Investigation of film cooling effectiveness and enhancement of cooling performance
Advanced gas turbines are designed to operate at increasingly higher inlet temperatures to increase efficiency and specific power output. This increase in the operating temperature is enabled by advances in high-temperature resistant materials such as super alloys and thermal-barrier coatings (TBCs) and by the development of effective cooling methods that lower the temperature of all surfaces that come in contact with the hot gases. Since the lower-temperature air used for cooling is extracted from the compressor, efficiency considerations demand effective cooling with minimum cooling flow;This study focuses on film cooling with a twofold objective. The first is to examine the effects of TBC blockage and surface roughness on film-cooling effectiveness. The second objective is to explore, develop, and evaluate more efficient film-cooling methods. This study is accomplished by using second-order accurate computational fluid dynamics (CFD) analyses of the "compressible" Navier-Stokes equations in which the details of the film-cooling geometry and relevant flow features are resolved. To ensure that the solutions generated are meaningful, a grid-sensitivity study was performed for each configuration examined. Also, a validation study was performed to assess the turbulence models used.