Abstract
Abstract This paper presents the results of a numerical investigation on the influence of wall roughness on the performance of centrifugal compressor volutes. The main objective of the presented work was to gain further knowledge on the highly three-dimensional flow inside the volute with regard to wall roughness and operating point (surge, best efficiency point and choke). The numerical investigation was carried out with steady state simulations and SST with enabled Reattachment Modification as turbulence model for two centrifugal compressor stages with different outward wound volutes. By means of the equivalent sand-grain roughness ks, the wall roughness was systematically varied and its influence on the volute was evaluated by a thorough performance and flow analysis. The expected drop in efficiency and polytropic head with increasing wall roughness was observed, which was more distinct at choke conditions, mainly due to the increasing skin friction losses at the volute walls. The flow analysis also showed influences of the wall roughness on the secondary vortex flows structures at the smaller volute cross sections near the volute tongue area, with distinct changes compared to the smooth wall case in terms of location and form. An influence of wall roughness on a possible shift of the best efficiency point was not observed.
Published Version
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