The maximization of rapid fuel-air mixing is one of the essential issues for the efficient operation of scramjet engines. A delta wing with its height being 6mm is located ahead of the injector to enhance the mixing process between the injectant and air in the supersonic flow with the freestream Mach number being 3.75, and the influence of the distance between the delta wing and the injector on the mixing efficiency is evaluated numerically, as well as the effect of the jet-to-crossflow pressure ratio. At the same time, the predicted results obtained in the three-dimensional transverse injection flow field are compared with the available experimental data in the open literature, and the grid independency analysis is conducted as well. The obtained results show that the mixing efficiency increases with the decrease of the jet-to-crossflow pressure ratio, and this conclusion is consistent with that obtained in the transverse injection flow field. The predicted wall static pressure distributions show reasonable agreement with the experimental data, and the grid scale has only a slight impact on the predicted results. Further, it is observed that the mixing efficiency increase with the decrease of the distance between the delta wing and the injector, and the hydrogen penetrates deeper into the core flow when the distance is smaller. Accordingly, the plume area is larger. This illustrates that the transverse jet flow field is affected by the vortex generated by the delta wing, and the mixing process is enhanced. The maximum mixing efficiency at x = −350mm is nearly 0.84 in the range considered in this paper.

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