單項(xiàng)選擇題

Centrifugal pumps are popular because they are very simple in construction,and produce smooth, constant, （） discharge.

A.non-pulsating
B.pulsating
C.positive
D.non-positive

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單項(xiàng)選擇題

The emergency bilge suction or bilge （） is used to prevent flooding of the ship.

A.injection valve
B.relief valve
C.discharge valve
D.inlet filter

單項(xiàng)選擇題

In （） pump a closed discharge valve will not cause excessive pressure to build up.

A.gear
B.vane
C.screw
D.centrifugal