Blow-off mechanism of a holder-stabilized laminar premixed flame in a preheated mesoscale combustor

Abstract

In a previous study, we fabricated a well-designed mesoscale combustor with a flame holder and preheating channels to improve the flame stability under extreme combustion conditions. This combustor can also act as a model for studying the synergistic effect of heat and flow recirculation on the flame dynamics. This paper systematically illustrates and discusses the blow-off mechanisms of a holder-stabilized laminar premixed flame in a preheated mesoscale combustor via three-dimensional numerical simulation. The flame blow-off processes that have been observed experimentally at various Reynolds number (Re) are well reproduced. Pinch-off appears at large Re but is absent at small Re. First, the moving characteristics of the flame root and flame top in the blow-off process at small Re are discussed in detail. Then, the flame pinch-off mechanisms are carefully analyzed in terms of the flow field, conjugate heat exchange, and stretch effect. The results indicate that the influence of conjugate heat exchange, which exists between the flame holder and flame root, is not significant in the flame pinch-off phenomenon, but a larger recirculation zone (which helps to stabilize the flame root) and flame stretch (which splits the flame) both induce flame pinch-off. This work can aid in gaining insight into the flame blow-off dynamics when the effects of heat and flow recirculation work synergistically in many practical combustors.