Direct numerical simulation of turbulent spray combustion in the SpraySyn burner : impact of injector geometry

Abstract

Spray combustion is one of the most important applications connected to modern combustion systems. Direct numerical simulations (DNS) of such multiphase flows are complex and computationally very challenging. Ideally, such simulations account for atomization, breakup, dispersion, evaporation, and finally ignition and combustion; phase change, heat and mass transfer should be considered as well. Considering the complexity of all those issues, and to simplify again the problem, virtually all DNS studies published up to now replaced the injector geometry by an approximated, simple configuration, mostly without any walls within the DNS domain. The impact of this simplification step is not completely clear yet. The present work aims at investigating the impact of a realistic injector geometry on flow and flame characteristics in a specific burner (called SpraySyn burner). For this purpose, two cases are directly compared: one DNS takes into account the inner geometry of the injector, including walls of finite thickness; a second one relies on a simplified description, as usually done in the literature. It has been found that considering the details of the geometry has a noticeable impact on the evaporation process and ultimately on the flame structure. This is mostly due to the effect of recirculation zones appearing behind thick injector walls; though quite small, they are sufficient to impact the evolution of the flow and of all connected processes.