IC ENGINE: COMPONENTS, FUNCTIONS, AND TYPES

It is an engine in which combustion of fuel takes 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 frees to moves inside the cylinder and transmits the pressure force to crank by use of connecting rod), which used to rotate the wheels of a 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.

Advantages of I.C. engine

•  It has overall high efficiency over E.C. engine.
•  These engines are compact and required less space.
•  The initial cost of the I.C. engine is lower than E.C. engine.
•  This engine easily starts in cold because it uses high volatile fuel.

COMPONENTS OF IC ENGINE

1. Cylinder block

The cylinder is the main body of the IC engine. The cylinder is a part in which the intake of fuel, compression of fuel and burning of fuel take place. The main function of the cylinder is to guide the piston. It is in direct contact with the products of combustion so it must be cooled. For cooling of the cylinder, a water jacket (for liquid cooling used in most of the cars) or fin (for air cooling used in most of the bikes) are situated at the outer side of the cylinder. At the upper end of the cylinder, cylinder head and at the bottom end crankcase is bolted. The upper side of the cylinder is consisting of a combustion chamber where fuel burns. To handle all this pressure and temperature generated by the 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.

2. Cylinder head

The top end of the engine cylinder is closed by means of the removable cylinder head. There are two holes or ports at the cylinder head, one for the 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 the cylinder head is to seal the cylinder block and not to permit entry and exit of gases on cover head valve engine. The cylinder head is usually made by cast iron or aluminum. It is made by casting or forging and usually in one piece.

3. Piston

A piston is fitted to each cylinder as a face to receive gas pressure and transmit the thrust to the connecting rod. It is a prime mover in the engine. The main function of the piston is to give a tight seal to the cylinder through the bore and slide freely inside the cylinder. The piston should be light and sufficient strength to handle gas pressure generated by the combustion of fuel. So the piston is made by aluminum alloy and sometimes it is made by cast iron because light alloy piston expands more than cast iron so they need more clearances to the bore.

4. Piston rings

A piston must be a fairly loose fit in the cylinder so it can move freely inside the cylinder. If the piston is a too tight fit, it would expand as it got hot and might stick tight in the cylinder and if it is too lose it would leak the vapor pressure. To provide a good sealing fit and less friction resistance between the piston and cylinder, pistons are equipped with piston rings. These rings are fitted in grooves which have been cut in the piston. They are split at one end so they can expand or slipped over the end of the piston. A small two-stroke engine has two piston rings to provide good sealing but a four-stroke engine has an extra ring which is known as oil ring. Piston rings are made of cast iron of fine grain and high elastic material which is not affected by the working heat. Sometimes it is made by alloy spring steel.

5. Connecting rod

Connecting rod connects the piston to the crankshaft and transmits the motion and thrust of the piston to the crankshaft. It converts the reciprocating motion of the piston into rotary motion of the crankshaft. There are two ends of the connecting rod; one is known as the big end and other as small end. The big end is connected to the crankshaft and the small end is connected to the piston by use of piston pin. The connecting rods are made of nickel, chrome, and chrome vanadium steels. For small engines, the material may be aluminum.

6. Crankshaft

The crankshaft of an internal combustion engine receives the efforts or thrust supplied by the piston to the connecting rod and converts the reciprocating motion of the piston into rotary motion of the crankshaft. The crankshaft mounts in bearing so it can rotate freely. The shape and size of crankshaft depend on the number and arrangement of cylinders. It is usually made by steel forging, but some makers use special types of cast-iron such as spheroidal graphitic or nickel alloy castings which are cheaper to produce and have a good service life.

7. 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 is sometimes called bush is used 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.

8. Crankcase

The main body of the engine at which the cylinder is attached and which contains the crankshaft and crankshaft bearing is called crankcase. It serves as the lubricating system too and sometimes it is called oil sump. All the oil for lubrication is placed in it.

9. Valves

To control the inlet and exhaust of an 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 the 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.

10. Spark plug

It is used in spark ignition engine. The main function of a spark plug is to conduct a high potential from the ignition system into the combustion chamber to ignite the compressed air-fuel mixture. It is fitted on the cylinder head. The spark plug consists of a metal shell having two electrodes which are insulated from each other with an air gap. When high potential current supply to spark plug it jumping from the supply electrode and produces the necessary spark.

11. Injector

The injector is usually used in compression ignition engine. It sprays the fuel into the combustion chamber at the end of the compression stroke. It is fitted on the cylinder head.

12. Manifold

The main function of the manifold is to supply the air-fuel mixture and collects the exhaust gases equally from all cylinder. In an internal combustion engine two manifold are used, one for intake and other for exhaust. They are usually made of aluminum alloy.

13. Camshaft

The 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 the exhaust stroke and closed at the end of the intake stroke. So to regulate its timing, a cam is used which is oval in shape and it exerts a pressure on the valve to open and release to close. It is driven by the timing belt which drives by the crankshaft. It is placed at the top or at the bottom of the cylinder.

14. Gudgeon pin or piston pin

These are hardened steel parallel spindles fitted through the piston bosses and the small end bushes or eyes to allow the connecting rods to swivel. It connects the piston to connecting rod. It is made hollow for lightness.

15. Push-rod

Push-rod is used when the camshaft is situated at the bottom end of the cylinder. It carries the camshaft motion to the valves which are situated at the cylinder head.

16. Flywheel

A flywheel is secured on the crankshaft. The main function of the flywheel is to rotate the shaft during the preparatory stroke. It also makes crankshaft rotation more uniform.