A Computational Investigation into the Effects of Spray Targeting, Bowl Geometry and Swirl Ratio for Low-Temperature Combustion in a Heavy-Duty Diesel Engine 2007-01-0119

A computational study was performed to evaluate the effects of bowl geometry, fuel spray targeting and swirl ratio under highly diluted, low-temperature combustion conditions in a heavy-duty diesel engine. This study is used to examine aspects of low-temperature combustion that are affected by mixing processes and offers insight into the effect these processes have on emissions formation and oxidation. The foundation for this exploratory study stems from a large data set which was generated using a genetic algorithm optimization methodology. The main results suggest that an optimal combination of spray targeting, swirl ratio and bowl geometry exist to simultaneously minimize emissions formation and improve soot and CO oxidation rates. Spray targeting was found to have a significant impact on the emissions and fuel consumption performance, and was furthermore found to be the most influential design parameter explored in this study. Specifically, variations in spray targeting were found to largely affect pre-combustion mixing processes and charge preparation, resulting in marked effects on soot formation levels. Swirl ratio was found to alter both pre-combustion mixture preparation and late-cycle oxidation processes, while bowl geometry was found to predominantly affect mixing processes through an interaction with swirl ratio levels. This study underscores the need to carefully consider mixing processes induced by bowl geometry and spray/bowl matching in the design of low-temperature diesel combustion systems.