ROTOR-STATOR INTERACTION SCENARIOS FOR THE CENTRIFUGAL COMPRESSOR OF A HELICOPTER ENGINE

摘要

The present paper deals with interaction phenomena that may arise in the centrifugal compressor of helicopter engines when structural contacts occur between the blade-tips and the surrounding casing. Those phenomena may lead to increased levels of vibration and are currently under investigation for axial compressors of aircraft engines for which blade failures were observed. The growing understanding of these phenomena allows for more challenging numerical simulations with increased geometrical complexity such as centrifugal compressors. The simulation of blade-tip/casing contacts is carried out based on an existing strategy previously introduced by the authors. An ovalized casing is considered and two contact configurations are investigated: (1) a single blade impacts the casing and (2) contact may occur on any blade of the cyclic assembly. Based on these two contact scenarios, an in-depth analysis is performed through both time and space Fourier transforms. Results highlight the plausibility of blade/casing interaction phenomena similar to those observed in axial compressors since interactions are detected with localized vibration levels on a single impacting blade. When contact is treated on all the blades of the centrifugal compressor, the witnessed interactions feature a higher degree of complexity and usual criteria become insufficient to predict interaction speeds as well as the location of significant peaks of vibration in the frequency domain.