《汽车专业英语》课件第2章.ppt

SealingHighcombustionpressuresareencountered.Pistonringsrequireanoilfilmbetweenringandlinerandbetweenringandpistongroovetosealagainstthesehighpressuresandtopreventblowby.CoolingTheengineoilislargelyresponsibleforpistoncooling.Thisisdonebydirectheattransferthroughtheoilfilmtothecylinderwallsandontothecoolingsystem.Heatisalsocarriedbytheoilfromtheundercrownandskirttothecrankcase.Thermallystableoilsarerequiredtowithstandthehightemperaturesencountered.DepositControlRingsmustremainfreetofunctionproperlyandtomaintainagoodseal.Depositbuildupintheringgroovesandonpistonlandsmustthereforebecontrolled.VarnishControlEngineparts,particularlythepiston,mustbekeptfreeofvarnishtoensureperformanceandpropercooling.SludgeControlHighandlow-temperaturesludge-formingontaminantsmustbeheldinsuspensionandnotallowedtodropoutandaccumulate.Thelargerparticlesareremovedbythefilter.Sludgeandabrasivesareremovedwiththeoilwhendrained.BearingProtectionOilbreakdownandcorrosiveproductsofcombustioncancausebearingcorrosion.Theadditivesintheoilcounteractthisactionbyminimizingbreakdown,neutralizingblowbyproducts,andhelpingtoformaprotectivefilm.RustControlEnginecomponentsincludingvalvelifters,valvestems,rings,cylinderwall,etc.,aresubjectedtosevererust-promotingconditions,particularlyinwinterstop-and-godriving.Rustingiscontrolledbyoilformulation.RadiatorAradiatorisatypeofheatexchanger.Itisdesignedtotransferheatfromthehotcoolantthatflowsthroughittotheairblownthroughitbythefan.Mostmoderncarsusealuminumradiators.Theseradiatorsaremadebybrazingthinaluminumfinstoflattenedaluminumtubes.Thecoolantflowsfromtheinlettotheoutletthroughmanytubesmountedinaparallelarrangement.Thefinsc