Centrifugal pumps are hydraulically operated machines characterised by their ability to transmit energy to fluids through the work of a field of centrifugal forces. Their main purpose is to transfer fluids through an increase in pressure and are the most commonly used pumps in all industries. Centrifugal pumps can have different structures, but their operating principle and fluid dynamic characteristics are always the same.
Schematically, centrifugal pumps consist of an impeller/s that rotates inside a casing. The impeller comprises a series of blades, preferably of a radial design, which transmit kinetic energy to the fluid being pumped. The casing is equipped with suction and discharge nozzles for the fluid being pumped. The suction nozzle has an axis that corresponds with the impeller’s rotational axis, while the discharge nozzle has a normal axis to the impeller axis, but still lying on the plane passing through the axis itself.
Mechanical to Kinetic Energy
The fluid being pumped enters continuously through the pump’s suction nozzle at the centre of the impeller. From here, fluid is accelerated in a radial direction as far as the edge of the impeller, where it drains into the casing.
The rotation of the pump impeller imparts kinetic energy to the fluid as it is drawn in from the impeller eye and is forced outward through the impeller vanes to their periphery. As the fluid exits the impeller, the fluid kinetic energy is then converted to static pressure.
Typically, the volute shape of the pump casing or the diffuser vanes, which serve to slow the fluid, are responsible for the energy conversion. The energy conversion results in an increased pressure on the downstream side of the pump, causing flow.
