內(nèi)燃機(jī)專業(yè)英語英文

1、1內(nèi)燃機(jī)專業(yè)英語自編講義部分：1.EngineClassificationOverallMechanicsTheautomobileenginescanbeclassifiedaccdingto:1.numberofcylinders2.arrangementofcylinders3.arrangementofvalves4.typeofcooling5.numberofcycles(twofour)6.typeoffuelburned

2、7.typeofignition.Theengineisthesourceofpowerthatmakesthewheelsgoaroundthecarmove.Theautomobileengineisaninternalcombustionenginebecausethefuel(gasoline)isburnedinsideit.Theburningofgasolineinsidetheengineproduceshighpres

3、sureintheenginecombustionchamber.Thishighpressurefcespistontomovethemovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotatetherotarymotioniscarriedthroughthepowertraintothecarwheelssothatth

4、eyrotatethemoves.Theenginerequiresafuelsystemtosupplyitwithamixtureofairfuel.Thefuelsystemdoesthisbypumpingliquidgasolinefromatankintothecarburetamixingdevicethatmixesthegasolinewithair.Themixtureisdeliveredtotheenginewh

5、ereitisburned.Theenginealsoneedsacoolingsystemthecombustionoftheairfuelmixtureintheenginecreatesaveryhightemperature(ashighas2000to2700℃).Thecoolingsystemtakesheatawayfromtheenginebycirculatingaliquidcoolant(watermixedwi

6、thantifreeze)betweentheenginearadiat.Thecoolantgetshotasitgoesthroughtheengine.Itcoolsoffasitgoesthroughtheradiat.Thusthecoolantcontinuallytakesheatawayfromtheenginewhereitcoulddodamagedeliversittotheradiat.Airpassingthr

7、oughtheradiattakesheatawayfromtheradiat.Theenginealsoincludesalubricatingsystem.Thepurposeofthelubricatingsystemistosupplyallmovingpartsinsidetheenginewithlubricatingoiltheoilkeepsmovingpartsfromwearingexcessively.Theeng

8、inerequiresafourthsystemtheignitionsystem.Theignitionsystemprovideshighvoltageelectricsparksthatignitesetfiretothegesofairfuelmixtureintheenginecombustionchambers.Thefifthisstartingsystemitspurposeistochangetheelectrical

9、currentintothemechanicalenergytopushthecrankshaftaround.Bymeansofthistheenginecanbestarted.Thesefivesystemsarediscussedbrieflyinfollowingsections.32.FourstageengineOperationTheactiontakingplaceintheenginecylindercanbediv

10、idedintofourstagesstrokes.“Stroke”referstopistonmovementasstrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC（topdeadcenter）.ThelowerlimitofpistonmovementiscalledBDC(b

11、ottomdeadcenter).AstrokeispistonmovementfromTDCtoBDCfromBDCtoTDC.Inotherwdsthepistoncompletesastrokeeachtimeitchangeitsdirectionofmotion.Wheretheentirecycleofeventsinthecylinderrequiresfourstrokes(twocrankshaftrevolution

12、s)theengineiscalledafourstrokecycleengineafourcycleengine.Thefourpistonstrokesareintakecompressionpowerexhaust.Intakestroke.Ontheintakestroketheintakevalvehasopenedthepistonismovingdownwardamixtureofairvapizedgasolineise

13、nteringthecylinderthroughthevalvept.Themixtureofairvapizedgasolineisdeliveredtothecylinderbythefuelsystempressionstroke.AfterthepistonreachesBDCthelowerlimitofitstravelitbeginstomoveupward.Asthishappenstheintakevalveclos

14、es.Theexhaustvalveisalsoclosedsothatthecylinderissealed.Asthepistonmovesupward(pushednowbytherevolvingcrankshaftconnectingrod)theairfuelmixtureiscompressed.BythetimethepistonreachesTDCthemixturehasbeencompressedtoaslittl

15、easonetenthofitsiginalvolumeevenless.Thiscompressionoftheairfuelmixtureincreasesthepressureinthecylinder.Whentheairfuelmixtureiscompressednotonlydoesthepressureinthecylindergoupbutthetemperatureofthemixturealsoincreases.

16、Powerstroke.AsthepistonreachesTDConthecompressionstrokeanelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahighvoltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignitessetsfiretotheairfuelmix

17、ture.Itnowbeginstoburnveryrapidlythecylinderpressureincreasestoasmuchas35MPaevenme.Thisterrificpushagainstthepistonfcesitdownwardapowerimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaft