In this article, we discuss the different components of IC engines and the terminology used in IC engines.
Components of IC Engines
The figure shows the components of IC engines. The main component of this 4-stroke petrol engine are as follows:
- Crank and crankshaft
- Connecting rod
- Spark plug
- Inlet and exhaust valve
- Crank pin & Gudgeon pin
- Cylinder head
- Piston rings
- Suction and exhaust manifold
It is the main body of an I.C. engine in which the piston reciprocates to develop power. It has to withstand very high pressures (up to 75 bar) and temperatures (up to 2400 °C) because the combustion takes place in the cylinder. It may be air-cooled or water-cooled. It is generally made of cast iron or alloy steel.
It is used to compress the charge (air-fuel mixture) during the compression stroke and to transmit the gas force to the connecting rod and then crank during the power stroke.
3. Crank and crankshaft
The crank is an integral part of the crankshaft and the crankshaft is the backbone of the engine, the crankshaft is supported by main bearings and it has a heavy wheel called a flywheel to control the fluctuation of torque.
4. Connecting rod
It is a rod with a circular or rectangular cross-section. Its small end is connected to the piston and the big end is connected to the crank It converts the reciprocating motion of the piston into the rotary motion of the crankshaft.
5. Spark plug
It is used to initiate the spark for the combustion of the air-fuel mixture in petrol engines.
6. Inlet and exhaust valve
The Inlet valve controls the admission of the charge during the suction stroke and the exhaust valve is used for the removal of exhaust gases after doing work on the piston.
7. Crank pin and Gudgeon pin
The crank pin is used to connect the big end of connecting rod to the crank and the gudgeon pin is used to connect the small end of connecting rod to the piston.
8. Cylinder Head
It is used for closing one end of the cylinder. It houses inlet and exhaust valves through which charge is taken inside the cylinder and burned gases are exhausted to the atmosphere from the cylinder.
9. Piston rings
Piston rings are housed in the circumferential grooves provided on the outer surface of the piston. It gives a tight fit between the piston and cylinder hence preventing the leakage of high-pressure gases.
10. Suction and exhaust manifold
The suction manifold is the passage that carries the charge from the carburetor to the engine whereas the exhaust manifold is the Carne passage which carries the exhaust gases from the exhaust valve to the atmosphere.
It is used to supply the uniform air-fuel mixture to the cylinder of a petrol engine through the intake manifold. It is controlled by a throttle valve.
Terminology Used in IC Engines
In addition to the above components of IC engines, certain standard terminology used in IC engines is as follows:
- Top Dead Centre (T.D .C.)
- Bottom Dead Centre (B.D.C.)
- Clearance volume
- Swept volume
- Compression ratio
It is the inside diameter of the cylinder.
It is the maximum distance traveled by the piston in the cylinder in one direction. It is generally twice the radius of the crank.
3. Top Dead Centre (T.D.C)
It is the extreme position of the piston at the top of the cylinder. For horizontal engines, it is called an inner dead center (I.D.C).
4. Bottom dead center (B.D.C)
It is the extreme position of the piston at the bottom of the cylinder. For horizontal engines, it is called the outer dead center (O.D.C).
5. Clearance volume
It is the volume contained in the cylinder above the top of the piston when it is at T.D.C. It is denoted by Vc.
6. Swept volume
It is the volume swept by the piston in moving between TDC and BDC It is denoted by Vs.
7. Compression ratio
It is the ratio of the volume when the piston is at BDC to the volume when the piston is at TDC. It is denoted by r.