Sunday 13 January 2019

Internal Combustion (IC) Engine and its Components

In previous blog, we have discussed about IC engine and before jumping to this blog, readers are requested to visit the link given below:
IC Engine

Engine or motor is a device designed to convert one form of energy into mechanical energy. The arrangement of different parts of four stroke spark ignition engine (Petrol engine) and four stroke compression ignition engine (Diesel engine) is shown in the figure below:


                                          Figure: Four Stroke Petrol Engine


                                        Figure: Outline of Diesel Petrol Engine

The purpose of each part is described in short:
1.      Cylinder
The cylinder of IC engine is considered as main body of engine in which piston reciprocates to develop power. It has to withstand very high pressure of about 70 bar and temperature of about 2200o C because there is direct continuous combustion inside the cylinder. So its material should retain strength at high temperatures without any deformation, should be good conductor of heat and should be able to resist to wear and tear due to reciprocating parts. Generally, ordinary cast iron is used but incase of heavy duty engines, alloy steels are used.

2.      Cylinder head
The cylinder seals one end of the cylinder. It houses the inlet, spark plug and exhaust valve through which the mixture of air and fuel is taken and burnt with the help of spark produced by spark plug and burnt gases are exhausted to the atmosphere from exhaust. A copper and asbestos gaskets are provided between the cylinder and cylinder heat to obtain a gas tight joint.

3.      Piston and piston rings
The primary function of piston is to compress the air fuel mixture during compression stroke and to transmit the gas force to the connecting rod and then to the crank during power stroke. Generally, the piston of IC engine are made up of cast iron, cast steel and aluminium alloy. Often piston is considered as heart of the engine.
The piston rings are placed in the circumferential grooves provided on the outer surface of the piston. It gives gastight fitting between piston and cylinder and prevents from the leakage of high pressurized gases. It is made from special grade cast iron which can retains its elastic property at very high temperatures. The upper piston rings are called compression rings and lower piston rings are called the oiling or oil control rings.

4.      Connecting rod
Connecting rod joins piston with crank. It is usually a steel forging of circular, rectangular, I, T, or H section and is highly polished for increased endurance strength. Its small ends forms a hinge and pin joint with piston and its big end is connected to the crank by crank pin. It has a passage for the transfer of lubricants from the big end bearing to small end bearing also known as gudgeon pin.

5.      Crank and crankshaft
The crankshaft is the backbone of the engine. The main function of crankshaft is to take power produced by engine and transmit it to the output shaft. Both crank and crankshafts are steel forged and machined to a smooth finish. Both are held together with the help of key. Crankshaft is supported in the main bearings held by engine block and has a heavy wheel, known as flywheel, to even out the fluctuations of torque. The power required for any useful purpose is taken out from crankshafts only.

6.      Piston pin or Wrist pin
The piston pin provides the bearing for the oscillating small end of the connecting rod.

7.      Inlet valve
This valve is responsible for the injection of air fuel mixture into the cylinder during suction stroke of the engine. It is controlled by cam shaft mounted on top of it.

8.      Exhaust valve
This valve is responsible for the removable of burnt gases from the cylinder after the power stroke. It is also controlled by cam shaft mounted on top of it.

9.      Valve spring
It is used to keep valves closer to each other.

10.  Inlet manifold
It is the path from where air fuel mixture is carried from carburetor to the petrol engine.

11.  Exhaust manifold
It is the passage from which carries the exhaust gases from exhaust valve to the atmosphere.

12.  Cam shaft
The function of cam shaft is to control the motion of intake and exhaust valves through the cams, cams follower, push rods and rocker arm. The cam shaft is driven positively from the crankshaft and is connected with timing chain.

13.  Cam and cam follower
It is made of a required profile to give desired motion to the valves through the followers.


14.  Push rod and rocker arm
Push rod and rocker arm transmits the motion of cam to the valves. These links together are also called valve gear.

15.  Crank case
It is the base which holds the cylinder and the crankshaft. It also serves as the sump for lubricating oil.

16.  Water jacket
It serves as cooling device for the engine operating at high temperatures.

17.  Bed plate
The lower portion of the crank case is also known as the bed plate. For concrete foundations, bed plates are hold the bed bolts.

18.  Flywheel
It is the wheel mounted on the crankshaft which stores the excess energy during the power stroke and returns the energy into the other strokes and maintains a fairly consant output torque on the crankshafts.

19.  Governor
The function of the governor is to regulate the air fuel mixture in case of petrol engine and amount of fuel in case of diesel engine to maintain a constant speed of the engine. It is run by a drive from the crankshaft.

20.  Carburetor
The function of carburetor is to supply the uniform mixture is air and fuel to the cylinder of petrol engine through the intake manifold. The mass of mixture entering the cylinder is controlled by the throttle valve.

21.  Spark plug
The function of spark plug is to ignite the air fuel mixture after completing the compression in the petrol engine. It is generally mounted on the cylinder head. This is not used in diesel engine.

22.  Fuel pump
It forces the fuel at high pressure through the fuel nozzle into the cylinder at the end of compression stroke in diesel engine.



23.  Fuel nozzle
The function of fuel nozzle is to break up the liquid fuel into a fine spray as it enters the cylinder for proper combustion. It is used in diesel engine.

YV Nitesh
13th Jan 2019

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