Model the cycle in the aircraft engine as an ideal jet-propulsion cycle. The T-s diagram of the ideal jet-propulsion cycle described is shown on the left.
The braking force equals the thrust developed by the engine when the airplane is stationary. The thrust can be determined by
mass flow rate of air, given as 8 kg/s
vexit = velocity of
air at the exit of the nozzle
vinlet = velocity of air at
the inlet of the engine
The airplane is stationary on the ground and the air velocity at the
inlet of the engine is negligible. Also, the effect of diffuser is negligible.
Thus, the thrust can be simplified as
The exit velocity of the nozzle can determined by the energy balance of
the nozzle. In steady-flow condition, it is
The above analysis shows that in order to calculate the exit velocity,
temperatures at state 4 and state 5 need to be determined first.
T1 = 300 K (given)
P1 = 100 kPa (given)
P2/P1 = rP = 10 (given)
P2 = P1rP = 100(10) = 1,000 kPa
Process 1-2: isentropic compression.
Process 2-3: constant pressure heat addition
P3 = P2 = 1,000 kPa
Heat transfer into the cycle equals,
The temperature at state 3 is