Influence of Fillet Radii on the Flow and Strength Behavior of a Shrouded Centrifugal Compressor Impeller

The trade-off between the aerodynamic and structural behavior for different fillet radii in a shrouded centrifugal compressor impeller is often not known in the early design phase. Therefore, many iteration loops are needed in the later design phase and the developement time increases. Subject of the present work is to investigate the influence of the fillet radii on the flow and strength behavior of these impeller types. To determine the influence on the fluid mechanics in the turbomachine, full-stage CFD analyses are carried out for an impeller setup with five different fillet radii. Linear-elastic and elastic-plastic analyses as well as modal analyses are used to determine the relationship between fillet radii and structural mechanics. A quadrupling of the fillet radii leads to a reduction of the overall polytropic stage efficiency by 2.1 percentage points, while the von-Mises stress is reduced by around 38.3 to 40.2 percentage points. Based on the findings of this work, the relationship between fillet radius and flow and strength behavior can be better estimated in order to find a compromise between aerodynamic losses and increased component strength.