13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
State-of-the-art centrifugal compressor units utilised in pipeline and in energy storage applications face the challenge of flexible and highly efficient operation. Geometric contouring on the hub side near a vaned diffuser affects the flow in a way which increases operational flexibility by delaying the incipience of instability and thereby increases compressor operating range. In the present paper, a hub-side wall contouring is applied within the vaneless space of an open impeller vaned diffuser centrifugal compressor stage. The performance characteristic of the novel hub contouring is evaluated in a scale-model test rig and compared against a baseline design. A stable operating range increase of 8% is achieved for the contoured design at Mu2 = 1.16. 5-hole probe measurements covering a complete diffuser blade- to-blade passage are performed upstream the diffuser and compared both against CFD simulations and against the measurements of the baseline design for an operating point near the stability limit.