Influence of Wall Impingement on the Structure of Reacting Jets

In Diesel engines, the vapor phase of the fuel jet is known to impinge on the walls. This impingement is likely to have an effect on mixing characteristics, the structure of the diffusion flame and on pollutant formation and oxidation. These effects have not been studied in detail in the literature. In this work, the structure of a laminar wall jet that is generated from the impingement of a free laminar jet on a wall is discussed. We study the laminar jet with the belief that the local structure of the reaction zone in the turbulent reacting jet is that of a laminar flame. Results from non-reacting and reacting jets will be presented. In the case of the non-reacting jets, the focus of the inquiry is on assessing the accuracy of the computed results by comparing them with analytical results. Velocity profiles in the wall jet, growth rates of the half-width of the jet and penetration rates are presented. The velocities in the wall jets are shown to be self-similar and agree with analytical results. In the case of reacting jets, the focus of the inquiry is on the differences in the structure of the jet relative to the non-reacting jet and on the temperature and species profiles in the jet. Methane is employed as the fuel. Chemical kinetics is modeled with detailed mechanism with 53 species. Species profiles in the wall jet are compared with those in the free jet. Wall interactions are shown to affect minor species distribution in the wall jet. This, in turn, affects pollutant formation.