1. INTRODUCTION
1.1 History of IC Engines: The machines that produce power or energy are called engines. The engines work as prime movers meaning “producers of motion”. There are other machines which are run by prime movers. Engines have become well known these days because of widespread popularity of automobile – the cars, trucks, buses and motor cycles are machines that are used for transport almost by everybody and everywhere. Doubtless no other engineering wonder can claim such wider use and engines provide the power for automobile. There are of course other uses of these engines also. Engines in general are reciprocating and rotary, the latter are commonly recognized as turbines, though there are some which are not turbine. An engine which was first introduced perhaps used a hot air which expanded on top of a piston. It was steam at high pressure which was then used against the piston which was pushed and moved in a cylinder linearly. The engine piston was connected to a crank through connecting rod caused the crank to rotate about its axis. Thus rotary motion is generated. An engine would definitely need an expanding medium which will push the piston when expanding. The expanding medium will have to be at higher temperature and pressure. The heat required for increasing the temperature and pressure of expanding medium can be given to the medium outside the cylinder in which the piston moves. In such a case the engine is called external combustion engine. The steam engine and hot air engine are examples. Fuel is burnt out of engine and heat is supplied to working fluid which enters the cylinder of the engine with high energy due to temperature and pressure. In internal combustion engine the fuel is burnt in the cylinder in confined space between walls and top of the cylinder. The heat causes the gases, which become