Flow measurements were made at the mid-passage in the unshrouded and shrouded centrifugal impellers by means of a hot-wire anemometer rotating with each impeller. Effects of the blade tip leakage or the secondary flow on the relative flow, the Reynolds stress and the flow loss were discussed. In the shrouded impeller, the secondary flow appears about the suction-side/shroud corner. In the unshrouded impeller, the tip leakage interferes in this secondary flow around the middle blade-to-blade near the casing. Therefore, the values of Reynolds stresses tend to be high at the regions influenced with the secondary flow in the shrouded impeller and interfered with the tip leakage and the secondary flow in the unshrouded impeller. These regions remarkably coincide with those of the flow loss in both impellers, respectively.
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