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Forward rotor vortex effects on counter rotating propeller noiseThree configurations of a model counter rotating propeller manipulate the blade tip flow by: placing the CRP at angle of attack, installing shrouds, and turning the upstream blades to provide forward sweep. Flow visualization and flow measurements with thermal anemometry show no evidence of a tip vortex; however, a leading edge vortex was detected on aft swept blades. The modifications served to alter the strength and/or path of the leading edge vortex. The vortical flow is eliminated by forward sweep on the upstream propeller blades. Far field acoustic data from each test indicate only small influences on the level and directivity of the BPFs. The interaction tone at the sum of the two BPF's was significantly altered in a consistent manner. As the vortex system varied, the interaction tone was affected: far field noise levels in the forward quandrant increased and the characteristic noise minimum near the plane of rotation became less pronounced and in some cases were eliminated. If the forward propeller leading edge vortex system does not impact the rear propeller in the standard manner, a net increase in the primary interaction tone occurs for the model tested. If the leading edge vortex is removed, the interaction tone increases.
Document ID
19930035224
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Laur, Michele
(NASA Lewis Research Center Cleveland, OH, United States)
Squires, Becky
(NASA Lewis Research Center Cleveland, OH, United States)
Nagel, Robert T.
(North Carolina State Univ. Raleigh, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1992
Publication Information
Publication: In: DGLR(AIAA Aeroacoustics Conference, 14th, Aachen, Germany, May 11-14, 1992, Proceedings. Vol. 2 (A93-19126 05-71)
Publisher: Deutsche Gesellschaft fuer Luft- und Raumfahrt
Subject Category
Aerodynamics
Accession Number
93A19221
Funding Number(s)
CONTRACT_GRANT: NAG3-855
Distribution Limits
Public
Copyright
Other

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