Investigation of dual-ported shroud casing in a centrifugal compressor: Aerodynamic performance and aeroacoustics

The dual-ported shroud casing has two ports over the impeller section in a centrifugal compressor, different from the traditional ported shroud casing. This paper uses numerical simulations and experiments to investigate the effects of the dual-ported shroud on the centrifugal compressor, including aerodynamic performance and aeroacoustics. According to the experimentally measured compressor performance map, the novel finding is that the dual-port casing treatment extends the compressor operating range by improving the instability margin and increasing the compressor choke flow capacity. The mechanism contributing to the choke flow capacity increase is the bypass function. The dual-ported shroud casing bypasses a part of the air to enter the impeller channels at the blade tips without going through the impeller geometry throat. Besides the benefits, the efficiency and aero-acoustic measurements identify the disadvantages of the dual-ports casing treatment: the peak efficiency deterioration at high rotational speeds and louder noise emission at the compressor inlet.