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Identification of Rotating Pressure Waves in a Centrifugal Compressor diffuser by Means of the Wavelet Cross-Correlation

Rotating stall is usually the first symptom of approaching compressor instability. It consists of zones of a turbulent flow, which rotate slower than the compressor impeller. The wavelet cross-correlation function was applied to detect rotating objects, whereas the continuous wavelet transform was used to identify different phases of the compressor operation. These methods of signal analysis enabled the identification of rotating pressure waves that appear during all phases of operation. Some of them have several times shorter wavelength than these manifested by the rotating stall. What is more, rotating pressure waves, though very weak, appear also during the stable compressor operation.