Effects of Blade Tip Clearance Size on Performance of a Centrifugal Compressor

Considering tip clearance in compressor blades results in the flow instabilities and leads to weakend aerothermo-dynamical and fluid-dynamical performances. In the present paper, effects of blade tip clearance size on a centrifugal compressor performance especially at near stall condition have been investigated. The current study is carried out on Iran University of Science and Technology centrifugal compressor test rig. The method of investigation is on the basis of computational fluid dynamics technique. In this paper, the Fluent solver package has been used for simulations. The Reynolds-Averaged Navier-Stokes (RANS) equations in three-dimensional and viscous form have been solved by a segregated implicit second-order scheme. The grid consists of 2,550,000 cells with structured hexahedral meshes. To validate the numerical simulation results, overall performance curves and static pressure distribution on the impeller casing were compared with each other in numerical and experimental conditions. The results showed good agreement of numerical results and experimental data. After validating numerical solutions, 5 blade tip clearance size conditions have been investigated numerically. Final results showed that increasing tip clearance size from 1.3 up to 3.7 percent of blade chord lowers the loading factor and efficiency 3.7% and 4.7% respectively.