单项选择题
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
The discharge flow of a reciprocating pump is （）.A.stea...
单项选择题The discharge flow of a reciprocating pump is （）.
A.steady B.in pulsation C.continuous D.large
A centrifugal pump produces the required pressure energ...
单项选择题A centrifugal pump produces the required pressure energy by means of a rotating （） provided with vanes.
A.propeller B.impeller C.circumference D.screw
