单项选择题
Air chambers are usually fitted to reciprocating pumps in order to （）.
A.increase discharge pressure B.increase suction vacuum C.develop pulsation flow D.keep a steady rate of flow
单项选择题 Some pumps use packing as sealing glandThe gland should be （）.
单项选择题 Which of the following pumps is used where a relatively high pressure and small capacity are required?（）
单项选择题 The （） pump discharges a nearly constant amount of liquid regardless of pressure.
