Modeling the Effect of Primary Atomization on Diesel Engine Emissions

A new primary breakup model was developed and applied to simulate the diesel fuel spray and atomization process. The continuous liquid fuel jet was simulated by a discrete Lagrangian particle method, and the primary breakup of the jet was calculated using a new 1-D Eulerian method that provides the jet breakup time and drop size distribution. A set of correlations of the breakup characteristics, including the breakup time and drop size, were developed for a range of operating conditions. The correlations were then used in the KIVA code to predict the jet primary breakup. For drop secondary breakups, the Kelvin-Helmholtz/Rayleigh-Taylor hybrid model was employed. The new primary breakup model was first validated by comparison to experimental breakup length and jet liquid tip penetration lengths. Predictions of the new breakup model were also compared with experimental data and predictions of the standard breakup model. Improvements over the standard model were seen, and good agreements with the experimental data were obtained. The new breakup model was applied to diesel combustion and emissions predictions in combination with other sub-models. The in-cylinder pressure and temperature, as well as emissions, were compared with available experimental data and predictions from the new and standard breakup models. The new breakup model provided accurate predictions, and shows that the primary jet atomization process has a significant influence on diesel particulate emissions.