Optimization of Return Channels of High Flow Rate Centrifugal Compressor Stages Using CFD Methods

Calculations performed with modern CFD programs aid in optimizing flow paths of centrifugal compressors. Characteristics of stator elements of flow paths, calculated via CFD methods, are considered quite accurate. We present optimized return channels (RCh) of three model industrial compressor stages with vaneless diffusers. A parameterized model was created for optimization. The MOGA (Multi-Objective Genetic Algorithm) optimization method was applied in the Direct Optimization program of the ANSYS (Analysis System) software package. Optimization objects were return channels of the stages with high flow rate 0.15. The stages have three different loading factors 0.45, 0.60, 0.70. The optimization goal was to achieve the minimum loss coefficient at the design point. During the optimization process, we varied the following: the number of vanes, the inlet angle of the vanes, the height of the vanes at the inlet, the outer and inner radii of curvature of the U-bend. The outlet angle of the vanes was selected to minimize outlet circumferential velocity. In comparison with preliminary design, the optimized RCh are more efficient across the entire range of flow rates. The optimization reduced the loss coefficient by 20% at the design flow rate.