第一章发动机的工作原理和总体构造

第一章发动机的工作原理和总体构造内燃机的工作原理与总体构造OperationandBasicSystems主要内容Contents发动机的定义及分类Definition&Classifications四冲程发动机及二冲程发动机的工作原理Operation发动机的基本工作系统BasicSystems发动机的产品名称和型号编制规则ProductNamesandTypeEstablishmentRules有关概念和排量的计算Terminology&Concept1.1IntroductionTheinternalcombustion(IC)engineisaheatenginethatconvertschemicalenergyinafuelintomechanicalenergy,usuallymadeavailableonarotatingoutputshaft.内燃机是将热能（来自于燃料化学能）转变为机械能的一种热机。Versussteamenginesandgasturbineenginesareexternalcombustionengines(i.e.，combustiontakesplaceoutsidethemechanicalenginesystem)外燃机

1.1发动机的定义发动机将某一种形式的能量转化为机械能的机器。热机（热能机械能）外燃机内燃机燃气轮机活塞式往复活塞式reciprocatingengines旋转活塞式rotaryengines1.2HistoricalBackgroundForcenturies,manwalkedorusedanimalsfortransportation.After

theinventionofmechanicalpropulsionsystems,peopleusedself-

propelledvehicles,whichmoveundertheirownpower.

Majormilestonesinvehicledevelopmentinclude:

ThefirstfairlypracticalenginewasinventedbyJ.J.E.Lenoir(1822-1900)andappearedonthesceneabout1860.1876Ottowasgivencreditwhenhisprototypeenginewasbuiltin1876.1892By1892,RudolfDiesel(1858-1913)hadperfectedhiscompressionignitionen­gineintobasicallythesamedieselengineknowntoday.1.2EarlyHistory2techno­logicaloccurrencesduringlatterhalfofthe1800sstimulatedtheemergenceoftheICEIn1859,thediscoveryofcrudeoilinPennsylvaniaThepneumaticrubbertirefirstmarketedbyJohnB.Dunlopin1888.1912

ElectricstarterinventedbyCharlesF.Kettering.

FirstusedonaCadillac,thestarterwasproduced

byDaytonElectricLaboratoriesCompany

1.2EarlyHistoryThesteamengineworkingprinciple内燃机发展简史内燃机是在蒸汽机的基础上发明创制的：1700年，英国人钮卡姆制成了直立汽缸，密封式活塞、缸内喷水冷却的蒸汽机；后由瓦特改良；1814——1829年，英国人史蒂芬森制成蒸汽机车，建成世界上第一段铁路；1860年，法国人勒纳（lenoir）仿蒸汽机制成世界上第一台商用煤气机（ŋ=4%）；内燃机发展简史内燃机是在蒸汽机的基础上发明创制的：1876年，德国人奥托制成四冲程火花点火内燃机（ŋ=16%）；1883年，英国人司派尔仿奥托四冲程煤气机创制汽油机；1886年，德国人奔茨制成用汽油机做动力的汽车；1892年，德国人狄塞尔创制柴油机成功，1898年，柴油机作为商品出售，热效率为29%。1.3EngineOperationFour-StrokeSIEngineCycleIntakeorInductionStrokePowerorExpansionStrokeCompressionStrokeExhaustStroke1.3EngineOperationindicatordiagram1.3EngineOperation1、Piston-EngineConstructionPistonsmoveupanddown(orbackandforth)incylindersReciprocatingmotionischangedtorotarymotionbyconnectingrodandacrankpinonthecrankshaft2、OperationApistonstrokeisthemovementofthepistoninthecylinderfromtoptobottom,orbottomtotopFourpistonstrokes-----------intake,compression,powerandexhaust.Takestworevolutionsofthecrankshaft.Four-stroke-cycleengine1.3EngineOperationFour-StrokeCIEngineCycleIntakeorInductionStrokePowerorExpansionStrokeCompressionStroke1.3EngineOperation四冲程柴油机工作原理（seeanimation）/diesel1.htm1.3EngineOperation四冲程柴油机与汽油机比较同：四个冲程—进气、压缩、膨胀和排气异：燃油，可燃混合气形成，着火方式汽油易蒸发，柴油不易挥发混合气形成：高压柴油从喷油器中直接喷入气缸，形成时间很短（燃烧室形状，组织进气涡流）着火方式：自燃温度约600K（320℃）压缩比较大。1.3EngineOperationQuestions:Whatmakestheairorair-fuelmixtureenterintothecylinder?Whatmakesthepistonsmoveupanddowninthecylinders?Whatisthepurposeofthevalves？Whatisthepropertimingofthevalves?Howdothecrankshaftandconnectingrodchangethereciprocatingmotionintorotarymotion？1.3EngineOperationAsinglecylinderfour-stroke-cycleenginehasonlyonepowerimpulseforeverytwocrankshaftrevolutions.Thepistondeliverspoweronlyone-fourthofthetime.四个冲程，只有一个行程做功，运转不平稳；Foramoreevenflowofthepower,mostautomotiveengineshavefourormorecylinders.Thecylindersfireoneafteranothertoprovideasteadypowerflow.常采用多缸的方式;缸数曲轴做功间隔12周21周4半周8¼周1.3EngineOperation1.3EngineOperationAcarengineusesafour-strokecycle--howcantwostrokesaccomplishthesametasks?想一想，两冲程发动机怎么工作？怎样在活塞的两个冲程完成一个（进气、压缩、膨胀和排气）完整的循环？结构特点示功图1.3EngineOperationYoucanseethattwo-strokeenginesareingeniouslittledevicesthatoverlapoperationsinordertoreducethepartcount.1.3EngineOperationTwo-StrokeSIEnginescheduleSpecialDesignofTwo-StrokeEnginesOnonesideofthepistonisthecombustionchamber,wherethepistoniscompressingtheair/fuelmixtureandcapturingtheenergyreleasedbytheignitionofthefuel.Ontheothersideofthepistonisthecrankcase,wherethepistoniscreatingavacuumtosuckinair/fuelfromthecarburetorthroughthereedvalveandthenpressurizingthecrankcasesothatair/fuelisforcedintothecombustionchamber.Meanwhile,thesidesofthepistonareactinglikevalves,coveringanduncoveringtheintakeandexhaustportsdrilledintothesideofthecylinderwall.1.3EngineOperation两冲程汽油机在两个活塞行程内完成进气、压缩、膨胀和排气的工作循环。1、结构三个口：进气口、排气口和扫气口2、工作过程活塞上行：压缩、进气、点燃活塞下行：做功、结束进气、排气、扫气3、总结由于特殊结构，方使得进气、压缩、做功和排气得以在两个冲程中完成；有效行程的大小与孔的位置有关。1.3EngineOperationTwo-StrokeSIEngineCycle1.3EngineOperationTwo-StrokeCIEngineCycle1.3EngineOperationTwo-StrokeoverFourStrokeSIEngineAdvantage优点：PowerStrokeeveryrevolution一周有一个做功行程，运转均匀平稳；SimpleStructure无专门的换气机构，使用方便。Disadvantage缺点：RemainingofExhaustGases不易将废气排除干净；LessEfficientStroke有效行程小于上下止点间距离；BlowoutofAir-FuelMixture扫气时有燃油损失。1.3EngineOperationTwo-StrokeCIEngine1、overtwo-strokeSIengine与二冲程汽油机比较，不同之处：exhaustvalves采用排气门排气；moreinletports进气口不止一个，环布在气缸周围，且经气泵加压；Scavengingwithpureair采用纯空气扫气，没有燃油损失；separatecrankcase不用曲轴箱贮存可燃混合气及空气。2、工作原理Upwardstroke:scavenge,compression,spray,self-ignition活塞上行冲程：换气、压缩、喷油着火；Downwardstroke:expansion,exhaust,intakeandscavenge活塞下行冲程：膨胀做功、排气换气。1.3EngineOperation柴油机与汽油机的特点比较柴油机压缩比大，燃气膨胀充分，膨胀终了燃气温度较低，热量利用程度较好，比汽油机省燃料。柴油机气缸压力较高，机件受力较大，刚度和强度要求较高，与相同功率的汽油机相比，其体积较大，重量也较大