Propulsive power (Benefit) WP P Input energy (Cost) Qin AfterburnerĪfterburner is popular in military aircrafts and it is used whenever a need for extra thrust arises, such as for short takeoffs or combat conditions. This then becomes a measure of how efficiently the energy released during the combustion process is converted to propulsive energy.
The thermal efficiency is defined based on the propulsive power. WP FVaircraft mVexit Vinlet Vaircraft The power developed from the thrust of the engine is called the propulsive power: The pressure at the inlet and the exist of a turbojet engine are identical (the ambient pressure) thus the net thrust developed by the engine is: F mV mV mVexit Vinlet exit inletįor an aircraft cruising in still air, Vinlet is the aircraft velocity. Gases are expanded to produce a high velocity, Ve > Vi results in a thrust Gases leave the turbine significantly higher in pressure than atmospheric pressure Isentropic expansion through the nozzle, air accelerates and the pressure deceases Turbine power just enough to drive the compressorĪir and fuel are mixed and burned in the combustion chamber at constant pressureĪir velocity leaving the turbine is small and can be neglected It can be explained through the Bernoulli’s equation:Ĭompressor, Burner and Turbine (2-5) 2-3: isentropic compression 3-4: constant pressure heat addition 4-5: isentropic expansion through the turbine during which work is developed
Bahramiĭecelerates the incoming flow relative to the engineĪ pressure rise known as a ram effect occurs, V (↓), P (↑). Typically operate at higher pressure ratios, often in the range of 10 to 25 Vinletįig. The fluid passes through a diffuser first where it is decelerated (gas pressure increases)
Since the gases leave at a high velocity, the change in momentum that the gas undergoes provides a thrust to the aircraft Gases are expanded in the turbine to a pressure where the turbine work is just equal to the compressor work plus some auxiliary power for pumps and generators i.e. Some of the major differences between the gas-turbine and jet-propulsion cycles are: Aircraft gas turbines operate on an open cycle called jet-propulsion cycle. Ideal Jet‐Propulsion Cycle Gas-turbine engines are widely used to power aircrafts because of their light-weight, compactness, and high power-to-weight ratio.