Subtopic: Thermodynamic principles of I.C. engines
Question Statement:
A power tiller with diesel engine produces 12 kW of brake power with a brake thermal efficiency of 30 %. If the air-fuel ratio in the combustion process is 14:1 and heating value of the fuel is 45 MJ kg⁻¹, air consumption rate of the engine will be ________ kg h⁻¹.
Official Answer Key:
44.50 to 45.00
Step-by-Step Solution & Explanation
Brake thermal efficiency: η_bth = BP / (ṁ_f × CV).
Heat supply rate = 12/0.30 = 40 kW = 40 kJ s⁻¹.
ṁ_f = 40/45000 = 8.889 × 10⁻⁴ kg s⁻¹ = 3.20 kg h⁻¹.
ṁ_air = (A/F) × ṁ_f = 14 × 3.20 = 44.8 kg h⁻¹ — within the official range 44.50–45.00.
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