Geometric evolution and cooling performance degradation of film cooling holes under long-term ablation in advanced gas turbines

Ablative deformation of film cooling holes under long-term exposure to high-temperature gas flows threatens the reliability of advanced gas turbine components. This study investigates the geometric evolution and cooling performance degradation of fan-shaped and cylindrical holes through directional ablation experiments and high-precision 3D reconstruction. A numerical approach, calibrated with a turbulent Schmidt number ( Sc _t=0.3), was employed to analyze cooling effectiveness across various momentum ratios. Findings reveal that ablation induces significant exit expansion and sidewall contraction in both hole types. The cooling effectiveness demonstrates a non-linear characteristic of "slight short-term enhancement followed by long-term degradation". Specifically, fan-shaped holes exhibited a 6.7 % reduction in effectiveness after 20 hours ( I =2.71), while cylindrical holes suffered a more severe 12.7 % degradation ( I =0.97), indicating the higher sensitivity of traditional geometries to prolonged ablation. Mechanistic studies reveal that performance decay in fan-shaped holes is predominantly governed by spanwise jet migration induced by asymmetric deformation. Conversely, cylindrical holes are compromised by an intensified counter-rotating vortex pair (CRVP) that acts as a "fluid scaffold" to trigger film lift-off. This research establishes a conservative worst-case baseline for evaluating the service life of high-temperature components and provides crucial design guidelines for ablation-resistant cooling configurations.