汽车专业英语PPT课件-section 1ppt课件Chapter 2 7-2 9

Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,NewWords,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,AlthoughMPIprovidesadrasticimprovementinresponseandcombustionquality,itisstilllimitedduetofuelandairmixingpriortoenteringthecylinder.Tofurtherincreasethrottleresponseandcombustionefficiency,whileloweringfuelconsumptionandincreasingoutput,systemsmayusedirectinjection.Gasolinedirectinjectionenginesareengineeredtoinjectthegasolinedirectlyintothecylinderinamannersimilartodieseldirectinjectionengines(Fig.2-14).Directinjectionisdesignedtogetbetterfueleconomy.Thisisaccomplishedbyenablingcombustionofanultra-leanmixtureundermanyoperatingconditions.Directinjectionisalsodesignedtoallowhighercompressionratios,deliveringhigherperformancewithlowerfuelconsumption.Currently,directinjectiongasolineenginesarebeingdeployedthroughouttheworldinpassengercars.,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,Fig.2-14Gasolinedirectinjection,Avarietyofair-fuelmixturescanbecreatedaccordingtochangesinthefuelinjectiontiming.TheGDIengineprovidesbothlowerfuelconsumptionandhigheroutput.Thisisachievedwiththeuseoftwocombustionmodes.ThesetwomodesarerepresentedinFigure2-15.,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,Figure2-15MitsubishiGDIusestwocombustionmodes,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,Ultra-leanCombustionMode.Undermostnormaldrivingconditions,uptospeedsof120km/h,theMitsubishiGDIengineoperatesinultra-leancombustionmode,resultinginlessfuelconsumption.Inthismode,fuelinjectionoccursatthelatterstageofthecompressionstrokeandignitionoccursatanultra-leanair-fuelratioof30-40.Thisoperatingmodeisalsocalledasstratified-chargemode.SuperiorOutputMode.WhentheGDIengineisoperatingwithhigherloadsorathigherspeeds,fuelinjectiontakesplaceduringtheintakestroke.Thisoptimizescombustionbyensuringahomogeneous,coolerair-fuelmixturewhichminimizesthepossibilityofengineknocking.Thismodeisalsocalledashomogeneous-chargemode.,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,TwomainoperatingmodesofVolkswagenAGsfuelstratifiedinjection(FSI)whichusesmoreoperatingmodesandFSIsfuel-savingpotentialisshowninFigure2-16.AtypicalpulseinjectionsystemwithdirectinjectionisgiveninFig.2-17.,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,Figure2-16Mainoperatingmodesandfuel-savingpotentialofVolkswagenAGsFSIdirect-injection,Chapter2InternalCombustionEngine2.7Gasolinedirectinjection,Fig.2-17Gasolinedirectinjectionsystem,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,NewWords,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,NewWords,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,2.8.1ConventionalSystemTypicaldieselsystemcomponentsincludethefueltank,fuelpump,fuelfilter,injectionpump,injectors,andthenecessaryfuellines(Fig.2-18).ThesysteminFig.2-19istypicalofnewersystemsthatutilizeacomputer-controlledelectronicfuelinjectionpump.,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Fig2-18Aconventionaldieselfuelinjectionsystem,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Fig2-19.Ancomputercontrolleddieselfuelinjectionsystemwithaxial-pistondistributorinjectionpump,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,FuelFilter.Dieselfuelmustbekeptcleantoavoidinjectorsystemtrouble.Verysmallparticlesareenoughtocloginjectornozzles.Dieselfuelsystemstypicallyuseoneormorefilterstotrapdirtandotherdeposits.InjectionPump.Duetothehighcompression(around22:1)usedindieselengines,thedieselinjectionpumpmustbecapableofproducinghighpressures.Thereareanumberofinjectionpumpdesigns.Themostcommonlyusedautomobileandlighttruckdieselinjectionpumpsareclassifiedasinlineordistributor.Theinlineinjectionpump（Figure12-18）usesaseparatecylinderplunger-camunit（Fig.2-20）foreachcylinder.Theseunitsarecontainedinastraightrowinacommonhousing.,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Figure2-20.Pumpplungerconstruction.Whenthecontrolrackismoved,theplungerwillbeforcedtorotatebythesegmentedgearsleeveactingontheplungerflange.,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Fig.2-21Cutawayviewofadistributortypeinjectionpump.,ThedistributorinjectionpumpisshowninFigure2-21.Youwillnotethatasingle,double-plungertypepumpservesallinjectoroutlets.Asingledeliveryvalveislocatedintherotor.AdistributortypefuelinjectionpumpwitchiselectronicallycontrolledisshowninFig.2-22.,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Fig.2-22Aelectronicallycontrolleddistributortypefuelinjectionpump.Fuelshutoffsolenoidiscontrolledbythepowertraincontrolmodule(PCM).Whenenergized,itisdesignedtocompletelystopthefuelflowintotheinjectionpump.,Chapter2InternalCombustionEngine2.8DieselFuelInjectionSystem,Injector.Therearemanydifferentinjectordesigns,butallareavariationoftwobasictypes-inwardopeningandoutwardopening.Dieselspraypatternswillvarydependinguponenginedesign.GlowPlugandIntakeAirHeaters.Toaidinignitingthecompressedair-fuelmixduringcoldstarting,dieselenginesuseglowplugsandintakeairheaters.Theglowplugisanelectricallyoperateddevicethatprotrudesintotheprecombustionchamber.Onlaterengines,theglowplugsareturnedonandoffautomatically.Intakeairheaterswarmtheairasitpassesthroughonitswaytotheintakemanifold.Theheaterelementisawiremeshthatiselectricallyheated.Thecomputerenergizestheheaterelementbeforecranking.,Chapter2InternalCombustionEngine2.9Commonrailinjectionsystems,NewWords,Chapter2InternalCombustionEngine2.9Commonrailinjectionsystems,Newerdieselenginesareequippedwithcommonrailinjectionsystems(Fig.2-23toFig.2-26).Commonrailsystemsaredirectinjection(DI)systems.Theinjectorsnozzlesareplacedinsidethecombustionchamber.Thepistontophasadepressionwhereinitialcombustiontakesplace.Theinjectormustbeabletowithstandthetemperatureandpressureinsidethecylinderandmustbeabletodeliverafinesprayoffuelintothoseconditions.Thesesystemshaveahighpressurefuelrailconnectedtoindividualinjectors.,Chapter2InternalCombustionEngine2.9Commonrailinjectionsystems,Theinjectorsarecontrolledbyacomputerthatattemptstomatchinjectoroperationtotheoperatingconditionsoftheengine.Therearetwotypesofinjectors:solenoid-typeandpiezoelectric(Fig.2-27andFig.2-28).Newerdieselfuelinjectorsrelyonstackedpiezoelectriccrystalsratherthansolenoids.Piezoelectric-crystalsquicklyexpandwhenelectricalcurrentisappl