Non-axisymmetric Profiled End Wall and Suction Surface Optimization Design of Vaned Diffuser in a Centrifugal Compressor

Abstract

The non-axisymmetric end wall profiling technology has been widely applied in turbines and axial flow compressors, effectively suppressing corner separation losses and improving compressor efficiency. However, its application in centrifugal compressors remains relatively limited. To realize effective flow control and aerodynamic performance enhancement, existing parameterization methods typically require 20 to 30 or even more profiling parameters. They also incorporate optimization based on surrogate models, which significantly increases the workload and computational costs. To reduce the number of design parameters, this study proposes a non-axisymmetric end wall and suction surface profiling method that uses only 8 profiling parameters and applies it to centrifugal compressors with guide vane diffusers. By superimposing different surface elements with boundary layer flow control capabilities, effective control of the surface shape can be achieved. Subsequently, a simplified model including the inlet duct, impeller, and diffuser is used for the optimization design process. Isentropic efficiency and static pressure efficiency are selected as optimization objectives. The optimization results indicate that under design point conditions, the overall stage isentropic efficiency increases by 0.4%, while the total pressure ratio rises by 0.06. Flow field analysis further indicates that the optimized profiling produces a more uniform velocity distribution within the diffuser and at the diffuser outlet, thereby improving the inlet conditions of the scroll and enhancing the overall stage performance.