENTIONALSTEPPED ADVANCEDDESIG_LABYRINTHSEAL tABYRINTH$_ALo Using a honeycomb land with the advanced seal increased leakage68.6%“ compared to the solid-smooth land.1978019484-016Provided by IHSNot for ResaleNo r

23、eproduction or networking permitted without license from IHS-,-,-Honeycomblandswere foundto reduceleakageupto 24%forconventionalstraight-throughlabyrinthseals.o Mediumsurfaceroughnesswas foundto reducestraight-throughseal leakageapproximately23% now-_relativeto a smoothlandat .013cm (.005in.)clearan

24、ceand5.0%at .051cm (.020in.)clearance.Greaterroughnessincreasedleakage.o Someabradablelandswerefoundto leak CONVENTIONALsubstantiallymore thana solid-smoothland. STRAIGHT-IHROUGHLABYRINTHSEALo Groovinga porousabradableseal landsignificantlyreducedleakagethroughthematerial.o Rotationreducedstraight-t

25、hroughsealleakageup to 10%forsmoothandabradablelands,but it hadnegligibleeffectwiththehoneycombIand.o Rotationdecreasedtheadvancedseal leakageapproximately6g forthesolid-smoothandabradablelands. However,thehoneycomb_.andexperienceda 6.4% leakageincreasewithrotationcomparedto thestaticperformance.o T

26、herotationalpowerabsorptionforsolid-smooth,abradable,andhoneycomblandsusinga conventionalfourknifestraight-throughsealshowedsmalldifferences.Thehoneycomblandhadthemaximumvaluewhichwas 5.7%higherthanthepowerabsorptionlevelot thesmoothIand.o The advancedsealrotationalpowerabsorptionforthesolid-smoothl

27、andisapproximatelythesameas thefourknifestraight-throughseal.o Rotationaleffectsdo not influencetheselectionof thesealknifeoptimumpitc_for a straight-throughseal.1978019484-017Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTRODUCTIONTechnologicala

28、dvancementsto achievehigherthermalandpropulsiveefficienciesforcurrentandadvancedaircraftgasturbineengineshavebeencharacterizedby significantincreasesinthe operatingcyclepressureratioandturbineinlettemperature.Thesetrendstypicallyc tse internalairseal leakageto increase. A higheroperatingtemperaturec

29、ausesgreaterdifferentialgrowth,frequentlyresultinginlargersealclearances.A highercyclepressureratiotendsto increaseseal leakage,even at the samesealclearancelevel. Thisflowincreasecanbe predictedfromthecompressibleflow relationship,PUAw =V_,- “UAs enginepressureratioincreases,pressure(PU)increasesmo

30、rerapidlythantemperature(Tu). The airflowparameter( ) increasesor remainsconstantifthe seal ischoked. Therefore,sealleakageincreaseson an approximatelyproportionalbasiswith increasesin sealinletpressure. Applyingthisrelationshipto a labyrinthseal ina gasturbine,assumingconstantengineairflow,as compr

31、essorpres:Jreratiois increased,the seal leakageincreasesas presentedinFigure1.Incorporatinga variablecycleengineapproachto futuredesignsmaalsoincreaseseal leakage. Normally,sealclearancesaresetto runastightas possibleat theenginemaximumtimeoperatingpoint. Theresultingclearancesat otherconditionsarea

32、cceptedsincetheyusually representa smallpercentageof theoperatingtime. However,thevariablecycleengine,throughdifferentialgrowthof hardwarecausedbytemperatureandmaterialdifferences,willcausetheaveragesealclearancetobe greaterand _hus,increaseleakage.Compensatingfor thecurrentstateof sealingtechnology

33、by attemptingto improveaerodynamiccomponentefficiencieshasnormallyresultedinlimitedpayoffsrelativeto time,cost,andeffortexpended. For anadvancedhighbypassratiogasturbineengine,Figure2 showsexamplesof the improvementsincompressorandturbinecomponentefficienciesrequiredto achievethe sameincreasein engi

34、neperformanceas areductionin turbinesealcomponentleakageof % of theengineairflow. A reductioninthe compressorrotorexitseal leakage _amounting_o1% of engineairflowwouldproducethesameresultsas acompre,sorefficiencyincreaseof 0.91%.Thebenefitsof improvedsealingeffectivenessareequallysignificantforfuelc

35、onservationorientedengines. Figure2 illustratesthepercentchangeinenginespecificfuelconsumptionfor a I% (ofgasgeneratorinletflow)reductionin seal leakage.1978019484-018Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CTherearealsodevelnpmentcostsavings

36、. The costtrade-offforimprovingsealperformancecomparedto improvingthecompressororturbinecomponentaerodynamicefficiencyis of significant |consideration.Extractingthe sameperformanceimprovementwithcompressoror turbineefficiencyimprovements,as comparedto sealleakageimproveme_its,is severaltimesmoreexpe

37、nsive. Typicalexamplesof thesecost trade-offsareshownin Figure3.Theforegoingtrendsandpayoffshave,therefore,addedincreasedemphasisto the immediateneedfor accelerateddevelopmentandcontinuedimprovementof gastJrbinesealingtechnologyinorderto reducecostlysealleakageto a m,.limum.Thisdevelopmentwillalsopr

38、ovidebetterandmorereliablecontroloversophisticatedcoolingcircuitsandpreventhighseal leakageflowsfromenteringcriticallocationsintheturbinegaspathwhichcanresultinconsiderablepenaltyfromthermalandmomentumlosses.Theobjectivesof improvedgas turbineperformanceandfuelsavingscanbe achievedby reducingthe lea

39、kagein currentsealswith designmodificationsandby developinghighefficiencylabyrinthsealconcepts. However,therearetechnologyvoidsinthedesig_,analysis,and“inservice“performanceof labyrinthsealsthatrequireddetailedinvestigationandunderstanding.Thisinformationisrequiredtoprovidedirectionfordesignimprovem

40、ents. DetroitDieselAllison o(DDA)hasbeen investigatingvariousaspectsof labyrinthsealperformanceunderin-housefundingandthroughtwocontractswith theNavalAirPropulsionTestCenter. Throughthe resultsof thesestudies,designconceptshavebeentestedthatsignificantlyreducesealleakageas comparedto a conventionals

41、eal. Theprogramthat is thesubjectofthisreportis an extensionandexpansionof experimentalworkaccomplishedat DDAoverthepastseveralyears.A diagramillustratingtheeffortsof thisprogramis presentedin _iFigure4. Theprogramwasdividedintotwobasictechnicaltasks. The Iwork involvedin TaskI includedexperimentall

42、ydetermininglabyrinthsealperformancefor a conventionalfourknifestraight-throughseal |Cusingabradableandhoneycomblands. Task IIwas directedtowardoptimizingan advancealabyrinthsealdesignandexploringtheeffectof |non-constantgeometryto reduceleakagein an advancedseal. _In TaskI,fourcommerciallyavailable

43、abradablelandmaterialsandthreehoneycombcell sizelandswereevaluatedforaerodynamicperformanceon the 2D testrig. Theeffectsof surfaceroughnessonsolidlands,porosityleakageon theabradablelands,andcelldepthonthehoneycomblandswere alsodeterminedusingthe 2D rig. Oneof theporousmaterialabradablelandswasgroov

44、edto simulatea rubconditionandretestedto determinetheeffecton leakage. A112D rig testinginthistaskwas accomplishedat threeclearancelevels:0.013cm (.005in.),0.025cm (.010in.),and0.051cm (.020in.).k4w_i9780i9484-0i9Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr

45、om IHS-,-,-Basedon theresultsof the2D rig tests,selectedabradableand honeycomblandswerefabricatedandtestedinthe3D rig up to 239m/s(785ft/sec)to investigatethe effectof rotationon sealleakag_andto determinetherotationalpowerabsorptiondifferencesofsolid-smooth,abradable,andhoneycomblands. Therotationa

46、lpowerdifferencecombinedwith seal leakagedifferencegavethe netsealsystemperformancechange.The abradablelandforthe3D rigwasgrooved1020to simulatea lightrub. Then therubgrooveswere extendedto 3600andretested. Testswereconductedstaticallyanddynamicallywiththerotorknivesforward,over,andbehindthegroovest

47、o determinethe leakageperformance.Also,in Task I,theeffectof rotationon theoptimumdesignpitchof astraight-throughsealwas investigatedwithsolid-smooth,abradable,andhoneycomblands. Fhreevaluesof pitchwere tested:.203cm (0.080in.),.279cm (0.110in.),and.356cm (0.140in.). Radialclearancesof 0.025cm (0.01

48、0in.)and0.051cm (0.020in.)were used. Testingwasdonostaticallyandatthreelevelsof rotationalvelocity:80 m/s (261ft/sec),159m/s (523ft/sec),and239n,/s(785ft/sec).InTask If,themajorgeometricsealparameters(knifepitch,knifeheight,knifeangle,andstepheight)wereexploredto optimizeanadvancedsealdesignin terms

49、of minimumleakage. Also,the useofnon-constantknifepitchwas investigatedas a techniqueto maximizetheinternalsealcavityturbulencebetweenknives. Theoptimizationofindividualknifedischargecoefficientswillresultinminimumsealleakage.The 2D airsealtestrigwas employedas an expedientandeconomicalmeansof conductingthe advancedseal