Study of Tonal Fan Noise Reduction by Modification of the Volute Cutoff
Blade-passing frequency (BPF) tonal noise is usually the main contributor to centrifugal fan noise as opposed to broad-band noise; therefore, abating its strength can reduce fan noise significantly. The predominant BPF noise source is the surface acoustic dipole over the cutoff due to the flow interactions between the impeller and the volute. In this study, a modified cutoff with an inclined edge and enlarged cutoff clearance was successfully employed to reduce the BPF noise; the measured noise spectra at three different flow rates of the inclined-cutoff fan and the original fan were compared, and noticeable noise reduction was found. The cause of this tonal noise reduction was numerically studied, using computational fluid dynamics (CFD) technology and acoustic analogy theory to calculate the flow fields inside the fan and sound radiation respectively. Results showed that the cutoff, including the geometric configuration and it's clearance with the impeller, was crucial to impeller-volute flow interactions. As a consequence, this inclined cutoff with enlarged cutoff clearance could eliminate the BPF pressure fluctuation, i.e. BPF dipole source, at the design point effectively; although the BPF pressure fluctuation was still notable at large flow rates, the radiated sound power decreased drastically attributed to the phase cancellation of the dipole sources. This study shows that CFD combined with acoustic analogy can provide a reliable access to noise prediction, thus it will be employed in aeroacoustic optimization of centrifugal fans.
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Document Type: Research Article
Publication date: November 1, 2010
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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