488Q天然氣發(fā)動(dòng)機(jī)—總體方案設(shè)計(jì)和計(jì)算

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488Q天然氣發(fā)動(dòng)機(jī)—總體方案設(shè)計(jì)和計(jì)算.rar

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關(guān) 鍵詞：: 天然氣發(fā)動(dòng)機(jī) 總體整體方案設(shè)計(jì) 以及計(jì)算

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A3-供氣系統(tǒng)示意圖.jpg

A3-進(jìn)氣歧管.jpg

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內(nèi)容簡(jiǎn)介：: XX設(shè)計(jì)外文翻譯學(xué)生姓名：XXXX學(xué)號(hào)：XXXXX學(xué)院：機(jī)電工程學(xué)院專(zhuān)業(yè)：XXXXX設(shè)計(jì)(論文)題目：488Q天然氣發(fā)動(dòng)機(jī)總體方案設(shè)計(jì)和計(jì)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(dòng)機(jī)和LPG發(fā)動(dòng)機(jī)是氣體發(fā)動(dòng)機(jī)CNG發(fā)動(dòng)機(jī)的燃料是壓縮天然氣，主要成分是甲烷；LPG發(fā)動(dòng)機(jī)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(jī)相比，氣體單燃料發(fā)動(dòng)機(jī)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(jī)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(dòng)機(jī)）、減壓器（CNG發(fā)動(dòng)機(jī)）等供給LPG或CNG的相關(guān)零部件。2、點(diǎn)火系統(tǒng)：柴油機(jī)是壓燃式發(fā)動(dòng)機(jī)，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(jī)一樣的點(diǎn)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(gè)點(diǎn)火傳動(dòng)裝置，通過(guò)點(diǎn)火正時(shí)傳感器獲得發(fā)動(dòng)機(jī)的點(diǎn)火正時(shí)信號(hào)。增加了以點(diǎn)火模塊、點(diǎn)火線圈及火花塞等零件組成的點(diǎn)火系統(tǒng)。3、控制系統(tǒng)：LPG發(fā)動(dòng)機(jī)與CNG發(fā)動(dòng)機(jī)采用電控，與原機(jī)械式柴油機(jī)相比，各工況點(diǎn)的空燃比、點(diǎn)火提前角、增壓壓力都實(shí)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(diǎn)火正時(shí)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(lái)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(dòng)機(jī)壓縮比比LPG發(fā)動(dòng)機(jī)高但比柴油機(jī)低，而LPG發(fā)動(dòng)機(jī)的壓縮比又可以比汽油機(jī)略高，當(dāng)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(jī)的缸蓋結(jié)構(gòu)上一般都沒(méi)有改動(dòng)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(dòng)機(jī)為了滿足壓縮比的要求，都加大了燃燒室容積。LPG發(fā)動(dòng)機(jī)的基本工作原理：LPG單燃料發(fā)動(dòng)機(jī)的燃?xì)庀到y(tǒng)包含：發(fā)動(dòng)機(jī)控制模塊、點(diǎn)火控制模塊、點(diǎn)火線圈、火花塞、電子節(jié)氣門(mén)、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(dòng)機(jī)和車(chē)輛的性能、排放和安全。液態(tài)的LPG從氣瓶出來(lái)到高壓電磁閥，高壓電磁閥的打開(kāi)受發(fā)動(dòng)機(jī)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(jí)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(dòng)機(jī)的冷卻水進(jìn)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(lái)有兩路氣，一路是一級(jí)減壓經(jīng)怠速燃料控制閥后到混合器，另一路是二級(jí)減壓經(jīng)主燃料控制閥到混合器。一級(jí)減壓的壓力相對(duì)穩(wěn)定，比1個(gè)大氣壓高幾十千帕，為發(fā)動(dòng)機(jī)怠速提供大部份燃料并由ECM對(duì)怠速燃料控制閥進(jìn)行閉環(huán)控制，保證怠速時(shí)混合氣的濃度。二級(jí)減壓壓力受增壓壓力反饋控制，為發(fā)動(dòng)機(jī)全工況提供燃料并由ECM對(duì)主燃料控制閥進(jìn)行閉環(huán)控制，以保證發(fā)動(dòng)機(jī)各工況點(diǎn)混合氣的濃度。點(diǎn)火時(shí)間控制是由儲(chǔ)存在ECM中的標(biāo)定表對(duì)各工況點(diǎn)的點(diǎn)火時(shí)間進(jìn)行開(kāi)環(huán)控制。通過(guò)廢氣旁通控制閥控制增壓器旁通閥的開(kāi)度來(lái)控制增壓壓力。CNG發(fā)動(dòng)機(jī)的基本工作原理：高壓的CNG從氣瓶出來(lái)到高壓電磁閥，高壓電磁閥的打開(kāi)受發(fā)動(dòng)機(jī)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(shí)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(gè)熱交換器，利用發(fā)動(dòng)機(jī)的冷卻水進(jìn)行加熱，以防止管路結(jié)冰堵塞。并且在熱交換器后有一個(gè)節(jié)溫器，通過(guò)控制冷卻水的流量來(lái)控制CNG的溫度。CNG經(jīng)過(guò)節(jié)溫器后到計(jì)量閥，計(jì)量閥上裝有八個(gè)噴嘴，噴嘴的開(kāi)啟時(shí)間受ECM的控制，控制了發(fā)動(dòng)機(jī)各工況點(diǎn)混合氣的濃度。CNG從計(jì)量閥出來(lái)后到混合器，在混合器處與空氣混合后經(jīng)電子節(jié)氣門(mén)進(jìn)入氣缸。點(diǎn)火控制、增壓壓力控制、怠速及高速調(diào)速控制與LPG發(fā)動(dòng)機(jī)相同。目前，汽車(chē)使用天然氣時(shí)，都是將原來(lái)的汽油車(chē)或柴油車(chē)的發(fā)動(dòng)機(jī)進(jìn)行改裝，以適應(yīng)燃燒天然氣。按燃燒天然氣的特點(diǎn)專(zhuān)門(mén)設(shè)計(jì)、制造的發(fā)動(dòng)機(jī)還比較少。根據(jù)汽油機(jī)和柴油機(jī)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(chē)的改裝使用

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