Anomalous blow-off behavior of a holder-stabilized premixed flame in a preheated mesoscale combustor

摘要

The present study investigates the blow-off limits of a laminar methane–air premixed flame under thesynergistic effect of heat and flow recirculation by means of experimentation and three-dimensional numericalsimulation. An anomalous blow-off phenomenon (the blow-off limit decreases with the decreasein Reynolds number ( Re )) is experimentally observed and reproduced via simulation. First, the flame basestructures for various Re values are studied. Subsequently, the underlying mechanisms are revealed interms of flow field, stretch effect, preferential transport effect, and conjugate heat transfer. The maincauses of the present anomalous blow-off phenomenon are the flow recirculation effect, preferentialtransport effect, and conjugate heat transfer, rather than the stretch effect. Specifically, a weaker flowrecirculation effect, a weaker preferential transport effect, a larger heat loss ratio from the combustor tothe ambient environment, and a lower preheated temperature of the fresh mixture altogether lead to asmaller blow-off limit at a smaller Re . In addition, the sharp reductions in both the local equivalence ratioand preheated temperature of the fresh fuel-oxidizer mixture explain why the blow-off limit sharply decreasesfrom Re = 80 to 40. This work offers insights into flame blow-off behaviors under the synergisticeffect of heat and flow recirculation in many practical combustors.