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Simulant Gas Test Technique Feasibility

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Final rept. Dec 1988-Jan 1990

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The uncertainty engendered by non-equilibrium air effects on hypersonic vehicle aerodynamics and heat transfer is compounded by the fact that such effects are difficult to validate in ground test facilities. Laboratory quality ground test data on air chemistry effects are clearly needed to investigate the rich parametric effects of scale, complex geometry, turbulence coupling, and altitudeMach number flight regime. Moreover, data is needed for numerical model validation purposes. A proposed concept for such a test, referred to as the Simulant Gas shock tunnel test, is investigated in the present report. The approach is based on the use of simulant gas mixtures in a shock tunnel operating in the nonreflected shock mode. Simulant gases are sought which react at lower temperatures than oxygen and which have a relatively well defined ignition temperature. They thereby provide the possibility of remaining unreacted in the freestream of the expanded shock tunnel flow while reacting at representative and controllable rates in the shock layer of a test model. The test concept, if feasible, would provide a laboratory quality experimental simulation technique which possesses reactive flow similitude relative to oxygen dissociation at hypersonic flight conditions. The feasibility of the simulant gas test concept was evaluated by performing reactive flow scaling and reactive streamline flow analyses for a limited range of combustible gas mixtures. The method is illustrated for air by defining flight regimes and baseline shock tunnel test regimes for which nonequilibrium oxygen dissociation is operative in the vehiclemodel shock layer.

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  • Fluid Mechanics

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