单项选择题
A.kg B.MPa C.mH20 D.None of the above
Which of the following are components of a mechanical s...
Which of the following are components of a mechanical seal? （） (1) stationary ring (2) rotational ring (3) packing (4)spring
A.(1), (2) and (3) B.(1), (2) and (4) C.(2), (3) and (4) D.None of the above
The gear, screw, and vane pumps are all classified as （...
单项选择题The gear, screw, and vane pumps are all classified as （）.
A.variable stroke pumps B.multistage pumps C.positive displacement pumps D.triple-ported pumps
The （） discharge a nearly constant amount of liquid reg...
单项选择题The （） discharge a nearly constant amount of liquid regardless of pressure.
A.mixed-flow pump B.axial-flow pump C.centrifugal pump D.displacement pump
