Study on Generation Mechanism of Discrete Frequency Noise from a Small Axial Flow Fan Based on Wake Analysis

Abstract

In this study, the generation mechanism of the discrete frequency noise from a small axial flow fan having an outlet guide vane was analyzed based on the wake characteristics of the rotor blades. Based on the organize of the actual measured fan noise, we indicated that the noise in the vicinity of the design point of the fan with the outlet guide vanes was affected by the discrete frequency noise synchronized with the blade passing frequency. The drag force formed in the wake near the blade tip represented the characteristics of the discrete frequency noise. We clarified that the discrete frequency noise of the small axial fan was generated by the drag force formed at the blade tip flowing into the outlet guide vanes.