Effect of hydrogen addition on CO emission and thermo-chemical state near wall during head-on quenching of laminar premixed methane/air flame

Abstract

A computational model for premixed methane-air flame under the flame-wall interaction was established based on CFD software and experimentally verified. The head-on quenching process of premixed methane-air flame under different hydrogen additions was simulated. The changes in CO emission, quenching distance, and the distribution of CO near the wall under different hydrogen additions were obtained. With the increase of H2 addition, the mass fraction of HCO and the generation of CO increase. Moreover, the consumption of OH in R79: OH+H2=H+H2O increases, resulting in the weakening of the oxidation of OH to CO in R94: OH+CO=CO2+H, and the EICO increases. With the increase of H2 addition, the heat release rate increases, the quenching distance decreases, and the Peclet number (Pe) increases. With the increase of hydrogen addition, the mole fraction of CO in Region A gradually decreases, the mole fraction of CO in Region B first increases and then decreases, and the mole fraction of CO in Region C increases. The temperature drops first and then rises. Near the wall (y < 0.3 mm), the convection term and diffusion term dominate, and the heat transfer time is less than the generation time and oxidation time of CO, and the generation branch and oxidation branch of CO move to the low-temperature region. Far from the wall (y ≥ 0.3 mm), the reaction source term dominates, the heat transfer time is greater than the generation time of CO, less than the oxidation time of CO, and the oxidation branch of CO moves to low temperature. With the increase of hydrogen addition, the chemical time scale of CO decreases, and the generation branches and oxidation branches of CO move to higher temperatures.