How is the fuel of a diesel engine ignited?

In a diesel engine, fuel ignition occurs through a process called compression ignition. This method relies on the high heat generated from the compression of air within the engine's cylinders, rather than an external source such as a spark plug or flame. When the air is compressed to a high degree, its temperature increases significantly.

Once the piston compresses the air to a sufficient temperature, the diesel fuel is injected into the cylinder. The heat from the compressed air is enough to ignite the fuel spontaneously, leading to combustion. This is a critical difference from gasoline engines, which utilize spark plugs to ignite a fuel-air mixture.

Consequently, the mechanism of ignition in diesel engines underscores the importance of the compression ratio and temperature management within the engine, making the compression ignition method fundamental to diesel engine operation.