内燃机专业英语英文.docx

内燃机专业英语英文.docx

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内燃机专业英语英文

内燃机专业英语自编讲义部分：

1.EngineClassificationandOverallMechanics

Theautomobileenginescanbeclassifiedaccordingto:

1.numberofcylinders;2.arrangementofcylinders;3.arrangementofvalves;4.typeofcooling;5.numberofcycles（twoorfour）;6.typeoffuelburned;7.typeofignition.

Theengineisthesourceofpowerthatmakesthewheelsgoaroundandthecarmove.Theautomobileengineisaninternal-combustionenginebecausethefuel（gasoline）isburnedinsideit.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcespistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate;therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthemoves.

Theenginerequiresafuelsystemtosupplyitwithamixtureofairandfuel.Thefuelsystemdoesthisbypumpingliquidgasolinefromatankintothecarburetor,amixingdevicethatmixesthegasolinewithair.Themixtureisdeliveredtotheenginewhereitisburned.

Theenginealsoneedsacoolingsystem,thecombustionoftheair-fuelmixtureintheenginecreatesaveryhightemperature（ashighas2000to2700℃）.Thecoolingsystemtakesheatawayfromtheenginebycirculatingaliquidcoolant（watermixedwithantifreeze）betweentheengineandaradiator.Thecoolantgetshotasitgoesthroughtheengine.Itcoolsoffasitgoesthroughtheradiator.Thus,thecoolantcontinuallytakesheatawayfromtheengine,whereitcoulddodamage,anddeliversittotheradiator.Airpassingthroughtheradiatortakesheatawayfromtheradiator.

Theenginealsoincludesalubricatingsystem.Thepurposeofthelubricatingsystemistosupplyallmovingpartsinsidetheenginewithlubricatingoil;theoilkeepsmovingpartsfromwearingexcessively.

Theenginerequiresafourthsystem,theignitionsystem.Theignitionsystemprovideshigh-voltageelectricsparksthatignite,orsetfireto,thechargesofair-fuelmixtureintheenginecombustionchambers.

Thefifthisstartingsystemanditspurposeistochangetheelectricalcurrentintothemechanicalenergytopushthecrank-shaftaround.Bymeansofthis,theenginecanbestarted.

Thesefivesystemsarediscussedbrieflyinfollowingsections.

WordsandExpressions

combustionchamber燃烧室；ignition.点燃；powertrain动力传动系统；carburetor化油器；antifreeze防冻的；coolant冷却剂（液态）；crankshaft曲轴

2.Four-stage-engineOperation

Theactiontakingplaceintheenginecylindercanbedividedintofourstages,orstrokes.“Stroke”referstopistonmovement;asstrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC（topdeadcenter）.ThelowerlimitofpistonmovementiscalledBDC（bottomdeadcenter）.AstrokeispistonmovementfromTDCtoBDCorfromBDCtoTDC.Inotherwords,thepistoncompletesastrokeeachtimeitchangeitsdirectionofmotion.

Wheretheentirecycleofeventsinthecylinderrequiresfourstrokes（ortwocrankshaftrevolutions）,theengineiscalledafour-stroke-cycleengine,orafour-cycleengine.Thefourpistonstrokesareintake,compression,power,andexhaust.

Intakestroke.Ontheintakestroke,theintakevalvehasopened,thepistonismovingdownward,andamixtureofairandvaporizedgasolineisenteringthecylinderthroughthevalveport.Themixtureofairandvaporizedgasolineisdeliveredtothecylinderbythefuelsystemandcarburetor.

Compressionstroke.AfterthepistonreachesBDC,orthelowerlimitofitstravel,itbeginstomoveupward.Asthishappens,theintakevalvecloses.Theexhaustvalveisalsoclosed,sothatthecylinderissealed.Asthepistonmovesupward（pushednowbytherevolvingcrankshaftandconnectingrod）,theair-fuelmixtureiscompressed.BythetimethepistonreachesTDC,themixturehasbeencompressedtoaslittleasone-tenthofitsoriginalvolume,orevenless.Thiscompressionoftheair-fuelmixtureincreasesthepressureinthecylinder.Whentheair-fuelmixtureiscompressed,notonlydoesthepressureinthecylindergoup,butthetemperatureofthemixturealsoincreases.

Powerstroke.AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair-fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.

Exhauststroke.AsthepistonreachesBDCagain,theexhaustvalve