AutomotiveemissionandcontrolBeijingUniversityofCivilEngineeringandArchitectureChapter1:introduction2StudyAims學習目標：UnderstandtherelationofautomotiveandenvironmentKnowaboutthepollutionofmaincityinChinaRealizethedisadvantageofautomotiveemissionStudypoints知識要點：theenvironmentandautomotivethepollutionofmaincityinChinathedisadvantageofCO,NOx,HC,PM,CO2

Example:

3Readtheexamplesinbook.Wouldyouliketakeanexampleaboutpollution?1.1Airpollutionandvehicles1.1.1Airpollution

Airpollutionistheintroductionofparticulates,biologicalmolecules,orotherharmfulmaterialsintoEarth'satmosphere,causingdiseases,deathtohumans,anddamagetootherlivingorganisms.1.1.2SourcesTherearevariouslocations,activitiesorfactorswhichareresponsibleforreleasingpollutantsintotheatmosphere.Thesesourcescanbeclassifiedintotwomajorcategories.(1)Anthropogenic(man-made)sources:(2)Naturalsources:1.2Environmentalimpact

thepollutioninIranWhy？Fig1.3Wordmapofpassengercarsper1000peopleWordmapofpassengercarsper1000peoplethepollutionofmaincityinChinaWhatdoyouseefromthetable?1.3TypesofemissionsEmissionsthatareprincipalpollutantsofconcernincludeCO,HC,NOx,PMandCO2Nitrogenoxides

Nitrogenoxides

(NOx)-Generatedwhen

nitrogen

intheairreactswithoxygenatthehightemperatureandpressureinsidetheengine.NOx

isaprecursortosmogand

acidrain.NOx

isamixtureofNO,N2O,andNO2.NO2

isextremelyreactive.Itdestroysresistancetorespiratoryinfection.NOx

productionisincreasedwhenanenginerunsatitsmostefficient(i.e.hottest)partofthecycle.HydrocarbonsHydrocarbons-Aclassofburnedorpartiallyburnedfuel,hydrocarbonsaretoxins.Hydrocarbonsareamajorcontributortosmog,whichcanbeamajorprobleminurbanareas.TheformationofsmogTheformationofsmogHydrocarbonsProlongedexposuretohydrocarbonscontributestoasthma,liverdisease,lungdisease,andcancer.Regulationsgoverninghydrocarbonsvaryaccordingtotypeofengineandjurisdiction;insomecases,"non-methanehydrocarbons"areregulated,whileinothercases,"totalhydrocarbons"areregulated.HydrocarbonsTechnologyforoneapplication(tomeetanon-methanehydrocarbonstandard)maynotbesuitableforuseinanapplicationthathastomeetatotalhydrocarbonstandard.Methaneisnotdirectlytoxic,butismoredifficulttobreakdowninacatalyticconverter,soineffecta"non-methanehydrocarbon"regulationcanbeconsideredeasiertomeet.Sincemethaneisagreenhousegas,interestisrisinginhowtoeliminateemissionsofit.HydrocarbonsCarbonmonoxide

Carbonmonoxide

(CO)-Aproductofincompletecombustion,carbonmonoxidereducestheblood'sabilitytocarryoxygen;overexposure(carbonmonoxidepoisoning)maybefatal.CarbonMonoxidepoisoningisakillerinhighconcentrationsParticulatematterParticulatematter

–

Soot

orsmokemadeupofparticlesinthe

micrometre

sizerange:Particulatemattercausesnegativehealtheffects,includingbutnotlimitedto

respiratorydisease

and

cancer.Volatileorganiccompounds

(VOCs)Volatileorganiccompounds

(VOCs)-Organiccompoundswhichtypicallyhaveaboilingpointlessthanorequalto250

°C;forexample

chlorofluorocarbons

(CFCs)and

formaldehyde.

Volatileorganiccompounds

areasubsectionof

Hydrocarbons

thatarementionedseparatelybecauseoftheirdangerstopublichealth.Carbondioxide(CO2)

Carbondioxideisagreenhousegas.MotorvehicleCO2emissionsarepartoftheanthropogeniccontributiontothegrowthofCO2concentrationsintheatmospherewhichiscausingclimatechange.SulfuroxideSulfuroxide

(SOx)-Ageneraltermforoxidesof

sulfur,whichareemittedfrommotorvehiclesburningfuelcontainingsulfur.Reducingtheleveloffuelsulfurreducesthelevelof

Sulfuroxideemittedfromthetailpipe.Emissionsofmanyairpollutantshavebeenshowntohavevarietyofnegativeeffectsonpublichealthandthenaturalenvironment.1.4PollutionEffects

1.5Emissionfactors

1.6Pollutionreduction

ConclusionsThemainfactorofpollution–automotiveemissionbecauseofthecitydevelopment,energyusage,andsoon.TheheavypollutioninChina,andtheNorthisheavierthantheSouth.AutomotiveEmissionincludesmanydifferentcontents,suchasCO,HC,NOx,PMandCO2Thanks!Chapter2:MechanismonemissioncontrolFig2.1:CO2emissionprediction2.1GeneralprincipleFig2.2:Thesourceofgasolineengineemission2.1Generalprinciple2.1.1MeasuresforcontrollingemissionsSparkignitionengineAbasicessentialforsparkignitionengineemissioncontrolisaninjectionsystemcapableofextremeaccuracyinmeteringthefuelsupplyrelativetotheairenteringtheengine.(2)DieselengineDieselandsparkignitionenginesproducethesameemission.Ontheotherhand,owingtothelowvolatilityofdieselfuelrelativetothatofgasoline,evaporativeemissionsarenotsosignificant.2.1Generalprinciple2.1.2Reductionofemissions:conflictingrequirementsFig2.3NOxincreaseswhenmeasuresaretakentoreduceparticulatesindifferenttypesofengine2.2Oxidesofnitrogen,NOx2.2.1FormationandreactionsThethreeprincipalreactions(theextendedZeldovichmechanism)producingthermalNOxare:N2+O→NO+NN+O2→NO+ON+OH→NO+HAllthreereactionsarereversible.Zeldovichwasthefirsttosuggesttheimportanceofthefirsttworeactions.2.2Oxidesofnitrogen,NOx2.2.2NOxfromfuelItisestimatedthattransportationfuelscause54%oftheanthropogenic(i.e.human-caused)NOx.ThemajorsourceofNOxproductionfromnitrogen-bearingfuelssuchascertaincoalsandoil,istheconversionoffuelboundnitrogentoNoxduringcombustion.Althoughthecompletemechanismisnotfullyunderstood,therearetwoprimarypathsofformation.Thefirstinvolvestheoxidationofvolatilenitrogenspeciesduringtheinitialstagesofcombustion.Thesecondpathinvolvesthecombustionofnitrogencontainedinthecharmatrixduringthecombustionofthecharportionofthefuels.2.2Oxidesofnitrogen,NOx2.2.3EffectsoffuelpropertiesonNOx(1)IncreasingthecetanenumberFig2.4(left)TestsbyBPshowinghowinjectiontiminginfluencescombustionandthereforeNOxoutput;(right)theinfluenceofcetanenumberontheprincipalEmissions.2.2Oxidesofnitrogen,NOx(2)IncreasingfuelvolatilityFig2.5.NOxemissionswithdirectandindirectinjection2.2Oxidesofnitrogen,NOx(3)ExhaustgasrecirculationFig2.6.RelationshipbetweenfuelconsumptionandNOxemissionswith(left)andwithout(right)chargecooling.2.2Oxidesofnitrogen,NOx(4)Reductionoftherateofswirl

ReductionoftherateofswirlisanotherwayofreducingtheoutputofNOx.Itincreasesthetimerequiredforthefueltomixwiththeair,andthereforereducestheconcentrationofoxygenaroundthefueldroplets.Consequently,thetemperatureofcombustiondoesnotrisetosuchahighpeak.Again,however,italsoreducesthermalefficiency.Moreover,unlessmeasures,suchasincreasingthenumberofholesintheinjectornozzleandreducingtheirdiameter,aretakentoshortenthelengthsofthesprays,morefueltendstobedepositedonthecombustionchamberwalls.2.2Oxidesofnitrogen,NOx(4)Reductionoftherateofswirl

ReductionoftherateofswirlisanotherwayofreducingtheoutputofNOx.Itincreasesthetimerequiredforthefueltomixwiththeair,andthereforereducestheconcentrationofoxygenaroundthefueldroplets.Consequently,thetemperatureofcombustiondoesnotrisetosuchahighpeak.Again,however,italsoreducesthermalefficiency.Moreover,unlessmeasures,suchasincreasingthenumberofholesintheinjectornozzleandreducingtheirdiameter,aretakentoshortenthelengthsofthesprays,morefueltendstobedepositedonthecombustionchamberwalls.(5)Delayingthestartofinjection

Delayingthestartofinjectionhastheeffectofreducingpeaktemperatures,andthereforeNOx.Thisisbecausethecombustionprocessbuildsuptoitspeaklaterinthecycle,whenthepistonisonitsdownwardstrokeandthegasisthereforebeingcooledbyexpansion.However,togetafullchargeoffuelintothecylinderinthetimeremainingforittobecompletelyburnt,higherinjectionpressuresareneeded.Therefore,toavoidincreasingtheproportionoffuelsprayedontothecombustionchamberwalls,theholesintheinjectormustagainbesmallerindiameterandlargerinnumber.2.2Oxidesofnitrogen,NOx(6)TurbochargingwithchargecoolingTurbochargingincreasesthetemperatureofcombustionbyincreasingboththetemperatureandquantityofairenteringthecylinder.After-cooling,however,canhelpbyremovingtheheatgeneratedbybothcompressionofthegasandconductionfromtheturbine.Italsoincreasesthedensityofthecharge,andthereforethermalefficiencyandpoweroutput.Thenetoutcomeofturbochargingwithchargecooling,therefore,isgenerallyanincreaseor,atworst,noreductioninthermalefficiency.2.3Unburnthydrocarbons2.3.1MainreasonsHydrocarbons(HCs)intheexhaustaretheprincipalcauseoftheunpleasantsmellofadieselengine,thoughthelubricatingoilalsomakesasmallcontribution.Therearethreemainreasonsforthis.First,atlowtemperaturesandlightloads,themixturemaybetooleanforefficientburningsotheprecombustionprocessesduringtheignitiondelayperiodarepartiallyinhibited.Thisiswhysomeofthemixturesubsequentlyfailstoburn.Secondly,becauseofthelowvolatilityofdieselfuelrelativetopetrol,andtheshortperiodoftimeavailableforittoevaporatebeforecombustionbegins,HCsaregeneratedduringstartingandwarmingupfromcold.Thirdly,aftercoldstartingandduringwarm-up,ahigherthannormalproportionoftheinjectedfuel,failingtoevaporate,isdepositedonthecombustionchamberwalls.

2.3Unburnthydrocarbons

AnotherpotentialcauseofHCsisthefuelcontainedinthevolumebetweenthepintleneedleseatandthesprayholeorholes(thesacvolume).Aftertheinjectorneedlehasseatedandcombustionhasceased,someofthetrappedfuelmayevaporateintothecylinder.Finally,thecreviceareas,forexamplebetweenthepistonandcylinderwallsabovethetopring,alsocontainunburntorquenchedfractionsofsemi-burntmixture,Expandingundertheinfluenceofthehightemperaturesduetocombustionandfallingpressuresduringtheexpansionstroke,andforcedoutbythemotionsofthepistonandrings,thesevapoursandgasesfindtheirwayintotheexhaust.2.3Unburnthydrocarbons2.3.2WaystoreduceHCemissionsIngeneral,therefore,theenginedesignercanreduceHCemissionsinthreeways.Oneisbyincreasingthecompressionratio;secondly,thespecificloadingcanbeincreasedbyinstallingasmaller,morehighlyrated,engineforagiventypeofoperation;and,thirdly,byincreasingtherateofswirlbothtoevaporatethefuelmorerapidlyandtobringmoreoxygenintointimatecontactwithit.ReductionoflubricatingoilconsumptionisanotherimportantaimasregardsnotonlycontrolofHCsbutalso,andmoreimportantly,particulateemissions.Avoidanceofcylinder-boredistortioncanplayasignificantpartinthereductionof22oilconsumption.2.4CarbonmonoxideFig2.7:Model(left)andBall-and-stickmodel(right)ofcarbonmonoxide

Carbonmonoxideoccursinvariousnaturalandartificialenvironments.Exhaustfromautomobilesisabout100–200ppmvintypicalconcentrationspermillion.2.5ParticulateMatter2.5.1Definition

Particulatematter(PM)orparticulates–ismicroscopicsolidorliquidmattersuspendedintheEarth'satmosphere.Thetermaerosolcommonlyreferstotheparticulate/airmixture,asopposedtotheparticulatematteralone.Sourcesofparticulatemattercanbeman-madeornatural.Theyhaveimpactsonclimateandprecipitationthatadverselyaffecthumanhealth.Humanactivities,suchastheburningoffossilfuelsinvehicles,powerplantsandvariousindustrialprocessesalsogeneratesignificantamountsofparticulates.2.5ParticulateMatter2.5.2ControltechnologiesBetteratomizationofthefuelMeasuresappropriateforreducingthefuelandoilcontentoftheparticulatesarethesameasthosealreadymentionedinconnectionwithHCemissions,Theoverallquantityofparticulatescanbereducedbyincreasingtheinjectionpressureandreducingthesizeoftheinjectorholes,toatomisethefuelbetter.2.5ParticulateMatter(2)Reductionofthesulphurcontent

Reductionofthesulphurcontentofthefuelalsoreducesparticulates.Althoughtheproportionofsulphate+waterisshowninTable2.1asbeingonly2%ofthetotal,iftheinsolublesulphurcompoundsareadded,thistotalbecomesmorelike25%.Fig2.8Relationshipbetweenparticulateemissionsandfuelquality,asestablishedbyVolvo2.5ParticulateMatter(3)AningeniousmethodTable2.1ANALYSES,EXPRESSEDINPERCENTAGES,OFPARTICULATESFROMDIFFERENTTYPESOFDIESELENGINENote:Horrocks(FordMotorCo.)differentiatedbetweenthecarbonandotherash(at41%and13%respectively),makingthetotal44%.2.6InfluenceoffuelqualityondieselexhaustemissionsHowindividualemissionsareinfluencedbydifferentfuelpropertieshavebeensummarisedbytheUKPetroleumIndustryAssociationasfollows—

NOxIncreasesslightlywithcetanenumber.Decreasesasaromaticcontentislowered.CONosignificanteffects.HCDecreasesslightlyascetanenumberincreases.Decreaseswithdensity.Relationshipwithvolatilityinconsistent.BlacksmokeIncreaseswithfueldensityanddecreaseswitharomaticcontent.Isnotsignificantlyaffectedbyvolatility.Increaseswithinjectionretard(e.g.forreducingNOx).ParticulatesReducedasvolatilityislowered.Reducedascetanenumberislowered,thoughinconsistently.Unaffectedbyaromaticcontent.Reducedassulphurcontentislowered.2.7Blacksmoke

TheeffectofsulphurcontentontheformationofparticulateshasbeencoveredinSection2.5.Otherfactorsincludevolatilityandcetanenumber.Asregardsvisibility,however,thecarboncontentismuchmoresignificant.Thereasonisthateachengineisdesignedtooperateatmaximumefficiencyoveragivenrangeofspeedsandloadswithagivengradeoffuel.Therefore,atanygivenspeedandload,achangeoffuelmightincreasethecombustionefficiency,yetatanotherspeedandloadthesamechangemightreduceit.Thereasonwhythecetanenumberdoesnothaveasignificanteffectontheoutputofblacksmokeissimple.Itisthatsmokedensityislargelydeterminedduringtheburningofthelastfewdropsoffueltobeinjectedintothecombustionchamber.2.8WhitesmokeWhitesmokeisamixtureofpartiallyvaporiseddropletsofwaterandfuel,theformerbeingproductsofcombustionandthelatterarisingbecausethetemperatureofthedropletsfailstorisetothatneededforignition.Itcanbemeasuredbypassingtheexhaustthroughabox,onesideofwhichistransparentandtheotherpaintedmattblack.Abeamoflightisdirectedthroughthetransparentwallontothemattblacksurface.Ifthereisnowhitesmoke,nolightisreflectedbacktoasensoralongsidethelightsource;thedegreeofreflectionthereforeisafunctionofthedensityofthewhitesmoke.Fortestingfuels,thecriterionisthetimetaken,afterstartingfromaspecifiedlowtemperature,forthesmokeleveltoreducetoanacceptablelevel.Afterstartingat0°C,satisfactorysmokelevelsaregenerallyobtainablewithaDieselIndexof57andacetanenumberof53.5.Question:1WhatistheEffectsoffuelpropertiesonNOx?2WhatisthemainapproachestoreduceHCemissions?3Whataretheinfluenceoffuelqualityondieselexhaustemissions?4WhatisBlacksmoke?5WhatisWhitesmoke?Chapter3:ThereductionofGasolineengineemissions3.1CurrentstatusTheworld-wideconcernoverenvironmentalpollutionwithrespecttothegasolineenginebeganintheearly1940swhenLosAngelesresidentsbecameawareofanatmosphericphenomenonknownasphotochemicalsmog,showninFig3.2.3.1CurrentstatusCurrenttailpiperegulationsforgasolineenginesfocusoncarbonmonoxide(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-boardrefuelingvaporrecovery?5Howmanysimultaneoustasksdoesatwo-waycatalyticconverterhave?Andpleaseintroducethistasks.6Whatistheadvantageofathree-waycatalyticconverters?7Howmanysimultaneoustasksdoesathree-waycatalyticconverterhave?Andpleaseintroducethistasks.Chapter4:ThereductionofDieselenginesemissionQuestion:HowdodieselenginesreducetheNOxemission?4.1DieselenginesFig4.2Thecurrentandfutureemissionregulationsaroundtheworldforheavy-dutydieselengines.4.2AvailableControlTechnologiesFig4.3NOxandPMemissionlimits4.2AvailableControlTechnologiesTechnologiesdesignedtocontrolparticulatematter(PM)include:Dieseloxidationcatalysts(DOCs)Dieselparticulatefilters(DPFs)Closedcrankcaseventilation(CCV)Technologiesdesignedtocontroloxidesofnitrogen(NOx)include:Exhaustgasrecirculation(EGR)Selectivecatalyticreduction(SCR)LeanNOxcatalysts(LNCs)LeanNOxtraps(LNTs)4.2AvailableControlTechnologiesFig4.4.VOLVOD13KEuro6enginewithEGRandaftertreatmentmuffler4.2AvailableControlTechnologiesFig4.5DPF+DOC+EGR4.3ApproachesforReducingDieselEmissions4.3.1EngineControlsEnginemanufacturersstartedasearlyasthelateeightiestodevelopcleanerdieselenginesbyemployinganumberofstrategies.Theseapproachesincludeadvancedcommonrailfuelinjection,electronicenginecontrols,combustionchamber53modifications,airboosting,improvedair/fuelmixing,andreducedoilconsumption.Achievingultra-lowexhaustemissiontargetsrequiresasystemsapproach.Enginemanufacturersarefocusingonwaystocontrolengineoperationtoreduceengine-outemissionsaslowaspossibleandreducetheburdenontheexhaustemissioncontrolsystems.4.3ApproachesforReducingDieselEmissions4.3.2ExhaustControlsFig4.6:anExhaustControlssystem4.4IntelligentDieselEngineFig4.7IntelligentDieselEngine4.4IntelligentDieselEngineFig4.8HighpressurefuelinjectionsystemforanintelligentDieselEngine4.5Flow-ThroughDieselOxidationCatalysts4.5.1DieselOxidationCatalystFig4.9DiagramofaDieselOxidationCatalyst4.5Flow-ThroughDieselOxidationCatalysts4.5.2FilterRegenerationCatalysts4.5.3ImpactofSulfuronOxidationCatalystsNow,allU.S.heavy-dutydieselvehiclesmusthaveadieselparticulatefilter(DPF)intheexhaustsystemtoreducePMtobelow0.01g/bhp-hr.TheDPFwillbedescribedingreaterdetaillaterinthisreport.AnessentialpartoftheproperfunctioningofanyDPFsystemreliesonaprescribedregenerationtooccasionallyburnsootcollectedinthefilterandreducethebackpressureoftheexhauststream.CatalystformulationshavebeendevelopedwhichselectivelyoxidizetheSOFwhileminimizingoxidationofthesulfurdioxide.However,thelowerthesulfurcontentinthefuel,thegreatertheopportunitytomaximizetheeffectivenessofoxidationcatalysttechnologyforbothbettertotalcontrolofPMandgreatercontroloftoxicHCs.4.6ParticulateFilters4.6.1OperatingCharacteristicsandControlCapabilities(1)ClosedCrankcaseVentilationFig4.10ClosedCrankcaseEmissionControlSystem4.6ParticulateFilters(2)Flow-ThroughorPartialDieselParticulateFiltersFig4.11Metallicflow-throughfiltermadeupofcorrugatedmetalfoilandlayersofporousmetalfleece.4.6ParticulateFilters4.6.2HighEfficiencyFiltersFig4.12DiagramofaWall-FlowDieselParticulateFilter.4.6ParticulateFiltersFig4.13Pressuredropacrossawall-flowDPFloadedwith4g/lofsootasafunctionofpercentwallporosityandrelativelevelofporeconnectivityforcatalyzedanduncatalyzedfilters.4.7FilterRegeneration4.7.1PassiveRegenerationThesimplesttypeoffilterisknownasapassivedesignbecauseitrequiresnodriverorengineinterventiontocombustthesootonthefilter.Inthiscasetheceramicormetalfiltersubstrateiscoatedwithahighsurfaceareaoxideandpreciousorbasemetalcatalyst.4.7.2ActiveRegenerationActivelyregenerated,high-efficiencyfiltersystemscanbeappliedtoamuchlargerrangeofapplications.Becauseofaddedcomplexityneededtoexpandtherange,theyaregenerallymoreexpensivethanpassivefilters.Someoftheactivetechnologyoptionsareburners(someoperatewhiletheengineisrunning,otherswhiletheengineisturnedoff),injectionofdieselfuelintotheexhauststreamforoxidationacrossaDOCupstreamoftheD