Comprehensive Study of Extinction, Re-ignition, and the Evolution of an Annular Edge Flame in a Counterflow Flame Perturbed by Vortices

摘要

The structure of a time-dependent methane/enriched-air flame established in an axisymmetric, laminar counterflow configuration during the interaction with two twin vortices is investigated. Computationally, the time-dependent equations are written using a modified vorticity-velocity formulation, with detailed chemistry and transport, and are solved implicitly on a non-staggered, non-uniform grid. Boundary conditions are chosen to create local extinction and reignition in the vicinity of the axis of symmetry. Experimentally, CO planar laser-induced fluorescence (PLIF), OH PLIF and an observable proportional to the forward reaction rate (RR) of the reaction CO + OH → CO_2 + H are measured. Particle image velocimetry (PIV) is used to characterize the velocity field of the vortical structures and to provide detailed boundary conditions for the simulations. Excellent agreement is found between model and experiments to the most minute morphological details throughout the interaction. The validated model is then used to probe the dynamics of the two-dimensional extinction/reignition process with high temporal resolution and emphasis on the edge flame transition from extinction mode to ignition mode.