Subtopic: Power efficiencies and measurement, engine performance curves
Question Statement:
A tractor engine delivers $36\text{ kW}$ brake power. The mechanical efficiency of the transmission between engine and PTO shaft is $92\%$. If the drawbar power developed during field tillage is $24\text{ kW}$, calculate the tractive efficiency in percentage.
Answer Key:
72.46
Step-by-Step Solution & Explanation
Power available at drive wheels (approx engine brake power minus transmission losses):
$P_{\text{axle}} = BP \times \eta_{\text{trans}} = 36 \times 0.92 = 33.12\text{ kW}$
Drawbar power $P_{\text{db}} = 24\text{ kW}$.
Tractive efficiency:
$\eta_{\text{tr}} = \frac{P_{\text{db}}}{P_{\text{axle}}} \times 100 = \frac{24}{33.12} \times 100 \approx 72.46\%$