Air vessel is a closed chamber containing compressed air in the top space and liquid at the bottom of the chamber. At the base of the chamber, there is an opening through which the liquid (water) may flow into or out from the vessel. When liquid enters the air vessel, air gets compressed and when liquid exits from the vessel, the air gets expanded. An air vessel is fitted to the suction pipe and to the delivery pipe at a point close to the cylinder of a single acting reciprocating pump as shown in Figure 9.24. The purposes of its application are as given below:
Figure 9.24 Reciprocating Pump with Air Vessels
- To obtain a continuous supply of liquid at uniform rate.
- To save a considerable amount of work in overcoming the friction resistance in the suction and delivery pipes.
- To run the pump at high speed without separation.
Work done by reciprocating pump with air vessels fitted to suction and delivery pipes
Work done by reciprocating pump with air vessels fitted to suction and delivery pipes
Example 9.16: A single acting reciprocating pump running at 100 rpm delivers 0.10 m3/s of water. The diameter of the piston is 500 mm and stroke length is 400 mm. Determine (i) the theoretical discharge, (ii) percentage slip, and (iii) co-efficient of discharge.
Solution:
Example 9.17: A double acting reciprocating pump has a piston of 300 mm diameter and piston rod of 60 mm diameter. Stroke length is 400 mm and speed is 50 rpm. The suction and discharge heads are 8 and 18 m, respectively. Determine (i) the force required to run the pump during in and out strokes, (ii) quantity of water in m3/s raised by pump, and (iii) power required to run the pump.
Solution:
Given: D = 300mm; d = 60mm; L = 400mm; N = 50rpm; Hs = 8m; and Hd = 18m
- Force required during in-stroke, F = ρg (A × Hs + (A − a) Hd)
- Force required during out-stroke = F = ρg [A × Hd + (A − a) Hs]
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