This paper presents a novel approach for the passive adaptive control of tonal noise radiated from subsonic axial fans. Tonal noise originates from non-uniform flow that causes circumferentially varying blade lift and gives rise to radiated dipolar sound at the blade passage frequency (BPF) and its harmonics. The approach used in this paper is to introduce a flow control obstruction to generate a secondary circumferential unsteady lift mode, of equal amplitude but opposite in phase with the most radiating primary circumferential unsteady lift mode so that the resultant of both the most radiating primary mode and the secondary mode is null. Acoustic pressure attenuation up to 21 dB and 15 dB was obtained respectively at the BPF and at its first harmonic, using two control obstructions. Finally, the aerodynamic performance of the automotive fan used in this study is almost unaffected by the presence of the control obstruction.
Passive adaptive control of tonal noise from subsonic axial fans using flow control obstructions
2007
12 Seiten, 9 Bilder, 1 Tabelle, 15 Quellen
Conference paper
Storage medium
English
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