CFD study on stability limits of hydrogen/air premixed flames in planar micro-combustors with catalytic walls

Abstract

Micro-combustion encounters both thermal and radical quenching, resulting in poor flame stability. Catalytic reactions offer a potential solution to counter radical quenching. A numerical study on the flame stability limits of hydrogen/air premixed combustion in planar micro-combustors with catalytic walls is carried out. A two-dimensional numerical model comprising detailed gas-phase and surface chemical kinetics is established for a parametric study to investigate the effects of key design and operational parameters on the stability limits. Under the fuel-lean condition, the coating of platinum dramatically enhances the wall temperature, compared to the gas-phase reaction mode. However, the blowout limit decreases as a result of the inhibition to gas-phase ignition. As the gap size increases, the critical blowout velocity decreases, but the micro-combustor becomes more resistant to extinction. A higher equivalence ratio increases the critical blowout velocity. As to the thermal properties, increasing the wall thermal conductivity or decreasing the effective heat loss coefficient increases the critical blowout velocity, suggesting the importance of thermal management in the design and operation of catalytic micro-combustors.