<p>Due to the continuous improvement of computer computing power, higher requirements are put forward for the heat dissipation in cabinets. The serious noise problem caused by the extensive application of cooling fans needs to be solved urgently. Cooling fans usually need to change working conditions according to the heat dissipation requirements in the space, which causes the variation of the main radiated noise frequency. An axial flow fan noise reduction technique with inlet duct is introduced, which can effectively reduce aerodynamic tonal noise under different working conditions. The noise reduction law of inlet duct on an axial flow cooling fan under variable working conditions is studied experimentally and numerically. In the test conditions, tonal noise is an important aerodynamic noise source, and its energy ratio increases with the fan rotation speed increasing and remains above 50%. Effective noise reduction at rated speed was achieved by installing short duct on the fan inlet. Considering the duct mode cut-off effect, the high order mode correction technique of double uniform sampling point is used to obtain the accurate circumferential acoustic modes at 1-3BPF at the fan inlet, and the noise reduction effect is explained from the mode propagation pathway. Moreover, the influence of the short duct on the fan aerodynamic characteristics is explored using CFD. The change of the fan aerodynamic performance shows that the flow rate is slightly influenced by inlet duct at high tip Mach numbers. The pressure pulsation on the blade surface decreases significantly with the duct, which reflects the correction effect of the inlet duct on the irregular intake flow and the improvement of the noise source characteristics. Measurement of variable working conditions indicates that when the tip Mach number increases from 0.049 to 0.156, the average total sound pressure level reduction in the far field of 1 m increases from 0.76 dB(A) to 4.26 dB(A), and the corresponding tonal noise energy ratio decreases. Furthermore, the noise reduction law of inlet duct is analyzed from the aspect of acoustic mode cut-off and aerodynamic characteristic variation, which provides guidance for the variable condition strategy of applying short duct noise reduction method to cooling fans.</p>

Noise Reduction Analysis of Electronic Device Cooling Fan With Duct and Its Application Under Variable Working Conditions

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.