A machine in which a fluid is used to produce rotational motion. The most widely used turbines are the steam turbines and water turbines that provide some 95% of the world's electric power (in the form of turbogenerators) and the gas turbines that power all the world's jet-propelled aircraft. In the impulse turbine a high-pressure low-velocity fluid is expanded through stationary nozzles, producing low-pressure high-velocity jets, which are directed onto the blades of a rotor. The rotor blades reduce the speed of the jets and thus convert some of the fluid's kinetic energy into rotational kinetic energy of the rotor shaft. In the reaction turbine the discharge nozzles are themselves attached to the rotor. The acceleration of the fluid leaving the nozzles produces a force of reaction on the pipes, causing the rotor to move in the opposite direction to that of the fluid. (See illustrations.) Many turbines work on a combination of the impulse and reaction principles.
Principle of the turbine