Fan Tonal Noise Reduction using Calibrated Obstructions in the Flow - An Experimental Approach

A1 - Tonal Noise Control with Flow Obstructions

We present the experimental results of a technology aiming at the cancellation of the tonal noise of fans, using calibrated obstructions placed upstream or downstream in the flow close to the fan. When placed at the optimal distance and angle, the obstruction generates pressure pulsations that interact with the fan pressure fluctuations in a destructive way, allowing to cancel the noise at the blade passing frequency, and, in some cases, at its first harmonic.

A parametric study has been conducted on two types of fans, axial and centrifugal. Parameters that have been studied are the obstructions shape and position and the fan speed. More than 50 different configurations have been investigated. A robot has been used to position the obstacles, allowing to get sound maps in distance and angle coordinates for each configuration.