Heat engines are sometimes referred to as being motors. Actually, a motor converts one form of energy into useful work without the intentional production of heat, such as an electric motor.
A device which burns fuel creating heat to perform work is a heat engine. Heat engines can be classified as external combustion, such as steam boiler, or internal combustion (IC). They can further be divided into the spark ignited (SI) engine or the compression ignited engine (CI).
The compression ignited internal combustion engine has two main designs: the four stroke cycle, and the two stroke cycle engine. They are both very common throughout the world because of their high efficiency - compare with other types of heat engines.
The engines convert chemical energy in fuel in to mechanical energy.
A typical oil engine has:
1. Cylinder in which fuel and air are admitted and combustion occurs.
2. Piston, which receives high pressure of expanding hot products of combustion and the piston, is forced to linear motion.
3. Connecting rod, crankshaft linkage to convert reciprocating motion into rotary motion of shaft.
4. Connected Load, mechanical drive or electrical generator.
5. Suitable valves (ports) for control of flow of fuel, air, exhaust gases, fuel injection, and ignition systems.
6. Lubricating system, cooling system
The compression of the fuel/air mixture limits the compression ratio of the engine, if it compresses the air too much; the fuel/air mixture spontaneously ignites and causes knocking. A diesel compresses only air, so the compression ratio can be much higher. The higher the compression ratio, the more power is generated.
Some diesel engines contain a glow plug of some sort. When a diesel engine is cold, the compression process may not raise the air to a high enough temperature to ignite the fuel.
The glow plug is an electrically heated wire (think of the hot wires you see in a toaster) that helps ignite the fuel when the engine is