The unsteady behavior of diffuser stall in a centrifugal compressor with vaneless diffuser

Hiroshi Miida, Kenta Tajima, Nobumichi Fujisawa, Yutaka Ohta

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The unsteady diffuser stall behavior in a centrifugal compressor with a vaneless diffuser was investigated by experimental and computational analyses. The diffuser stall generated as the mass flow rate decreased. The diffuser stall cell rotated at 25-30 % of the impeller rotational speed, with diffuser stall fluctuations observed at 180° from the cutoff. The diffuser stall fluctuation magnitude gradually increased near the cutoff. Based on diffuser inlet velocity measurements, the diffuser stall fluctuations generated near both the shroud and hub sides, and the diffuser stall appeared at 180° and 240° from the cutoff. According to the CFD analysis, the mass flow fluctuations at the diffuser exit showed a low mass flow region, rotating at approximately 25% of the impeller rotational speed. They began at 180° from the cutoff and developed as this region approached the cutoff. Therefore, the diffuser stall could be simulated by CFD analysis. First, the diffuser stall cell originated at 180° from the cutoff by interaction with boundary separation and impeller discharge vortex. Then, the diffuser stall cell further developed by boundary separation accumulation and the induced low velocity area, located at the stall cell center. The low velocity region formed a blockage across the diffuser passage span. The diffuser stall cell expanded in the impeller rotational direction due to boundary separation caused by a positive flow angle. Finally, the diffuser stall cell vanished when it passed the cutoff, because mass flow recovery occurred.

Original languageEnglish
Title of host publicationFluid Applications and Systems; Fluid Measurement and Instrumentation
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791883716
DOIs
Publication statusPublished - 2020
EventASME 2020 Fluids Engineering Division Summer Meeting, FEDSM 2020, collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels - Virtual, Online
Duration: 2020 Jul 132020 Jul 15

Publication series

NameAmerican Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM
Volume1
ISSN (Print)0888-8116

Conference

ConferenceASME 2020 Fluids Engineering Division Summer Meeting, FEDSM 2020, collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels
CityVirtual, Online
Period20/7/1320/7/15

Keywords

  • Centrifugal Compressor
  • CFD
  • DES
  • Diffuser Stall
  • Internal Flow
  • Vaneless Diffuser

ASJC Scopus subject areas

  • Mechanical Engineering

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