Allied & ICAR Exam Bank • ALLIED_1108 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Fuel Consumption and Economy

Question Statement:

A tractor diesel engine develops 30 kW brake power while consuming 7.5 kg of diesel fuel per hour. The calorific value of the diesel fuel is 42,000 kJ/kg. The brake thermal efficiency of the engine (in %) is:

Answer Key:

34.3

Step-by-Step Solution & Explanation

Rate of heat supply $Q_{in} = \frac{\dot{m}_f \times CV}{3600} = \frac{7.5 \times 42,000}{3600} = 87.5\text{ kW}$. Brake thermal efficiency $\eta_{bth} = \frac{BP}{Q_{in}} \times 100 = \frac{30.0}{87.5} \times 100 \approx 34.29\%$.
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