利用空气幕冷却提升涡轮叶栅端壁 气膜冷却有效度的实验研究

Due to circumferential pressure gradients and complicated secondary flows, pressure-side regions of turbine endwalls are one of the most difficult-to-cool regions. This study aims to solve this cooling problem by placing two rows of discrete film holes in the upstream region of the endwall passage inlet near the pressure side to obtain curtain cooling with unique cooling characteristics. A pressure sensitive paint(PSP)technique was implemented to examine film cooling patterns of curtain cooling over the endwall surfaces and its effects on discrete film injection within the passage in detail. Furthermore, an optimized endwall film cooling scheme was obtained by applying curtain cooling to the endwall. The experimental results reveal that curtain cooling has quite different cooling patterns compared with discrete film cooling within the passage. The curtain cooling was slightly influenced by the pressure gradients circumferentially across the endwall passage, resulting in efficient cooling for the pressure-side region and even for the endwall passage throat and its downstream regions. Increasing coolant rates enhances film cooling effectiveness for curtain cooling and improves film cooling performance of the discrete film holes within the endwall passage. The optimized cooling scheme improves film cooling effectiveness over the endwall by 33% relative to a baseline cooling configuration. Additionally, flow structures at the vane cascade exit demonstrate that the optimized cooling configuration reduces the cascade aerodynamic losses, somewhat.