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Acoustic modal analysis of a full-scale annular combustorAn acoustic modal decomposition of the measured pressure field in a full scale annular combustor installed in a ducted test rig is described. The modal analysis, utilizing a least squares optimization routine, is facilitated by the assumption of randomly occurring pressure disturbances which generate equal amplitude clockwise and counter-clockwise pressure waves, and the assumption of statistical independence between modes. These assumptions are fully justified by the measured cross spectral phases between the various measurement points. The resultant modal decomposition indicates that higher order modes compose the dominant portion of the combustor pressure spectrum in the range of frequencies of interest in core noise studies. A second major finding is that, over the frequency range of interest, each individual mode which is present exists in virtual isolation over significant portions of the spectrum. Finally, a comparison between the present results and a limited amount of data obtained in an operating turbofan engine with the same combustor is made. The comparison is sufficiently favorable to warrant the conclusion that the structure of the combustor pressure field is preserved between the component facility and the engine. Previously announced in STAR as N83-21896
Document ID
19830052268
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Karchmer, A. M.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 11, 2013
Publication Date
April 1, 1983
Subject Category
Acoustics
Report/Patent Number
AIAA PAPER 83-0760
Accession Number
83A33486
Distribution Limits
Public
Copyright
Other

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