How Does The Internal Combustion Engine Work?

Internal combustion engine:

Combustion, also known as burning, is the basic chemical process of releasing energy from a fuel and air mixture.Internal-combustion engine, one in which combustion of the fuel takes place in a confined space, converts chemical energy into thermal energy, to produce useful mechanical work. The combustion of air and fuels take place inside the 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 component of the engine which consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the power-train, this motion drives the vehicle’s wheels.. The force is applied typically to pistons, turbine blades or a nozzle. 



Air-fuel mixture in the combustion chamber is ignited, either by a spark plug (in case of SI Engines) or by compression (in case of CI engines). This ignition produces tremendous amount of heat energy and pressure inside the cylinder. This induces reciprocating motion in the piston.Power of the piston is transmitted to a crankshaft which undergoes rotary motion. The rotary motion is ultimately transmitted to the wheels of the vehicle, via a transmission system, to produce propulsion in the vehicle.As the combustion takes place internally inside the cylinder (a part of working fluid circuit) the engine is called internal combustion engine.

There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine. Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

It can be classified into the following types:


According to the basic engine design :-
(a) Reciprocating engine (Use of cylinder piston arrangement), 

(b) Rotary engine (Use of turbine)

According to the type of fuel used :-
(a) Petrol engine, 

(b) diesel engine, 

(c) gas engine (CNG, LPG), 

(d) Alcohol engine (ethanol, methanol etc)

According to the number of strokes per cycle :-
(a) Four stroke and 

(b) Two stroke engine


According to the method of igniting the fuel :-

(a) Spark ignition engine, 

(b) compression ignition engine and 

(c) hot spot ignition engine


According to the working cycle :-

(a) Otto cycle (constant volume cycle) engine, 

(b) diesel cycle (constant pressure cycle) engine, 

(c) dual combustion cycle (semi diesel cycle) engine.


According to the fuel supply and mixture preparation :-

(a) Carburetor type (fuel supplied through the carburetor), 

(b) Injection type (fuel injected into inlet ports or inlet manifold, fuel injected into the cylinder just before ignition).

According to the number of cylinder :-

(a) Single cylinder and 

(b) multi-cylinder engine


 According to Method of cooling :-
(a) Water cooled or 
(b) Air cooled


According to Speed of the engine :-
(a)Slow speed, 
(b)Medium speed and 
(c)High speed engine


According to Cylinder arrangement :-

(a)Vertical, 

(b)Horizontal, 

(c)Inline, 

(d)V-type, 

(e)Radial, 

(f)Opposed cylinder or piston engines.

According to Valve or port design and location :-

(a)Overhead (I head), 

(b)Side valve (L head); 

In two stroke engines: 

(d)Cross scavenging, 

(e)loop scavenging, 

(f)uniflow scavenging.

According to  Method governing :-

(a)Hit and miss governed engines, 

(b)Quantitatively governed engines and 

(c)Qualitatively governed engine.


According to Application :-

(a)Automotive engines for land transport, 

(b)Marine engines for propulsion of ships, 

(c)Aircraft engines for aircraft propulsion, 

(d)Industrial engines, 

(e)Prime movers for electrical generators.