Effects of triply periodic minimal surface porous media structures on combustion and heat transfer characteristics of low-concentration methane

Abstract

Porous medium burners can improve the combustion efficiency of low concentration methane, promote the utilization of low grade energy sources, and reduce greenhouse gas emissions. As a new type of porous medium, it is of great significance to investigate the effects of different Triply Periodic Minimal Surfaces structures on the combustion process of low concentration methane. In this study, Diamond and Gyroid burners were constructed with different values of ω (structural parameters, which control the structural period and pore channel scale). Computational fluid dynamics methods were employed to investigate their internal pore scale flow, heat transfer characteristics, and flame structure. The results indicate that increasing ω refines the pore channels and increases the specific surface area (S), thereby enhancing gas solid heat transfer while simultaneously increasing flow resistance. When comparing the two structures, the Gyroid exhibited lower flow resistance and higher internal flow velocities, with peak velocities of 1.05–1.12 m/s, higher than the 0.84–1.10 m/s observed in the Diamond structure. However, the interlaced channels within the Diamond structure were more effective at suppressing velocity fluctuations and confining the flame near the inlet, resulting in a more concentrated high-temperature zone. The carbon containing components in the combustion products are primarily CO2, accounting for 95%–97%, while CO accounts for 3%–4%. Under different ω conditions, CH4 undergoes nearly complete combustion, nevertheless, structures with larger ω values cause secondary oxidation of CO at the rear end of the burner, thereby reducing CO emissions and improving combustion efficiency.