TURBOPROP ENGINES

In a turboprop engine a propeller mounted in front of the jet engine is driven either by a second, or free, turbine or by additional stages from the turbine that supplies power to the compressor. About 90 percent of the energy of the expanding gases is absorbed in the turbine portionthat dives the propeller, leaving only about 10 percent to accelerate the the overall propulsive thrust. Turboprops have certain advantages for small and medium-sized planes at speeds of up to about 480 to 640 km/h. They cannot compete, however, with turbojets or fanjets for very large planes and for higher speeds.

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