Unsteady secondary flow in axial turbines

由于粘性尾迹和叶片的潜在影响，叶轮机械中相对运动的叶片和叶片在空气动力学上相互作用。在端壁附近，端壁边界层和二次流现象的影响进一步叠加。由于叶片排间的气动相互作用，二次流型呈周期性非定常。二次损失是叶片排和整个发动机总损失的重要组成部分。轴向涡轮非定常二次流项目是压气机和涡轮叶片排非定常二次流效应联合项目的一部分。该联合项目的主要重点是压气机和涡轮叶栅的基础实验和数值研究，以检测和描述重要的二次流效应。研究了系统参数变化对二次流效应和损失产生的非定常特性的影响。通过这些研究，将确定利用有利的二次流效应改善涡轮机械部件性能的潜力。轴流式涡轮非定常二次流项目的目的是为了提高对轴流式涡轮叶片排非定常二次流效应的物理认识。基础实验研究将揭示周期性非定常尾迹对涡轮叶片和叶片排内二次流和损失产生的影响程度。实验将在低速轴向涡轮中进行，使用两种不同的结构。涡轮1的周期性非定常尾迹是由旋转杆产生的。本文将详细研究棒状尾迹对二次流场和后续定子损失的影响。对于涡轮构建2而不是旋转杆涡轮转子叶片排将被使用。这些研究的重点是实际转子尾迹对定子二次流的影响，以及由于旋转轮毂的额外影响。实验辅以项目合作伙伴的数值研究。

The blades and vanes in turbomachinery, moving relatively to each other, aerodynamically interact because of the viscous wakes and the potential effects of the blades. Near the endwalls the influence of the endwall boundary layers and secondary flow phenomena additionally superimpose. Due to the aerodynamic interaction of the blade rows the secondary flow patterns are periodically unsteady. The secondary losses are a significant part of the overall losses of the blade row and the whole engine.The project Unsteady secondary flow in axial turbines is part of the joint project Unsteady secondary flow effects in compressor und turbine blade rows. Main focuses of this joint project are fundamental experimental und numerical investigations in compressor and turbine cascades to detect and describe the significant secondary flow effects. The influence of systematic parameter variations on the unsteady behavior of secondary flow effects and loss generation will be investigated. With these investigations the potential for improving the performance of turbomachinery components using advantageous secondary flow effects will be identified.Aim of the project Unsteady secondary flow in axial turbines is to contribute to an improved physical understanding of unsteady secondary flow effects in the blade rows of axial turbines. Fundamental experimental investigations will show, to what extent the periodical unsteady wakes influence the secondary flows and the loss generation in turbine blade and vane rows. The experiments will be performed in a low-speed axial turbine, using two different builds. For turbine build 1 the periodical unsteady wakes are generated with rotating bars. The influence of the bar wakes ion the secondary flow field and the losses in a subsequent stator will be investigated in detail. For turbine build 2 instead of the rotating bars a turbine rotor blade row will be used. Focuses of these investigations are the influence of real rotor wakes on the secondary flows in the stator as well as additional influences due to the rotating hub. The experiments are supplemented with numerical investigations of the project partners.