Composition of the test gas in the test section of a high-enthalpy wind tunnel

A method and system for sampling a chemically active gas from a hypersonic flow with high stagnation parameters are developed. Results of an experimental study of the test gas composition at the nozzle exit of the IT-302M hotshot wind tunnel based at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences are presented. As the air in the settling chamber is heated up to 3000 K by an electric arc only, the volume fraction of oxygen in the test section decreases from 21 to 18%, which may require supplying an additional amount of oxygen into the settling chamber as a compensation for its reduction in some tests of gas-dynamic models with combustion. In the case with hydrogen used together with the electric arc for increasing the energy of the facility, the degree of completeness of the reaction of hydrogen combustion in air in the settling chamber is determined. For the minimum possible supply of electric energy for the IT-302M wind tunnel (based on conditions of arc combustion stability), the hydrogen combustion efficiency is $\approx$ 0.9 for extremely lean hydrogen-air mixtures with the hydrogen concentration much lower than the flammability limits under standard conditions. The combustion efficiency rapidly approaches unity as the hydrogen concentration in the settling chamber and the electric energy supply are increased.