# Internal Combustion Engines¶

## Example 3.1 , Page 131¶

In [16]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
re=6.0
k=1.4

#calculations
nt=1-1/re**(k-1)
ntt=nt*100  #efficiency

#results
print "Thermal efficiency in percent",round(ntt,3)

Thermal efficiency in percent 51.164


## Example 3.2,Page 132¶

In [1]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
d=3.25 #in
stroke=4.0 #in
v=6.0 #cu in

#calculations
Dp=d**2 *pi*stroke/4
r=(Dp+v)/v #compression ratio

#results
print "Compression ratio ",round(r,3)

Compression ratio  6.531


## Example 3.3,Page 133¶

In [18]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
per=20.0
Dp=100.0

#calculations
r=Dp/per +1

#results
print "Compression ratio ",round(r,3)

Compression ratio  6.0


## Example 3.4,Page 136¶

In [19]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
r=16.0
rc=4.0
k=1.4

#calculations
etat=1-1/r**(k-1) *((rc**k -1)/(k*(rc-1)))
eta=etat*100; #efficiency

#results
print "Thermal efficiency in percent",round(eta,3)
print "The answer is a bit different due to rounding off error in the textbook"

Thermal efficiency in percent 53.154
The answer is a bit different due to rounding off error in the textbook


## Example 3.5,Page 142¶

In [2]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
F=200 #lb
area=1.65 #sq. in
length=3.5 #in

#calculations
ord=area/length
mep=ord*F

#results
print "MEP of an engine in psi",round(mep,3)

MEP of an engine in psi 94.286


## Example 3.6,Page 143¶

In [1]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
Pi=90 #psi
L=5.0/12.0 #ft
r=5.0 #in
x=1.5 #ft
rpm=1500.0 #rpm

#calculations
A=pi*x*x
N=rpm*4/2
Ihp=Pi*L*A*N/33000.0

#results
print "IHP of cylinder ",round(Ihp,3)

IHP of cylinder  24.097


## Example 3.7,Page 144¶

In [22]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
r=4.0 #ft
n=300.0 #rpm
F=60.0 #lb

#calculations
Bhp=2*pi*r*F*n/33000

#results
print "Bhp of the engine ",round(Bhp,3)

Bhp of the engine  13.709


## Example 3.8,Page 147¶

In [23]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
C=1.0/4000.0
F=125.0 #lb
n=3500 #rpm

#calculations
Bhp=F*n*C

#results
print "Bhp of the engine ",round(Bhp,3)

Bhp of the engine  109.375


## Example 3.9,Page 151¶

In [24]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
r=1.75 #ft
F1=72.0 #lb
F2=24.0 #lb
n=500.0 #rpm
m=1.8 #lb
mi=15.0 #min
Qh=20000.0 #Btu/lb

#calculations
Bhp=2*pi*r*F1*n/33000.0
Fhp=2*pi*r*F2*n/33000.0
Ihp=Bhp+Fhp
Fc=m*60/mi
Bsfc=Fc/Bhp
Isfc=Fc/Ihp
etam=Bhp/Ihp *100
etabt=Bhp*2545/(Fc*Qh)
etait=Ihp*2545/(Fc*Qh)

#results
print "Thermal efficiency in percent",round(etam,3)
print " Brake thermal effficiency in percent",round(etabt*100,3)
print " Indicated thermal effficiency in percent",round(etait*100,3)

Thermal efficiency in percent 75.0
Brake thermal effficiency in percent 21.2
Indicated thermal effficiency in percent 28.266


## Example 3.10,Page 191¶

In [3]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
bore=3.0 #in
stroke=4.0 #in
rpm=3000.0 #rpm
air=110.0 #cu ft per min

#calculations
pdv=bore*bore*pi*stroke*2*bore/4
pde=pdv*rpm /2
req=air*1728
eff=req/pde *100; #efficiency

#results
print "Volumetric efficiency in percent",round(eff,3)

Volumetric efficiency in percent 74.697


## Example 3.11, Page 244¶

In [27]:
# Initialization of Variable
from math import pi
from math import atan
from numpy import *
x1=11.5 # CO2
x2=4.1  #CO
x3=0.4  #O2
x4=2.3 # H2
x5=0.2 #CH4
x6=81.5 #N2
yc=0.842 #lb of C
yh=0.158 #lb of H2
basis=1
bhp=100
burn=8.9 #gal/hr
sg=0.731
Qh=20750.0 #Btu/lbm
rate=66.0 #gpm
ex=1100.0 #F
air=70.0 #F
cp=0.254
h2=4330.0 #btu/lb
h4=62000.0 #btu/lb
h5=23700.0 #btu/lb

#calculations
c1=x1*44 #mass CO2
c2=x2*28 #mass CO
c3=x3*32 #mass O2
c4=x4*2 #mass H2
c5=x5*16 #mass CH4
c6=x6*28 #mass N2
summ=c1+c2+c3+c4+c5+c6
carbon=x1*12 + x2*12+x5*12
hydrogen=x4*2+x5*4
lbdrygas=summ/carbon *yc
lbfuel=carbon/yc
lbH=lbfuel*yh
lbH2=lbH-hydrogen
lb3=lbH2*9
lbwater=lb3/lbfuel
lbair=lbdrygas+lbwater-basis
bsfc=burn*sg*8.33/bhp
fuelmin=bsfc*bhp/60
energy=2545/bsfc
per1=energy/Qh #energy supplied
Ec=rate*8.33*10
Eclb=Ec/fuelmin
per2=Eclb/Qh #energy absorbed
dryloss=(ex-air)*cp*lbdrygas
per3=dryloss/Qh #energy lost
hv2=h2*c2/lbfuel
hv4=h4*c4/lbfuel
hv5=h5*c5/lbfuel
hv=hv2+hv4+hv5
per4=hv/Qh #energy supplied
eh2=lbwater*(1066+0.5*ex-air)
per5=eh2/Qh #energy supplied

#results
print "Air supplied per lb of fuel in lb air per lb fuel",round(lbair,3)
print "Percentage of energy supplied utilized in Btu in percent",round(per1*100,3)
print  "Percentage of energy absorbed by coolant in percent",round(per2*100,3)
print "Energy lost in sensible heat in percent",round(per3*100,3)
print "Energy supplied in combustiles in exhaust in percent",round(per4*100,3)
print "Energy supplied in water formed by combustion in percent",round(per5*100,3)
print "Energy supplied unaccounted for in percent",round(per6*100,3)

Air supplied per lb of fuel in lb air per lb fuel 13.189
Percentage of energy supplied utilized in Btu in percent 22.632
Percentage of energy absorbed by coolant in percent 29.334
Energy lost in sensible heat in percent 16.369
Energy supplied in combustiles in exhaust in percent 18.366
Energy supplied in water formed by combustion in percent 8.987
Energy supplied unaccounted for in percent 4.901