A turbine is a machine used to convert energy generated by a moving liquid, gas or air into work. For example, the energy produced by fast flowing water is made to spin a rotating shaft by pushing on the angled blades set around a wheel mounted on the shaft, and this action produces the required work. The generated work helps to drive machines like propeller of a ship or an aeroplane or electric generators to produce electricity. The gas or liquid used in a turbine is known as the working medium. The working medium can be water, steam, gas or air.
The water turbines use water from a waterfall or a dam to drive the turbine. There are two different methods to make the turbine wheels rotate. A water jet may be directed onto the blades. This is called a reaction turbine. In the second method, the turbine wheels are submerged in the flowing water. These turbines are used at hydro electric power stations.
For a steam turbine to operate, first the steam must to be produced by heating water in boilers. The steam enters the turbine at a high pressure. Inside the turbine, the pressure drops and the steam expands. This expansion drives the wheels around. Steam turbines have a series of wheels, mounted on the same shaft. This is because the steam expands gradually as it moves through the turbine.
Gas turbines are turned by fast-moving jets of gas. These gases are produced by burning liquid fuels or natural gases. Air is drawn into the front of the turbine, and passed through a compressor. The compressed air is mixed with the fuel and the mixture is ignited in the combustion chamber. This produces hot, expanding gases, which drive the turbine wheels. Gas turbines are used to turn the propellers of aircrafts and also to propel ships.
Gas turbines are used in jet engines. The hot gases are sent out at a high speed from the back of the engine. This produces a large amount of thrust that forces the engine to move forward. In jet engines, the purpose of the turbine is to drive the compressor. Turbines are also used in nuclear power stations.