Effects of diffuser leading-edge geometries on performance and noise characteristics of a centrifugal compressor

The noise reduction radiated from a centrifugal compressor with vaned diffuser using hooked and tapered diffuser vane are discussed by experiments and CFD. Most dominant noise of the centrifugal compressor is interaction tone noise between impeller-discharged flow and diffuser leading-edge. Thus, the shape of diffuser leading-edge is important to reduce the noise level of interaction tone noise. In the experiments, the compressor performance by using hooked diffuser vane is deteriorated because of increase of the leakage-flow passing through the hooked portion while the hooked diffusers are able to reduce the noise level effectively. On the other hand, tapered diffuser vanes are able to reduce the noise and to maintain high compressor performance simultaneously. In the CFD, the twin vortices are generated by the leakage-flow passing through the tapered portion and the vortices induce secondary flow near the pressure surface at diffuser leading-edge and suppress the flow separation from the diffuser leading-edge.