THERMODYNAMICS - MODULE 10

1. Internal Combustion
Engine Cycle
• The OTTO CYCLE
• The DIESEL CYCLE
• The DUAL CYCLE

2. INTERNAL
COMBUSTION
ENGINE
By. Engr. Yuri G. Melliza

3. Internal Combustion Engine
Cycle
Air Standard Cycle
 Otto Cycle
 Diesel Cycle
 Dual Cycle

4. Otto Cycle
Inventor: Nikolaus Otto (1832 – 1891)
Processes:
1 to 2: Isentropic Compression (S = C)
2 to 3: Constant Volume Heat Addition
(V = C)
3 to 4: Isentropic Expansion (S = C)
4 to 1: Constant volume Heat Rejection
(V = C)

5. P V Diagram
P
V
1
4
3
2
S = C
S = C
VD
CVD

6. T S Diagram
T
S
1
4
3
2
V = C
V = C
QR
QA

7. Compression Ratio
Heat Added (V = C)

8. Heat Rejected (V = C)
Net Work

9. Thermal Efficiency
100%
x
Q
Q
-
1
e
100%
x
Q
Q
-
Q
e
100%
x
Q
W
e
A
R
A
R
A
A
















10. 100%
x
(r)
1
-
1
e
100%
x
T
T
T
T
e
1
-
k



















2
3
1
4
1
Percent Clearance
100%
x
lume
Vo
nt
Displaceme
TDC
at
Volume
C 

11. C
C
r
CV
V
100%
x
V
V
C
D
2
D
2




1
KPa
V
W
P
D
m 
Mean Effective Pressure
W VD Pm
KJ m3 Kpa
KJ/kg m3/kg Kpa
KW m3/se
c
KPa
kg
m
V
m
V
V
V
3
D
3
D
)
(
)
(
2
1
2
1







12. Diesel Cycle
Inventor: Rudolf Christian Karl Diesel
(1858-1913)
Processes:
1 to 2: Isentropic compression (S = C)
2 to 3: Constant Pressure Heat Addition
(P = C)
3 to 4: Isentropic Expansion (S = C)
4 to 1: Constant Volume Heat Rejection
(V = C)

13. P V Diagram
P
V
1
4
3
2
S = C
S = C
VD
CVD

14. T S Diagram
T
S
1
4
3
2
V = C
P = C
QR
QA

15. Compression Ratio
Cut-Off Ratio

16. Heat Added (P = C)
Heat Rejected (V = C)

17. Net Work

18. Thermal Efficiency
100%
x
Q
Q
-
1
e
100%
x
Q
Q
-
Q
e
100%
x
Q
W
e
A
R
A
R
A
A
















19. 100%
x
r
k
r
r
1
-
1
e
100%
x
T
T
k
T
T
e
c
k
c
1
-
k





























1
1
1
2
3
1
4
(
)
(
)
(
Percent Clearance
100%
x
lume
Vo
nt
Displaceme
TDC
at
Volume
C 

20. C
C
r
CV
V
100%
x
V
V
C
D
2
D
2




1
KPa
V
W
P
D
m 
Mean Effective Pressure
W VD Pm
KJ m3 Kpa
KJ/kg m3/kg Kpa
KW m3/se
c
KPa
kg
m
V
m
V
V
V
3
D
3
D
)
(
)
(
2
1
2
1







21. Dual Cycle
Processes:
1 to 2: Isentropic compression (S = C)
2 to 3: Constant Volume Heat Addition
QA1(V = C)
3 to 4: Constant Pressure Heat addition
QA2(P = C)
4 to 5: Isentropic Expansion (S = C)
5 to 1: Constant Volume Heat Rejection
(V = C)

22. PV Diagram
P
V
1
3
2
5
S = C
S = C
4

23. TS Diagram
T
S
5
3
2
4
1
V = C
P = C
QA1
QA2
QR

24. Cut-Off Ratio
Compression Ratio
Pressure Ratio

25. Heat Added

26. Net Work
Heat Rejected

27. Thermal Efficiency
100%
x
Q
Q
-
1
e
100%
x
Q
Q
-
Q
e
100%
x
Q
W
e
A
R
A
R
A
A
















28. 100%
x
r
kr
r
r
r
r
1
-
1
e
100%
x
T
T
k
T
T
T
T
e
c
p
p
k
c
p
1
-
k 
































)
(
)
(
)
(
)
(
)
(
1
1
1
1
3
4
2
3
1
5
Percent Clearance
100%
x
lume
Vo
nt
Displaceme
TDC
at
Volume
C 

29. C
C
r
CV
V
100%
x
V
V
C
D
2
D
2




1
W VD Pm
KJ m3 Kpa
KJ/kg m3/kg Kpa
KW m3/se
c
KPa
KPa
V
W
P
D
m 
Mean Effective Pressure
kg
m
V
m
V
V
V
3
D
3
D
)
(
)
(
2
1
2
1





