Direct numerical simulation of catalytic combustion in a meso-scale channel with non-planar walls

Abstract

Catalytic combustion of natural gas has a growing interest to improve the flame stability and conversion efficiency in microcombustors. In automotive industry, the improvement of the efficiency of catalytic after-treatment systems are one solution to reduce drastically pollutant emissions. These devices present a honeycomb shape which consists in a grid of millimeter-scale narrow channels whose interior walls are coated with precious metals presenting catalytic properties. Fuels or pollutants are converted through the chemical interactions involving gas-phase molecules and catalytic sites. In order to promote transfers, obstacles can be introduced inside the channels. The numerical simulation is mandatory to help understanding and mastering the underlying phenomena. In the present study, a numerical methodology is proposed to couple surface kinetics and gas phase chemistry with boundary conditions accounting for momentum, heat and mass transfers in order to take into account the interactions between the flow and heterogeneous reactions. Numerical simulations are then performed on the experimental configuration by Dogwiler et al. which consists in lean premixed CH4/air mixture igniting in a Pt-coated meso-scale channel with flat walls. The validated numerical methodology is then applied to explore the impact of introducing wall obstacles and segmented coating on the anchoring position of the flame and fuel conversion rate.