IC ENGINE

1. IC Engine

2. Engines : A device that converts energy into mechanical energy or mechanical power.
It can have Reciprocating, Rotary, etc. motion
Air-fuel
Mixture
TDC
BDC
It always have Stator and Moving parts
Engines are broadly classified into:
 IC engines : Combustion takes place inside the engine cylinder.
E.g. Petrol Engine , Diesel Engine, Gas Engine
 External Engines : Combustion takes place outside the engine cylinder
E.g. Steam Engine, Gas Turbines, Steam Turbines
Introduction

3. Applications

4. According to the fuel used
According to thermodynamic cycle
According to method of Ignition
According to number of strokes per cycle
According to number of cylinders
According to cooling system
According to method of fuel injection
According to valve mechanism
According to method of starting
According to Lubrication system
According to field of application
According to arrangement of cylinders
Classification of Engines

5. Stroke = 4 times
• Suction
• Compression
• Expansion
• Exhaust
Air-fuel
Mixture
Suction
Suction Compression
Heat
Addition
Expansion
Heat
Rejection Exhaust
Compression
Heat
Addition Expansion
Heat
Rejection Exhaust
No
Movement
Burn-out
Air-Fuel
mixture
Spark Plug Inlet Port Outlet Port
No
Movement
Air-Fuel
mixture
ignited using
spark Plug
TDC
BDC

6. 0
V2= V3 = Clearance Volume (VC)
V1= V4 = VC+ Vs
V1- V2 = Swept Volume (Vs)
2
4
D
L

 
Compression ration = V1/V2= (VC+ Vs)/(VC)

7. 𝜂 = 1 −
𝑇4 − 𝑇1
𝑇3 − 𝑇2
𝜂 = 1 −
𝑇1
𝑇4
𝑇1
− 1
𝑇2
𝑇3
𝑇2
− 1
Now , air standard efficiency in terms of compression ratio
𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
𝑃1𝑉1
𝛾
= 𝑃2𝑉2
𝛾
𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
1 1 2
2 2 1
V T P
V T P
  1 1 1
2 2 2
V T V
V T V


 
𝑷𝟏𝑽𝟏
𝜸
= 𝑷𝟐𝑽𝟐
𝜸
𝑼𝒔𝒊𝒏𝒈
Process 1-2: Isentropic Compression
Air Standard efficiency

8. 𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
1 1 2
2 2 1
V T P
V T P
  1 1 1
2 2 2
V T V
V T V


 
𝑷𝟏𝑽𝟏
𝜸
= 𝑷𝟐𝑽𝟐
𝜸
𝑼𝒔𝒊𝒏𝒈
1
2 1
1
1 2
T V
T V





1
2 1
1 2
T V
T V
 
 
  
 
1
2
, ( compression ratio )
V
where r
V

1
2 1
T T r 

1
3 4
4 3
Similarly
T V
T V
 
 
  
 
1
3 4
T T r 

4
3
, ( compression ratio )
V
where r
V

Process 3-4: Isentropic Expansion

9. 3
2
1 4
T
T
T T

1
3 4
T T r 

1
2 1
T T r 

3
4
1 2
T
T
T T

4
1
1
3
2
2
1
1
1
T
T
T
T
T
T

 

 
 
 
 

 
 
1
2
1
T
T
  
1
2 1
T T r 

1
1
1
r
 
 
Air Standard efficiency

10. Work-done using in terms of Pressure and
Volume

11. dW PdV vdP
 
dW PdV

using n
PV C

n
C
dW dV
V

f f
n
i i
C
dW dV
V

 
1 1
1
n n
f i
V V
W C
n
 



1
f i
n n
f i
V V
C
V V
W
n
 

 
 
 


1
f i
n n
f i
V V
C C
V V
W
n



1
f
n n i
f f i i
n n
f i
V V
P V PV
V V
W
n



1
f f i i
P V PV
W
n



2 2 1 1 2 2 1 1
1 2 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
4 4 3 3 3 3 4 4
3 4 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
using, n
PV C

Process 1-2: Work on the system Process 3-4: Work by the system

12. Mean effective pressure (MEP) =
𝑵𝒆𝒕 𝑾𝒐𝒓𝒌 𝒅𝒐𝒏𝒆
𝑺𝒘𝒆𝒑𝒕 𝑽𝒐𝒍𝒖𝒎𝒆
2 2 1 1 2 2 1 1
1 2 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
4 4 3 3 3 3 4 4
3 4 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
Process 1-2: Work on the system Process 3-4: Work by the system
Net work done in Otto Cycle
3 3 4 4 2 2 1 1
1 1
net
PV PV PV PV
W
 
 
 
 
Equal to shaded area
1 2
Swept Volume V V
 
2
1 1
1
1
(1 ) (1 )
V
V V
V r
   

14. Diesel Cycle

15. Work Done = Heat Supplied – Heat Rejected
   
3 2 4 1
p v
Work done c T T c T T
   
Air Standard Efficiency ( ) =
supplied
Net Work done
Heat

   
 
3 2 4 1
3 2
p v
p
c T T c T T
c T T

  


 
 
4 1
3 2
1 v
p
c T T
c T T


 

4
1
1
3
2
2
1
1
1
1
T
T
T
T
T
T


 

 
 
 
 

 
 

16. 4
1
1
3
2
2
1
1
1
1
T
T
T
T
T
T


 

 
 
 
 

 
 
Now , air standard efficiency in terms of compression ratio
Process 1-2: Isentropic Compression
𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
𝑃1𝑉1
𝛾
= 𝑃2𝑉2
𝛾
𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
1 1 2
2 2 1
V T P
V T P
  1 1 1
2 2 2
V T V
V T V


 
𝑷𝟏𝑽𝟏
𝜸
= 𝑷𝟐𝑽𝟐
𝜸
𝑼𝒔𝒊𝒏𝒈
Like Otto Cycle

17. 𝑃1𝑉1
𝑇1
=
𝑃2𝑉2
𝑇2
1 1 2
2 2 1
V T P
V T P
  1 1 1
2 2 2
V T V
V T V


 
𝑷𝟏𝑽𝟏
𝜸
= 𝑷𝟐𝑽𝟐
𝜸
𝑼𝒔𝒊𝒏𝒈
1
2 1
1
1 2
T V
T V





1
2 1
1 2
T V
T V
 
 
  
 
1
2
, ( compression ratio )
V
where r
V

1
2 1
T T r 

Like Otto Cycle
1
3 4
4 3
Similarly
T V
T V
 
 
  
 
4
3
, compression ratio
V
where
V

Process 3-4: Isentropic Expansion

18. Due to constant heat addition process an new term
come into existence : cut off ratio
3
2
Cut-off ratio ( )=
V
V

1
3 4
4 3
since
T V
T V
 
 
  
 
1
3
4
3 4
V
T
T V
 
 
  
 
The cut-off ratio is defined as the ratio of the volume at
the end of constant-pressure energy addition process
to the volume at the beginning of the energy addition
process.
1
3
4 2
3 2 4
V
T V
T V V
 
 
 
 
 
1
3
4 2
3 2 1
V
T V
T V V
 
 
 
 
 
3 1
2 2
;
V V
r
V V

 
1
4
3
T
T r



 
  
 

19. 2-3: Constant heating process
3 3
2 2
V T
V T

3
4 4 2
1 3 2 1
T
T T T
T T T T
  
1
1
4
1
T
r
T r






 
  
 
 


4
1
1
3
2
2
1
1
1
1
T
T
T
T
T
T


 

 
 
 
 

 
 
 
1
1
1
1
1 1
1
1
r
r
r






 



 
 
  
 
 
 
 
 
   

 
1
1
1
1
1
1 1
1
1
r
r
r







 




 
  
 
 
   

 
 
1
1
1 1
1
1
r




 


   

 
 
1
1
1 1
1
1
r




 


   

As per Charle’s Law
1
2 1
T T r 

1
4
3
T
T r



 
  
 

20. Work-done using in terms of Pressure and
Volume
V

21. 2 2 1 1 2 2 1 1
1 2 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
4 4 3 3 3 3 4 4
3 4 ( 1)
1 1
PV PV PV PV
W
 

 
   
 
Process 1-2: Work on the system Process 3-4: Work by the system
Like Otto Cycle
Process 2-3: Work by the system
dW PdV vdP
 
dW PdV

using P C

3 3
2 2
dW P dV

   
2 3 3 2
W P V V
  
Mean effective pressure (MEP) =
𝑵𝒆𝒕 𝑾𝒐𝒓𝒌 𝒅𝒐𝒏𝒆
𝑺𝒘𝒆𝒑𝒕 𝑽𝒐𝒍𝒖𝒎𝒆
Net work done in diesel Cycle
  3 3 4 4 2 2 1 1
3 2
1 1
net
PV PV PV PV
W P V V
 
 
   
 
1 2
Swept Volume V V
 
2
1 1
1
1
(1 ) (1 )
V
V V
V r
   