Extraction of turbulent flame structures and dynamic modes with corrected OH-PLIF images for a hydrogen micromix burner

The combination of micromix and diluted combustion technologies is an effective way to realize stable H2 flames with low NOx emission, and the dynamic modes and turbulent flame structures with corrected OH-PLIF (1 kHz) images for a hydrogen micromix burner were experimentally studied in this work under different steam dilution ratios (D) and equivalence ratios (phi). Two types of flames, anchored and lifted, are found for different inlet conditions (dilution ratios (D) and equivalence ratios (phi)). When the flame tends to lift, the flame shape and location of the peak OH signal have obvious change over time and the results show that the flame stability reduces. Besides, the flame surface density (FSD) has small values distributed around the flame root, making the flame more unstable. When the flame is lifted, the distribution of FSD becomes wider (not mainly in the shear layer zone (SLZ)) and a large part of FSD is distributed in the flame root. In general, dynamic mode decomposition (DMD) analysis results show that the anchored flame has a lower flame frequency than that of the lifted flame in the same mode. Diluted micromix combustion technology is an effective way to realize stable H2 flames with low NOx emission, and the turbulent flame structures of a micromix burner are experimentally revealed in this work with corrected OH-PLIF images.