A turbojet engine takes 50 (kg/sec) of air and propels an aircraft with uniform flight speed of 880 (km/hr). Isentropic enthalpy change for the nozzle is 188.28 (kJ/kg) and its velocity coefficient (being a ratio of the velocity of the jet relative to the aircraft speed over the exit velocity of gases) is 0.96. The fuel/air ratio is 1.2 percent. Combustion efficiency is 95 percent, and the calorific value of fuel is 4.393 x 104(kJ/kg).
(1) the thermal efficiency of the engine,
(2) the fuel flow in (kg/hr) and specific fuel consumption,
(3) the thrust power, propulsive efficiency, and overall efficiency.
- ṁa = 50 kg/sec
- Vaircraft = 880 km/hr = 244 m/sec
- Isentropic enthalpy change for Nozzle h5 – h6s = 188.28 kJ/kg
- Fuel/Air = 1.2 % = 0.012
- ṁf/ṁa = 0.012
- Combustion efficiency ηcombustion = 95 %
- Calorific Value of fuel CVf = 4.393 x 104 kJ/kg