On the sensitivity of NOx to exhaust gas recirculation in a premixed compression ignition engine

Premixed compression ignition (PCI) combustion offers a unique opportunity to simultaneously and substantially reduce nitric oxides (NOx) and particulate matter (PM) from diesel engines. Exhaust gas recirculation (EGR) plays a critical role in attaining PCI by both extending ignition delay as well as reducing flame temperature of the combustion event, thus also reducing NOx emissions. On a relative basis, it appears as though NOx is more sensitive to EGR under PCI conditions than under conventional combustion conditions. This article provides more insight into this apparent sensitivity. Furthermore, the dependence of NOx formation on temperature reduction is investigated, with consideration given to changing air-fuel (AF) ratios as EGR rate increases.

On the sensitivity of NOx to exhaust gas recirculation in a premixed compression ignition engine Conference Paper