单项选择题
A centrifugal impeller consists of a number of vanes curving （） from the direction of rotation.
A.backwards
B.forwards
C.upward
D.downwards
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相关考题
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单项选择题
When installed for bilge pumping or ballast duty, centrifugal pumps require a （） to remove air from the suction pipe.
A.air chamber
B.head lank
C.primer
D.prime mover -
单项选择题
Water enters the rotating impeller through the entry, known as “（）”, at the centre.
A.eye
B.hole
C.balance holes
D.opening -
单项选择题
Which one is not the normal operation for boiler shutdown?（）
A.Carry out soot blowing if permissible
B.Change fuel supply to diesel oil
C.Close steam stop valves on boiler when pressure is reduced
D.Drain boiler empty when it has cooled down
