机械原理 英汉双语 教学课件 作者 张春林 Chapter 12 Fluctuation and Regulation in Speed of Machines.pptx

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1、Chapter12FluctuationandRegulationinSpeedofMachines1.ForcesActingonaMachine(1)WorkingresistanceWorkingresistancereferstothetypesofmachines.(2)DrivingforceThedifferentprimemotorshavedifferentoperatingpeculiarities.Therelationshipbetweenthedrivingforceanditsspeedisoftenre

2、presentedbythepeculiarcurveofamachine.Fig.12-1ashowsapeculiarcurveofaninternalcombustionengine,andFig.12-1bshowsapeculiarcurveofanACelectromotor.12.1OperatingAnalysisofMachineryFig.12-1　Mechanicalbehaviorcurveofprimemachines(原动机的机械特性曲线图)2.OperatingProcessofMachines(1)S

3、tartupperiodTherunningspeedofamachineisfromzerotoworkrunningspeedinthisperiod,andtheworkdonebythedrivingforceisgreaterthantheworkdonebytheresistance.(2)SteadyrunningperiodInthesteadyrunningperiod,theworkdonebythedrivingforceisequaltotheworkdonebytheresistanceinaperiod.

4、Theincrementofthekineticenergyiszero.(3)StoppingperiodInthestoppingperiod,thedrivingforcewillceasetowork,thusWd=0.Themotioncontinuesforacertaintimeowingtotheinertiakineticenergyofthemachine.Fig.12-2　Crankpunch(曲柄压力机)Fig.12-3　Operatingprocessofmachinery(机械的运转过程)12.2Equi

5、valentKineticModelofMechanismSystems1.TheMethodofResearchingRunningProcessofMachinesFig.12-4　Forceanalysisofacrankpunch(曲柄压力机的受力分析)InordertofindtheactualmotionofamechanismshowninFig.12-4,wemustsolvethedrivingtorqueactingonthelink1andtheangularvelocity.Thedynamicforceana

6、lysisoftheslidercrankmechanismhasalargenumberofunknownstosolve.Weoftenselecttherotatinglinkorreciprocatinglinkasanequivalentlink.Fig.12-5showsthoseequivalentlinks.Fig.12-5　Equivalentlinks(等效构件)(1)RotatingequivalentlinkWhentheequivalentlinkisrotatingaboutanaxiswithacons

7、tantangularvelocity,thekineticenergyisasfollows：2.TheParameterofTheEquivalentLinkIftheequivalentlinkperformsarotatingmotion,theinstantpowerisasfollows:Theinstantpowergeneratedbytheequivalentlinkisequaltotheonesgeneratedbythewholemachine,sowehave：(2)Reciprocatingequival

8、entlinkAllthedrivingforcesormomentsactingonthemachinearereplacedbyoneforceormomentappliedtotheequivalentlink,t