Jet population systems in which the workout put of the gas turbine plant is used to produce high velocity of hot gases.
The various types of jet propulsion systems are.
- Screw propeller
- Turbo propeller
This engine is producing power by partial expansion, just sufficient to drive the compressor. At higher speeds of the turbojet gives higher propulsion efficiency.
These engines have the capability to fly at supersonic speeds. A ramjet is always equipped with a small turbojet which starts the ramjet.
In this type the total power is developed by the turbine is used to drive the compressor and propeller.
The turbo propeller type of system is employed in air craft systems. The expansion of gases takes place partly in turbine and partly in the nozzle. In this system the power is developed by the turbine. It is consumed in running the compressor and propeller.
The overall efficiency of the turbo propeller system is improved by providing the diffuser before the compressor.
- Propulsive efficiency = Thrust power / Propulsive power
- Jet efficiency = Final kinetic energy in the jet / Isentropic heat drop in the jet pie + carry over from turbine