An engine is a device which transforms one form of energy into another form with its associated conversion efficiency. Heat engine classification can be done into two types. They are listed below
External combustion engines are those in which combustion takes place outside the machines. Heat produced during external combustion is used for inducing useful mechanical motion in the cylinder of the engine.
Steam Engine, Stirling Engine, Steam Turbine, Closed cycle gas turbine are the types of External Combustion Engines.
Internal combustion engines are those in which combustion takes place within the engine. Chemical energy of the fuel is converted to thermal energy, and thermal energy is converted to mechanical energy, which moves the piston up and down inside the cylinder. Power from the piston is transmitted to the crankshaft which is ultimately transmitted to the wheels via a transmission system. Modern automobiles use internal combustion engines for propulsion.
Gasoline Engine, Diesel Engine, Wankel Engine, Open Cycle Gas Turbine are the types of Internal Combustion Engines.