Title of Paper:The effect of impeller-diffuser interactions on diffuser performance in a centrifugal compressor

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Date of Publication:2016-01-01

Journal:ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS

Included Journals:SCIE

Volume:10

Issue:1

Page Number:565-577

ISSN No.:1994-2060

Key Words:Unshrouded centrifugal impeller; diffuser performance; impeller-diffuser interaction; unsteady simulation; frequency spectrum analysis

Abstract:The unsteady phenomenon abounds in centrifugal compressors and significantly affects the compressor performance. In this paper, unsteady simulations are carried out to investigate the aerodynamic performance of a process-unshrouded centrifugal compressor and the unsteady mechanism in the vaned diffuser. The predicted stage performance and pressure fluctuations at some locations are in good agreement with experimental data. The predicted main pressure fluctuation frequency spectrums at the diffuser inlet and outlet are consistent with the measured results. The results indicate that at the inlet of the diffuser there are two pressure peaks in a passage cycle. The higher pressure peak relates to the impeller wake and the lower peak is connected with the vortex generated at the diffuser's leading edge. With a decrease in the mass flow coefficient, the vortex core region becomes larger and the lower pressure peak becomes more pronounced. The change in circumferential flow angle at the diffuser inlet is mainly responsible for the unsteadiness in the diffuser flow field, which in turn affects the inlet incidence of the diffuser vane and the vane loading distributions.