Question Bank • QB_FP_051 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Power efficiencies and measurement, engine performance curves

Question Statement:

A Prony brake dynamometer is used to measure the brake power of an agricultural diesel engine running at $N = 1500\text{ rpm}$. The effective moment arm from the shaft centerline to the balance knife-edge is $L = 0.75\text{ m}$. The net load registered on the balance scale is $W = 280\text{ N}$. Taking $\pi = 3.1416$, the brake power of the engine in $\text{kW}$ is ________ (round off to 2 decimal places).

Answer Key:

32.99

Step-by-Step Solution & Explanation

1. Braking torque ($T$): $T = W \times L = 280\text{ N} \times 0.75\text{ m} = 210.0\text{ N}\cdot\text{m}$ 2. Brake power ($BP$): $BP = \frac{2 \pi N T}{60 \times 1000} = \frac{2 \times 3.1416 \times 1500 \times 210.0}{60,000} = \frac{1,979,208}{60,000} \approx 32.9868\text{ kW} \approx 32.99\text{ kW}$
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