Question

A sports car engine delivers 150 kW to the driveshaft with a thermal efficiency of 20%. The fuel has a heating value of 35 000 kJ/kg. Find the rate of fuel consumption and the combined power rejected through the radiator and exhaust.

Answer 1

Answer:600 kW

Explanation:

Given

Power delivered $P=150 kW$

Fuel heating value $q=35,000 kJ/kg$

thermal Efficiency $\eta =\frac{Power}{Heat}$

$0.2=\frac{150}{35,000\times \dot{m}}$

where, $\dot{m} =mass\ flow\ rate\ of\ fuel$

$\dot{m}=\frac{150}{35,000\times 0.2}$

$\dot{m}=0.0214 kg/s$

For an Engine

$q\dot{m}=P+Q_r , where Q_r=heat\ rejected$

$Q_r=q\dot{m}-P$

$Q_r=750-150=600 kW$