Subtopic: Power efficiencies and measurement, engine performance curves
Question Statement:
The high idle speed of an engine is 2240 rpm and the governor regulation is 11.5%. The peak torque of 180 N m occurs at 1450 engine rpm. If lugging ability is 28 Nm, the engine power in kW at governor's maximum position will be
Options:
(A) 31.8
(B) 35.7
(C) 37.6
(D) 42.2
Official Answer Key:
A
Step-by-Step Solution & Explanation
Governor regulation = (N_high-idle − N_rated)/N_rated ⟹ N_rated = N_high-idle/(1+regulation) = 2240/1.115 = 2008.97 rpm — this is the engine's rated (governed, full-load) speed, i.e., the 'governor's maximum (load) position'. Lugging ability = peak torque − rated torque ⟹ T_rated = 180 − 28 = 152 N·m. Power = 2πNT/60000 (kW, N in rpm, T in N·m) = 2π × 2008.97 × 152 / 60000 = 31.98 kW ≈ 31.8 kW, matching option (A).
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