Effect of the tip clearance variation on the performance of a centrifugal compressor with considering impeller deformation

Abstract

The effects of impeller tip clearance variation on centrifugal compressor performance have been investigated experimentally and numerically in a centrifugal compressor. In order to accurately calculate the real tip clearance, the influence of impeller geometry deformation caused by the thermal load (temperature variation) and mechanical loads (aerodynamic pressure and centrifugal force) under working condition on the compressor aerodynamic performance is taken into account by fluid/solid interaction method during the computational fluid dynamics flow field analysis process. In this article, tip clearance flow under the real working environment is investigated with three different tip clearance cases. The impeller deformation combined with the adjustment of tip clearance causes some influence on the aerodynamic performance and on the structure reliability of the compressor system. For the aerodynamic design, an increase in the impeller tip clearance decreases the overall pressure rise and isentropic efficiency of the compressor, mainly due to the tip clearance loss in the impeller. Regarding structure design, the uniform relative tip clearance from the inlet to the outlet CR = 7.3 per cent is changed to non-uniform distribution from 6.4 per cent to 4.15 per cent. The largest deformation location occurs at the blade inducer and trailing-edge tip. The relative clearance near the outlet of the blade is reduced about 3.15 per cent which will cause great influence on the impeller working reliability.