Impeller

Strictly speaking, propellers are a sub-class of impellers where the flow both enters and leaves axially, but in many contexts the term "impeller" is reserved for non-propeller rotors where the flow enters axially and leaves radially, especially when creating suction in a pump or compressor.

[2][3] The velocity achieved by the impeller transfers into pressure when the outward movement of the fluid is confined by the pump casing.

[4] In pumps, the fluid enters the impeller's eye, where vanes add energy and direct it to the nozzle discharge.

Wear on the bowl and edge of vane can be compensated by adjusting the clearance to maintain efficiency over time.

The construction of closed impellers includes additional back and front walls on both sides of vanes that enhances its strength.

[6] The screw impeller design aligns more with an axial progressive channel that allows for solids to be openly handled when rotating.

There are two types of impellers, depending on the flow regime created (see figure): Radial flow impellers impose essentially shear stress to the fluid, and are used, for example, to mix immiscible liquids or in general when there is a deformable interface to break.

Fire services in the United Kingdom and many countries of the Commonwealth use a stylized depiction of an impeller as a rank badge.

Officers wear one or more on their epaulettes or the collar of their firefighting uniform as an equivalent to the "pips" worn by the army and police.

Applications include blast furnaces, ventilation systems, and superchargers for internal combustion engines.

Impellers are an integral part of axial-flow pumps, used in ventricular assist devices to augment or fully replace cardiac function.