Basic Components of IC Engine and Their Function

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.

Basic Components of IC Engine

The Main Components of spark ignition engine are as follows:

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.