Effects of Feeding Pressures on the Flowfield Structures of Supersonic Film Cooling

Schlieren and shadowgraph visualizations of flowfields in a typical configuration of supersonic film cooling in a backward-facing slot were conducted in a Mach 2.95 continuous-suction wind tunnel, with the film gas tangentially ejected through a half-Laval nozzle of Mach 1.5. The flowfields after the step without and with the injection of film coolant were measured in the paper, including the coolant delivery pressures in the matched and unmatched conditions with the mainstream, respectively. The effects of the different injecting pressures of film coolant on the flowfields in these conditions were also analyzed. A clear visual image of the flowfields of supersonic film cooling in a backward-facing step was obtained, and the characteristics of the flowfields near the step were described. The results confirmed that the feeding pressure of film gas affected the flowfields after the step, especially the shock wave emanating from the upper tip of the lip and the shock wave and expansion fan from the lower tip of the lip. This work aided the verification of numerical simulation results and the in-depth understanding of the flowfields of supersonic film cooling near the backward-facing step.