Aerodynamic performance and noise characteristics of a centrifugal compressor with modified vaned diffusers

Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored oil-film method. The focus of the research is concentrated on the leading edge shape of diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by more than ten decibels by using modified diffuser vanes which have 3-D tapered shapes on both pressure and suction surfaces of the leading edge. Furthermore, by adopting the proposed modified diffuser vanes, the secondary flow which is considered to be an obstruction of diffuser pressure recovery can be suppressed, and also the pressure decrease observed in the throat part of the diffuser flow passage is reducible. Thus, the proposed diffuser vanes show a favorable result for both noise and the aerodynamic performance of the centrifugal compressor, and offer a few basic guidelines for the diffuser vane design.