Question

Air at 7°C enters a turbojet engine at a rate of 16 kg/s and at a velocity of 220 m/s (relative to the engine). Air is heated in the combustion chamber at a rate 15,000 kJ/s, and it leaves the engine at 427°C. Determine the thrust produced by this turbojet engine.

Answer 1

F=14.05 KN

Step-by-step explanation:

Now from first law for open system

`h_1+(V_1^2)/(2)+Q=h_2+(V_2^2)/(2)+w`

In Turbojet net work out put is zero because ,power produce by turbine is consumed by compressor.

So w=0

Given mass flow rate =16 kg/s

`V_1=220 m/s`

Heat input Q=15000 KW (Q=937.5 KJ/kg)

`h_1+(V_1^2)/(2)+Q=h_2+(V_2^2)/(2)`

`1.005* (273+70)+(220^2)/(2000)+937.5=1.005* (273+427)+(V_2^2)/(2000)`

So
`V_2=1098.1 m/s`

So thrust

`F=\dot{m_a}(V_2-V_1)`

F=16(1098.32-220)

F=14.05 KN