Lesson 3.2 Pumps. words. 1. Expressions and Technical Terms. 2. Text. 3. content. 泵. 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.
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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
displacement pump 位移泵
reciprocating pump 往复泵
rotary pump 回转泵；转子泵
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
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 .
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.
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