Simultaneous PLIF/PIV investigation of vortex-induced annular extinction in H₂-air counterflow diffusion flames

High-temporal-resolution measurements of scalars and velocity are used to study vortex-induced annular (off-centerline) flame extinction during the interaction of a propagating vortex with an initially stationary counterflow hydrogen-air diffusion flame. Such an extinction process differs from classical one-dimensional descriptions of strained flamelets in that it captures the effects of flame curvature as well as dynamic strain. Planar laser-induced fluorescence (PLIF) measurements of the hydroxyl radical (OH) are used to track flame development, and simultaneous particle-image velocimetry (PIV) is used to characterize the two-dimensional flowfield. Measurements reveal differences in local normal strain rate profiles along and across the reaction zone and indicate that vortex-induced curvature in the annular region may initiate the extinction process. In addition, the effect of local flame extinction on vortex evolution and dissipation is determined from measured vorticity data.