Presentation of Thermodynamics Group leader: M.Bilal Yousaf
Group Member: 1. 2. 3. 4. M. Danish Jahanzaib Afzal M. Bilal Yousaf
M.sanan
Four stroke petrol engine
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
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.
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
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
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.
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
Construction of four stroke petrol engine
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
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
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.
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.
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
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.
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.
Working principle four Stroke Engine Following are the four
strokes 1 Intake/Suction stroke 2 Compression stroke 3 Expansion
stroke 4 Exhaust stroke
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. 2/26/2014
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. 2/26/2014
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. 2/26/2014
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. 2/26/2014
Working principal of four stroke petrol engine
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. 2/26/2014
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. 2/26/2014
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. 2/26/2014
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 engines valve guides and rocker arms.
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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
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
