Resumen de Noise source analysis and control of two axial-flow cooling fans in series

Chen Wang, Weihao Zhang, Lixi Huang

• The noise signature of two identical small axial-flow cooling fans in series was analyzed and a technique of synchronous averaging with time-base stretching was used to perform the noise source component decomposition. Acoustic directivity measurements were conducted for two configurations. First of all, the inlet flow to the upstream fan is unobstructed, i.e. in a free-field. The effect of a flow straightener placed between the two fans was studied as well. The proportion of each noise source in the total noise is changed by the flow straightener even though the total SPL is hardly affected. Secondly, the inlet flow is distorted by a flat plate covering one half of the inlet flow passage. The effect of the axial distance between the flat plate and fan inlet was investigated. The same flow straightener was mounted at the inlet of the upstream fan to reduce the negative effect of the inlet flow distortion. The average total SPL was reduced by 2.5 dB