The document discusses different types of internal combustion engines, focusing on spark ignition (SI) engines. It provides details on the 4-stroke and 2-stroke combustion cycles of SI engines. The 4-stroke cycle consists of the suction, compression, power/combustion, and exhaust strokes. The suction stroke involves fresh air being drawn into the cylinder. In the compression stroke, the air-fuel mixture is compressed. The power stroke occurs when combustion pushes the piston. Finally, in the exhaust stroke, spent gases are expelled from the cylinder. A 2-stroke SI engine combines the intake, compression, power, and exhaust functions into two strokes per cycle.

1. SI ENGINE
*(4STROKE AND
2STROKE)*
UNIT 2 : THERMAL ENGINEERING
PPT PRESENTATION
DIV : B
BATCH: B#3

2. PVG’S COE(N)
• Representatives I ) Shivam ii) Himanshu iii)Harsh iv) Viraj
• Assinged by M.D.Madlik

3. CONTENT
IC Engine
Types of Engine
SI Engine
Petrol Engine
Diesel Engine
4 Stroke SI Engine
2 Stroke SI Engine

4. COMPARISM BETN. SI AND CI ENGINE
Spark Ignition Combustion Ignition
Petrol as the fuel for combustion Diesel as the fuel for the combustion
Spark plug for ignition Fuel Injector for ignition
Less efficient More efficient
Lower compression ratio comparitively Higher compression ratio

5. SI 4 STROKES -
4-Strokes Suction Compression
Power
Exhaust

6. SUCTION STROKE
Meaning and definition
of suction stroke : Suction
stroke. The stroke of the
piston of a four-
stroke engine during which
a fresh charge is sucked in
or forced by atmospheric
pressure into the space
vacated by the piston.

7. COMPRESSION STROKE
The compression stroke is
the stroke in an engine in
which the air or air/ fuel
mixture is compressed
before ignition. The intake
valve closes and the piston
starts up on the
compression stroke. During
the compression stroke, the
piston moves up the
cylinder, squeezing the

8. POWER/COMBUSTION STROKE
As the fuel reaches the end of
it’s combustion, the heat released
from combusting hydrocarbons
increases the pressurewhich
causes the gas to push down on
the piston and create the power
output. Exhaust stroke:As the
piston reaches the bottom, the
exhaust valve opens.

9. EXHAUST STROKE
The exhaust stroke begins at Stage 6 as
the piston is pushed towards the
combustion chamber (to the right in the
figure). The intake valve is closed, the
electrical contact is open, and the
exhaust valve is opened by the cam
pushing on the rocker arm. The exhaust
gas is pushed past the valve and exits
the engine.

10. 2 STROKE SI ENGINE

11. ABOUT
• A two-stroke SI engine consists of a cylinder with one end fitted with
a cover for the placement of spark plug and the other fitted with a
sealed crank case which will act as leak-proof pump during operation.
The cylinder is provided with inlet port, transfer port, and exhaust port.