A positive displacement pump is one in which a definite volume of liquid is delivered for each cycle of pump operation.
An air vessel is a cast iron closed chamber having an opening at its base through which the water flows into the vessel or from the vessel.
The purpose of using the air vessel to obtain unifrom discharge from the reciprocating pump.
Self primed due to their capacity to remove air from the suciton line.
These pumps are used for systems require high suction lift.
These are positive displacement and have constant discharge.
Vane Type Pump
A centrifugal pump has external and internal impeller diameters as 600 mm and 300 mm respectively. The vane angle at inlet and outlet are 30° and 45°respectively. The water enters the impeller at 2.5 m/s, the velocity of flow is constant through the impeller is constant. Find
Speed of impeller in r.p.m.
Work done per KN of water
Calculate vane angle at the inlet of a centrifugal pump impeller having 200 mm diameteer at inlet and 400 mm diameter at outlet. The impeller vanes are set back at angle of 45° to the outer rim, and the entry of the pump is radial. The pump runs at 1000 r.p.m and velocity of flow through the impeller is constant at 3 m/s. Also calculate the work done per kN of water and the velocity as well as direction of the water at outlet.