Fillet, as a junction of the blade and endwall, can greatly affect the flow pattern and loss mechanism near the turbomachinery endwall. In order to investigate the effect of the fillet shape on the aerodynamic performance of the centrifugal impeller, a parametric method based on the ellipse equation is presented to model the fillet profile and the non-uniform distribution of fillet is controlled by the variable sin-type fillet hills. Then, the shapes and locations of the non-uniform distributed fillet are optimized to improve the overall efficiencies in multi-operating conditions. To preserve the surge margin, the mass flow rate near the choke condition is constrained though the geometric throat area of the impeller. The optimization results show that the efficiencies at all operating conditions are improved obviously and the vortices downstream of trailing edge are removed by applying the optimum non-uniform fillet hill at the pressure side.
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