Influence of Mixture Composition and Radial Flame Location on Counter-rotating Vortex Pair Evolution in a reacting jet in crossflow

Abstract

This study analyzes the influence of combustion on the topology and dynamics of a reacting jet in cross flow. Past work has noted that the stability of the jet shear layer vortices (SLV) is strongly influenced by the radial flame location relative to the jet shear layer. This study analyzes radial flame location effects on the downstream development of the counter-rotating vortex pair (CVP). Large eddy simulations (LES) were performed for four cases - one non-reacting (NR) and three reacting (R1, R1.5, and R2 where the flame is moved from outside to inside of the jet shear layer by altering the composition of the jet and the crossflow), contrasting both the effect of combustion and the radial flame location on flow topology. The NR case shows the classical CVP development. In the R1 case, where the flame is located radially outboard of the shear layer development, shear layer growth rates are reduced but qualitatively similar to the NR case. Moreover, the CVP structure is qualitatively similar to the non-reacting case. When the flame is moved inside the shear layer (case R2) the shear layer vorticity does not concentrate into discrete vorticities, but remains distributed in the stream wise direction. Moreover, the CVP structure is considerably different, lacking the characteristic double-lobed structure (containing streamwise vorticity) that is such a familiar feature of this flow field. The wake flow field shows a significant recirculation region, similar to a bluff body flow field. The results demonstrate the profound effect that radial flame location has on both the near field dynamics of SLV structures and the far-field organization of the CVP.