The influence of non-axisymmetric geometry on the generation mechanism of rotating stall in a centrifugal compressor and the experimental validation

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K14894
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Waseda University
• Principal Investigator: Fujisawa Nobumichi 早稲田大学, 理工学術院, 専任講師 (10778153)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 流体機械 / 流体工学 / CFD / 遠心圧縮機 / 旋回失速

Outline of Final Research Achievements

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. 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.

Free Research Field

流体機械

Academic Significance and Societal Importance of the Research Achievements

社会全般で広く実用化されている遠心圧縮機を対象として、その羽根なしディフューザ部分に発生する旋回失速の初生・旋回機構を初めて解明した。従来、各種圧縮機では失速余裕と呼ばれる安全運転範囲を設定して非定常現象の発生を抑制しているが、これらの運転余裕を設ける必要性から本来要求される高い圧力比や広範な運転流量範囲を犠牲にしている。この基礎研究によって、非定常現象の発生機構が解明され、失速回避策が提案されることでより高い圧力比条件下での運転が可能となり、圧縮機性能を飛躍的に向上させると共に、将来的には温室効果ガスなどの発生を抑制する産業機械の設計手法が提案されることが期待される。