Experimental Methodology to Assess Atomic Recombination on High-Temperature Materials

Abstract

An experimental methodology to quantify atomic recombination on high-temperature materials exposed to homonuclear diatomic gases is proposed. Candidate materials are tested in a plasma wind tunnel driven by an inductive plasma generator, providing highly dissociated flows. The reconstruction of the flowfield around the tested specimens is accomplished by adequate characterization of the free flow during experiments and supported by a Navier–Stokes solver for nonequilibrium flows developed at the Institute of Space Systems. Recombination coefficients are obtained from an iterative approach in which the numerically reconstructed boundary layer and the respective simulated heat flux balance the experimental measurements. This work focuses not only on the procedure of extracting catalytic properties of high-temperature materials but it also emphasizes the influence of atomic flux on recombination coefficients. From the investigation under constant wall temperature and variations of the impinging atomic flux, the dependency of the recombination coefficient on the latter could be extracted. Moreover, it can be observed that Langmuir–Hinshelwood mechanisms are dominant as compared with Eley–Rideal mechanisms. One of the outlooks of this work is the possibility of fitting complex catalytic models such as finite-rate models as soon as variations of both surface temperature and atomic flux are considered.