Numerical investigation on the effect of upstream ramps on film cooling performance with compound angles

This paper presents a numerical investigation on the concept for improving film cooling performance by placing a ramp upstream the film hole with compound angle. Eight cases with different geometry models are investigated, including the compound angles of 15°, 30°, 45° and the distances between the upstream ramps and film holes (upstream distances) of 5 mm, 10 mm, and 15 mm. The effect of compound angle and upstream distance on film cooling performance is studied. The cases of film cooling on a flat plate, film cooling with compound angle, and film cooling with an upstream ramp are also presented as a contrast. The film cooling performance is evaluated at the density ratio of 0.97 with the blowing ratios ranging from 1.0 to 2.0. Results obtained show that the film cooling performance with compound angle is greatly improved by the upstream ramp, especially in the region downstream the film hole. Both the entrainment of coolant and modified kidney vortices are observed in the case of the novel geometry. The film cooling performance is greatly improved by the dual effect of coolant entrainment and modified kidney vortices. In addition, the film cooling performance is influenced by compound angle and upstream distance. With the increase of compound angle, the lateral adiabatic cooling effectiveness rises. With the increase of the upstream distance, the lateral adiabatic cooling effectiveness goes down.