Periodical unsteady flow near the endwalls of rotating compressor bladings

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Current efforts in turbomachinery to increase pressure ratio, reduce blade count, decrease the aspect ratio, intense part load operation, etc. lead to increasing influence of flows near the side walls on the overall engine performance. Especially the operating range, losses and heat transfer are influenced by these flows. The occurring mechanisms are not fully understood although being investigated since decades. Thus the current technological progress strongly requests adequate basic research activity. This deficit will be addressed by a joint research program of four research groups at TU Dresden, UniBw München und RU Bochum, by carefully coordinated simulations and experiments to produce relevant results. Beside the investigation of heat transfer and the development of methodical tools a major goal of this joint program is the detailed analysis of the effect of system rotation. Therefor a number of specially planed and adjusted configurations will be investigated and compared with each other.In the framework of the project part at the Chair for Turbomachinery and Flight Propulsion at TU Dresden the flow near the endwall of a compressor rotor will be analyzed in comparison with stationary cascades. Through appropriate test assemblies at the Low Speed Research Compressor distinct stepwise abstractions between a linear stationary cascade and the rotating compressor rotor will be introduced to evaluate the effects of rotation, Coriolis force, increasing pitch with blade height, radial pressure gradients, relative motion of the end walls and shear of the inlet boundary layer separately. The experimental investigation will cover measurements at a stationary annular cascade (stator) with and without radial clearance to the rotating / non-rotating hub endwall and a rotating annular cascade (rotor) with and without wake generator for simulation of the rotor-stator-interaction. All builds and additional parameter variation will be numerically modelled by RANS and URANS simulations. The target of this work package is an improvement of the physical understanding of the influence of the single parameters, a validation of their prediction by RANS methods and a determination of the strength and weaknesses of different numerical approaches especially in comparison with the LES of selected test cases by the project part at the Chair of Fluid Mechanics at TU Dresden. Furthermore the phenomena in compressor and turbine configurations will be compared and discussed together with the research partners in Munich and Bochum.