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Acoustic performance of inlet suppressors on an engine generating a single mode

Author
Homyak, L.
Published
JAN 1, 1981.
Physical Description
1 electronic document
Additional Creators
Heidelberg, L. J. and Rice, E. J.
Online Version

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Unclassified, Unlimited, Publicly available.
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Summary
Three single degree of freedom liners with different open area ratio face sheets were designed for a single spinning mode in order to evaluate an inlet suppressor design method based on mode cutoff ratio. This mode was generated by placing 41 rods in front of the 28 blade fan of a JT15D turbofan engine. At the liner design this near cutoff mode has a theoretical maximum attenuation of nearly 200 dB per L/D. The data show even higher attenuations at the design condition than predicted by the theory for dissipation of a single mode within the liner. This additional attenuation is large for high open area ratios and should be accounted for in the theory. The data show the additional attenuation to be inversely proportional to acoustic resistance. It was thought that the additional attenuation could be caused by reflection and modal scattering at the hard to soft wall interface. A reflection model was developed, and then modified to fit the data. This model was checked against independent (multiple pure tone) data with good agreement.
Other Subject(s)
Collection
NASA Technical Reports Server (NTRS) Collection.
Note
Document ID: 19810024425.
Accession ID: 81N32968.
NASA-TM-82697.
AIAA PAPER 81-1965.
E-980.
Aeroacoustics Conf.; 5-7 Oct. 1981; Palo Alto, CA; United States.
Terms of Use and Reproduction
No Copyright.
View MARC record | catkey: 15717977