Unit-18-Fluid-and-Hydraulic-System-机电专业英语-图文课件.ppt
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- Unit 18 Fluid and Hydraulic System 机电 专业 英语 图文 课件
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1、Unit 18 Fluid and Hydraulic SystemContentslNew Words&Expressions lText&TranslationlComplex Sentence AnalysislKey to ExercisesNew Words&Expressions lhydraulic system 液压系统lprehistoric pri:histrik adj.史前的,很久以前的lharness h:nis v.利用(风等)作动力,治理,控制lwatermill w:tmil n.水车,水磨lhydraulic motor 液压电动机lmosaic mzeiik
2、 n.镶嵌细工,马赛克ldomestication dmestikein n.家养,驯养ldisplacement displeismnt n.位移,转移,置换New Words&Expressions llayer lei n.层,层次ltangential tndenl adj.切线的,切向的lNewtonian njutnin adj.牛顿的,牛顿学说的lnonlinear nnlini adj.非线性的,非直线的lrotational ruteinl adj.旋转的,转动的,循环的lcompressible kmpresibl adj.可压缩的,可压榨的lPascals law 帕斯卡
3、定律lpressurize preraiz v.增压,给加压New Words&Expressions lintake inteik n.入口,进口,进入量ltank tk n.油箱,水箱,池塘l.reservoir rezvw:n.蓄水池,水箱,蓄能器latmospheric tmsferik adj.大气的,空气的ldischarge dist:d n.卸货,出料,流出;vi.卸下,放出lpreference prefrns n.优先选择lcompact kmpkt adj.紧凑的,紧密的,简洁的New Words&Expressions ldiagrammatic daigrmtik a
4、dj.图表的,概略的loil pressure pump 液压泵lhydraulic cylinder 液压缸lkinetic energy 动能lhydrostatic driver 静压传动lvariable-delivery pump 变量泵lby no means 决不lself-contained adj.独立的,配套的,整体的New Words&Expressions lstimulate stimjuleit v.促进,激励lhydraulics haidr:liks n.水力学,液压系统lresilience rizilins n.跳回,恢复力,回弹lvirtue v:tu:n
5、.优点,效力,功能ldetriment detrimnt n.损害,不利lregrind ri:graind v.重磨Text&TranslationlHydraulic power has a long history,which dates from mans prehistoric efforts to harness the energy in the world around him.The only sources readily available were the water and the windtwo free and moving streams.lThe waterm
6、ill,the first hydraulic motor,was an early invention.One is pictured on a mosaic at the Great Palace in Byzantium,dating from the early fifth century.The Romans had built the mill.But the first record of a watermill dates back even further,to around 100 BC,and the origins may indeed have been much e
7、arlier.Text&TranslationlThe domestication of grain began some 5 000 years before and some enterprising farmers may have become tired of pounding or grinding the grain by hand.Perhaps,in fact,the inventors were some farmers wives.Since they often drew the heavy jobs.lFluid is a flowing substance;that
8、 is,its constituent particles may continuously change their positions relative to one another.Moreover,it offers no lasting resistance to the displacement,however great,of one layer over another.This means that,if the fluid is at rest,no shear force(that is a force tangential to the surface on which
9、 it acts)can exist in it.Text&TranslationlFluid may be classified as Newtonian and non-Newtonian.1In Newtonian fluid there is a linear relation between the magnitude of applied shear stresses and the resulting rate of angular deformation.In non-Newtonian fluid there is a nonlinear relation between t
10、he magnitude of applied shear stress and the rate of angular deformation.lThe flow of fluids may be classified in many ways,such as steady or non-steady,rotational or irrotational,compressible or incompressible,and viscous or no viscous.Text&Translationl2All hydraulic systems depend on Pascals law,n
11、amed after Braise Pascal,who discovered the law.This law states that pressurized fluid within a closed containersuch as cylinder or pipeexerts equal force on all of the surfaces of the container.lIn actual hydraulic systems,Pascals law defines the basis of the results which are obtained from the sys
12、tem.Thus,the liquid is moved by a pump in the system.The intake of the pump is connected to a liquid source,usually called the tank or reservoir.Atmospheric pressure,pressing on the liquid in the reservoir,forces the liquid into the pump.When the pump operates,it forces liquid from the tank into the
13、 discharge pipe at a proper pressure.Text&TranslationlThe flow of the pressurized liquid discharged by the pump is controlled by valves.Three control functions are used in most hydraulic systems:control of the liquid pressure,control of the liquid flow rate,and control of the direction of flow of th
14、e liquid.lHydraulic drives are used in preference to mechanical systems when power is to be transmitted between point too far apart for chains or belts;high torque at low speed is required;a very compact unit is needed;a smooth transmission,free of vibration,is required;easy control of speed and dir
15、ection is necessary;and output speed is varied steplessly.Text&TranslationlFig.18.1 gives a diagrammatic presentation of the components of a hydraulic installation.3Electrically driven oil pressure pumps establish an oil flow for energy transmission,which is fed to hydraulic motors or hydraulic cyli
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