Allied & ICAR Exam Bank • ALLIED_1103 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Engine Testing

Question Statement:

In a Morse test on a 4-cylinder, 4-stroke petrol engine running at constant speed, the total brake power with all cylinders firing is 32.0 kW. The brake powers measured when cylinders 1, 2, 3, and 4 are cut out in turn are 23.0 kW, 22.5 kW, 23.2 kW, and 22.8 kW, respectively. The mechanical efficiency of the engine (in %) is:

Answer Key:

87.7

Step-by-Step Solution & Explanation

Indicated powers of cylinders: $IP_1 = 32.0 - 23.0 = 9.0\text{ kW}$, $IP_2 = 32.0 - 22.5 = 9.5\text{ kW}$, $IP_3 = 32.0 - 23.2 = 8.8\text{ kW}$, $IP_4 = 32.0 - 22.8 = 9.2\text{ kW}$. Total $IP = 9.0 + 9.5 + 8.8 + 9.2 = 36.5\text{ kW}$. Mechanical efficiency $\eta_m = \frac{BP}{IP} \times 100 = \frac{32.0}{36.5} \times 100 = 87.67\%$.
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