涡轮叶片尾缘新型扰流半劈缝的气膜冷却强化与流动损失机理研究

The trailing edge is one of the key parts in turbine blades which need to be cooled effectively. The structure of pressure side cutback with film cooling slot is widely used in the trailing edge due to its advantage in the overall performances in cooling and aerodynamics. Based on the heat transfer process analysis on the trailing edge cutback structure, a new idea of increasing the convective heat transfer coefficient on the cutback surface, which breaks the traditional way of only focusing on the film cooling effectiveness, is introduced in the present project to enhance the cutback film cooling effect for trailing edge. And a novel turbulated cutback structure is proposed for the trailing edge cooling based on this idea, which has turbulated structures on the cutback surface for heat transfer enhancement. In order to reveal the performance and related mechanism in film cooling enhancement and aerodynamic loss for this new turbulated cutback cooling structure, experimental and numerical studies will be conducted on the effects of flow-structure parameters on the film cooling characteristics, wake loss and the related flow structures. And various turbulator structures will be studied and compared to find out their influence mechanism on the film cooling and wake loss performances of turbulated cutback structures. Effective turbulated cutback cooling structures with better cooling performance can be expected through the research of this project. It will contribute to the development of advanced cooling technology for turbine blades, as well as the deep understanding on the influence mechanism of turbulators on the film cooling performance.

尾缘是涡轮叶片上需要冷却的关键部位之一，半劈缝气膜冷却结构由于其良好的冷却与气动综合性能而广泛应用在涡轮叶片尾缘上。本项目根据对尾缘半劈缝结构的传热过程分析，突破单纯增强半劈缝表面气膜冷却效率的传统做法，提出了通过增强半劈缝表面对流换热系数来提升尾缘综合冷却效果的新思路，并基于这个思路提出了一种在半劈缝壁面布置有扰流强化换热结构的扰流半劈缝新概念。为了深入揭示新型扰流半劈缝的气膜冷却强化与流动损失特性及机理，本项目采用实验测量与数值模拟相结合的方法，针对带有高效扰流强化换热结构的新型扰流半劈缝，研究流动-结构参数对其气膜冷却特性与尾迹损失的影响规律，分析不同扰流半劈缝的气膜流动与掺混结构，阐明不同扰流结构对半劈缝气膜冷却特性与尾迹损失的影响机制。本项目预期可以获得相同冷气量下冷却性能更好的新型半劈缝结构，有助于涡轮叶片新型高效冷却结构的发展以及深入认识壁面扰流结构对气膜冷却特性的影响机理。

尾缘是涡轮叶片上亟需冷却的关键部位之一，其冷却需求与气动性能对高效冷却结构的设计提出了巨大挑战。与一直追求低换热系数的叶身区域传统气膜冷却相比，尾缘区域的冷却设计追求目标是高冷却效率和高换热系数，前者可有效降低压力面侧的气流温度，后者加强压力面侧的散热能力。本课题通过对涡轮叶片尾缘半劈缝冷却结构的传热过程分析，突破单纯增强半劈缝气膜冷却效率的传统思路，提出了“扰流半劈缝”的新概念和尾缘冷却强化的新思路：借助壁面扰流结构增强尾缘半劈缝气膜对流换热强度，从而提高尾缘综合冷却效果，并基于此设计了壁面带有连续肋片和离散结构的尾缘扰流半劈缝新构型，研究结构表明，低吹风比工况下，受主流脱落涡及扰流结构扰动影响下，劈缝表面远下游区域的气膜冷却效率略有降低；随着吹风比的增大，次流涡占据主导影响，劈缝表面气膜覆盖效果与基准结构一致，壁面扰流结构的加入显著提高了壁面的换热系数和综合冷却效果；外部连续肋片及离散结构对涡轮叶片尾缘气动特性的影响较小，而内冷带肋通道在大吹风比工况下极大加剧了气动损失。.本课题首次系统地研究了内部肋片、外部肋片及离散元等扰流结构对半劈缝气膜冷却效率、对流换热系数和叶片尾缘气动特性的影响规律与机理，阐明了流动-结构参数对扰流半劈缝气膜冷却特性的影响机理，同时根据不同工况提出了相应的设计准则。研究成果有助于涡轮叶片新型高效冷却结构的发展以及深入认识壁面扰流结构对气膜冷却的影响特性与机理，可为此种新型尾缘冷却结构的工程应用提供理论指导与技术支撑。