A radial turbine
is similar to an axial turbine
, except that instead of several successively smaller fan blades, it only has one. Radial turbines are lighter and more efficient at moving smaller amounts of air than axial turbines.
A radial turbine operates on centrifugal force, hurling air against the sides of its housing. The fan blades are angled so as to scoop the incoming air and better force it in. Radial turbines are most commonly used in small turbojet engines and automotive turbos.
If a radial turbine is part of a closed system, as with a turbo, it usually needs little or zero help getting started, although oil is usually pumped in to lubricate the bearings and assist with rotation. If it is not part of a closed system, as with a jet engine, it may require a starter bullet.
As with axial turbines, radial turbines can be designed to work either way - they can either be driven by external force and used to compress a fluid, or be used to convert the kinetic energy of a compressed fluid into rotation to drive a shaft. In a turbojet engine, the turbine that compresses the air coming into the engine is driven by a common shaft shared with another turbine on the other side of the engine which is driven by exhaust from the combustion chamber.