Internal combustion engines

A heat engine is a device in which the chemical energy of a fuel is first converted into heat energy , subsequently this heat energy is converted into mechanical energy. heat engines are also called as thermal prime movers.

Types of heat engines:-
(1)External combustion engines
(2)Internal combustion engines

(1)External Combustion engines:-
     In the external combustion engines, the combustion of fuel takes place outside the cylinder in engine.The heat energy of hot products of combustion is used directly as in case of gas turbines to develop mechanical power. this heat energy of hot gases is used to raise the pressure and temperature of another working fluid like steam. This steam is subsequently used in steam engines or steam turbines to develop mechanical power.the main disadvantage is size is large and bulky.

(2)Internal combustion engines:-
    In these engines the combustion of fuel take place in side the engine cylinder. due development of chemical energy pressure is increase also temperature is increase.the hot gases are subsequently expanded to develop the mechanical power and finally the gases are rejected back to atmosphere.