The characteristics of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser are discussed by experiments, including visualization techniques using the oil-film method. Research attention is paid to the leading edge geometries of the diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by several decibels by setting some clearances in both the hub and shroud surfaces of the diffuser wall along with some decline in the pressure-rise coefficient. Since the decline turned out to be caused by the flow impingement and also by the secondary flow within the diffuser passages, several new types of diffuser vane geometries which do not detract from both the performance and noise level are developed and utilized for the experiments. The presented diffuser vane geometries will offer a few basic guidelines for the diffuser vane design.
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.
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