This paper is a follow-up to work published by Sorokes et al. [16] regarding a diffuser flow-field phenomenon, identified as a precursor to stall in a centrifugal stage. The earlier work provided greater detail on the phenomenon that occurred, including further details on the CFD analyses done to investigate the phenomenon and the trends observed in the test data. The numerical and experimental results described in the earlier work were used as a foundation in developing improved stationary components of another stage of similar design whose surge margin fell short of expectation, with the goal of improving its surge margin and overall performance. The study focused specifically on improving the flow characteristics in the diffuser and return channel by optimizing the geometry. The improvement in surge margin and overall performance was first verified numerically (through CFD analysis) and then experimentally via scale model testing.

The paper will provide an overview of the centrifugal stage that was tested along with a description of the test vehicle, operating conditions and instrumentation used. The paper will also include a description of the numerical work completed; i.e., the CFD code used, computational domain considered and boundary conditions applied. Comparisons of the trends observed in the experimental and numerical work will be offered and the agreement between the numerical and empirical results will be assessed. Finally, performance comparisons of the optimized stage with the previous stage will also be presented.

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