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Fan noise research at NASAResults of recent NASA research to reduce aircraft turbofan noise are described. As the bypass ratio of a turbofan engine increases from 5 to as much as 20, the dominant source of engine noise is the fan. A primary mechanism of tone noise generation is the rotor blade wakes interacting with downstream stator vanes. Methods of analyzing rotor-stator tone noise generation are described and sample results are given. The role of an acoustic modal description is emphasized. Wind tunnel tests of model fans and nacelles are described including a novel rotating microphone technique for modal measurement. Sample far field results are given showing the effects of inlet length, and modal measurements are shown which point to a new generation mechanism. Concepts for active fan noise control at the source are addressed. Implications of the research which have general relevance to fan noise generation and control are discussed.
Document ID
19950004847
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Groeneweg, John F.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 17, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Inst. of Noise Control Engineering, Noise Con 1994: Proceedings of the 1994 National Conference on Noise Control Engineering. Progress in Noise Control for Industry
Subject Category
Acoustics
Accession Number
95N11260
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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