Low solidity vaned diffusers for rotating stall prevention: experimental analysis of some design parameters

Rotating stall in centrifugal compressors is an attractive topic both for academic research and industrial applications. Its complex phenomenology requires detailed and advanced analyses to improve the understanding of the physical mechanisms responsible for its development. From such an investigation, benefits can also come for the design of more efficiently performing industrial compressors. In this context, an activity was planned focusing on the comprehension and characterization of rotating stall for a group of industrial centrifugal stages with a low blade-outlet-width-toimpeller-radius ratio for very high pressure applications. These are generally equipped with vaneless diffusers. In order to improve stage stability, the use of low solidity vaned diffusers (LSD) seems to be a very useful approach. Starting from results obtained for a previous set of LSD, new sets of configurations were tested in order to analyze in detail the influence of vane solidity, inlet radius and incidence at design point on performance and design point. Results are compared with those of the vaneless solution highlighting improvements and drawbacks.