单项选择题
A.diameter of the discharge piping, with all other factors remaining the same
B.diameter of the suction piping, with all other factors remaining the same
C.width of the impeller only
D.diameter of the impeller
单项选择题 If the discharge valves on a refrigeration compressor are leaking badly, the compressor should （）.
单项选择题 Which of the following terms could be applied to the simple definition the energy of motion?（）
单项选择题 The delivery rate of an axial-piston hydraulic pump is controlled by varying the position of the （）.