Secondary flow in ultra-low-aspect-ratio transonic turbine cascades.

该项目将对极小展弦比跨音速涡轮叶栅的二次损失效应有更深入的了解。因此，现有的损耗相关性将针对这个极端的几何范围进行改进和扩展。目前的公共损耗相关性不包括极低的纵横比范围。由于跨音速流动在实际应用中是非常常见的，计划中的研究也将暗示亚音速和跨音速的流动状态。在低端壁距离的构型中，一个典型的现象是二次流效应的合并。这种影响及其对主流的影响和由此产生的流动损失还没有得到充分的研究。为了建立损失相关扩展的数据库，计划使用一种混合方法，其中数据将通过验证的数值调查来提供。为了验证，将在跨音速叶栅试验台上研究特殊的几何形状。使用数字数据建立损失数据库，提高了调查的灵活性和范围。自己以前在这个课题上的工作表明，CFD能够预测这种几何形状的损失。此外，还将在非设计条件下对叶栅流动进行研究。这一点很重要，因为公共入射损失相关性在非常低的纵横比范围内也是无效的。这些流态也不为人所知。该项目不仅从科学角度来看很重要。在很小展弦比范围内验证的损失关联式将用于高压空气涡轮的设计。例如，这些涡轮机被用作飞机模型风洞测试的发动机模拟器。其他应用是在医药行业和所有其他行业中具有非常高转速的压缩空气马达，其中非常高功率密度的压缩空气马达比电动马达更受欢迎。

The proposed project will deliver a deeper understanding for the secondary loss effects in transonic turbine cascades with very low aspect ratio. As a result the existing loss correlation will be refined and extended for this extreme geometry range. Current public loss correlations do not cover the extreme low aspect ratio range. The planned investigations will imply the subsonic and transonic flow regime as well, since the transonic flow is very usual for the real applications.A typical phenomenon in configurations with a low endwall distance is the merging of the secondary flow effects. This effect, its influence on the main flow and the resulting flow losses are not yet investigated adequately.To create the database for the loss correlation extension, it is planned to use a hybrid approach, in which the data will be delivered by validated numerical investigations. For the validation special geometries will be investigated in a transonic cascade test rig. Using numerical data for the loss database enhances the flexibility and range of the investigation. Own previous work on this topic showed that the CFD is capable to predict the losses in this geometry. Moreover the cascade flow will be investigated in off-design conditions. This is important since the public incidence loss correlations are also not valid for the very low aspect ratio range. These flow regimes are also not understood. The project is not only important from a scientific point of view. The validated loss correlations in the very low aspect ratio range will be used in the design of high pressure air turbines. These turbines are for example used as engine simulators for wind tunnel tests of airplane models. Other applications are compressed air motors with very high rotation speed in the medicine industry and all other industries where compressed air motors with their very high power density are preferred over electrical motors.