# Chapter 16 : Two Stroke Engines¶

## Example 16.1 Page No : 328¶

In :
import math

#Given:
n  =  2.      #Number of cylinders
N  =  4000.      #Angular speed of engine in rpm
eta_v  =  0.77      #Volumetric efficiency
eta_m  =  0.75      #Mechanical efficiency
V_f  =  10.      #Fuel consumption in l/hr
s  =  0.73      #Specific gravity
h  =  10500.      #Enthalpy of fuel in kcal/kg
A_F  =  18.      #Air-fuel ratio
v_p  =  600.      #Speed of piston in m/min
imep  =  5.      #Indicated mean effective pressure in atm
T  =  298.
P  =  1.013      #Smath.radians(numpy.arcmath.tan(ard temperature and pressure in K and bar

#Solution:
R  =  0.287      #Specific gas consmath.tant in kJ/kgK
m_f  =  V_f*s      #Fuel consumption in kg/hr
m_a  =  A_F*m_f      #Air consumption in kg/hr
m_c  =  m_f+m_a      #Mass of total charge in kg/hr
m  =  round(m_c/eta_v)      #Mass of charge corresponding to the swept volume in kg/hr
V  =  (m/2)*R*T/(P*100)      #Volume of charge consumed in m**3/hr
V_s  =  V*10**6/(60*N)      #Swept volume by piston per stroke in cc
L  =  v_p*100/(2*N)      #Stroke length of cylinder in cm
d  =  math.sqrt(4*V_s/(math.pi*L))      #Bore of cylinder in cm
IHP  =  round(imep*V_s*N*n/450000)      #Indicated horse power in metric HP
BHP  =  IHP*eta_m      #Brake horse power in metric HP
eta_t  =  BHP*736*3600/(V_f*s*h*4187)      #Thermal efficiency

#Results:
print " The engine dimensions\t Stroke length, L   =   %.1f cm\t Bore, d   =   %.1f cm"%(L,d)
print " The brake power output, BHP   =   %.1f metric HP"%(BHP)
print " The thermal efficiency, eta_t   =   %.1f percent"%(eta_t*100)

 The engine dimensions	 Stroke length, L   =   7.5 cm	 Bore, d   =   7.3 cm
The brake power output, BHP   =   21.0 metric HP
The thermal efficiency, eta_t   =   17.3 percent