Numerical Analysis of Hydrogen Peroxide Addition and Oxygen-Enriched Methane Combustion

Methane (CH₄)/air lean combustion can be enhanced by increasing the concentration of the oxidizer, like oxygen (O₂) enrichment, or adding a strong oxidant to the reactant. Hydrogen peroxide (H₂O₂) is a strong oxidizer that yields O₂, steam, and appreciable heat after decomposition. This study numerically investigated and compared the effects of H₂O₂ and O₂-enriched conditions on the adiabatic flame temperature, laminar burning velocity, flame thickness, and heat release rates of CH₄/air combustion using the San Diego mechanism. The result showed that in fuel-lean conditions, the adiabatic flame temperature changed from H₂O₂ addition > O₂-enriched scenario to O₂-enriched scenario > H₂O₂ addition with increasing α. This transition temperature was not affected by the equivalence ratio. Adding H₂O₂ enhanced the laminar burning velocity of the CH₄/air lean combustion more than the O₂-enriched scenario. The thermal and chemical effects are quantified in various H₂O₂ additions, and it is found that the chemical effect has a noticeable contribution to the laminar burning velocity compared with the thermal effect, especially in higher H₂O₂ addition. Further, the laminar burning velocity had a quasi-linear correlation with (OH)_max in the flame. The maximum heat release rate was observed at lower temperatures for H₂O₂ addition and higher temperatures for the O₂-enriched scenario. The flame thickness was significantly reduced upon adding H₂O₂. Finally, the dominant reaction to the heat release rate changed from the reaction of CH₃ + O ↔ CH₂O + H in the CH₄/air or O₂-enriched scenario to the reaction of H₂O₂ + OH ↔ H₂O + HO₂ in the H₂O₂ addition scenario.