Uncertainty quantification analysis of fan-shaped cooling holes considering internal blockage/roughness

Internal blockage and roughness can be observed within film holes on turbine blades after manufacturing and prolonged service. These two types of internal damage typically occur simultaneously, collectively contributing to the degradation of film cooling in aero-engines. The interaction mechanisms between blockage and roughness are complex, and identifying the dominant damage type responsible for cooling degradation is essential for mitigating structural damage and maintaining high cooling effectiveness. Therefore, this study conducts a comparative analysis of these two types of internal damage using fan-shaped holes. Furthermore, uncertainty quantification analysis is introduced to provide statistical insight into the cooling performance variations and respective contributions of each damage type under their combined effects. The study adopts numerical simulations, with film cooling effectiveness measured under identical conditions using pressure-sensitive paint to validate the turbulence model. Results show that internal blockage and roughness alter the baseline flow field through increased jet velocity at the hole exit and enhanced velocity nonuniformity, respectively. At a blowing ratio of 0.5, the impact of internal damage on film cooling is minor, but the effect intensifies with increasing blowing ratio. Uncertainty quantification analysis using polynomial chaos expansion reveals that the combined effects of internal damage lead to high standard deviation regions near the spanwise sides of the hole exit. Sensitivity analysis using Sobol indices confirms the dominant influence of internal blockage on the film cooling performance of fan-shaped holes. However, the contribution of internal roughness rises steadily with blowing ratio.