Since the early work on axial compressors the penalties due to radial clearances between blades and side walls are known and an ongoing focus of research work. The periodic unsteadiness of the tip clearance vortex, due to its interaction with the stator wakes, has only rarely been addressed in research papers so far. The current work presents experimental and numerical results from a four stage low speed research compressor modeling a state of the art compressor design. Time-resolved experimental measurements have been carried out at three different rotor tip clearances (gap to tip chord: 1.5%, 2.2%, 3.7%) to cover the third rotor’s casing static pressure and exit flow field. These results are compared with either steady simulations using different turbulence models or harmonic RANS calculations to discuss the periodical unsteady tip clearance vortex development at different clearance heights. The prediction of the local tip leakage flow is clearly improved by the EARSM turbulence model compared to the standard SST model. The harmonic RANS calculations (using the SST model) improve the prediction of time-averaged pressure rise and are used to analyze the rotor stator interaction in detail. The interaction of the rotor tip flow field with the passing stator wakes cause a segmentation of the tip clearance vortex and result in a sinusoidal variation in blockage downstream the rotor row.
Periodic Unsteady Tip Clearance Vortex Development in a Low Speed Axial Research Compressor at Different Tip Clearances
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Lange, M, Rolfes, M, Mailach, R, & Schrapp, H. "Periodic Unsteady Tip Clearance Vortex Development in a Low Speed Axial Research Compressor at Different Tip Clearances." Proceedings of the ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. Volume 2D: Turbomachinery. Charlotte, North Carolina, USA. June 26–30, 2017. V02DT46A023. ASME. https://doi.org/10.1115/GT2017-64256
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