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首页> 外文会议>International Symposium on Fluid Machinery and Fluid Engineering(ISFMFE); 20041201-03; Beijing(CN) >PIV FOR UNSTEADY SEPARATED FLOW IN AN ANNULAR CASCADE
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PIV FOR UNSTEADY SEPARATED FLOW IN AN ANNULAR CASCADE

机译：PIV用于环形阶梯中的非定常流动

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摘要

To study unsteady-fluid characteristic of inner flow in fluid machines is very important for reducing losing and enhancing lift force. In an annular cascade, when incidence angle changed, separation and vortex may happen. Under the designed incidence, separating section is narrower and blended with main fluid quickly. When the incidence angle decreases greatly, wider separating section, and stronger vortex appear. Similar phenomenon happens when incidence angle increases to a big positive value, expect that the vortex intensity is higher than that of the former. Experiment with pressure probe shows that aerodynamic performance of the annular cascade would be improved obviously by adding proper external acoustic excitation. In order to develop an in-depth study on configuration and characteristic of separate flow and effects of external unsteady excitation, PIV (Particle Image Velocimetry) and numerical simulation are used to analyze the inner flow field through an annular cascade. Tests have been taken under different incidence cases in the tested range, with and without external acoustic excitation. The distribution of flow velocity, streamline and vorticity are obtained. Other important parameters like circumferential velocity, turbulent kinetic energy can be calculated from the original experimental data. Obvious difference of separation configuration due to different incidence angle can be seen from the results. And, when proper external acoustic excitation added, vorticity and separating section in the tested range decreases obviously. Moreover, numerical simulation using k-e turbulence model and Large-eddy simulation for the same cases are also made. Compared the calculation result with that of the PIV experiment, detailed configuration of separate flow in the annular cascade can be found. Such work may offer some ideas on how to control separation and optimize designs.
机译：研究流体机械内部流动的非稳态流体特性对于减少损失和提高升力非常重要。在环形叶栅中，当入射角改变时，可能会发生分离和涡旋。在设计的入射角下，分离段较窄并与主油快速混合。当入射角大大减小时，分离区域变宽，涡旋变强。当入射角增大到较大的正值时也会发生类似的现象，并期望涡旋强度高于前者。压力探头的实验表明，通过增加适当的外部声激励，可以明显改善环形叶栅的空气动力学性能。为了深入研究分离流的构造和特性以及外部非稳态激励的影响，使用了PIV（颗粒图像测速）和数值模拟来分析通过环形叶栅的内部流场。在有或没有外部声激励的情况下，已在不同的入射情况下进行了测试。得到了流速，流线和涡度的分布。其他重要参数，例如圆周速度，湍动能，可以从原始实验数据中计算得出。从结果可以看出，由于不同的入射角，分离结构明显不同。并且，当添加适当的外部声激励时，在测试范围内的涡度和分离截面明显减小。此外，在相同情况下，还进行了使用k-e湍流模型的数值模拟和大涡模拟。将计算结果与PIV实验的结果进行比较，可以找到环形叶栅中单独流动的详细配置。此类工作可能会提供一些有关如何控制分离和优化设计的想法。

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