When axial compressors operate under high-loading conditions, inherent unsteady flow phenomena emerge in the tip region as a consequence of the tip leakage flow. These aerodynamic phenomena are collectively known as tip flow unsteadiness. It has been proven that tip flow unsteadiness not only serves as an excitation source of both non-synchronous vibration and tip noise but is also the cause of short-length-scale stall inception. These structural and aerodynamic problems have become common issues in highly loaded axial compressors, which require a breakthrough in the study of tip flow unsteadiness. This article begins with a review of past research on unsteady tip flow phenomena, examining them from the perspectives of self-excited unsteadiness and rotating instability (RI). Detailed discussions are presented on the relationships between RI and tip clearance noise, non-synchronous vibrations, and stall inceptions. This is followed by explanations for the origin of the tip flow unsteadiness. Six theories proposed in existing literature are classified, including vortex shedding, tip leakage vortex breakdown, the interaction between tip leakage flow and adjacent flow, rotating instability vortex, tip secondary vortex, and shear layer instability. There have been only limited investigations of control techniques aimed at suppressing tip flow unsteadiness. These methods are classified according to their control mechanisms and the corresponding control effects are presented. Additionally, recommendations for future advancements in these fields are presented.

中文翻译：

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轴流式压缩机叶尖流的失常空气动力学问题及控制策略综述


当轴流式压缩机在高负载条件下运行时，由于尖端泄漏流，尖端区域会出现固有的不稳定流动现象。这些空气动力学现象统称为尖端流不稳定。事实证明，针尖流的不稳定性不仅是非同步振动和针尖噪声的激励源，也是短距离失速的原因。这些结构和空气动力学问题已成为高负载轴流式压缩机的常见问题，需要在尖端流失稳性研究方面取得突破。本文首先回顾了过去对非定常尖端流现象的研究，从自激非定性和旋转不稳定性 （RI） 的角度对其进行了研究。详细讨论了 RI 和叶尖间隙噪声、非同步振动和失速开始之间的关系。接下来解释了尖端流不稳定的根源。对现有文献中提出的 6 种理论进行了分类，包括涡旋脱落、尖端泄漏涡旋击穿、尖端泄漏流与相邻流之间的相互作用、旋转不稳定涡旋、尖端二次涡旋和剪切层不稳定性。对旨在抑制尖端流动不稳定的控制技术的研究有限。根据其控制机制对这些方法进行分类，并给出了相应的控制效果。此外，还提出了对这些领域未来发展的建议。