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Validation of the Predicted Circumferential and Radial Mode Sound Power Levels in the Inlet and Exhaust Ducts of a Fan Ingesting Distorted InflowFan inflow distortion tone noise has been studied computationally and experimentally. Data from two experiments in the NASA Glenn Advanced Noise Control Fan rig have been used to validate acoustic predictions. The inflow to the fan was distorted by cylindrical rods inserted radially into the inlet duct one rotor chord length upstream of the fan. The rods were arranged in both symmetric and asymmetric circumferential patterns. In-duct and farfield sound pressure level measurements were recorded. It was discovered that for positive circumferential modes, measured circumferential mode sound power levels in the exhaust duct were greater than those in the inlet duct and for negative circumferential modes, measured total circumferential mode sound power levels in the exhaust were less than those in the inlet. Predicted trends in overall sound power level were proven to be useful in identifying circumferentially asymmetric distortion patterns that reduce overall inlet distortion tone noise, as compared to symmetric arrangements of rods. Detailed comparisons between the measured and predicted radial mode sound power in the inlet and exhaust duct indicate limitations of the theory.
Document ID
20120003367
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Koch, L. Danielle
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 25, 2013
Publication Date
February 1, 2012
Subject Category
Acoustics
Report/Patent Number
E-18008
AIAA Paper-2011-2808
NASA/TM-2012-217253
Meeting Information
Meeting: 17th Aeroacoustics Conference
Location: Portland, OR
Country: United States
Start Date: June 5, 2011
End Date: June 8, 2011
Sponsors: American Inst. of Aeronautics and Astronautics, Confederation of European Aerospace Societies
Funding Number(s)
WBS: WBS 561581.02.08.03.18.11
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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