用于不稳定性分析的重型汽车动力传动建模

GlobalPowertrainCongressGPC'2001,June5,2001,Detroit,Michigan,USAHEAVYTRUCKPOWERTRAINMODELLINGFORINSTABILITIESANALYSISV.Thomas,IMAGINE,Roanne,FranceN.JansevanRensburg,IMAGINESoftwareInc.,Detroit,MichiganH.Defay,RenaultVehiculesIndustriels,StPriest,FranceABSTRACTThispaperpresentstheconstructionofaheavytruckpowertrainmodelusedtoreproduceandanalyzeinstabilityphenomena,sometimescalled“surgephenomena”.Inmanypracticalcases,thedesignorimprovementofdynamicsystemscanbedoneusinganexperimentalapproachbutitisoftenexpensive,complextoperform,andtimeconsuming.Inthesecasesanumericalmodelallowsquicksensitivityanalysisonparametersandevaluationofsuggestedtechnicalsolutions.InthisstudythedynamicsystemssimulationsoftwareAMESim®isusedbecauseitcontainsnumerousspecificmodellibrariesthatlimitsthedevelopmentworknecessaryandisbasedonanadvancednumericalintegrator.Furthermore,AMESim®hastheabilitytotakenon-lineareffectsintoaccountandisabletomixdiscreteandcontinuousmodelsinasinglesystem.THESURGEPHENOMENON[1,2]Vehiclevibrationduetotheexcitationofdrivelinetorsionmodesbytheengineiscalled“pumping”.Pumpingcausesdriverdiscomfortandmayleadtoseverepowertraindamage.Thiskindofprobleminitiallyappearedduringtheseventieswhennewrequirementsforhightorqueengineswereset.Theinstabilitycurrentlystudiedhasbeenidentifiedbyconsumersthatcomplainaboutdriverdiscomfortandinsomeseverecasesofvehiclebreakdown.Theproblemsoccuronheavytruckswithanelectronicinjectioncontrolsystem(associatedwithamechanicalin-linepump).Thesurgephenomenoncorrespondstostrongoscillationsofthepowertrainresultingfromthecouplingbetweenthevibrationsofthedrivelineandtheunsteadytorquedeliveredbytheengineandproducedbycombustion.Thus,theinjectioncontrolsystembehaviourisofmajorimportancesinceitdeterminestheshapeofthein-cylinderpressureasafunctionoftheengineoperatingpoint.Themainvehiclecharacteristicswhichcancause“pumping”are:•Themethodofinjectioncontrol(mechanicalorelectronicinjection)•Thedrivelinevibratorycharacteristics(definingthepossibleunstableconfigurationsinthepowertrain).POWERTRAINMODELLINGThepowertrainoftheheavytruckcanbedividedintothreemainsub-systems.Thesearetheengine,thedrivelineandtheinjectioncontrolsystem.Eachsub-systemismodelledassimplyaspossiblesincethepurposeofthestudyistoanalysethecouplingsbetweensystemsandnottheexactdynamicbehaviourofeachelement.GearBoxDiff.HeavyTruckICEngineWheelECUDriverInjectionEnginespeedEngineloadFigure1–TheHeavyTruckPowertrainTHEICENGINEAsformostheavytrucks,theheartofthepowertrainliesintheengine,whichisaninternalIgnition-Compressionengine.ThechoicefortheDieselismainlyjustifiedbyconsumptiongainsbutalsobythenecessityforhightorquesGlobalPowertrainCongressGPC'2001,June5,2001,Detroit,Michigan,USAevenatlowenginespeeds.Whenutilizingdirectinjectionandturbocharging,thecompressionignitionengineseemstobethebestcompromisebetweenfueleconomy,performanceandpollutionwithcurrenttechnology.Sincethisstudyisconcernedwithlowfrequencyphenomena,theenginecanbeseenasatorquesourceanditwouldnotbenecessarytomodelthecrankshaftrotaryinertiasexactlybutonlythekinematicsofthepistonasafunctionoftheangulardisplacement.Theturbochargerwillnotbemodeledindetailbecauseoftheadditionalcomplexityitintroducesandthestrongcouplingthatitwouldimplyontheenginenumericalmodel.Thus,theturboismodeledasapressuresource,whichisaboundaryconditionofthesystem.Themono-cylindermodel(Figure2)willbeduplicatedtoformacompleteengine.CamshaftsIntakeExhaustCombustionChamberCrankshaftDrivelinerotaryvelocityWallheatexchangeCombustionheatreleasePressure&TemperaturecalculationInjectorPistonTurbochargerFigure2–Modellingofamono-cylinderTheheartofthesystemisthecombustionchamberwherefuelenergyistransformedduringcombustionintoanavailabletorqueonthecrankshaft.Duringthefourstrokes,severalaspectsmustbetakenintoaccountsuchasenginebreathing,injectionandcombustion,heattransferandpistonwork.•EnginebreathingThecombustioninaninternalenginerequirestwocompounds:freshairandfuel.Thus,thequalityoftheenginefillingisasimportantforperformanceasitstotalcapacityorastheamountoffuelinjected.Tosimulatethefirstorderbehavioroftheintakeandexhaustflows,simplevalvemodelsareusedtocalculateamassflowrateasafunctionofthepressuredropthroughthevalvewiththeclassicalBarrédeSaintVenantequations(1,2),thatarevalidforsubsonicandsonicflows(assumingaperfectgas).uumqTPCCAm⋅⋅⋅=&(1)whereuTanduParetheupstreamtemperatureandpressure,Athecross-sectionalareaandCmtheflowparameter.TheareaAisafunctionofthepipediameterandthevalveliftthatissuppliedbyadata-fileasafunctionofthecamshaftdisplacement.TheflowcoefficientCqisintroducedtoadjustthetheoreticalrelationtoexperiments.Thiscoefficientislessthan1andisusedtoincludeextralossesduetolocalfrictionandlossofkineticenergy.Whentheflowissubsonic,theflowparameterCmisafunctionofthepressureratioudPPandthespecificheatratioγ.Whentheflowissonic,theflowparameterisconstant.GlobalPowertrainCongressGPC'2001,June5,2001,Detroit,Michigan,USA()()≤+γ+γγ⋅=+γγ−−γγ⋅=−γ−γ+γγ+γγ(sonic)PPPifrr(subsonic)PPPifPPPPrCcr