Abstract
Low specific speed impellers are applied to high pressure ratio centrifugal compressors because of the small volume flow rate. Generally, the efficiency of the low specific speed impellers is lower than that of high specific speed impellers, because the small width of the flow passage makes the friction loss increase. Wedge impellers that have enlarged flow passage width by using the thick blades are developed for the purpose of efficiency improvement of the low specific speed impellers. The parameters of the functions that decide the blade angle and thickness are investigated. The suitable blade profiles are clarified by performance estimations for the various impeller profiles. Moreover, the designed Wedge impellers are manufactured and tested experimentally to evaluate its performances. As a result, the efficiency of the Wedge impellers increased by 4% and the operation range was greatly expanded compared with the conventional impellers that have thin blades.
