Thermal Effect of Surface Catalysis in Subsonic Dissociated-Air Jets. Experiment on a High-Frequency Plasmatron and Numerical Modeling

Abstract

Experiments on heat transfer in subsonic dissociated-air jets are performed on 100 kW VGU-4 induction plasmatron. The heat fluxes to the water-cooled surfaces of copper, silver, tantalum, beryllium, niobium, gold, molybdenum, and quartz are measured at the stagnation point on a cylindrical flat-nosed model, 50 mm in diameter, having rounded edges at 50 and 100 hPa pressures in the low-pressure chamber and the high-frequency (HF) generator power of 30 to 70 kW. At the same pressures and the HF generator powers of 45 and 64 kW the convective heating of a specimen of sintered silicon carbide is studied in the surface temperature range from 1720 to 1910 K. The predominance of the surface catalyticity effect on the heat flux with respect to nitrogen and oxygen atom recombination is demonstrated. Under the experimental conditions the air plasma flow in the discharge channel of the plasmatron, the subsonic jet flow past the cylindrical model, and the heat transfer to the stagnation point on the model are numerically simulated. Basing on the comparison of the experimental and calculated data on the heat fluxes to the surfaces of metals (Tw = 300 K), quartz (Tw = 572–722 K), and silicon carbide (Tw = 1720–1910 K) the quantitative catalyticity gradation of the materials considered with respect to heterogeneous recombination of nitrogen and oxygen atoms is established.