Improvement in stable operating range of a centrifugal compressor with leaned diffuser vanes

The stable operating range of the centrifugal compressor is limited by stall or surge at lower mass flow rates and by choke at higher mass flow rates. The type of diffuser used has a strong influence on the performance of a centrifugal compressor. This paper presents a numerical investigation of the effect of the leaned vanes in the low solidity vaned diffuser on the stable operating range of a centrifugal compressor. The vanes in the low solidity vaned diffuser were leaned in the direction of impeller rotation by reducing their inlet angle from hub to shroud uniformly. Four cases of leaned vaned diffusers were configured downstream of the same impeller with different lean magnitude. The compressor stage with 6° leaned vaned diffuser gave an improvement of 19.3 % and 12.2 % in the stall margin and the operating range, respectively, over the stage with low solidity vaned diffuser.