compressedignition

Compressed ignition refers to a process in internal combustion engines where the fuel-air mixture ignites spontaneously due to the high temperatures and pressures generated during compression. This is the fundamental principle behind diesel engines. Unlike spark-ignition engines (like gasoline engines) which rely on an external spark to initiate combustion, compressed ignition occurs naturally as the piston compresses the mixture to a critical point.

In a typical diesel cycle, air is drawn into the cylinder and then compressed to a very high ratio. This intense compression raises the air's temperature significantly, often exceeding the autoignition temperature of diesel fuel. Once the piston reaches the top of its stroke, or near it, fuel is injected directly into the hot, compressed air. The finely atomized fuel mixes rapidly with the air and, due to the high temperature, ignites on its own without any need for a spark plug. This self-ignition is the defining characteristic of compressed ignition.

The advantages of compressed ignition include higher thermal efficiency compared to spark-ignition engines, leading to better fuel economy, and the ability to produce higher torque at lower engine speeds. This makes diesel engines well-suited for heavy-duty applications, trucks, and buses. However, compressed ignition engines typically produce more nitrogen oxides (NOx) and particulate matter, requiring more complex exhaust after-treatment systems to meet emissions standards.