排气控制系统外文文献翻译中英文翻译外文翻译Word下载.docx

排气控制系统外文文献翻译中英文翻译外文翻译Word下载.docx

《排气控制系统外文文献翻译中英文翻译外文翻译Word下载.docx》由会员分享，可在线阅读，更多相关《排气控制系统外文文献翻译中英文翻译外文翻译Word下载.docx（7页珍藏版）》请在冰豆网上搜索。

EmissionControlSystems

Thepurposeoftheemissionsystemisjustthatitcontrolstheemissionandexhaustfromavehicle.Theideaistoturntheharmfulgasesacarmanufacturesintoharmlessonesthatdon'

truintheenvironment,orpersons.Someofproblemgasesare:

1.hydrocarbons（unburned）.

2.Carbonmonoxide.

3.Carbondioxide

4.Nitrogenoxide.

5.Sulfurdioxide.

6.Phosphorus.

7.Leadandothermetal.

Therearefivepopularsystemsusedtoreduceemissions:

thecrankcaseventilationsystem,theevaporativeemissionscontrolsystem,theexhaustgasrecirculationsystemandthecatalyticconvertersystem.Inadditionaltotheseemissionssystem,somevehiclesincorporateanelectronicallycontrolledfuelsystem,whichfurtherreducesemissions.

Note:

Notallvehiclesareequippedwiththeseemissionsystems.

Crankcaseventilationsystem

Sincetheearly1960s,allcarshavebeenequippedwithcrankcaseventilationsystem.

Whentheengineisrunning,asmallportionofthegaseswhichareformedinthecombustionchamberleakpasthepistonringsandenterthecrankcase.Sincethesegasesareunderpressure,theytendtoescapefromthecrankcaseandentertheatmosphere.ifthesegasesareallowedtoremaininthecrankcaseforanylengthoftime,theycontaminatetheengineoilandcausesludgetobuildupinthecrankcase.Ifthegasesareallowedtoescapetotheatmosphere,theypollutetheairwithunburnedhydrocarbons.Thejobofthecrankcaseventilationsystemistorecycletheegasesbackintotheenginecombustionchamberwheretheyarere-burned.

Thecrankcasegasesarerecycledastheengineisrunningbydrawingcleanfilteredairthroughtheairfilterandintothecrankcase.Astheyarepassesthroughthecrankcase,itpicksupthecombustiongasesandcarriesthemoutofthecrankcase,throughtheoilseparator,throughthePCVvalveororifice,andintotheinductionsystem.astheyentertheintakemanifold,theyaredrawnintothecombustionchamberwheretheyarere-burned.

ThemostcriticalcomponentinthesystemisthePCVvalvethatcontrolstheamountofgasesthatarerecycled.Atlowenginespeedincreases,thevalveopenstoadmitgreaterquantitiesofairtotheintakemanifold.SomesystemsdonotuseaPCVvalve.Theysimplyusearestrictorororificeintheventilationhosetometerthecrankcasegases.

IfthePCVvalvebecomesblockedorplugged,thegasescannotbeventedfromthecrankcase.Sincetheyareunderpressure,theyillfindtheirownwayoutofthecrankcase.Thisalternaterouteisusuallyaweakoilsealorgasketintheengine.Asthegasescapesbythegasket,itusuallycreatesanoilleak.Besidescausingoilleaks,acloggedPCVvalvealsoallowsthesegasestoremaininthecrankcaseforanextendedperiod,promotingtheformationofsludgeintheengine.

Evaporativeemissioncontrolsystem

Theevaporativeemissioncontrolsystemisdesignedtopreventfueltankandcarburettorbowlvapoursfrombeingemittedintotheatmosphere.Fuelvapoursareabsorbedandstoredbyafuelvapourcharcoalcanister.Thecanisterstoresthemuntilcertainengineconditionsaremetandthevapourscanbepurgedandburnedbytheengine.

Thecharcoalcanisterpurgecycleiscontrolleddifferentways:

eitherbyathermostaticvacuumswitch,asolenoidorbyatimedvacuumsource.Thethermostaticswitchisinstalledinthecoolantpassageandpreventscanisterpurgewhentheengineisbelowacertaintemperature.Thesolenoidisusuallycontrolledbyacomputerandisusedonfeedbackfuelsystems.Thecomputerdetermineswhencanisterpurgeisappropriate.Dependingonthesystem,thiscanbeengineoperatingtemperature,enginespeed,evaporativesystempressureoranycombinationofthese.Thetimedvacuumsourceusesamanifoldvacuumcontrolleddiaphragmocontrolcanisterpurge.Whentheengineisrunning,fullmanifoldvacuumisappliedtothetoptubeofthepurgevalvewhichliftsthevalvediaphragmandopensthevalve.

Aventlocatedinthefueltank,allowsfuelvapourstoflowtothecharcoalcanister.atankpressurecontrolvalve,usedonsomehighaltitudeapplications,preventscanisterpurgewhentheengineisnotrunning.Thefueltankcapdoesnotnormallyventtotheatmosphere,butisdesignedtoprovidebothvacuumandpressurerelief.

Airinjectionsystem

Introducingacontrolledamountofairintotheexhaustsystempromotesfurtheroxidationofthegases.Thisinturnreducestheamountofcarbonmonoxideandwater,theharmlessby-productsofcombustion.Somesystemuseanairpump,whileotherusenegativeexhaustpulsestodrawair.

Theairpump,usuallydrivenbyabelt,simplypumpsairunderapressureofonlyafewpoundsintoeachexhaustport.Betweenthenozzlesandthepumpisacheckvalvetokeepthehotexhaustgasesfromflowingbackintothepumpandhosestherebydestroyin