A Study on Configurations of Casing Treatment for Axial Flow Compressors

Abstract

Casing treatment is known to improve the stall margin of axial compressors. However, it is known as well that casing treatment 16wers the efficiency of compressors. An experiment was planned in order to test a series of configurations of casing treatment which are supposed to have favourable effects and obtain the optimum ones, if any, judged from above-mentioned two stand-points : larger stall margin improvement and smaller lowering of efficiency. The result showed that the relation between the stall margin improvement and the compressor efficiency for all of the tested configurations falls on some smooth curved-line, and thus, there exists no particulary superior treatment configurations to others. It rather showed a certain amount of loss in efficiency was inevitable in order to obtain some required amount of stall margin improvement. Influence of rotor tip clearance on the effect of casing treatment was also examined. The result can be used as a guide for the selection of configurations in designing casing treatment.