Investigation study on the flow-induced noise by winglet and shroud shape of an axial flow fan at an outdoor unit of air conditioner

Abstract

Axial flow fans of outdoor units are equipped with specially shaped winglets and shroud for reduction of the flow-induced noise. In this study, the unsteady state flow field and the characteristics of the flow-induced noise according to the application of the sweptback tip winglets and 30 % covered shroud in an axial flow fan of an outdoor unit of air conditioner were experimentally and numerically analyzed. To analyze the unsteady flow field, large eddy simulation (LES) reflecting the geometry of complicated outdoor unit was performed; and the LES results were used by simplified Ffowcs Williams and Hawkings (FW-H) equation in order to calculate the noise numerically. As a result, asymmetric flow characteristics inside the outdoor unit by the mount and the shape of blade tip and shroud were found to cause inconsistent movement of the tip leakage vortex, which was revealed to change the characteristics of the flow-induced noise.