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+//Calculations on gas engine

+clc,clear

+//Given:

+d=27,l=45 //Bore and stroke in cm

+D_b=1.62 //Effective diameter of the brake wheel in m

+t=38.5 //Duration of test in min

+N=8080,N1=3230 //Number of revolutions and explosions

+P=903 //Net load on brake in N

+imep=5.64 //Indicated mean effective pressure in bar

+Vg1=7.7 //Gas used in m^3

+T1=27+273 //Temperature of the gas in K

+deltaP1=135 //Pressure difference of gas above atmospheric pressure in mm of water

+Patm=750 //Atmospheric pressure in mm of Hg 

+CV=18420 //Calorific value of the gas in kJ/m^3 at N.T.P.

+m_w=183 //Mass of cooling water used in kg

+deltaT_w=47 //Cooling water temperature rise in degreeC

+//Solution:

+P1=Patm+deltaP1/13.6 //Gas pressure in mm of Hg

+P1=P1/750 //Gas pressure in bar

+T2=0+273,P2=1.013 //Normal temperature and pressure (N.T.P.) in K and bar

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

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

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

+bp=2*%pi*(N/t*1/60)*(T)*10^-3 //Brake power in kW

+bp=round(10*bp)/10

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

+A=%pi/4*d^2*10^-4 //Area of cylinder in m^2

+ip=imep*10^2*l/100*A*(N1/t*1/60) //Indicated power in kW

+ip=round(10*ip)/10

+Q_ip=ip*60 //Heat equivalent to indicated power in kJ/min

+fp=ip-bp //Frictional power in kW

+Q_fp=fp*60 //Heat equivalent to frictional power in kJ/min

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

+Q_w=m_w/t*cp*(deltaT_w) //Heat in cooling water in kJ/min

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

+eta_it=Q_ip/Q1 //Indicated thermal efficiency

+eta_bt=Q_bp/Q1 //Brake thermal efficiency

+//Results:

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

+printf("\n The brake thermal efficiency, eta_bt = %.1f percent",eta_bt*100)

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

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

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

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