stratifiedcharge

Stratified charge is a combustion strategy used in internal combustion engines to improve fuel efficiency and reduce emissions. The core principle involves creating a fuel-air mixture within the combustion chamber that is not uniform, or stratified. Typically, this means creating a richer fuel-air mixture near the spark plug for easier ignition and a leaner mixture in the rest of the combustion chamber. This leaner mixture burns more slowly and at a lower temperature, which can reduce the formation of nitrogen oxides (NOx).

Various designs have been employed to achieve stratification. Some systems use a pre-chamber or a divided combustion chamber. In a pre-chamber design, a small chamber containing a rich fuel-air mixture is ignited by the spark plug. The flame front then propagates from this pre-chamber into the main combustion chamber, which contains a leaner mixture. Other approaches involve carefully timed fuel injection directly into the cylinder or specific piston crown designs that direct the air and fuel into distinct regions.

The goal of stratified charge is to combine the benefits of igniting a readily combustible mixture with the efficiency and low emissions of burning a lean mixture. While promising for its potential to meet stringent emissions standards and improve fuel economy, practical implementation has faced challenges. These include the complexity of control systems, potential for misfires with very lean mixtures, and the need for precise fuel injection or air-fuel mixing. Despite these challenges, the concept remains an area of interest in engine development.