Question

A Brayton gas power cycle is used to power a jet engine. The fuel used has calorific value of 50 Mj/kg. Jet engine has..a velocity of 800 m/s and produces net thrust of 6 kM If the fuel consumption is 0.2 kg per hour per N of thrust. The overall efficiency of gas power cycle is _____ % ( Correct upto 2 decimal places)

• A. 28.8

Answer 1

The correct option is A 28.8
Given $(C_V{)}_f=50MJ/kg$
$V=800m/s$
$F=6kN$
$\Rightarrow$ Thrust power =F.V $=6\times 800=4800kW$
$\Rightarrow$ ${\dot{m}}_f=fuelconsumption$
$=\frac{0.2}{3600}\times 6000kg/s=\frac{1}{3}kg/s$
$\Rightarrow$ Heat input ${\dot{m}}_f$(CV)_f = $\frac{1}{3}\times 50\times {10}^{3}kW$
$=\frac{50,000}{3}kW$
$\Rightarrow$ Overall efficiency $-\frac{4800}{50000/3}\times 100$% = 28.8%