Basic IC Engine Components and Nomenclature of a S.l. Engine :
In the spark-ignition engine, a mixture is ignited by an electric spark from a spark plug — the timing of which is very precisely controlled. Almost all gasoline engines are of this type. Diesel engine timing is precisely controlled by the pressure pump and injector. The normal plug distance between the spark plug is 1mm apart, and the voltage is 3000v at normal atmospheric conditions.
A cross
section of a single cylinder S. I. engine with overhead valves is shown in fig.
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Basic Components of IC Engine |
- Cylinder
- Cylinder block and cylinder head
- Piston
- Piston Ring
- Combustion Chamber
- Inlet Manifold
- Exhaust Manifold
- Inlet and exhaust valves
- Spark Plug
- Connecting Rod
- Crankshaft
- Camshaft
- Cams
- Flywheel
- Gudgeon Pin or wrist pin or piston pin
- Engine Bearing
- Governer
- The major components of the engine and their functions are briefly described below:
1. Cylinder: As the name implies it is a
cylindrical vessel. In this vessel the piston makes
reciprocating motion. The varying volume cleated in the cylinder during the engine
operation is filled with the working fluid. This fluid is subjected to
different thermodynamic
processes. The cylinder is supported in the cylinder block. It is made of hard grade C. I. and usually cast in one piece.
2. Cylinder
block and cylinder head: Cylinder block is the main supporting
structure for the
various components. The cylinder of a multicylinder engine are cast as a single unit. It
is called a cylinder block.
Cylinder head : It is mounted on the cylinder
block. The end of the cylinder is closed by
means of a removable cylinder head. This
head usually contains the inlet or
admission valve and exhaust valve. In the case of a water-cooled engine, the
cylinder head and
cylinder block is provided with water jackets or with cooling fins in the case of air
cooling. Gasket is incorporated between the cylinder head and cylinder block.
Number of
bolts or studs are used to held cylinder head tight to the cylinder block. The
bottom portion of the cylinder block is called crank
case. The crank case is a samp for
lubricating oil. The crankcase cover is fixed on the crankcase at the bottom
side of crankcase.
Also Read: IC Engine
The main purpose of the cylinder head is to seal the
working ends of the cylinder. The cylinder head is usually made of C. I. or Aluminum alloy.
3. Piston : It is a cylindrical component. It
is fitted into the cylinder. It forms the moving boundary
of the combustion chamber. It fits perfectly into the cylinder hence it provides
a gas tight space with piston rings and lubricant. It transmits the gas force to the
output shaft via connecting rod. It must (i) give gas tight seal to the
cylinder through bore (ii)
side freely (iii) be light and (iv) be strong. The piston wall known as skirt must be strong
enough to stand up to this side thrust. Pistons
are made of C. I. or Aluminum alloy for lightness.
4. Piston rings : To provide a good seating fit
between the piston and cylinder, pistons are
equipped with piston rings. They are made of C.
I. of fine grain and high elasticity which is not affected by the working
heat. Some rings are of alloy spring steel. They are split at one end. Hence, they
can be expanded and slipped over the end of
the piston and into ring grooves cut in the piston. The rings fit tightly
against the
cylinder wall and against the sides of the ring grooves in the pistons. Four-stroke cycle
engines have an extra ring called the oil rings.
5. Combustion Chamber : The space enclosed in
the upper part of the cylinder, by the
cylinder head and the piston top during the combustion process is known as combustion
chamber. In this part of the cylinder, the combustion of fuel takes place. Hence the
thermal energy is taking place resulting in the building up of pressure.
6. Inlet Manifold : The pipe which connects the
intake system to the inlet valve is called
the inlet manifold. The mixture of
air-fuel or air is drawn into the cylinder through
it.
7. Exhaust Manifold : The pipe which connects
the exhaust system to the exhaust valve of
the engine is exhaust manifold. The
products of combustion escape into the
atmosphere.
8. Inlet and exhaust valves : Valves are of
mushroom shaped puppet valve type. They are
provided either on the cylinder head or on the side of the cylinder for regulating
the inlet or discharge. They are made from special alloy steel.
9. Spark Plug : It is used in S. I. Engine only. It is usually located on the
cylinder head.
10. Connecting Rod : It connects the piston and
the crankshaft. It transmits the gas forces
from the piston to the crankshaft. The two ends of the connecting rod are called as
small end and the big end. Small end is connected to the piston by gudgeon pin while
the big end is connected to the crankshaft by crank pin. The connecting rods are
made of Nickie, chrome, and Chrome
vanadium steels. For small engines the
material may be aluminum.
ll. Crankshaft : It converts the reciprocating
motion of the piston into useful rotary motion of
the output shaft. For a single cylinder engine there are a pair of crank arms and
balance weights. Used static and dynamic balancing of the rotating system. It
is enclosed
in a crankcase.
12. Cam Shaft: The cam shaft and its associated
parts control the opening and closing of the
two valves. The associated parts are push rods, rocker arms, valve springs and
tappets. This shaft also provides the drive to the ignition system. It is
driven by the
crank shaft through timing gears.
13. Cams : They are made as integral parts of
the cam shaft. They will open the valve at the
correct timings. They also keep them open for the necessary duration.
14. Flywheel : The net torque by the crankshaft
during one complete cycle of
operation fluctuates. This will change angular velocity of the shaft. For
achieving a uniform
torque flywheel is used.
15. Gudgeon Pin or wrist pin or piston pin : It
is the pin through the piston bosses and the
small end of the piston is connected to piston via this pin. It is a press- fit.
Because of it the connecting rod swivel.
16. Engine Bearing : The crankshaft is
supported by the bearing. The big end of the connecting
rod is connected with crank-shaft by bearing. The piston pin rides in the bearing.
Bearing will reduce the friction and allow the parts to moves easily. It is lubricated
with oil.
17. Governer : It is a device to regulate
automatically the fluctuations of engine speed due to
changes in load.
Application:
The spark-ignition engine are used in automobiles (motorcycle, Scooters, cars etc.), aircraft, motorboats and also in small engines such as chainsaws, lawn-mowers etc.
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Basic Components of IC Engine and Their Function
Reviewed by Harish
on
September 12, 2020
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