Interaction of Reactive Gas Flows and Ceramics at High Temperature - Experimental Methods for the Measurement of Species Recombination during Planetary Entry.

摘要

During the atmospheric re-entry phase of aerospace vehicles, several physico-chemical phenomena taking place on the hot parts (nose cap and wing leading edges) can lead to an important excess of heating and possible damage of the protective materials. The determination of the atomic oxygen recombination at the surface of different sintered ceramic materials at high temperature under low air pressure plasma has been realized in the MESOX set-up (Moyen d Essai Solaire d OXydation) using a multi-scale approach. At the mesoscopic scale, the thermal method is based on a heat balance on materials under air and argon plasmas. This approach leads to the determination of the temperature increase due to the catalytic recombination of atomic oxygen and to the evaluation of the thermal flux of recombination transferred to the surface. Thermal fluxes of recombination have also been calculated from heat balance with a one-dimensional hypothesis. Catalytic activities for the different materials move weakly between 1000-1400 K, except for Al2O3 for which recombination fluxes vary strongly and reach a maximum at 1400 K. A heat transfer modelling at high temperature has been developed in order to identify the absorbed microwave flux and finally the thermal flux of recombination and, also, to precise the validity of the experimental assumptions. The catalytic scale is confirmed by using the bi-dimensional modelling and give more accurate values of the thermal flux of recombination particularly for temperatures lower than 1400 K. These data are very useful for the calculation and design of the planetary entry of hypersonic vehicles and for comparison with results obtained by indirect methods on arc-jet or plasmatron facilities.