In combustion engines the inner energy set free by combustion ( e.g. of gasioline or Diesel fuel ) is changed partly into mechanical energy. There are several varieties of combustion engine. The most common is the four-stroke Otto Engine, which was invented by the German merchant and engineer Nikolaus August Ottoin 1876.
The working mechanism of the four-stroke Otto-Cycle: The engine's cylinder has got two valves, the Intake valve I and the Exhaust valve E, which are opened and closed by a mechanism (camshaft - not shown here). A crank moves the piston in the cylinder bymeans of a "connecting rod".
1st stroke (Intake):
The piston sucks in the fuel-air-mixture from the carburetor into the cylinder.
2nd stroke (Compression):
The piston compresses the mixture.
3rd stroke (Combustion):
The spark from the spark plug inflames the mixture. The following explosion presses the piston to the bottom, the gas is operating on the piston.
4th stroke (Exhaust): The piston presses the exhaust out of the cylinder.
