Edge flames in mixing layers: Effects of heat recirculation through thermally active splitter plates

A numerical study is carried out to investigate the stabilization and dynamic properties of the edge flame formed in the wake of two merging streams, one containing fuel and the other oxidizer, separated by a splitter plate. Several plates are considered to illustrate the effects of their thermo-physical properties on the edge flame for low- and high-Lewis-number mixtures. The objective is to provide a comprehensive understanding of the effects of the heat recirculation cycle, from the edge flame through the splitter plate and back to the fresh reactants, on the edge flame. A diffusive-thermal model is adopted, with the flow field determined by solving the incompressible Navier–Stokes equations in the vicinity of the plate trailing edge, and the combustion field determined by solving the transport equations with a constant density. Two distinct modes of flame stabilization are identified and examined: a stationary mode, where the edge flame is held stationary at a well-defined distance, whether attached to or lifted from the tip of the plate, and an oscillatory mode where the edge flame undergoes sustained oscillations relative to an (unstable) equilibrium position. To characterize the heat recirculation effect under varying flow/mixture conditions, we introduce the thermal sensing distance, as a heuristic parameter that determines whether substantial thermal interaction between the edge flame and the plate occurs, and the average output heat flux, as a universal measure characterizing the efficiency of the heat recirculation cycle.