The document discusses different types of internal combustion engines. It describes the four-stroke spark ignition engine, which intakes air and fuel on the first stroke, compresses it on the second, ignites it with a spark plug on the third power stroke, and exhausts on the fourth stroke. The two-stroke engine completes this cycle with only two strokes per revolution using ports instead of valves, providing power every rotation but being less efficient and more polluting. Valve and ignition timing is important for synchronization between engine cycles.

3. CONTENT…
• INTRODUCTION
• ENGINE CLASSIFICATION
• INTERNAL COMBUSTION ENGINE
• SI ENGINE - PROCESS FOR EXECUTION
• SPARK IGNITION ENGINE (WITH VALVE TIMING DIAGRAM)
FOURE STROKE SI ENGINE
TWO STROKE SI ENGINE
• REFERENCES

4. INTRODUCTION
An engine is a machine designed to convert one
form of energy into mechanical energy.
“Engine is also defined as a mechanism or
object that serves as an energy source.”
(Merriam-webster.com)
CHEMICAL ENERGY >>> MECHANICAL ENERGY

5. ENGINE CLASSIFICATION
Figure 1. Engine classification (electrical-knowhow.com)

6. • In an Internal combustion engine, combustion takes
place within working fluid of the engine, thus fluid
gets contaminated with combustion products.
• Petrol engine is an example
of internal combustion engine,
where the working fluid is a
mixture of air and fuel.
INTERNAL COMBUSTION ENGINE

7. Internal combustion engines may be classified as :
(1) Spark Ignition engines.
(2) Compression Ignition engines.
Figure 2. Application of IC Engine (Slideshare.in)

8. SPARK IGNITION ENGINE
The Spark Ignition (SI) engines work on the principle
of cycle of operations invented by Nikolaus A. Otto in
the year 1876.
SI engine is also called the
Otto engine.
In SI engines, the burning of fuel occurs by the spark
generated by the spark plug located in the cylinder
head. The fuel is compressed to high pressures and its
combustion takes place at a constant volume.

9. ESSENTIAL COMPONENTS
Figure 3.

10. E
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P
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11. PROCESSES FOR EXECUTION

12. Figure 4. An animated cut away diagram of a typical fuel injector. Fuel
injectors are used to spray controlled amounts of fuel into an internal
combustion engine (EFI gasoline engine).

15. STAGES OF COMBUSTION
Figure 5. Stages of combustion in SI engine (Ref. mechscience.com)

16. There is mainly four stroke in four stroke SI engine:-
1) Suction stroke
2) Compression stroke
3) Power or Expansion or Working stroke
4) Exhaust stroke
FOUR STROKE SI ENGINE
Figure 6.

17. Four-stroke cycle used in
gasoline/petrol engines.
1 = Intake,
2 = Compression,
3 = Power,
4 = Exhaust.
WORKING OF FOUR STROKE SI ENGINE
Figure 7. Animation of each Four stroke in SI Engine
(https://commons.wikimedia.org/wiki/File:4StrokeEngine_Ortho_3D_Small.gif)

18. BASIC ENGINE TERMINOLOGIES
• Top dead center (TDC)
• Bottom dead center (BDC)
• Piston Stroke (s)
• Stroke volume (Vh)
• Clearance volume (Vc)
• Swept volume/Displacement
volume
• Compression ratio
Figure 8. Basic Engine Terminology

19. VALVE AND IGNITION TIMING
The normal engine completes around 100000 cycles per minute, as there
are number of processes involve in a single cycle of a internal which makes it
necessary to be equipped with an effective system that can enable…
(1) Synchronization between the steps of a cycle of the engine.
(2) Complete seizure of the combustion chamber.
(3) Provide the exit for the combustion residual so that the next
cycle of the engine can take place.
(4) Ideal timing for the opening and closing of the inlet and outlet
valve.
(5) The cleaning of engine cylinder which in turn maintain the
quality of combustion and decreases wear and tear inside the
cylinder.
(6) The study of the details of the combustion that is required for the
modification of the power of the engine.

20. THEORETTICAL VALVE TIMING
DIAGRAM FOR 4 STROKE ENGINE
Figure 9.

21. ACTUAL VALVE TIMING DIAGRAM FOR
4 STROKE ENGINE
Figure 10.

22. • Dedicated lubrication system makes to engine
more wear resistant
• Better efficiency than two (2) stroke engines
• No oil in the fuel - less pollution
Advantages
Drawbacks
• Complicated construction
• Should work in a horizontal position due to
lubrication

23. TWO STROKE SI ENGINE
A two-stroke (or two-cycle) engine is a type of internal
combustion engine which completes a power cycle with two
strokes (up and down movements) of the piston during only
one crankshaft revolution.

24. BASIC PARTS
• Piston
• Piston Ring
• Spark plug
• Connecting rod
• Crankshaft
Figure 11. Basic parts of two stroke engine like,
Piston ring, spark plug and connecting road.

25. WORKING PRINCIPLE
• As the name itself implies, all the processes in the two
stroke (Upstroke and Down-stroke) cycle engine are
completed in two strokes.
• These engine have one power stroke per revolution of the crankshaft.
In the two stroke engine
there is a two opening
called ports (INLET AND
EXHAUST) are provided in
place of valve of four stroke
engines. These ports are
opened and closed by
reciprocating motion of the
piston in the cylinder
Figure 12. Ref. http://engineering.myindialist.com

26. Figure 13. Upstroke and Down stroke of 2 stroke engines
Ref. http://www.automobileandengines.com

27. ACTUALL VALVE TIMING DIAGRAM FOR 2
STROKE ENGINE
Figure 14. Valve Timing diagram
for two stroke engine
(mechanicalbooster.com)

28. Advantages
Drawbacks
• Lack of valves, which simplifies
construction and lower weight
• Fire once at every revolution, which
gives a significant power boost
• Can work in any orientation
• Good power to weight ratio
• Produce uniform torque on crankshaft.
• Lack of a dedicated lubrication system
makes the engine to wear faster.
• Necessity of oil addition into the fuel
• Low efficiency
• Produce a lot of pollution
• It produces high vibration and noisy
operation.

29. REFERENCES
• https://en.wikipedia.org/wiki/Spark-ignition engine
• www.brighthubengineering.com
• https://encyclopedia2.thefreedictionary.com
• Mechanicalbooster.com
• https://www.slideshare.net
• Me-mechanicalengineering.com
• fluid.wme.pwr.wroc.pl/engines/SI_engine_combustion.pdf