Question

A four cylinder, four stroke petrol engines has a 10 cm bore, 15 cm stroke and uses a compression ratio of 6. The engine develops 25 kW indicated power at 2000 rpm. Estimate the mean indicated pressure and air standard efficiency. Also calculate the fuel consumption per hour, if the indicated thermal efficiency is 30%. Take the calorific value of fuel as 42 MJ/kg​

Answer 1

Given: No. of strokes per cycle for the engine,  S =  2;

            Actual mean effective pressure, pam = 6 bar;

    Engine speed, N = 1000 r.p.m;

    Diameter of the piston, D = 110 mm = 0.11 m;      

    Stroke length, L = 140 mm = 0.14 m;

    No. of cylinders = 1;

    No. of missed cycle, nmc = 0;

Determine the indicated power developed, I.P.:

Formula:   Indicated power developed,  IP =   × (No. of cylinders), kW

     =     × (No. of cylinders)       [  nmc = 0]

Answer:  Indicated power, I.P =  × (No. of cylinders)

                                                     = 13.3 kW

Problem 48.2: A 4-cylinder four-stroke petrol engine develops 14.7 kW at 1000 r.p.m. The mean effective pressure is 5.5 bar, Calculate the bore and stroke of the engine, if the length of  stroke is 1.5 times the bore.

Solution:

Given:   Number of cylinder, ncyl = 4;

       No. of strokes per cycle for the engine, S = 4;      

             Power developed,   I.P. = 14.7 kW;

      Engine speed, N = 1000 r.p.m.;

     Actual mean effective pressure, Pam = 5.5 bar;

     Length of stroke, L = 1.5 D (bore);

     No. of missed cycle, nmc = 0.

Determine the bore, D and stroke, L of the engine: