3-D numerical consideration of nozzle structure on combustion and emission characteristics of DI diesel injector

摘要

A three-dimensional approach was used to capture the main parametric influences of injector geometries on combustion characteristics by utilization of a constant volume vessel. The investigation was performed by means of two case studies. In the first case study, the nozzle inclination angle was varied for group-hole nozzle layout, while the second case study analyses the single dense spray of an injector while its inlet-rounding radius to nozzle diameter ratio was being changed. Results demonstrate that closer included angle (up to 10°) leads to higher penetration of spray and thus greater LOL (lift-off length) and ID (ignition delay). A decreasing trend as a result for overall emissions of NO_X and soot mass fraction was observed. With regard to the second case study, decrement of r/d brings about enhancement of mixing quality of spray that leads to higher evaporation rate and accumulated heat release. Increasing heat release will augment chamber temperature that in turn contributes to higher NO_X formation. Higher cavitation caused better liquid jet disintegration and smaller spray droplet that reduces soot mass fraction of late combustion process. The present study is intended to investigate primarily the effect of injector geometry on critical combustion components. The combination of changes in vessel pressure and group-hole nozzle angle is considered to study the combustion behavior of sprays and subsequent emissions content.