The Gas Turbine Engine: Basic Operation
The gas turbine engine provides thrust for aircraft through a series of stages similar to any internal combustion engine. The gas turbine engine functions similarly to the four-cycle piston automotive engine. The gas turbine consists of four main components: the compressor, combustion chamber, turbine, and exhaust nozzle. To operate, an engine must (1) draw in a quantity of air and compress it, (2) burn it with fuel and extract the energy, (3) turn the blades of the turbine, and then (4) exhaust the discharge gases producing thrust.
Air Intake and Compression
Air is drawn into the gas turbine engine and compressed by multiple sets of rapidly rotating fan blades driven by the engine turbine via a turbine shaft. This axial flow compressor employs alternate rows of rotating (rotor) blades, to accelerate the air, and stationary (stator) vanes, to diffuse the air, until the required pressure rise is obtained. The compressed air then enters the combustion chamber.
Combustion of Compressed Air and Fuel
The combustion chamber consists of a chamber containing fuel spray nozzles and an igniter. Fuel is mixed with the high volume of air, supplied by the compressor, and ignited. The resulting heat expands and accelerates to produce a smooth stream of uniformly heated gas. Compressed air is mixed with the heated air to cool the stream before hitting the turbine.
Production of Energy in the Turbine
Hot gases released from the combustion chamber pass through the turbine, spinning its blades. This rotational energy (torque) drives the compressor and other engine components. Turbine blades must survive intense heat. Cool air is forced out of many small holes in the blades. This air remains close to the blade surfaces, preventing them from melting.
After passing through the turbine blades, the air mix enters the engine exhaust nozzle. The exhaust nozzle passes the turbine-discharge gases to the atmosphere at high velocity. The nozzle guides the exhaust to provide the engine thrust while protecting nearby components from excessive heat. The nozzle can also contain a thrust reverser to slow the aircraft on landing and a noise suppressor to reduce noise.