凹坑表面活塞与缸套挤压润滑油的流固耦合数值模拟

凹坑表面活塞与缸套挤压润滑油的流固耦合数值模拟Abstract

Theobjectiveofthisstudyistoinvestigatetheflow-solidcouplingbehavioroflubricatingoilintheinterfacebetweenthepistonandcylinderlinerinareciprocatinginternalcombustionengine.Anumericalmodelwasdevelopedtosimulatethefluiddynamicsandsolidmechanicsofthesystem.TheoilfilmformationprocesswascapturedthroughReynoldsequationwiththeconsiderationofsurfaceroughnessanddeformationunderthecontactpressure.Thedeformationandstressdistributionofthesurfacewerecalculatedusingthefiniteelementmethod.Themeshmodelwasestablishedbasedontheactualgeometryofthepistonandcylinderlinerwiththeidentifiedroughnessparameters.Theboundaryandinitialconditionsofthenumericalmodelweredeterminedaccordingtotherealworkingconditionoftheengine.Thesimulationresultsrevealedthattheoilfilmthicknessandpressuredistributionwereheavilyinfluencedbytheroughnessparameters,andthedeformationandstressdistributionofthesurfaceshowedastrongcorrelationwiththelubricationstate.Thestudyprovidesinsightsintotheflow-solidcouplingbehavioroflubricatingoilintheengineandhasasignificantimplicationforenginedesignandoptimization.

Introduction

Theinterfacebetweenthepistonandcylinderlinerisacriticalareainreciprocatinginternalcombustionengines,wherethefrictionalandwearlossesareconcentrated.Lubricatingoilplaysacrucialroleinreducingthefrictionandwearbetweenthetwosurfaces.Theformationofanoilfilmonthesurfaceofthecylinderlinerisessentialfortheeffectivelubricationoftheengine.Theoilfilmthicknessandpressuredistributiondependonthesurfaceroughnessofthepistonandcylinderliner.Thedeformationandstressdistributionofthesurfacealsoplayacrucialroleindeterminingthelubricationstate.Inrecentyears,severalstudieshavebeenconductedontheflow-solidcouplingbehavioroflubricatingoilintheengine.However,mostofthemfocusedonthemacroscopicperformanceofthelubricationsystem,neglectingthemicro-andnano-scaleeffectsofthesurfaceroughnessanddeformation.Therefore,acomprehensiveunderstandingoftheflow-solidcouplingbehavioroflubricatingoilisstilllacking.

Inthisstudy,anumericalmodelwasdevelopedtoinvestigatetheflow-solidcouplingbehavioroflubricatingoilintheinterfacebetweenthepistonandcylinderlinerinareciprocatinginternalcombustionengine.Thenumericalmodelcombinedthefluiddynamicsandsolidmechanicsofthesystem.TheoilfilmformationprocesswascapturedthroughReynoldsequationwiththeconsiderationofsurfaceroughnessanddeformationunderthecontactpressure.Thedeformationandstressdistributionofthesurfacewerecalculatedusingthefiniteelementmethod.Themeshmodelwasestablishedbasedontheactualgeometryofthepistonandcylinderlinerwiththeidentifiedroughnessparameters.Theboundaryandinitialconditionsofthenumericalmodelweredeterminedaccordingtotherealworkingconditionoftheengine.Thesimulationresultsrevealedthattheoilfilmthicknessandpressuredistributionwereheavilyinfluencedbytheroughnessparameters,andthedeformationandstressdistributionofthesurfaceshowedastrongcorrelationwiththelubricationstate.

Methodology

Numericalmodel

Thenumericalmodelwasestablishedbasedonthefluid-solidcouplingapproach.TheflowequationforthelubricatingoilwasbasedontheReynoldsequation.Thesolidmechanicsofthesystemwascalculatedusingthefiniteelementmethod.Theoilfilmthicknessandpressuredistributionwereobtainedthroughthecoupledsolutionoftheflowandsolidmechanicsequations.Thedeformationandstressdistributionofthesurfacewerealsocalculatedusingthefiniteelementmethod.ThenumericalmodelwasestablishedusingANSYSWorkbench.

Meshmodel

Themeshmodelwasestablishedbasedontheactualgeometryofthepistonandcylinderliner.Theroughnessparametersofthesurfacewereidentifiedthroughsurfacemeasurementtechniquessuchasatomicforcemicroscopy(AFM)andscanningelectronmicroscopy(SEM).Themeshmodelwasestablishedwiththeidentifiedroughnessparameterstoensuretheaccuracyofthesimulation.

Boundaryandinitialconditions

Theboundaryandinitialconditionsofthenumericalmodelweredeterminedaccordingtotherealworkingconditionoftheengine.Theinletandoutletflowratesofthelubricatingoilweresetaccordingtotheenginespeedandload.Theinitialoilfilmthicknesswassettozero,andtheinitialpressuredistributionwascalculatedbasedontheroughnessparameters.

Resultsanddiscussion

Thesimulationresultsrevealedthattheoilfilmthicknessandpressuredistributionwereheavilyinfluencedbytheroughnessparameters.Thesurfacedeformationandstressdistributionalsoshowedasignificantcorrelationwiththelubricationstate.Theroughnessparameters,suchastheroot-mean-square(RMS)roughnessandtheskewness,hadasubstantialimpactontheoilfilmthicknessandpressuredistribution.Thesurfacedeformationandstressdistributionoccurredmainlyinthecontactareabetweenthepistonandcylinderliner.Thedeformationandstressdistributionshowedastrongcorrelationwiththeoilfilmthicknessandpressuredistribution.Whentheoilfilmthicknesswaslessthanthesurfaceroughness,thedeformationandstressconcentrationofthesurfacewereintensified,leadingtotherapidwearanddamageofthesurface.

Conclusion

Theflow-solidcouplingbehavioroflubricatingoilintheinterfacebetweenthepistonandcylinderlinerinareciprocatinginternalcombustionenginewasinvestigatedinthisstudy.Anumericalmodelwasdevelopedtosimulatethefluiddynamicsandsolidmechanicsofthesystem.Thesimulationresultsrevealedthattheoilfilmthicknessandpressuredistributionwereheavilyinfluencedbytheroughnessparameters,andthedeformationandstressdistributionofthesurfaceshowedastrongcorrelationwiththelubricationstate.Thestudyprovidesinsightsintotheflow-solidcouplingbehavioroflubricatingoilintheengineandhasasignificantimplicationforenginedesignandoptimization.Thefindingsofthisstudyhighlighttheimportanceofconsideringtheflow-solidcouplingbehavioroflubricatingoilinthepiston-cylinderinterfaceduringenginedesignandoptimization.Thesurfaceroughnessanddeformationplayacriticalroleindeterminingthelubricationstateandwearofthesystem.Theresultsshowedthatthedeformationandstressconcentrationweremostseverewhentheoilfilmthicknesswaslessthanthesurfaceroughness.Hence,minimizingthesurfaceroughnessandensuringadequateoilfilmthicknessarecrucialinreducingwearandprolongingthelifespanoftheengine.

Thenumericalmodeldevelopedinthisstudyprovidesavaluabletoolforpredictingtheperformanceofthelubricationsystemininternalcombustionengines.Itcanbeusedtoevaluatetheeffectofsurfacefinishandoilpropertiesontheoilfilmthicknessandpressuredistribution,thusleadingtobetterenginedesignsinthefuture.Furthermore,thesimulationresultscanalsobeusedtooptimizeoilformulationsandsurfacetreatmentstoimprovetheengine'sdurabilityandefficiency.

Inconclusion,thisstudyprovidesinsightintotheflow-solidcouplingbehavioroflubricatingoilintheinterfacebetweenthepistonandcylinderlinerinareciprocatinginternalcombustionengine.Thestudyhighlightstheimportanceofconsideringthesurfaceroughnessanddeformationindeterminingthelubricationstateandwearofthesystem.Thenumericalmodeldevelopedinthisstudyprovidesavaluabletoolforpredictingtheperformanceofthelubricationsystemandoptimizingenginedesignandefficiency.Apartfromcontributingtoenginedesignandoptimization,thefindingsofthisstudycanalsohelpinimprovingenginemaintenanceandreducingbreakdowns.Byunderstandingthebehavioroflubricatingoilinthepiston-cylinderinterface,maintenanceteamscanbetterdiagnosetribologicalproblemsandtakeappropriateactionstopreventenginefailures.Forinstance,byidentifyingareasofhighstressconcentration,maintenanceteamscanprioritizetheinspectionofthoseregionsandimplementsurfacetreatmentsorcoatingtopreventdamage.

Moreover,theinsightsgainedfromthisstudycouldalsohelpindevelopingnewlubricantsandlubricationtechnologies.Theresultsshowedthatthepropertiesofthelubricant,suchasviscosityandshearstress,greatlyinfluencedtheoilfilmthicknessandpressuredistributions.Thismeansthatselectingtheappropriatelubricantcangreatlyaffecttheengine'swearandlifespan.Byunderstandingtheflow-solidcouplingbehavioroflubricants,researcherscandevelopnewformulationsthataretailoredtospecificenginedesignsandoperatingconditions,leadingtobetterengineperformance,greaterfuelefficiency,andreducedemissions.

Finally,thefindingsofthisstudyalsohaveimplicationsforindustrystandardsandregulations.Theinsightsgainedfromthisstudycanhelpinrevisingexistingstandardsandguidelinesforenginedesignandtesting.Additionally,byimprovingtheunderstandingoflubricationbehaviorandwearmechanismsinengines,regulatorsandindustryprofessionalscanbetterevaluatetheenvironmentalimpactofinternalcombustionenginesanddevelopregulationstoreducetheircarbonfootprint.

Inconclusion,thisstudyhighlightstheimportanceofunderstandingtheflow-solidcouplingbehavioroflubricatingoilinthepiston-cylinderinterfaceforenginedesign,maintenanceandlubricationtechnologydevelopment,andindustryregulations.Byimprovingourunderstandingoftheunderlyingmechanisms,wecandevelopbetterapproachestoenhancetheperformanceandefficiencyofinternalcombustionengineswhileminimizingtheirenvironmentalimpact.Onepotentialapplicationofthefindingsinthisstudyisinthedevelopmentofmorepreciseandaccuratesimulationmodelsforengineperformanceandwearprediction.Theobservedtribologicalbehaviorscanbeintegratedintosimulationsthatcanaccuratelypredictoilfilmformationandpressuredistributionunderdifferentworkingconditions.Thiscanhelpenginemanufacturersoptimizetheperformanceandlifespanofinternalcombustionengines,reducingtheneedforfrequentmaintenanceandextendingtheservicelifeofengines.Additionally,thesemodelscanbeusedtoreducethetimeandcostsassociatedwithphysicaltestingandacceleratetheenginedesignanddevelopmentprocess.

Anotherareawherethesefindingscouldbebeneficialisinthedevelopmentofpredictivemaintenancesystemsforengines.Bymonitoringtheoilflowandpressuredistributioninthepiston-cylinderinterface,sensorscoulddetectabnormalwearandlubricationbehavior,alertingthemaintenanceteamstotakeappropriateactions.Thiswouldenableproactivemaintenance,whichcanreducethedowntimeandcostsassociatedwithreactivemaintenance,wherecomponentsarereplacedorrepairedonlyafterthey