Experiment study on effect of tip clearance on centrifugal impeller performance

Fluid loss caused by leaks through the impeller tip clearance was investigated for a centrifugal compressor. Operating conditions and clearance were varied independently during the experiment. It was found that the average compressor performance would be reduced by about 10% when the relative clearance was increased from 2.8% to 6.9%. The leak velocity in clearance was measured by hot wire. Moreover, the distribution of velocity at impeller exit was taken and the results show that the reverse flow occurs near hub side in small flow rate.