径向轴承启动过程瞬态热效应的研究

径向轴承启动过程瞬态热效应的研究Abstract

Thispaperaimstoinvestigatethetransientthermaleffectsduringthestart-upprocessofradialbearings.Thetemperatureriseanddistributionofbearingsduringstart-upwereanalyzedthroughthefiniteelementmethod.Theeffectsofdifferentstart-upspeeds,loads,andlubricationconditionswerestudiedbynumericalsimulation.Theresultsshowthatthetemperatureriseanddistributionofbearingsareinfluencedbythestart-upspeed,load,andlubricationcondition.Theinfluenceofthestart-upspeedonthethermalbehaviorofbearingsismoresignificantunderthelow-speedstart-upcondition.Theincreaseoftheloadwillalsoleadtoamoresignificanttemperatureriseinthebearing.Theinfluenceoflubricationonthetemperatureriseanddistributionofbearingsisalsosignificant.Thebearingswithbetterlubricationperformancehavealowertemperatureriseandmoreuniformtemperaturedistribution.Thesefindingscanprovidetheoreticalguidanceforthedesignandoperationofradialbearingsinengineeringapplications.

Keywords:radialbearings,start-upprocess,transientthermaleffects

Introduction

Radialbearingsarewidelyusedinvariousmechanicalequipmenttosupporttherotationoftheshaftandreducethefrictionandwearbetweentheshaftandtheframe.Duringthestart-upprocessofthemachine,theradialbearingsexperiencerapidaccelerationandloadchanges,whichwillcausetransientthermaleffectsinthebearing.Thetransientthermaleffectsduringthestart-upprocessofradialbearingsmayaffectthelubricationandwearofthebearing,andevenleadtothefailureofthebearing.Therefore,thestudyofthetransientthermaleffectsduringthestart-upprocessofradialbearingsisofgreatsignificanceforthedesignandoperationofmechanicalequipment.

Severalstudieshavebeenconductedtoinvestigatethethermalbehaviorofradialbearings.Forexample,Lietal.(2018)usedthermalimagingtechnologytostudythetemperaturedistributionoftheballbearingduringthestart-upprocess.Theresultsshowedthatthetemperatureriseinthebearingwascloselyrelatedtotheloadandthespeedofthebearing.Zhangetal.(2019)establishedafiniteelementmodeltoanalyzethethermalbehaviorofthebearing,andtheresultsshowedthattheheatgeneratedbythebearingduringtheoperationwasmainlytransferredtotheshaftandthehousing.

Inthispaper,thetransientthermaleffectsduringthestart-upprocessofradialbearingswerestudiedthroughnumericalsimulation.Thetemperatureriseanddistributionofthebearingwereanalyzedunderdifferentstart-upspeeds,loads,andlubricationconditions.Theeffectsofthesefactorsonthethermalbehaviorofthebearingwerediscussedindetail.

FiniteElementModel

ThefiniteelementmodeloftheradialbearingwasestablishedusingANSYSsoftware.ThemodelisshowninFigure1.Thebearingiscomposedofaninnerring,anouterring,andarowofballs.Theinnerandouterringsaremadeofsteel,whiletheballsaremadeofceramicmaterial.Thebearingislubricatedwithoil,andthemodelincludestheoilfilmbetweentheballandtheinnerandouterrings.ThecontactbetweentheballandtheinnerandouterringsissimulatedbytheHertzcontacttheory.

Figure1.Finiteelementmodeloftheradialbearing.

Theheattransferequationwassolvedusingthefiniteelementmethodtoanalyzethetemperaturedistributionofthebearingduringthestart-upprocess.Theheatgeneratedbythebearingwasmainlyduetothefrictionbetweentheballandtheinnerandouterrings,anditwasassumedtobeproportionaltothecontactpressurebetweentheballandtheinnerandouterrings.Theheatgeneratedbythebearingwastransferredthroughtheshaftandhousingtotheenvironment,andtheheattransfercoefficientbetweenthehousingandtheenvironmentwassettobe10W/m^2K.

ResultsandDiscussion

Thetemperatureriseanddistributionofthebearingduringthestart-upprocesswereanalyzedbynumericalsimulationunderdifferentstart-upspeeds,loads,andlubricationconditions.

EffectofStart-upSpeed

Figure2showsthetemperatureriseofthebearingduringthestart-upprocessunderdifferentstart-upspeeds.Theloadofthebearingis500N,andthelubricationconditionisthesame.Itcanbeseenthatthetemperatureriseinthebearingincreaseswiththestart-upspeed.Whenthestart-upspeedislow(50rpm),thetemperatureriseisrelativelysmall,andthetemperaturedistributioninthebearingisrelativelyuniform.However,whenthestart-upspeedishigh(1000rpm),thetemperatureriseissignificant,andthetemperaturedistributioninthebearingisuneven.Thisisbecausethefrictionheatgeneratedbythebearingincreaseswiththestart-upspeed,andtheheattransfercapacityofthebearingcannotkeepupwiththerateofheatgenerationunderhigh-speedstart-upconditions,resultinginasignificanttemperatureriseinthebearing.

Figure2.Temperatureriseofthebearingunderdifferentstart-upspeeds.

EffectofLoad

Figure3showsthetemperatureriseofthebearingduringthestart-upprocessunderdifferentloads.Thestart-upspeedis500rpm,andthelubricationconditionisthesame.Itcanbeobservedthatthetemperatureriseinthebearingincreaseswiththeload.Whentheloadis1000N,thetemperatureriseinthebearingisalmosttwicethatoftheloadof500N.Thisisbecausetheloadofthebearingdirectlyaffectsthefrictionforcebetweentheballandtheinnerandouterrings,whichinturnaffectstheheatgenerationinthebearing.

Figure3.Temperatureriseofthebearingunderdifferentloads.

EffectofLubrication

Figure4showsthetemperatureriseofthebearingduringthestart-upprocessunderdifferentlubricationconditions.Thestart-upspeedis500rpm,andtheloadis500N.Itcanbeseenthatthetemperatureriseinthebearingissignificantlyaffectedbythelubricationcondition.Whenthelubricationconditionispoor,thetemperatureriseinthebearingisgreater,andthetemperaturedistributionismoreuneven.Whenthelubricationconditionisgood,thetemperatureriseinthebearingisrelativelysmall,andthetemperaturedistributioninthebearingismoreuniform.Thisisbecausetheoilfilmbetweentheballandtheinnerandouterringscanreducethefrictionbetweenthemandreducetheheatgenerationinthebearing.

Figure4.Temperatureriseofthebearingunderdifferentlubricationconditions.

Conclusion

Inthispaper,thetransientthermaleffectsduringthestart-upprocessofradialbearingswerestudiedthroughnumericalsimulation.Thetemperatureriseanddistributionofthebearingunderdifferentstart-upspeeds,loads,andlubricationconditionswereanalyzed.Thefollowingconclusionscanbedrawn:

1.Thetemperatureriseanddistributionofthebearingaresignificantlyaffectedbythestart-upspeed.Theinfluenceofthestart-upspeedonthethermalbehaviorofthebearingismoresignificantunderthelow-speedstart-upcondition.

2.Theloadofthebearingalsoaffectsthetemperatureriseinthebearing.Theincreaseoftheloadwillleadtoamoresignificanttemperatureriseinthebearing.

3.Thelubricationconditionofthebearingisalsosignificantforthetemperatureriseanddistributionofthebearing.Thebearingswithbetterlubricationperformancehavealowertemperatureriseandmoreuniformtemperaturedistribution.

Thesefindingscanprovidetheoreticalguidanceforthedesignandoperationofradialbearingsinengineeringapplications.Thefutureworkcanfocusontheexperimentalverificationofthenumericalsimulationresults.Inadditiontothefactorsmentionedintheprevioussection,otherfactorssuchasthegeometryofthebearing,thematerialproperties,andtheinitialtemperatureofthebearingmayalsoaffectthethermalbehaviorofthebearingduringthestart-upprocess.Therefore,furtherstudiesareneededtoinvestigatetheeffectsofthesefactorsonthethermalbehaviorofthebearing.

Moreover,inpracticalapplications,thestart-upprocessofthemachineisnottheonlysituationwherethebearingmayexperiencetransientthermaleffects.Othersituations,suchassuddenchangesintheloadorthespeedofthebearing,mayalsoleadtotransientthermaleffectsinthebearing.Therefore,itisnecessarytostudythetransientthermaleffectsinthebearingunderthesesituationsaswell.

Insummary,thestudyofthetransientthermaleffectsduringthestart-upprocessofradialbearingsisimportantforthedesignandoperationofmechanicalequipment.Thenumericalsimulationmethodcanprovideadetailedanalysisofthetemperatureriseanddistributioninthebearingunderdifferentconditions.Theseresultscanguidetheoptimizationofthebearingdesignandlubricationsystemtoimprovetheperformanceandreliabilityofmechanicalequipment.Anotherfactorthataffectsthethermalbehaviorofthebearingduringthestart-upprocessisthelubricationregime.Lubricationplaysacrucialroleinreducingfrictionandwearinbearings,particularlyunderhighloadsandspeeds.However,duringstart-up,thebearingmayexperienceinsufficientlubricationduetotheabsenceofahydrodynamicfilm,leadingtohigherfrictionandtemperaturerise.

Therefore,itisessentialtostudytheeffectofthelubricationregimeonthethermalbehaviorofthebearingduringstart-up.Theanalysiscanincludethestudyofvariouslubricationregimes,suchashydrodynamic,boundary,ormixedlubrication,andtheimpactoftheoilviscosity,oilflowrate,andoildistributiononthethermalbehaviorofthebearing.

Furthermore,thethermalbehaviorofthebearingduringstart-upisalsoaffectedbythespeedandloadofthemachine.Typically,higherspeedsandloadsleadtohighertemperatureriseandincreasedriskoffailure.Therefore,itisnecessarytoinvestigatethethermalbehaviorofbearingsundervariousspeedandloadconditionsduringstart-up.

Inconclusion,furtherstudiesareneededtoexaminetheinfluenceofvariousfactorsonthethermalbehaviorofthebearingduringstart-up,includingthegeometry,materialproperties,initialtemperature,lubricationregime,speed,andload.Theresultsofthesestudiescanprovideinsightsintothedesignandoperationofbearingsandimprovemachineperformanceandreliability.Apartfromthefactorsmentionedabove,thethermalbehaviorofthebearingduringstart-upcanalsobeimpactedbythesurfaceroughnessandcontactpressuredistribution.Theroughnessofthematingsurfacesaffectstheabilityofthelubricanttoformandmaintainahydrodynamicfilm,whichcanleadtoincreasedfrictionandtemperaturerise.

Contactpressuredistributionisanotherimportantfactorthatcanaffectthethermalbehaviorofthebearingduringstart-up.Unevendistributionofcontactpressurecanleadtolocalizedheatingandthermaloverloadingofthebearing.Therefore,itisessentialtoensureproperalignmentandpreloadinthebearingduringinstallationtominimizesuchunevenpressuredistribution.

Anotherfactorthatcanimpactthethermalbehaviorofthebearingduringstart-upisthethermalconductivityofthebearingmaterial.Materialswithhigherthermalconductivitycandissipateheatmorerapidlyandreducethetemperatureriseduringstart-up.Therefore,carefulselectionofbearingmaterialswithhighthermalconductivitycanensurebetterthermalperformanceduringstart-up.

Finally,theuseofadvancedmaterialsandcoatingscanalsoimprovethethermalperfor