A compression ignition engine (6 cylinders, Vd = 5L, N = 2000rpm) operates under

Question

A compression ignition engine (6 cylinders, Vd = 5L, N = 2000rpm) operates under part load with phi = 0.5. It uses a diesel fuel with (F/A)stoich = 0.069.

a)

If the volumetric efficiency is assumed to be 90%, calculate the air flow rate into the engine (g/s). Assume air at standard conditions (101kPa, 298K).

b)

Based on the above fuel information, calculate the fuel mass flow rate (g/s) for the engine.

c)

Calculate the fuel injection time required (in ms) to meet the above fuel requirements. The injector flow rate is given as 20g/s.

d)

Find the injection pulse duration needed (in crank angle).

Explanation / Answer

Density of air at standard conditions

rho = P/R*T = 101/0.287*298

rho = 1.145 kg/m^3

Volumetric Efficiency = Mass flow rate of air/(rho*Vd*N) = ma/((rho*Vd*N))

ma = 0.9*1.145*5*10^-3*(2000/60)

ma = 0.17175 kg/s

ma = 171.75 g/s

b)

Given

(F/A)stoich = 0.069.

Phi = 0.5

But

Phi = (F/A)actual/(F/A)stoich

(F/A)actual/(F/A)stoich = 0.5

(F/A)actual = 0.0345

mf/ma = 0.0345

mf = 5.93 g/s

Mass flow rate of fuel is 5.93 g/s

c)

time taken is 296.5 ms

d)

Crank angle = t*RPM =296.5*10^-3*1000/60 = 4.95 deg

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