Abstract Non-Synchronous-Vibration (NSV) in high-speed turbomachinery compressors is an aeroelastic phenomenon which can have devastating consequences, including loss of rotor blades. Despite extensive research over the past two decades its underlying mechanisms are not yet understood. This paper aims to explain the physical mechanisms causing NSV in a modern transonic compressor rotor. Referring to previous experimental results and using validated computational fluid dynamics (CFD), a parametric study is performed in order to characterize the aerodynamic disturbance causing NSV, and to understand the lock-in mechanism between the fluid and the structure seen during NSV. The results show that the process is driven by aerodynamics in the tip region. Under highly throttled conditions, the tip leakage flow blocks the passage and causes the disturbance, which is characterised as a vorticity fluctuation, to propagate circumferentially in the leading edge plane. It is found that the propagation speed of the disturbance is determined by the mean flow conditions and only its phase is periodically modulated through interaction with oscillating blades. This is the mechanism facilitating lock-in. Based on these findings a semi-analytic model is developed and calibrated with the numerical results. The model is capable of simulating the lock-in process and correctly predicts unstable vibration modes.

中文翻译：

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轴流压缩机非同步振动：锁定机制和半解析模型

摘要 高速涡轮机械压缩机中的非同步振动 (NSV) 是一种气动弹性现象，会产生破坏性后果，包括转子叶片的损失。尽管在过去的 20 年中进行了广泛的研究，但尚未了解其潜在机制。本文旨在解释在现代跨音速压缩机转子中引起 NSV 的物理机制。参考先前的实验结果并使用经过验证的计算流体动力学 (CFD)，进行参数研究以表征导致 NSV 的空气动力扰动，并了解 NSV 期间看到的流体与结构之间的锁定机制。结果表明，该过程是由尖端区域的空气动力学驱动的。在高度节流的情况下，叶尖泄漏流阻塞通道并引起扰动，其特征是涡度波动，在前缘平面内周向传播。发现扰动的传播速度是由平均流动条件决定的，并且只有它的相位通过与振荡叶片的相互作用而被周期性地调制。这是促进锁定的机制。基于这些发现，开发了一个半解析模型，并用数值结果进行了校准。该模型能够模拟锁定过程并正确预测不稳定的振动模式。发现扰动的传播速度是由平均流动条件决定的，并且只有它的相位通过与振荡叶片的相互作用而被周期性地调制。这是促进锁定的机制。基于这些发现，开发了一个半解析模型，并用数值结果进行了校准。该模型能够模拟锁定过程并正确预测不稳定的振动模式。发现扰动的传播速度是由平均流动条件决定的，并且只有它的相位通过与振荡叶片的相互作用而被周期性地调制。这是促进锁定的机制。基于这些发现，开发了一个半解析模型，并用数值结果进行了校准。该模型能够模拟锁定过程并正确预测不稳定的振动模式。