I have been asked to calculate the following problem and I am struggling with calculating the volumetric efficiency part c. So far I have calculated:

A 4 cylinder 4 stroke engine of 78mm bore and 105mm stroke develops an indicated power of 47.5kW at 4400rpm. The air/fuel ratio is 21kg air/kg fuel, the fuel consumption is 13.6 kg/h and the calorific value is 41.8Mj/kg. Calculate:

a. mean effective pressure:

Using IP= 100 rho LAN (For kW)

gives : rho = IP/100LAN

= 47.5/ 100 * (PI*{0.078^2/4}* 0.105 * 73.3/2 = 47.5/1.838 = 25.84 bar

b. Indicated thermal efficiency

Using eta Ith = IP/FP where FP = Mf x cv

eta Ith= IP/mf * cv

eta Ith= 47.5 * 10^3/ 0.037*41800 = 0.3071 = 30.7%

c. Volumetric efficiency given inlet conditions 1 bar and 15 deg C. R=287 J/kgK.

I have found out that volumetric efficiency is the ratio of actual air mass drawn into the engine during one cycle to that of atmospheric conditions.

eta volumetric = actual mass of air/ rho(atmosheric conditions) * displacement

or

eta volumetric = rev per cycle * steady air flow in / rho(atmosheric conditions) * displacement * engine speed

I am struggling to find the actual mass of air drawn in or steady air flow in any help will be greatly appreciated.

Thanks James