发动机原理English吴建军剖析VIP免费

1第一章发动机性能及其参数[1]三种理想循环1)ottocycle:2)diedelcycle:3)dualcycle;(theefficiencyliesbetween~)isentropiccompression;additionofheat;isentropicexpansion;rejectionofheat;[2]评价理论循环的参数Cyclefuelconversionefficiencyt和MeaneffectivepressurePtt:Thecyclefuelconversionefficiencytisusedtoevaluatethecycleeconomy,whichisdefinedas:(ηtincreaseswiththeincreasingofcompressionratioε,pressureratioλ,isentropicexponentKanddecreaseswiththeincreasingofexpansionratioρ.)Pt:Ptiscycleworkdonebyunitcylindervolume.Itisusedtoevaluatethepowercapabilityofacylinder:(Ptincreaseswithincreasingofpa、、、、kandt.)[3]realcycle实际循环1、intake(induct)stroke2、compressionstroke3、power(combustion)stroke4、exhauststroke[4]Whichlossesexistedinrealcyclecomparedwithidealcycle?explaineverylossandtheformingreason.(实际循环与理想循环相比，存在的损失及其形成原因。)1)Heattransfer.Heattransferfromunburnedmixturetothecylinderwalls.Thepressureattheendofcombustionintherealcyclewillbelower.2)Finitecombustiontime.Finitetimerequiredtoburnthecharge.Thepeak12121101QQQQQQWtStVWp2pressureintheengineisbelowtheidealcyclepeakpressurevalue.3)Incompletecombustion.combustionofthecylinderchargeisincomplete;theexhaustgasescontaincombustiblespecies.4)Exhaustblowdownloss.Thegaspressureattheendofexpansionstrokeisreduced.5)Creviceeffectsandleakage.Theseeffectsreducethecylinderpressure.6)Pumpingloss.Theworkisusedtoovercometheresistanceininletandexhaustpassages.[5]enginesindicatedparametersa(发动机指示指标及作用？和类容)1>概念及作用：.Indicatedparameters:Theparametersarecalculatedonbasisoftheworkdonebyworkingfluidtopistons.itiswidelyusedtoevaluatetheconversionefficiencyofheatintopowerpercycleandiswidelyusedinengineresearchfield.2>内容1、IndicatedworkpercycleWi（循环指示功）2、Indicatedmeaneffectivepressure(imep)Pmi（平均指示压力）3、IndicatedpowerPi(指示功率)Pi(kw)=[Pmi(Mpa)*Vs(L)*n(r/min)*i]/[30*tao]（i为汽缸数，tao为冲程数）4、Indicatedefficiencyηi（指示热效率）5、Indicatedspecificfuelconsumptionbi（指示油耗率）)()/()/(32mVmNWmNimeppsimiuiiiiBHPQW3106.3310)()/())/((kWPhkgBhkWgbii3指示热效率与指示油耗率的关系[6]enginebrakeparameters(何谓发动机有效指标及作用)1>概念：Enginebrakeparametersarebasedonenginecrankshaftoutputwork.Itisusedtoevaluateeconomicanddynamicperformanceofanengine。2>内容：1.BraketorqueTtqandpowerPe（有效转矩和有效功率）2.BrakeworkWeandbrakemeaneffectivepressurePme(有效功和平均压力)We=Wi-WmWi---指示功；Wm---机械损失功3.Brake(thermal)efficiencyηe（有效热效率）4.Brakespecificfuelconsumption(bsfc)be（有效油耗率）热效率有油耗率的关系5.EnginespecificpowerPL（升功率）iuibH6106.3)()/()/(32mVmNWmNbmeppsemeueeeBHPQW31106.3310)()/())/((kWPhkgBbsfchkwgbeeeuebH6106.3SeLiVPP4[7]enginemechanicalefficiency(机械效率)定义：Theratioofthebrake(oruseful)powerdeliveredbytheenginetotheindicatedpoweriscalledthemechanicalefficiencyηm:imiemPPPP1.影响因素：Thefactsthatinfluenceitare:thepeakcombustionpressuresincylinder,enginespeedorpistonmeanspeed,engineloads,thecharacteristicoflubricationandtemperatureofcoolingwater,andtheconditionsofengineruns.第二章发动机的换气[1]gasexchangeprocessesoffour-strokeengine.（四冲程发动机换气过程）Thegasexchangeprocessofanengineconsistsofthedurationfromopeningtheexhaustvalvetoclosingtheinletvalve.itcanbadividedintofourphases1.blowdown自由排气2.displacement强制排气3.inductionprocess进气行程4.val...