488Q天然氣發(fā)動機—總體方案設(shè)計和計算

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488Q天然氣發(fā)動機—總體方案設(shè)計和計算.rar

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關(guān) 鍵詞：: 天然氣發(fā)動機總體整體方案設(shè)計以及計算

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A3-進氣歧管.jpg

A3-排氣管罩.jpg

A3-排氣歧管.jpg

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內(nèi)容簡介：: XX設(shè)計外文翻譯學(xué)生姓名：XXXX學(xué)號：XXXXX學(xué)院：機電工程學(xué)院專業(yè)：XXXXX設(shè)計(論文)題目：488Q天然氣發(fā)動機總體方案設(shè)計和計算指導(dǎo)教師：XXXXXXXXX年X月XX日英文翻譯CNGengineandaLPGengineisgasengine.FuelCNGengineiscompressednaturalgas,themaincompositionismethane,LPGenginefuelisliquefiedpetroleumgas(LPG),itsmaincompositionispropaneandbutane.Comparedwiththeoriginaldieselengine,gassinglefuelenginemainlyexistthefollowingdifferences:1,Thefuelsupplysystem:Canceltheoriginaldieselenginefuelinjectionsystemofrelatedpartsandcomponents,increasedtheevaporationpressureregulator(LPGengine),pressurereducer(CNGengine),andothersuppliesLPGorCNGrelatedspareparts.2,Theignitionsystem:Dieselengineisacompressionignitionengine,theLPGandCNGfuelfeatureduetothelimit(antiknockperformanceofvibration)isthesamelightasgasolineengine.Aftertheycancelledtheinjectorintheoriginalfuelinjectorholeoncylinderheadtothesparkplughole.Aftercanceledtheoilpump,oilpumpintheoriginalinstallationlocationonaignitiondrivingdevice,engineignitiontimingsignalswereobtainedthroughtheignitiontimingsensor.Addedtotheignitionmodule,ignitioncoilsandsparkplugignitionsystemcomposedofparts.3,Thecontrolsystem:LPGenginetoCNGengineadoptselectriccontrol,comparedwiththeoriginalmechanicaldieselengine,thepointofair-fuelratio,ignitionadvanceAngle,superchargingpressureformoreprecisecontrol,inordertomeetthecontrolrequirements,increasethecorrespondingMAP,MAT,ECT,ignitiontimingandoxygenconcentrationandothersensors.4,Compressionratio:Theselectionofcompressionratioiscloselyrelatedtothefuelantiknockperformance,antiknockperformanceismeasuredbythefueloctanenumber,thehighertheoctanenumberantiknockperformance,thebetter,thecommonlyusedseveralkindsoffuelaccordingtotherankofoctanenumber:dieselandCNG(methane),propane,butane(LPG)isamixtureofpropaneandbutane,andgasoline.BasedonthecharacteristicsofthiskindoffuelCNGenginecompressionratiothanLPGenginegenerallyhighbutislowerthandiesel,andLPGenginescompressionratiocanbeslightlyhigherthanthegasolineengine,ofcourse,becauseofLPGisamixtureofpropaneandbutane,differentmixingproportionalsoaffectthecompressionratio.OnthebasisofthedieselenginedesignimprovementsforLPGandCNGengine,inordertoreducethecompressionratioyouneedtoincreasethecombustionchambervolume,asaresultofthedieselenginecylinderheadstructuregenerallyhavenochange,onlythepistoncombustionchambervolumeincrease.Therefore,LPGandCNGengineinordertomeettherequirementsofcompressionratio,increasethecombustionchambervolume.ThebasicworkingprincipleofLPGengine:LPGsinglefuelenginegassystemincludes:theenginecontrolmodule,ignitioncontrolmodule,ignitioncoils,sparkplugs,electronicthrottle,mixer,themainfuelcontrolvalves(FTVvalve),idlespeedcontrolvalve,evaporatingpressureregulator,pressuresolenoidvalve,exhaustbypassvalveandsurgevalve.Inaddition,alsoincludingallkindsofsensorsandwiringharness.Thesystemcontrolstheengineandvehicleperformance,safetyandemissions.TheprinciplediagramoftheLPGenginesystemLiquidLPGcylindersfromoutinhighpressuresolenoidvalve,highpressuresolenoidvalveopeningiscontrolledbytheengineECM,LPGafterhighpressuresolenoidvalvetotheevaporationoftheliquidpressureregulator,theevaporatingpressureregulatorCanonoftwo-stagedecompressionevaporationvaporizationintogaseousLPG,duetotheLPGevaporationvaporizationneedtoabsorbalotofheat,sotheevaporationpressureregulatorwithenginecoolingwaterisheated,inordertopreventtheevaporationpressureregulatoricejam.Parttworoadfromtheevaporatingpressureregulator,allthewayisprimarydecompressionafteridlefuelcontrolvalvestothemixer,theotherissecondarystressthemainfuelcontrolvalveallthewaytothemixer.Levelofthereliefpressureisrelativelystable,higherthan1atmdozensofKpa,providemostofthefuelfortheengineidlespeedandtheECMonidlefuelcontrolvalveclosedloopcontrol,ensurethattheidlewhentheconcentrationofthemixture.Secondaryreliefpressuresuperchargingpressurefeedbackcontrol,toprovidefuelfortheengineallconditionandbytheECMtoclosedloopcontrol,themainfuelcontrolvalvestoguaranteeengineworkingconditionofeachpointoftheconcentrationofthemixture.IgnitiontimingcontroltableisstoredintheECMcalibrationonthepointofignitiontimeforopenloopcontrol.Throughtheexhaustbypasscontrolvalvecontrolsuperchargerby-passvalveopeningtocontrolthechargingpressure.ThebasicworkingprincipleoftheCNGengine:HighpressureofCNGcameoutfromthecylindertothehighpressuresolenoidvalve,highpressuresolenoidvalveopeningiscontrolledbytheengineECM,highpressureofCNGafterhighpressuresolenoidvalvetothepressurereducer,afterpressurereducerofCNGpressurefrom20Mpa(fullbottlesofoil-gaspressure)to6to9bar,becauseoftheCNGdecompressionafterthetemperaturedroppedsubstantially,soafterthepressurereducerhasaheatexchanger,theuseoftheenginecoolingwaterforheating,inordertopreventthepipelineicejam.Andintheheatexchangerhasathermostat,bycontrollingtheflowofcoolingwatertocontrolthetemperatureoftheCNG.CNGafterthermostattometeringvalve,meteringvalveisequippedwitheightnozzle,thenozzleopeningtimeiscontrolledbytheECM,controltheengineworkingconditionofeachpointoftheconcentrationofthemixture.CNGisoutofthemeteringvalvetothemixer,afterinthemixermixeswiththeairbytheelectronicthrottleintothecylinder.Ignitioncontrol,boostpressurecontrolandidlespeedandhighspeedcontrolofmotorspeedcontrolisthesameastheLPGengine.Atpresent,thedomesticcarusingnaturalgas,aretheoriginalcarpetrolordieselenginetobemodified,toadapttotheburningnaturalgas.Accordingtothecharacteristicsofthecombustiongasspecializeddesign,themanufactureofthemotorisless.Accordingtotheworkingprincipleofgasolineengineanddieselengine,theworkingsofaswitchtonaturalgascanhavethefollowingkinds:1,ThemodifiedgasolinevehiclesTheworkingprincipleofusingnaturalgasasafuelisthesameastheoriginalgasolineengine.Willbestoredinhigh-pressurecylindersafterpressurerelieftothemixerofnaturalgas,inthemixedwithair,intothecylinder.Stillusetheoriginalsparkplugintheengineignitionsystem.Theoriginalgasolineenginescompressionratiodoesntchange,thestructureoftheoriginalenginebasicallyremainunchanged,justinadditiontotheaircylinder,pressurereducingvalveofthegasandthecorrespondingswitch.Modificationcostislow,andusenaturalgasorgasolinebothfuelcanworkwhilegasantidetonatingqualityisverygood,allowedtoworkatahighercompressionratio,butbecauseinamodifiedinordertomaketheoriginalworkcanstillbeusedgasolineengine,sotheoriginalenginescompressionratiohasnotchanged,tolossofenginepowerare10%20%.Inordertoreducethepowerloss,canbeinwhenconvertedtoincreasethecompressionratiooftheoriginalgasolineengine(themostsimplewaytogoisdugcylindercoverpart),andchangingtheignitionadvanceAngleinordertomeettheneedsoftheworkofnaturalgas.Althoughthiscanreducetherateofloss,butwithgasolinetoworktherewillberiskofdetonation,evencantwork.Itisdifficulttoreturntotheoriginalgasolineengineworks.Sothecar,petrolenginecompressionratiogenerallyremainthesame.2,DieselcarmodifiedTherearetwokindsofmethod.Thefirstkindofmethodisbasicallyremainunchanged,theoriginaldieselenginestructureaccordingtoelectricignitionmethods,namely,accordingtotheworkingprincipleofgasolineengine(Ottocycle).Removeallofyouroriginaldieselenginefuelsystemwillbereducedtogascompressionratiocanundertakenumerical(higherthangasolineengines,general(810):1)inadditiontonaturalgasfuelsystemcomponents,aircylinder,pressurereducingvalve,mixer,etc,addelectricignitionsystem,shouldbeonlysinglecarfuelgasburningnaturalgas.Thismodifiedmethodissimpler,technologyismature,butcantworkwithdiesel,andenginepowerlossisbigger,isabout65%70%thatoftheoriginaldieselengine.Thesecondmethodistheoriginaldieselenginefuelsystemischangeless,coupledwiththesamegasfuelsystemasabove,averagecompressionratiowithoutchanging.Enginecylinderafterinhaledairandgasmixture,theoriginaldieselinjectorintoasmallamountofdieselfuelforignition.Aftercompressiveignitiondiesel,litthegasandairmixtureintothework,thisisdualfuelgasengine.Itsbasicworkingprincipleis:startwiththedieseloil,addloadtonegativepressureintheairandgasmixerdiaphragminstitutions,throughthepumproddieselhighpressureoilpumprackislimited,whilethedriveristheacceleratorpedalnowonlytoincreasetheflowofnaturalgas.Theworkingsofadualfuelnotonlylosepower,andbynaturalgascombustionperformanceisgood,alsothantheoriginaldieselenginepowerincreasesslightly.Thisisbecausetheenginecompressionratioishigh,theoriginalbecauseofexcessaircoefficientislarger.Themodifiedmethodsoftheoriginaldieselenginechangestheleast,andwhenthegasisinshortsupplycanalsobeconvertedtothediesel.Butthiswayofworkinginthemiddleandlowload,economyandemissionsarenotsogood.Therefore,withoutanadditionalmeansofovercomethesedisadvantages,isnotsuitableforcitybus.Itisbestthatinthelongterm,highloadofcarsandlong-distancetransportationvehiclesusemodifiedinthisway.Moderntechnologyadvancedautomotivefuelsystemsmostlywithcomputercontrolofelectronicfuelinjectionsystem.Istousethecomputerautomaticallyaccordingtotheconditionsofusetochangetheelectronicsprayvalvebodyemitsthegasolineordiesel,flowrateandignitiontime.Liketoswitchtonaturalgasasfuel,needtoreplacepetrolordieselelectronicinjectionvalvewithorelectronicinjectionvalveofthegas,tochangethecomputercontrolsoftwareprogram,suchascanbeburningnaturalgasnaturalgasengines.Ofcourse,theothercomponentsofnaturalgasfuelsystemandaircylinder,pressurereducingvalveisnecessary.中文譯文CNG發(fā)動機和LPG發(fā)動機是氣體發(fā)動機CNG發(fā)動機的燃料是壓縮天然氣，主要成分是甲烷；LPG發(fā)動機的燃料則為液化石油氣，其主要成分是丙烷和丁烷。與原柴油機相比，氣體單燃料發(fā)動機主要存在以下方面的差別：1、燃料供給系統(tǒng)：取消了原柴油機的燃油噴射系統(tǒng)相關(guān)的零部件，增加了蒸發(fā)調(diào)壓器（LPG發(fā)動機）、減壓器（CNG發(fā)動機）等供給LPG或CNG的相關(guān)零部件。2、點火系統(tǒng)：柴油機是壓燃式發(fā)動機，而LPG和CNG由于受燃料特性限制（抗爆振性能）采用的是與汽油機一樣的點燃方式。在取消了噴油器后，將原缸蓋上的噴油器孔改為了火花塞孔。在取消了油泵后，在原油泵安裝位置裝上了一個點火傳動裝置，通過點火正時傳感器獲得發(fā)動機的點火正時信號。增加了以點火模塊、點火線圈及火花塞等零件組成的點火系統(tǒng)。3、控制系統(tǒng)：LPG發(fā)動機與CNG發(fā)動機采用電控，與原機械式柴油機相比，各工況點的空燃比、點火提前角、增壓壓力都實現(xiàn)了更精確的控制，為滿足這些控制要求，增加了相應(yīng)的MAP、MAT、ECT、點火正時以及氧濃度等傳感器。4、壓縮比：壓縮比的選取與燃料的抗爆震性能密切相關(guān)，抗爆震性能是用燃料的辛烷值來衡量，辛烷值越高抗爆震性能越好，常用的幾種燃料按辛烷值高低排序依次為：柴油、CNG（甲烷）、丙烷、丁烷（LPG是丙烷和丁烷的混合物）和汽油。根據(jù)這種燃料特性，一般CNG發(fā)動機壓縮比比LPG發(fā)動機高但比柴油機低，而LPG發(fā)動機的壓縮比又可以比汽油機略高，當然，由于LPG是丙烷和丁烷的混合物，混合比例不同也影響其壓縮比的選擇。由于柴油機的缸蓋結(jié)構(gòu)上一般都沒有改動的余地，只有將活塞上的燃燒室容積加大。因此，LPG和CNG發(fā)動機為了滿足壓縮比的要求，都加大了燃燒室容積。LPG發(fā)動機的基本工作原理：LPG單燃料發(fā)動機的燃氣系統(tǒng)包含：發(fā)動機控制模塊、點火控制模塊、點火線圈、火花塞、電子節(jié)氣門、混合器、主燃料控制閥（FTV閥）、怠速燃料控制閥、蒸發(fā)調(diào)壓器、高壓電磁閥、廢氣旁通控制閥和喘振閥構(gòu)成。另外，還包括各種傳感器和線束。整套系統(tǒng)控制著發(fā)動機和車輛的性能、排放和安全。液態(tài)的LPG從氣瓶出來到高壓電磁閥，高壓電磁閥的打開受發(fā)動機ECM的控制，液態(tài)的LPG經(jīng)高壓電磁閥后到蒸發(fā)調(diào)壓器，在蒸發(fā)調(diào)壓器內(nèi)經(jīng)兩級減壓蒸發(fā)汽化變?yōu)闅鈶B(tài)LPG，由于LPG蒸發(fā)汽化需要吸收大量的熱量，因此蒸發(fā)調(diào)壓器接有發(fā)動機的冷卻水進行加熱，以防止蒸發(fā)調(diào)壓器結(jié)冰堵塞。從蒸發(fā)調(diào)壓器出來有兩路氣，一路是一級減壓經(jīng)怠速燃料控制閥后到混合器，另一路是二級減壓經(jīng)主燃料控制閥到混合器。一級減壓的壓力相對穩(wěn)定，比1個大氣壓高幾十千帕，為發(fā)動機怠速提供大部份燃料并由ECM對怠速燃料控制閥進行閉環(huán)控制，保證怠速時混合氣的濃度。二級減壓壓力受增壓壓力反饋控制，為發(fā)動機全工況提供燃料并由ECM對主燃料控制閥進行閉環(huán)控制，以保證發(fā)動機各工況點混合氣的濃度。點火時間控制是由儲存在ECM中的標定表對各工況點的點火時間進行開環(huán)控制。通過廢氣旁通控制閥控制增壓器旁通閥的開度來控制增壓壓力。CNG發(fā)動機的基本工作原理：高壓的CNG從氣瓶出來到高壓電磁閥，高壓電磁閥的打開受發(fā)動機ECM的控制，高壓的CNG經(jīng)高壓電磁閥后到減壓器，經(jīng)減壓器后CNG的壓力由20MPa（滿瓶時氣壓力）降到6到9Bar，由于CNG減壓后溫度大幅度下降，因此在減壓器后接有一個熱交換器，利用發(fā)動機的冷卻水進行加熱，以防止管路結(jié)冰堵塞。并且在熱交換器后有一個節(jié)溫器，通過控制冷卻水的流量來控制CNG的溫度。CNG經(jīng)過節(jié)溫器后到計量閥，計量閥上裝有八個噴嘴，噴嘴的開啟時間受ECM的控制，控制了發(fā)動機各工況點混合氣的濃度。CNG從計量閥出來后到混合器，在混合器處與空氣混合后經(jīng)電子節(jié)氣門進入氣缸。點火控制、增壓壓力控制、怠速及高速調(diào)速控制與LPG發(fā)動機相同。目前，汽車使用天然氣時，都是將原來的汽油車或柴油車的發(fā)動機進行改裝，以適應(yīng)燃燒天然氣。按燃燒天然氣的特點專門設(shè)計、制造的發(fā)動機還比較少。根據(jù)汽油機和柴油機工作原理不同，改用天然氣的工作方式可以有以下幾種:1、汽油車的改裝使用

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