汽车专业英语 教学课件 作者 宋进桂汽车专业英语课件-section 1Chapter 2-7.ppt

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1、Chapter2InternalCombustionEngine2.7GasolinedirectinjectionNewWordsdrastic['dræstik]a.剧烈的，猛烈的response[ri'spɔns]n.反应，响应efficiency[i'fiʃənsi]n.效率，效能，有效性ultra-lean['ʌltrə'li:n]a.极端稀薄的，超稀薄deploy[di'plɔi]v.展开，部署homogeneous[hɔmə'ʤi:njəs]a.相似的，均匀的stratify['strætifai]a.(使)成层，（使）分层Chapter2Inte

2、rnalCombustionEngine2.7GasolinedirectinjectionAlthoughMPIprovidesadrasticimprovementinresponseandcombustionquality,itisstilllimitedduetofuelandairmixingpriortoenteringthecylinder.Tofurtherincreasethrottleresponseandcombustionefficiency,whileloweringfuelconsumptionandincreasingoutput,

3、systemsmayusedirectinjection.Gasolinedirectinjectionenginesareengineeredtoinjectthegasolinedirectlyintothecylinderinamannersimilartodieseldirectinjectionengines(Fig.2-14).Directinjectionisdesignedtogetbetterfueleconomy.Thisisaccomplishedbyenablingcombustionofanultra-leanmixtureunderma

4、nyoperatingconditions.Directinjectionisalsodesignedtoallowhighercompressionratios,deliveringhigherperformancewithlowerfuelconsumption.Currently,directinjectiongasolineenginesarebeingdeployedthroughouttheworldinpassengercars.Chapter2InternalCombustionEngine2.7GasolinedirectinjectionFi

5、g.2-14GasolinedirectinjectionAvarietyofair-fuelmixturescanbecreatedaccordingtochangesinthefuelinjectiontiming.TheGDIengineprovidesbothlowerfuelconsumptionandhigheroutput.Thisisachievedwiththeuseoftwocombustionmodes.ThesetwomodesarerepresentedinFigure2-15.Chapter2InternalCombustionEngi

6、ne2.7GasolinedirectinjectionFigure2-15MitsubishiGDIusestwocombustionmodesChapter2InternalCombustionEngine2.7GasolinedirectinjectionUltra-leanCombustionMode.Undermostnormaldrivingconditions,uptospeedsof120km/h,theMitsubishiGDIengineoperatesinultra-leancombustionmode,resultinginlessfu

7、elconsumption.Inthismode,fuelinjectionoccursatthelatterstageofthecompressionstrokeandignitionoccursatanultra-leanair-fuelratioof30-40.Thisoperatingmodeisalsocalledasstratified-chargemode.SuperiorOutputMode.WhentheGDIengineisoperatingwithhigherloadsorathigherspeeds,fuelinjectiontakespl

8、acedu