單項(xiàng)選擇題

Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? ()
(1) reciprocating
(2) rotary
(3) centrifugal

A.(1)only
B.(1)and (2)
C.(1),(2)and(3)
D.(2)and(3)


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1.單項(xiàng)選擇題The amount of fluid delivered by a positive displacement pump can be regulated by ().

A.throttling the pressure line
B.changing the speed of the driving rotor
C.either A or B
D.None of the above is tree

2.單項(xiàng)選擇題The amount of fluid delivered by a reciprocating pump can be regulated by ().

A.throttling the pressure line
B.changing the speed of the piston
C.either A or B
D.None of the above is tree

3.單項(xiàng)選擇題The amount of fluid delivered by a centrifugal pump can be regulated by ().

A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is tree

4.單項(xiàng)選擇題While flowing through the volute in a centrifugal pump, part of the () energy of the liquid is converted to () energy.

A.kinetic;pressure
B.kinetic;essential
C.pressure;kinetic
D.pressure;height

5.單項(xiàng)選擇題The amount of fluid delivered by a screw pump can be regulated by ().

A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is tree