A 4 stoke engine with 6 cylinders is designed to run at a ma

\"A 4 stoke engine with 6 cylinders is designed to run at a maximum power of 257 kW at 7000 rpm. Each cylinder has a bore and stroke of 94 x 83 mm, and runs at a compression ratio of 10:1. The fuel has a heating value of 43 MJ/kg. For SI engines assume the thermal efficiency is 32%, the engine runs at a lambda ratio = 1.1 and the fuel is gasoline (C7H16). For CI engines assume the thermal efficiency is 40%, the engine runs at a lambda ratio = 1.5 and the fuel is cetane (C16H34). Determine the volumetric efficiency in % at peak power. Assume the air density to be 1.189 kg/m3.\"

Solution

Swept Volume Vsw = pi/4*D^2 * L * Ncyl

= 3.14/4*0.094^2 * 0.083 * 6

= 3454.25748*10^-6 m^3

Power = 2*pi*N*T/60

257*10^3 = 2*3.14*7000*T / 60

Torque T = 350.8 Nm

Thermal efficiency = Work done / heat input

0.32 = 350.8 / (mf * 43*10^6)

Fuel consumed mf = 25.49 mg/cycle

For gasoline, stoichiometric air-fuel ratio = 15.1

Actual air-fuel ratio = 15.1*1.1 = 16.61

Air consumed = 25.49*16.61 = 423.4 mg/cycle

Volume of air consumed = 423.4*10^-6 / 1.189 = 356.1*10^-6 m^3/cycle

Voleff = 356.1*10^-6 / 3454.25748*10^-6

= 10.3%