Explain the working principle of a Centrifugal pump with a simple diagram.
When a certain mass of liquid is made to rotate by an external force, it is thrown away from the central axis of rotation and a centrifugal head is impressed which enables it to rise to a higher level. The centrifugal force is created by an impeller spinning at high speed inside a pump casing.
The centrifugal pump consists of a set of curved vanes sandwiched between 2 pairs of discs. The impeller has an opening (called the eye) at the centre along the axis of rotation. The fluid enters through the eye of the impeller. The fluid is then rotated by the curved vanes and flows radially outwards gaining kinetic energy. It then enters into a diffuser or volute casing. This kinetic energy of the fluid coming out of the impeller is harnessed by creating a resistance to the flow. The first resistance is created by the volute casing that catches the fluid and slows it down. The fluid further deaccelerates as it travels the involute path and its velocity is converted to pressure according to Bernoulli’s principle.
Therefore, the Head (Pressure in terms of height of the fluid) developed and equal to the velocity energy at the periphery of the impeller expressed by the well-known formula:
Where, H: total head developed in feet; v: velocity developed at the periphery of the impeller in ft/sec; g: acceleration due to gravity (32.2 ft/sec2).
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