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Basic research in fan source noise: Inlet distortion and turbulence noiseA widely recognized problem in jet engine fan noise is the discrepancy between inflight and static tests. This discrepancy consists of blade passing frequency tones, caused by ingested turbulence that appear in the static tests but not in flight. To reduce the ingested distortions and turbulence in an anechoic chamber, a reverse cone inlet is used to guide the air into the fan. This inlet also has provisions for boundary layer suction and is used in conjunction with a turbulence control structure (TCS) to condition the air impinging on the fan. The program was very successful in reducing the ingested turbulence, to the point where reductions in the acoustic power at blade passing frequency are as high as 18 db for subsonic tip speeds. Even with this large subsonic tone suppression, the supersonic tip speed tonal content remains largely unchanged, indicating that the TCS did not appreciably attenuate the noise but effects the generation via turbulence reduction. Turbulence mapping of the inlet confirmed that the tone reductions are due to a reduction in turbulence, as the low frequency power spectra of the streamwise and transverse turbulence were reduced by up to ten times and 100 times, respectively.
Document ID
19790006704
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Kantola, R. A.
(General Electric Co. Schenectady, NY, United States)
Warren, R. E.
(General Electric Co. Schenectady, NY, United States)
Date Acquired
September 3, 2013
Publication Date
December 1, 1978
Subject Category
Acoustics
Report/Patent Number
NASA-CR-159451
SRD-78-186
Report Number: NASA-CR-159451
Report Number: SRD-78-186
Accession Number
79N14875
Funding Number(s)
CONTRACT_GRANT: NAS3-17853
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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