Sound absorbing panel, air intake structure, nacelle and aircraft

Abstract

The invention relates to a sound absorbing panel, an air intake structure, a nacelle and an aircraft, the sound absorbing panel comprising: an inner skin crossed by holes and intended to be oriented towards a passage in which a fluid flows; a heating mat consisting of strips fixed to the inner skin on the side opposite to the passage and oriented in a first direction, wherein two adjacent strips are spaced apart from each other so as to leave a slot between them; a base fixed to the strips on the side opposite to the inner skin, wherein the base comprises grooves on the side of the strips, the grooves extending in a second direction different from the first direction, and wherein the base has ribs between two successive grooves; a honeycomb core fixed to the base on the side opposite to the strips, and; an outer panel fixed to the honeycomb core on the side opposite to the base. Such a sound absorbing panel thus makes it possible to obtain a de-icing surface and better noise attenuation.

Description

Technical Field

[0001] The present invention relates to a sound-absorbing panel having a honeycomb core and a de-icing system, an air intake structure of an aircraft nacelle including such a sound-absorbing panel, a nacelle including such an air intake structure, and an aircraft including at least one such nacelle. Background Technology

[0002] Sound-absorbing panels are used in many technical fields, especially in the aerospace industry.

[0003] The aircraft's turbine engine includes a nacelle in which the engine assembly is housed. The annular nacelle has an air intake structure at the front.

[0004] The air intake structure generally consists of an internal surface and an external surface that contacts the outside air, with the internal surface defining the passageway that forms the fan duct. The main function of the air intake structure is to ensure that the aerodynamic flow of air is directed towards both the fan duct and the outside of the nacelle.

[0005] The air intake structure typically includes an air intake lip, a front reinforcing frame, and an acoustic panel.

[0006] The inlet lip has a U-shaped cross-section that opens toward the rear. This inlet lip forms the outer cladding of the forward portion of the inlet structure and ensures the distribution of air between the portion entering the fan duct and the portion flowing around the nacelle.

[0007] The front reinforcing frame also has a U-shaped cross-section that opens towards the rear, and this front reinforcing frame is positioned inside the air intake lip and at the rear. The front reinforcing frame provides mechanical strength to the forward section of the nacelle and helps maintain its shape and dimensions.

[0008] The acoustic panel forms the inner cladding of the nacelle behind the air intake lip and on the side of the fan duct. Therefore, the acoustic panel constitutes part of the internal surface.

[0009] The acoustic panel has a structure suitable for attenuating noise generated by the engine, and especially by the fan. This acoustic panel is of a composite sandwich type, and integrates a honeycomb core between inner and outer walls. The inner wall defines the fan duct and extends the intake lip, while the outer wall is located inside the intake structure but oriented outwards toward the nacelle.

[0010] The volume between the intake lip and the front reinforcing frame allows for the circulation of hot airflow, which ensures de-icing of the intake lip.

[0011] While this intake structure was perfectly satisfactory during its use, the expectation was to find a structure that would allow for an increased attenuation frequency range and a larger de-icing and sound-absorbing surface. Summary of the Invention

[0012] The purpose of this invention is to provide a sound-absorbing panel that offers better noise attenuation and de-icing.

[0013] To this end, a sound-absorbing panel is proposed, the sound-absorbing panel comprising:

[0014] - Inner skin, which is perforated and oriented toward the channels through which fluid flows.

[0015] - A heating pad comprising strips fixed to the inner skin on the side opposite to the channel and oriented in a first direction, wherein two adjacent strips are spaced apart from each other to leave a slot between them.

[0016] - A substrate, the substrate being fixed to the strip on a side opposite to the inner skin, wherein the substrate includes grooves on the strip side, the grooves extending in a second direction different from the first direction, and wherein the substrate has ribs between two successive grooves.

[0017] - A honeycomb core, the honeycomb core being fixed to the substrate on the side opposite to the strip, and

[0018] - An outer panel, which is fixed to the honeycomb core on the side opposite to the substrate.

[0019] This type of sound-absorbing panel thus achieves a de-icing surface and better noise attenuation.

[0020] Advantageously, the strips are integrated with each other.

[0021] Advantageously, the first direction is perpendicular to the second direction.

[0022] Advantageously, the total thickness of the substrate at the level of the rib is at least 4 mm.

[0023] Advantageously, each strip includes a resistive element and an electrically insulating element therein, the resistive element generating heat when current passes through it.

[0024] Advantageously, each strip is traversed by a pipe through which heated heat transfer fluid flows.

[0025] Advantageously, the inner skin is made of a thermally conductive material.

[0026] The present invention also proposes an air intake structure for a nacelle of an aircraft, the air intake structure defining a channel and including a lip and a first sound-absorbing panel according to one of the aforementioned variants, the lip having a rearwardly oriented U-shaped cross section, the first sound-absorbing panel being fixed behind the lip and defining the channel.

[0027] Advantageously, the air inlet structure includes a second sound-absorbing panel fixed behind the first sound-absorbing panel and includes a honeycomb core fixed between an inner skin with holes and oriented toward the channel and an outer panel oriented in the opposite direction.

[0028] The present invention also proposes a nacelle comprising an air intake structure at the front according to one of the aforementioned variants.

[0029] The present invention also proposes an aircraft comprising at least one nacelle according to the preceding variant. Attached Figure Description

[0030] The above and other features of the invention will become clearer after reading the following description of exemplary embodiments, which is given with reference to the accompanying drawings, in which:

[0031] Figure 1 A side view of the aircraft according to the present invention is shown.

[0032] Figure 2 This is a cross-sectional side view of the air inlet structure according to the present invention.

[0033] Figure 3 This is an exploded perspective view of the sound-absorbing panel according to the present invention, and

[0034] Figure 4 This is a perspective view of a heating pad according to a variant embodiment. Detailed Implementation

[0035] In the following description, the position-related terms refer to the aircraft in a position of forward motion, i.e., such as... Figure 1 The aircraft shown is used for this purpose.

[0036] Figure 1 An aircraft 10 including at least one turbine engine 20 is shown.

[0037] Throughout the following description, by convention, direction X corresponds to the longitudinal direction of turbine engine 20, which is parallel to the longitudinal axis X of turbine engine 20. On the other hand, direction Y corresponds to the direction lateral to turbine engine 20, and direction Z corresponds to the vertical or height direction. These three directions X, Y, and Z are orthogonal to each other.

[0038] The turbine engine 20 conventionally includes a nacelle 19, which includes an air intake structure 22 at the front, the air intake structure including a lip defining the interior and exterior of the nacelle 19. The lip extends inward through an inner wall that extends around a channel that directs air toward engine components including a fan and the like.

[0039] Figure 2 An air intake structure 22 is shown, which includes a lip 24 having a U-shaped cross-section positioned rearward and generally having an annular shape. The air intake structure 22 defines a passage 26 that directs air toward engine components, and in particular toward the fan.

[0040] The lip 24 defines the exterior 25 and interior 26 of the nacelle 19. The interior 26 corresponds to the passage 26.

[0041] In the embodiment of the invention described herein, the air inlet structure 22 includes a first sound-absorbing panel 28 and a second sound-absorbing panel 30 surrounding a channel 26, the first and second sound-absorbing panels defining the channel 26. The first sound-absorbing panel 28 is fixed behind a lip 24 up to the second sound-absorbing panel 30. The second sound-absorbing panel 30 is fixed behind the first sound-absorbing panel 28.

[0042] In the case of the present invention, the reinforcing frame has been eliminated, and the air inlet structure 22 of the present invention is enhanced by the presence of a first sound-absorbing panel 28, which also has structural capabilities.

[0043] The second sound-absorbing panel 30 includes a honeycomb core 34, which is fixed between an inner skin 38 oriented toward the channel 26 and an outer panel 42 oriented in the opposite direction. The inner skin 38 is perforated to allow sound waves to propagate into the core 34 so that they are attenuated there.

[0044] The second sound-absorbing panel 30 is provided to attenuate high frequencies in the range of 1000 Hz to 4000 Hz. For this purpose, the inner skin 38 of the second sound-absorbing panel 30 has a thickness on the order of 0.9 mm to 2 mm, and the holes 46 therefore also have a length of at least 0.9 mm to 2 mm.

[0045] Figure 3 An exploded view of the first sound-absorbing panel 28 is shown.

[0046] The first sound-absorbing panel 28 includes an inner skin 36 oriented toward the channel 26 and perforated by holes that allow sound waves to propagate through the inner skin 36. Typically, the inner skin 36 is oriented toward the channel 26 in which fluid flows. The inner skin 36 can be, for example, of a porous element (e.g., a porous fabric or mesh).

[0047] The first sound-absorbing panel 28 also includes a heating pad 48, which is composed of strips 50 fixed to the inner skin 36 on the side opposite to the channel 26. All strips 50 are oriented in a first direction 52. Two adjacent strips 50 are spaced apart from each other to leave slots 51 between them. Holes in the inner skin 36 open into these slots 51, which allow sound waves to propagate.

[0048] The heating pad 48 allows for de-icing of the inner skin 36 located in the channel 26.

[0049] The first sound-absorbing panel 28 also includes a substrate 53 fixed to the strip 50 on the side opposite to the inner skin 36. The substrate 53 includes grooves 54 on the side of the strip 50 extending in a second direction 56, which is different from (specifically perpendicular to) the first direction 52. The substrate 53 thus has ribs 58 between two successive grooves 54, parallel to the second direction 56. The substrate 53 is thus supported to the strip 50 by the ribs 58.

[0050] The substrate 53 is also through a hole that allows sound waves to propagate.

[0051] The total thickness of the substrate 53 at the level of the rib 58 is on the order of 0.9 mm to 5 mm, and the depth of the hole through the rib 58 is therefore also equal to 0.9 mm to 5 mm. The thickness of the substrate 53 at the level of the groove 54 is, for example, on the order of 0.3 mm to 0.9 mm, and therefore the depth of the hole through the substrate is also 0.3 mm to 0.9 mm. According to a particular embodiment, the total thickness of the substrate 53 at the level of the rib 58 is at least 4 mm.

[0052] The first sound-absorbing panel 28 also includes a honeycomb core 32, which is fixed to the substrate 53 on the side opposite to the strip 50.

[0053] The first sound-absorbing panel 28 also includes an outer panel 40, which is fixed to the honeycomb core 32 on the side opposite to the substrate 53.

[0054] This structure allows for better noise attenuation because sound waves propagate through the inner skin 36, slots 51, grooves 54, substrate 53, and finally through the honeycomb core 32. The continuous holes with smaller diameters and larger spaces (slots 51 and grooves 54) create variations that slow down sound waves and thus attenuate noise.

[0055] Furthermore, the presence of slot 51 and groove 54 allows the hole to remain open even after assembly, thus increasing the percentage of open surface area.

[0056] When the thickness is at least 4 mm, the substrate 53 at the level of rib 58 allows for the attenuation of low frequencies in the range of 300 Hz to 600 Hz. The volume of the cells in which the holes of the substrate 53 appear in the honeycomb core 32 and the depth of these holes allow for the selection of the frequencies to be attenuated. For example, with a hole depth of 4 mm and a cell height of 40 mm, frequencies around 500 Hz are attenuated.

[0057] Therefore, by using sound-absorbing panels based on two different technologies, the attenuation of sound waves is greater and the frequency range of attenuation is also expanded compared to existing technologies.

[0058] The inner skin 36 of the first sound-absorbing panel 28, oriented toward the channel 26, is flush with the inner skin 38 of the second sound-absorbing panel 30, oriented toward the channel 26, in order to create an aerodynamic surface.

[0059] The inner skin 38 of the second sound-absorbing panel 30 preferably also includes a heat source embedded in the mass of the inner skin 38.

[0060] Each strip 50 includes, for example, a resistive element 60 and an electrically insulating element 62 embedded therein, the resistive element generating heat when current passes through it.

[0061] Each strip 50 can be passed through a fitting 64 through which a heat transfer fluid (e.g., hot air) flows.

[0062] To facilitate heat transfer, the inner skin 36 is made of a thermally conductive material.

[0063] Thermal insulators can be arranged on certain sides of strip 50 to restrict heat propagation in certain directions. Thermal conductors can also be arranged on certain sides of strip 50 to facilitate heat propagation in certain directions.

[0064] Figure 4 A heating pad 448 according to a particular embodiment is shown, wherein, to facilitate the operation of the heating pad 448, the strips 50 are integrally formed with each other, for example, by bridging portions 66 passing through slots 51. The heating pad 448 thus becomes a perforated sheet.

Claims

1. A sound-absorbing panel (28), the sound-absorbing panel comprising: Inner skin (36), which is perforated and oriented toward the channel (26) through which fluid flows, Heating pads (48, 448) are made of strips (50) that are fixed to the inner skin (36) on the side opposite to the channel (26) and oriented in a first direction (52), wherein two adjacent strips (50) are spaced apart from each other to leave a slot (51) between them. A substrate (53) is fixed to the strip (50) on the side opposite to the inner skin (36), wherein the substrate (53) includes a groove (54) on the side where the strip (50) is located, the groove extending in a second direction (56) different from the first direction (52), and wherein the substrate (53) has a rib (58) between two successive grooves (54). A honeycomb core (32) is fixed to the substrate (53) on the side opposite to the strip (50), and An outer panel (40) is fixed to the honeycomb core (32) on the side opposite to the substrate (53).

2. The sound-absorbing panel (28) according to claim 1, characterized in that, The strips (50) are integrated with each other.

3. The sound-absorbing panel (28) according to any one of claims 1 and 2, characterized in that, The first direction (52) is perpendicular to the second direction (56).

4. The sound-absorbing panel (28) according to any one of claims 1 to 2, characterized in that, The total thickness of the substrate (53) at the level of the rib (58) is at least 4 mm.

5. The sound-absorbing panel (28) according to any one of claims 1 to 2, characterized in that, Each strip (50) includes a resistive element (60) and an electrically insulating body (62) in which the resistive element (60) is embedded, the resistive element generating heat when current passes through it.

6. The sound-absorbing panel (28) according to any one of claims 1 to 2, characterized in that, Each strip (50) is passed through a fitting (64) through which heated heat transfer fluid flows.

7. The sound-absorbing panel (28) according to any one of claims 1 to 2, characterized in that, The inner skin (36) is made of a thermally conductive material.

8. An air inlet structure (22) for a nacelle (19) of an aircraft (10), the air inlet structure (22) defining a passage (26) and including a lip (24) and a sound-absorbing panel (28) according to any one of claims 1 to 7, the sound-absorbing panel (28) being a first sound-absorbing panel, the lip having a rearwardly oriented U-shaped cross section, the first sound-absorbing panel being fixed behind the lip (24) and defining the passage (26).

9. The air inlet structure (22) according to claim 8, characterized in that, The air inlet structure further includes a second sound-absorbing panel (30) fixed behind the first sound-absorbing panel, and the second sound-absorbing panel (30) includes a honeycomb core (34). The honeycomb core of the second sound-absorbing panel (30) is fixed between the inner skin (38) of the second sound-absorbing panel (30) and the outer panel (42) of the second sound-absorbing panel (30). The inner skin (38) of the second sound-absorbing panel (30) has a hole and is oriented toward the channel (26). The outer panel (42) of the second sound-absorbing panel (30) is oriented in the opposite direction to the inner skin (38) of the second sound-absorbing panel (30).

10. A nacelle (19) comprising an air intake structure (22) at the front according to any one of claims 8 to 9.

11. An aircraft (10) comprising at least one nacelle according to claim 10.

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