Diesel Combustion

AbstractThe diesel combustion process and combustion system are briefly described, with the aim to provide a starting point for those interested in exploring and developing these. The chapter describes the typical characteristics of the diesel combustion process and its heat release. A description is given of how hardware in the combustion system supports the combustion process, for example, the importance of the combustion chamber geometry and the fuel injection system. Furthermore, useful theoretical concepts are presented to provide the reader with simple tools for understanding limiting processes for emissions formation. These include scaling relationships for air entrainment and flame lift‐off in quasi‐stationary diesel jets. Heavy duty and light duty combustion systems are then treated separately, since differences in duty cycle and customer requirements have given them different characteristics. Due to the high‐load duty cycle, with long injections and high fueling rates, heavy duty diesel combustion can be analyzed by analogy to a quasi‐stationary jet. In light duty engines, where injections typically are short, a significant portion of the heat release takes place after the end of injection. Therefore the picture of a quasi‐stationary jet becomes inadequate. Emphasis is put on describing fluid mechanic processes supporting the late‐cycle combustion in these engines. Finally, means of in‐cylinder emissions control in diesel engines are discussed.