Numerical investigation of centrifugal compressor stall with compressed dynamic mode decomposition

Heightened interest in visualizing the flow structure under critical conditions for aero-engine led to further understanding of the underlying physical mechanism as well as to a better knowledge of the issues faced with their design and flow control. In this work, an unsteady full annular simulation of a centrifugal compressor coupled with experimental validations was presented. The diffuser stall was determined with various criterion principles and the wave-maker region under asymmetric flow field was investigated. Then, a dynamic mode decomposition (DMD) procedure concerning the whole domain and individual planes was applied to the numerical data so as to capture and visualize the dominating flow structure. With the purpose of improving calculation efficiency, a compressed DMD was adopted and validated against the standard DMD analysis results. Finally, the nonlinear development and spatial propagation between components of the coherent perturbations in diffuser and volute were reconstructed. The results indicate that the representative organized structure of flow instability can be captured with standard DMD approach. And by applying the compressed DMD approach, the flow mode can also be obtained with calculating time saving of 88.4% when the compression ratio is 1%. Considering the flow construction, four stall cells oscillating with little circumferential phase change are recovered during 6 rotor-cycles, indicating that the origin of the diffuser stall lies at the hub wall with fixed circumferential position near the diffuser outlet. The spatial propagation of stall mode except for the one near the volute tongue extends to the volute flow with a dumping effect of high-frequency perturbations.