In [1]:

```
#Given:
#For SI engine
F_A1 = 1/13.5 #Fuel air ratio
CV1 = 44000. #Calorific value in kJ/kg
eta_bt1 = 25. #Brake thermal efficiency in percent
m_f1 = 1. #Fuel consumption in kg/hr
#For CI engine
A_F2 = 25./1 #Air fuel ratio
CV2 = 42000. #Calorific value in kJ/kg
eta_bt2 = 38. #Brake thermal efficiency in percent
#Solution:
#(a)SI engine
bp1 = m_f1*CV1*eta_bt1/(100*3600) #Brake power in kW
bsfc1 = m_f1/bp1 #Brake specific fuel consumption in kg/kWh
m_a1 = bsfc1/F_A1 #Air consumption in kg/kWh
#(a)CI engine
m_f2 = 1. #Fuel consumption in kg/hr
bp2 = m_f2*CV2*eta_bt2/(3600*100) #Brake power in kW
bsfc2 = m_f2/bp2 #Brake specific fuel consumption in kg/kWh
m_a2 = bsfc2*A_F2 #Air consumption in kg/kWh
#Comparison
R_bp = bp1/bp2 #Ratio of brake power of SI to CI
R_bsfc = bsfc1/bsfc2 #Ratio of brake specific fuel consumption of SI to CI
R_m_a = m_a1/m_a2 #Ratio of fuel consumption of SI to CI
#Results:
print " For SI engine\tBrake output, bp = %.2f kW/kg of fuel\tBrake specific fuel consumption, bsfc = %.3f kg/kWh"%(bp1,bsfc1)
print " For CI engine\tBrake output, bp = %.1f kW/kg of fuel\tBrake specific fuel consumption, bsfc = %.3f kg/kWh"%(bp2,bsfc2)
print " The air consumption\tfor SI engine, m_a = %.2f kg/kWh\tfor CI engine, m_a = %.2f kg/kWh"%(m_a1,m_a2)
print " Comparison of SI to CI\tbp = %.3f\tbsfc = %.3f\tair consumption = %.3f"%(R_bp,R_bsfc,R_m_a)
```

In [2]:

```
#Given:
#For SI engine
s1 = 0.72 #Specific gravity of gasoline fuel
CV1 = 44800. #Calorific value of gasoline fuel in kJ/kg
eta_bt1 = 20. #Brake thermal efficiency in percent
A_F1 = 14. #Air fuel ratio
#For CI engine
s2 = 0.87 #Specific gravity of diesel oil
CV2 = 43100. #Calorific value of diesel oil in kJ/kg
eta_bt2 = 30. #Brake thermal efficiency in percent
A_F2 = 21. #Air fuel ratio
#Solution:
#SI engine
bsfc_SI = 3600*100/(eta_bt1*CV1) #Brake specific fuel consumption in kg/kWh
m_a_SI = A_F1*bsfc_SI #Air consumption in kg/kWh
#CI engine
bsfc_CI = 3600*100/(eta_bt2*CV2) #Brake specific fuel consumption in kg/kWh
m_a_CI = A_F2*bsfc_CI #Air consumption in kg/kWh
#Results:
print " For SI engine\tBrake specific fuel consumption, bsfc_SI = %.3f kg/kWh\tAir consumption = %.2f kg/kWh"%(bsfc_SI,m_a_SI)
print " For CI engine\tBrake specific fuel consumption, bsfc_CI = %.3f kg/kWh\tAir consumption = %.2f kg/kWh"%(bsfc_CI,m_a_CI)
```