Example 1 Page No:281

In [1]:
#Input data
import math
Pa=10                            #Single cylinder double acting steam engine pressure in bar 
Pb=1.5                           #Single cylinder double acting steam engine pressure in bar
rc=100/35                        #Cut-off of the stroke in %


#Calculation
Pm=((Pa/rc)*(1+math.log(rc))-Pb) #Therotical mean effective pressure

#Output
print("Therotical mean effective pressure=",round(Pm,2),"bar")

Therotical mean effective pressure= 5.67 bar

Example 2 Page No:283

In [2]:
#Input data

a=5/100     #Engine cylinder of the stroke valume in %
P1=12       #Pressure of the stream
rc=3        #Cut-off is one-third
Pb=1.1      #Constant the back pressure in bar

#Calulation
#Therotical mean effective pressure Pm
Pm=P1*(1/rc+((1/rc)+a)*math.log((1+a)/((1/rc)+a)))-Pb 

#Output
print("#Therotical mean effective pressure=",round(Pm,2),"N/m**2")

#Therotical mean effective pressure= 7.54 N/m**2

Example 3 Page No:285

In [3]:
#Input data
import math
P1=14           #Steam is ssupplied in bar          
P6=6            #Pressure at the end in bar
Pb=1.2          #Pressure at back in bar
a=0.1           
re=4 
#From hyperbolic process 
b=0.4

#Calculation
#Mean Effective pressure in N/m**2 
Pm=P1*((1/re)+((1/re)+a)*math.log((1+a)/((1+re)+a)))-Pb*((1+b)+(a+b)*math.log((a+b)/a))


#Output
print("Mean Effective pressure=",round(-Pm,3),"N/m**2")

Mean Effective pressure= 6.662 N/m**2

Example 4 Page No:286

In [4]:
#Input data
Cover=1200                       #Area of the indicator diagram for cover 
Crank=1100                       #Area of the indicator diagram for crank
ID=75
PS=0.15


#Calculation
CoverMEP=Cover/ID*PS             #Cover end mean effective pressure
CrankMEP=Crank/ID*PS             #Crank end mean effective pressure
AverageMEP=(CoverMEP+CrankMEP)/2 #Average end mean effective pressure


#Output
print("Cover end mean effective pressure=",CoverMEP,"bar")
print("Crank end mean effective pressure=",round(CrankMEP,2),"bar")
print("Average end mean effective pressure=",AverageMEP,"bar")

Cover end mean effective pressure= 2.4 bar
Crank end mean effective pressure= 2.2 bar
Average end mean effective pressure= 2.3 bar

Example 5 Page No:286

In [5]:
#Input data
a=25                  #Area of indicator diagram cm**2
Vs=0.15               #swept volume m**2
S=1                   #Scale in cm 
cm=0.02               #pressure axis m**3


#Calculation
b=Vs/cm               #Base length of diagram 
Pm=a/b*S              #Mean effective pressure

#Output
print("Base length of diagram=",b,"bar")
print("Mean effective pressure=",round(Pm,2),"bar")

Base length of diagram= 7.5 bar
Mean effective pressure= 3.33 bar

Example 6 Page No:287

In [6]:
#Input data
import math
P1=14                            #Steam Engine pressure in bar
Pb=0.15                          #Back pressure in bar
K=0.72                           #Diagram factor
rc=100/20 

#Calculation
Pm=((P1/rc)*(1+math.log(rc))-Pb) #Therotical mean effective pressure Pm
Pma=Pm*K                         #Actual mean effective pressure Pma

#Output
print("Therotical mean effective pressure=",round(Pm,3),"bar")
print("Actual mean effective pressure=",round(Pma,2),"bar")

Therotical mean effective pressure= 7.156 bar
Actual mean effective pressure= 5.15 bar

Example 7 Page No:287

In [7]:
#Input data
import math
P1=9                         #Reciprocating engine pressure in bar
Pb=1.5                       #Back pressure in bar
rc=100/25                    #Cut-off 
K=0.8                        #Diagram factor

#Calculation
Pm=((P1/rc)*(1+math.log(rc))-Pb) #Therotical mean effective pressure Pm
Pma=Pm*K                         #Actual mean effective pressure Pma

#Output
print("Therotical mean effective pressure= ",round(Pm,2),"bar")
print("Actual mean effective pressure=",round(Pma,2),"bar")

Therotical mean effective pressure=  3.87 bar
Actual mean effective pressure= 3.1 bar

Example 8 Page No:288

In [8]:
#Input data
import math
P1=10                   #Inlet pressure
Pb=1                    #Back pressure
rc=3                    #Expansion ratio
a=12.1                  #Area of indicator diagram
b=7.5                   #Length of indicator diagram 
S=3                     #Pressure scale


#calculation
Pm=((P1/rc)*(1+math.log(rc))-Pb )#Therotical mean effective pressure Pm
Pma=a/b*S                        #Actual mean effective pressure Pma
K=Pma/Pm                         #diagram factor 

#Output
print("Therotical mean effective pressure=",round(Pm,2),"bar")
print("Actual mean effective pressure=",round(Pma,2),"bar")
print("Diagram factor=",round(K,3),)

Therotical mean effective pressure= 6.0 bar
Actual mean effective pressure= 4.84 bar
Diagram factor= 0.807

Example 9 Page No:289

In [9]:
#Input data
D=200*10**-3                     #Steam engine cylinder in mm  
L=300*10**-3                     #Bore of steam engine cylinder in mm  
rc=100/40                        #Cut-off of the sroke
P1=7                             #Admission pressure of steam in bar
Pb=0.38                          #Exhaust pressure of steam in bar
K=0.8                            #Diagram factor
N=200                            #Indicator factor of engine
pi=3.142                         #Constant value
#Indicated power of the engine  in rpm
A=pi*(200*10**-3)**2/4


#Calculation
Pm=((P1/rc)*(1+math.log(rc))-Pb)  #Therotical mean effective pressure Pm
Pma=Pm*K                          #Actual mean effective pressure Pma
IP=(2*Pma*L*A*N/60000)*10**5      #Indicated power of steam engine in Kw


#Output
print("Therotical mean effective pressure= ",round(Pm,3),"bar")
print("Actual mean effective pressure=",round(Pma,),"bar")
print("Indicated power of steam engine=",round(IP,2),"Kw")

Therotical mean effective pressure=  4.986 bar
Actual mean effective pressure= 4 bar
Indicated power of steam engine= 25.06 Kw

Example 10 Page No:290

In [10]:
#Input data
import math
IP=343                  #Steam engine develop indicated power in Kw
N=180                   #power In rpm
P1=15                   #Steam supplied i bar                   
Pb=1.25                 #Steam is exhausted in bar
rc=100/25               #Cut-off take place of stroke
K=0.78                  #Diagram factor
#x=L/D=4/3
x=4/3                   #Stroke to bore ratio
pi=3.142
A=((pi/4)*(D**2))

#calculation
Pm=((P1/rc)*(1+math.log(rc))-Pb)    #Therotical mean effective pressure Pm
Pma=Pm*K                            #Actual mean effective pressure Pma
D=(((60000*IP)/(2*(Pma*10**5)*(4/3)*N))/(pi/4))**(1/3)#Indicated power of steam engine
L=(x)*D


#Output
print("Therotical mean effective pressure=",round(Pm,2),"bar")
print("Actual mean effective pressure=",round(Pma,2),"bar")
print("Indicated power of steam engine=",round(D,3),"mm")
print("Indicated power of steam engine=",round(L,1),"mm")

Therotical mean effective pressure= 7.7 bar
Actual mean effective pressure= 6.0 bar
Indicated power of steam engine= 0.45 mm
Indicated power of steam engine= 0.6 mm

Example 11 Page No:290

In [11]:
#Input data
import math
D=240*10**-3  #Steam engine bor
L=300*10**-3  #Stroke of engine
N=220         #Speed of engine 220 in rpm      
IP=36         #Indicated power in Kw
Pb=1.3        #Exhaust pressure in bar
re=2.5        #Expansion ratio
K=0.8         #Diagram factor
A=((pi/4)*(D**2))


#Calculation
Pma=((IP*60000)/(2*10**5*L*A*N))  #Indicated power of steam engine in bar
Pm=Pma/K                          #Actual mean effective pressure in bar
P1=((Pm+Pb)*re)/(1+math.log(re))  #Theoretical mean effective pressure in bar

#Output
print("Indicated power of steam engine=",round(Pma,3),"bar")
print("Actual mean effective pressure=",round(Pm,3),"bar")
print("theoretical mean effective pressure=",round(P1,1),"bar")

Indicated power of steam engine= 3.617 bar
Actual mean effective pressure= 4.521 bar
theoretical mean effective pressure= 7.6 bar

Example 12 Page No:291

In [12]:
#Input data
import math
D=700*10**-3             #Steam engine diameter in mm
L=900*10**-3             #Steam engine diameter in mm
Ip=450                   #Develop indicated power Kw
N=90                     #Speed of steam engine in rpm
P2=12                    #Pressure at cut-off in bar
P1=12                    #Pressure at cut-off in bar
Pb=1.3                   #Back pressure in bar
K=0.76                   #Diameter factor
pi=3.142
A=((pi/4)*0.7**2)

#Calculation
Pma=(Ip*60000)/(2*10**5*L*A*90) #Indicated power of steam engine in bar
Pm=Pma/K                        #Theoretical mean effective pressure in bar
#using trial and error method
re=1/0.241                             #Expansion ratio
#Output
print("Indicated power of steam engine=",round(Pma,2),"bar")
print("Theoretical mean effective pressure=",round(Pm,1),"bar")
print("Expansion ratio=",round(re,2),)

Indicated power of steam engine= 4.33 bar
Theoretical mean effective pressure= 5.7 bar
Expansion ratio= 4.15

Example 13 Page No:293

In [13]:
#Input data
Db=900*10**-3      #Diameter of break drum in mm
dr=50*10**-3       #Diameter of rope in mm
W=105*9.81         #dead weight on the tight side of the rope in Kg
S=7*9.81           #Spring balance of the rope in N
N=240              #Speed of the engine in rpm

#Calculation
T=(W-S)*((Db+dr)/2) #Torque Nm
Bp=2*pi*N*T/ 60000  #Brake Power in Kw

#Output
print("Torque= ",round(T,2),"Nm")
print("Brake Power=",round(Bp,2),"Kw")

Torque=  456.66 Nm
Brake Power= 11.48 Kw

Example 14 Page No:294

In [14]:
#Input data
D=300*10**-3                #steam engine bor
L=400*10**-3                #stroke 
Db=1.5                      #effective brake diameter
W=6.2*10**3                 #net load on the brake
N=180                       #speed of engine in rpm
Pma=6.5*10**3               #mean effective pressure in bar
A=((pi/4)*0.3**2) 
dr=0
S=0

#Calculation
Ip=((2*Pma*L*A*N)/60000)*100 #Indicated power of steam engine in Kw
T=(W-S)*((Db+dr)/2)          #Torque in Nm
Bp=2*pi*N*T/ 60000           #Break power Kw
eta=(Bp/Ip)*100              #Mechanical efficiency in%


#Output
print("Indicated power of steam engine=",round(Ip,2),"Kw")
print("Torque=",T,"Nm")
print("Break power=",round(Bp,2),"Kw")
print("Mechanical efficiency=",round(eta,1),"%")

Indicated power of steam engine= 110.28 Kw
Torque= 4650.0 Nm
Break power= 87.66 Kw
Mechanical efficiency= 79.5 %