油压泵简介外文文献翻译、泵体类机械外文翻译、中英文翻译

- 0 - 本科生毕业设计  (论文 ) 外  文  翻  译   原  文  标  题  Oil pressure pump cover 译  文  标  题  油压泵简介  作者所在系 别  机械工程系  作者所在专业  机械设计制造及其自动化  作者所在班级  机本 1007 作  者  姓  名  龙张平  作  者  学  号  10201420739 指导教师姓名  范志明  指导教师职称  副教授  完  成   时  间   2014 年  5 月  20  - 1 - 译文标题  油压泵  原文标题  Oil pressure pump cover  作     者    译   名   国  籍   原文出处     原文   A hydraulic pump is a mechanical device which converts mechanical energy into hydraulic energy.More specifically ,a pump converts the kinetic(moving) energy of a rotating shaft into the kinetic energy of fluid flow. The fluid flow also has potential energy that allows it to overcome the resistance of the system to fluid flow .Remember that a pump provides the force produce flow and transmit power . Hydraulic pressure is caused by the load on the system and by the resistance of the hydraulic system to fluid flow. When operating , a hydraulic pump performs two functions. First, it creates a partial vacuum at its inlet ,permitting the atmospheric pressure in the fluid reservoir to push the hydraulic fluid through the inlet strainer and line into the pump .Second, its mechanical action delivers the fluid to its outlet and into the hydraulic systems, as shown in Fig.5-1. As the fluid leaves the pump, it encounters the working pressure in the system. This pressure is produced by the pressure regulating valve, the system work load ,and flow losses in the hydraulic tubing A pump is classified on the basis of the physical arrangement of its pumping mechanism and its basic principle of operating. Pumps classified by principle of operation include positive displacement and nonpositive-displacement types. Positive-displacement pumps are equipped with a mechanical separation(gears,vanes,or impellers) between the inlet and outlet, which minimizes internal leakage or slippage. Therefore,the output of positive-displacement pumps is almost unaffected by variations in system pressure Nopositive-displacement pumps(such as centrifugal pumps) do not have a positive internal separation against leakage or slippage. Because of this slippage,the delivery of these pump is reduced as the working pressure of a  - 2 - system is increased. However, nonpositive-displacement pumps deliver a continuous flow, while positive-displacement pumps deliver an intermittent(pulsating) flow. These pulsations are small and can be smooth out by the accumulator or the system piping. Most hydraulic pumps are positive-displacement pumps of the rotary type. Positive-displacement pumps have either a fixed or variable displacement. The volume of delivery ,or gpm, of a fixed-displacement  pump can be changed only by changing the speed of the pump, because the physical arrangement of the pumping mechanism cannot be changed, (This does not mean that the flow in other portions of the system cannot be adjusted by valves.) The flow of a variable-displacement pump can be changed by changing the physical arrangement of the pumping mechanism with a built-in controlling device. This device often functions in response to system pressure or other signals. Variable-displacement pumps are more complex than fixed-displacement pumps and,therefore,cost more. In addition, the efficiency of a variable-displacement pump is lower than that of a fixed-displacement pump. This is offset somewhat by the higher overall efficiency of a system powered by a variable-displacement pump. Most positive-displacement pumps are classified as rotary pumps. This is because the assembly that transfers the fluid from the pump inlet to the pump outlet has a rotating motion. Rotary pumps are further classified according to the mechanism that transfers the fluid-such as gears,vanes,or screws. A different kind of positive-displacement pump is piston pump. This pump uses a reciprocating (back-and-forth) motion of the piston, alternately to receive fluid on the inlet side, and to discharge fluid on the outlet side. A radial-piston pump has a revolving assembly with several piston assemblies built into it, and can be classified as a rotary pump. Several types of piston pumps will be discussed later in this chapter. The performance of different pumps is evaluated on the basis of many factors, inculding physical characteristics, operating characteristics,and cost. When selecting a pump, the follow pump rating and selection factors are considered； Capacity Pressure Energy consumption Drive speed Efficiency  - 3 - Reliability Fluid characteristics Size and weight Control adaptability Service life Installation and maintenance costs Some of the performance characteristics of different pumps are given in Table 5-1.Each of these selection factors is described briefly in the following paragraph. The primary rating of a pump is its capacity. This is also called the delivery rate ,flow rate, or volumetric output. The capacity usually is given in gallons per minute (gpm), cubic inches per minute( min/3in ) ,or cubic inches per revolution at specified operating conditions. Pump capacity ratings usually are given at standard atmospheric inlet pressure and various output pressures, as well as at approximate fluid service temperatures. The pressure rating of a pump generally is based on the ability of the pump to withstand pressure without an undesirable increase in its internal leakage( or slippage) or damage to pump parts. Pumps are pressure-rated under the same conditions( speed,temperrature,and inlet pressure) at which they are capacity-rated. Most pumps are pressure-rated at 100,500,1000,1500,2000,3500,or 5000 psi. Energy consumption is an important consideration not only in the selection of a pump, but also in the operating performance of the pump after the system is installed. The energy requirement for pumping depends on the pumping pressure, and on the mass of fluid pumped in a given time. The fluid pumping horsepower is determined as follow: Hp=(gpm* galb1*psi)/(14286*n) Where n is the overall effciency of the pump, motor, and drive. As you can see from this equation, reducing gpm and  psi results in a proportional reduction in pumping horsepower. Control of pump delivery can be accomplished either manually or automatically, using handwheel,levels, or variable-speed motors or transmission actuated by load-sensing controls. Pumps often are rated at the commonly available electric motor speed of 1200 or 1800 rpm.They also may be rated at speeds other than motor speeds. For instance, higher speeds occur in mobile hydraulic pumps driven from internal combustion engines. These engines usually operate at a constant speed  - 4 - and include speeds of 2000 rpm and higher. Some industrial hydraulic pumps are rated at speeds of up to 4000 rpm. The maximum safe speed for a rotating pump is limited by the pump s ability to avoid cavitation and high outlet pressures. Most rotating pumps also require a minimum operating speed. Although these speeds usually are not critical, pumps operating at high pressures require a minimum speed in order to prevent overheating or internal slippage. Maximum speed and pressure ratings for pumps often are given for both intermittent and continuous operation. Continuous ratings describe the maximum speed and pressure at which a pump can be operated for a normal design life (about 10000 hours). Intermittent ratings are maximum speed and pressure at which a pump can be operated safely for short times and still have a satisfactory service life. Operating a hydraulic pump beyond its drive speed ratings usually reduces its service life. As pointed out earlier, the pressure a system exerts on the hydraulic pump directly affects the delivery rate of the pump. As the pressure increases, the flow rate of the pump decreases. The amount of decrease varies depending on the type of pump used. This change in flow affects the pump s efficiency. Pump efficiency is described in two ways: Volumetric efficiency- the ratio of the actual delivery rate to the theoretical displacement Overall efficiency-the ratio of the hydraulic power output to the mechanical power input. The reliability of a pump is determined by how well the characteristics of the pump are matched to the requirements of the system. Reliability can also be measured in maintenance time. Items such a how much fluid is required, how well the system is designed and maintained, where the pump is located, and how durable it is, all are related to reliability. The service life of a pump is rated in hours of operation. Many hydraulic pumps hava a service life of 10000 hours, or about one year. Other operate for three or five years at about 5000 hours per year, for a total of 15000 or more hours. The service life depends on the design and construction of the pump as well as on the application.  - 5 - 翻译      液压 泵是 能把机械能转化为液压能的机械装置， 更具体地说 ,一个泵将旋转柱塞的动能转换为流动的液压能。这些流体也有潜在的能量能够克服系统阻力进行流动，记住 液压 泵提供了一个产生流量和输出功率的力。液压是由系统负载和液压系统阻力的流体流动。  当液压 泵工作时，它执行两个功能， 首先 ,它在其入口创建了一个局部真空， ,允许大气压力作用下推动液压油通过入口过滤器和油路进入泵的吸油腔。第二 ,它的机械作用传递液压油到出口并进入液 压系统，正如表 5-1所示。当液压油离开 泵时，它就会遭遇系统的工作压力，这种压力是由调压阀、系统的外负载和液流的管路损失所产生的。  液压 泵是基于他的物理排油机制和基本操作原理来分类的。泵按操作原理分配包括正排量泵和负排量泵。正排量泵在入口和出口之间装备了一个机械分离装置（齿轮、叶片或叶轮）来最大限度的减少内部泄漏和滑移。因此 ,正排量泵的输出是几乎不受系统压力变化的影响。  负排量泵没有一个确切的内部分离装置来减少泄漏和滑动，由于这种滑动，这些泵的排油量减少正如系统的工作压力增加。然而，负排量泵是持续性排油，正排 量泵是间歇（脉动）的排油，这些脉动很小，可以通过蓄能器和系统管路消除。大多数液压泵是回转型的正排量容积泵。     正排量泵分为定量泵和变量泵。定量泵的流量只能通过改变泵的转速来调节，因为泵的抽吸装置的物理机制是无法改变的。（这并不意味着液压系统的其他部分不可以通过阀门来调节。）      变量泵可以通过一个内置的控制装置来改变泵的抽吸装置的物理机制，这个控制装置通常是用来相应系统压力和其他信号。变量泵比定量泵更复杂，因此成本更高。此外变量泵的效率也比定量泵的效率要低。这些变量泵更低的效率有些时候抵消了部分更高 的系统整体效率。    大多数正排量泵被分类为旋转泵。这是因为液压油从入口被到出口有一个旋转的过程。旋转泵通过它的排油机制进一步划分为齿轮泵、叶片泵、螺杆泵。    柱塞泵是一种不同的正排量泵，这种泵是使用一种往复（来回）式运动的柱塞，交替的在吸油口吸油，出油口排油。一个旋转装置和数个活塞组构成了一个径向柱塞泵，因此它能被分类为旋转泵。 几种类型的柱塞泵将在本章后面讨论 。     不同泵的性能的评估是基于许多因素，包括物理特性、运行机制以及成本。当选者一个泵时，应考虑遵循泵的功率选择因素。     排量     压力   - 6 -   能耗     转速     效率     可靠性     流量     大小和重量     操作适应性     使用寿命     安装和维护成本     我们主要通过一个泵的容量来评价它。这也可以被称作供油速度、流量、容积输出。这种能力通常是在制定操作条件下每分钟多少加仑，多少立方英寸，或者一次循环输出多少立方英寸。泵能力的评级通常在标准大气进气压力和各种输出压力 ,以及在相似的流体使用温度下。       一个泵压力等级的一般是基于的泵能够承受的压力能力并且没有一个不良的内部泄漏 (或滑脱 )或泵零件损坏的增加。  泵 额定压力是在相同条件下（速度、温度、和入口压力）进行的的能力的评估。 大多数泵额定压力在 100， 500， 1000， 1500， 2000，3500或 5000磅每平方英寸。      能耗是一个重要的考虑因素，不仅仅是在泵的选择上，而且还是在系统安装完成后泵的操作性能上。这个能耗取决于泵压力，和给定时间内的泵的输送流量。  液压 泵马力确定如下 :          Hp=(gpm* galb1*psi)/(14286*n) 这里 n 是整体效率的泵、 马达、驱动器，正如您可以从这个方程看到，减少能耗 和流量将会成比例的减少泵的抽送