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Some design philosophy for reducing the community noise of advanced counter-rotation propellersAdvanced counter-rotation propellers have been indicated as possibly generating an unacceptable amount of noise for the people living near an airport. This report has explored ways to reduce this noise level, which is treated as being caused by the interaction of the upstream propeller wakes and vortices with the downstream propeller. The noise reduction techniques fall into two categories: (1) reducing the strength of the wakes and vortices, and (2) reducing the response of the downstream blades to them. The noise from the wake interaction was indicated as being reduced by increased propeller spacing and decreased blade drag coefficient. The vortex-interaction noise could be eliminated by having the vortex pass over the tips of the downstream blade, and it could be reduced by increased spacing or decreased initial circulation. The downstream blade response could be lessened by increasing the reduced frequency parameter omega or by phasing of the response from different sections to have a mutual cancellation effect. Uneven blade to blade spacing for the downstream blading was indicated as having a possible effect on the annoyance of counter-rotation propeller noise. Although there are undoubtedly additional methods of noise reduction not covered in this report, the inclusion of the design methods discussed would potentially result in a counter-rotation propeller that is acceptably quiet.
Document ID
19860004538
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Dittmar, J. H.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 5, 2013
Publication Date
August 1, 1985
Subject Category
Acoustics
Report/Patent Number
NAS 1.15:87099
E-2692
NASA-TM-87099
Accession Number
86N14007
Funding Number(s)
PROJECT: RTOP 505-45-58
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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