Volutes for radial-flow turbomachines (e.g., centrifugal fans and pumps) are spiral funnel-shaped casings that house rotors. Their function is to guide the flow from rotors to outlets and maintain constant flow speeds. Under specific conditions, however, volutes are removed (termed voluteless) to reduce flow losses and noise. In this paper, a generic voluteless centrifugal fan is investigated for the tonal noise generation at an off-design operation point. In contrast to typical tonal noise sources induced by the fan blades, we find out that another predominant source is the turbulence stemming from the clearance gap between the fan front shroud and the inlet duct. The turbulence evolves along with the front shroud and is swept downstream to interact with the top side of the blade leading edge. An obvious additional tone is observed at other than the blade passing frequency () and relevant harmonic frequencies. By coarsening the mesh resolution near the inlet gap and front shroud in the simulations, we artificially deactivate the gap turbulence. Consequently, the tone at disappears completely. The finding indicates that the interaction between the gap turbulence and blades accounts for the tone. As the gap turbulence exists near the front shroud, this rotating wall introduces rotational momentum into the turbulence due to skin friction. Hence, this tonal interaction frequency is smaller than with a decrement of the fan rotation frequency. To the authors' knowledge, this is the first time that voluteless centrifugal fans are studied for the gap-turbulence noise generation.
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July 2021
Research Article|
July 15 2021
Tonal noise of voluteless centrifugal fan generated by turbulence stemming from upstream inlet gap
M. Ottersten
;
M. Ottersten
a)
1
Department of Mechanics and Maritime Science, Chalmers University of Technology
, Gothenburg, Sweden
2
Swegon Operation
, Box 336, SE-401 25 Gothenburg, Sweden
a)Author to whom correspondence should be addressed: martin.ottersten@chalmers.se
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H.-D. Yao (姚华栋)
;
H.-D. Yao (姚华栋)
1
Department of Mechanics and Maritime Science, Chalmers University of Technology
, Gothenburg, Sweden
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L. Davidson
L. Davidson
1
Department of Mechanics and Maritime Science, Chalmers University of Technology
, Gothenburg, Sweden
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a)Author to whom correspondence should be addressed: martin.ottersten@chalmers.se
Physics of Fluids 33, 075110 (2021)
Article history
Received:
April 27 2021
Accepted:
June 18 2021
Citation
M. Ottersten, H.-D. Yao, L. Davidson; Tonal noise of voluteless centrifugal fan generated by turbulence stemming from upstream inlet gap. Physics of Fluids 1 July 2021; 33 (7): 075110. https://doi.org/10.1063/5.0055242
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