Performance of a high-pressure-ratio centrifugal compressor influenced by distribution of tip clearance of the mixed-flow impeller.

To investigate influences of the distribution of tip clearance on the performance of centrifugal compressors, the mixed-flow impeller of a centrifugal compressor with l0:1 pressure ratio was tested with various distributions of the tip clearance varied by not only the axial movement but also the radial reforming of the shroud casing relative to the impeller. Measured data on the decrements of the input head and of the impeller efficiency due to the distribution of tip clearance are compared with the predicted values. The change in the available flow range due to the distribution of tip clearance is also discussed.