Impeller

An impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid.

Impellers in Pumps

An impeller is a rotating component of a pump , usually made of iron, steel, aluminum or plastic, which transfers energy from the motor that drives the pump to the fluid being pumped by forcing the fluid outwards from the centre of rotation. Impellers are usually short cylinders with protrusions forming paddles to push the fluid and a splined center to accept a driveshaft.


Impellers in Water Jets

Some impellers are similar to small propellers but without the large blades. Among other uses, they are used in water jet to power high speed boats.

Since impellers have no large blades to turn, they can spin at much higher speeds than propellers. The water forced through the impeller is channelled by the housing, creating a water jet that propels the vessel forward. The housing is normally tapered into a nozzle to increase the speed of the water, which also creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, so tending to increase the speed.

To work efficiently, there must be a close fit between the impeller and the housing. The housing is normally fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller.

Vessels using impellers are normally steered by changing the direction of the water jet.

Compare to propeller and jet aircraft engines.