汽車新能源與排放控制（雙語教學(xué)版）Chapter 3-修改

Chapter3:ThereductionofGasolineengineemissions3.1CurrentstatusTheworld-wideconcernoverenvironmentalpollutionwithrespecttothegasolineenginebeganintheearly1940swhenLosAngelesresidentsbecameawareofanatmosphericphenomenonknownasphotochemicalsmog,showninFigCurrentstatusCurrenttailpiperegulationsforgasolineenginesfocusoncarbonmonoxide(CO),theoxidesofnitrogen(collectivelycalledNOx)andhydrocarbons(HC).Thesestandardshavebecomeincreasinglystringentsincetheirintroductioninthe1960's.ThisisdemonstratedinFig3.3,whichshowsthechangeinHCemissionsfromgasolinepoweredvehiclesintheUnitedStatessince1966.Fig3.3HCemissionstandardshavechangeddramatically3.2Tailpipeemissioncontrol3.2.1GasolineEnginesFig3.4TWCconversionefficiencyvarieswithA/F.EfficientsimultaneousconversionofCO,HCandNOxoccursonlynearstoichiometry3.2Tailpipeemissioncontrol(1)A/FControlFig3.5ThisschematicrepresentsatypicalA/Fcontrolalgorithm.Inthiscase,feedforwardcontrolisbasedonanairflowmetermeasurementandfeedbackisimplementedwithaHEGOsensor3.2Tailpipeemissioncontrol(2)ColdStart(3)partiallyzeroemissionsvehicle(PZEV)(4)LeanBurningGasolineEngines3.2TailpipeemissioncontrolFig3.7Theelectroniccontrolsystem1-fueltank2-fulefilter3-fuelpressureregulator4-injector5-airfilter6-watertemperaturesensor7-ildercontrolvalve8-ailmass-flowsensor9-oxygensensor10-ECUcontroller(5)Theelectroniccontrolsystem3.2Tailpipeemissioncontrol(6)Warm-airintakesystems(7)GasolinedirectinjectionFig3.8:GDIengine3.2Tailpipeemissioncontrol3.2.2Aftertreatment(1)CatalyticconversionAcatalyticconversionisanemissionscontroldevicethatconvertstoxicpollutantsinexhaustgastolesstoxicpollutantsbycatalyzingaredoxreaction(oxidationorreduction).(2)Two-waycatalyticconversionAtwo-way(or"oxidation")catalyticconverterhastwosimultaneoustasks:(1)Oxidationofcarbonmonoxidetocarbondioxide:2CO+O2→2CO2(2)Oxidationofhydrocarbons(unburnedandpartiallyburnedfuel)tocarbondioxideandwater:CxH2x+2+[(3x+1)/2]O2→xCO2+(x+1)H2O(acombustionreaction)3.2Tailpipeemissioncontrol(3)TheconverterFig.3.9:Thestainlesssteelhousingformonolithiccatalystcarriers3.2Tailpipeemissioncontrol(4)CatalystsupportFig3.10:Twomonolithiccatalystcarriersbeingassembledinseriesintotheircasing3.2Tailpipeemissioncontrol(5)MetallicmonolithsforcatalyticconvertersFig3.11Comparisonbetweenceramicandmetallicmonoliths3.2TailpipeemissioncontrolTable3.1METALANDCERAMICMONOLITHMATERIALSCOMPAREDNote:Thicknessesandcross-sectionsareofmetalsuncoatedwithcataly3.2Tailpipeemissioncontrol(6)Three-waycatalyticconvertersFig3.12Three-waycatalyticconverters3.2TailpipeemissioncontrolAthree-waycatalyticconverterhasthreesimultaneoustasks:1.Reductionofnitrogenoxidestonitrogenandoxygen:2NOx→xO2+N22.Oxidationofcarbonmonoxidetocarbondioxide:2CO+O2→2CO23.Oxidationofunburnthydrocarbons(HC)tocarbondioxideandwater:CxH2x+2+[(3x+1)/2]O2→xCO2+(x+1)H2O.Fig3.13Typicalefficiencyofathree-waycat3.2TailpipeemissioncontrolFig3.14Oxygensensorlocation3.2TailpipeemissioncontrolFig3.15DifferenceofOxygensensor3.3EvaporativeemissionsFig3.16Evaporativeemission3.3EvaporativeemissionsTheevaporativeemissions(asshowninFig3.16)aremostlyhydrocarbonsthough,withsomespecialfuelsandthosethathavebeenmodifiedtoincreaseoctanenumber,alcoholsmayalsobepresent.Ingeneral,thevapourcomesfromfoursources—(1)Fueltankventingsystem.(2)Permeationthroughthewallsofplasticstanks.(3)Throughthecrankcasebreather.Permeationthroughthewallsofplasticstanksiscontrolledbyoneoffourmethods.Theseare—(1)Fluorinetreatment.(2)Sulphurtrioxidetreatment.(3)DuPontone-shotinjectionmoulding(alaminarbarriertreatment).(4)PremierFuelSystemsmethodoflamination.3.3EvaporativeemissionsFig3.17Evaporativeemissioncontrolsystem3.4CrankcaseemissioncontrolFig3.18positiveventilationsystemFig.3.19AC-Delcocrankcaseventilationcontrolvalve.Withzerodepressioninthemanifold,thevalveseatsontheright-handorificeandwithmaximumdepressionontheleft-handone.3.4Crankcaseemissioncontrol(a)(b)(c)(d)Fig3.20:Airflowatdifferentcondition3.5On-boardrefuelingvaporrecovery3.5.1GeneralOn-boardrefuelingvaporrecovery(ORVR)isavehicleemissioncontrolsystemthatcapturesfuelvaporsfromthevehiclegastankduringrefueling.Thegastankandfillpipearedesignedsothatwhenrefuelingthevehicle,fuelvaporsinthegastanktraveltoanactivatedcarbonpackedcanister,whichadsorbsthevapor.Whentheengineisinoperation,itdrawsthegasolinevaporsintotheengineintakemanifoldtobeusedasfuel.3.5On-boardrefuelingvaporrecovery3.5.2Operation(1)WhiledrivingFig3.21Schematicdiagramwhiledriving3.5On-boardrefuelingvaporrecovery(2)WhilerefuelingFig3.21SchematicdiagramwhilerefuelingQuestion:

1WhatisA/Fcontrol?2Pleasesummarytheprincipleoftheelectroniccontrolsystem.3Wherethevaporofevaporativeemissionscomefrom?4WhatisOn-boardrefuelingv