Flame Propagation of Premixed Gas with Enhanced Heat Recirculation: Dynamic Characteristics of Lean and Rich Combustion

Abstract

Porous media combustion greatly improves the combustion of low calorific value gas (LCG), and appropriate heat control contributes to optimizing the flame evolution. To obtain the dynamic characteristics of lean-rich combustion, an enhanced heat-recirculating burner is built by embedding the cylindrical rod with high thermal conductivity. The temperature distribution and gas products are investigated under different rod parameters and operating conditions. The results indicate that the reduction of the equivalence ratio and inlet velocity are both beneficial for the upstream propagation of rich-methane flame, which has an opposite trend to lean combustion. Regardless of the direction in which the rich-methane flame propagates, the flame propagates the fastest as the diameter of the cylindrical rod is 8 mm. When the 8–120 cylindrical rod is embedded in the burner, the downstream propagation time is shortened by 73.40%. The appropriate embedment of the cylindrical rods in porous media not only accelerates the rich-methane flame propagation but also promotes the conversion of methane to syngas. Moreover, the decrease in pellet diameter is also conducive to increasing syngas production. The above conclusions provide theoretical support for the efficient and clean utilization of LCG in the porous media.