F.Zhangetal./ProceedingsoftheCombustionInstitute33(2011)3151–31583157

inFig.8.Themolefractioninthisphaseisthecombinationofburnedareaandunburnedarearesults.SeenfromFig.8,formaldehydeisgradu-allygeneratedafterthestartofthecombustion.After0°CAthereisacertainamountofformal-dehydeconsumptionduetothetemperaturerise.ThemodelsetsthattheintakeairstartsatÀ368°CA.Atthistimethemolefractionofform-aldehydereducesduetothechargeoffreshair.AstheendoftheintakeprocessatÀ120°CA,thelowtemperatureoxidationofmethanolreactiontakesplaceinthecylinder.Thus,someofformaldehydebeginstogenerate.Meanwhile,theamountofgen-eratedformaldehydealsoincreaseswiththemetha-nolproportioninmethanol-gasolineblendedfuelsincreasing.Afterthestartofthemixturecombus-tionthecylinderformaldehydestartstoquicklygenerateandthendecreasesbytherapidoxidation.Figure9givesthecomparisonsbetweensimulatedandexperimentalformaldehydeemissionsfromdi erent-contentmethanol-gasolineblendedfuels.AsshowninFig.9,formaldehydeemissionshaveanearlylineargrowthwiththeincreaseofthemeth-anolproportion.TheexperimentaldatafromtheSIenginewereobtainedbytheFTIRspectrometer.Themaximumerrorbetweensimulatedandexper-imentalvaluesofpuregasoline,M10,M20,andM30islessthan50%.Thesimulationresultsachieveagoodconsistencywiththeexperimentalresults.

Theexperimentsusinghighpercentageofmethanol-gasolineblendedfuelsarerestrictedbythefactoroffuelinjectionpulsewidth.Thus,usingtheestablishedenginemodelcanprovideapredic-tionontheformaldehydeemissionsofhigh-contentmethanol-gasoline,asshowninFig.10.Itindicatesthatthehigh-contentmethanol-gasolineblendedfuelgeneratesalargeamountofformalde-hydeemission,about6–8timeshigherthangasoline.

5.Conclusions

Inthisstudy,adetailedcomprehensivemetha-noloxidationmechanismwasdeveloped,basedonpresentreactionrateconstantandpathinfor-mation.Thein uenceofCH,CHnitricoxide2(S),andCH2(T)radicalspeciesandwascon-sideredinthemechanism.Shock-tubeand ow-reactordatawereusedtovalidatethemechanism.Numericalsimulationsofallsystemswerecon-ductedbyCHEMKIN-basedprograms.Inordertoconstructamethanol-gasolinemechanism,anoxidationmechanismofgasolinesurrogatewascombinedwiththemethanolmechanism.Thegas-olinesurrogatemechanismwasformedwithiso-octane,toluene,and1-hexene.Themethanol-gaso-linemechanismwasvalidatedbythejet-stirredreactorexperimentdata.Thesimulationresultsoftheproposedmechanismhaveagenerallygoodagreementwiththeexperimentaldata.Sequen-tially,theBoostenginecyclemodelwasestablishedandcoupledwiththemethanol-gasolinemecha-nismtosimulatetheformaldehydeemissionsofthelow-percentmethanol-gasolineblendedfuelsfromaSIengine,andalsoappliedtopredicttheemissionsofthehigh-percentblendedfuels.ThesimulationresultsofSIenginesachieveagoodcon-sistencywiththeexperimentalresults.Acknowledgments

Thisworkwas nanciallysupportedbytheNationalHighTechnologyResearchandDevel-opmentProgramofChina(“863”Program)“AdaptabilityResearchonMethanolVehicle”,underGrant2006AA11A1A4.AppendixA.Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound,intheonlineversion,atdoi:10.1016/j.proci.2010.07.029.

3158F.Zhangetal./ProceedingsoftheCombustionInstitute33(2011)3151–3158

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