Evolution Process of Diffuser Stall in a Centrifugal Compressor With Vaned Diffuser

Abstract

The evolution process of a diffuser rotating stall in a centrifugal compressor with a vaned diffuser was investigated by experimental and numerical analyses. From velocity measurements, it was found that the diffuser stall propagated near the shroud side in the vaneless space. As the mass flow decreased, a stage stall rotated within both the impeller and diffuser passages, instead of a diffuser stall. The evolution process of the diffuser stall had three stall forms. First, the diffuser stall, which was rotating on the shroud side, shifted to the hub side. Then, the diffuser stall moved into the impeller passages and evolved to a stage stall. From computational fluid dynamics (CFD) analysis, a tornado-type vortex was generated first, near the hub side of the diffuser leading edge, when the diffuser stall was shifted to the hub side. Next, a throat area blockage was formed near the hub side because of the boundary layer separation in the vaneless space. Finally, the blockage within the diffuser passages expanded to the impeller passages and developed into a stage stall. From the pressure measurements along the impeller and diffuser passages, the magnitude of pressure fluctuation on the casing wall of the diffuser throat area also suddenly increased when the diffuser stall shifted to the hub side. Therefore, the evolution area of the diffuser stall was caused by the evolution of the blockage near the throat area of the diffuser passage.

Evolution of unsteady vortex structures and rotating stall cells in a centrifugal compressor with vaneless diffuser

“…It may be directly caused by the upstream deteriorative inlet flow field near the shroud. This observation does not conform to the flow mechanisms by Fujisawa et al (2018).…”

“…In order to investigate the flow mechanisms, Fujisawa et al (2018) conducted a numerical simulation using the DEStype method. A tornado-type vortex was observed at the impeller inlet related to a stage stall cell.…”

Intelligent Identification of Rotating Stall for Centrifugal Compressor based on Pressure Pulsation Signals and SDKAE Network

“…At present, most of the research on rotating stalls of a centrifugal compressor is in time-frequency domain numerical analysis such as the coherence analysis method. With the development of intelligent manufacturing, the analysis ability of these models is obviously insufficient in the face of massive engineering data in actual processing [13].…”

Operating Range Extension of an Open Impeller Centrifugal Compressor Stage Utilising 3D Diffuser End Wall Contouring

“…A wide stable operating range of vaned diffusers is therefore important to meet these requirements. Fujisawa et al [4] and Fujisawa et al [5] studied the diffuser stall mechanism in an open impeller centrifugal compressor stage with a wedge diffuser. As initiation for diffuser instability a rotating diffuser stall was observed on shroud side.…”