CLASSIFICATION OF ENGINES

Mechanical engines are basically classified in to two types:
                                        *INTERNAL COMBUSTION ENGINES (IC)
                                         *EXTERNAL COMBUSTION ENGINES

In internal combustion engines the combustion of fuels takes place inside the engine cylinder and where as in external combustion engines the combustion of fuel take place outside the engine with the help of a grate or something.Basically coal is used as a fuel in external combustion engines.For eg.early 1940's trains used EC engines for which coal is used as a fuel.

                                         FIG 1.0      EXTERNAL COMBUSTION ENGINE

                                            FIG 2.0       INTERNAL COMBUSTION ENGINE