Experimental Study of Surface Roughness Effect on Oxygen Catalytic Recombination

Abstract

The effect of surface roughness on a catalytic phenomenon has been experimentally investigated. The test gas considered was a mixture of 21% oxygen and 79% argon by volume. The surface heat-transfer rate at the shock tube end wall was measured using a thin-film gauge. The surface of the test model was coated with silicon dioxide. Three different levels of surface roughness of the test model were prepared. Prior to testing, the surface roughness of the test samples was determined using atomic force microscopy, thus characterizing the initial condition. The heat-transfer rates of the rough surfaces were approximately 11% to 25% higher than those of the smooth walls, where the root-mean-square roughness of the rough walls were higher than those of the smooth walls approximately by a factor of 2–6.5. The oxygen catalytic recombination efficiency was determined by evaluating the measured heat-transfer rates and by the existing theory based on binary gas mixtures. It was found that with the increase in the level of surface roughness, the catalytic activity at the surface is increased.