Diesel Engine concept

Diesel engine is any internal-combustion engine in which air is compressed to a sufficiently high temperature to ignite diesel fuel injected into the cylinder, where combustion and expansion actuate a piston.

It converts the chemical energy stored in the fuel into mechanical energy, which can be used to power freight trucks, large tractors, locomotives, and marine vessels. 

A limited number of automobiles also are diesel-powered, as are some electric-power generator sets.

How is a diesel engine different from a gasoline engine?

Gasoline engines and diesel engines both work by internal combustion, but in slightly different ways. In a gasoline engine, fuel and air is injected into small metal cylinders. 

A piston compresses (squeezes) the mixture, making it explosive, and a small electric spark from a sparking plug sets fire to it. 

That makes the mixture explode, generating power that pushes the piston down the cylinder and (through the crankshaft and gears) turns the wheels.