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Turbofan Engines

Turbofan Engines

  • The turbofan gas turbine engine is, in principle, the same as  a turboprop, except that the propeller is replaced by a ductenclosed naxial-flow fan. The fan can be a part of the first-stage compressor blades or can be mounted as a separate set of fan blades. The blades can be mounted forward of the compressor.
  • The general principle of the fan engine is to convert more of the fuel energy into pressure. With more of the energy converted to pressure, a greater product of pressure times area can be achieved.
  • One of the major advantages is turbofan production of this additional thrust without increasing fuel flow. The end result is fuel economy with the consequent increase in range.
  •  Because more of the fuel energy is turned into pressure in the turbofan engine, additional stages must
  • be added in the turbine section to provide the power to drive the fan.
  • This means there is less energy left over and less thrust from the core exhaust gases. Also, in a mixed-exhaust nozzle (where fan air and core air mix in a common nozzle before entering ambient conditions) the exhaust nozzle must be larger in area.
  •  The result is that the fan develops most of the thrust. The thrust produced by the fan more than makes
  • up for the decrease in thrust of the core (gas generator) of the engine. Depending on the fan design and bypass ratio, it produces 80 percent of the turbofan engine’s total thrust.

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