Swirler geometry effect on a variable density coaxial jet behavior

Mixing process and flow structure in a confined coaxial configuration are numerically examined under a swirl generator insertion. The effect of the swirler geometry on the resulting turbulent coaxial jet behavior is investigated. RANS calculations were conducted to study the effect of the central swirler zone nature (solid/fluid) on dynamic and species fields. Turbulence was taken into account using the k-epsilon Realizable model. Numerical findings were discussed for both reactive and non reactive conditions. For non reacting mixture, it has been shown that the annular swirler enhances mixing between the central jet and the surrounding air. In this case, mixing improvement is due to the development of a central recirculation zone in the confined volume. However, for reactive mixture, the non annular swirler corresponds to the best test case. Indeed, the annular presents the problem of flattened fuel radial profiles near the confinement walls which could generate a flame flashback problem.