On the Aerodynamic and Acoustic Behavior of Double Outlet Squirrel Cage Fans

Abstract

Investigations and observations on fluid flow and performance characteristics (numerically and experimentally) and sound generation (experimentally) of single and double outlet squirrel cage fans are performed in this study. The main objective is to survey the performance of double outlet fans and the effect of two volute tongues as main sound sources. Fan performance and sound experiments are conducted using an in-duct experimental setup. The efficiency and pressure curves show that each outlet channels of the double outlet fan operates similar to a single outlet one. As a criterion for evaluating the sound generation, total sound pressure level (SPL) and the noise component at blade passing frequency (BPF) in the power spectrum are considered. A comparison between the total sound pressure levels of the fans shows that in both of them the BPF noise increases with flow rate, while higher SPL is found for the double outlet one. An exactly-higher velocity jet/wake flow from the rotor in double outlet fan is responsible for the higher BPF noise.

Keywords

• fan; forward curved; double outlet; efficiency; sound pressure level; blade passing frequency; flow induced noise.