Mixing and Combustion Enhancement in Scramjet Combustors Induced by Interaction between Vortex and Shock Wave

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In order to establish a method to evaluate relative importance of gain and loss in the available energy to be converted into the propulsive work in the scramjet combustor, we introduced a combustor performance parameter which was written in terms of the kinetic energy efficiency and the combustion efficiency. These two efficiencies in the parameter were combined in the form appearing in the equation for thrust. The combustor performance parameter was evaluated with the available experimental data for two supersonic combustors with eight fuel injection patterns, and it clarified the effects of injection pattern, combustor length, chemical reaction in the nozzle were investigated. The result showed that the optimum combustor length based on the parameter was less than a half of one estimated only from the combustion efficiency or the mixing efficiency. It was found that use of the properties of pure air instead of those of vitiated air used in the experiment may results in significantly … More different value of the performance parameter.As a typical flowfield where interaction between vortices and shock waves occurs, compressible swirling jet of over- or under-expansion condition was chosen, and mixing of such jet was experimentally investigated. At first, non-swirling jet of Mach 0.3, 1.0 or 2.0 was injected into quiescent atmosphere or heated subsonic flow. Mixing characteristics of the non-ideally expanded non-swirling jets could be well correlated with those of the ideally expanded jets when the reference values of diameter and velocity calculated with assumption of expansion or compression to ambient pressure keeping the stream thrust constant were used to non-dimensionalize the data. The swirling jet was produced by attaching a swirler in the subsonic portion of the nozzle. Mixing of the jet was slightly enhanced by increasing swirl number. In comparison with the ideal expansion jet, the potential core region of the non-ideally expanded swirling jet was shortened, but its mixing rate in the developed region was retarded. Effect of swirl on the mixing of two parallel supersonic jets were observed by flow visualization. The swirl enhanced mixing near the merging region of the twin jets. Swirl of the same direction for both jets had resulted in better mixing then that of the counter direction. Less