Application of a 20 kW arc-heated wind tunnel to evaluation tests of wall catalysis

This paper describes the performance characteristics of a 20 kW-class arc-heated wind tunnel and the investigation of material catalysis as an application of this facility. First of all, stagnation heat fluxes and pressures are measured in high-enthalpy air and nitrogen arc jets that are generated by a constrictor-type arc heater. Total enthalpies of the arc jets are estimated based on Pope's theory. The total enthalpies are 7.5-22 MJ/kg for nitrogen and 13-19 MJ/kg for air. The operation envelope of this arc-heated wind tunnel and the applicable conditions for reentry simulation or the thermal protection tests are discussed based on the experimental results. Finally, as an application of this arc-heated wind tunnel, evaluation tests of wall catalysis have been attempted by the use of two flat-faced cylindrical models equipped with two kinds of specimens of catalytic material. The evaluation tests are composed of heat flux measurements and spectroscopic measurements. It is found that there is a certain difference in obtained heat fluxes between the two catalytic materials. Emission spectra from a shock layer formed in front of the model are measured, and wall catalysis is discussed based on the spectra measurements. The results show the existence of catalytic wall effects.