旋转状态收敛缝形气膜孔的冷却特性

Film cooling plays a very important role in the cooling configuration of the modern gas turbine engines, of which the core problem is how to reduce the penetration of film outflow to primary flow and enhance the extensibility of film outflow along primary flow direction. The key factor for film cooling characteristic is the interaction between film outflow and mainstream. The film outflow from converging slot hole is of inherent feature owing to its special internal flow passage under stationary condition, which forms a pair of vortices that is opposite to the kidney vortices. The alteration of vortice rotation direction makes the film with higher extensibility along streamwise direction and prevents the primary flow from invading to the local area between film holes. Based on this research background, the converging slot hole (console) film cooling configuration at rotation condition was numerical studied in the present paper to further understand the interaction between film outflow and primary flow, and reveal its physical mechanism for enhancing cooling characteristic, and get the difference characteristics of vortex between stationary and rotation, and arrange the effects of aerodynamic conditions (including revolution, blowing ratio and mainstream Reynolds number) and curvature conditions on vortex structure and film cooling effectiveness characteristic with console hole.

气膜冷却在现代航空涡轮发动机热端部件的冷却结构中具有十分重要的作用，其核心问题在于降低冷气出流穿透率，以及增强气膜的延伸能力等。气膜出流与主流的相互作用，则是影响冷却特性的关键点。静止状态下，收敛缝形孔的固有流道特性使气膜出流形成与肾形涡旋向相反的涡对，此涡对的存在提升了气膜出流向下游的延伸能力并且有效地抑制了冷气向主流的穿透。本申请拟对旋转状态下收敛缝形孔气膜出流开展详细的数值研究，揭示气膜出流与主流的相互作用规律及其强化冷却的物理机制，得到旋转效应下收敛缝形气膜孔的涡结构特征，揭示旋转和静止条件下冷却特性的本质区别；归纳整理气动参数（转数、吹风比、主流雷诺数）和转子叶片曲率对收敛缝形孔涡结构、气膜冷却特性的影响规律，为涡轮转子叶片的高效冷却增强技术储备。

气膜冷却在现代航空涡轮发动机热端部件的冷却结构中具有十分重要的作用，其核心问题在于降低气膜出流向主流的穿透、增强孔间覆盖和气膜出流向下游的延伸能力等。本项目以此为研究背景，对旋转条件下收敛缝形气膜孔结构的冷却特性开展了数值研究。研究内容主要为：针对收敛缝形气膜孔的冷却结构，通过改变转速、吹风比及主流雷诺数等条件，研究其冷却特性的变化规律，并与圆形气膜孔的冷却特点对比分析，得到其改善气膜冷却效率的特性。研究结果表明：旋转时收敛缝形气膜孔的冷气整体会发生偏移，且随着转速的增加，偏移现象愈加明显，同时冷气的偏移，使得收敛缝形孔展向区域的气膜覆盖增多，增强了展向的冷却效果和均匀性，而流向上造成下游气膜延伸性的下降；旋转时叶片压力面处的冷却流体在较强的科氏力作用下，偏移朝着向心方向，而吸力面的偏移则朝离心方向；收敛缝形孔在旋转时保持较好的气膜贴壁性，冷却效率随吹风比和主流雷诺数的增大而提高；旋转条件下，收敛缝形孔依然可以形成与圆形孔肾形涡对旋向相反的涡对，此涡对可将冷气带至壁面从而形成较好的气膜覆盖，故收敛缝形孔在展向气膜覆盖的均匀性和沿流向气膜的延展性均优于圆形孔。