车辆工程专业英语PPT课件-UNIT-5--DIESEL-FUEL-INJECTION

No.10039UNIT5DIESELFUELINJECTIONTEXTAOverviewofDieselFuelInjectionPROFESSIONALENGLISHNo.10039UNIT5DIESELFUELINJECTIONTEXTAOverviewofDieselFuelInjectionOverallDieselFuelSystemInjectorPumpTypesDieselInjectorTypesGlowPlugandIntakeAirHeaters本次课学习内容No.10039本次课学习目标掌握柴油机喷油系统的组成掌握主要部件的型式及原理掌握有关的专业名词与术语了解翻译技巧—省略NEWWORDSschematic[ski'mætik]a.示意性的alert[ə'lə:t]v.向…发出警报；clog[klɔg]v.&n.阻塞，堵塞nozzle['nɔz(ə)l]n.喷嘴jam[ʤæm]v.&n.堵塞，拥挤trap[træp]n.圈套，陷阱，捕集器plunger['plʌnʤə]n.柱塞，活塞rack[ræk]n.齿条barrel['bær(ə)l]n.桶；v.装入桶内helix['hi:liks]n.螺旋，螺旋状物cutaway['kʌtwei]a.切去一部分的，剖面的instantly['instæntli]ad.立即地，即刻地variation[veəri'ei∫ən]n.变化，变更，变种，变调protrude[prə'tru:d]v.突出，伸出dull[dʌl]v.变迟钝；a.迟钝的，不鲜明的，无光泽的readily['redili]ad.容易，欣然，乐意地waterseparator（油）水分离器inlineinjectorpump直列式喷油泵deliveryvalve出油阀segmentgear扇形齿轮transferpump输送泵，输油泵inlinefuelpump管路串接式燃油泵inwardopeninginjector孔式喷油器outwardopeninginjector轴针式喷油器glowplug预热塞pumpingchamber预压缩室（腔）wiremesh（金属、钢、塑料）丝网，线网PHRASESANDEXPRESSIONSOverviewofDieselFuelInjectionDieselenginesareusedonsomecarsandlighttrucks.Thedieselengineusestheheatofcompression,insteadofasparkplug,toignitethefuel.Dieselfuelinjectionissimilartogasolineinjection,butrequireshigherinjectionpressures.Airisdrawnintothecylinderandhighlycompressed.Thecompressionissohighthatthecompressedairwillreachtemperaturesof1000℉(538.2℃).Attheprecisetimethepistonhascompletedthecompressionstroke,dieselfuelissprayedintothecombustionchamber,oranoffsetprechamber.Theintenseheatofthecompressedairignitesthefuel,andthepowerstrokefollows.OverallDieselFuelSystemAschematicofadieselfuelsystemlayoutisshowninFig.5-1.Typicaldieselsystemcomponentsincludethetank,fuelpump,filter,injectionpump,injectors,andthenecessaryfuellines.ThesysteminFig.5-1istypicalofnewersystemsthatutilizeacomputer-controlledelectronicfuelinjectionpump.Fig.5-1.AnoverallviewofoneparticulardieselfuelinjectionsystemasusedwithaV-8engine.WaterInFuelSensorSomevehiclesareequippedwithawaterinfuelsensorthatwillalertthedrivertothefactthatwaterispresentinthefuel[1].Thewatermaythenbedrawnoffthroughavalveinthebottomofawaterseparator.Waterisextremelydamagingtotheinjectionsystem.FuelFilterDieselfuelmustbekeptcleantoavoidinjectorsystemtrouble.Verysmallparticlesareenoughtocloginjectornozzlesorjamtheinjector.Dieselfuelsystemstypicallyuseoneormorefilterstotrapdirtandotherdeposits.DieselInjectionPumpDieselfuelisinjecteddirectlyintothecylinderatthetopofthecompressionstroke.Duetothehighcompression(around22:1)usedindieselengines,thedieselinjectionpumpmustbecapableofproducinghighpressures.Injectorpumppressuresvarygreatlydependingonthepumpandengine.Pressurescanrangefrom3000-15,000psi(20685-103425kPa).HowtheInjectorPumpProducesPressureByusingaplungeroperatinginacylinder,thepumptrapsfuelaheadoftheplunger.Whentheplungerisforcedup,itbuildspressureonthefuel.Pressurewillbeincreasedtothepointatwhichtheinjectorwillopenandsprayfuelintotheengine.Pumpscanuseasingleplungerforeachinjectororasinglepump(oftenconsistingoftwoormoreopposingplungers)toserveallinjectors[2].InjectorPumpTypesThereareanumberofinjectorpumpdesigns.Themostcommonlyusedautomobileandlighttruckdieselinjectorpumpsareclassifiedasinlineordistributor.Botharemechanicalpumpsthatpressurizethefuelanddeliverittothecylindersatthepropertimeforeach.InlineInjectorPumpInlineInjectorPumpTheinlineinjectorpumpusesaseparatecylinderplunger-camforeachcylinder.Theyarecontainedinastraightrowinacommonhousing.Thecamsarepartofacommoncamshaftdrivenbytheengineatone-halfenginespeed.Drivemaybebychain,belt,orgear.Fuelfromthefuelpumpisfedtoalloftheplungerassemblies.Asthecamshaftrotates,eachoftheplungersismovedupanddownintheircylinders.Asinglecontrolrackorrailwithgearteethalongonesideismeshedwitheachplungerassembly.Bymovingthecontrolrack,theeffectivepumpaction(amountoffuelpumped)ofallplungerscanbeadjusted.InlineInjectorPumpMeteringControlEachplungeroperatesinaseparatecylinderorbarrel.Thetopsectionoftheplungerhasawidebandorgroovecutaway.Oneedgeofthecutformsahelix(spiralshape).Theplungeralsohasaverticalslotreachingfromthetopoftheplungerdownintothecutawayarea.Thebottomoftheplungerisconnected,bymeansofaflange,tothetoothedcontrolsleevethatmesheswiththecontrolrackteeth.Whenthecontrolrackismovedbackandforth,theplungerwillrotateinthecylinder,sotheeffectivepumpaction,orstroke,willbechanged.InjectorPumpDeliveryValveFuelflowingfromthepumpcylinderisforcedthroughadeliveryvalveonitswaytotheinjector.Thefuelflowforcesthedeliveryvalvefromitsseat.Whenthehelixuncoversthecylinderports,fuelpressureinthepumpcylinderdropsinstantly,Thiscausesthedeliveryvalveplungertoquicklyreturntoitsseat.Insodoing,thevolumeinthedeliveryline(injectorhousing,linetoinjectoranddeliveryvalvespringchamber)issuddenlyincreasedbytheamountofthedeliveryvalveplungertravel.Thisincreaseinvolumecausesasuddenreductionindeliverylinepressurethatallowstheinjectornozzlevalvetosnapshutquicklyandcleanlywithoutdripping[3].Adeliveryvalveisusedonbothinlineanddistributortypepumps.Figure5-2.Pumpplungerconstruction.Whenthecontrolrackismoved,theplungerwillbeforcedto