高职高专汽车专业英语

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1、书名：汽车专业英语ISBN：978-7-111-42342-3作者：卢晓春出版社：机械工业出版社本书配有电子课件Task1TheOperationCycleofanEngineParagraphAtpresent,themostautomobileusesaninternalcombustionengineintheworld.Whatisaninternalcombustionengine?Howdoestheinternalcombustionenginework?EngineConstructionFourstrokesThemostcommonengineisthefo

2、ur-strokepistonengine．Thesefourstrokesareintakestroke,compressionstroke，powerstrokeandexhauststroke.IntakeStrokeTheintakestrokeofafour-strokeenginebeginswiththepistonattopdeadcenter(TDC)．Thestartercausesthecrankshafttorotateinaclockwisedirection（Fig.2-3）．Thecrankshaft，throughtheconnectingrod，

3、forcesthepistontomovedownward．Thisdownwardmovementofthepistoncreatesavacuum，adifferenceinpressure，inthespaceabovethepiston．Theenginemanufacturertimestheintakevalveactionsothatitopensautomaticallyatorslightlybeforethepistonstartsdown．Therefore,amixtureofgasolineandair，pushedbytheatmosphericpre

4、ssureoutsidetheengine,rushesthroughtheintakemanifoldandintotheenginecylinder．Atthesametime,theexhaustvalveremainsclosedduringthisdownwardstrokeofthepiston.Thisvalveclosurepreventstheenteringair／fuelchargefromescapingthroughtheexhaustport.Afterthepistonreachesthebottomofitsfirststroke,thecylin

5、derispracticallyfullofanair／fuelcharge．Thedrawingofanair／fuelchargeintothecylinderinthismanner，duringthedownwardmovementofthepiston，constitutestheintakestrokeofthepiston．CompressionStrokeAfterthepistonreachesbottomdeadcenter(BDC)，itmovesupwardagainasthestartercontinuestoturnthecrankshaftinacl

6、ockwisedirection．Asthepistonisbeginningtomoveupward，theintakevalvecloses，andtheexhaustvalveremainsclosed．Sincebothvalvesareclosed，thepistoncompressestheair／fuelmixtureinthesmallspacebetweenthetopofthepistonandthecylinderhead．AsthepistonreachesTDCagainduringitsupwardtravel，thecompressionstroke

7、ofthepistonisover．Theair／fuelchargeisnowundercompressionsothatitwillproduceagreatdealofpowerwhenthesparkplugignitesit．PowerStrokeJustasorslightlybeforethepistonreachesTDConthecompressionstrokewiththeair／fuelmixturefullycompressed，atimedelectr