Allied & ICAR Exam Bank • ALLIED_1119 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Engine Volumetric Efficiency

Question Statement:

A 4-stroke 2.0-litre diesel engine operates at 2400 rpm. The measured dry air intake mass flow rate is 0.042 kg/s at intake air density $\rho = 1.20\text{ kg/m}^3$. The volumetric efficiency of the engine (in %) is:

Answer Key:

87.5

Step-by-Step Solution & Explanation

Displacement volume rate $\dot{V}_d = V_s \times \frac{N}{2 \times 60} = 0.002\text{ m}^3 \times 20\text{ s}^{-1} = 0.040\text{ m}^3/\text{s}$. Mass of air displaced $\dot{m}_{th} = \dot{V}_d \times \rho = 0.040 \times 1.20 = 0.048\text{ kg/s}$. Volumetric efficiency $\eta_v = \frac{\dot{m}_a}{\dot{m}_{th}} \times 100 = \frac{0.042}{0.048} \times 100 = 87.5\%$.
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