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Impact of bypass-duct bifurcations on fan noise

Holewa, Axel and Weckmüller, Ch. and Guerin, S. (2012) Impact of bypass-duct bifurcations on fan noise. In: Proceedings 18th AIAA / CEAS Aeroacoustics Conference (33rd Aeroacoustics Conference) (Vol. 1 of 5). AIAA. 18th AIAA/CEA Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference), 04. Juni - 06. Juni 2012, Colorado Springs, USA. ISBN 978-1-62276-215-6

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The present work deals with the impact of the potential field of bypass-duct bifurcations on the turbofan tonal noise. The investigation is carried out at take-off condition on a typical rotor-stator fan stage extended with struts, upper and lower bifurcations. the results of quasi-3D steady and unsteady RANS calculations at 60% rotor span are presented and compared to the isolated configuration. Two sorts of impact on noise are observed: on the one hand a direct impact on rotor noise due to the periodic loading of the rotor interacting with the circumferentially non-uniform pressure field imposed backwards by the bifurcations; on the other hand an indirect impact on the noise generation at the stator due to the deformation of the rotor wakes under the influence of the potential field of the bifurcations. In the present study, tonal noise due to the rotor-wake interaction with the stator vanes appears to be dominant in the bypass duct. Under the effect of the bypass components a dramatic change in the azimuthal structure of the acoustic field is observed at the blade passing frequency and ist harmonics with a significant increase of the sound power level. It is expected that the bypass components will jeopardise the cut-off design of the blade passing frequency in the full-3D configuration. In the inlet, the shocks built on the blades do not propagate as the corresponding pressure patterns are cut-off. However one can observe that the shock position moves back and forth during one revolution which certainly should influence the generation and propagation of buzz-saw noise going to the full-3D configuration.

Item URL in elib:https://elib.dlr.de/77536/
Document Type:Conference or Workshop Item (Speech, Paper)
Title:Impact of bypass-duct bifurcations on fan noise
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Journal or Publication Title:Proceedings 18th AIAA / CEAS Aeroacoustics Conference (33rd Aeroacoustics Conference)
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:Tonal noise, fan stage, bypass duct, bifurcations, RANS
Event Title:18th AIAA/CEA Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)
Event Location:Colorado Springs, USA
Event Type:international Conference
Event Dates:04. Juni - 06. Juni 2012
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Virtual Engine and Validation Methods (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology > Engine Acoustic
Deposited By: Kaur, Balbir
Deposited On:10 Jan 2013 10:18
Last Modified:27 Jun 2013 08:52

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