车辆工程专业英语PPT课件-UNIT-7--EMISSION-CONTROL-SYSTEMS

No.10039UNIT7EMISSIONCONTROLSYSTEMSTEXTAOverviewofEmissionControlSystemsPROFESSIONALENGLISHNo.10039UNIT7EMISSIONCONTROLSYSTEMSTEXTAOverviewofEmissionControlSystemsPCVSystemEGRSystemEvaporativeControlSystemAirInjectionCatalyticConverterPROFESSIONALENGLISHNo.10039本次课学习目标掌握排放控制系统的组成掌握排放控制系统的原理掌握有关的英文专业术语了解翻译技巧—重复NEWWORDSdilute[dai'lju:t]v.冲淡,变淡,变弱,稀释crossover['krɔsֽouvə]n.转线路,天桥,交叉channel['t∫ænl]n.海峡，水道，信道，频道，通道route[ru:t]n.路线,路程,通道；v.发送lean（out）[li:n]v.贫化，变瘦thermal['θə:məl]a.热的,热量的transducer[trænz'dju:sə]n.传感器，变频器，变换器orifice['ɔrifis]n.孔，口，节流孔linear['liniə]a.线的,直线的,线性的potentiometer[pəֽten∫i'ɔmitə]n.电位计,电势计fume[fju:m]n.(浓烈或难闻的)烟,气体；v.用烟熏,冒烟,发怒prohibit[prə'hibit]v.禁止,阻止adhere[əd'hiə]v.粘附,胶着,坚持pop[pɔp]n.砰的一声,爆裂声,流行乐曲,流行艺术a.流行的,热门的,通俗的v.发出爆裂声,爆开,射击,突然出现diverter[dai'və:tə]n.分流器，换向器，分流阀divert[di'və:t]v.转移,转向catalytic[ֽkætə'litik]a.催化的muffler['mʌflə]n.消声器pellet['pelit]n.小球honeycomb['hʌnikoum]n.蜂房，蜂巢platinum['plætinəm]n.白金,铂palladium[pə'leidiəm]n.钯catalyst['kætəlist]n.催化剂render['rendə]v.致使，表演，实施PHRASESANDEXPRESSIONS脉宽调制pulsewidthmodulationEGR阀位置（EVP）传感器EGRvalveposition(EVP)sensor锥形端taperedtip通气孔bleedport背压backpressure大节气门开度（简写为WOT）wide-openthrottle废气再循环阀EGRvalve节气门开度throttleopening在最坏的情况下atworst空气喷射airinjection催化转换器catalyticconverter空气泵airpump分流阀divertervalve清污阀purgevalve与…一道（同时），以及，除…之外（还）alongwith活性炭罐charcoalcanisterOverviewofEmissionControlSystemsTominimizepollutionoftheatmospherefromincompletelyburnedandevaporatinggasesandtomaintaingooddriveabilityandfueleconomy,anumberofemissioncontrolsystemsareusedonallvehicles.Theyincludepositivecrankcaseventilation(PCV)system，evaporativeemissioncontrol(EVAP)system，exhaustgasrecirculation(EGR)system，airinjection(AIR)systemandthree-waycatalyticconverter(TWC)system.PCVSystemThepurposeofthepositivecrankcaseventilation(PCV)systemistotakethevaporsproducedinthecrankcaseandpistonblow-by,andredirectthemintotheair/fuelintakesystemtobeburnedduringcombustion.Thesevaporsdilutetheair/fuelmixture,theyhavetobecarefullycontrolledandmeteredsoasnottoaffecttheperformanceoftheengine.Thisisthejobofthepositivecrankcaseventilation(PCV)valve.Atidle,whentheair/fuelmixtureisverycritical,justalittleofthevaporsareallowedintotheintakesystem.Athighspeedwhenthemixtureislesscriticalandthepressuresintheenginearegreater,moreofthevaporsareallowedintotheintakesystem[1].Whenthevalveorthesystemisclogged,vaporswillbackupintotheairfilterhousingoratworst,theexcesspressurewillpushpastsealsandcreateengineoilleaks[2].Ifthewrongvalveisusedorthesystemhasairleaks,theenginewillidlerough,oratworstengineoilwillbesuckedoutoftheengine.EGRSystemExhaustgasrecirculation(EGR)systemsreducetheamountofoxidesofnitrogenproducedduringthecombustionprocess.TheEGRsystemdilutestheair/fuelmixturewithcontrolledamountsofexhaustgas.Sinceexhaustgasdoesnotburn,thisreducesthepeakcombustiontemperatures.Atlowercombustiontemperatures,verylittleofthenitrogenintheairwillcombinewithoxygentoformNOX.Mostofthenitrogenissimplycarriedoutwiththeexhaustgases.Fordriveability,itisdesirabletohavetheEGRvalveopening(andtheamountofgasflow)proportionaltothethrottleopening.DriveabilityisalsoimprovedbyshuttingofftheEGRwhentheengineisstartedupcold,atidle,andatfullthrottle.SincetheNOXcontrolrequirementsvaryondifferentengines,thereareseveraldifferentsystemswithvariouscontrolstoprovidethesefunctions.EGRValvesMostofthesesystemsuseavacuum-operatedEGRvalvetoregulatetheexhaustgasflowintotheintakemanifold.Exhaustcrossoverpassagesundertheintakemanifoldchanneltheexhaustgastothevalve.(Somein-lineenginesroutetheexhaustgastothevalvethroughanexternaltube.)TypicalmountingoftheEGRvalveiseitheronaplateunderthecarburetorordirectlyonthemanifold.TheEGRvalveisavacuum-operated,flowcontrolvalve.OpeningtheEGRvalvebycontrolvacuumatthediaphragm,allowsexhaustgasestoflowthroughthevalveandintotheintakemanifold.Here,theexhaustgasmixeswiththeair/fuelmixture.Theeffectistodiluteorleanoutthemixture,sothatitstillburnscompletelybutwithareductionincombustionchambertemperatures.TherearealsovariousdesignsofEGRvalves.ThepositivebackpressureEGRvalvehasableedportandvalvepositionedinthecenterofthediaphragm.Alightspringholdsthisbleedvalveopen,andanexhaustpassageisconnectedfromthelowerendofthetaperedvalvethroughthestemtothebleedvalve.Whentheengineisrunning,exhaustpressureisappliedtothebleedvalve.Atlowenginespeeds,exhaustpressureisnothighenoughtoclosethebleedvalve.Ifcontrolvacuumissuppliedtothediaphragmchamber,thevacuumisbledoffthroughthebleedport,andthevalveremainsclosed.（略）InanegativebackpressureEGRvalve,anormallyclosedbleedportispositionedinthecenterofthediaphragm.Anexhaustpassageisconnectedfromthelowerendofthetaperedvalvethroughthestemtothebleedvalve.Whentheengineisrunningatlowerspeeds,thereisahigh-pressurepulseintheexhaustsystem.However,betweenthesehigh-pressurepulsestherearelow-pressurepulses.Astheenginespeedincreases,morecylinderfiringsoccurinagiventime,andthehigh-pressurepulsesbecomeclosertogetherintheexhaustsystem.（略）AdigitalEGRvalvecontainsuptothreeelectricsolenoidsthatareoperateddirectlybythePCM.E