动叶尾迹扫掠下静叶角区失速与压气机旋转失速的关联性探索研究

Hub-corner stall and rotating stall are two different but closely related “stall” phenomena in compressors. Hub-corner stall means the large reverse flow with a separation vortex in the compressor hub-corner region with increasing loading (inlet incidence angle). Rotating stall represents that a low total-pressure region located in one or several blade passages rotates along the rotor with a different speed in the circumference. In some cases, the two stall flows coexist and influence each other in a compressor at the near-stall operating point. Although the studies of the two stalls are fruitful, most researches were conducted in an isolated compressor rotor or cascade. Therefore, the link between the two phenomena and their influence on compressor stability are not clearly clarified. In this project, the relationship between hub-corner stall and rotating stall will be investigated in detail through deeply collaborating with the German partner. The research target is a small single-stage high-loaded compressor. The research contents include: (1) The Detached-Eddy-Simulation of the unsteadiness and flow structure of separation flow in the hub-corner stall region of the stator under the upstream rotor wake boundary condition; (2) Clarify the unsteady interaction mechanism between hub-corner stall and tip clearance flow; (3) Investigate the relationship between hub-corner stall and rotating stall during the throttling process up to the stall limit of the compressor, and further explore how the two stalls together affect the compressor stability.

叶片根部的角区失速和压气机的旋转失速是两个既相互关联又根本不同的内部流动失稳现象。在角区失速中，“失速”指的是随着来流攻角的增加，角区分离骤然加剧，出现旋风状漩涡的现象；而在旋转失速中，“失速”指的是圆周中某一个或数个局部的叶片通道出现随着转子的转动以不同于转子转速的速度沿圆周传播的低总压区。由于都使用“失速”这个词且很多情况下它们紧密关联，所以两类失速的关系，以及二者对压气机稳定性的影响极易混淆。本项目拟对静叶根部角区失速与动叶旋转失速的关联特性进行探索，通过与德国伙伴合作，以单级高负荷压气机为对象，开展三个方面的研究：借助DES研究动叶尾迹扫掠下静叶根部角区失速机制；结合实验分析角区失速分离与叶顶间隙流的非定常作用机制；澄清两种失速的关联特性及其对压气机失稳途径和稳定性的影响机理。这些工作的完成不仅能完善对压气机失稳机理的认识，还可为提出兼顾两类失速流动的扩稳新方法提供参考依据。

压气机静叶叶片根部的角区分离/失速和起始于动叶通道顶部的旋转失速现象是两个相互关联又根本不同的内部流动失稳现象。本项目为澄清静叶根部角区分离/失速特征及损失机制，探索角区分离/失速与动叶旋转失速和稳定性的关联特性，开展了一系列研究，共发表中英文学术论文16篇（其中SCI论文7篇、EI论文6篇），项目成员先后获AFMC Young Engineer Award、国家优秀青年基金、中国科学院青年创新促进会优秀会员、国家奖学金、中科院三好学生等荣誉。主要研究成果包括：（1）在数值模拟工具开发方面，基于OpenFoam平台开发面向工程应用的基于DES模型的RANS/LES混合方法数值计算求解器，研究了适用于叶轮机械流动精确捕捉的最优DES模型；（2）在静叶角区分离/失速及损失机制方面：建立了能够精细刻画叶片端区分离涡空间结构并定量预测损失分布的熵产率模型，提出了针对特定区域积分熵产损失的损失量化评估方法，发展形成了“当地损失机制分析—积分损失定量预测—流动损失定向控制”的静叶角区分离/失速流动控制方法设计方法；（3）在静叶角区分离/失速与旋转失速关联性方面：揭示了不同静叶负荷和不同动叶尾迹扫掠强度对静叶角区分离/失速流动结构和损失机制、角区分离/失速与叶顶泄漏流耦合作用机制和旋转失速途径的影响规律。结果表明，通过减小静叶稠度加剧静叶角区分离强度和损失，并不影响压气机失稳工况点对应的流量和旋转失速途径。通过机匣处理调控动叶扫掠尾迹，叶顶泄漏流强度减弱会导致静叶轮毂侧角区分离加强，拓宽失稳边界，但不影响压气机的旋转失速途径。以上研究工作澄清了静叶角区分离/失速与导致压气机进入失稳边界的旋转失速现象之间的关联特性，完善对压气机失稳机理的认识，也为角区分离/失速流动控制方法设计提供了依据和方法。