Numerical Simulation of the Rotating Instability in an Annular Compressor Cascade Test Rigs

Abstract: The main topic of this study is the Rotating Instability (RI), which is investigated numerically. The RI is a self-induced rotating flow instability, which occurs at high blade loadings at globally stable flow condition prior to stall with a characteristic pressure signature in the frequency spectra. Former experimental work by Hermle and Weidenfeller at an annular compressor stator cascade at the Section of Turbomachinery, University of Kassel, has shown, that the rotating instability arises for incidences greater i = 12.3°. There are hints, that the origin is located at the hub near the leading edge, and can be identified in the frequency spectra of unsteady pressure signals. In order to investigate the capabilities of Reynolds averaged Navier-Stokes (RANS) and Detached-Eddy-Simulation (DES) to predict the characteristics of RI, extensive computation have been performed. The numerical simulations cover the complete annulus of the cascade and results are compared with experimental data. Beside the work of van Rennings, the presented computational results reveal that the development of a rotating flow pattern, similar to the rotating instability, can be captured with a DES method. Unsteady pressure signals near the hub at the leading edge are evaluated in the time and frequency domain and are compared to experimental data. Although the main characteristics of the rotating instability are captured by the simulation, there are some differences concerning the quantitative parameters, which can be related to the applied total pressure profile at the inlet.