The stability of reacting single-mode Rayleigh-Taylor flames

From detailed 1D and 2D numerical simulations of a non-premixed, single-mode Rayleigh-Taylor (RT) flame, we report on mechanisms for stabilization and destabilization of the underlying flow. A new problem for non-premixed flames is defined where a sharp interface separating a fuel and oxidizer evolves under the influence of the RT instability, while the instability-driven mixing in turn enhances burning at the flame site. When the initial configuration is globally unstable, the onset of burning within the reaction zone results in an active third layer that renders the fuel-flame interface stable near the spikes. In contrast, for an initial configuration that is globally stable, the reaction zone renders the fuel-flame surface unstable. The observed pathways to stability and instability in each case may be realized by directly manipulating the density difference driving the flow, by varying the proportion of inert N-2 in the fuel stream. The specific results are relevant to the performance of compact combustors, while the novel flow configuration investigated here can potentially provide a new framework for understanding the properties of several non-premixed flames. (C) 2020 Elsevier B.V. All rights reserved.