The Internal Combustion Engine
The basics of an Internal Combustion Engine:
To begin comprehending how an internal combustion engine works, one must first understand the principle of combustion. Combustion is an exothermic reaction meaning energy is released. It is this energy that is used for work as in the case of the internal combustion engine. Taking a gasoline engine for example, a hydrocarbon (gasoline) reacts with oxygen to produce carbon dioxide, water and the energy mentioned earlier. Combustion also requires an input of energy to initiate the reaction which is termed the activation energy of the reaction. Consequently, for a conventional internal combustion engine to work properly, it must have air (O2 supply), fuel (hydrocarbon supply) and spark/pressure (energy input or ignition).
The parts responsible for these basic functions are the spark plug, combustion chamber and piston. The combustion chamber has an intake for air and fuel input and an output for exhaust (waste) gases to be released. Lastly, the piston is connected to a crankshaft via a connecting rod in order to translate the vertical motion of the piston into rotational motion.
The 4 stroke/cycle:
Four stroke engines are most commonly found on automobiles and larger motorcycles. The four-stroke name refers to the number of strokes done by the piston to complete the reaction described above and to expel the waste products (CO2 and H2O in an engine which uses hydrocarbons as fuel). The four strokes are intake, compression, combustion and exhaust waste expulsion.
The 2 stroke/cycle:
Two-stroke engines are simpler and are usually used on small lawn equipment and motorcycles. As the name refers, a two-stroke engine goes through two strokes of the piston in order to complete the combustion reaction and waste expulsion. The first stroke expels exhaust gases and draws fuel into the combustion chamber as a result of previous combustion forcing the piston downwards. The second stroke compresses the new fuel mixture in the combustion chamber and brings more fuel into the crankcase in preparation for the next cycle.