Blowoff dynamics of lean premixed flames stabilized on a meso-scale bluff-body

Bluff-bodies have been used as effective flame holders for practical applications of premixed flames. While many studies about bluff-body stabilization have been done both experimentally and numerically, there is still the lack of understanding of blowoff mechanism. Direct numerical simulations are conducted to investigate dynamics of lean premixed hydrogen-air and syngas-air flames anchored on a meso-scale bluff-body flame holder. A two-dimensional square channel of 10 mm-by-10 mm with a square bluff-body of 0.5 mm is considered as a computational domain. The height of domain is chosen as an unconfined condition to minimize the effect of blockage ratio. Density ratio of the flame decreases by preheating to investigate hydrodynamic effects on flame dynamics in both hydrogen-air and syngas-air mixtures as ramping up the mean inflow velocity until blowoff occurs. Phenomenological descriptions of flame dynamics are presented, including the process of blowoff events. The objectives of this study are to understand blowoff mechanism and to investigate the hydrodynamic effects on the flame dynamics.