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Acoustic analysis of aft noise reduction techniques measured on a subsonic tip speed 50.8 cm (twenty inch) diameter fanSound data which were obtained during tests of a 50.8 cm diameter, subsonic tip speed, low pressure ratio fan were analyzed. The test matrix was divided into two major investigations: (1) source noise reduction techniques; and (2) aft duct noise reduction with acoustic treatment. Source noise reduction techniques were investigated which include minimizing second harmonic noise by varying vane/blade ratio, variation in spacing, and lowering the Mach number through the vane row to lower fan broadband noise. Treatment in the aft duct which includes flow noise effects, faceplate porosity, rotor OGV treatment, slant cell treatment, and splitter simulation with variable depth on the outer wall and constant thickness treatment on the inner wall was investigated. Variable boundary conditions such as variation in treatment panel thickness and orientation, and mixed porosity combined with variable thickness were examined. Significant results are reported.
Document ID
19800006843
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Stimpert, D. L. (General Electric Co. Cincinnati, OH, United States)
Clemons, A. (General Electric Co. Cincinnati, OH, United States)
Date Acquired
September 4, 2013
Publication Date
January 1, 1977
Subject Category
Aircraft Propulsion And Power
Report/Patent Number
R75AEG368
NASA-CR-134891
Accession Number
80N15102
Funding Number(s)
CONTRACT_GRANT: NAS3-18021
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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