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DevelopmentsinenginebearingdesignF.A.MartinSomeoftheimportantrecentdevelopmentsinenginebearingdesigntechniquesarehighlighted.Theavailabilityofincreasedcomputingpowerhasenabledmorerealisticassumptionsaboutbearingconditionstobeconsideredtheseincludeoilfeedfeatures,oilfilmhistory,noncircularbearings,inertiaeffectsduetojournalcentremovement,improvedpredictionofmainbearingloads,flexiblehousingsandspecialbearings.Referencestotheseadvancesaremade,togetherwithillustrationsofhowtheyaffectpredictedbearingperformance.Experimentalevidenceisalsobeingobtained,whichhelpstoverifyandgiveconfidenceintheanalyticalpredictionsKeywordsjournalbearings,bearingsdesign,hydrodynamiclubrication,bearingstress,bearinghousings,oilgroovesEnginebearingperformanceisdependentuponmanyfactors,fromthemechanicalconfigurationoftheenginetothehydrodynamicsoftheoilfilm.Thispaperhighlightsthemoreimportantfactorstobeconsidered,andrelatesthemtorecentadvances,bothpublishedandunpublished,throughouttheworld.Thereviewattemptsnotjusttoreferencetheseadvances,buttoillustratehowtheyextendtheareasofperformanceprediction,experimentalverificationandthedesignofspecialbearings.Historically,theearliestattemptsatthedesignofdynamicallyloadedbearingswerebasedonmaximumallowablespecificloaddefinedasmaximumappliedloaddividedbyprojectedbearingarea,andthisisstillavaluableparameter.Withtheadventofgraphicalandnumericaltechniquescapableofsolvingahydrodynamicbearingmodel,albeitstillhighlysimplified,estimatesofminimumoilfilmthicknesscouldbemade,andusedasacomparatortojudgethelikelihoodofproblemsonnewengines.Acomprehensivestudyofthoseearlypredictivemethodscanbefoundinthe1967reviewpaperbyCampbelletalIasastudycasethisusedthebigendbearingofaRustonandHornsbyVEBMkIII600hp,600r/mindieselengine.NearlytwentypredictedandexperimentaljournalorbitsfromvarioussourceswerediscussedinthevolumeofI.Mech.E.proceedingswhichcontainedthatpaper,andthesamestudycaseisstillbeingusedbyworkersinthisfieldtodaypolarloaddiagram,Fig1acompletedata,Ref1.Ithasbeenusedinthisreviewtoillustratesomeofthesubsequentadvancesinpredictioncapabilities.Manyofthemajorassumptionsusedintheearlypredictionmethodswerecertainlynotrealistic,butwereusedasexpedientstoobtainamathematicalmodelwhichcouldbesolvedwiththelimitedcomputingcapabilitiesthenavailable.TheseassumptionsincludedcircularrigidbearingsandaperfectsupplyofisoviscousNewtonianoil.Inmanycasesthebearingsurfacewasassumedtobeuninterruptedbyoilfeedfeaturesinthedevelopedfilmpressureregionsand,externaltothebearing,thecalculationofthemainbearingloadstooknoaccountofthecrankshaftandcrankcasestiffnesses.OverthelastdecadeincreasesincomputingpowerhavemeantthatmanyofthoseearlyassumptionsarenolongerDepartmentofApplicationsEngineering,TheGlacierMetalCompanyLimited,Alperton.Wembley,MiddlesexHAO1HD,UKnecessaryandworkhasbeencarriedoutonbearingshapes23elasticconnectingrodbearing4,oilfeedfeaturess6,oilfilmhistory7,andmorerealisticmainbearingloadsharing89.Thisisinkeeping,althoughalittlelate,withthe1967prophecyfromCampbell,whichstatedthatItistheauthorsbeliefthat,withthecontinuingrapidadvanceincomputationalmethodsandwiththegrowingawarenessofthepowerfuldesigntechniqueswhichareAABaDBk¢,,jbEC\\,4\ii\aTCvFig1PolarloaddiagramsforVEBconnectingrodbearingrelativetoaconnectingrodaxis,bcylinderaxis,ccrankpinaxisTRIBOLOGYinternational0301679X/83/0301471803.00©1983ButterworthCoPublishersLtd147MairEnginebearingdesignIi,//Iieaimingforfewerassumptionsdatapresentationforbetterunderstem.dingofresultsbetterpredictionofoperatingconditionsloadsharing,heatbalanceexperimentalverification.Progressineachofthesecategoriesisveryimportamandeachsectioncomplementstheothers.Withtheneedtoconserveenergyandwithfueleconomyamajorissue,manyenginesarenowbeingdesignedwithhigherpowertoweightratiosTheresultanteffectsonbearingsarereductioninbearingsize,higherspecificloadsandtheuseoflowerviscosityoils.AllthesechangesbringtheSimplifiedandquickmethodManydataoresentationtechniquesshowninthispaperelatingtotheVEBbigendstud},caseuseEooKersshortoearingMobilitysolution.TheMobiitycoTcoorqasbeensuccessfullyappliedoverthelastt5years,ano..zexplainedindetailelsewhereu°.itsgreatattractionisthewayLsplitsjournalmovementintotwocononentssqueezeandwhirl,whichenabeaFulIorbitobecaiculatedver/rapidlywithnoreiterativecaicuiationsaeachtimestep.ForcompletenesstheshortbearingVEBerhalcentreorbitisincludedinthenewurvevaforbitsinFig2asupplementingthoseinRefI,andthevariationfnminimumfilmthicknessatdifferenttimestLroughot.theloadcycledefinedbycrankangleisshowniFig3.148983Voi8N3AsecondpartofBookersworkwastoproduceaclearancecirclefilmpressuremap2givingtheratioofthemaximumhydrodynamicpressuretothespecificloadatanypointintheclearancecircle.TheinsetdiagraminFig4showstheclearancecirclefilmpressuremapwiththeVEBorbitsuperimposed.Notethatthisorbitisnotplottedrelativetospacetheconventionalmethodbutonaclearancemapwhichiseffectivelybeingmovedinanangularsensethroughoutthecycle,suchthatthedirectionoftheappliedloadisalwaysdownwards.ThisisanimportantandvaluabletechniquewhenusingtheMobilitymethod.ThemaximumoilfilmpressureisobtainedfromtheserelationshipsandNomenclatureCrradialclearance,mDbearingdiameter,mhminminimumfilmthickness,meeccentricityvectorFforcevectorJlOOfo21ecosO1dO0Lbearinglength,mMMobility,dimensionlessPfoilfeedpressure,NmPmaxmaximumfilmpressure,Nm2PnspecificloadW/LD,Nm2QFoilflowconsideringfilmhistory,m3srigoroussolutionQHhydrodynamicflow,m3s1rapidsolutionQpfeedpressureflow,m3s1rapidsolutionQRflownotconsideringfilmhistory,m3srigoroussolutionQxflowfromexperiments,m3s1Rshaftradius,mrldynamicviscosity,Nsm2eeccentricityratio,dimensionlesskfrictionfactor0angleofoilholefromcentrelineCFseeFig23coandcoarefunctionsofjournalandbearingangularvelocity0.50.40,3G.5E0.20.1F1.875,5o°,.,....,2/0,10.001\,,\\\mL__o90oso5,oCrankangle,degreesFig3ShortbearingfilmthicknessratioVEBdo720MartinEnginebearingdesignitsvariationthroughouttheloadcycleisshowninthemainpartofFig4.AtGECintheUKRitchiendevelopedanewsemianalyticalmethodforpredictingthejournalcentreorbititusesaneasilyobtainedoptimizedshortbearingsolutionwhichhasimprovedaccuracyathigheccentricitiesoverthestandardshortbearingmethodtheorbitoftheVEBbigendbearingisshowninFig2b.Thislooksverysimilartoageneralfinitebearingorbitandapparentlyonlytook16secondstorunonanIBM370/145computerseveralyearsago.Theminimumoilfilmthicknessof0.0033mm0.00013inchesiscomparedinTable1withvaluesfromothersourcesincludingtheresultsofaGECfinitebearingprogramusingthestoreddataapproachseenextsection.Itisseentobewithinthescatterbandofthemorerigorousfinitebearingmethods,butstillmaintainstheadvantageofarapidsolution.Theminimumoilfilmthicknessduringacompletecycleofoperationisoneofthemostsignificantparametersonwhichtojudgebearingperformance.Itisgenerallyusedasacomparatorandrepresentsamajorfactorinrelatingpredictedperformancewithexistingbearingexperienceonsimilartypeengines.Itisdifficulttogiveprecisevaluesofminimumfilmthicknessatwhichbearingdamagemightoccur,asotherfactorssuchashighbearingtemperature,misalignment,inadequateoilfeedarrangementsandadverseenvironmentalconditionswillallhaveaneffect.Bookerllgivessomeguidanceondangerlevelsforfilmthicknessinconnectingrodbearingsforusewithshortbearingpredictionmethods.FinitebearingtheoriesUsingafiniteelementmethodferntosolvethefinitebearingtheory,GeneralMotorsResearchLaboratories2havetheabilitytoconsiderdifferentshapesofbearingandalsotoallowforthepresenceofgrooving.ForaplaincircularbearingGMhavesuccessfullycurvefittedbasicdatafromtheirfembearingmodel,andusedthistodeveloparapidmethod,typicallyreducingcomputationaltimefromhourstoseconds.BothmethodshavebeenappliedtotheProlix1.6672Pn2.540,,350/l/i/25\\m2o_E15.E.E1I0e5iiI1IIi090180270560450540650720Crankangle,degreesFig4ShortbearingmaximumfilmpressureVEBTRIBOLOGYinternational149MartL,.EnginebearingdesignRustonVEBbigend,andFigs2canddshowthejournalcentreorbitforthefiniteelementprogramandcurvefitprogramrespectively.Thesetwoorbitslookverysimilar,Nthoughtherewasaremarkablesavingincomputationaltimeforthecurvefitprogram.Filmthicknessratioandmaximumfilmpressurefromthetwome,hodsarecomparedinFigs5aandb.AlsonotethatthefilmpressurefromtheshortbearingtheoryFig4isverysimilartothatfromthefinitebearingferntheoryFig5boManyestablistmentsnowhavefiniteelementorfinitedifference2Dsolutionscapableofallowingfortheeffectofoilfeedfeaturesonhydrodynamicpressuregeneration,ThetandardVEBstudycase,withitscircumferentialgroove,isnotsuitableforillustratingsucheffects,soinsteadtheintermainbearingofa1.8\itregasolineenginewillbeused.TheleaddiagramisshowninFig6andfurtherdatcanbefoundinReferences6and7oTheorbitsinthetorcdiagramofFig7showthefilmthicknessreducedlocailyasaresultofthepresenceofanoilhole.ttshouldbenotedhowever,thatthesmallestfilmthicknessduringthecyclemaynotnecessarilybeimpairedAdesignmethodhasbeendevelopedattheGlacierMetalCowhi.chaltows,inamorecompleteway,fortheeffectsoffeedfeaturesinthebearingoItconsiderstheseeffectstoflintotwocategories.Thefirstrelatestothedehnentaieffectofthedevelopedpressureregionpassingovertheoilfeedregionhole,grooveetcofthebearing°Thesecondinvolvesthestudyofoittransportwithinthebearo.47Curvfitprogram0.5Finiteelementorcgrarr.........\\o.i,\\\,4090t802705604504,6.30720g_50moE20.CurvefitprogramFmffeelementprogram....../m//I/t/t/W\,j1rC9080£70360450540630720bCroOngledegreesFig5GeneralMotorsrapidcurvefitprogramcomparedrorigorousfernprogramVEB}adimensioMessfilmthickness,b}maximumfilmpressureingoiifilm,andtakesintoaccoumthedeleteriouseffectwhentheoi1fimextentisdepletedduetoinsufficientelibeingavailabletofilItheioadcarryingareaofthebearind.ThissecondcategoryissometimesreferredtoascilfiNstory.elif\ImhistoryMuchofthefundamentalworkonelifilmhistoryandor.film.boundariesmdynamicallyloadedbearingswaspione.rcattheUZKNationalEngineeringLaboratorybytheiateA..AoMilnes16,whoseuntimelydeathleftavodintheknowledgeoftNsveryspecializedfbldoMilneapFroachconsideredaneverchangingan_dme,andmeshatemomach.hefilmboundaries.ArxthermethoddevelopedatGlacierbyJonesconsidered,.......,,.i,eritocaiflOWSusingJfixedfinitedifferencemesh,withcontrolspacebounda.,aroundeachnode.TNslatterapproachwaseasiertoadepandhasbeenusedintheanaGsisofLheintermainbearinwithaholefeedinthe1.8itreengine6,¢sshownvtherighthanddiagramofFig7,thegeneralorbitshapew,thfilmhiscryisqutedifferent{reinpredictionswhenfT.mistoryeffectsareignoredAlthoughthesmallestfimthicknessduringtheioadcycleisagainhardiyaffectedwhenconsideringoifilm.history,onecouldperceiveacasefbrinstancewithalowoilfeedpressurewherethexraradaiexcursionofthejournacentremayro,mcedangereuslsinaifilmthicknesses°TNsemphasizestk,Orectonoshftrotcfion\fg6goZarloaddiagram.rtezainbearingoSS/ftLengine50June1983Vo5o3
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