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1、IntroductionMarinedieselengineisthemostwidelyusedengineinships.Comparedwithgasolineengine,marinedieselenginehashigherthermalefficiencyandismoreeconomical.Oilfeedingsystemofmarinedieselengineissimplerthangasolineenginesothatmarinedieselengineissteadierand
2、haslessmaintenancecost.MarinedieselenginealsohaslowerspecificfueloilconsumptionandCO2emissionwhichisconsideredthemainreasonofgreenhouseeffect.However,thereisaproblemlimitstheuseofmarinedieselengine.ThatistheNOxemission.Marinedieselengineisthemainairpollu
3、tionsourceofportandsea.NOxisageneraltermofnitrogenoxideswhichmainlycontainsNOandNO2etc.AccordingtoZeldovichmechanism,inhightemperatureandpressurecondition,nitrogenwillreactwithoxygenandbecomeNOx.Actually,inNOxproducedfromcombustioninmarinedieselengine,90
4、%contentsofNOxisNOand10%isNO2.Everyyear,peoplewillproduceover100milliontonnesofNOx,andit’sahugepollutiontotheair.Forexample,whenasupersonicairplanefliesthroughthestratosphere,itwillmakealotofNOxfromengine,andNOxwillbeharmfultoOzonelayer.NOxisalsothereaso
5、nofacidrainandrespiratorydiseaseespeciallytolungandcardiacmuscle.Therefore,someexpertssaidNOxwasmoredangerousthanSOx.Sincetheindustrialrevolutionbrakeout,pollutionhasbeenabigproblemgradually.Fortunately,humanhasrealizedtheimportanceofenvironmentprotectio
6、n.Althoughit’snotavailabletomakeenginezerorelease,manycompaniesandorganizationsaretryingtocontrolengineemission.Somestringentexhaustgasregulationshascomeintoeffectandtechnologiesanddevelopmentshavebeenadvancedtoreducedieselexhaustemissions.IMOpublishedMA
7、RPOL73/78,AnnexVItolimittheemissionin1997andadvancednewrequirementsin2008.TierDateNOxlimit,g/kwhn<130130 ≤ n < 2000n≥2000TierI200017.045·n-0.29.8TierII201114.444·n-0.237.7TierIII20163.49·n-0.21.96Fig.1Hence,themarineindustryisunderinternationalregulation
8、,andtherehavebeenmanywaystocontrolNOxemissionlikefuelvalveandnozzleoptimisation,WaterEmulsification,ExhaustGasRecirculation(EGR),andSelectiveCatalyticReduction(SCR)ect.AimsoftheprojectAirpollutionisabigproblemtodayandNOxem
