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1、英语论文NUMERICALCONTROLTECHNOLOGYAPPLYCATIONSMostautomobilednginesareinternalcombustion,reciprocating4-strokegasolineengines,butothertypeshavebeenused,includingthediesel,therotary(Wankel),the2-srtoke,andstratifiedcharge.Reciprocatingmeansupanddownorbanckandforth,Itistheupanddown
2、actionofapistoninthecylinderblick,orengineblock.Theblickisanironoraluminumcastingthatcontainsenginecylindersandpassgescalledwaterjacketsforcoolantcirculation.Thetopoftheblockiscoveredwiththecylinderhead.Whichformsthecombustionchanber.Thebottomoftheblockiscoveredwithanoilpanor
3、oilsump.Powerisproducedbythelinearmotionofapistoninacylinder.However,thislinearmotionmustbechangedintorotarymotiontoturnthewheelsofcarsoftrucks.Thepistonisattachedtothetopofaconnectingrodbyapin,calledapistonpinorwristpin.Thebottomoftheconnectingrodisattachedtothecrankshaft.Th
4、econnectingrodtransmitstheup-and-downmotionofthepistontothecrankshaft,whichchangesitintorotarymotion.Theconnectingrodismountedonthecrankshaftwithlargebeaingscalledrodbearings.Similarbearings,calledmainbearings,areusedtomountthecrankshaftintheblock.ShowninFig.1-1Thediameteroft
5、hecylinderiscalledtheenginebore.Displacementandcompressionratioaretwofrequentlyusedenginespecifications.Displacementindicatesenginesize,andcompressionratiocomparesthetotalcylindervolumetocompressionchambervolume.Thetermstrokeisusedtodescribethemovementoftheistonwithinthecylin
6、der,aswellasthedistanceofpistontravel.Dependingonthetypeofenginetheoperatingcyclemayrequireeithertwoorfourstrokestocomplete.The4-strokeengineisalsocalledOttocycleengine,inhonoroftheGermanengineer,Dr.NikolausOtto,whofirstappliedtheprinciplein1876.Inthe4-strokeengine,fourstroke
7、softhepistoninthecylinderarerequiredtocompleteonefulloperatingcycle.Eachstrokeisnamedaftertheactionitperformsintake,compression,power,andexhaustinthatorder,showninFig1-2.1、IntakestrokeAsthepistonmovesdown,thevaporizedmixtureoffuelandairentersthecylinderthroughopenintakevalve.
8、Toobtainthemaximumfillingofthecylindertheintakevalveopensabout10°bef
