A series of experiments are performed to investigate and quantify the design and off-design three-dimensional mean flow in a centrifugal compressor impeller. The experiments entail the acquisition and analysis of LDV data in the impeller passages of a low speed research mixed-flow compressor operating at its design point and at a point near the inception of rotating stall. The LDV data at both operating points show regions near the impeller exit with a significant velocity deficit on the shroud surface characteristic of the traditional jet-wake structure observed in many centrifugal compressors. At design, the maximum velocity deficit occurs at a location 70% of the passage width from the pressure to the suction surface. At the incipient stall point, the maximum velocity deficit occurs in the shroud suction surface corner, with the data indicating reverse flow.

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