Since the olden times, man has been trying to find some convenient ways of lifting water to higher levels for water supply or irrigation purposes. It is believe that the idea of lifting water, by centrifugal force, was first given by L.D Vinci (An Italian scientist and engineer) in the end of 16th century. Then this idea was put to experiments by French scientist and they designed centrifugal pump, having impeller and blades. At that time, the reciprocating pumps were very popular. Then a continuous advancement of this pump has brought it to high degree of perfection, which is used all over the world these days.
Types of Pumps
Though there are many types of pumps these days, yet the following two are important the subject point of view:
1. Centrifugal pump, and
2. Reciprocating pump.
A pump, in general, may be defined as a machine, when driven from some external source, lifts water or some other liquid from a lower level to a higher level. Or in other words, a pump may also be defined as a machine, which converts mechanical energy into pressure energy. The pump which raises water or a liquid from a lower level to a higher level by the action of centrifugal force is known as a centrifugal pump.
It will be interesting to know that the action of a centrifugal pump is that of a reserved reaction turbine. In a reaction turbine, the water at high pressure is allowed to enter the casing which gives mechanical energy at its shaft; whereas in a pump, the mechanical energy is fed into the shaft and water enters the impeller (attached to the rotating shaft) which increases the pressure energy of the outgoing fluid. The water enters the impeller radically and leaves the vanes axially.
Casings for the Impeller of a Centrifugal Pump
A centrifugal pump consists of an impeller, similar to that of a turbine, to which curved vanes are fitted. The impeller is enclosed in a water tight casing, having a delivery pipe in one of its sides. The casing for a centrifugal pump is so designed pump is so designed that kinetic a delivery pipe in one of its sides. The casing for a centrifugal pump is so designed that the kinetic energy of the water is converted into pressure energy before the water leaves the casing. This considerably increases the efficiency of the pump.