汽车专业英语(幻灯片)chapter 3 engine(2.7)

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1、Differencesbetweendieselandgasolineengines:DieselenginegetsthisnamefromthepioneerworkdonebyDrRudolfDiesel.Thedieselisusedforthemajorityofheavyvehiclesandtheexcellentfueleconomymakesitanattractivealternativetothepetrolengineforlightcommercialvehicles,deliveryvansandtaxis.

2、柴油发动机的名称来源于RudolfDiesel博士所完成的开拓性工作。大多数重型车辆使用柴油，优良的燃油经济性使得柴油机成为最有吸引力的替代品,来代替轻型商用车、厢式货车和出租车上汽油机。Gasoline,keroseneanddieseloilareallproducefromnaturalpetroleum(crudeoil),andaredistinguishedmainlybytheirvolatility.Gasolineisquitevolatile,thatis,itevaporatesorvaporizesatalowt

3、emperature.Keroseneneedsmoreheattomakeitvaporize,whiledieseloilrequiresstillmoreheat.Bothtypesofenginesareinternal-combustionengines,thatis,theyburnthefuelinsidetheircylinders.汽油、煤油和柴油全都是从天然石油（原油）中提取出来的，通过挥发性可以把他们区分开。汽油易挥发，也就是，它在低温下蒸发或变成蒸汽。煤油需要较多热量才能挥发，而柴油需要更多热量。这两种发动机都是

4、内燃机，也就是，它们在汽缸内燃烧。Thedieselenginehasnothrottleplateorsimilardevicetorestrictairflowintotheengine.Enginespeediscontrolledonlybytheamountoffuelputintothecylinders.Forthisreason,adieselengineisanunthrottledengine.Agasolineenginehashighvacuumwhenthethrottleisclosed,andloworno

5、vacuumwhenthethrottleisopen.Adieselengine,becauseithasnothrottle,hasnointakemanifoldvacuum.柴油机没有节气门或类似装置控制进入发动机的气流。发动机速度仅由进入汽缸中的燃油量控制。因此，柴油机是无节气门发动机。当关闭节气门时汽油机真空度升高，打开节气门时真空度降低或没有真空。由于柴油发动机没有节气门，因而没有进气管真空度。Thefuelinjectionsystemisthemostimportantpartofthedieselengine.Die

6、selinjectionmustcontrolthequantityofthefuelinjectedanddeterminewhenitistobeinjected.Thetimingofthefuelinjectionisimportant,asisthesparktimingofagasolineengine.燃油喷射系统是柴油机的最重要的部分。柴油喷射必须控制燃油喷射量和决定喷射时间。燃油喷射时间象汽油机点火时间一样重要。Review1:ListthedifferencesbetweenDieselandGasolineengi

7、ne?Actualefficiencyηeffupto45%Actualefficiencyηeffupto30%Maximumcombustionpressure6~8MPaMaximumcombustionpressure3~5MPaCompressionratio14～24Compressionratio8～11alwaysgreaterthan1（excess-airfactor)from0.7to1.3Enginespeed1500to5000r/minEnginespeed4000to10000r/minIrregula

8、rmixtureinthecombustionchamberRegularmixtureinthecombustionchamberAuto-ignitionExternallysuppliedigniti