Aircraft Gas Turbine

one of the basic subsystems of an aircraft gas turbine engine. Aircraft gas turbines differ from stationary-plant gas turbines by their greater output combined with smaller size and smaller mass, which is achieved through design improvements, the high axial-flow velocities of the gas through the turbine, the high rim speeds of the turbine under operating conditions (up to 450 m/sec), and the extensive heat differential (to 250 kilojoules per kg, or 60 kilocalories per kg). Aircraft gas turbines are capable of developing high power levels; for instance, the single-stage turbine in a modern engine develops a power output as high as 55 megawatts (MW), or 75,000 horsepower (hp). The most popular aircraft gas turbines are of the multistage type, in which the power developed by a single stage is usually 30–40 MW (40,000–50,000 hp). Aircraft gas turbines are characterized by a high gas temperature (850–1200°C) at the turbine inlet. The required lifetime and reliable operation of the turbine are secured through the use of special alloys characterized by excellent mechanical properties at their working temperature and resistance to creep, and also by cooling the nozzle blading and rotor blading, the turbine casing, and the rotor disks. Air cooling in which air from a compressor is passed through the channels of the cooling system to enter the turbine blading system is in wide use.

Aircraft gas turbines are used to drive the compressor of a turbojet engine, the compressor and fan of a double-flow turbojet engine., and the compressor and propeller of a turboprop engine. Aircraft gas turbines are also used to drive auxiliary equipment of engines and aircraft, such as starters, electrical generators, fuel pumps, and oxygen pumps in liquid-fuel rocket engines.

The development of the aircraft gas turbine follows the path of aerodynamic design and technological improvements—improving the gas-dynamic characteristics of the blading flow path to achieve higher efficiency over a wider range of variations in operating conditions characteristic of the aircraft engine; reducing the turbine mass (while maintaining the specified power level); achieving further increases in the gas temperature at the turbine inlet; using the latest highly refractory materials and coatings; and promoting effective cooling of the turbine blades and disks. The development of the aircraft gas turbine has also progressed by further increases in the number of stages—as many as eight in modern aircraft gas turbines.