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Lesson1.PetrolandDieselEngines汽油发动机机和柴油发动机Theexplosivemixtureofthepetrolengineisprovidedbyacarburettor,butinthecaseofthedieselenginethesupplyiseffectedbyaninjectionorjerkpumpwhichforcesashotoffuelintoeachcylinderinturnaccordingtothecorrectfiringsequence.翻译：汽油发动机由一个化油器输送可燃混合气体，而柴油发动机，由一个喷射泵或柱塞式燃油泵实现燃油供应，此泵根据正确的点火顺序把少量燃油依次压入每个汽缸。Thepumpisactuatedfromacamshaftandtheamountinjectedforeachpowerstrokeisextremelysmallatmaximumoutput,indeeditmaybelessthan0.1cm2,Moreover,thischargemustbemeteredwithgreatandconstantaccuracyevenwhileitisbeingvariablycontrolledtoregulatepowerfromidlingtomaximum.Itwillberealisedthatefficientandeconomicalrunningislargelydependentuponthefuelpump.翻译：通过凸轮轴驱动油泵。每个功率冲程的燃油喷射量在最大输出功率时是非常微小的，实际上，可能小于0.1cm2。而且，此燃油量虽然从怠速到最大速度要进行不同的控制调节，但此燃油量必须非常精确和稳定地进行测量。人们认识到有效和经济的运行主要依靠燃油泵Multi-cylinderenginesarenormallyequippedwithpumpsinunitmonoblocformincorporatingacorrespondingnumberofelements，havingacommoncamshaftandcontrolmeansbutprovidedwithindividualadjustmentsforregulatingtheiroutputandsettingtheirtiming.Anequalquantityoffuelmustbedeliveredbyeachelement,whichiscalibratedseparatelytoapredeterminedrateofdelivery.Timingofthestartofinjectioninrelationtoenginecrankshaftpositionmustalsobeconstantandequaloneachelement,thesettingprocessiscalledphasing.Calibrationandphasingareprecisionoperationstobecarriedoutonlybyskilledservicemechanicswhohavethenecessaryspecialisedequipment.翻译：多汽缸发动机一般情况下装配整体式油泵，把相关的喷射单元组合成一体，共用凸轮轴和控制方式，但可单独调整以调节各自功率输出和设定各自的正时。每个喷射单元必须输送等量燃油,按照预定的输送比率分别校准。与发动机曲轴位置度相关的喷射开始时间在每个喷射单元也必须是恒定相等的。设定的过程被称为调整相位。校准和调整相位是精确的操作，只有熟练的服务机械师用必要的专用工具才能进行，Averyimportantdetailisthatinjectionmustceasecleanlyandabruptlyattheendofthedeliveryperiodwithoutanytraceofafter-dribblefromtheinjector;otherwisecarbondepositsquicklyformonthenozzletipandexcessivesmokewillappearintheexhaust.Therequiredconditionisensuredbythespecialdesignofthepumpdeliveryvalveswhichprovideforaveryrapidcollapseofpressureintheinjectorfuelpipesattheendofinjection翻译：一个非常重要的细节是燃油喷射必须在燃油输送结束时干净且突然地停止，从喷射泵上不留下任何后渗漏的痕迹。否则，在喷嘴尖上很快形成积碳，排气管将冒浓烟。这种要求由专用（专门设计的）输油泵输送气阀来保证，此气阀可以在喷射结束时快速终止喷射泵燃油管的压力。Atanearlystageintheevolutionofthehigh-speeddieselavariabletimingdevicewasintroducedinthepumpdrivecoupling,takingtheformofahelicallysplinedcouplingbymeansofwhichtheangularrelationbetweendrivinganddrivenshaftscouldbevariedbymanualorautomaticcontrol.ThisdevicehasalwaysbeenafeatureofGardnerengineswhereitiscoupledtotheacceleratorcontrol.Insomemakesofenginethehelicallysplinedcouplingisnotusedandtheangulardisplacementoftheshaftsiseffectedbycentrifugallyactuateddevicesoftheswinginglinkorinclinedplanetype.Thefittingofvariabletimingdeviceshasbeendiscardedbysomemanufacturersinfavouroffixedtiming,butinrecentyearstheextensiveadoptionofthedistributortypeoffuelpump,whichincorporatesasimplevariabletimingdevice,hasnowbroughtthisrefinementintomuchmoregeneraluse.翻译：在高速柴油机发展的早期，可变的正时装置被引用到油泵驱动联轴节上，采用螺旋式花键套管的形状，驱动轴和从动轴之间的相对角度可以通过手动或自动控制进行改变。此装置是加德纳发动机的一个特征，总是和加速器控制连接在一起。在一些发动机的制造中，并不使用螺旋式花键套管，通过摇杆或斜面型的偏心操纵装置，曲轴相位角起到同样作用.一些制造商放弃装配可变正时装置，而采用固定正时。但是，最近，装配一个简单可变正时器的分配器型的燃油泵广泛采用，使这精致的附件获得更普遍的使用。Fromtheaboveitwillberealisedthatfundamentaldifferencebetweenpetrolanddieselenginesisthatinthepetrolenginethesourceofheatforignitingthecharge,namelyanelectricspark,isgeneratedoutsidetheengine,andistaken,asitwere,intothewaitingchargeattherequiredinstant.Inthedieselenginethesourceofheatforignitingthechargeiscreatedwithintheenginebycompressingpureairtoadegreethatwillinitiatecombustionandtheninjectingthefuelattherighttimeinrelationtothemovementofthecrankshaft.Itwillhavebeengatheredthatapartfromtheirauxiliaryfeatures,bothclassesofengineareofverysimilarconstruction.Butasthedieseliscalledupontowithstandverymuchgreaterstressesduetohigherpressuresinthecylinders,ithastobeofmoresubstantialconstructionandisthusheavier.翻译：通过以上描述，人们认识到汽油机和柴油机之间的基本差别是汽油机里，点燃混合气体的（也就是一个电火花塞）热源产生于发动机外面，在要求的瞬间，热源被吸进等待的混合气体里。在柴油机里，点燃燃料热源产生于发动机内部，把纯净的空气压缩到开始燃烧的程度，然后，在曲轴运动相连的准确时刻喷射燃油。从收集的资料看，除了辅助的特点外，两种的发动机结构非常相似。但是。由于压力更高，柴油机的汽缸里要求经受大得多的应力，所以，柴油机必须（拥有）更坚固的结构，因而，会增加起其重量。（其重量更重）Bycarefuldesignandbytakingfulladvantageofthemostadvancedmetallurgicaltechniquethepower/weightratiooftheautomotivedieselwassubstantiallyimprovedwithinthecourseofaveryfewyearssothattheweightsofpresent-dayenginesdonotappeartobecapableofmuchfurtherreduction翻译：通过认真设计和完全利用最先进的冶金技术的优点，汽车柴油机的功率/重量比在最近几年里有本质的改进，以致，现在发动机的重量似乎已经降到最低程度（似乎不能再减少）。Lesson2.TheFour-strokeCycle四冲程循环Anyonefamiliarwiththeworkingoftheordinarypetrolengineisawarethatthemotivepowerisproducedbyignitingabovethepistonineachcylinderamixtureofpetrolvapourandair,theresultantcombustionofwhichcausesanexpansionofgasesexertingpressureonthetopofthepiston.Bythismeanstheheatreleasedbythefuelistransformedintowork,thereciprocatingmovementofthepistonsbeingconvertedintorotarymovementofacrankshaftbymeansoftheconnectingrods翻译：熟悉普通汽油发动机原理的人知道，通过点燃每个汽缸里活塞上面汽油蒸气和空气混合气体，混合气体燃烧的结果使气体膨胀，给活塞顶部施加压力而产生动力。通过这种方式，燃料释放的热量被转换成功。活塞的往复运动通过连杆被转换成曲轴的旋转运动。Thefour-strokecycleistheoperatingsequencemorecommonlyemployed.Itrequiresthateachcylinderbe