DevelopmentsinenginebearingdesignF.A.Martin*Someoftheimportantrecentdevelopmentsinenginebearingdesigntech-niquesarehighlighted.Theavailabilityofincreasedcomputingpowerhasenabledmorerealisticassumptionsaboutbearingconditionstobeconsidered；theseincludeoilfeedfeatures,oilfilmhistory,non-circularbearings,inertiaeffectsduetojournalcentremovement,improvedpredictionofmainbearingloads,flexiblehousingsandspecialbearings.Referencestotheseadvancesaremade,togetherwithillustrationsofhowtheyaffectpredictedbearingperformance.Experimentalevidenceisalsobeingobtained,whichhelpstoverifyandgiveconfidenceintheanalyticalpredictionsKeywords:journalbearings,bearings+design,hydrodynamiclubrication,bearingstress,bearinghousings,oilgroovesEnginebearingperformanceisdependentuponmanyfactors,fromthemechanicalconfigurationoftheenginetothehydrodynamicsoftheoilfilm.Thispaperhighlightsthemoreimportantfactorstobeconsidered,andrelatesthemtorecentadvances,bothpublishedandunpublished,throughouttheworld.Thereviewattemptsnotjusttoreferencetheseadvances,buttoillustratehowtheyextendtheareasofperformanceprediction,experimentalverifica-tionandthedesignofspecialbearings.Historically,theearliestattemptsatthedesignofdynamic-allyloadedbearingswerebasedonmaximumallowablespecificload(definedasmaximumappliedloaddividedbyprojectedbearingarea),andthisisstillavaluableparameter.Withtheadventofgraphicalandnumericaltechniquescapableofsolvingahydrodynamicbearingmodel,albeitstillhighlysimplified,estimatesofminimumoilfilmthick-nesscouldbemade,andusedasacomparatortojudgethelikelihoodofproblemsonnewengines.Acomprehensivestudyofthoseearlypredictivemethodscanbefoundinthe1967reviewpaperbyCampbelletalI；asastudycasethisusedthebigendbearingofaRustonandHornsbyVEBMkIII600hp,600r/mindieselengine.NearlytwentypredictedandexperimentaljournalorbitsfromvarioussourceswerediscussedinthevolumeofI.Mech.E.proceedingswhichcontainedthatpaper,andthesamestudycaseisstillbeingusedbyworkersinthisfieldtoday(polarloaddiagram,Fig1(a)；completedata,Ref1).Ithasbeenusedinthisreviewtoillustratesomeofthesubse-quentadvancesinpredictioncapabilities.Manyofthemajorassumptionsusedintheearlypredictionmethodswerecertainlynotrealistic,butwereusedasexpedientstoobtainamathematicalmodelwhichcouldbesolvedwiththelimitedcomputingcapabilitiesthenavailable.TheseassumptionsincludedcircularrigidbearingsandaperfectsupplyofisoviscousNewtonianoil.Inmanycasesthebearingsurfacewasassumedtobeuninterruptedbyoilfeedfeaturesinthedevelopedfilmpressureregionsand,externaltothebearing,thecalculationofthemainbearingloadstooknoaccountofthecrankshaftandcrank-casestiffnesses.Overthelastdecadeincreasesincomputingpowerhavemeantthatmanyofthoseearlyassumptionsarenolonger*DepartmentofApplicationsEngineering,TheGlacierMetalCom-panyLimited,Alperton.Wembley,MiddlesexHAO1HD,UKnecessaryandworkhasbeencarriedoutonbearingshapes23elasticconnectingrodbearing4,oilfeedfeat-uress6,oilfilmhistory7,andmorerealisticmainbearingloadsharing89.Thisisinkeeping,althoughalittlelate,withthe1967prophecyfromCampbell,whichstatedthat:Itistheauthorsbeliefthat,withthecontinuingrapidadvanceincomputationalmethodsandwiththegrowingawarenessofthepowerfuldesigntechniqueswhichareAABaD-Bk,jbEC,4iiaT-CvFig1PolarloaddiagramsforVEBconnecting-rodbearingrelativeto:(a)connectingrodaxis,(b)cylinderaxis,(c)crankpinaxisTRIBOLOGYinternational0301679X/83/030147-18$03.001983Butterworth&Co(Publishers)Ltd147Mair-EnginebearingdesignIi,/Iieaimingforfewerassumptionsdatapresentationforbetterunderstem.dingofresultsbetterpredictionofoperatingconditions(loadsharing,heatbalance)experimentalverification.Progressineachofthesecategoriesisveryimportamandeachsectioncomplementstheothers.Withtheneedtoconserveenergyandwithfueleconomyamajorissue,manyenginesarenowbeingdesignedwithhigherpowertoweightratiosTheresultanteffectsonbear-ingsarereductioninbearingsize,higherspecificloadsandtheuseoflowerviscosityoils.AllthesechangesbringtheSimplifiedandquickmethodManydataoresentationtechniquesshowninthispape；relatingtotheVEBbigendstud,caseuseEooKersshortoearingMobilitysolution.TheMobi!itycoT:co-or:qasbeensuccessfullyappliedoverthelastt5years,ano.zexplainedindetailelsewhereu.itsgreatattractionisthewayLsplitsjournalmovementintotwocon:onentssqueezeandwhirl,whichenab!eaFulIorbi!tobecaiculatedver)/rapidlywithnoreiterativecaicuiationsaeachtimestep.ForcompletenesstheshortbearingVEB)erhalcentreorbitisincludedinthenew%urvevaforbitsinFig2a(supplementingthoseinRefI,andthevariationfnminimumfilmthicknessatdifferenttimestLroughot.theloadcycle(definedbycrankangle)isshowni:Fig3.148983Voi!8N3AsecondpartofBookersworkwastoproduceaclearancecirclefilmpressuremap2givingtheratioofthemaximumhydrodynamicpressuretothespecificloadatanypointintheclearancecircle.TheinsetdiagraminFig4showstheclearancecirclefilmpressuremapwiththeVEBorbitsuperimposed.Notethatthisorbitisnotplottedrelativetospace-theconventionalmethod-butonaclearancemapwhichiseffectivelybeingmovedinanangularsensethroughoutthecycle,suchthatthedirectionoftheappliedloadisalwaysdownwards.ThisisanimportantandvaluabletechniquewhenusingtheMobilitymethod.ThemaximumoilfilmpressureisobtainedfromtheserelationshipsandNomenclatureCrradialclearance,mDbearingdiameter,mhminminimumfilmthickness,meeccentricityvectorFforcevectorJlOOfo2(1+ecosO)-1dO0Lbearinglength,mMMobility,dimensionlessPfoilfeedpressure,Nm-:Pmaxmaximumfilmpressure,Nm-2Pnspecificload(W/LD),Nm-2QFoilflowconsideringfilmhistory,m3s-(rigoroussolution)QHhydrodynamicflow,m3s-1(rapidsolution)Qpfeedpressureflow,m3s-1(rapidsolution)QRflownotconsideringfilmhistory,m3s-(rigoroussolution)Qxflowfromexperiments,m3s-1Rshaftradius,mrldynamicviscosity,Nsm-2eeccentricityratio,dimensionlesskfrictionfactor0angleofoilholefromcentrelineCF(seeFig23)coandcoarefunctionsofjournalandbearingangularvelocity0.50.4-0,3-G.5E0.2-0.1-F1.875,5:-)o；,?.,.-.,2/0,10.001,mL_o90&os；o5,oCrankangle,degreesFig3Shortbearingfilmthicknessratio(VEB)do720Martin-EnginebearingdesignitsvariationthroughouttheloadcycleisshowninthemainpartofFig4.AtGECintheUKRitchiendevelopedanewsemi-analyticalmethodforpredictingthejournalcentreorbit；itusesaneasilyobtainedoptimizedshortbearingsolutionwhichhasimprovedaccuracyathigheccentricitiesoverthestandardshortbearingmethod；theorbitoftheVEBbigendbearingisshowninFig2(b).Thislooksverysimi-lartoageneralfinitebearingorbitandapparentlyonlytook16secondstorunonanIBM370/145computer(severalyearsago).Theminimumoilfilmthicknessof0.0033mm(0.00013inches)iscomparedinTable1withvaluesfromothersources(includingtheresultsofaGECfinitebearingprogramusingthestoreddataapproach-seenextsection).Itisseentobewithinthescatterbandofthemorerigorousfinitebearingmethods,butstillmain-tainstheadvantageofarapidsolution.Theminimumoilfilmthicknessduringacompletecycleofoperationisoneofthemostsignificantparametersonwhichtojudgebearingperformance.Itisgenerallyusedasacomparatorandrepresentsamajorfactorinrelatingpredictedperformancewithexistingbearingexperienceonsimilartypeengines.Itisdifficulttogiveprecisevaluesofminimumfilmthicknessatwhichbearingdamagemightoccur,asotherfactorssuchashighbearingtemperature,misalignment,inadequateoilfeedarrangementsandadverseenvironmentalconditionswillallhaveaneffect.Bookerllgivessomeguidanceondangerlevelsforfilmthicknessinconnectingrodbearings(forusewithshortbearingpredic-tionmethods).FinitebearingtheoriesUsingafiniteelementmethod(fern)tosolvethefinitebearingtheory,GeneralMotorsResearchLaboratories2havetheabilitytoconsiderdifferentshapesofbearingandalsotoallowforthepresenceofgrooving.Foraplaincir-cularbearingGMhavesuccessfullycurve-fittedbasicdatafromtheirfembearingmodel,andusedthistodeveloparapidmethod,typicallyreducingcomputationaltimefromhourstoseconds.BothmethodshavebeenappliedtotheProlix1.6672Pn2.540,3；50/l/i/:-25m=2o_E15.E.E1I0e5iiI1IIi090180270560450540650720Crankangle,degreesFig4Shortbearingmaximumfilmpressure(VEB)TRIBOLOGYinternational149MartL,.EnginebearingdesignRustonVEBbigend,andFigs2(c)and(d)showthejournalcentreorbitforthefiniteelementprogramandcurve-fitprogramrespectively.Thesetwoorbitslookverysimilar,Nthoughtherewasaremarkablesavingincompu-tationaltimeforthecurve-fitprogram.Filmthicknessratioandmaximumfilmpressurefromthetwome,hodsarecom-paredinFigs5(a)and(b).Alsonotethatthefilmpressurefromtheshortbearingtheory(Fig4)isverysimilartothatfromthefinitebearingferntheory(Fig5b)oManyestablistmentsnowhavefiniteelementorfinitedifference2-Dsolutionscapableofallowingfortheeffectofoilfeedfeaturesonhydrodynamicpressuregeneration,The%tandardVEBstudycase,withitscircumferentialgroove,isnotsuitableforillustratingsucheffects,soinsteadtheintermainbearingofa1.8itregasolineenginewillbeused.TheleaddiagramisshowninFig6andfurtherdatcanbefoundinReferences6and7oTheorbitsinthetorcdiagramofFig7showthefilmthicknessreducedlocailyasaresultofthepresenceofanoilhole.ttshouldbenotedhowever,thatthesmallestfilmthicknessduringthecyclemaynotnecessarilybeimpairedAdesignmethodhasbeendevelopedattheGlacierMetalCowhi.chaltows,inamorecompleteway,fortheeffectsoffeedfeaturesinthebearingoItconsiderstheseeffectstoflintotwocategories.Thefirstrelatestothedeh-:nentaieffectofthedevelopedpressureregionpassingovertheoilfeedregion(hole,grooveetc)ofthebearingThesecondinvolvesthestudyofoittransportwithinthebear-o.47!Curvfitprogram0.5Finiteelementorcgrarr.:!o.i-,40-90t802705604504,6.30720g_50moE=20.CurvefitprogramFmffeelementprogram./m/I/t/t/W,j1rC908070360450540630720bCroOngledegreesFig5GeneralMotorsrapidcurvefitprogramcomparedrorigorousfernprogram(VEB:(a)dimensioMessfilmthick-ness,(bmaximumfilmpressureingoiifilm,andtakesintoaccoumthedeleteriouseffectwhentheoi1fi!mextentisdepletedduetoinsufficientelibeingavailabletofilItheioadcarryingareaofthebearind.Thissecondcategoryissometimesreferredt