Diesel engines are internal combustion engines. The main difference compared to other internal combustion engines is how the fuel is ignited. Hot air from the compressor is transferred to the combustion chamber, but instead of requiring an ignitor, the air is hot enough that when the fuel is injected, it spontaneously combusts. Spontaneous combustion is the result of two things, the self-ignition temperature of diesel and the compression ratio of diesel engines.
Because the fuel is injected before it ignites, there is an uneven distribution of fuel. Diesel engines operate with a diffusion flame— the oxygen diffuses into the flame. The torque produced is controlled through the manipulation of the air ratio. Diesel engines rely on changing the amount of injected fuel and the air ratio is typically high. Its high expansion ratio makes it the highest thermal efficiency combustion engine— it enables heat dissipation by the excess air.
Some of the common advantages of diesel engines are:
Some of the common disadvantages of diesel engines are:
Diesel engines have a wide variety of applications including passenger cars, commercial vehicles, locomotives, watercraft, and construction equipment. Just like every other component of an engine, the pros and cons of a diesel engine need to be evaluated based on their applications.