Abstract: The 3D internal viscous flow in the last stage of a centrifugal compressor is analyzed numerically with commercial computational fluid dynamic software NUMECA. The geometric model includes the close-type impeller, the vaneless diffuser and the volute. Based on the analytic results, modifications to the constant width volute are proposed and the stage efficiency is increased by 4.5%. The same approach is applied on the last stage of another centrifugal compressor and the efficiency is also increased by 4.5%. Through summing up the effect of different parameters, the code for the aerodynamic design of the welding type volute is developed. The code is tested on another compressor with a constant height volute and the last stage efficiency is increased by 3%. Numerical experiments prove that the code can be used for the aerodynamic design of all welding type volutes.

Key words: Centrifugal compressor, Efficiency, Numerical simulation, Welding type volute