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

该项目将对低展弦比跨声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在这个极端几何范围内得到细化和扩展。目前的公开损耗相关性不包括极低的宽高比范围。计划的研究也将包括亚音速和跨音速的流动形式，因为跨音速的流动在实际应用中是非常常见的。低端壁距离配置中的典型现象是二次流效应的合并。这种效应、它对主流的影响以及由此产生的流动损失尚未得到充分的研究。为了创建损失相关扩展的数据库，计划使用混合方法，其中数据将通过经过验证的数值调查提供。为了验证，将在跨音速叶栅试验台研究特殊几何形状。利用数值数据建立损失数据库，提高了调查的灵活性和范围。我之前在这个主题上的工作表明，CFD能够预测这种几何形状的损失。此外，还将研究非设计条件下的叶栅流动。这一点很重要，因为在非常低的纵横比范围内，公共入射损耗相关性也无效。这些流动状态也不为人所知。这个项目不仅从科学的角度来看很重要。在极低展弦比范围内验证的损失相关性将用于高压空气涡轮的设计。例如，这些涡轮机用作飞机模型风洞试验的发动机模拟器。其他应用是在医药工业和所有其他工业中具有非常高转速的压缩空气电动机，其中具有非常高功率密度的压缩空气电动机优于电动机。

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.