Investigation of an inversely designed centrifugal compressor stage - Part II: Experimental investigations

This paper presents an experimental investigation of two centrifugal compressor stage configurations. The baseline configuration has been designed using conventional design engineering tools. The second configuration was designed using advanced inverse design rules as described in Part 1. It is designed to match the choke, flow as well as the best point of the conventionally designed stage. The experimental investigation is conducted in the industry-scale centrifugal compressor facility at the Turbomachinery Laboratory of the Swiss Federal Institute of Technology. Performance maps for both configurations at several speed lines are presented. These plots show the overall behavior of the stages designed using the different design approaches and their operating range. Time-resolved measurements show details of the unsteady flow field within the diffuser close to the impeller exit. The time-resolved data have been analyzed to assist the explanation of changes in the characteristics and associated efficiency penalties and gains. The processed data show the benefits of the new inverse design method with respect to an improvement of the compressor efficiency and the operating range. It is seen that the application of an inverse design method results in a more uniform flow into the diffuser.