Interaction of rotating instabilities and stall in axial compressors

该项目的重点是旋转不稳定(RI)，这是轴流压气机中的一种预失速不稳定。参考自己最近的实验和数值研究，RI的物理机制需要反映在一个通用的模型上。在系统简化必要边界条件的基础上，在扰动沿圆周传播的环形空间中产生开尔文-亥姆霍兹不稳定性。之后，将使用已建立的识别RI的分析方法来研究由开尔文-亥姆霍兹不稳定性引起的压力波动。为了扩大参数的范围，将研究来自上游叶片排的周期性尾迹对阻力形成的影响。具体地说，主要目的是分析特定激励频率对频谱、模式和时间分辨RI特性的影响。在多学科的方法中，通过有针对性地调整叶片数量来可能影响RI也将在叶轮机械的气动弹性领域提供巨大的科学益处。众所周知，阻力系数可能是叶片振动不同步的原因之一。此外，还将在RI的附加影响下研究旋转失速的极短时间起始过程。将澄清RI是否刺激失速细胞的发育，以及在这一过程中涉及哪些驱动机制。在此背景下，将分析国际扶轮与众所周知的初始机制之间的相互作用，如“尖峰”或“模式”。这一结果对旋转失速的研究有很大的潜力。在过去的几十年里，国际扶轮是活跃但也有争议的讨论的一部分。即使是“旋转不稳定”一词也被社区的一些人认为是不恰当的。因此，拟议的项目支持将RI明确归类为“压气机不稳定”和“失速起始”领域。

The proposed project focuses on Rotating Instability (RI), which is known as a prestall instability in axial compressors. Referring to own recent experimental and numerical investigations, the physical mechanism of RI needs to be reflected on a generic model. Based on a systematical reduction of necessary boundary conditions, a Kelvin-Helmholtz-Instability is to be generated in an annulus where the disturbances propagate circumferentially. Afterwards pressure fluctuations being induced by the Kelvin-Helmholtz-Instability will be investigated using established analysis methods for the identification of RI. In order to extend the scope of parameters, the impact of periodical wakes coming from an upstream blade row onto the formation of RI will be investigated. In detail, the main objective is to analyze the influence of specific excitation frequencies on spectral, modal and time-resolved RI characteristics. In a multidisciplinary approach, a possible influence of RI through a targeted adjustment of the number of blades would also provide a great scientific benefit in the field of aeroelasticity of turbomachinery. It is known that RI can be one of the reasons for non-synchronous blade vibrations. In addition, the extremely short-timed inception process of rotating stall will be investigated under the additional influence of RI. It will be clarified whether RI is provoking the development of stall cells and which driving mechanisms are involved in this process. In this context, the interaction between RI and well-known inception mechanisms such as "spikes" or "modes" will be analyzed. The results have great potential to contribute significantly to the subject of rotating stall inception. Over the last decades the topic RI is part of lively but also controversial discussions. Even the term "Rotating Instability" was considered inappropriate by parts of the community. Thus, the proposed project supports an unambiguous classification of RI into the field of "compressor instabilities" and "stall inception".