Acoustic panel

Abstract

An acoustic panel for an aircraft, comprising: a sound attenuating sheet comprising a plurality of cavities, the sound attenuating sheet having a first surface, a second surface opposite the first surface, and an end surface connecting the first surface and the second surface; a first sheet extending over at least a portion of the first surface and over the end surface; and a second sheet extending over the second surface and the end surface, wherein the first sheet and the second sheet are connected such that tension can be transferred therebetween.

Description

TECHNICAL FIELD

[0001] The present invention relates to an acoustic panel and to an air inlet fairing comprising such an acoustic panel. BACKGROUND

[0002] It is desirable to isolate sound in one section of an aircraft from other sections of the aircraft and / or from the exterior of the aircraft. This is particularly important for the aircraft cabin, where the noise generated by the engines and the airflow at the engine inlets should be suppressed or attenuated to avoid excessive noise pollution.

[0003] Existing acoustic panels typically comprise a sound attenuating sheet positioned between two sheets, i.e. an inner and an outer sheet, one of which has an aperture to allow sound to enter the closed panel, but this arrangement often results in difficulties in sealing the acoustic panel to an adjacent panel due to the abrasive nature of the sound attenuating sheet. Furthermore, if more than one layer of sound attenuating sheet is to be used, it can be beneficial to securely hold the multiple layers of sound attenuating sheet together.

[0004] The present invention can improve manufacturability and robustness. SUMMARY

[0005] A first aspect of the present invention provides an acoustic panel for an aircraft, comprising: a sound attenuating sheet comprising a plurality of cavities, the sound attenuating sheet having a first surface, a second surface opposite the first surface, and an end surface connecting the first surface and the second surface; a first sheet extending over at least a portion of the first surface and over the end surface; and a second sheet extending over the second surface and the end surface, wherein the first sheet and the second sheet are connected such that a tensile force can be transferred therebetween.

[0006] With this arrangement, the connection arrangement of the first sheet and the second sheet allows the sound attenuating sheet to be held in compression, thus reducing the chance of the sound attenuating sheet separating or other damage to the sound attenuating sheet due to tensile stresses generated therein.

[0007] The first sheet and the second sheet can prevent the sound attenuating sheet from expanding in the thickness direction of the sound attenuating sheet. It is thus possible to prevent the first surface and the second surface of the sound attenuating sheet from further separating.

[0008] Furthermore, by having a portion of the sheet extend over the edge of the sound attenuating sheet, it is possible to improve the seal between the acoustic panel and an adjacent panel, feature or component.

[0009] The sound attenuating sheet can comprise two layers of sound attenuating sheet, each layer of sound attenuating sheet comprising a plurality of cavities, the two layers of sound attenuating sheet separated by a membrane. By providing two separate layers of sound attenuating sheet, the acoustic panel is able to attenuate sound over a greater range of frequencies, thereby potentially providing improved sound isolation.

[0010] The sound attenuating sheet can be a porous sheet such as a honeycomb sheet, or in the case of a single sheet, the single sound attenuating sheet can be a porous sheet such as a honeycomb sheet. By using a porous sheet, the individual cells can act as Helmholtz resonators, thereby attenuating sound at specific frequencies.

[0011] The first and second sheets can form a single continuous sheet. By using a single sheet to cover portions of the first and second surfaces of the sound attenuating sheet and portions of the end surfaces of the sound attenuating sheet, a uniform tension can be applied to the sheet such that the sound attenuating sheet has a uniform compression force. A simpler overall arrangement can also be provided which improves the use of manufacture.

[0012] The acoustic panel can further comprise a third sheet separate or discontinuous from the first and second sheets, extending over a portion of the first surface of the sound attenuating sheet and over a portion of the first sheet, the portion of the first sheet extending over at least a portion of the first surface of the sound attenuating sheet. By using a third sheet, the acoustic panel can be more easily manufactured and the single continuous sheet can have a C-shape into which the sound attenuating sheet can be slid and over which the third sheet can overlap the portion of the single continuous sheet extending over the first surface of the sound attenuating sheet. Overall, this can provide an acoustic panel which is more easily manufactured as the sound attenuating sheet can be more easily slid into place.

[0013] The first and second sheets can overlap over the end surfaces of the sound attenuating sheet. This arrangement provides an alternative possible method of manufacture in which the first and second sheets can be applied to the sound attenuating sheet simultaneously, meaning that the sound attenuating sheet does not need to be slid over the sheets.

[0014] The first and / or second sheets can comprise an inspection hole through which the end surface of the sound attenuating sheet can be seen. The provision of an inspection hole can allow personnel manufacturing the acoustic panel to ensure that the sound attenuating sheet is correctly placed and can allow the sound attenuating sheet to be inspected to detect damage.

[0015] The acoustic panel can further comprise a seal or other closing feature attached to the first and / or second sheets, wherein the respective sheet extends over the end surface of the sound attenuating sheet, the seal being arranged to abut an adjacent panel. By attaching the seal directly to the sheet extending over the end surface, as opposed to attaching the seal to an adjacent panel, the convenience and non-abrasive nature of the sheet at the end surface can be fully utilised.

[0016] The panel can be curved such that the first surface is a radially outer surface and the second surface is a radially inner surface, and the end surface has an annular or arcuate shape. By following the natural shape of these parts, this can improve the suitability of the acoustic panel for use in an aircraft cabin or fuselage.

[0017] The second sheet can be air permeable at a location where it extends over the second surface. This can improve the functioning of the sound attenuating panel, particularly when there is an open cell arranged to act as a Helmholtz resonator within the sound attenuating panel.

[0018] The end surface of the panel can be substantially orthogonal to the first and second surfaces. This can allow the panel to be more easily fitted to an existing adjacent panel.

[0019] The panel can be suitable for use in an air inlet fairing of an aircraft cabin or a different aircraft structure such as a fuselage where noise attenuation is required.

[0020] The first, second and third sheets can be composite sheets or can be metallic, for example aluminium.

[0021] According to a second aspect of the application, there is provided an air inlet fairing for an aircraft cabin comprising an acoustic panel according to the first aspect of the application.

[0022] Such an air inlet fairing can have improved sound insulation and can have an acoustic panel that is not susceptible to wear or damage.

[0023] The end surface of the sound attenuating panel can be arranged at the aft end of the inlet fairing. This can allow the acoustic panel to fit within an existing shaped aircraft cabin.

[0024] The air inlet fairing can further comprise a seal arranged to abut the acoustic panel at the aft end of the panel. BRIEF DESCRIPTION OF DRAWINGS

[0025] Embodiments of the application will now be described with reference to the accompanying drawings in which:

[0026] Figure 1 An aircraft cabin is shown;

[0027] Figure 2 A cross-sectional view of an acoustic panel according to an embodiment of the application is shown;

[0028] Figure 3 A cross-sectional view of an acoustic panel according to an embodiment of the application is shown; Figure 1 arranged within an aircraft cabin;

[0029] Figure 4A second embodiment of an acoustic panel according to the application is shown;

[0030] Figure 5 A cross-sectional view of a third embodiment of an aircraft panel according to the application is shown; and

[0031] Figure 6a 、 6b and 6c show the sequential steps of manufacturing an acoustic panel according to an embodiment of the application. DETAILED DESCRIPTION

[0032] Figure 1 An aircraft nacelle 10 is shown, the nacelle exterior being formed of three main parts: an inlet scoop 12, a fan case 14 and a thrust reverser 16. The purpose of the inlet scoop 12, which can be referred to as an inlet cowl, is to direct airflow into the fan and into the engine and to create an aerodynamically smooth surface for the airflow over the exterior of the aircraft nacelle 10. The airflow into the inlet cowl 12 creates a significant amount of noise, so the inlet cowl 12 should act to attenuate the noise and prevent excessive noise pollution outside the aircraft.

[0033] Figure 2 A cross-sectional view of an embodiment of an acoustic panel 100 for use within the inlet cowl is shown. The acoustic panel 100 has a sound attenuating sheet 102, which can be a honeycomb sheet or a different low density material such as a porous foam or sponge. The sound attenuating sheet 102 has three surfaces as shown, namely a top first surface 102a, a bottom second surface 102b and an end surface 102c. Figure 2

[0034] A composite layer 104 (see Figure 2 ) which can also be referred to as a sheet, extends over a portion of the first surface 102a, a portion of the second surface 102b and the end surface 102c. The sheet 104 thus forms a C-shape and covers at least a portion of all three of the above-mentioned surfaces of the sound attenuating sheet 102.

[0035] The sheet 104 can be considered to comprise three portions, namely a first portion 104a extending over at least a portion of the first surface 102a, a second portion 104b extending over at least a portion of the second surface 102b and a third portion 104c extending over the end surface 102c. Each respective portion 104a, 104b, 104c of the sheet 104 can be located over and abut the respective surface 102a, 102b, 102c of the sound attenuating sheet 102. The sheet 104 can be attached to the sound attenuating sheet 102 along its entire length by adhesive or can be attached only over a portion of its length.

[0036] ​Another sheet 108 extends over the top first surface of the sound attenuating sheet 102 and overlaps at least a portion of the first portion 104a of the sheet 104. The other sheet 108 can be referred to as a stepped or interleaved sheet. Within the scope of a nacelle, the surface of the acoustic panel 100 formed by the first portion 104a of the sheet 104 and the optional other sheet 108 can be a radially outer surface, and the second surface of the acoustic panel 100 opposite the first surface, the second surface of the acoustic panel 100 formed by the second portion 104b of the sheet 104 can be a radially inner surface.

[0037] The second portion 104b of the sheet 104 (or at least a portion of the second portion 104b) can include perforations or other apertures 106 for allowing fluid communication between the interior of the nacelle and the sound attenuating sheet 102. In the case where the sound attenuating sheet is formed of a honeycomb material, the honeycomb cells can be aligned such that they open to the second surface of the acoustic panel 100. The apertures 106 can allow the honeycomb cells to function as Helmholtz resonators.

[0038] The acoustic panel 100 further includes a seal 110 adhered to the sheet 104 where the sheet overlaps the end surface 102c of the sound attenuating sheet 102. The seal can optionally be a P-seal but can be a different shape or a different type of closure feature.

[0039] The sheet 104 can be considered a first sheet and a second sheet that can form a continuous sheet, and the other interleaved sheet 108 can be considered a third sheet.

[0040] When the sheet 104 is considered a first sheet and a second sheet, both the first sheet and the second sheet can be considered to extend over a portion of the end surface of the sound attenuating sheet, and the single continuous sheet can be considered two connected sheets such that a tensile force can be transferred between the two sheets. Alternatively, the two sheets can be adhered together or have interleaved ply that are connected to each other such that a tensile force can be transferred between them.

[0041] Figure 3 The acoustic panel 100 is shown fitted to the fan casing 200 via a flange 114 having bolt holes 116 for bolting the acoustic panel 100 to corresponding flanges 214 of the fan casing 200. The fan casing 200 can have corresponding fan casing panels 216.

[0042] Figure 3The sound attenuator 102 has two honeycomb sections: a first honeycomb section 121 and a second honeycomb section 122 separated by a diaphragm 103. The diaphragm 103 may be breathable. The sound attenuator 102 with two honeycomb sections separated by a diaphragm can be referred to as a 2-DOF sheet because the two different honeycomb sections can have honeycomb cells of the same or different sizes, thereby attenuating sounds of different frequencies.

[0043] The 2-DOF sound attenuator can benefit from the arrangement of sheets extending around it, as this prevents the sound attenuator from being subjected to tensile forces in the thickness direction, i.e., from the first surface 102a to the second surface 102b. This improves the robustness of the acoustic panel 100 by firmly holding the individual layers of the sound attenuator together.

[0044] exist Figure 3 It can also be seen that the seal 110 essentially seals the gap between the acoustic panel 100 and the fan housing panel 216.

[0045] Figure 4 An alternative embodiment of the acoustic panel 100 is shown. In this embodiment, two overlapping sheets are present at the end surface 102c of the sound attenuation sheet 102. This embodiment has a first sheet 104 and a second sheet 105, the first sheet 104 extending over a first surface 102a and at least a portion of the end surface 102c, and the second sheet 105 extending over a second surface 102b and at least a portion of the end surface 102c, the second sheet 105 overlapping the first sheet 104 in the region where the first sheet 104 extends over the end surface 102c. The first sheet 104 and the second sheet 105 may be co-cured or may be bonded together to bear tensile loads between them.

[0046] Alternatively, the first sheet 104 may overlap with the second sheet 105 such that the second sheet 105 is located between the first sheet 104 and the end surface 102c, and the acoustic panel can still be manufactured and function in substantially the same way.

[0047] Figure 5 Another alternative embodiment is shown, wherein the individual layers 115 of the first sheet 104 and the second sheet 105, which are composite sheets, can be staggered at the end surface 102c of the acoustic sheet 102. The first sheet 104 and the second sheet 105 can thus be connected to bear tensile loads between them.

[0048] Figure 6aA sound attenuator 102 is shown sliding in the direction indicated by arrow A, such that the end surface 102c can abut and mate with the third portion 104c of the sheet 104. A C-shape formed by the first portion 104a, the second portion 104b, and the third portion 104c of the sheet 104 is shown and shaped to fit tightly with the corresponding first surface 102a, second surface 102b, and end surface 102c of the sound attenuator 102, respectively.

[0049] Sheet 104 has inspection holes 120 arranged to allow the manufacturer to observe whether the sound attenuator 102 is properly seated within sheet 104 and / or maintenance personnel to inspect whether the sound attenuator 102 has been damaged during use. Inspection holes 120 may be aligned with diaphragm 103 to allow observation of any deterioration or damage between the layers of diaphragm 103 or sound attenuator 102, such as any deterioration or damage between the first honeycomb portion 121 and the second honeycomb portion 122.

[0050] Although the inspection hole 120 is shown only together with a single continuous piece 104 extending above the end surface 102c of the sound attenuation plate 102, it should be understood that Figure 4 and Figure 5 The embodiments may also include inspection holes, and the inspection holes may also be formed by making overlapping or staggered sheets.

[0051] Figure 6b The sound attenuator 102 is shown mounted and positioned against surface 102c. Inspection holes 120 can be aligned in this position to allow an engineer to inspect the contact between the sound attenuator 102 and the sheet 104.

[0052] Figure 6c A sound attenuator 102 is shown fitted within a sheet 104 after the application of interlaced sheets 108. The sheet 104 and the interlaced sheets 108 can be attached to the sound attenuator 102 by bolts or adhesive.

[0053] Although the invention has been described above with reference to one or more preferred embodiments, it will be understood that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. An acoustic panel for an aircraft, comprising: The sound attenuator (102) includes two sound attenuator layers (121, 122), each sound attenuator layer includes multiple cavities, the two sound attenuator layers are separated by a diaphragm (103), the sound attenuator has a first surface (102a), a second surface (102b) opposite to the first surface, and an end surface (102c) connecting the first surface and the second surface. A first sheet portion (104a) extends over and abuts over at least a portion of the first surface and at least a portion of the end surface. The second sheet portion (104b) extends over and abuts both of at least a portion of the second surface and at least a portion of the end surface. A third sheet portion (108), separate from the first sheet portion and the second sheet portion, includes a stepped portion extending over and directly adjacent to a portion of the first sheet portion, the portion of the first sheet portion extending over at least a portion of the first surface of the sound attenuator. The third sheet portion also includes a planar portion extending over and directly adjacent to the first surface of the sound attenuator, the planar portion of the third sheet portion being coplanar with the portion of the first sheet portion. The third sheet portion includes a transition portion extending between the planar portion and the stepped portion, wherein the first sheet portion and the second sheet portion form a single continuous sheet, enabling the transmission of tensile force between them. The panel is curved such that the first surface is a radially outer surface and the second surface is a radially inner surface, and the end surfaces have an annular or arcuate shape.

2. The acoustic panel according to claim 1, characterized in that, One or more of the sound attenuation sheets are one or more honeycomb sheets.

3. The acoustic panel according to claim 1 or 2, characterized in that, The first sheet portion and / or the second sheet portion include an inspection hole through which the end surface of the sound attenuation sheet can be viewed.

4. The acoustic panel according to claim 1 or 2, characterized in that, It also includes a seal attached to the first sheet portion and / or the second sheet portion, wherein the respective sheet portion extends above the end surface of the sound attenuation sheet, and the seal is arranged adjacent to the adjacent panel.

5. The acoustic panel according to claim 1 or 2, characterized in that, The second sheet portion is breathable where it extends above the second surface.

6. The acoustic panel according to claim 1 or 2, characterized in that, The end surface is substantially orthogonal to the first surface and the second surface.

7. The acoustic panel according to claim 1 or 2, characterized in that, The panel is suitable for use in the air inlet fairing of an aircraft cabin.

8. An air inlet fairing for an aircraft cabin, comprising an acoustic panel according to any one of claims 1 to 7.

9. The air inlet shroud according to claim 8, characterized in that, The end surface of the sound attenuator is located at the rear end of the inlet fairing.

10. The air inlet shroud according to claim 8 or 9, characterized in that, It may also include a seal arranged adjacent to the acoustic panel at the rear end of the panel.

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