Coupled effects of film-hole geometry and thermal barrier coating application on overall thermal performance

Advances in coating deposition technologies enable localized application of thermal barrier coatings (TBCs) around film holes, allowing the coating distribution to be coordinated with the film-hole geometry. This approach provides a practical means of integrating film cooling and thermal insulation with limited additional manufacturing complexity. In this study, numerical simulations were employed to investigate the flow characteristics and film coverage effectiveness of various hole configurations under different blowing ratios. Comparisons with experimental data on overall cooling effectiveness reveal that, under the coupling effects of solid conduction and radiation, the heat transfer through the exposed substrate is noticeable in both the transverse trench and the sine-wave-shaped trench. Consequently, neither configuration achieves the expected cooling performance predicted by the adiabatic assumption. Evaluating cooling performance based solely on the adiabatic assumption fails to accurately reflect the true thermal state of high-temperature models, and may even lead to deviations in cooling system design. The overall thermal performance is governed by the combined effects of film cooling and TBC insulation. For the standard cylindrical-hole configuration, the insulation effect of the TBC exhibits strong spatial dependence. In regions with weak film coverage, increasing the TBC thickness increases the conduction resistance and reduces heat transfer from the mainstream to the substrate. In regions with strong film coverage, however, a thicker TBC can impede heat dissipation from the substrate toward the low-temperature surface. These results demonstrate that the influence of TBC thickness depends strongly on the local film cooling intensity and heat transfer state.