阅读说明：本技术 具有斜刺穿的蜂窝状结构的噪音降低装置 (Noise reduction device with obliquely pierced honeycomb structure ) 是由 蒂埃里·乔治·保罗·帕潘 于 2020-01-22 设计创作，主要内容包括：本发明涉及一种用于飞行器涡轮发动机的噪音降低装置(18),所述装置具有呈层(20,22,24)的堆叠形式的结构,使得由复合材料制成的第一表层和第二表层(22,24)形成第一外层和第二外层(22,24),这些外层(22,24)大致彼此平行并且包围中心层(20)。该中心层具有蜂窝状结构,该蜂窝状结构具有隔板(26),该隔板从第一外层(22)横向地延伸到第二外层(24),以形成空腔(28)。该隔板(26)由粘弹性材料制成,并且与第一外层和第二外层(22,24)形成为锐角的倾斜角(α)。(The invention relates to a noise-reducing device (18) for an aircraft turbine engine, said device having a structure in the form of a stack of layers (20, 22, 24) such that first and second skin layers (22, 24) made of composite material form first and second outer layers (22, 24), these outer layers (22, 24) being substantially parallel to each other and enclosing a central layer (20). The center layer has a honeycomb structure with baffles (26) extending transversely from the first outer layer (22) to the second outer layer (24) to form cavities (28). The separator (26) is made of a viscoelastic material and forms an acute angle of inclination (α) with the first and second outer layers (22, 24).)

1. A noise reducing device (18) for an aircraft turbine engine, the device having a structure in the form of a stack of layers (20, 22, 24) such that first and second skin layers (22, 24) made of composite material form first and second outer layers (22, 24), the first and second outer layers (22, 24) being substantially parallel to each other, the first and second outer layers (22, 24) enclosing a central layer (20) having a honeycomb structure comprising a partition (26) extending transversely from the first outer layer (22) to the second outer layer (24) to form a cavity (28).

Characterized in that the partitions (26) of the honeycomb structure of the central layer (20) are made of a viscoelastic material and in that the partitions (26) form an acute angle of inclination (a) with the first and second outer layers (22, 24).

2. Device (18) according to the preceding claim, characterized in that said baffle (26) of said central layer (20) is flat and has the same inclination angle (a) as said first and second outer layers (22, 24), which is comprised between 10 and 50 degrees.

3. Device (18) according to any one of the preceding claims, characterized in that said viscoelastic material is an organic foam.

4. Device (18) according to claim 1 or 2, characterized in that said viscoelastic material is a metal foam.

5. Device (18) according to any one of the preceding claims, characterized in that each baffle (26) of the central layer (20) has a thickness comprised between 3mm and 7mm, and preferably 5 mm.

6. Device (18) according to any one of the preceding claims, characterized in that said central layer (20) has a thickness (E) comprised between 20mm and 30mm, and preferably 25 mm.

7. Device (18) according to any one of the preceding claims, characterized in that the cavity (28) of the central layer (20) has a depth (P) of 40 mm.

8. A method for manufacturing a device (18) according to any one of the preceding claims, characterized in that it comprises a step of manufacturing said cavities (28) in said central layer (20) by piercing a solid plate made of viscoelastic material.

9. Method according to the preceding claim, characterized in that the plate made of viscoelastic material has two surfaces, substantially parallel to each other, the piercing being oblique so that each cavity (28) has a height forming a part of a plane non-perpendicular to said surfaces of the plate.

10. The method according to claim 8 or 9, characterized in that the method further comprises the steps of:

-fixing a first skin (22) made of composite material to a first surface of a pierced plate of viscoelastic material,

-fixing a second skin (24) made of composite material to a second surface of the pierced plate of viscoelastic material, and

-making perforations in said first skin layer (22) made of composite material.

Technical Field

The present invention relates to the field of noise reduction for aircraft engines.

Background

Gas turbine engines, such as those that power aircraft, typically include structure for suppressing noise, particularly fan noise. These structures are generally made up of a plurality of porous structures formed by baffles defining cavities. These cells are typically arranged in a network, for example, a network resembling a plurality of "honeycomb" cells.

These structures are typically located within the engine's nacelle, downstream of the fan.

To the extent that thin, short nacelles are developed, the surfaces available for possible acoustic treatment become smaller and smaller. This means that the space for mounting the equipment, in particular the acoustic panel for attenuating the noise of the fan, is getting smaller. The bulk and integration of the equipment, particularly the installation of the acoustic panel in the secondary duct of the engine, therefore becomes a major problem.

Technically, in order to achieve effective sound insulation, the implementation must comply with the so-called "mass/spring/mass" principle: two masses (e.g., a blade and an insulator) are separated by a spring. The spring between the two masses attenuates the energy of sound and is therefore used as a noise damper.

The present invention is particularly intended to provide an acoustic treatment device which enables the thickness of the acoustic plate to be reduced while maintaining the same efficiency.

Disclosure of Invention

According to the invention, the invention is achieved by a noise reducing device for an aircraft turbine engine, having a structure in the form of a stack of layers, such that a first skin layer and a second skin layer made of composite material form a first outer layer and a second outer layer, the first outer layer and the second outer layer being substantially parallel to each other, the first outer layer and the second outer layer enclosing a central layer having a honeycomb structure comprising a partition extending transversely from the first outer layer to the second outer layer to form a cavity. The device is characterized in that the partitions of the honeycomb structure of the central layer are made of a viscoelastic material and form an acute angle of inclination with the first and second outer layers, for example between 10 and 80 degrees.

Thus, the thickness of the acoustic plate is reduced while maintaining the same efficiency. By reducing the thickness of the acoustic plate, the diameter of the housing is reduced. These diameter reductions enable an overall reduction in the diameter of the nacelle. All these diameter reductions make it possible to save the overall weight of the whole engine.

The device according to the invention may comprise one or more of the following features, which may be used alone or in combination with each other:

the baffles of the central layer are flat and have the same angle of inclination as the first and second outer layers, which angle of inclination is between 10 and 50 degrees, for example an acute angle between 10 and 30 degrees,

-the viscoelastic material is an organic foam,

-the viscoelastic material is a metal foam,

each baffle of the central layer has a thickness comprised between 3mm and 7mm, preferably 5mm,

the thickness of the central layer has a thickness comprised between 20mm and 30mm, preferably 25mm,

the cavities of the central layer have a depth of 40 mm.

The invention also relates to an outer fan module casing comprising a device as described above, intended to be arranged immediately upstream of the fan or immediately downstream of the fan, for example with respect to upstream and downstream with respect to the air flow through the turbine engine in which the fan is provided.

The invention also relates to a method for manufacturing a device according to any one of the preceding claims, characterized in that it comprises a step of making cavities in the central layer by piercing a solid plate made of viscoelastic material.

The method according to the invention may comprise one or more of the following features, which may be used alone or in combination with each other:

the plate made of viscoelastic material has two surfaces, which are substantially parallel to each other, the piercing being oblique so that each cavity has a height forming a part of a plane that is not perpendicular to the surfaces of the plate.

The method further comprises the steps of:

-fixing a first skin layer made of composite material to a first surface of a pierced plate of viscoelastic material,

-fixing a second skin layer made of composite material to a second surface of the pierced plate of viscoelastic material, and

-making perforations in a first skin made of composite material.

Drawings

Other features and advantages of the present invention will become apparent from the following detailed description, and for the purposes of understanding the detailed description, and by reference to the accompanying drawings, in which:

fig. 1 is a schematic axial cross-sectional view of an aircraft engine inlet, showing an acoustic treatment zone,

figure 2 is a perspective view of an example of a noise reducing device comprising a honeycomb core layer according to the prior art,

figure 3 is a schematic cross-sectional view of a honeycomb structure according to the prior art,

fig. 4 is a schematic cross-sectional view of a honeycomb structure according to the present invention.

Detailed Description

Fig. 1 schematically shows a cross-section of an inlet of an aircraft turbine engine generally comprising a gas generator 10 surrounded by an inner casing C1, a fan 12, a main duct 14 and a secondary duct 16, the main duct and the secondary duct being separated by an intermediate casing C2. Thus, the main duct 14 is defined by the inner case C1 and the intermediate case C2. The secondary duct 16 is delimited by an intermediate casing C2 and a fan module outer casing C3. The outer shell C3 is part of a component of the cabin of the aircraft. The housing C3 at least partially surrounds the fan 12.

As shown in fig. 1, the outer casing C3 includes two acoustic treatment zones Z1, Z2. The first zone of acoustic treatment Z1 is located upstream of the fan. A second acoustic treatment zone Z2 is located downstream of fan 12. In the present application, upstream and downstream are defined according to the flow direction of the gas in the turbine engine.

The acoustic treatment zones Z1, Z2 mainly comprise acoustic plates which form the noise reduction means 18 (see fig. 2). The device 18 generally has a structure in the form of a stack of layers 20, 22, 24.

The main criteria enabling an optimal acoustic treatment are the surface area and distance traveled by the acoustic wave to be attenuated in the cavity. For the "Ultra High By Pass Ratio" (UHBR) type of engines commonly used By the applicant, the range of target frequencies typically extends from 400Hz to 4 KHz.

As shown in fig. 2, the noise reducing device 18 according to the present invention includes a center layer 20 that forms a core. The core layer 20 forms a so-called honeycomb structure. The center layer 20 typically has a thickness E of about fifty millimeters. The central layer is generally made of a foam-type material (organic or metallic) or other viscoelastic material. As shown in fig. 2, the core layer 20 is sandwiched between a first skin layer 22 and a second skin layer 24, which are made of a carbon or glass composite material. The two skin layers 22, 24 form a first outer layer 22 and a second outer layer 24, respectively, of the device 18. The first outer layer 22 and the second outer layer 24 are generally parallel to each other and surround the central layer 20. The honeycomb structure of the center layer 20 is produced by planar baffles 26, all of which are generally parallel to each other and extend transversely from the first outer layer 22 to the second outer layer 24. The flat baffles 26 are positioned in contact with each other via their edges to form a uniform cavity 28 with the two skins 22, 24.

The device 18 is integrated into the cabin of an aircraft, a first outer layer (inner skin) 22 being in contact with the air flowing in the secondary duct 16, and a second outer layer (outer skin) 24 being in contact with the air circulating around the cabin.

In order to associate the desired acoustic function (reduction of noise) with the device 18 and to enable the air circulating in the secondary duct 16 to penetrate the central layer 20, perforations are made in the inner skin 22. These openings typically have a diameter D of 5 mm.

To achieve good acoustic performance, the perforation ratio of inner skin 22 is typically selected to be between 5% and 12%. Preferably, this ratio is about 10%. Thus, air is driven into the center layer 20 and the sound produced is reduced. In practice, the partition 26 forms a cavity 28 called a resonant cavity. Under the influence of the passage of air, the partition 26 of the cavity 28 vibrates and, if the dimensions are well calculated, enters resonance.

Frequency tuning (i.e., enabling optimization of the maximum dissipation to the frequency to be attenuated) is accomplished primarily by modulating the volume of the resonant cavity 28. Thus, the geometric characteristics of septum 26 are defined according to the target acoustic performance.

Typically, in the prior art, the cavity 28 has a depth P of about 40mm for the target application, as shown in fig. 3. In the present application, the depth P is defined as the length of the partition 26, i.e. the distance separating the two outer layers 22, 24 of the device 18 along an axis substantially parallel to said partition 26. In the prior art (see fig. 3), these planar baffles 26 extend vertically between the inner skin 22 and the outer skin 24. The depth P of the cavity 28 thus coincides with the height of the device 18, as shown in fig. 2 and 4.

The invention proposes to reduce the thickness of the acoustic treatment zones Z1, Z2. As shown in fig. 4, the separator 26 does not extend laterally between the first and second outer layers 22, 24. Separator 26 does not extend vertically between first outer layer 22 and second outer layer 24. In particular, the separator 26 forms an acute angle of inclination α with the outer layers 22, 24.

It is apparent that any acute angle α between the first face of the baffle 26 and the outer layers 22, 24 means that an obtuse angle β exists between the second face of the baffle 26 and the outer layers 22, 24, as can be seen in fig. 4.

Thus, the baffle 26 of the center layer 20 has the same angle of inclination α as both the first outer layer 22 and the second outer layer 24. The angle of inclination a is acute, for example between 10 and 80 degrees. Good results may be obtained by considering an acute angle, for example between 10 and 50 degrees. Angular values closer to 10 degrees than to 50 degrees are preferred.

Each baffle 26 of the central layer 20 has a thickness of between 3mm and 7mm, preferably 5 mm. As shown in fig. 4, the central layer 20 has a thickness E of between 20mm and 30mm, preferably 25 mm. However, since the spacer 26 no longer forms a right angle with the skins 22, 24, the thickness E of the center layer 20 no longer coincides with the depth P of the cavity 28. In practice, the depth P of the cavity 28, i.e. the length of the partition 26, is always approximately 40 mm. Thus, although the overall height of the device 18 has been reduced by a factor of about 1.6, the acoustic properties of the device 18 have not changed. Thus, an equivalent reduction in noise is maintained in the reduced thickness E. This also makes it possible to reduce the diameter of the outer casing C3 of the fan and, consequently, of the nacelle of the aircraft. The reduction in the size of the nacelle of an aircraft makes it possible to reduce the drag and the weight of said aircraft.

The honeycomb structure of the core layer 20 is made of a viscoelastic material. The viscoelastic material may be, for example, an organic foam or a metal foam.

The inclined cellular structure is obtained by a method applied to a solid panel made of viscoelastic material, such as organic foam or metal foam. The solid plate has two surfaces that are substantially parallel to each other. The height of the solid plate is approximately 25 mm. The solid sheet is intended to form a central layer 20.

Here, the method comprises the following five steps:

the cavities 28 of the central layer 20 are made by oblique piercing in a solid plate,

-fixing a first skin 22 made of composite material to the first surface of the pierced panel,

-fixing a second skin layer 22 made of composite material to a second surface of the pierced sheet of material, and

making perforations in the first skin layer 22 made of composite material.

The piercing of the solid plate is oblique such that each cavity 28 has a height that forms a portion of a plane that is not perpendicular to the surface of the plate.

The piercing step may be performed by piercing a tube, which may act as a guide to comply with the selected inclination angle α.

The depth P of penetration is made on the basis of a length equivalent to the performance of the intended application, in this case 40 mm.

Thus, with this method for piercing the foam, the person skilled in the art has a very large degree of freedom in selecting both the angle of inclination α and the length of the partition 26. In fact, once the acoustic model has been modeled, the plate can be pierced easily with satisfactory precision. The method according to the invention makes it possible to get rid of the difficulties associated with the assembly of an inclined honeycomb structure. All that remains is to add the outer layers 22, 24 and perforate the inner skin layer 22 and allow the device 18 to function. Thus, in addition to saving space due to the height of the panels, saving weight due to the reduction of the diameter of the outer shell, saving weight and drag of the aircraft due to the reduction of the outer surface of the nacelle, time is also saved during the manufacture of the device 18.