Geometric optimization for low-degradation film-cooling holes at the leading edge of turbine blades

Existing designs for film cooling of turbine blades mainly focus on higher cooling effectiveness, ignoring the performance degradation during actual operation. This oversight can reduce the lifespan and lead to insufficient design reliability. To handle this issue, the conjugate heat transfer method was employed to investigate the impact of geometric deviations of film holes on cooling effectiveness at the leading edge. An optimized design method for the geometric parameters of film holes, aimed at minimizing cooling effectiveness degradation, has been developed. Using Sobol sensitivity analysis, the study revealed that the upper deviation in the hole diameter had a dominant effect on both cooling effectiveness and its degradation, accounting for 57.1 % and 70.2 %, respectively. The deviation in flow direction angle and spanwise angle, when acute, significantly simplified the optimization process. After attenuation, the diameter of the original blade decreased, and the film experienced reverse flow. This led to a sharp reduction in cooling effectiveness, with the area-averaged temperature increasing by 20.2 K. Following optimization, the design diameter of the film holes was reduced in advance, leading to minimal changes in the diameter after attenuation. By optimizing the angles, the film coverage was improved, achieving a compensation effect on the cooling performance. During the optimization process, the total pressure of internal cooling chamber was monitored, and the absolute value was always less than 2 %. As a result of the optimization, the sensitivity of the leading-edge cooling performance to the geometric deviations was reduced, and the overall cooling effectiveness decay rate was lowered by 44 %. The optimization approach enables the fine-tuning of blade design, ensuring long-term reliable operation.