How is diesel fuel ignited in a warm diesel engine?

In a warm diesel engine, diesel fuel is ignited by the heat generated from the compression of air within the cylinder. When the piston compresses the air, its temperature rises significantly due to the laws of thermodynamics—more specifically, the ideal gas law. This rise in temperature is sufficient to ignite the diesel fuel when it is injected into the highly compressed, hot air in the combustion chamber.

In contrast, gasoline engines rely on a spark generated by a spark plug to initiate combustion. Therefore, the process of ignition in diesel engines is fundamentally different, as it does not involve an electronic spark but instead depends solely on the temperature created through compression. This characteristic is a key feature of the diesel combustion cycle, differentiating it from other types of internal combustion engines.