Assessment of the effect of thermal barrier coating blockage on film cooling effectiveness: An experimental study of full-coverage turbine vane

The improved performance of turbine blades leads to increased temperature loads, thereby necessitating higher design standards for heat protection. Thermal barrier coating (TBCs) and film cooling are the predominant technologies employed for blade cooling. However, the application of thermal barrier coatings through spraying inevitably modifies the structure of film holes, resulting in deviations from the original design in film cooling. In this study, numerical calculations are used to examine the impact of TBCs blockage on coolant mixing and flow mechanisms in the film holes at typical locations on the vane surface. Additionally, models with actual engine vane dimensions were developed, and the full-coverage film cooling effectiveness (.) vanes with and without TBCs were measured using Pressure-sensitive paint (PSP). The results indicate that the impact of TBCs blockage on the cooling characteristics of cylindrical holes is more pronounced than that of laid-back fan-shaped holes. The TBCs blockage leads to a redistribution of coolant, causing a greater tendency for the coolant to flow out from the hole rows on the suction surface in the tested vane. This results in higher eta on the suction surface for the vane with TBCs compared to the vane without TBCs, with a maximum increase of approximately 16.7%. For the other regions of the vane, TBCs spraying significantly reduced eta at the leading edge of the vane (with a maximum reduction of approximately 52%) and slightly reduced eta at the pressure surface for other regions of the vane (with a maximum reduction of approximately 7%). The application of TBCs reduces the uniformity of film coverage on vane surfaces, with a maximum reduction of approximately 22.5%.