Question

A turbojet aircraft is flying with a velocity of 280 m/s at an altitude of 9150 m, where the ambient conditions are 32 kPa and -32C. The pressure ratio across the compressor is 12, and the temperature at the turbine inlet is 1100 K. Air enters the compressor at a rate of 50 kg/s, and the jet fuel has a heating value of 42,700 kJ/kg. Assume constant specific heats for air at room temperature. Efficiency of the compressor is 80%, efficiency of the turbine is 85%. Assume air leaves diffuser with negligibly small velocity.
determine
(a) The velocity of the exhaust gases.
(b) The rate of fuel consumption.

Answer 1

Answer:

(a) The velocity of the exhaust gases. is 832.7 m/s

(b) The rate of fuel consumption is 0.6243 kg/s

Explanation:

For the given turbojet engine operating on an ideal cycle, the pressure ,temperature, velocity, and specific enthalpy of air at $i^{th}$ state are $P_i$ , $T_i$ , $V_i$ , and $h_i$ , respectively.

Use "ideal-gas specific heats of various common gases" to find the properties of air at room temperature.

Specific heat at constant pressure, $c_p$ = 1.005 kJ/kg.K

Specific heat ratio, k = 1.4