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1. PRESENTATION OF
COMMUNICATION SKILLS

2. Presentation of Thermodynamics
Group leader:
M.Bilal Yousaf
Group Member:
1.
2.
3.
4.
M. Danish
Jahanzaib Afzal
M. Bilal Yousaf
M.sanan

3. Four stroke petrol engine

4. Four stroke petrol engine
Contents:
1.
Introduction of four stroke petrol engine
2.
Construction of four stroke petrol engine
3.
Working of four stroke petrol engine
4.
Applicatio,lubricationof four stroke petrol engine

5. Introduction of four stroke petrol engine
 Engine:
An engine is motor which
converts chemical energy
into mechanical energy
 Fuel/petrol engine:
A petrol engine (known as
a gasoline engine in North
America) is an internal
combustion
engine with sparkignition, designed to run on
petrol (gasoline) and similar
volatile fuels.

6. Introduction of four stroke petrol engine
 Four stroke engine:
A four-stroke
engine (also known as fourcycle) is an internal
combustion engine in
which
the piston completes four
separate strokes which
comprise a single
thermodynamic cycle. A
stroke refers to the full
travel of the piston along
the cylinder, in either
direction

7. Introduction of four stroke petrol engine
Invention:
Inventor:
Nikolaus Otto Four-stroke engine, Inventor
Nikolaus August Otto was the German inventor of the first
internal-combustion engine to efficiently burn fuel directly in a
piston chamber.
It was invented in 1876 in Germany by German
inventor Nikolaus August Otto. In most petrol engines, the fuel and
air are usually pre-mixed before compression . The pre-mixing was
formerly done in a carburetor, but now it is done by electronically
controlled fuel injection, except in small engines where the
cost/complication of electronics does not justify the added engine
efficiency. it consist of 4 stroke, one cycle complete in 4 stroke of
piston and two revolution of crank shaft

8. Introduction of four stroke petrol engine
Four stroke petrol engine:
The cycle of operation in a
four stroke petrol engine is
completed in two revolutions of
crank shaft or four strokes of
piston. Stroke is defined as the
distance traveled by the piston
from one of the dead centers to
the other dead centre. It is also
equal to two times the crank
radius. Hence in a four stroke
engine work is obtained only
during one stroke out of the four
strokes of the piston required to
complete one cycle. This engine
works on Otto or constant
volume cycle.

9. Introduction of four stroke petrol engine
Four stroke petrol engine:
 Working cycle Otto Cycle
 Fuel used Petrol
 Fuel Supply Carburetor
 Ignition Spark plug is required
 Vibration & noise Less
 Field of application Light duty work

10. Construction of four stroke petrol engine

11. Construction of four stroke petrol engine
Various parts of four stroke petrol engine:










Inlet valve & exhaust valve
Piston
Piston ring
cylinder
Connecting rod
Crank shaft
Crank pin
Crank case
Spark plug
carborator

12. Various parts of four stroke petrol engine
Inlet valve & exhaust valve
 Inlet valve:
its function is to intake
the fresh air-fuel mixture
into the cylinder
 Exhaust valve:
its function is to exhaust
is the burnt gases by the
force of piston

13. Various parts of four stroke petrol engine
Piston:
Piston is a connected to
the crankshaft through the
connecting rod when
piston moves downward
sucks fresh air and fuel
mixture in suction stroke
and ignited inside the
cylinder due to the high
temperature and pressure
generated thus the expand
force down the piston.

14. Various parts of four stroke petrol engine
Piston ring:
A piston ring is
an open ended ring that
fits into a grove or a
groove our outer
diameter of the cylinder.
Piston ring have three
major functions which
are seal the expansion
chamber support heat
transfer and finally
regulate the engine oil
consumption.

15. Various parts of four stroke petrol engine
Connecting rod:
 A small end of connecting
rod is connecting to the
piston and other end is
connecting to the
crankshaft. Its function is
to transmit reciprocating
motion of piston to the
rotary motion of
crankshaft .gudgeon pin is
used to connect the piston
and connecting rod

16. Various parts of four stroke petrol engine
Crank pin:
Crank case
 In a reciprocating engine,
 In an internal combustion
the crankpins, also known
as crank journals are
the journals of the big
end bearings, at the ends
of theconnecting rods
opposite to the pistons.
engine of the reciprocating
type, the crankcase is the
housing for the crankshaft.

17. Various parts of four stroke petrol engine
Carborator:
Spark plug:
 is a device that
 Is used in petrol engine
blends air and fuel for
an internal combustion
engine.
only which is help to ignite
the air-fuel mixture for
combustion.

18. Working principle four Stroke Engine
Following are the four strokes
1 – Intake/Suction stroke
2 – Compression stroke
3 – Expansion stroke
4 – Exhaust stroke

19. 1 – Intake stroke
In suction stroke piston starts at
Top Dead Center (TDC) of the
cylinder and moves to the Bottom
Dead Center (BDC).
Outlet valve will be closed
and inlet valve will be open to
allowing the fresh charge of mixed
fuel & air into the cylinder.
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20. 2 – Compression stroke
In compression stroke,Once
piston reaches BDC & moves back
TDC,inlet valve will be closed,As
the piston moves towards TDC,It
compress air fuel mixture inside
the cylinder & compression takes
place,Hence it is called
compression stroke.
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21. 3 – Expansion stroke
In expansion stroke,Both the
valves are closed,When piston
reaches top of its stroke the fuel
mixture is ignited by spark plug
due to spark high temperature &
pressure generated inside the
cylinder & push down the piston
to BDC,Hence it is known as
expansion stroke.
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22. 4 – Exhaust stroke
In this stroke exhaust valve is
opened,when piston reaches to
BDC & moves to upward.
Piston pushes out the burnt gases
to the atmosphere through the
exhaust valve. Hence called
exhaust stroke & the engine is
ready to begin the cycle again.
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23. Working principal of four stroke petrol engine

24. Applications of Four stroke engine:-
The four stroke version is generally used for larger applications
and is the most common type of engine used in automobiles
today.
This type of engine is an ingenious and practical design that
has powered millions of vehicles. It produces a large amount of
power in an efficient and effective manner. It also generally
produces less pollution and lasts longer than a two stroke
engine. The engine was created by Nikolas Otto in the mid
1800s, and in his honor, it's sometimes known as the Otto
Engine. The four main strokes or steps that make up the cycle
are intake, compression, combustion, and exhaust, which is
sometimes called the Otto cycle.
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25. Four-Stroke lubrication
Four-stroke engines are lubricated by oil held in an oil sump. The oil is distributed through
the engine by splash lubrication or a pressurized lubrication pump system; these systems
may be used alone or together.
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26. SPLASH LUBRICATION:Splash lubrication is achieved
by partly submerging the
crankshaft in the oil sump. The
momentum of the rotating
crankshaft splashes oil to other
engine components such as the
cam lobes, wrist pins and
cylinder walls.
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27. PRESSURIZED
LUBRICATION:Pressurized lubrication uses
an oil pump to provide a
pressurized film of lubricant
between moving parts such
as the main bearings, rod
bearings and cam bearings. It
also pumps oil to the engine’s
valve guides and rocker arms.
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28. 2/26/2014

29. 2/26/2014

30. Difference between
4-Stroke Engine & 2-Stroke Engine
4-Stroke Engine
• One cycle completed
in every 2 revolution
of crankshaft
• More moving parts
• More maintenance
• Heavy in weight
• More expensive
2-Stroke Engine
• One cycle completed
in every revolution of
crankshaft
• Less moving parts
• Less maintenance
• Light in weight
• Less expensive

31. Difference between
4-Stroke Engine & 2-Stroke
Engine
4-Stroke Engine
• Produce more
pollution
• Long engine life
• Not required
• Complex design
2-Stroke Engine
• Less pollution
• Short engine life
• Required a mix of oil
to lubricate the
crankshaft
• Simpler design