Effects of mainstream cross-flow and wall contouring on film cooling effectiveness of cylindrical-holes embedded in elliptical craters

Abstract

The combined effects of the dominated flow parameters at contoured end-wall and the geometrical parameters of elliptical-crater on the cratered-hole film cooling performances and flow mechanisms were investigated experimentally and numerically. Seven cratered-holes were designed to demonstrate the individual and combined influences of the position and size of crater. The original cylindrical-hole was selected as the baseline model. Three test passages were built up to simulate the flat-plate environment, the mainstream cross-flow environment and the environment with mainstream cross-flow coupled by wall contouring, respectively. Under blowing ratio (BR) from 0.25 to 2.0, the surface film effectiveness was measured using infrared thermography technique, and the in-plane scalar transport characteristics were captured by the concentration visualizations, as well as the flow interactions were displayed by the numerical simulations. The comparisons of results revealed that the benefit of crater on the film effectiveness enhancement depends on the contradictory of the crater configuration requirements, bringing to the huge challenge of fine design. The mainstream cross-flow causes the new mechanisms for the cratered-hole film cooling, presenting a new requirement for the design of crater-configuration. Compared to the flat-plate environment, the cratered-hole can improve 20% in film effectiveness under the solo mainstream cross-flow effect. Further adding the wall contouring can improve the uniformity of film coverage and weaken the sensitivity to crater-configuration, while reduce by 40% in the benefit of crater on film effectiveness improvement. The local cooling deterioration under the low flowrates of cooling air results in the combined application of cratered film cooling and end-wall contouring being undesired.