The effect of stoichiometry on vortex flame interactions

The interaction of a vortex pair with a premixed flame serves as an important prototype for premixed turbulent combustion. In this study, we investigate the interaction of a counterrotating vortex pair with an initially flat premixed methane flame. We focus on characterizing the mechanical nature of the flame-vortex interaction and on the features of the interaction strongly affected by fuel equivalence ratio, φ. We compare computational solutions obtained using a time-dependent, two-dimensional adaptive low Mach number combustion algorithm that incorporates GRI-Mech 1.2 for the chemistry, thermodynamics and transport of the chemical species. We find that the circulation around the vortex scours gas from the preheat zone in front of the flame, making the interaction extremely sensitive to equivalence ratio. For cases with φ ≈ 1, the peak mole fraction of CH across the flame is relatively insensitive to the vortex whereas for richer flames we observe a substantial and rapid decline in the peak CH mole fraction, commencing early in the flame-vortex interaction. The peak concentration of HCO is found to correlate, in both space and time, with the peak heat release across a broad range of equivalence ratios. The model also predicts a measurable increase in C2H2 as a result of interaction with the vortex, and a marked increase in the low temperature chemistry activity. The effect of stoichiometry on vortex flame interactions 1