Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like
Patent
1990-05-21
1996-08-06
Epstein, Henry F.
Stock material or miscellaneous articles
Structurally defined web or sheet
Honeycomb-like
527931, 181292, 428118, 493966, B32B 312
Patent
active
055431984
DESCRIPTION:
BRIEF SUMMARY
This application is a continuation of PCT/GB89/00841, filed Jul. 24, 1989, designating the United States.
The present invention relates to noise attenuation panels and is particularly, although not exclusively, concerned with noise attenuation panels for use in the attenuation of noise in aero engines.
It has previously been proposed to provide noise attenuation panels for reducing turbine engine noise, the panels being formed as integral parts of the aero engine structure. For example, the panels may form part of a cowling surrounding a turbine engine inlet duct or be placed adjacent a high turbulence region of the fan of a turbo fan engine.
In particular, prior specification GB 2056367A describes a process for producing broad band noise attenuation panels for use in such environments, where they are used as skin surfaces adjacent the engine.
The panel of GB 2056367A comprises a central honeycomb core having a plurality of open-ended juxtaposed cells, an imperforate backing sheet extending across the ends of the cells at the rear thereof, a perforate inner facing sheet extending across the ends of the cells at the front of the core and an outer facing sheet of fibrous or woven material bonded to the inner facing sheet, which is said to improve the sound attenuation characteristics.
The preferred material for the core and the backing and inner facing sheets of the panel of GB 2056367A is aluminium due to its weight versus strength and cost characteristics, although it is envisaged that other metals or materials could be used where these requirements are not considered.
The inner facing sheet for the panel of GB 2056367A is perforated with a plurality of small perforations and the outer facing sheet is adhesively bonded to the surface of the perforated inner facing sheet. The preferred material for the woven outer sheet is stainless steel, which is woven as a Dutch twill fabric, although it is stated that other types of material and weave pattern may be utilised.
It has furthermore previously been proposed in patent specification GB 2122540A to provide a noise attenuation panel of the form described in GB 2056367A, except insofar that the apertured inner facing sheet is formed from a carbon fibre/resin matrix composite material. In particular, the apertured inner facing sheet is formed as an open weave material in which the apertures are constituted by hexagonal openings between three sets of carbon threads mutually arranged at 60.degree. to one another. The porous woven outer facing sheet is, however, made of stainless steel.
The use of a composite material for the apertured inner facing sheet of the panel disclosed in GB 2122540A has, it is stated, advantages over the use of materials such as aluminium. The apertures can for example be formed while the resin matrix of the composite is in a partially cured condition, leading to a far less expensive process than forming perforations in a metal sheet. Furthermore, the resin matrix of the composite material could, it is stated, itself provide an adhesive medium by which the porous outer facing sheet is secured to the apertured inner facing sheet.
While the noise attenuation panel disclosed in GB 2122540A has been found to be successful for use in aero engine environments, it suffers from a number of disadvantages. In particular, it has been found that the use of a woven material for the porous outer facing sheet gives rise to a relatively high resistance to high speed air flow over the surface and that sound attenuation is effective over a relatively narrow band of frequencies. Furthermore, the problem of metal galvanic corrosion is resent where the material used is stainless steel.
It is an object of the present invention to provide a noise attenuation panel which does not suffer from the above-mentioned disadvantages of the noise attenuation panels previously proposed and as hereinbefore set forth or does not suffer to the same extent from those disadvantages.
According to a first aspect of the present invention there is provided a noise attenuation panel c
REFERENCES:
patent: 3673057 (1972-06-01), Fairbanks
patent: 3819007 (1974-06-01), Wirt et al.
patent: 3831710 (1974-08-01), Wirt
patent: 3977492 (1976-08-01), Hankel
patent: 4111081 (1978-09-01), Hilliard et al.
patent: 4318453 (1982-03-01), Rose et al.
patent: 4384020 (1983-05-01), Beggs
patent: 4465725 (1984-08-01), Riel
patent: 4933131 (1990-06-01), Okey et al.
patent: 4957577 (1990-09-01), Huebner
Epstein Henry F.
Short Brothers PLC
LandOfFree
Noise attenuation panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Noise attenuation panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Noise attenuation panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2189719