Internal combustion engine

1. INTERNAL COMBUSTION ENGINE
ABDI SAMAD MOHAMED AWAYS ID: 31
ABDULLAHI OMAR MOHAMOOD ID: 41
LIIBAAN HUSEIN JIMALE ID: 59
An assignment submitted in full filament of the
Requirements for the machine tool course
Faculty of Engineering
Department of electromechanical
Somali national university
December 2019

2. ii
Abstract
The most successful inventions of human includes internal combustion engine (IC Engine)
as top of list. The recent emphasis on fuel economy, pollution control and other automobile
fields like low friction body profile has also stimulated theoretical searches for an automobile.
A small quantity of high energy fuel enclosed in a small chamber, on ignition produces an
enormous amount of energy. This principle is known as internal combustion engine works on the
above principle.
Over past few years there is a great evolution in automobile industry. The various
technologies are coming forward enhancing the performance and efficiencies of internal
combustion engine. The demand for such power generating engines has raised remarkably.

3. iii
List of Contents
Contents pages
Abstract .................................................................................................................................... iii
List of Contents...........................................................................................................................v
List of figures..............................................................................................................................v
1. Introduction .........................................................................................................................1
1.1 History and Development of Engine ..................................................................................2
1.2 Definition of engine...........................................................................................................4
1.3 Definition of heat engine....................................................................................................4
1.4 External combustion and internal combustion engines .......................................................4
1.5 Working principles of engines ...........................................................................................5
1.5.1 Four stroke spark ignition Engine ................................................................................5
1.5.2 Four stroke compression ignition Engine.....................................................................6
1.5.3 Two stroke Engine ......................................................................................................6
1.6 Application of IC Engines..................................................................................................6
2. Literature Review.................................................................................................................7
3. Types of Engines .................................................................................................................9
3.1 According to number of stroke:..........................................................................................9
3.2 According to design of engine:...........................................................................................9
3.3 According to fuel used:....................................................................................................10
3.4 According to method of ignition: .....................................................................................10
3.5 According to number of cylinder: ....................................................................................10
3.6 According to arrangement of cylinder: .............................................................................11
4. Main Parts of IC Engine.....................................................................................................14

4. iv
4.1 Cylinder block .................................................................................................................14
4.2 Cylinder head ..................................................................................................................14
4.3 Piston...............................................................................................................................16
4.4 Piston rings......................................................................................................................17
4.5 Connecting Rod...............................................................................................................19
4.6 Crankshaft .......................................................................................................................20
4.7 Camshaft .........................................................................................................................20
4.8 Engine bearing.................................................................................................................22
4.9 Valves .............................................................................................................................22
4.10 Flywheel........................................................................................................................22
4.11 Exhaust Manifold...........................................................................................................23
4.12 Intake Manifold .............................................................................................................23
5. Conclusion.........................................................................................................................24
References ................................................................................................................................25

5. v
List of figures
Figure3.1: in line engine............................................................................................................11
Figure3.2: horizontally opposed engine .....................................................................................12
Figure3.3: radial engine.............................................................................................................13
Figure3.4: V engine...................................................................................................................13
Figure4.1: cylinder block………………………………………………………………………...14
Figure4.2: cylinder head............................................................................................................15
Figure4.3: piston.......................................................................................................................17
Figure4.4: piston rings...............................................................................................................18
Figure4.5: connecting rod..........................................................................................................19
Figure4.6: crankshaft.................................................................................................................20
Figure4.7: camshaft...................................................................................................................21
Figure4.8: exhaust manifold......................................................................................................23
Figure4.9: intake manifold ........................................................................................................23

6. 1
1. Introduction
It is an engine in which combustion of fuel take place inside the engine. When the fuel
burns inside the engine cylinder, it generates a high temperature and pressure. This high-pressure
force is exerted on the piston (A device which free to moves inside the cylinder and transmit the
pressure force to crank by use of connecting rod), which used to rotate the wheels of vehicle. In
these engines we can use only gases and high volatile fuel like petrol, diesel. These engines are
generally used in automobile industries, generation of electric power etc [1].
Internal combustion engine is an engine in which the chemical energy of the fuel is
released inside the engine and used directly for mechanical work, as opposed to an external
combustion engine in which a separate combustor is used to burn the fuel. The internal
combustion engine was conceived and developed in the late 1800s. It has had a significant
impact on society, and is considered one of the most significant inventions of the last century.
The internal combustion engine has been the foundation for the successful development of
many commercial technologies. The major applications are in the vehicle (automobile and truck),
railroad, marine, aircraft, home use and stationary areas. The vast majority of internal
combustion engines are produced for vehicular applications, requiring a power output on the
order of 102 kW. Next to that internal combustion engines have become the dominant prime
mover technology in several areas.
The components of a reciprocating internal combustion engine, block, piston, valves,
crankshaft and connecting rod have remained basically unchanged since the late 1800s. The main
differences between a modern day engine and one built 100 years ago are the thermal efficiency
and the emission level. For many years, internal combustion engine research was aimed at
improving thermal efficiency and reducing noise and vibration. As a consequence, the thermal
efficiency has increased from about 10% to values as high as 50%. Since 1970, with recognition
of the importance of air quality, there has also been a great deal of work devoted to reducing
emissions from engines. Currently, emission control requirements are one of the major factors in
the design and operation of internal combustion engines.

7. 2
1.1 History and Development of Engine
A brief outline of the history of the internal combustion engine includes the following
highlights:
1680 - Dutch physicist, Christian Huygens designed (but never built) an internal
combustion engine that was to be fueled with gunpowder.
1794: Robert Street built a compression less engine. He was also the first to use liquid fuel
in an internal combustion engine [2].
1807 - Francois Isaac de Rivaz of Switzerland invented an internal combustion engine that
used a mixture of hydrogen and oxygen for fuel. Rivaz designed a car for his engine - the first
internal combustion powered automobile. However, his was a very unsuccessful design.
1824 - English engineer, Samuel Brown adapted an old Newcomen steam engine to burn
gas, and he used it to briefly power a vehicle up Shooter's Hill in London.
1853–1857: Eugenio Barsanti and FeliceMatteucci invented and patented the internal
combustion engine using the free-piston principle in an atmospheric two cycle engine [3] [4].
1858 - Belgian-born engineer, Jean Joseph Étienne Lenoir invented and patented (1860) a
double-acting, electric spark-ignition internal combustion engine fueled by coal gas. In 1863,
Lenoir attached an improved engine (using petroleum and a primitive carburetor) to a three-
wheeled wagon that managed to complete an historic fifty-mile road trip.
1862 - Alphonse Beau de Rochas, a French civil engineer, patented but did not build a
four-stroke engine (French patent #52,593, January 16, 1862).
1864 - Austrian engineer, Siegfried Marcus, built a one-cylinder engine with a crude
carburetor, and attached his engine to a cart for a rocky 500-foot drive. Several years later,
Marcus designed a vehicle that briefly ran at 10 mph that a few historians have considered as the
forerunner of the modern automobile by being the world's first gasoline-powered vehicle

8. 3
1864: Nikolaus Otto, patented in England and other countries his first atmospheric gas
engine. Otto was the first to build and sell this type of compression less engine designed with an
indirect-acting free-piston, whose great efficiency won the support of EugenLangen which at that
time was mainly for small stationary engines fueled by lighting gas[5].
1873 - George Brayton, an American engineer, developed an unsuccessful two-stroke
kerosene engine (it used two external pumping cylinders). However, it was considered the first
safe and practical oil engine.
1876: Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the
compressed charge, four-stroke engine. The German courts, however, did not hold his patent to
cover all in-cylinder compression engines or even the four-stroke cycle, and after this decision,
in-cylinder compression became universal [6].
1883 - French engineer, EdouardDelamare-Debouteville, built a singlecylinder four-stroke
engine that ran on stove gas. It is not certain if he did indeed build a car, however, Delamare-
Debouteville's designs were very advanced for the time - ahead of both Daimler and Benz in
some ways at least on paper.
1885 - Gottlieb Daimler invented what is often recognized as the prototype of the modern
gas engine - with a vertical cylinder, and with gasoline injected through a carburetor (patented in
1887). Daimler first built a two-wheeled vehicle the "Reitwagen" (Riding Carriage) with this
engine and a year later built the world's first four-wheeled motor vehicle.
1886 - On January 29, Karl Benz received the first patent (DRP No. 37435) for a gas-
fueled car. 1889 - Daimler built an improved four-stroke engine with mushroom-shaped valves
and two V-slant cylinders. 1890 - Wilhelm Maybach built the first four-cylinder, four-stroke
engine.
1950s: Development begins by US firms of the Free-piston engine concept which is a crank
less internal combustion engine.

9. 4
1.2 Definition of engine
An engine is a device which transforms one form of energy into another form. However,
while transforming energy from one form to another, the efficiency of conversion plays an
important role. Normally most of the engines convert thermal energy into mechanical work and
therefore they are called heat engines
1.3 Definition of heat engine
Heat engine is a device which transforms the chemical energy of a fuel into thermal energy
and utilizes this thermal energy to perform useful work. Thus thermal energy is converted to
mechanical energy in a heat engine.
Heat engine can be broadly classified into two categories:
I. Internal combustion engine (IC Engines)
II. External combustion engine (EC Engines)
1.4 External combustion and internal combustion engines
External combustion engine are those in which combustion takes place outside the engine
where as Internal combustion engines takes place within the engine. For example in a steam
engine or a steam turbine, the heat generated due to the combustion of fuel is employed to
generate high pressure steam which is used as the working fluid in a reciprocating engine or
turbine.
In case of gasoline or diesel engines the products of combustion generated by the
combustion of fuel and air within the cylinder form the working fluid.

10. 5
1.5 Working principles of engines
If an engine is to work successfully then it has to follow a cycle of operations in a
sequential manner. The sequence is quite rigid and cannot be changed.In the following sections
the working principle of both spark ignition and compression ignition is described.
1.5.1 Four stroke spark ignition Engine
In a four stroke engine the cycle of operations is completed in four strokes of the piston or
two revolutions of the crankshaft. During the four strokes, there are five events to be completed:
suction, compression, combustion, expansion and exhaust. Each stroke consists of 180 degree of
crankshaft rotation and hence the four stroke cycle is completed through 720 degree of
crankshaft rotation. The cycle of operation for ideal four stroke SI engine consists of the
following four strokes: i) Suction or intake stroke ii) compression stroke iii) expansion or
power stroke iv)exhaust stroke
I. Suction or intake stroke: suction stroke starts when the piston is at the top dead centre and
about to move down wards. The inlet valve is open at this time and the exhaust valve is
closed.
II. Compression stroke: the charge taken into the cylinder during the suction stroke is
compressed by the return stroke of the piston. During this stroke both inlet and exhaust
valves are in closed position.
III. Expansion or power stroke: the high pressure of the burnt gases forces the piston towards
the bottom dead centre. Both the valves are in closed position. Of the four strokes only
during this stroke power is produced. Both pressure and temperature decrease during
expansion.
IV. Exhaust stroke: at the end of the expansion stroke the exhaust valve opens and the inlet
valve remains closed. The piston travels from BDC to TDC pushes out the products of
combustion.

11. 6
Each cylinder of a four stroke engine completes the above four operations in two engine
revolutions, one revolution of the crankshaft occurs during the suction and compression strokes
and the second revolutions during the power and exhaust strokes.
1.5.2 Four stroke compression ignition Engine
The four stroke CI engine is similar to the four stroke SI engine but it operates at a much
higher compression ratio. The compression ratio of an SI engine is between 6 and 10 while for a
CI engine is it from 16 to 20.
1.5.3 Two stroke Engine
In two stroke engines the cycle is completed in one revolution of the crankshaft. two
strokes are sufficient to complete the cycle, one for compressing the fresh charge and the other
for expansion or power stroke.
1.6 Application of IC Engines
The most important of IC engines is a transport on land, sea and air. Other applications
include industrial power plants and as prime movers for electric generators.

12. 7
2. Literature Review
Sreenath&Venkatesh (1973) in their analytical work have predicted the oil film thickness
for a four stroke engine at full load and no-load conditions and have compared with the results of
other researchers. The film thickness is predicted by solving Reynold’s equation considering the
“Squeeze film effect” at TDC and BDC where it is more significant. Full flooded lubrication is
assumed for the entire stroke length [7].
Wakuri et al. (1992) developed a model to study IC engine. The instantaneous friction
force of a piston assembly under firing engine conditions was measured by an improved floating
liner method[8].
JaanaTamminena (2006) used a commercial six cylinder, medium speed diesel engine as a
test engine to investigate the oil film thicknesses between the compression rings and the cylinder
liner at different load conditions. The engine speed for all measurements was 900 rev/min [9].
Santhalia and Kumar (2013) studied the effect of compression ring profile on friction force
of internal combustion engine. Three different ring profiles were selected and analyzed of ring
film thickness, the ring twist angles, the friction force and the friction coefficient using Secant
method, for the compression ring. Hydrodynamic lubrication occurs for most part of the stroke
except at the dead center where mixed lubrication regime was found due to reduced film
thickness resulting in increased friction force [10].
P.C. Mishra (2013) has used a four stroke four cylinder engines are modeled for lubrication
performance. The detailed parameters related to engine friction and lubrication is computed
numerically for the 1-3-4-2 engine firing order. To avoid friction and subsequent wear, the liner
surface is textured with cross h pattern and the ring is coated with thermal and wear resistant
coatings [11].

13. 8
P.C. Mishra et al. (2014) the piston compression ring and the theoretical and experimental
works developed to analyze ring liner contact friction. Because of micro conjunction effect the
friction is comparatively less in case of a rough liner 80 % Power Loss is in compression and
power stroke together of total power loss in an engine cycle. Broad literature survey is carried
out in the research area of piston compression ring to know about the simulation and
experimental methods developed to study its performance [12].
AshkanMoosavian et al. (2016) the effects of piston scuffing fault on engine performance
and vibrations are investigated in an internal combustion (IC) engine ran under a specific test
procedure. Three body abrasive wear mechanism was employed to produce piston scuffing fault
it caused the engine performance to reduce significantly [13].

14. 9
3. Types of Engines
There are two major cycles used in internal combustion engines: Otto and Diesel. The Otto
cycle is named after Nikolaus Otto (1832 – 1891) who developed a fourstroke engine in 1876. It
is also called a spark ignition (SI) engine, since a spark is needed to ignite the fuel-air mixture.
The Diesel cycle engine is also called a compression ignition (CI) engine, since the fuel will
auto-ignite when injected into the combustion chamber. The Otto and Diesel cycles operate on
either a four- or twostoke cycle.
I.C. engine is widely used in automobile industries so it is also known as automobile
engine. An automobile engine may be classified in many manners.
3.1 According to number of stroke:
I. Two Stroke Engine: In a two stroke engine a piston moves one time up and down inside
the cylinder and complete one crankshaft revolution during single time of fuel injection.
This type of engine has high torque compare to four stroke engine. These are generally
used in scooters, pumping sets etc.
II. Four Stroke Engine: In a four stroke engine pistons moves two times up and down inside
the cylinder and complete two crankshaft revolutions during single time of fuel burn.
This type of engines has high average compare to two stroke engine. These are generally
used in bikes, cars, truck etc.
3.2 According to design of engine:
I. Reciprocating engine (piston engine): In reciprocating engine the pressure force generate
by combustion of fuel exerted on a piston (A device which free to move in reciprocation
inside the cylinder). The piston starts reciprocating motion (too and fro motion). This
reciprocating motion converts into rotary motion by use of crank shaft. So the crank shaft

15. 10
starts to rotate and make rotate the wheels of the vehicle. These are generally used in all
automobile.
II. Rotary engine (Wankel engine): In rotary engine there is a rotor which frees to rotate.
The pressure force generated by burning of fuel is exerted on this rotor so the rotor
rotates and starts to rotate the wheels of vehicle. This engine is developed by Wankel in
1957. This engine is not used in automobile in present days.
3.3 According to fuel used:
I. Diesel engine: These engines use diesel as the fuel. These are used in trucks, buses, cars
etc.
II. Petrol engine: These engines use petrol as the fuelthese are used in bikes, sport cars,
luxury cars etc.
III. Gas engine: These engines use CNG and LPG as the fuel. These are used in some light
motor vehicles.
3.4 According to method of ignition:
I. Compression ignition engine: In these types of engines, there is no extra equipment to
ignite the fuel. In these engines burning of fuel starts due to temperature rise during
compression of air. So it is known as compression ignition engine.
II. Spark ignition engine: In these types of engines, ignition of fuel start by a spark,
generated inside the cylinder by some extra equipment (Spark Plug). So it is known as
spark ignition engine.
3.5 According to number of cylinder:
I. Single cylinder engine: In this type of engines have only one cylinder and one piston
connected to the crank shaft.

16. 11
II. Multi cylinder engine: In this type of engines have more than one cylinder and piston
connected to the crank shaft.
3.6 According to arrangement of cylinder:
I. In Line engine:
In this type of engines, cylinders are positioned in a straight line one behind the other along
the length of the crankshaft. The inline-four engine or straight-four engine is an internal
combustion engine with all four cylinders mounted in a straight line, or plane along the
crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane
with all the pistons driving a common crankshaft. Where it is inclined, it is sometimes called a
slant-four.
Figure3.1: in line engine
II. Horizontally opposed:
A horizontally opposed engine is an engine in which the two cylinder heads are on opposite
side of the crankshaft, resulting in a flat profile. Subaru and Porsche are two automakers that use
horizontally opposed engine in their vehicles. Horizontally opposed engines offer a low centre of
gravity and thereby may a drive configuration with better stability and control. They are also
wider than other engine configurations, presenting complications with the fitment of the engine
within the engine bay of a front-engine car.

17. 12
This kind of engine is wide spread in the aircraft production. Typically, the layout has
cylinders arranged in two banks on the either side of the single crankshaft and is generally
known as boxer.
Boxers got their name because each pair of piston moves simultaneously in and out, rather
than alternately, like boxers showing they are ready by clashing their gloved fists against each
other before a fight.
Boxer engines of up to eight cylinders have proved highly successful in automobiles and up
to six in motorcycles and continue to be popular for the light aircrafts engine.
Figure3.2: horizontally opposed engine
III. Radial Engine:
The radial engine is a reciprocating type internal combustion engine configuration in which
the cylinders point outward from a central crankshaft like the spokes on a wheel. This
configuration was very commonly used in large aircraft engines before most large aircraft started
using turbine engines. The connecting rods of pistons are connected to a master rod which, in
turn, connected to the crankshaft.
In a radial engine, the pistons are connected to the crankshaft with a master-and
articulating-rod assembly. One piston has a master rod with a direct attachment to the crankshaft.
The remaining pistons pin their connecting rods` attachment to rings around the edge of the
master rod. Four-stroke radials always have an odd number cylinders per row, so that a
consistent every-other-piston firing order can be maintained, providing smooth operation.
This achieved by the engine talking two revolution of the crankshaft to complete the four
stokes (intake, compression, power, exhaust), which means the firing order is 1,3,5,2,4 and back

18. 13
to cylinder 1 again. This means that there is always a two-piston gap between the piston on its
power stroke and the next piston on fire (piston compression).If an even number of cylinders was
uses, the firing order would be something similar to 1,3,5,2,4,6 which leaves a three piston gap
between firing piston on the first crank shaft revolution and only one piston gap on the second.
This leads to an uneven firing order within the engine, and is not ideal.
Figure3.3: radial engine
IV. V engine
V engine or Vee engine is a common configuration for an internal combustion engine. The
cylinders and pistons are aligned in two separate planes or “banks”, is that they appear to be in a
“V” when viewed along the axis of the crankshaft. The Vee configuration generally reduces the
overall engine length, height and weight compared to the equivalent inline configuration.
Various cylinder bank angles of Vee are used in different engines depending on the number of
the cylinders; there may be angles that work better than others for stability. Very narrow angles
of V combine some of the advantages of the straight and V engine. The most common of V
engines is V6. It is an engine with six cylinders mounted on the crankcase in two banks of three
cylinders, usually set at either a right angle or an accurate angle to each other, with all six pistons
driving a common crankshaft.
Figure3.4: V engine

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4. Main Parts of IC Engine
4.1 Cylinder block
Cylinder is the main body of IC engine. Cylinder is a part in which the intake of fuel,
compression of fuel and burning of fuel take place. The main function of cylinder is to guide the
piston. It is in direct contact with the products of combustion so it must be cooled. For cooling of
cylinder, a water jacket (for liquid cooling used in most of cars) or fin (for air cooling used in
most of bikes) are situated at the outer side of cylinder. At the upper end of cylinder, cylinder
head and at the bottom end crank case is bolted. The upper side of cylinder consist a combustion
chamber where fuel burns. To handle all this pressure and temperature generated by combustion
of fuel, cylinder material should have high compressive strength. So it is made by high grade cast
iron. It is made by casting and usually cast in one piece.
Figure4.1: cylinder block
4.2 Cylinder head
The top end of the engine cylinder is closed by means of removable cylinder head. There
are two holes or ports at the cylinder head, one for intake of fuel and other for exhaust. Both the
intake and exhaust ports are closed by the two valves known as inlet and exhaust valve. The inlet
valve, exhaust valve, spark plug, injector etc. are bolted on the cylinder head. The main function
of cylinder head is to seal the cylinder block and not to permit entry and exit of gases on cover

20. 15
head valve engine. Cylinder head is usually made by cast iron or aluminum. It is made by casting
or forging and usually in one piece.
The cylinder head bolts to the deck of the cylinder block. It covers and encloses the top of
the cylinders. Combustion chambers, small pockets formed in the cylinder heads where
combustion occurs, are located directly over the cylinders. Spark plugs (gasoline engine) or
injectors (diesel engine) protrude through holes into the combustion chambers. Intake and
exhaust ports are cast into the cylinder head. The intake ports route air (diesel engine) or air and
fuel (gasoline engine) into the combustion chambers. The exhaust port routes burned gases out of
the combustion chamber.
Figure4.2: cylinder head
Valve guides are small holes machined through the cylinder head for the valves. The valves
fit into and slide in these guides. Valve seats are round, machined surfaces in the combustion
chamber port openings. When a valve is closed, it seals against the valve seat.
The cylinder head is built to conform to the arrangement of the valves: L-head, I-head, or
others. Cylinder heads on liquid-cooled engines have been made almost exclusively from cast
iron until recent years. Because weight has become an important consideration, a large
percentage of cylinder heads now are being made from aluminum.
The cylinder heads are sealed to the cylinder block to prevent gases from escaping. This is
accomplished on liquid-cooled engines by the use of a head gasket. In an aircooled engine,
cylinder heads are sealed to the tops of the cylinders by soft metal rings. The lubrication system
feeds oil to the heads through the pushrods.

21. 16
4.3 Piston
Piston is one of the main parts in the engine. Its purpose is to transfer force from expanding
gas in the cylinder to the crankshaft via a connecting rod. Since the piston is the main
reciprocating part of an engine, its movement creates an imbalance. This imbalance generally
manifests itself as a vibration, which causes the engine to be perceivably harsh.
The friction between the walls of the cylinder and the piston rings eventually results in
wear, reducing the effective life of the mechanism. The sound generated by a reciprocating
engine can be intolerable and as a result, many reciprocating engines rely on heavy noise
suppression equipment to diminish droning and loudness.
To transmit the energy of the piston to the crank, the piston is connected to a connecting
rod which is in turn connected to the crank because the linear movement of the piston must be
converted to a rotational movement of the crank mechanical loss is experienced as a
consequence. Overall, this leads to a decrease in the overall efficiency of the combustion
process. The motion of the crank shaft is not smooth, since energy supplied by the piston is not
continuous and it is impulsive in nature. To address this, manufacturers fit heavy flywheels
which supply constant inertia to the crank.
Balance shafts are also fitted to some engines, and diminish the instability generated by the
pistons movement. To supply the fuel and remove the exhaust fumes from the cylinder there is a
need for valves and camshafts. During opening and closing of the valves, mechanical noise and
vibrations may be encountered.
Pistons are commonly made of a cast aluminum alloy for excellent and lightweight thermal
conductivity. Thermal conductivity is the ability of a material to conduct and transfer heat.
Aluminum expands when heated and proper clearance must be provided to maintain free piston
movement in the cylinder bore. Insufficient clearance can cause the piston to seize in the
cylinder. Excessive clearance can cause a loss of compression and an increase in piston noise.

22. 17
Piston features include the piston head, piston pin bore, piston pin, skirt, ring grooves, ring
lands, and piston rings. The piston head is the top surface (closest to the cylinder head) of the
piston which is subjected to tremendous forces and heat during normal engine operation.
As the piston moves from the top of the cylinder to the bottom (or vice versa), it accelerates
from a stop to a speed approximately 60 mph at midpoint, and then decelerates to a stop again. It
does this approximately 80 times per second.
The structural components of the pistons are the head, skirt, ring grooves, and lands
however all pistons do not look like the typical one shown here. Some have differently shaped
heads.
Figure4.3: piston
4.4 Piston rings
A ring groove is a recessed area located around the perimeter of the piston that is used to
retain a piston ring. Ring lands are the two parallel surfaces of the ring groove which function as
the sealing surface for the piston ring. A piston ring is an expandable split ring used to provide a
seal between the piston and the cylinder wall. Piston rings are commonly made from cast iron.
Cast iron retains the integrity of its original shape under heat, load, and other dynamic forces.
Piston rings seal the combustion chamber, conduct heat from the piston to the cylinder wall, and
return oil to the crankcase. Piston ring size and configuration vary depending on engine design
and cylinder material.

23. 18
Piston rings commonly used on small engines include the compression ring, wiper ring, and
oil ring.
A compression ring is the piston ring located in the ring groove closest to the piston head.
The compression ring seals the combustion chamber from any leakage during the combustion
process. When the air-fuel mixture is ignited, pressure from combustion gases is applied to the
piston head, forcing the piston toward the crankshaft.
The pressurized gases travel through the gap between the cylinder wall and the piston and
into the piston ring groove. Combustion gas pressure forces the piston ring against the cylinder
wall to form a seal. Pressure applied to the piston ring is approximately proportional to the
combustion gas pressure.
A wiper ring is the piston ring with a tapered face located in the ring groove between the
compression ring and the oil ring. The wiper ring is used to further seal the combustion chamber
and to wipe the cylinder wall clean of excess oil. Combustion gases that pass by the compression
ring are stopped by the wiper ring.
An oil ring is the piston ring located in the ring groove closest to the crankcase. The oil ring
is used to wipe excess oil from the cylinder wall during piston movement. Excess oil is returned
through ring openings to the oil reservoir in the engine block. Two-stroke cycle engines do not
require oil rings because lubrication is supplied by mixing oil in the gasoline, and an oil reservoir
is not required.
Figure4.4: piston rings

24. 19
4.5 Connecting Rod
The connecting rod is a major link inside of a combustion engine. It connects the piston to
the crankshaft and is responsible for transferring power from the piston to the crankshaft and
sending it to the transmission. There are different types of materials and production methods
used in the creation of connecting rods. The most common types of connecting rods are steel and
aluminum. The most common type of manufacturing processes are casting, forging and
powdered metallurgy.
The connecting rod is the most common cause of catastrophic engine failure. It is under an
enormous amount of load pressure and is often the recipient of special care to ensure that it does
not fail prematurely. The sharp edges are sanded smooth in an attempt to reduce stress risers on
the rod. The connecting rod is also shot-peened, or hardened, to increase its strength against
cracking. In most high-performance applications, the connecting rod is balanced to prevent
unwanted harmonics from creating excessive wear. The most common connecting rod found in
production vehicle engines is a cast rod. This type of rod is created by pouring molten steel into a
mold and then machining the finished product. This type of rod is reliable for lower horse power
producing engines and is the least expensive to manufacture. The cast rod has been used in
nearly every type of engine, from gasoline to diesel, with great success.
Figure4.5: connecting rod

25. 20
4.6 Crankshaft
The crankshaft is the part of an engine which translates reciprocating linear piston motion
into rotation. To convert the reciprocating motion into rotation, the crankshaft has crankpins,
additional bearing surfaces whose axis is offset from that of the crank, to which the “big ends” of
the connecting rod from each cylinder attach. It typically connects to a flywheel, to reduce the
pulsation characteristic of the fourstroke cycle, and sometimes a torsion or vibration damper at
the opposite end, to reduce the torsion vibrations often caused along the length of the crankshaft
by the cylinders farthest from the output end acting on the torsion elasticity of the metal.
The engine's crankshaft is made of very heavy cast iron in most cases and solid steel in
very high-performance engines. The crankshaft's snout must be made very strong to withstand
the stress of placing the crankshaft pulley and the stress created from driving all of the
components off of that single pulley.
Figure4.6: crankshaft
4.7 Camshaft
Camshaft is used in IC engine to control the opening and closing of valves at proper timing.
For proper engine output inlet valve should open at the end of exhaust stroke and closed at the
end of intake stroke. So to regulate its timing, a cam is use which is oval in shape and it exerts a
pressure on the valve to open and release to close. It is drive by the timing belt which drives by
crankshaft. It is placed at the top or at the bottom of cylinder.

26. 21
Camshaft is frequently called “brain” of the engine. This is so because its job is to open and
closed at just the right time during engine rotation, so that the maximum power and efficient
cleanout of exhaust to be obtained. The camshaft drives the distributor to electrically synchronize
spark ignition. Camshafts do their work through eccentric "lobes" that actuate the components of
the valve train. The camshaft itself is forged from one piece of steel, on which the lobes are
ground. On single-camshaft engines there are twice as many lobes as there are cylinders, plus a
lobe for fuel pump actuation and a drive gear for the distributor.
Driving the camshaft is the crankshaft, usually through a set of gears or a chain or belt. The
camshaft always rotates at half of crank rpm, taking two full rotations of the crankshaft to
complete one rotation of the cam, to complete a four-stroke cycle. The camshaft operates the
lifters (also called tappets or cam followers) that in turn operate the rest of the valve train. On
"overhead valve" engines the lifters move pushrods that move rocker arms that move valve
stems. Lifters can be of several types. The most common are hydraulic, mechanical and roller
lifters. Hydraulic lifters fill with oil that acts as a shock absorber to eliminate clearance in the
valve train. They are quiet and don't require periodic adjustment. Mechanical lifters are solid
metal and require scheduled adjustment for proper valve clearance. These are used in high-rpm
applications. Roller lifters use a roller device at one end and can be hydraulic or mechanical.
They are used in applications where a very fast rate of valve lift is required.
Figure4.7: camshaft

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4.8 Engine bearing
Everywhere there is rotary action in the engine, bearings are needed. Bearings are used to
support the moving parts. The crankshaft is supported by bearing. The connecting rod big end is
attached to the crank pin on the crank of the crankshaft by a bearing. A piston pin at the small
end is used to attach the rod to the piston is also rides in bearings.
The main function of bearings is to reduce friction between these moving parts. In an IC
engine sliding and rolling types of bearing used. The sliding type bearing which are sometime
called bush is use to attach the connecting rod to the piston and crankshaft. They are split in
order to permit their assembly into the engine. The rolling and ball bearing is used to support
crankshaft so it can rotate freely. The typical bearing half is made of steel or bronze back to
which a lining of relatively soft bearing material is applied.
4.9 Valves
To control the inlet and exhaust of internal combustion engine, valves are used. The
number of valves in an engine depends on the number of cylinders. Two valves are used for each
cylinder one for inlet of air-fuel mixture inside the cylinder and other for exhaust of combustion
gases. The valves are fitted in the port at the cylinder head by use of strong spring. This spring
keep them closed. Both valves usually open inwards.
4.10 Flywheel
A flywheel is secured on the crankshaft. The main function of flywheel is to rotate the shaft
during preparatory stroke. It also makes crankshaft rotation more uniform.

28. 23
4.11 Exhaust Manifold
The exhaust manifold connects all of the engine cylinders to the rest of the exhaust system.
On L-head engines, the exhaust manifold bolts to the side of the engine block, whereas on
overhead-valve engines, it bolts to the side of the cylinder head. It is made of cast iron,
lightweight aluminum, or stainless steel tubing. If the exhaust manifold is made properly, it can
create a scavenging action that causes all of the cylinders to help each other get rid of the gases.
Back pressure (the force that the pistons must exert to push out the exhaust gases) can be reduced
by making the manifold with smooth walls and without sharp bends. Exhaust manifolds on
vehicles today are constantly changing in design to allow the use of various types of emission
controls. Each of these factors is taken into consideration when the exhaust manifold is designed
the best possible manifold is manufactured to fit into the confines of the engine compartment.
Figure4.8: exhaust manifold
4.12 Intake Manifold
The intake manifold can be made of cast iron, aluminum, or plastic. On a gasoline engine it
carries the air-fuel mixture from the carburetor and distributes it to the cylinders. On a diesel
engine, the manifold carries only air into the cylinders. The gasoline engine intake manifold is
designed with the following functions in mind: Deliver the air-fuel mixture to the cylinders in
equal quantities and proportions. This is important for smooth engine performance. The lengths
of the passages should be as equal as possible to distribute the air-fuel mixture equally.
Figure4.9: intake manifold

29. 24
5. Conclusion
Internal Combustion engine is one of the most important inventions of the last century. It
has been developed in the late 1800s and from there on it has had a significant impact on our
society. It has been and will remain for foreseeable future a vital and active area of engineer
research.
Internal combustion engines are among the most important engineering applications. The
theory of application either depends on diesel or Otto cycles. They are categorized either to the
according to the operating cycle, or due to mechanism of working.
Each type of engines has some advantages over the other one. Thus the selection of
appropriate engine requires determining the conditions of applications. Internal combustion
engine with its latest and advanced technology will keep powering vehicles for the foreseeable
future.

30. 25
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