Film cooling performance and heat transfer over an inclined film-cooled surface at different convergent angles with respect to highly turbulent mainstream

Experiments have been performed to study and obtain the adiabatic-wall film cooling effectiveness and the heat transfer over a film-cooled surface that is made inclined at various angles with respect to a highly turbulent flow. The film-cooled air is injected from a tangential slot. The normal temperature distributions were measured to infer the flow structure and the rate of mixing of film jet with the freestream. The freestream turbulence intensity is controlled to range from 1.0% to 26.4%, the inclination or the convergent angle of the film-cooled surface ranges from 0° to 20°, the blowing parameter from 0.5 to 2.0. It is found that the mixing of the film jet with the freestream is significantly enhanced by both the freestream turbulence intensity and the convergent angle of the film-cooled surface, which leads to the decrease in the film cooling effectiveness and the increase in the heat transfer when the inclination angle of the film-cooled surface is not large. This is attributed to the two competition mechanisms of impinging effect and the stabilization due to acceleration of the mainstream. The normal temperature distribution at several locations along the flow direction is also measured and used to infer the flow structure of the mixing of film jet with the mainstream. More detailed discussion is presented. Correlations for both the film cooling effectiveness and the heat transfer under the film-cooled surface have been very successful and are provided.