Analysis of ultra-low concentration methane combustion in gradient D-type TPMS structural porous medium by experimental and pore-resolved simulations

Abstract

This study systematically investigates flame stabilization mechanisms and heat transfer characteristics in gradient Diamond-type triply periodic minimal surface (D-TPMS) porous media burners under ultra-low concentration methane conditions, using a combined experimental and pore-scale simulation approach. A comparative analysis of linear gradient (LGD-TPMS) and step gradient (SGD-TPMS) structures reveals distinct combustion performance differences. A pore-resolved numerical model was developed to capture the complex radiation-convection coupled heat transfer mechanism within the TPMS structure and elucidate the distribution patterns of surface radiation and localized gas-solid heat flux in periodic pore channels. Results indicate that SGD-TPMS is prone to flame surface rupture due to abrupt interfacial changes, whereas LGD-TPMS facilitates stable finger-like anchored flames with significantly broadened combustion stability limits. Combustion-induced flow acceleration outweighs pure structural effects: at an equivalence ratio of 0.5, a 0.2 m/s increase in inlet velocity resulted in a 1.2 m/s rise in peak velocity within the reaction zone. In the preheating zone, the solid skeleton efficiently preheats via radiation absorption from downstream high-temperature regions; in the reaction zone, intense convective heat exchange dominates between gas and solid phases, while radiation heat flux exhibits a distinct spatial pattern with mid-zone emission and upstream/downstream absorption, significantly enhancing lateral heat uniformity and flame stability. This demonstrates that localized thermal management can be achieved by adjusting the structural parameters of the LGD-TPMS. This study provides theoretical reference for the structural design of highly efficient porous media burners and the utilization of low-concentration methane.