Enhancement of CH₄/Air combustion performance in porous media with a three-layer structure

This work presents an experimental investigation comparing the combustion performance of two-layer and three-layer porous media structures of CH₄/Air. Visible flame characteristics, OH* distribution, temperature distribution, and excess enthalpy combustion features are evaluated to compare the performance of the two structures. The experimental results indicate that the three-layer structure exhibits better temperature distribution characteristics under all operating conditions, with the average temperature in the primary combustion zone being 61 to 117 K higher than the two-layer structure across different conditions. The three-layer structure exhibits more stable excess enthalpy combustion, particularly at Φ = 0.55 where the two-layer structure shows significant decline. Under varying equivalence ratio conditions, the excess enthalpy temperature in most operating conditions and regions exceeds that of the two-layer structure by approximately 80 to 100 K. However, the excess enthalpy combustion characteristics of the two structures both weaken with increasing equivalence ratio. Under varying inlet velocity, a better excess enthalpy combustion effect is observed when u ≥ 1.0 m/s. The three-layer structure exhibits more stable flame under various conditions, making it less prone to flashback and blowout compared to the two-layer structure. Additionally, the recirculation efficiency of the three-layer structure is higher across all operating conditions, achieving a more effective heat recirculation process.