Influence of the clearance size on rotating instability in an axial compressor stator

Authors

C. Beselt, R. van Rennings, R. Sorge, D. Peitsch, F. Thiele, K. Ehrenfried, P.-U. Thamsen - TU Berlin
B. Pardowitz, L. Enghardt - German Aerospace Center(DLR), Berlin, Germany

Abstract

In order to improve the understanding of unsteady secondary flow structures in axial turbomachines, the flow in a scaled axial compressor stator was studied. It was operated in the vicinity of the stability line and could be equipped with variable hub clearances. Results from unsteady aerodynamic and acoustic pressure measurements, high-speed Particle Image Velocimetry measurements, and turbulence resolving numerical simulations are presented. Typical characteristics of the rotating instability (RI) phenomenon were found. A parameter study varying the clearance size and the blade loading, respectively, revealed the surprising occurrence of the RI even for the stator configuration without hub clearance. This contradicts the hitherto presumption of a hub or tip clearance needed to be in place for a rotating instability to emerge