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

• Applicant: Professor Dr.-Ing. Konrad Vogeler
• Subject Area: Hydraulic and Turbo Engines and Piston Engines
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258090413

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.

• DFG Programme: Research Grants