A four stroke cylinder gasoline engine has six cylinders of 80 mm bore and 100 mm stroke. The engine is coupled to a rope break dynamometer having a radius of 400 mm. At 3200 rpm with all cylinders firing the net load is 350 N , when each cylinder is cut off the average net brake load produced at the same speed by the remaining five cylinders is 250 N. Estimate the indicated mean effective pressure of the engine. With all cylinders in operation the fuel consumption is 0.33 kg/min. The calorific value of fuel is 43 MJ/kg. The cooling water flow rate is 70 kg/min. and the temperature rise is 10°C. During test the engine is enclosed in a box and ventilating air is blown up through the box at a rate of 15 kg/min at 17°C. The air leaves the box at 62°C. Draw heat balance sheet for the engine on minute basis.

Given data:

4-stroke engine,

No. of cylinders=k=6,

Diameter of dynamometer = Db=0.4 m, D=0.08 m,

L=0.1 m

C.V. =43000 kJ/kg,

N=3200 rpm,

Temperature rise of cooling water=10°C,

i. Analyzing heat balance sheet on minute basis

1) Rate of heat supplied

2) Rate of heat distribution

a) B.P.

Substituting the values we get,

b) Rate at which heat is carried away by cooling water

c) Rate at which heat is carried away by ventilating air

Therefore, following is the heat balance sheet:

5) Indicated Mean Effective Pressure (i.m.e.p)