A Study on Aerodynamic Characteristics and Noise of a Ring Fan

The ring fan is a blower that has a shroud at the tip side of the axial flow impeller. In this study, to clarify the influence of the flow around the impeller on the aerodynamic characteristics and noise of the fan is aimed. The following characteristics were obtained; the efficiency of the ring fan is improved about 13% than the current propeller fan, the specific noise level is reduced approximately 6dB. The potential of the blade tip vortex of the ring fan has been weakened by the shroud. The blade tip vortex of the ring fan is generated at outside of the diameter of the impeller; the relative flow is attached to the blade surface by the weakened tip vortex. From these results, the overall characteristics of the fan improved by the decrease of the relative velocity