How does a diesel engine ignite its fuel?

A diesel engine ignites its fuel primarily through the process of compressing air to a high temperature. In a diesel engine, air is drawn into the cylinder and then compressed to a significantly high pressure. This compression heats the air to a temperature that is sufficient to ignite the fuel when it is injected.

When fuel is injected into the highly compressed, hot air, it vaporizes and ignites spontaneously due to the elevated temperature of the air. This process of ignition is a characteristic feature of diesel engines, distinguishing them from gasoline engines, which rely on spark plugs to initiate combustion. The high compression ratio used in diesel engines not only aids in the ignition process but also contributes to their efficiency and power output.