Cowl of an aeronautical propulsion assembly, aeronautical propulsion assembly comprising such a cowl, and method for manufacturing such a cowl

Abstract

The invention relates to a cowl of an aeronautical propulsion assembly (10) extending in an axial direction (X), a radial direction (R) and a circumferential direction (C), the cowl comprising an inner panel (12) having a plurality of cavities (12A) configured to attenuate noise, an outer panel (14) having an axial end (14A) connected to the inner panel (12), the outer panel (14) being arranged radially outside the inner panel (12), the inner panel (12) having a radial recess (13) receiving the axial end (14A) of the outer panel (14) such that the radially outer surface (14S) of the axial end (14A) of the outer panel (14) is tangential to the radially outer surface (12S) of a portion (12-1) of the inner panel (12) axially adjacent to the radial recess (13).

Description

Description Title of the invention: Aircraft propulsion assembly cowling, aircraft propulsion assembly comprising such a cowling, and method of manufacturing such a cowling. Technical Field

[0001] This presentation concerns an aircraft propulsion system cowling, an aircraft propulsion system comprising such a cowling, and a method for manufacturing such a cowling. For example, the cowling may be a tail cowling or outlet cowling of an aircraft propulsion system, either fixed (of the nozzle type) or movable (also called a transcowl cowling by those skilled in the art), but not necessarily so. Such a cowling may radially delimit the exterior of a gas stream outlet of the propulsion system, for example, a secondary or tertiary gas stream.

[0002] In this document, the term "aeronautical propulsion system" refers to all turbomachinery or gas turbine devices that produce motive power, are dedicated to the propulsion of an aircraft, and are equipped with a nacelle. Among these devices, a distinction is made between turbojets, which provide the thrust necessary for propulsion by reacting to the high-speed ejection of gases, and turboshaft engines, in which motive power is provided by the rotation of a drive shaft. For example, turboshaft engines are used as helicopter engines. Turboprop engines (turboshafts driving a propeller) are turboshaft engines used as aircraft engines. Previous technique

[0003] Common propulsion system cowlings typically consist of an inner panel and an outer panel joined to the inner panel via an axial end, with the outer panel positioned radially to the outside of the inner panel. To ensure the mechanical strength of the joint between the outer and outer panels and / or to provide a continuous external aerodynamic surface, common aeronautical propulsion system cowlings generally incorporate significant material thicknesses, added components, and / or substantial resin joints, which increase the overall mass, complicate the manufacturing process, and raise associated costs. Therefore, there is a need for solutions in this area. Description of the invention

[0004] One embodiment relates to an aircraft propulsion assembly cowling having an axial direction, a radial direction and a circumferential direction, comprising an internal panel having a plurality of cavities configured to attenuate noise, an external panel having an axial end connected to the internal panel, the external panel being arranged radially outside with respect to the internal panel, the internal panel having a radial recess receiving the axial end of the external panel such that the radially external surface of the axial end of the external panel is tangent to the radially external surface of a portion of the internal panel axially adjacent to the radial recess.

[0005] Generally, the axial direction corresponds to the direction of the axis of rotation of the gas generator of the aeronautical propulsion system, for example, when the cowling is mounted on an aeronautical propulsion system. A radial direction is a direction perpendicular to the axial direction. The azimuthal or circumferential direction corresponds to the direction describing a ring around the axial direction. The three directions—axial, radial, and azimuthal (or circumferential)—correspond respectively to the directions defined by elevation, radius, and angle in a cylindrical coordinate system. Furthermore, upstream and downstream are defined with respect to the normal direction of fluid flow (upstream to downstream) through the aeronautical propulsion system. Finally, unless otherwise specified, the adjectives inside / internal and outside / external are used with reference to the radial direction, so that the internal part (i.e.,radially internal) of an element is closer to the axis defining the axial direction than the external (i.e. radially external) part of the same element.

[0006] Hereafter, and unless otherwise indicated, "propulsive assembly" means "aeronautical propulsion assembly", by "hood" we mean "hood of aeronautical propulsion assembly", and by "recess" we mean "radial recess".

[0007] The portion (or first portion) of the inner panel axially adjacent to the recess is not covered by the outer panel and, together with the outer panel, forms the external aerodynamic surface of the hood. The second portion of the inner panel axially adjacent to the recess, axially opposite to the portion (or first portion) of the inner panel axially adjacent to the recess with respect to the recess, is covered by the outer panel and is positioned radially inward relative to the outer panel. This second portion may be at least partially radially distant from the outer panel. In other words, the external aerodynamic surface formed by the hood has a variable radius, for example monotonous increasing or decreasing, according to the axial direction in the direction oriented from upstream to downstream.

[0008] For example, the axial end of the external panel is a downstream axial end. For example, the portion (or first portion) of the internal panel axially adjacent to the recess extends downstream of the recess, forming a downstream portion of the internal panel. For example, the portion of the internal panel adjacent to the recess and extending upstream of the recess forms an upstream portion of the internal panel. The upstream portion (which may correspond to the second portion mentioned above) is arranged radially inward relative to the external panel.

[0009] For example, the inner panel and outer panel are assembled together only with rivets, and the assembly structure includes no other elements than the inner panel, the outer panel, the rivets and one or more optional filler joints such as resin.

[0010] The recess is formed on the outer surface of the inner panel. The recess creates a concavity extending radially from the outer surface of the inner panel towards the interior of the panel (i.e., into the material or material forming the inner panel). As a reminder, a recess is an indentation with a depth within the thickness of an object or wall. In other words, the inner panel has a radial thickness, and the concavity extends radially within the thickness of the inner panel, with the thickness of the inner panel extending in the radial direction. The inner panel may comprise, for example, one or more layers of material stacked in the radial direction, and the recess may extend radially within this layer or stack of layers. For example, the inner panel may comprise at least one layer of acoustic material (i.e.a layer of material configured to attenuate noise), and the recess may be formed within the acoustic material layer. The acoustic material layer may be all or part of the portion of the internal panel comprising the plurality of cavities configured to attenuate noise. Any other layers may conform to the surface of the acoustic material layer and define the surface of the recess.

[0011] The recess is configured so that when the axial end of the outer panel is disposed (or received or otherwise housed) within the radial recess, the outer surface of the outer panel is axially tangent to the outer surface of the portion of the inner panel adjacent to the radial recess (i.e., the first portion).

[0012] Such a configuration makes it possible to ensure an assembly structure comprising a limited number of components and assembly operations, thus presenting a controlled manufacturing cost, while providing the hood with a continuous and regular external aerodynamic surface and a limited mass.

[0013] In some embodiments, the external panel has an axial end portion comprising the axial end portion, the axial end portion having a constant radial thickness, a maximum radial depth of the radial recess being equal to the radial thickness of the axial end portion, plus or minus twenty percent (±20%), for example plus or minus nine percent (±9%).

[0014] For example, the axial end portion extends axially from the axial end over an axial length between 10 mm (ten millimeters) and 500 mm (five hundred millimeters), for example between 20 mm (twenty millimeters) and 60 mm (sixty millimeters).

[0015] The radial thickness and radial depth can be measured strictly along the radial direction or, assuming the angle formed by the axial end portion is small, for example less than or equal to 10° (ten degrees of angle), can be measured along a direction normal to their outer surface. In all cases, the radial thickness and radial depth are measured along the same direction.

[0016] This recess configuration ensures that the outer surface of the external panel, and more specifically the axial end portion of the external panel, is axially tangent to the outer surface of the portion of the internal panel adjacent to the radial recess (or first portion). This can help ensure an assembly structure with a limited number of components and assembly operations, thus keeping manufacturing costs down, while providing the hood with a continuous and regular external aerodynamic surface and a limited mass.

[0017] In some embodiments, a residual space extends axially within the radial recess between the axial end of the outer panel and the portion of the inner panel axially adjacent to the radial recess, the residual space being filled by a filler joint.

[0018] Such a filler seal is formed, for example, with resin, such as a chrome-free epoxy resin. Thanks to the hood's design and the recess, the residual gap is minimal compared to prior art hoods. For example, the axial extent of the residual gap is greater than or equal to 2 mm (two millimeters) and less than or equal to 7 mm (seven millimeters). Such a filler seal, Smaller than those of the prior art, this can contribute to better aerodynamic performance, particularly in the event of erosion and / or loss, which would have a reduced aerodynamic impact due to its small size. This helps ensure an assembly structure comprising a limited number of components and assembly operations, thus resulting in controlled manufacturing costs, while providing the hood with a continuous and regular external aerodynamic surface and a limited mass.

[0019] In some embodiments, the hood comprises a first electrically conductive coating on the external surface of the inner panel, a second electrically conductive coating on the external surface of the outer panel, the inner panel and the outer panel being fixed together by a plurality of electrically conductive rivets each in contact with the first electrically conductive coating and with the second electrically conductive coating, thereby ensuring electrical continuity between the inner panel and the outer panel.

[0020] In other words, the inner panel comprises the first coating, and the outer panel comprises the second coating. The first and second coatings can be of the same or different materials (thickness, etc.). Thanks to the electrically conductive nature of the first and second coatings, the outer surface of the cover is almost entirely covered with an electrically conductive material. Rivets ensure electrical continuity between the first and second coatings. This electrical continuity between the first and second coatings creates a connection between the two panels, allowing any accumulated electrical current (e.g., lightning) or charge (electrostatic) to dissipate. This electrical continuity, or junction, contributes to overall lightning protection and creates an effective lightning protection system across the entire outer surface of the cover.Such a coating configuration, which is made possible in particular by the hood configuration, and especially by the recess and associated assembly structure, helps to ensure an assembly structure comprising a limited number of components and assembly operations, thus presenting a controlled manufacturing cost, while providing the hood with a continuous and regular external aerodynamic surface, a limited mass and enhanced safety against lightning.

[0021] In some embodiments, the inner panel and the outer panel are fixed together by a plurality of rivets and in which, considered in the axial direction, each rivet is arranged within the radial recess.

[0022] For example, the first coating extends over the outer surface of the recess, while the second coating extends over the outer surface of the axial end portion of the outer panel. Rivets couple the outer and inner panels via the axial end portion of the outer panel and the recess of the inner panel. This configuration optimizes the integration of the lightning protection device's electrical continuity structure within the hood, contributing to an assembly structure with a limited number of components and assembly operations. This results in controlled manufacturing costs, while also providing the hood with a continuous and uniform external aerodynamic surface, reduced mass, and enhanced lightning protection.

[0023] In some embodiments, considered along the axial direction, the internal panel comprises a first central core of honeycomb material, a second central core of honeycomb material, distinct from the first central core and extending over all or part of the axial extent of the radial recess, and a third central core of honeycomb material, distinct from the first central core and the second central core, the second central core being arranged axially between the first central core and the third central core.

[0024] It is understood that the central cores are said to be central with respect to their position along the radial direction within the internal panel. For example, the internal panel has one or more layers radially external to the central cores, and one or more layers radially internal to the central cores. For example, the internal panel comprises, as central cores, only the first, second, and third central cores.

[0025] This three-core structure simplifies the manufacturing of the inner wall, particularly the recess. Overall, this helps ensure a good balance between the number of components and manufacturing operations, and the manufacturing cost, while providing the hood with a continuous and uniform external aerodynamic surface and a limited mass.

[0026] An embodiment relates to an aeronautical propulsion assembly comprising an aeronautical propulsion assembly cowl according to any of the embodiments described in this presentation, the axial end of the external panel being a downstream end, upstream and downstream being defined with respect to the direction of gas flow from upstream to downstream, the aeronautical propulsion assembly being configured so that the gases flow from upstream to downstream from an inlet to an outlet.

[0027] In such a configuration, the cowling can be a rear cowling or an exit cowling for the propulsion assembly. The radius of the external aerodynamic surface formed by the outer and inner panels of such a cowling can be monotonically decreasing along the axial direction from upstream to downstream.

[0028] An embodiment relates to a method of manufacturing an aircraft propulsion assembly cowling according to any one of the embodiments described in this exposition, wherein an internal panel having a plurality of noise-damping cavities and a radial recess is provided, and an external panel having an axial end, the axial end of the external panel is disposed within the radial recess of the internal panel so that the external panel is disposed radially outside the internal panel, and the internal panel and the external panel are fixed together so that the radially external surface of the axial end of the external panel is tangent to the radially external surface of a portion of the internal panel axially adjacent to the radial recess.

[0029] For example, for the manufacture of the external panel, a skin can be produced by draping material onto a tooling representative of the aerodynamic lines, for example using pre-impregnated fabrics (for example for manual draping) or strips of pre-impregnated material (for example for automated draping); oven-bake the skin, the baking temperature depending on the draped material, and the oven pressure can be on the order of 0.7 MPa (seven tenths of a megapascal); machine the skin to obtain the final dimensions, and carry out a non-destructive inspection of the skin which, at the end of such a process, forms the external panel.

[0030] For example, for the manufacture of the internal panel, a skin can be made by draping material onto a tooling representative of the aerodynamic lines, for example using pre-impregnated fabrics (for example for manual draping) or strips of pre-impregnated material (for example for automated draping); bake the skin in an oven, the baking temperature depending on the draped material, and the baking pressure can be on the order of 0.7 MPa (seven tenths of a megapascal); drill the skin to form acoustic cavities, for example by mechanical machining; perform a non-destructive testing of the skin; glue the skin, for example by depositing a film of glue where a layer of honeycomb material will be positioned; blow the glued skin to clear the holes in the acoustic cavities; glue a layer of honeycomb material onto the glue film (the radial indentation being machined into the honeycomb material layer beforehand or after gluing onto the glue film); optionally, depending on the complexity of the part, bake the honeycomb material layer at a pressure of approximately 0.07 MPa (seven hundredths of a. megapascal), which fixes the honeycomb material layer in position and shape on the skin; glue the honeycomb material layer (opposite the skin), for example by depositing a film of glue; create a second skin by draping it over the side glued in the previous step, for example using pre-impregnated fabrics (for example for manual draping) or strips of pre-impregnated material (for example for automated draping); bake the assembly obtained in the previous step, the baking temperature depending on the draped material, and the baking pressure can be on the order of 0.25 MPa (twenty-five hundredths of a megapascal); machine the part obtained in the previous step to obtain the final dimensions; carry out a non-destructive test of the part thus obtained which, at the end of such a process, forms an internal panel.

[0031] According to another example, for the manufacture of the internal panel, a skin can be created by draping material onto tooling representative of the aerodynamic lines, for example using pre-impregnated fabrics (for example for manual draping) or strips of pre-impregnated material (for example for automated draping); gluing the skin, for example by depositing a film of glue where a layer of honeycomb material will be positioned; gluing a layer of honeycomb material onto the glue film (the radial recess being machined in the layer of honeycomb material beforehand or after gluing onto the glue film); gluing the layer of honeycomb material (opposite the skin), for example by depositing a film of glue;to create a second skin by draping it over the glued surface from the previous step, for example using pre-impregnated fabrics (for example for manual draping) or strips of pre-impregnated material (for example for automated draping); to oven-bake the assembly obtained in the previous step, the baking temperature depending on the draped material, and the baking pressure being on the order of 0.25 MPa (twenty-five hundredths of a megapascal); to drill the part obtained in the previous step to form acoustic cavities; to machine the part obtained in the previous step to obtain the final dimensions; to carry out a non-destructive testing of the part thus obtained which, at the end of such a process, forms an internal panel.

[0032] In some embodiments, a residual space extending axially within the radial recess between the axial end of the outer panel and the portion of the inner panel axially adjacent to the radial recess is filled with resin. Once dry / polymerized, the resin forms a filler joint.

[0033] In some embodiments, the inner and outer panels are fixed using a plurality of electrically conductive rivets so that a The first electrically conductive coating on the external surface of the inner panel and a second electrically conductive coating on the external surface of the outer panel are in electrical contact, thereby ensuring electrical continuity between the inner panel and the outer panel. Brief description of the drawings

[0034] The purpose and advantages of this presentation will be better understood upon reading the detailed description below of various embodiments given as non-limiting examples. This description refers to the attached figure pages, on which:

[0035] [Fig. 1] Figure 1 represents an aeronautical propulsion system,

[0036] [Fig. 2] Figure 2 shows a detailed view of the propulsion assembly cowling, according to magnifying glass II of Figure 1, and

[0037] [Fig. 3] Figure 3 is a flowchart representing different stages of a manufacturing process for the outlet hood of Figure 2. Description of the implementation methods

[0038] Figure 1 shows an example of an aircraft propulsion system 100, in this example an aircraft turbojet engine. For example, the turbojet engine 100 can be of the twin-spool, twin-flow, or triple-flow type, with a shrouded fan (as shown in Figure 1) or an unshrouded fan (not shown). The aircraft propulsion system 100 is equipped with an aircraft propulsion system cowling 10. In this example, the propulsion system 100 is shown partially in cross-section to better illustrate the cowling 10.

[0039] The hood 10 has an axial direction X, a radial direction R and a circumferential direction C, which coincide in Figure 1 with the axial, radial and circumferential directions of the propulsion assembly 100. The gases within the propulsion assembly 100 flow from upstream AM to downstream AV from an inlet E to an outlet S.

[0040] In this example, the cowling 10 is a rear cowling or axially movable outlet cowling, also called a movable thrust reverser cowling or "transcowl" in English. In Figure 1, the cowling 10 is shown in the deployed position, so that the grids 50 of the thrust reverser 60 of the propulsion unit 100 are visible. According to an alternative (not shown), the cowling can be axially fixed and form a nozzle. In this example, the cowling 10 radially delimits the outside of a portion of the duct secondary V2 of the gases within the propulsion assembly 100, particularly when the cowling 10 is in the retracted position (not shown).

[0041] The hood 10 is described in more detail with reference to Figure 2. The hood 10 comprises an inner panel 12 having a plurality of cavities 12A configured to attenuate noise, an outer panel 14 having an axial end 14A connected to the inner panel 12, the outer panel 14 being arranged radially outside with respect to the inner panel 12 (in Figure 2 the inner side of the hood being indicated by INT and the outer side of the hood being indicated by EXT), the inner panel 12 having a radial recess 13 receiving the axial end 14A of the outer panel 14 such that the radially external surface 14S of the axial end 14A of the outer panel 14 is tangent (see dashed line T in Figure 2) to the radially external surface 12S of a portion (or first portion) 12-1 of the inner panel 12 axially adjacent to the radial recess 13.As can be seen in Figure 2, the radial recess 13 is provided on the external surface 12S of the internal panel 12 and forms a concavity extending radially from the external surface 12S of the internal panel towards the interior INT of the hood 10 or the panel 12.

[0042] The portion 12-1 of the inner panel axially adjacent to the recess 13 is not covered by the outer panel 14, and together with the outer panel 14 forms the external aerodynamic surface SEA of the hood 10. The second portion 12-2 of the inner panel 12 axially adjacent to the recess 13 and axially opposite to portion 12-1 with respect to the recess 13, is covered by the outer panel 14, and is arranged radially inward with respect to the outer panel 14. The second portion 12-2 may be at least partially radially distant from the outer panel 14.

[0043] In this example, the axial end 14A of the external panel 14 is a downstream end, with upstream AM and downstream AV defined with respect to the direction of gas flow from upstream AM to downstream AV. The aeronautical propulsion assembly 100 is configured so that gases flow from upstream AM to downstream AV from an inlet E to an outlet S. According to an alternative (not shown), the axial end could be an upstream end.

[0044] In this example, the external panel 14 has an axial end portion 14A-1 comprising the axial end 14A, the axial end portion 14A-1 having a constant radial thickness ER, a maximum radial depth PRM of the radial recess 13 being equal to the radial thickness ER of the axial end portion 14A-1, plus or minus twenty percent, for example plus or minus nine percent.

[0045] In this example, a residual space 16 extending axially within the radial recess 13 between the axial end 14A of the outer panel 14 and the portion 12-1 of the inner panel 12 axially adjacent to the radial recess 13, the residual space 16 being filled by a filler joint 18.

[0046] In this example, the hood 10 includes a first electrically conductive coating 20 on the external surface 12S of the internal panel 12, a second electrically conductive coating 22 on the external surface 14S of the external panel 14, the internal panel 12 and the external panel 14 being fixed together by a plurality of electrically conductive rivets 24 each in contact with the first electrically conductive coating 20 and with the second electrically conductive coating 22, thereby ensuring electrical continuity between the internal panel 12 and the external panel 14, at least between the external surface 12S of the first portion 12-1 of the internal panel 12 and the external surface 14S of the external panel 14.For example, the first electrically conductive coating 20 is made of fabric with a bronze weave, the second electrically conductive coating 22 is also made of fabric with a bronze weave, and the rivets 24 are made of stainless steel. The assembly comprising the first electrically conductive coating 20, the second electrically conductive coating 22, and the rivets 24 forms a lightning arrester 30 for the cover 10.

[0047] In this example, the inner panel 12 and the outer panel 14 are fixed together by a plurality of rivets 24 and in which, considered along the axial direction X, each rivet 24 is disposed within the radial recess 13

[0048] In this example, the first cladding 20 extends over the outer surface of the recess 13, while the second cladding 22 extends over the outer surface of the axial end portion 14A-1 of the outer panel 14. In this example, the first cladding 20 does not extend over the outer surface of the second portion 12-2 of the inner wall 12. The rivets 24 couple the outer panel 14 and the inner panel 12 via the axial end portion 14A-1 of the outer panel 14 and the recess 13 of the inner panel 13.

[0049] In this example, considered along the axial direction X, the internal panel comprises a first central core 12B1 made of honeycomb material, a second central core 12B2 made of honeycomb material, distinct from the first central core 12B1 and extending over all or part of the axial extent of the radial recess 13, and a third central core 12B3 made of honeycomb material, distinct from the first central core 12B1 and the second central core 12B2. 12B2 being arranged axially between the first central web 12B1 and the third central web 12B3. The hatched areas 11 A and 11 B in Figure 2 represent the connection areas along the axial direction between the first and second central webs 12B1 and 12B2 on the one hand, and between the second and third central webs 12B2 and 12B3 on the other hand.

[0050] In this example, the central cores 12B1, 12B2, and 13B3 of the inner panel 12 are radially sandwiched between an inner skin 12C and an outer skin 12D, with through holes provided in the inner skin 12C to form the acoustic cavities 12A. The first electrically conductive coating 20 is disposed on the outside of the outer skin 12D. In this example, the outer panel 14 comprises a single skin 14B on the outside of which the second electrically conductive coating 22 is disposed.

[0051] Generally, the radial recess 13 extends radially through the thickness of the inner panel 12 (i.e., through the material forming the inner panel 12). In this example, the recess 13 can be formed in the core of the inner panel 12, for example, in the core 12B2 and the core 12B3. The core forms an example of an acoustic material layer. In this example, the outer skin 12D and the first optional electrically conductive coating 20 conform to the shape of the core and the concavity forming the radial recess 13.

[0052] A manufacturing process PR of the hood 10 is described with reference to Figure 3. In a first step E1, an internal panel 12 is provided having a plurality of cavities 12A configured to attenuate noise and a radial recess 13, as well as an external panel 14 having an axial end 14A. In a second step E2, the axial end 14A of the external panel 14 is placed within the radial recess 13 of the internal panel 12 so that the external panel 14 is positioned radially outside the internal panel 12. In a third step E3, the internal panel 12 and the external panel 14 are fixed together so that the radially external surface 14S of the axial end 14A of the external panel 14 is tangent to the radially external surface 12S of a portion 12-1 of the internal panel 12 axially adjacent to the radial recess 13.For example, during the third step E3, the inner panel 12 and the outer panel 14 are fixed using a plurality of electrically conductive rivets 24 so that a first electrically conductive coating 20 is on the outer surface 12S of the inner panel 12 and a second electrically conductive coating 22 is on the outer surface 14S of the panel. external 14 are in electrical contact, thereby ensuring electrical continuity between the internal panel 12 and the external panel 14.

[0053] The PR process may include a fourth step E4 in which a residual space 16 extending axially within the radial recess 13 between the axial end 14A of the outer panel 14 and the portion 12-1 of the inner panel 12 axially adjacent to the radial recess 13 is filled with resin. A resin joint 16 is thus formed.

[0054] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0055] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. Aircraft propulsion assembly cowling (10) having an axial direction (X), a radial direction (R) and a circumferential direction (C), comprising an inner panel (12) having a plurality of cavities (12A) configured to attenuate noise, an outer panel (14) having an axial end (14A) connected to the inner panel (12), the outer panel (14) being disposed radially outside with respect to the inner panel (12), the inner panel (12) having a radial recess (13) receiving the axial end (14A) of the outer panel (14) such that the radially outer surface (14S) of the axial end (14A) of the outer panel (14) is tangent to the radially outer surface (12S) of a portion (12-1) of the inner panel (12) axially adjacent to the radial recess (13).

2. Aircraft propulsion assembly cowling (10) according to claim 1, wherein the external panel (14) has an axial end portion (14A-1) comprising the axial end (14A), the axial end portion (14A-1) having a constant radial thickness (ER), a maximum radial depth (PRM) of the radial recess (13) being equal to the radial thickness (ER) of the axial end portion (14A-1), plus or minus twenty percent, for example plus or minus nine percent.

3. Aircraft propulsion assembly cowling (10) according to claim 1 or 2, having a residual space (16) extending axially within the radial recess (13) between the axial end (14A) of the outer panel (14) and the portion (12-1) of the inner panel (12) axially adjacent to the radial recess (13), the residual space (16) being filled by a filler joint (18).

4. Aircraft propulsion assembly cowling (10) according to any one of claims 1 to 3, comprising a first electrically conductive coating (20) on the external surface (12S) of the inner panel (12), a second electrically conductive coating (24) on the external surface (14S) of the outer panel (14), the inner panel (12) and the outer panel (14) being fixed together by a plurality of electrically conductive rivets (24) each in contact with the first electrically conductive coating (20) and with the second electrically conductive coating (22), thereby ensuring electrical continuity between the inner panel (12) and the outer panel (14).

5. Aircraft propulsion assembly cowling (10) according to any one of claims 1 to 4, wherein the inner panel (12) and the outer panel (14) are fixed together by a plurality of rivets (24) and in which, considered along the axial direction (X), each rivet (24) is arranged within the radial recess (13).

6. Aircraft propulsion assembly cowling (10) according to any one of claims 1 to 5, wherein, viewed along the axial direction (X), the internal panel (12) comprises a first central core (12B1) of honeycomb material, a second central core (12B2) of honeycomb material, distinct from the first central core (12B1) and extending mostly or part of the axial extent of the radial recess (13), and a third central core (12B3) of honeycomb material, distinct from the first central core (12B1) and the second central core (12B2), the second central core (12B2) being arranged axially between the first central core (12B1) and the third central core (12B3).

7. Aircraft propulsion assembly (100) comprising an aircraft propulsion assembly cowl (10) according to any one of claims 1 to 6, the axial end (14A) of the external panel (14) being a downstream end, upstream (AM) and downstream (AV) being defined with respect to the direction of gas flow from upstream (AM) to downstream (AV), the aircraft propulsion assembly (100) being configured so that gases flow from upstream (AM) to downstream (AV) from an inlet (E) to an outlet (S).

8. A method of manufacturing (PR) an aircraft propulsion assembly cowling (10) according to any one of claims 1 to 6, wherein (E1) an inner panel 12 having a plurality of noise-dampening cavities (12A) and a radial recess (13) and an outer panel (14) having an axial end (14A) are provided, (E2) the axial end (14A) of the outer panel (14) is disposed within the radial recess (13) of the inner panel (12) such that the outer panel (12) is disposed radially outside the inner panel (14), and (E3) the inner panel (12) and the outer panel (14) are fixed together such that the radially external surface (14S) of the axial end (14A) of the outer panel (14) is tangent to the radially external surface (12S) of a portion (12-1) of the internal panel (12) axially adjacent to the radial recess (13).

9. A manufacturing method (PR) for an aircraft propulsion assembly cowling (10) according to claim 8, wherein a residual space (16) extending axially within the radial recess (13) between the axial end (14A) of the outer panel (14) and the portion (12-1) of the inner panel (12) axially adjacent to the radial recess (13) is filled (E4) with resin.

10. A method of manufacturing (PR) an aircraft propulsion assembly cowling (10) according to claim 8 or 9, wherein the inner panel (12) and the outer panel (14) are fixed (E3) using a plurality of electrically conductive rivets (24) such that a first electrically conductive coating (20) on the outer surface (12S) of the inner panel (12) and a second electrically conductive coating (22) on the outer surface (14S) of the outer panel (14) are in electrical contact, thereby ensuring electrical continuity between the inner panel (12) and the outer panel (14).

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