Turbo-prop.

turbo-prop. (komb. off: Turbine and. Propeller) is a landläufige name for propeller turbine engine (also as PTL designates). Airplanes with this engine are limited to airspeeds up to approximately 80 per cent of the speed of sound. In this speed range Turboprops work also more economically than pure turbine engines.

Funktionsschema eines Turboproptriebwerkes (A Propeller, B Getriebe, C Kompressor, D Brennkammer, E Turbine, F Ausstoßdüse)
Operation diagramme oneTurbo-prop (A propeller, B transmission, C compressor, D combustion chamber, E turbine, F output nozzle)
Triebwerke einer Bristol, Britannia, eines der ersten Turboprop-Flugzeuge
engines of a Bristol, Britannia, one of the first turboprop aircraft
propellers moving in opposite directions to Antonov a An-70, one the different sheet number

the turbo-prop. considers is a gas turbine, those as wave engine a propeller over a transmission propels. The thrust is produced almost exclusively by the propeller, to which the produced energy of the turbine will transfer. In order to produce the thrust, by the propeller very large amounts of air are sucked in and accelerated weakly. This kind of the engine draws by low fuel consumptionout, why it primarily with transportation and Kurzstreckenflugzeugen, which operate in the lower air space (until 20,000 ft/6.500 m), is used. In higher air layers the air pressure is so low that turboprop aircraft are unprofitable and therefore turbofan - airplanes to the employment come.

Differently than with otherwise usual propellers become Propellers uses, which possess frequently five or more shovel sheets. Thus the shovel length can be shortened with same air volume. By the lower speed at the blade tips one achieves a low noise level. In addition one knows only so the Stromgeschwindigkeiten at the blade tips under the range of the speed of soundhold and the associated enormous friction forces minimize.

Depending upon airspeed and flight altitude the angle of incidence of the propeller blades is usually stopped automatically, in order to achieve an optimal utilization of the torque and the number of revolutions.

The energy for the drive of the propeller supplies the gas turbine. It sucksAir, which is consolidated in an axial or radial multi-level compressor. Subsequently, it arrives into the combustion chamber, where it burns with the fuel and expands much. Air high-energy flows by usually the axially developed and multi-level turbine and thereby is eased.The energy transferred to the turbine propels the compressor if necessary over a wave and over a transmission the propeller. The exhaust gases are discharged.

In relation to a conventional drive over piston motors propeller type turbines have the advantage of a smaller weight with same achievement (about 0.23 to 0.27 kg/kW),a smaller front surface and a higher maximum power per engine.

The largest airplane with this engine type is those Antonov An-22, whose Kuznetsov NK-12MA - engines with an achievement each the largest Turboprops per built by 11,185 KW are simultaneous.

See also: Engine, jet engine

 

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