Lesson 3.2 Pumps

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Expressions and Technical Terms2

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Words泵

pump[pʌmp] n . 泵 blowcase [blәu`keis] n . 吹气箱elevation [͵eli`veiʃən] n . （ 1 ）断面图（ 2 ）海拔；标高member [`membә] n . 结构单元；成员；构件；节；环中原子数chamber [`ʧeimbә] n . 室；箱；容器

其他

inlet [`inlet] n . 入口，进口；投料口；供料口discharge [dis`ʧaʤ] n. 排放量；排放；排量 v 放电diameter [dai`æmitə] n. 直径flexible [`fleksəbl] adj 柔软的，灵活的rod [rɔd] n . 棒diaphragm [`daiəfræm] n . 隔膜；膜片

Expressions and Technical Terms

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对应职业岗位

mechanical energy 机械能positive-displacement pumps 容积泵；排代泵centrifugal pumps 离心泵reciprocating piston 往复式活塞rotational velocity 旋转速度kinetic energy 动能pressure energy 压力能displacement pump 位移泵reciprocating pump 往复泵rotary pump 回转泵；转子泵

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Liquid are sometimes moved by gravity from elevated tanks, or from a “ blowcase” (a storage vessel pressurized from an external source of compressed gas ), but by far the most common devices for the purpose are pumps.液体有时候可以由高位槽在重力的作用下被输送 , 或者可以通过压缩气箱来输送 .( 压缩气箱是由外界压缩气体加压后的储存气箱 ) 但是目前用于液体输送的最常见的设备是泵 .

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Pumps increase the mechanical energy of the liquid, increasing its velocity, pressure, or elevation –or all three. The two major classes are positive-displacement pumps and centrifugal pumps.泵可以增加液体的机械能 , 机械能可使液体的速度 , 压力 ,高度增加或这三个性质 . 泵有两种主要的形式 . 即容积泵和离心泵 .

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Positive-displacement units apply pressure directly to the liquid by a reciprocating piston, or by rotating members which from chambers alternately filled by and emptied of the liquid. Centrifugal pumps generate high rotational velocities, then convert the resulting kinetic energy of the liquid to pressure energy.容积泵可通过往复式活塞直接给液体加压或通过旋转构件给液体加压 , 旋转构件可使容积室内的液体交替的充满和排空 . 离心泵能使液体产生很高的旋转速度 , 然后把此速度所带来的动能转化为静压能 .

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Positive-Displacement Pumps There are two subclasses of positive-displacement pumps, reciprocating pumps and rotary pumps. In reciprocating pumps, the chamber is a stationary cylinder that contains a plunger or piston; in rotary pumps, the chamber moves from inlet to discharge and back to the inlet容积泵 有两种形式的容积泵 , 即往复泵和回转泵 . 在往复泵中容积是固定的 , 里面有活塞或活柱 . 在回转泵中容积室是活动的可从入口移动到出口再返回到入口 .

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Reciprocating pumps Piston pumps, plunger pumps, and diaphragm pumps are examples of reciprocating pumps. In a piston pumps, liquid is drawn through an inlet check valve into the cylinder by the withdrawal of a piston, and then is forced out through a discharge check valve on the return stroke. Most piston pumps are double –acting with liquid admitted alternately . 往复泵 活塞泵 , 活柱泵 , 隔膜泵都是往复泵 , 在活塞泵中通过活塞的抽取将使液体从单向阀入口阀抽到气缸中 , 然后在回程中经过出口阀使液体强制排出 . 大多数的活塞泵都是两个同时交换使用 .

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For higher pressures, plunger pumps are used. A heavy-walled cylinder of small diameter contains a close-fitting reciprocating plunger, which is merely an extension of the piston rod. At the limit of its stroke the plunger fills nearly all the space in the cylinder. Plunger pumps are single-acting and usually are motor-driven.压力较高的情况下使用活柱泵 , 直径很小 , 气壁很厚的缸包含有一个安装紧密的往复式活柱 , 它仅仅是活塞柱的一种延伸形式 . 在活塞泵柱冲程中 , 活塞几乎充满容积室的整个空间 . 活柱泵单独使用通常是需要马达驱动的 .

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In a diaphragm pump, the reciprocating member is a flexible diaphragm of metal, plastic, or rubber. This eliminates the need for packing or seals exposed to the liquid being pumps, a great advantage when handling toxic or corrosive liquids. A typical unit is shown in Fig. 9. 在隔膜泵中往复式的构件是一种灵活的金属 , 塑料 , 橡胶的膜片 . 这种膜片可以减少液体填充泵或密封泵的需要 ,这样就会使这种泵在处理有毒的 , 有腐蚀性液体时有很大好处 , 典型的隔膜泵如图 9

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Fig 9 Diaphragm Pump

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Rotary Pumps A wide variety of rotary positive-displacement pumps are available. They bear such names as gear pumps, lobe pumps ， screw pumps. Two examples of gear pumps are shown in Fig. 10.回转泵 有大量的回转容积泵可用 , 这些泵主要有齿 , 轮泵 , 凸轮泵 , 螺杆泵 . 两种齿轮泵如图 10

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Fig 10 Gear pumps (a)spur-gear pump ; 　　　　　 (b) internal-gear pump

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Unlike reciprocating pumps, rotary pumps contain no check valves. Close tolerances between the moving and stationary parts minimize leakage from the discharge space back to the suction space; they also limit the operating speed. Rotary pumps operate best on clean, moderately viscous fluids, such as light lubricating oil. Discharge pressures up to 200 atm or more can be attained.与往复泵不同 , 回转泵无单向阀 , 在移动的构件与固定之间的公差很小 , 减少了从出口空间到入口空间的漏矢量 ,同时也限制了操作速度 , 回转泵最好适宜输送 , 洁净的黏度适中流体 , 如轻质润滑油 , 出口压力达到 20.265Mpa 或更多 .

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Centrifugal Pumps In the second major class of pumps, the mechanical energy of the liquid is increased by centrifugal action. A simple, very common, example of a centrifugal pump is shown in Fig 11离心泵 在第二种泵即离心泵中 , 液体的机械能可通过离心泵的离心率可以提高 , 一种简单的常用的离心泵如图 11 所示 .

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Fig 11Single-suction centrifugal pump

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The liquid enters through a suction connection concentric with the axis of a high-speed rotary element called the impeller, which carries radial vanes integrally cast in it液体通过与高速旋转的构件即叶轮同轴的进口连接件进入到离心泵内 . 叶轮可夹带静像的叶片一起旋转

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Liquid flows outward in the spaces between the vans and leaves the impeller. In a properly functioning pump, the space between the vanes is completely filled with liquid flowing without cavitation. The liquid leaving the outer periphery of the impeller is collected in a spiral casing called the volute and leaves the pump through a tangential discharge connection.液体流到介于叶片和叶轮空隙中 , 在正常工作的离心泵中 , 叶片间的空间完全被液体所充满 , 无气蚀现象发生 .离开叶轮外周的液体 , 被收集到叫做蜗壳的旋转构件中 ,通过切向的出口连接件排出泵外 .

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作业

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