Near-Wall Flow in Turbomachinery Blade Rows

在本项目中，涡轮和压气机叶栅内的近壁流动正在进行基础性的研究。关于涡轮叶栅的工作已经自然结束，但根据所取得的结果，提出了一些关于压缩机内流动的研究问题，这些问题将在两年的延续阶段得到回答，以澄清与近壁流动有关的重要应用方面。而在当前阶段，重点放在单级，特别是近壁流动结果的可转换性，从线性叶栅到旋转叶栅，并且只使用圆柱尾迹作为模型，现在将扩展到更复杂的近壁动静相互作用(RSI)。为此，在继续阶段，将完成向真实的多级压缩机的实际进气条件的过渡。一方面，通过对流线型非偏转尾迹发生器和下游转子的实验研究，以及考虑四级低速轴流压气机的第三级来实现这一点。另一方面，将进行高分辨率大涡模拟(LES)，其中专门为这些构型设计的模块设计的入口条件允许清楚地识别影响。这一有条不紊的协调程序使我们能够弄清流入中的各个流动成分对转子内的近壁流动、二次流动和损失发展的作用。通过对RSI影响下侧壁附近流动的湍流结构的详细分析，也对此做出了贡献。这是通过结合使用壁分辨LES和一种创新的测量技术--激光多普勒轮廓传感器来实现的。第三个主题涉及到到目前为止所获得的结果在非设计条件下的可转换性，在非设计条件下，预计壁面附近的RSI随着更高的气动载荷而发生显著变化。目前的结果也显示了旋转失速触发的影响，即工作范围的限制。在这里，除了其他问题外，还需要研究径向间隙宽度的影响，特别是对于大间隙。继续阶段计划的工作将详细分析受RSI影响的壁面附近的流动，并增进对基本问题的物理理解，以实现减少损失、提高效率和扩大稳定运行范围的长期愿景。

In the current project , the near-wall flow in turbine and compressor cascades is being investigated fundamentally. The work on turbine cascades has reached a natural end, but based on the results achieved, a number of research questions on flow in compressors have been raised which shall be answered in a two-year continuation phase to clarify important application-relevant aspects of the near-wall flow. While in the current phase the focus was on the single stage, especially the transferability of results for near-wall flow from linear cascades to rotating cascades, and only cylinder wakes were used as a model, this will now be extended to more complex near-wall rotor-stator interaction (RSI). To this end, in the continuation phase the transition to realistic inflow conditions of a real, multi-stage compressor will be accomplished. On one hand, this is done by experimental investigations with a streamlined, non-deflecting wake generator and a downstream rotor as well as considering the third stage of the four-stage low-speed axial compressor. On the other hand, high-resolution Large Eddy Simulations (LES) will be carried out, in which modularly designed inlet conditions specially designed for these configurations allow the effects to be clearly identified. The methodically closely coordinated procedure allows to clarify the role of the individual flow components in the inflow on near-wall flow, secondary flows and loss development in the rotor. A contribution to this is also made by the detailed analysis of the turbulence structure in the flow near the side wall under the influence of RSI. This is achieved by the combined use of wall-resolved LES and an innovative measuring technique, the laser Doppler profile sensor. The third topic is concerned with the transferability of the results obtained so far to off-design conditions, where it is to be expected that the RSI near the wall changes significantly with higher aerodynamic load. Current results also show ist influence on the triggering of rotating stall, i.e. the limitation of the operating range. Here, among other issues, the influence of the radial gap width is to be investigated, especially for large gaps. The work planned for the continuation phase will provide a detailed analysis of the flow near the wall under the influence of RSI and generate an improved physical understanding of fundamental issues, with the long-term vision of achieving a reduction of losses, increase of the efficiency and extension of the stable operating range.