单项选择题
A.throttling the pressure line B.changing the speed of the rotor C.either A or B D.None of the above is tree
A screw pump belongs to （） according to its working pri...
单项选择题A screw pump belongs to （） according to its working principle.
A.reciprocating pumps B.positive displacement pumps C.centrifugal pumps D.centripetal pumps
Through a （） pump, the liquid is transferred from the s...
单项选择题Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.
A.positive displacement B.ejector C.centrifugal D.air compressor
In a （） the center screw is driven and the outer screws...
单项选择题In a （） the center screw is driven and the outer screws idle.
A.single screw pump B.double-screw pump C.triple screw pump D.centripetal pump
