单项选择题
A.providing the impeller with balancing holes B.the use of symmetrical impeller C.neither A nor B D.either A or B
The amount of fluid delivered by a gear pump can be reg...
单项选择题The amount of fluid delivered by a gear 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 true
Which of the following pumps are self-priming, and can ...
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump（） (1) ejector (2) screw (3) centrifugal
A.(1)only B.(1)and(2) C.(1),(2)and(3) D.(2)and(3)
In （） pumps a closed discharge valve will cause burstin...
单项选择题In （） pumps a closed discharge valve will cause bursting discharge pressure.
A.centrifugal B.plunger C.injector D.water
