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+//Calculations on Gas engine

+clc,clear

+//Given:

+d=24,l=48 //Bore and stroke in cm

+D_b=1.25 //Effective diameter of the brake wheel in m

+P=1236 //Net load on brake in N

+N=77 //Average engine explosions in min

+N1=226.7 //Average speed at output shaft in rpm

+imep=7.5 //Indicated mean effective pressure in bar

+Vg1=13 //Gas used in m^3/hr

+T1=15+273,P1=771 //Temperature and pressure of the gas in K and mm of mercury

+T2=0+273,P2=760 //Normal temperature and pressure (N.T.P.) in K and mm of mercury

+CV=22000 //Calorific value of the gas in kJ/m^3

+m_w=625 //Mass of cooling water used in kg/hr

+T1_w=25+273,T2_w=60+273 //Inlet and outlet temperature of cooling water in K

+//Solution:

+//(a)

+T=P*D_b/2 //Brake torque delivered in Nm

+bp=2*%pi*N1/60*T //Brake power in W

+ip=imep*10^5*l*%pi/4*d^2*N/60*10^-6 //Indicated power in W

+eta_m=bp/ip //Mechanical efficiency

+//(b)

+Vg2=(P1/P2)*(T2/T1)*Vg1 //Gas consumption at N.T.P. in m^3/hr

+//(c)

+eta_it=ip/1000*3600/(Vg1*CV) //Indicated thermal efficiency

+//Heat balance sheet

+Q1=Vg2/60*CV //Heat supplied in kJ/min

+Q_bp=bp/1000*60 //Heat equivalent to brake power in kJ/min

+cp=4.1868 //Specfic heat of water in kJ/kgK

+Q_w=m_w/60*cp*(T2_w-T1_w) //Heat in cooling water in kJ/min

+Q_r=Q1-Q_bp-Q_w //Heat to exhaust, radiation in kJ/min

+//Results:

+printf("\n (a)The mechanical efficiency of the engine, eta_m = %.1f percent",eta_m*100)

+printf("\n (b)The gas consumption at N.T.P. = %.1f m^3/hr",Vg2)

+printf("\n (c)The indicated thermal efficiency, eta_it = %.1f percent",eta_it*100)

+printf("\n\n   Heat balance sheet\n\t Heat supplied by the gas = %.1f kJ/min, %d percent",Q1,Q1/Q1*100)

+printf("\n\t Heat equivalent to b.p. = %.1f kJ/min, %.1f percent",Q_bp,Q_bp/Q1*100)

+printf("\n\t Heat in cooling water = %.1f kJ/min, %.1f percent",Q_w,Q_w/Q1*100)

+printf("\n\t Heat to exhaust, radiation = %.1f kJ/min, %.1f percent",Q_r,Q_r/Q1*100)