《外文翻译--液压系统和气压系统.doc》由会员分享，可在线阅读，更多相关《外文翻译--液压系统和气压系统.doc（10页珍藏版）》请在金锄头文库上搜索。
1、Hydraulic system and Peumatic SystemHui-xiong wan,Jun Fan1. School of mechanical science and Engineening,Huazhong univ.of science and technology,Wuhan,430074,China2. School of Logistics Engineening,Wuhan,univ.of science and technology,Wuhan,430063,ChinaAbstract:Hydraulic system is widely used in ind
2、ustry, such as stamping, grinding of steel type work and general processing industries, agriculture, mining, space technology, deep sea exploration, transportation, marine technology, offshore gas and oil exploration industries, in short, Few people in their daily lives do not get certain benefits f
3、rom the hydraulic technology. Successful and widely used in the hydraulic systems secret lies in its versatility and ease of maneuverability. Hydraulic power transmission mechanical systems as being not like the machine geometry constraints, In addition, the hydraulic system does not like the electr
4、ical system, as constrained by the physical properties of materials, it passed almost no amount of power constraints.Keywords: Hydraulic system, Pressure system, FluidThe history of hydraulic power is a long one, dating from mans prehistoric efforts to harness the energy in the world around him. The
5、 only source readily available were the water and the windtwo free and moving streams.The watermill, the first hydraulic motor, was an early invention. One is pictured on a mosatic at the Great Palace in Byzantium, dating from the early fifth century. The mill had been built by the Romans. But the f
6、irst record of a watermill goes back even further, to around 100BC, and the origins may indeed have been much earlier. The domestication of grain began some 5000 years before and some enterprising farmer is bound to have become tired of pounding or grinding the grain by hand. Perhaps, in fact, the i
7、nventor were some farmers wives. Since the often drew the heavy jobs.Fluid is a substance which may flow; that 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 ove
8、r another. This means that, if the fluid is at rest, no shear force (that is a force tangential to the surface on which it acts) can exist in it.Fluid may be classified as Newtonian or non-Newtonian. In Newtonian fluid there is a linear relation between the magnitude of applied shear stresses and th
9、e resulting rate of angular deformation. In nonNewtonian fluid there is a nonlinear relation between the magnitude of applied shear stress and the rate of angular deformation.The flow of fluids may be classified in many ways, such as steady or non steady, rotational or irrotational, compressible or
10、incompressible, and viscous or no viscous.All hydraulic systems depend on Pascals law, such as steady or pipeexerts equal force on all of the surfaces of the container.In actual hydraulic systems, Pascals law defines the basis of results which are obtained from the system. Thus, a pump moves the liq
11、uid 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 discharge pipe at a suitabl
12、e pressure.The flow of the pressurized liquid discharged by the pump is controlled by valves. Three control functions are used in most hydraulic systems: (1) control of the liquid pressure, （2）control of the liquid flow rate, and (3) control of the direction of flow of the liquid.Hydraulic drives ar
13、e used in preference to mechanical systems when(1) powers is to be transmitted between point too far apart for chains or belts; (2) high torque at low speed in required; (3) a very compact unit is needed; (4) a smooth transmission, free of vibration, is required;(5) easy control of speed and directi
14、on is necessary; and (6) output speed is varied steplessly.Fig. 1 gives a diagrammatic presentation of the components of a hydraulic installation. Electrically driven oil pressure pumps establish an oil flow for energy transmission, which is fed to hydraulic motors or hydraulic cylinders, converting
15、 it into mechanical energy. The control of the oil flow is by means of valves. The pressurized oil flow produces linear or rotary mechanical motion. The kinetic energy of the oil flow is comparatively low, and therefore the term hydrostatic driver is sometimes used. There is little constructional di
16、fference between hydraulic motors and pumps. Any pump may be used as a motor. The quantity of oil flowing at any given time may be varied by means of regulating valves( as shown in Fig.7.1) or the use of variable-delivery pumps.The application of hydraulic power to the operation of machine tools is by no means new, though its adoption on such a wide scale as exists at present is comparatively recent. It was in fact in development of the modern self-conta
