文档介绍：附录
外文文献原文:
monly used sources of power in hydraulic systems are pumps and accumulators .
Similarly,accumulator connected to atmosphere will dischange oil at atmosphere pressure until it empty. only when connected to a system having resistance to flow can pressure be developed.
Three types of pumps find use in fluid-power systems:rotary,reciprocating or piston-type, and 3,centrifugal pumps.
Simple hydraulic system may use but one type of pump . The trend is to use pumps with the most satisfactory characteristics for the specific tasks involved . In matching the characteristics of the pump to the requirements of the hydraulic system , it is not unusual to find two types of pumps in series . For example , a centrifugal pump may be to supercharge a reciprocating pump , or a rotary pump may be used to supply pressurized oil for the contronls associated with a reversing variabledisplacement pumps . Most power systems require positive displacement pumps . At high pressure , reciprocating pumps are often preferred to rotary pumps .
1、Rotary pumps
These are built in many differnt designs and extremely popular in modern fluid power system . The mon rotay-pump designs used today are spurgear , internal gear ,generated rotor , sliding vane ,and screew pumps . Ehch type has advantages that make it most suitable for a given application .
2、Gear pumps
Gear pumps are the simplest type