Comparative Study of Subsynchronous Rotating Flow Patterns in Centrifugal Compressors with Vaneless Diffusers,
GHENT RIJKSUNIVERSITEIT (BELGIUM)
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A comparative experimental investigation of the unstable operating modes of a centrifugal compressor is made. Hot wire measurements, in two different compressor configurations, allowed to distinguish between the different unsteady flow pattern. Impeller andor diffuser rotating stall has been observed, depending on the flow conditions. The measured relative rotational speed of this perturbation is cross-checked with other experimental data and it is shown that the rotational speed is strongly dependent on the type of rotating stall. The diffuser absolute inlet flow angle at the onset of diffuser rotating stall agrees well with the value predicted by an existing stability criterion.