Flame Diagnostics with a Conservative Representation of Chemical Explosive Mode Analysis

A conservative representation of a chemical explosive mode analysis is formulated for flame diagnostics in compressible reactive flows. The flame characteristics are detected by the quantification of individual contributions of chemical reaction, diffusion, and compressibility to chemical explosive modes. The diagnostic method is first applied to analyze one-dimensional representative flames. The analysis shows that compressibility plays the dominant role among the nonchemical effects for chemical explosive modes in high-speed flows. Then, the diagnostic method is further applied to analyze the flame stabilization mechanisms in the Burrows-Kurkov supersonic flames, for which large-eddy simulations have been performed and validated against measurement data. Results show that chemical reaction controls the flame kernel formation, indicating that autoignition governs the flame stabilization. Furthermore, compressibility has the same order of magnitude contribution to chemical explosive modes as the chemical reaction in the surrounding area of the ignited flame kernels, which counteracts chemical reaction for the growth of the flame kernels.