Experimental and numerical study of oxygen catalytic recombination of SiC-coated material

Abstract

A combined experimental and numerical approach has been proposed to study the oxygen catalytic recombination coefficient of SiC-coated material for two different types of surface condition: roughened and pre-heated. For the experimental approach, the shock tube facility, which test gas consists of 21% oxygen and 79% argon by volume, is utilized to measure the oxygen catalytic recombination coefficient at near-room surface temperature. The coefficient is deduced from the local heat transfer measurement at the end-wall model of the shock tube via catalytic boundary layer theory. The experimental data indicated that the coefficient for the SiC-coated material varied between 0.0024 and 0.01, depending on the surface condition. The results suggested that even at low surface temperature, both the level of surface roughness and the oxidation due to the pre-heating should be considered carefully for the atomic recombination process. For the numerical approach, the finite rate catalytic modeling is elaborated in detail. The modeling is conducted to better understand the physical interaction for the recombination mechanism. Given the surface reactions considered in the modeling, the catalytic recombination coefficient was not significantly affected by the pressure at low wall temperature. Conversely, the variation in the coefficient was observed to be dependent on the activation energy and the number of active site concentrations at the surface.