This document provides an overview of internal combustion engine cycles and valve timing. It discusses several air standard cycles including Otto, diesel, dual, and others. It then focuses on the Otto cycle in more detail over multiple pages. The document also covers fuel-air cycles, deviations from ideal cycles, and ends with a discussion of valve timing diagrams. Key points covered include the various air standard cycles, details of the Otto cycle process, comparisons of air-standard and actual cycles, and diagrams showing the opening and closing of intake and exhaust valves through the four strokes of an engine.

1. Dr. Vishal Patil
Associate Professor 1
Sharad Institute of Technology, College of
Engineering, Yadrav- Ichalkarnji
Internal Combustion Engine
Department of Mechanical Engineering
Mr. A. S. Husainy
Assistant Professor
Power Cycles

2. 2
Content
1. Air Standard Cycles
2. Otto Cycle
3. Diesel Cycle
4. Duel Cycle
5. Fuel Air Cycles
6. Deviation of Actual Cycle from Ideal Cycle
7. Valve Timing Diagram

3. 3
1. Air Standard Cycles
Types of cycles
1. Carnot cycle
2. Otto cycle
3. Diesel cycle
4. Stirling cycle
5. Ericsson cycle
6. Dual cycle
7. Lenoir cycle
8. Atkinson cycle
9. Brayton cycle

4. 4
2. Otto Cycle

5. 5
2. Otto Cycle

6. 6
2. Otto Cycle

7. 7
2. Otto Cycle

8. 8
3. Diesel Cycle

9. 9
3. Diesel Cycle

10. 10
3. Diesel Cycle

11. 11
3. Diesel Cycle

12. 12
4. Duel Cycle
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13. 13
5. Fuel Air Cycles
1. Significance
2. Composition of cylinder gases
3. Variable specific heats
4. Dissociation
5. Effect of number of mole
6. Comparison with air standard cycles
7. Effect of operating variables
a. Compression ratio
b. Fuel-Air ratio :-
1. Efficiency
2. Maximum power
3. Maximum temperature
4. Maximum pressure
5. Exhaust temperature
6. Mean effective pressure

14. 14
6. Deviation of Actual Cycle from Ideal Cycle
Major Losses
1. Variation of specific heat with temperature
2. Dissociation of the combustion products
3. Progressive combustion
4. Incomplete combustion of fuel
5. Heat transfer into the walls of the combustion chamber
6. Blow down at the end of exhaust process
7. Gas exchange process

15. 15
6. Deviation of Actual Cycle from Ideal Cycle
Comparison of Air-Standard and Actual Cycle
1. The working substance being a mixture of air and fuel vapour or finely
atomized liquid fuel in air combined with the products of combustion left
from the previous cycle.
2. The change in chemical composition of the working substance.
3. The variation of specific heats with temperature.
4. The progressive combustion rather than the instantaneous combustion.
5. The change in the composition, temperature and actual amount of fresh
charge because of the residual gases.
6. The heat transfer to and from the working medium
7. The substantial exhaust blow down loss
8. Gas leakage and fluid friction.

16. 16
6. Deviation of Actual Cycle from Ideal Cycle
1.Time Loss Factor
2.Heat Loss Factor
3.Exhaust Blow down

17. 17
10. Valve Timing Diagram
Reference: Internal Combustion Engine by Prof. V. Ganesan, 4th
Edition, Mc Graw Hill Education

18. The above diagram represents the valve timing for the ideal Engine. But in reality, the
opening/closing of the valve is not instantaneous as like in the theoretical assumption.
The time taken for the opening of these valves needs to be considered. so the Actual
or practical Valve Timing Diagram will be slightly different than the above theoretical
one. Check this following actual/practical Valve Timing Diagram.
Valve timing
diagram

19. Valve timing diagram for a 4-stroke Petrol engine

20. We know that the four stroke engine has 4 strokes namely
• Suction
• Compression
• Power or expansion (as indicated in diagram)
• Exhaust.
Valve timing diagram shows the opening and closing of inlet
and exhaust valve according to the 4 strokes of engines or
we can simply say according to the two revolution of
crankshaft.
It is clearly shown in the diagram that inlet valve opens 25
degree before TDC ( Top dead center - top edge of the
cylinder) and inlet valve closes after suction stage ends i.e
30 degree after BDC. Similarly fuel injection start and stop
and exhaust valve open and close shown according to the 4
stages of Engine cycle.
Valve timing diagram for a 4-stroke Diesel engine

21. 21
This video is prepared for academic use only.