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# Lecture 5

## on Feb 21, 2012

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## Lecture 5Presentation Transcript

• Lecture 5 Fluid Mechanics II Muhammad Usman
• Reciprocating Pumps
• Suitable for less discharge and higher heads.
• A positive displacement pump is one in which a definite volume of liquid is delivered for each cycle of pump operation.
• Air Vessels
• 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.
• Rotary Pumps
• 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.
• Gear Pump
• Lobe Pump
• Screw Pump
• Vane Type Pump
• Diaphragm Pump
• Example 1
• 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
• Example 2
• 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.