# Chapter 10 : Air Capacity of Four Stroke Engines¶

## Example 10.1 Page No : 238¶

In :
import math

#Given:
n  =  6.      #Number of cylinders
V_d  =  700.      #Displaced volume per cylinder in cm**3
bp  =  78.      #Brake power in kW
N  =  3200.      #Angular speed of engine in rpm
m_f  =  27.      #Petrol consumption in kg/hr
CV  =  44.      #Calorific value in MJ/kg

#Solution:
#(1)
A_F  =  12.      #Air-fuel ratio
P1  =  0.9
T1  =  32+273      #Intake air pressure and temperature in bar and K
m_a  =  A_F*m_f      #Air consumption in kg/hr
R  =  287.      #Specific gas consmath.tant in J/kgK
rho_a  =  P1*10**5/(R*T1)      #Density of air in kg/m**3
eta_vol  =  m_a/(60*rho_a*V_d*n*10**-6*N/2)      #Volumetric efficiency
#(2)
eta_bt  =  bp*3600/(m_f*CV*1000)      #Brake thermal efficiency
#(3)
T  =  bp*60/(2*math.pi*N)      #Brake torque in kNm

#Results:
print " 1)The volumetric efficiency, eta_vol   =   %.2f percent"%(eta_vol*100)
print " 2)The brake thermal efficiency, eta_bt   =   %.2f percent"%(eta_bt*100)
print " 3)The brake torque, T   =   %.0f Nm"%(T*1000)

 1)The volumetric efficiency, eta_vol   =   78.16 percent
2)The brake thermal efficiency, eta_bt   =   23.64 percent
3)The brake torque, T   =   233 Nm