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

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

Content Provider	NASA Technical Reports Server (NTRS)
Author	Rice, E. J. Heidelberg, L. J. Homyak, L.
Copyright Year	1981
Description	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.
File Size	1255252
Page Count	23
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_19810024425
Archival Resource Key	ark:/13960/t7zm05f8c
Language	English
Publisher Date	1981-01-01
Access Restriction	Open
Subject Keyword	Acoustics Noise Propagation Engine Noise Spin Noise Reduction Engine Inlets Linings Turbofan Engines Aircraft Engines Aeroacoustics Acoustic Attenuation Propagation Modes Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Article

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