Influence of hole blockage caused by thermal barrier coatings on the turbine vane endwall film cooling performance

Thermal barrier coating (TBC) is extensively employed to protect hot components in modern gas turbines due to its high thermal resistance. Laser spraying is used to apply ceramic coating powder onto the target surface. However, when coating the junction region between the endwall and vane, the angle of the sprayer cannot face the surface directly. As a result, excessive spraying in a specific direction will result in hole blockages. Such blockages can disrupt cooling jet outflow, impacting downstream film cooling performance. This study investigated the adiabatic effectiveness of turbine nozzle guide vane endwalls, considering hole blockages. The experiments utilizing pressure sensitive paint (PSP) technique and simulations were both conducted, and the numerical turbulence model was validated. For a turbine cascade vane endwall, the blockage mainly occurred on the film holes near the boundary. These blockages significantly altered film flow direction, and increased the cooling jet momentum. For the endwall with cylindrical holes, the impact of blockages on the endwall cooling performance varied with blowing ratios. For the endwall with fan-shaped holes, blockages enhanced the cooling performance. In contrast, blockages reduced the cooling performance of endwall with converging slot holes.