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Turboprop Engine Concept

 Turboprop Engine Concept


  • The turboprop engine is a variant of a jet engine that has been optimized to drive a propeller. Turboprop equipped aircraft are very efficient at lower flight speeds (less than mach 0.6), burning less fuel per seat-mile and requiring significantly less runway for takeoff and landing than a turbojet or turbofan powered aircraft of the same size.
  • When the aircraft is used over relatively short distances, these cost and performance benefits offset the lower speed making turboprops the engine of choice for most commuter aircraft.
  • A turboprop engine uses the same principles as a turbojet to produce energy, that is, it incorporates a compressor, combust and turbine within the gas generator of the engine. The primary difference between the turboprop and the turbojet is that additional turbines, a power shaft and a reduction gearbox have been incorporated into the design to drive the propeller.
  •  The gearbox may be driven by the same turbines and shaft that drive the engine compressor, mechanically linking the propeller and the engine, or the turbines may be separate with the power turbine driving a concentric, mechanically isolated shaft to power the gearbox.
  • The latter design is referred to as a "free power turbine" or, more simply, a "free turbine" engine. In either case, the turbines extract almost all of the energy from the exhaust stream using some of it to power the engine compressor and the rest to drive the propeller.
  • Aircraft powered with turboprop engines go significantly faster than aircraft with propellers powered by reciprocating engines but not as fast as pure jet aircraft. Operating costs for turboprop planes are often one tenth the costs for turbojet powered planes.
  • Turboprop aircraft are generally used for shorter length flights than pure jets. They are efficient at lower altitudes and lower airspeed than pure jets. They are generally smaller in terms of seats and cargo capacity but have a wide range of sizes from a few seats to perhaps a hundred.
  • Turboprops also can operate from shorter runways than pure jets with similar payload capacities. That means they are ideal for some military applications where the C-130 has been a work horse for many decades.
  • Turboprop engines or turboshaft engines use the same basic turbine arrangement as a turbojet engine but are optimized to generate torque on a central shaft instead of maximizing thrust generated by the air/fuel flow in the engine. The shaft is connect to an otherwise normal propeller to provide most of the thrust to make an aircraft fly. In the case of helicopters the same type of engine is used to turn the main rotors and provide lift. These engines produce generally less power than fan jet engines but are much more efficient while producing this lower level of Power

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