The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

Abstract

The characteristics of premixed methane/air combustion in a microchannel with a Pt catalyst were examined and the effect of inlet velocity on catalytic methane combustion with hydrogen addition was investigated numerically. It is shown that appropriate hydrogen addition can expand the extinction limits, particularly the upper extinction limit of the inlet velocity, and increase methane conversion at higher inlet velocities. However, it is proved that methane conversion at an equivalent ratio of 0.8 decreased with hydrogen addition when inlet velocity was lower than 0.36 m s−1. The heat released in the hydrogen–oxygen reaction increased the wall temperature, which resulted in the adsorption–desorption equilibrium of oxygen shifting towards desorption as Pt(s) coverage increased and O(s) coverage decreased. With the same amount of hydrogen added, the changes in wall temperature that reflected the thermal effects of hydrogen were more obvious at higher inlet velocities, which improved methane conversion. If the heat released by hydrogen was neglected, the competitive consumption of oxygen, which demonstrates the chemical effect of hydrogen, was more significant at lower inlet velocities, which inhibited methane conversion.