畢業(yè)設(shè)計論文 外文文獻翻譯 汽車專業(yè) 發(fā)動機概述 中英文對照

GENERALCOMMENTSOFAUTOMOBILEENGINEENGINEISTHESOURCEOFAUTOMOTIVESOFAR,AUTOMOTIVEENGINESAREALLPOWEREDBYHEATEXCEPTFORAFEWOFAUTOMOTIVESDRIVEDBYELECTRICITYMODERNAUTOMOTIVEENGINESARECALLEDINTERNALCOMBUSTIONENGINESBECAUSEFUELBURNSINSIDETHEENGINETHEENGINECONVERTSTHEBURNINGFUELSTHERMALENERGYTOMECHANICALENERGYBYCOOLINGSYSTEMSLIQUIDCOOLEDENGINESANDAIRCOOLEDENGINESAREBEINGUSEDLIQUIDCOOLEDENGINESARETHEMOSTCOMMONINTHEDIESELINDUSTRYBYFUELSYSTEMGASOLINEDIESELANDPROPANEFUELSYSTEMSARECURRENTLYUSEDINAWIDEVARIETYOFENGINESBYIGNITIONMETHODGASENGINESUSETHESPARKELECTRICALIGNITIONDIESELENGINESUSETHEHEATFROBDCTOTDCITVARIESWITHCYLINDERBORESIZE,LENGTHOFPISTONSTROKE,ANDNUMBSYSTEMINJECTIONTHECALORYOFDIESELENGINECOMEFROMTHEFUELEMBLAZEDBYTHECOMPRESSEDAIRTHEDIESELENGINECOMPRESSIONRATIONISMUCHBIGGERTHANTHEGASENGINEITSSUFFICIENTCALORYISFROMTHEFUELBURNEDBYTHEPRESSEDAIRBYVALVEARRANGEMENTFOURTYPESOFVALVEARRANGEMENTSHAVEBEENUSEDINGASOLINEANDDIESELENGINESOFTHEFOURTYPESL,T,F,ANDIHEADS,THEIHEADISCOMMONLYUSEDONDIESELENGINESBYCYLINDERARRANGEMENTENGINEBLOCKCONFIGURATIONORCYLINDERARRANGEMENTDEPENDSONCYLINDERBLOCKDESIGNCYLINDERSMAYBEARRANGEDINASTRAIGHTLINEONEBEHINDTHEOTHERTHEMOSTCOMMONINLINEDESIGNSARETHEFOURANDSIXCYLINDERENGINESTHEVTYPEOFCYLINDERARRANGEMENTUSESTWOBANKSOFCYLINDERSARRANGEDINA60TO90VDESIGNTHEMOSTCOMMONEXAMPLESARETHOSEWITHTWOBANKSOFTHREETOEIGHTCYLINDERSEACHTHEOPPOSEDENGINEUSESTWOBANKSOFCYLINDERSOPPOSITEEACHOTHERWITHTHECRANKSHAFTINBETWEENENGINECLASSIFICATIONACCORDINGTOTHEDIFFERENCESOFTHEPISTONMOVEMENT,THEPISTONINTENALCOMBUSITIONENGINEWILLBECLASSIFIEDRECIPROCATINGINTENALCOMBUSITIONENGINEANDROTARYPISTONINTENALCOMBUSITIONENGINETHENWEWILLINTRODUCEWORKINGPRINCIPLEDIAGRAMOFRECIPROCATINGINTERNALCOMBUSTIONENGINEEXCEPTFORTHEWANKELROTARY,ENGINE,ALLPRODUCTIONAUTOMOTIVEENGINESARETHERECIPROCATING,ORPISTON,DESIGNRECIPROCATINGMEANS“UPANDDOWN“OR“BACKANDFORTH“ITISTHISUPANDDOWNACTIONOFAPISTONINACYLINDERTHATGIVESTHERECIPROCATINGENGINEITSNAMEALMOSTALLENGINESOFTHISTYPEAREBUILTUPONACYLINDERBLOCK,ORENGINEBLOCKTHEBLOCKISANIRONORALUMINUMCASTINGTHATCONTAINSTHEENGINECYLINDERSTHETOPOFTHEBLOCKISCOVEREDWITHTHECYLINDERHEAD,WHICHFORMSTHECOMBUSTIONCHAMBERSTHEBOTTOMOFTHEBLOCKISCOVEREDWITHANOILPAN,OROILSUMPAMAJOREXCEPTIONTOTHISTYPEOFENGINEONSTRUCTIONISTHEAIRCOOLEDVOLKWAGENENGINEITISREPRESENTATIVEOFTHEHORIZONTALLYOPPOSEDAIRCOOLEDENGINESUSEDBYPORSCHE,CHEVROLETCORVAIR,ANDSOMEOTHERAUTOMOBILEMANUFACTURERSINYEARSPASTPOWERISPRODUCEDBYTHEINLINEMOTIONOFAPISTONINACYLINDERHOWEVER,THISLINEARMOTIONMUSTBECHANGEDTOROTATINGMOTIONTOTURNTHEWHEELSOFACARORTRUCKTHEPISTONISATTACHEDTOTHETOPOFACONNECTINGRODBYAPIN,CALLEDAPISTONPINORWRISTPINTHECONNECTINGRODTRANSMITSTHEUPANDDOWNMOTIONOFTHEPISTONTOTHECRANKSHAFT,WHICHCHANGESITTOROTATINGMOTIONTHECONNECTINGRODISMOUNTEDONTHECRANKSHAFTWITHLARGEBEARINGSCALLEDRODBEARINGSSIMILARBEARINGS,CALLEDMAINBEARINGS,AREUSEDTOMOUNTTHECRANKSHAFTINTHEBLOCKTHECRANKSHAFTCHANGESTHERECIPROCATINGMOTIONOFTHEPISTONSTOROTATINGMOTIONTHECOMBUSTIBLEMIXTUREOFGASOLINEANDAIRENTERSTHECYLINDERSTHROUGHVALVESAUTOMOTIVEENGINESUSEPOPPETVALVESTHEVALVESCANBEINTHECYLINDERHEADORINTHEBLOCKTHEOPENINGANDCLOSINGOFTHEVALVESISCONTROLLEDBYACAMSHAFTLOBESONTHECAMSHAFTPUSHTHEVALVESOPENASTHECAMSHAFTROTATESASPRINGCLOSESEACHVALVEWHENTHELOBEISNOTHOLDINGITOPENTHEMOSTCOMMONARRANGEMENTSOFENGINECYLINDERSANDVALVESAREDISCUSSEDLATERTHEBASICSINGLECYLINDERENGINECONSISTSOFACYLINDERENGINEBLOCK,AMOVABLEPISTONINSIDETHISCYLINDER,ACONNECTINGRODATTACHEDATTHETOPENDTOTHEPISTONANDATTHEBOTTOMTOTHEOFFSETPORTIONOFACRANKSHAFT,ACAMSHAFTTOOPERATETHETWOVALVESINTAKEANDEXHAUST,ANDACYLINDERHEADAFLYWHEELISATTACHEDTOONEENDOFTHECRANKSHAFTTHEOTHERENDOFTHECRANKSHAFTHASAGEARTODRIVETHECAMSHAFTGEARTHECAMSHAFTGEARISTWICEASLARGEASTHECRANKSHAFTGEARTHISDRIVESTHECAMSHAFTATHALFTHESPEEDOFTHECRANKSHAFTONFOURSTROKECYCLEENGINES,THECRANKSHAFTANDCAMSHAFTRUNATTHESAMESPEEDENERGYCONVERSIONTHEINTERNALCOMBUSTIONDIESELENGINEISADEVICEUSEDTOCONVERTTHECHEMICALENERGYOFTHEFUELINTOHEATENERGYANDTHENCONVERTTHISHEATENERGYINTOUSABLEMECHANICALENERGYTHISISACHIEVEDBYCOMBININGTHEAPPROPRIATEAMOUNTSOFAIRANDFUELANDBURNINGTHEMINANENCLOSEDCYLINDERATACONTROLLEDRATEAMOVABLEPISTONINTHECYLINDERISFORCEDDOWNBYTHEEXPANDINGGASESOFCOMBUSTIONTHEMOVABLEPISTONINCYLINDERISCONNECTEDTOTHETOPOFACONNECTINGRODTHEBOTTOMOFTHECONNECTEDRODISATTACHEDTOTHEOFFSETPORTIONISTRANSFERREDTOTHECRANKSHAFT,ASTHEPISTONISFORCEDDOWN,THISOFFSETPORTIONOFACRANKSHAFT,TOROTATETHERECIPROCATINGBACKANDFORTHORUPANDDOWNMOVEMENTOFTHEPISTONISCONVERTEDTOROTARYTURNINGMOTIONOFTHECRANKSHAFT,WHICHSUPPLIESTHEPOWERTODRIVETHEVEHICLEINGENERALANAVERAGEAIRFUELRATIOFORGOODCOMBUSTIONISABOUT15PARTSOFAIRTO1PARTOFFUELBYWEIGHTHOWEVER,THEDIESELENGINEALWAYSTAKESINAFULLCHARGEOFAIRSINCETHEREISNOTHROTTLEPLATEINMOSTSYSTEMS,BUTONLYASMALLPARTOFTHISAIRISUSEDATLOWORIDLEENGINESPEEDSAIRCONSISTSOFABOUT20PERCENTOXYGENWHILETHEREMAINING80PERCENTISMOSTLYNITROGENTHISMEANSTHAT,FOREVERYGALLONOFFUELBURNED,THEOXYGENIN9,000TO10,000GALLONSOFAIRISREQUIREDFOURSTROKECYCLEGASOLINEBYITSELFWILLNOTBURN,ITMUSTBEMIXEDWITHOXYGENAIRTHISBURNINGISCALLEDCOMBUSTIONANDISAWAYOFRELEASINGTHEENERGYSTOREDINTHEAIRFUELMIXTURETODOANYUSEFULWORKINANENGINE,THEAIRFUELMIXTUREMUSTBECOMPRESSEDANDBURNEDINASEALEDCHAMBERHERETHECOMBUSTIONENERGYCANWORKONTHEMOVABLEPISTONTOPRODUCEMECHANICALENERGYTHECOMBUSTIONCHAMBERMUSTBESEALEDASTIGHTLYASPOSSIBLEFOREFFICIENTENGINEOPERATIONANYLEAKAGEFROMTHECOMBUSTIONCHAMBERALLOWSPARTOFTHECOMBUSTIONENERGYTODISSIPATEWITHOUTADDINGTOTHEMECHANICALENERGYDEVELOPEDBYTHEPISTONMOVEMENTTHE4STROKEENGINEISALSOCALLEDTHEOTTOCYCLEENGINE,INHONOROFTHEGERMANENGINEER,DRNIKOLAUSOTTO,WHOFIRSTAPPLIEDTHEPRINCIPLEIN1876INTHE4STROKEENGINE,FOURSTROKESOFTHEPISTONINTHECYLINDERAREREQUIREDTOCOMPLETEONEFULLOPERATINGCYCLETWOSTROKESUPANDTWOSTROKESDOWNEACHSTROKEISNAMEDAFTERTHEACTIONITPERFORMSINTAKE,COMPRESSION,POWER,ANDEXHAUST1、INTAKESTROKEASTHEPISTONMOVESDOWN,THEVAPORIZED,MIXTUREOFFUELANDAIRENTERSTHECYLINDERPASTTHEOPENINTAKEVALVE2、COMPRESSIONSTROKETHEPISTONRETURNSUP,THEINTAKEVALVECLOSES,THEMIXTUREISCOMPRESSEDWITHINTHECOMBUSTIONCHAMBER,ANDIGNITEDBYASPARK3、POWERSTROKETHEEXPANDINGGASESOFCOMBUSTIONFORCETHEPISTONDOWNINTHECYLINDERTHEEXHAUSTVALVEOPENSNEARTHEBOTTOMOFTHESTROKE4、EXHAUSTSTROKETHEPISTONMOVESBACKUPWITHTHEEXHAUSTVALVEOPEN,ANDTHEBURNEDGASESAREPUSHEDOUTTOPREPAREFORTHENEXTINTAKESTROKETHEINTAKEVALVEUSUALLYOPENSJUSTBEFORETHETOPOFTHEEXHAUSTSTROKETHIS4STROKECYCLEISCONTINUOUSLYREPEATEDINEVERYCYLINDERASLONGASTHEENGINEREMAINSRUNNINGTWOSTROKECYCLETHETWOSTROKECYCLEDIESELENGINECOMPLETESALLFOUREVENTSINTAKE,COMPRESSION,POWER,ANDEXHAUSTINONEREVOLUTIONOFTHECRANKSHAFTORTWOSTROKESOFTHEPISTONASERIESOFPORTSOROPENINGSISARRANGEDAROUNDTHECYLINDERINSUCHAPOSITIONTHATTHEPORTSAREOPENWHENTHEPISTONISATTHEBOTTOMOFITSSTROKEABLOWERFORCESAIRINTOTHECYLINDERTHROUGHTHEOPENPORTSEXPELLINGALLREMAININGEXHAUSTGASESPASTTHEOPENEXHAUSTVALVESANDFILLINGTHECYLINDERWITHAIRTHISISCALLEDSCAVENGINGASTHEPISTONMOVESUP,THEEXHAUSTVALVESCLOSEANDTHEPISTONCOVERSTHEPORTSTHEAIRTRAPPEDABOVETHEPISTONISCOMPRESSEDTONCOVERSTHEPORTSTHEAIRTRAPPEDABOVETHEPISTONISCOMPRESSEDSINCETHEEXHAUSTVALVEISCLOSEDJUSTBEFORETHEPISTONREACHESTOPDEADCENTER,THEREQUIREDAMOUNTOFFUELISINJECTEDINTOTHECYLINDERTHEHEATGENERATEDBYCOMPRESSINGTHEAIRIGNITESTHEFUELALMOSTIMMEDIATELYCOMBUSTIONCONTINUESUNTILTHEFUELINJECTEDHASBEENBURNEDTHEPRESSURERESULTINGFROMCOMBUSTIONFORCESTHEPISTONDOWNWARDONTHEPOWERSTROKEWHENTHEPISTONISAPPROXIMATELYFALFWAYDOWN,THEEXHAUSTVALVESAREOPENED,ALLOWINGTHEEXHAUSTGASESTOESCAPEFURTHERDOWNWARDMOVEMENTUNCOVERSTHEINLETPORTS,CAUSINGFRESHAIRTOENTERTHECYLINDERANDEXPELTHEEXHAUSTGASESTHEENTIREPROCEDUREISTHENREPEATED,ASTHEENGINECONTINUESTORUNTHEDIFFERENCESOFTHETWOINTENALCOMBUSTIONENGINEITCOULDBEASSUMEDTHATATWOCYCLEENGINEWITHTHESAMENUMBEROFCYLINDERS,THESAMEDISPLACEMENT,COMPRESSIONRATIO,ANDSPEEDASAFOURCYCLEENGINEWOULDHAVETWICETHEPOWERSINCEITHASTWICEASMANYPOWERHOWEVER,THISISNOTTHECASE,SINCEBOTHTHEPOWERANDCOMPRESSIONSTROKESARESHORTENEDTOALLOWSCAVENGINGTOTAKEPLACETHETWOCYCLEENGINEALSOREQUIRESABLOWER,WHICHTAKESENGINEPOWERTODRIVEABOUT160DEGREESOUTOFEACH360DEGREESOFCRANKSHAFTROTATIONAREREQUIREDFOREXHAUSTGASEXPULSIONANDFRESHAIRINTAKESCAVENGINGINATWOCYCLEENGINEABOUT415DEGREESOFEACH720DEGREESOFCRANKSHAFTROTATIONINAFOURCYCLEENGINEAREREQUIREDFORINTAKEANDEXHAUSTTHESEFIGURESINDICATETHATABOUT445OFCRANKROTATIONISUSEDFORTHEPOWERPRODUCINGEVENTSINTHETWOCYCLEENGINE,WHILEABOUT59OFCRANKROTATIONISUSEDFORTHESEPURPOSESINTHEFOURCYCLEENGINEFRICTIONLOSSESARECONSEQUENTLYGREATERINTHEFOURCYCLEENGINEHEATLOSSES,HOWEVER,AREGREATERINTHETWOCYCLEENGINETHOUGHBOTHTHEEXHAUSTANDTHECOOLINGSYSTEMSINSPITEOFTHESEDIFFERENCES,BOTHENGINETYPESENJOYPROMINENTUSEWORLDWIDEENGINECONSTRUCTIONCYLINDERBLOCKTHECYLINDERBLOCKISCASTINONEPIECEUSUALLY,THISISTHELARGESTANDTHEMOSTCOMPLICATEDSINGLEPIECEOFMETALINTHEAUTOMOBILETHECYLINDERBLOCKISACOMPLICATEDCASTINGMADEOFGRAYIRONCASTIRONORALUMINUMITCONTAINSTHECYLINDERSANDTHEWATERJACKETSTHATSURROUNDTHEMTOMAKETHECYLINDERBLOCK,ASANDFORMCALLEDAMOLDISMADETHENMOLTENMETALISPOUREDINTOTHEMOLDWHENTHEMETALHASCOOLEDTHESANDMOLDISBROKENUPANDREMOVEDTHISLEAVESTHETOUGHCYLINDERBLOCKCASTINGTHECASTINGTHECASTINGISTHENCLEANEDANDMACHINEDTOMAKETHEFINISHEDBLOCKCYLINDERBLOCKSFORDIESELENGINESAREVERYSIMILARTOTHOSEFORSPARKIGNITIONENGINESTHEBASICDIFFERENCEISTHATTHEDIESELENGINECYLINDERBLOCKISHEAVIERANDSTRONGERTHISISBECAUSEOFTHEHIGHERPRESSURESDEVELOPEDINTHEDIESELENGINECYLINDERSSEVERALENGINESHAVEALUMINUMCYLINDERBLOCKSALUMINUMISRELATIVELYLIGHTMETAL,WEIGHINGMUCHLESSTHANCASTIRONALSO,ALUMINUMCONDUCTSHEATMORERAPIDLYTHANCASTSOFTTOUSEASCYLINDERWALLMATERIALITWEARSTOORAPIDLYTHEREFORE,ALUMINUMCYLINDERBLOCKSMUSTHAVECASTIRONCYLINDERLINERSORBECASTFROMANALUMINUMALLOYTHATHASSILICONPARTICLESINITSOMEMANUFACTURESMAKEANALUMINUMCYLINDERBLOCKTHATDOESNOTHAVECYLINDERLINERS,ORSLEEVESINSTEAD,THEALUMINUMISLOADEDWITHSILICONPARTICLESSILICONISAVERYHARDMATERIALAFTERTHECYLINDERBLOCKISCAST,THECYLINDERSAREHONEDTHENTHEYARETREATEDWITHACHEMICALTHATETCHESEATSAWAY,THESURFACEALUMINUMTHISLEAVESONLYTHESILICONPARTICLESEXPOSEDTHEPISTONANDRINGSSLIDEONTHESILICONWITHMINIMUMWEARPISTONTHEPISTONCONVERTSTHEPOTENTIALENERGYOFTHEFUELINTOTHEKINETICENERGYTHATTURNSTHECRANKSHAFTTHEPISTONISACYLINDRICALSHAPEDHOLLOWPARTTHATMOVESUPANDDOWNINSIDETHEENGINESCYLINDERITHASGROOVESAROUNDITSPERIMETERNEARTHETOPWHERETHERINGAREPLACEDTHEPISTONFITSSNUGLYINTHECYLINDERITHASGROOVESAROUNDITSPERIMETERNEARTHETOPWHERETHERINGSAREPLACEDTHEPISTONFITSSNUGLYINTHECYLINDERTHEPISTONSATEUSEDTOENSUREASNUG“AIRTIGHT”FITTHEPISTONINYOURENGINESCYLINDERARESIMILARTOYOURLEGSWHENYOURIDEABICYCLETHINKOFYOURLEGSASPISTONSTHEYGOUPANDDOWNONTHEPEDALS,PROVIDINGPOWERPEDALSARELIKETHECONNECTINGRODSTHEYARE“ATTACHED”TOYOURLEGSTHEPEDALSAREATTACHEDTOTHEBICYCLECRANKWHICHISLIKETHECRANKSHAFT,BECAUSEITTURNSTHEWHEELSTOREVERSETHIS,THEPISTONSLEGSAREATTACHEDTOTHECONNECTINGRODSPEDALSWHICHAREATTACHEDTOTHECRANKSHAFTTHEBICYCLERANKTHEPOWERFROMTHECOMBUSTIONINTHECYLINDERSPOWERSTHEFROMTHECOMBUSTIONRODSTOTURNTHECRANKSHAFTCONNECTINGRODTHECONNECTINGRODSHOWNINISMADEOFFORGEDHIGHSTRENGTHSTEELITTRANSMITSFORCEANDMOTIONFROMTHEPISTONTOTHECRANKPINONTHECRANKSHAFTASTEELPISTONPIN,OR“WRISTPIN”,CONNECTSTHESMALLENDOFTHECONNECTINGRODSOMERODSHAVEALOCKBOLTINTHESMALLENDASTHEPISTONMOVESUPANDDOWNINTHECYLINDER,THEPINROCKSBACKANDFORTHINTHEHOLE,ORBORE,INTHEPISTONTHEBIGENDOFTHECONNECTINGRODISATTACHEDTOACRANKPINBYARODBEARINGCAPCONNECTINGRODANDRODBEARINGCAPSAREASSEMBLEDDURINGMANUFACTURETHENTHEHOLDFORTHEBEARINGISBOREDWITHTHECAPINPLACETHISISCALLEDLINEBRINGITMAKEEACHRODANDITSCAPAMATCHEDSETUSUALLY,THESAMENUMBERISSTAMPEDONTHERODANDCAPTHISPREVENTSTHECAPSSETTINGMIXEDDURINGENGINESERVICEIFTHECAPSAREMIXED,THEBEARINGBOREWILLNOTBEROUNDANENGINEASSEMBLEDWITHTHERODBEARINGCAPSSWITCHEDWILLPROBABLYLOCKTHECRANKSHAFTIFTHECRANKSHAFTTURNS,THEBEARINGWILLPROBABLYHAVEIMPROPERCLEARANCEANDEARLYBEARINGFAILUREWILLRESULTANOTHERREASONFORKEEPINGTHECAPANDRODMATCHEDISTOPREVENTENGINEUNBALANCEANDUNWANTEDVIBRATIONALLCONNECTINGRODSINANENGINEMUSTBEASLIGHTASPOSSIBLEBUTTHEYMUSTALLWEIGHTHESAMEIFONERODISHEAVIERTHANTHEOTHER,THEENGINEWILLVIBRATETHISCOULDDAMAGETHEENGINECRANKSHAFTTHECRANKSHAFTTHENMAINROTATINGMEMBER,ORSHAFT,INTHEENGINEITHASCRANKPINS,TOWHICHTHECONNECTINGRODFROMTHEPISTONSAREATTACHEDDURINGTHEPOWERSTROKES,THECONNECTINGRODSFORCETHECRANKPINSANDTHEREFORETHECRANKSHAFTTOROTATETHERECIPROCATINGMOTIONOFTHEPISTONSISCHANGEDTOROTARYMOTIONASTHECRANKSHAFTSPINSTHISROTARYMOTIONISTRANSMITTEDTHROUGHTHEPOWERTRAINTOTHECARWHEELSTHECRANKSHAFTISASTRONG,ONEPIECECASTING,ORFORGING,ORHEATTREATEDALLOYSTEELITMUSTBESTRONGTOTAKETHEDOWNWARDFORCEOFPOWERSTROKESWITHOUTEXCESSIVEBENDINGITMUSTBEBALANCEDSOTHEENGINEWILLRUNWITHOUTEXCESSIVEVIBRATIONENGINEDISPLACEMENTTHEFREQUENTLYUSEDENGINESPECIFICATIONSAREENGINEDISPLACEMENTANDCOMPRESSIONRATIODISPLACEMENTANDCOMPRESSIONRATIONARERELATEDTOEACHOTHER,ASWEWILLLEARNINTHEFOLLOWINGPARAGRAPHSBYDISPLACEMENTENGINEDISPLACEMENTISTHEAMOUNTOFAIRDISPLACEDBYTHEPISTONWHENITMOVESFROTHEELECTRICALIGNITIONSYSTEMCAUSESASPARKACROSSTHESPARKPLUGELECTRODESINTHECYLINDERATTHEENDOFTHECOMPRESSIONSTROKE,WHICHIGNITESTHEVAPORIZEDFUELANDAIRMIXTUREMCOMPRESSINGTHEAIRTOIGNITETHEFUELWHENITISINJECTEDINTOTHECYLINDERATTHEENDOFTHECOMPRESSIONRATIOSAREMUCHHIGHERTHANGASOLINEENGINECOMPRESSIONRATIOS,SUFFICIENTHEATISGENERATEDBYCOMPRESSINGTHEAIRTOIGNITETHEFUEROFCYLINDERSENGINESARECLASSIFIEDASLOW,MEDIUM,HIGH,ANDSUPERHIGHSPEEDCOMMONLYUSEDTOINDICATEENGINESIZE,THISSPECIFICATIONISREALLYAMEASUREMENTOFCYLINDERVOLUMETHENUMBEROFCYLINDERSISAFACTORINDETERMININGDISPLACEMENT,BUTTHEARRANGEMENTOFTHECYLINDERSORVALVESISNOTENGINEDISPLACEMENTISCALCULATEDBYMULTIPLYINGTHENUMBEROFCYLINDERSINTHEENGINEBYTHETOTALENGINEDISPLACEMENTISTHEVOLUMEDISPLACEDBYALLTHEPISTONSTHEDISPLACEMENTOFONECYLINDERISTHESPACETHROUGHWHICHTHEPISTONSTOPSURFACEMOVESASITTRAVELSFROMTHEBOTTOMOFITSSTROKEBOTTOMDEADCENTERTOTHETOPOFITSSTROKETOPDEADCENTERITISTHEVOLUMEDISPLACEDBYTHECYLINDERBYONEPISTONSTROKEPISTONDISPLACEMENTCANBECALCULATEDASFOLLOWS1DIVIDETHEBORECYLINDERDIAMETERBYTWOTHISGIVESYOUTHERADIUSOFTHEBORE2SQUARETHERADIUSMULTIPLYITBYITSELF3MULTIPLYTHESQUAREOFTHERADIUSBY31416PIORTOFINDTHEAREAOFTHECYLINDERCROSSSECTION4MULTIPLYTHEAREAOFTHECYLINDERCROSSSECTIONBYTHELENGTHOFTHESTROKEYOUNOWKNOWTHEPISTONDISPLACEMENTFORONECYLINDERMULTIPLYTHISBYTHENUMBEROFCYLINDERSTODETERMINETHETOTALENGINEDISPLACEMENTTHEFORMULAFORTHECOMPLETEPROCEDUREREADSSTROKENOOFCYLINDERSDISPLACEMENTR2COMPRESSIONRATIOTHISSPECIFICATIONCOMPARESTHETOTALCYLINDERVOLUMETOTHEVOLUMEOFONLYTHECOMBUSTIONCHAMBERTOTALCYLINDERVOLUMEMAYSEEMTOBETHESAMEASPISTONDISPLACEMENT,BUTITISNOTTOTALCYLINDERVOLUMETHECOMBUSTIONCHAMBERVOLUMEWITHTHEPISTONATTOPDEADCENTERISOFTENCALLEDTHECLEARANCEVOLUMECOMPRESSIONRATIOISTHETOTALVOLUMEOFACYLINDERDIVIDEDBYITSCLEARANCEVOLUMEIFTHECLEARANCEVOLUMEISONEEIGHTHOFTHETOTALCYLINDERVOLUME,THECOMPRESSIONRATIOIS88TO1THEFORMULAISASFOLLOWSCOMPRESSIONRATIOOLUMECLEARNCVTTINTHEORY,THEHIGHERTHECOMPRESSIONRATIO,THEGREATERTHEEFFICIENCYOFTHEENGINE,ANDTHEMOREPOWERANENGINEWILLDEVELOPFROMAGIVENQUANTITYOFFUELTHEREASONFORTHISISTHATCOMBUSTIONTAKESPLACEFASTERBECAUSETHEFUELMOLECULESAREMORETIGHTLYPACKEDANDTHEFLAMEOFCOMBUSTIONTRAVELSMORERAPIDLYBUTTHEREAREPRACTICALLIMITSTOHOWHIGHACOMPRESSIONRATIOCANBEBECAUSEOFTHEUNAVAILABILITYOFHIGHOCTANEFUEL,MOSTGASOLINEBURNINGENGINESARERESTRICTEDTOACOMPRESSIONRATIONOGREATERTHAN115TO1RATIOSTHISHIGH,HOWEVER,CREATEHIGHCOMBUSTIONCHAMBERTEMPERATURESTHISINTURNCREATESOXIDESOFNITROGENNOX,APRIMARYAIRPOLLUTANTINTHEEARLY1970S,COMPRESSIONRATIOSWERELOWEREDTOAROUND8TOPERMITTHEUSEOFLOWEROCTANELOWLEADORUNLEADEDFUEL,ANDTOREDUCENOXFORMATIONADVANCESINELECTRONICENGINECONTROLINTHE1980SHAVEALLOWEDENGINEERSTORAISECOMPRESSIONRATIOSTOTHE9AND10TO1RANGEFOROPTIMUMPERFORMANCEANDECONOMY發(fā)動機概述發(fā)動機是汽車的動力源。迄今為止除為數(shù)不多的電動汽車外，汽車發(fā)動機都是熱能動力裝置?，F(xiàn)代汽車發(fā)動機因為燃料發(fā)動機內(nèi)部燃燒而被稱為內(nèi)燃機。發(fā)動機將燃料燃燒產(chǎn)生的熱能變?yōu)闄C械能。冷卻系統(tǒng)水冷發(fā)動機和風(fēng)冷發(fā)動機被應(yīng)用，在柴油引擎制造業(yè)中，水冷發(fā)動機應(yīng)用最廣泛。燃料系統(tǒng)汽油，柴油，丙烷燃料系統(tǒng)在各式各樣的發(fā)動機中廣泛應(yīng)用。點火方式汽油機采用電子點火系統(tǒng)；電子點火系統(tǒng)在壓縮行程終了時通過氣缸內(nèi)的火花塞高壓電板產(chǎn)生火花，點燃霧化的燃油空氣混合物。柴油機的能量來源于當(dāng)燃料被注入氣缸時壓縮空氣點燃燃料。柴油機的壓縮比遠遠大于汽油機的壓縮比。在注入燃料時靠壓縮空氣點燃燃料能產(chǎn)生足夠的熱量。閥門裝置已經(jīng)有四種閥門配備被應(yīng)用于汽油機和柴油機上。在這四種類型中（I、T、F和I頭型），I型在柴油機中最常用。氣缸排列方式發(fā)動機的外形結(jié)構(gòu)或氣缸排列方式取決于氣缸的設(shè)計，氣缸一個接一個地被排成直線，直線式最常用于四缸或六缸發(fā)動機；V型的氣缸排列方式是兩排氣缸成60到90角度。最常用的機型每排氣缸有三到八個。對置式發(fā)動機是指兩列氣缸水平相對曲軸位于二者之間發(fā)動機的分類按活塞運動方式的不同，活塞式內(nèi)燃機可分為往復(fù)活塞式和旋轉(zhuǎn)活塞式兩種，前者在現(xiàn)代車上被廣泛的運用，下面就以往復(fù)活塞式內(nèi)燃機為例，介紹一下發(fā)動機的工作原理。除了旋轉(zhuǎn)活塞式發(fā)動，所有生產(chǎn)的汽車發(fā)動機都是往復(fù)式的。往復(fù)的意思就是“上下運動”或者“前后運動”。正是由于活塞在氣缸內(nèi)做上下運動而被稱為往復(fù)式發(fā)動機。幾乎所有的這種類型的發(fā)動機都是坐在氣缸上或發(fā)動機機體上的，機體是鑄有發(fā)動機氣缸的鐵或鋁的鑄造物。機體的上端被氣缸蓋住，形成燃燒室。機體的低部被油底殼或油箱覆蓋。對于這種類型的發(fā)動機在構(gòu)造上有一個例外風(fēng)冷的發(fā)動機，它是典型的水平對置式風(fēng)冷發(fā)動機過去的幾年里被其他一些汽車廠商廣泛應(yīng)用?；钊跉飧變?nèi)的直線運動產(chǎn)生動力。然而，這種直線運動必須轉(zhuǎn)變成驅(qū)動轎車或卡車車輪轉(zhuǎn)動的旋轉(zhuǎn)運動?；钊灰粋€銷稱為活塞銷連接在連桿的頂端。連桿將活塞的上下運動傳遞給曲軸，曲軸將直線運動轉(zhuǎn)變?yōu)樾D(zhuǎn)運動。連桿由大軸承安裝在曲軸上。用類似的軸承稱為主軸承，將曲軸安裝在機體上。曲軸將活塞的往復(fù)運動轉(zhuǎn)變?yōu)樾D(zhuǎn)運動。可燃的汽油和空氣混合物通閥門進入氣缸。汽車發(fā)動機使用POPPET閥門。這種閥門可以安裝在機體或氣缸頭部。閥門的開啟與關(guān)閉被凸輪軸控制。當(dāng)凸輪軸旋轉(zhuǎn)時凸輪上的凸起使閥門打開。當(dāng)凸起不在維持閥門開啟時，彈簧使閥門關(guān)閉。下面討論氣缸和閥門最常見的安排方式?；镜膯螝飧装l(fā)動機包括一個氣缸（發(fā)動機機體），氣缸內(nèi)可移動的活塞，連桿頭端連接活塞，底端連接曲軸上的分支部分，操縱兩個閥門（進氣門，排氣門）的凸輪軸以及汽缸蓋。飛輪安裝在曲軸的一端。曲軸的一端有一個齒輪來驅(qū)動凸輪軸上的齒輪。凸輪軸上的凸輪是曲軸上齒輪的兩倍。當(dāng)凸輪軸與曲軸以相同的轉(zhuǎn)速轉(zhuǎn)動時，在四沖程發(fā)動機中凸輪軸上吃捆的轉(zhuǎn)速是曲軸上齒輪轉(zhuǎn)速的一半。能量轉(zhuǎn)化方面內(nèi)燃機柴油機是將化學(xué)能轉(zhuǎn)變?yōu)闊崮苓M而轉(zhuǎn)化為可使用的機械能。這是由密閉的汽缸內(nèi)燃燒適量的控制比例混合的空氣與燃料的混合物獲得的。汽缸內(nèi)可移動的活塞被燃燒后膨脹的氣體向下推動，汽缸內(nèi)可運動的活塞與連桿的頭端連接，連桿的底部與曲軸連接。當(dāng)活塞向下運動時，曲軸開始旋轉(zhuǎn)?；钊耐鶑?fù)式運動（前后或上下運動）轉(zhuǎn)化為曲軸的旋轉(zhuǎn)運動這為驅(qū)動汽車提供動力。通常情況下，空燃比為151時能獲得叫好的燃燒。然而，進入柴油機的空氣往往很多，但在發(fā)動機轉(zhuǎn)速很慢時只有一部分被利用?？諝獯蠹s由20的氧氣而剩余的80幾乎全為氮氣。這就意味著，每一輪燃料的燃燒需要9000至10000加侖空氣中含的氧氣。四沖程發(fā)動機汽油單獨不會燃燒，必須與氧氣（空氣）混合。這種燃燒即為氧化，是一種釋放在燃油混合物中的能力方式。燃油混合氣必須在密封小室內(nèi)被壓縮并燃燒，這樣燃燒的能量使可移動的活塞工作產(chǎn)生機械能。為保證發(fā)動機的效率，燃燒室盡可能的牢固密封。燃燒室任何的泄露都會造成燃燒能量的耗散，而不會增加由活塞運動產(chǎn)生的機械能。為了紀(jì)念德國工程師尼克勞斯奧托博士，首位在1876年實行這個原則的博士，所以四沖程發(fā)動機又被稱為奧托發(fā)動機，在四沖程發(fā)動機中需要氣缸內(nèi)活塞的四個行程來完成全額作業(yè)周期兩個向上的行程，兩個向下的行程，每個行程是以其發(fā)揮的作用來命名的進氣，壓縮，做功，排氣。1、進氣行程當(dāng)活塞向下運動時，其氣狀的燃料與空氣的混合物通過開啟的進氣閥進入汽缸。2、壓縮行程活塞返回向上運動，進氣門關(guān)閉，混合物在燃燒室內(nèi)被壓縮并且被火花點燃。3、作功行程燃燒的膨脹的氣體使汽缸內(nèi)地活塞向下運動。在做功行程終了時排氣門打開。4、排氣行程活塞隨著排氣門的開啟，又返回向上運動，燃燒后的其他氣體被排出，為下一個進氣形成做準(zhǔn)備。進氣門往往在排氣開始之前開啟。只要發(fā)動機在運轉(zhuǎn)，這四個沖程的循環(huán)就會在每個氣缸內(nèi)周而復(fù)始的運動。兩沖程發(fā)動機兩沖程柴油機完成這四個過程進氣，壓縮，做功，排氣。曲軸的一次旋轉(zhuǎn)或活塞的兩個行程中。氣缸周圍排列著一系列的開口，當(dāng)活塞在行程終了時，開口就會打開。一個鼓風(fēng)機使空氣通過開口進入氣缸。驅(qū)使所有剩余的廢氣通過開啟排氣閥排除氣體，并且使汽缸內(nèi)充滿空氣。這叫做排除廢氣。當(dāng)活塞向上運動時，排氣門關(guān)閉，活塞覆蓋開口。在排氣關(guān)閉時留在活塞上部的空氣被壓縮。在活塞到達上止點之間，所需要的燃料被注入氣缸。即刻因壓縮空氣而產(chǎn)生的熱量將燃料點燃。燃燒一直持續(xù)到被注入的燃料燃燒完畢。在作功行程中，來自燃燒的壓力使活塞向下運動。當(dāng)活塞大約運動到一半的時候，排氣門打開，廢氣排出，活塞繼續(xù)向下運動進氣門打開，新鮮空氣進入氣缸，排出廢氣。發(fā)動機繼續(xù)運轉(zhuǎn)時，則重復(fù)上述整個過程。二者比較假設(shè)，一臺兩沖程發(fā)動機與一臺四沖程發(fā)動機有相同數(shù)量的氣缸，相同的排氣量，壓縮比以及轉(zhuǎn)速，那么，四沖程產(chǎn)生的動力將會是兩沖程的兩倍，因為四沖程做功的次數(shù)是兩沖程的兩倍。然而，這并不是事實，因為有排氣廢氣的過程，做功行程及壓縮行程均被縮短。兩沖程發(fā)動機也需要一個鼓風(fēng)機，使發(fā)動機動力驅(qū)動。兩沖程發(fā)動機，在360的曲軸旋轉(zhuǎn)中大約有160被用來排除廢氣和進入新鮮空氣。在四沖程發(fā)動機中，每720的曲軸旋轉(zhuǎn)中大約有415被用來進氣和排氣。這些數(shù)據(jù)表明，在兩沖程發(fā)動機