Vortex trajectory prediction and mode analysis of compressor stall with strong non-uniformity

Given the heightened requirements of understanding the flow structure under critical condition and improving flow control technique for the turbocharger compressor, further insight into the unsteady behaviors of spike-stall inception associated with tip leakage flow was vital. In this work, an unsteady full annular simulation of a centrifugal compressor coupled with experimental validations was carried out by using the Reynolds averaged Navier–Stokes technique. A spike-type stall in the impeller was determined with multiple criterion principles. Then, a dynamic mode decomposition procedure was applied to the numerical data to capture and visualize the dominant flow structure in both absolute and relative coordinate. The temporal and spatial development of coherent perturbations was reconstructed. Finally, based on the results of mode decomposition, a modified prediction model of vortex trajectory concerning the asymmetrical flow, which can determine the circumferential location of spike-stall inception, was put forward. The results indicate that the low-frequency perturbation associated with stall inception can be captured by the DMD approach under both absolute and relative frames with the perturbation frequencies of 0.44 RF and 0.5 RF, respectively. Under absolute coordinate, the stall inception can be decomposed into three patterns: stationary stall cell in the mean flow, propagated stall cell in a certain region associated with BPF and oscillated stall cell in the origin place with the stall frequency of 0.44 RF. Considering the flow reconstruction, the flow instability in the impeller is relatively stationary stall inception without a significant phase shift and the stall perturbation occurs at 120^∘ circumferential location. The specific location of stall inception is influenced by the blade leading edge, which can be predicted by the prediction model of the vortex trajectory accurately.