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

摘要

Premixed compression ignition (PCI) combustion offers a unique opportunity to simultaneously and substantially reduce nitric oxides (NO_x) 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 NO_x emissions. On a relative basis, it appears as though NO_x 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 NO_x formation on temperature reduction is investigated, with consideration given to changing air-fuel (AF) ratios as EGR rate increases.