Working Principle of Internal Combustion Engine

 An internal combustion engine  is an engine where the combustion of a fuel occurs with an  air in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. The first commercially successful internal combustion engine was created by Etienne Lenoir around 1859.

A mixture of fuel with correct amount of air is exploded in an engine cylinder
which is closed at one end. As a result of this explosion, heat is released and this heat
causes the pressure of the burning gases to increase. This pressure forces a close fitting
piston to move down the cylinder. The movement of piston is transmitted to a crankshaft
by a connecting rod so that the crankshaft rotates and turns a flywheel connected to it.
Power is taken from the rotating crank shaft to do mechanical work. To obtain
continuous rotation of the crankshaft the explosion has to be repeated continuously.
Before the explosion to take place, the used gases are expelled from the cylinder, fresh
charge of fuel and air are admitted in to the cylinder and the piston moved back to its
starting position. The sequences of events taking place in an engine is called the
working cycle of the engine. The sequence of events taking place inside the engine are
as follows
1. Admission of air or air-fuel mixture inside the engine cylinder ( suction ).
2. Compression of the air or air fuel mixture inside the engine (compression).
3. Injection of fuel in compressed air for ignition of the fuel or ignition of air-fuel mixture by an electric spark using a spark plug to produce thermal power inside the cylinder (power ).
4. Removal of all the burnt gases from the cylinder to receive fresh charge (exhaust).

Charge means admitting fresh air in to the cylinder in the case of compression
ignition engines ( diesel engines ) or admitting a mixture of air and fuel in to the
cylinder in the case of spark ignition engines.