Optimization of Injector Spray Configurations for an HSDI Diesel Engine at High Load

CFD simulations were conducted with the KIVA-3v code with improved spray and combustion sub-models. Combustion analysis was performed using micro-genetic optimizations for a 1.9L HSDI diesel engine at a high load operating conditions (∼15 bar imep). The study explored injector spray configurations, including the number of injector nozzle holes, the hole diameters, and their orientations. The engine swirl ratio and start-of-injection timing were also varied. The optimizations considered injector nozzles with 14, 12, 10 and 8 injector holes. Each configuration included consideration of a pair of injector holes. Variations in the orientation angle of the first hole were explored. For the second hole, both the orientation angle and the azimuthal spacing relative to the first hole were varied. The chosen parameters allowed the holes to be symmetrically spaced or coincident azimuthally. The performance of each simulation was based on a merit function which accounts for fuel economy, NOx and soot emissions. For the test conditions chosen, an 8-hole injector configuration was found to be the best. This is explained by the improved fuel spray penetration and mixing associated with a smaller number of large diameter nozzle holes. For all injector configurations, the optima selected groups of holes where the total angular spacing between holes was less than eight degrees. The optimum swirl ratio found was approximately that of the baseline engine design.