• stall
• rotating stall
• aerodynamics
• CFD
• diffuser
• centrifugal compressor

The work aims to investigate the effects of the return channel removal on the stability and possible appearance of rotating stall in centrifugal compressors. Particular attention is to be paid to the performances of the diffuser, as it is considered by various experts to be one of the main elements to characterize the phenomenon of the instability of the whole machine.
Thanks to the Computational Fluid Dynamics, and with the ambitious goal of bringing useful results to simplify and reduce the costs of experimental tests in the industrial field, this work examines how the flow stability in the diffuser is influenced by the presence or absence of the return channel and by its geometry. The goal is to understand if the geometry outlet of the stage can delay, anticipate or leave unchanged the flow angle at which instability occurs, and how it affects the flow that develops later.