Method for producing a casing for an aircraft turbine engine

Abstract

Method for manufacturing a casing (3) for an aircraft turbine, the casing comprising: an annular casing portion (9) extending around an axis A and made of a composite material comprising woven fibers impregnated in resin, an annular layer (4) comprising a wear-resistant material arranged inside the casing portion and covering a first inner annular surface (9bb) of a middle section (9ab) of the casing portion, the method comprising a step of gluing the layer to the first surface, during which the casing is heated and compressed by a system located at least partially inside the casing, characterized in that before the casing is heated and compressed, a forming tool (10) is installed inside the casing and the forming tool consists of two rings (12, 14).

Description

Technical Field

[0001] The invention relates to the production of a casing, in particular a casing for a fan of an aircraft turbomachine. Background Art

[0002] The prior art includes in particular documents FR-A1-2 997 725, FR-A1-2 997 726, FR-A1-3 005 100 and FR-A1-3 060 7438.

[0003] Figure 1 A partial view of a fan of an aircraft turbine is provided.

[0004] Typically, a turbomachine comprises, from upstream to downstream (ie in the direction of gas flow), a fan, one or more compressors, a combustion chamber, one or more turbines, and an exhaust duct for the combustion gases leaving the one or more turbines.

[0005] The fan 1 comprises a blade wheel 2 surrounded by a fan housing 3, which is also called a retaining housing because it serves to retain the blades if they break loose or if debris penetrates inside the fan.

[0006] like Figure 2 As shown, the fan housing 3 generally comprises an annular shell portion with an axis of rotation A, which extends around the blades of the fan 2 of the turbomachine. The shell portion comprises an annular attachment flange 3', 3" at each of its axial ends. These flanges 3', 3" are used to attach the housing 3 to one of the annular walls of the nacelle of the turbomachine.

[0007] Figure 3 is a schematic cross section showing a fan housing 3 according to the prior art.

[0008] The fan casing 3 is connected in an upstream section to an air inlet duct 5 and in a downstream section to an intermediate casing shroud 6. The casing also supports an upstream acoustic panel 7 and a downstream acoustic panel 8. The fan casing 3 further comprises an annular layer 4 made of a wear-resistant material 4, which is arranged on the inner annular surface of the shell between the upstream panel 7 and the downstream panel 8.

[0009] In addition to the holding function, the fan housing 3 is also designed to:

[0010] - ensuring mechanical continuity (of stresses and moments) between the air inlet duct 5 and the shield 6 of the intermediate casing;

[0011] - enables the attachment of panels 7 , 8 and layer 4 ;

[0012] - enables the attachment of devices and supports known in the art;

[0013] - Comply with relevant fire prevention and leakage management regulations;

[0014] -Enables the flow of electric current to resist lightning strikes, etc.

[0015] It has been proposed to manufacture the shell of the fan casing from a composite material made of woven fibers immersed in a polymer resin, using a manufacturing process of the “RTM” type (standing for “Resin Transfer Moulding”).

[0016] In the RTM process, a mold comprising two half shells defines a molding cavity, the two half shells being arranged one on top of the other. Before the resin is injected, the fibers are woven in a three-dimensional manner to form a fiber preform, which is inserted into the mold cavity between the two half shells.

[0017] The polymerization of the resin is carried out by keeping the two half shells closed. Depending on the desired production rate, the polymerization is carried out at room temperature or by heating.

[0018] The use of such a process is particularly advantageous since it enables the manufacture of a component whose overall weight is less than that of an identical component manufactured in metallic material, while having a mechanical resistance that is at least equal, if not greater.

[0019] However, during demoulding, ie during the extraction of the manufactured part, deformations are observed with respect to the theoretical nominal geometry. Thus, by way of example, for a fan casing, defects can be observed with respect to the theoretically circular geometry when it is extracted from the mold, the part beginning to transform into an ellipse.

[0020] This type of deformation creates the following types of problems: assembly (matching gaps between components), manufacturing (non-uniform processing of components), other components that must adapt to the elliptical shape of the shell (such as wear-resistant layers), mechanical performance (non-uniform mechanical properties), aerodynamics (non-uniform aerodynamic flow paths), etc.

[0021] In particular, this defect can be explained by the fact that during component manufacturing, inside the mold, residual constraints are applied to the component (e.g. polymerization gradients, winding tensioning of components made of composite materials) and are released when the component is removed from the mold, resulting in deformations of the removed component.

[0022] In order to overcome this drawback, a known method is to use at least one mold comprising a molding cavity having a geometry that does not match the nominal geometry of the part to be manufactured, but takes into account the deformed geometry so that when the part is removed from the mold, the nominal geometry of the part is finally obtained.

[0023] Advantageously, this method will also counteract the ovalization of the rotor part when it is demoulded. However, during the manufacture of the fan casing, the ovalization of the fan casing observed does not only occur when it is taken out of the mold. In fact, the manufacture of the casing then implies various consecutive operations, such as machining (such as trimming and drilling) and gluing operations (such as the wear layer).

[0024] The machining operation results in the release of physical constraints that contribute to the deformation of the casing. The gluing operation is usually carried out in an oven. The gluing operation includes a step of heating and pressurizing the casing, followed by a step of cooling the casing. All these steps result in the emergence of constraints that contribute to the ovalization of the casing. Therefore, during the entire manufacturing process, various cases of casing ovalization may occur and tend to accumulate. Therefore, the prior art does not seem to be sufficient to combat the ovalization of the fan casing during its manufacture, since the emergence of this ovalization occurs not only when the casing is taken out of its molding cavity, but also during the machining and gluing steps.

[0025] The invention proposes a solution to limit the risks of ovalization of the fan casing during the gluing operation of the wear-resistant annular layer.

[0026] During this operation, the shell is placed in the oven as described above and part of a pressurizing system is mounted inside the shell to apply pressure radially from the inside towards the outside to the wear layer. This system further guarantees a constant process temperature during operation. This system is relatively bulky and prevents the use of solutions known in the prior art, such as that detailed in document FR-A1-3 060 7438, which include a plurality of annular parts (rims, flanges, drums, bladders, etc.) provided inside the shell and occupying the entire space of the shell.

[0027] The present invention proposes a simple, effective and cost-effective solution to this problem. Summary of the invention

[0028] The invention relates to a method for producing a casing for an aircraft turbomachine, the casing comprising:

[0029] an annular shell extending around the axis A and made of a composite material comprising woven fibers impregnated in a resin,

[0030] an annular layer comprising a wear-resistant material arranged inside the shell and covering a first inner annular surface of a middle section of the shell,

[0031] The method comprises a step of gluing the layer to the first surface, during which the shell is heated and compressed by a system located at least partially inside the shell,

[0032] It is characterized in that before the shell is heated and compressed, a forming tool is installed inside the shell, and the forming tool is composed of two rings, namely a first ring and a second ring, the first ring is arranged inside the shell and covers the second inner annular surface of the end section of the shell, the second ring is arranged inside the shell and covers the third inner annular surface of the other end section of the shell, and the middle section is arranged between the two end sections.

[0033] The shaping of the fan casing is thus ensured only by two rings, which are respectively mounted inside the two end sections of the composite shell of the casing. These shaping elements are therefore simple, since they have annular shape and do not occupy space inside the casing, and the center of the casing can therefore contain part of the system required for heating and / or pressurizing the casing during gluing of the wear layer.

[0034] The method according to the invention may include one or more of the following features considered individually or in combination:

[0035] - during compression, the housing is subjected to a pressure in the range of 1 to 10 bar, preferably in the range of 2 to 6 bar;

[0036] - during heating, the housing is subjected to a temperature in the range of 25° C. to 300° C., preferably in the range of 80° C. to 200° C.;

[0037] - the duration for which the shell is subjected to heating and compression is in the range of 60 minutes to 500 minutes, preferably in the range of 180 minutes to 300 minutes;

[0038] - the ring is divided into a plurality of segments and each ring comprises ring segments which are arranged circumferentially end-to-end and comprise circumferential ends which overlap one another;

[0039] - the circumferential end portion comprises a first through hole for the attachment assembly to pass through;

[0040] - the first holes of the ring are aligned with the second holes of the shell, the attachment assembly being screwed into these second holes or passing through these second holes;

[0041] - the rings each have a diameter in the range 1000 mm to 3000 mm, preferably in the range 1500 mm to 2500 mm, and / or an axial dimension in the range 50 mm to 300 mm, preferably in the range 100 mm to 200 mm, and / or a radial thickness in the range 10 mm to 100 mm, preferably in the range 20 mm to 50 mm;

[0042] - The method comprises: after heating and compressing, disassembling and removing the ring;

[0043] - The housing is arranged in an autoclave during heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings, in which:

[0045] [ Figure 1 ] Figure 1 is a partial cross-sectional view of a fan of an aircraft turbomachine mentioned above and showing the prior art;

[0046] [ Figure 2 ] Figure 2 is a perspective view of the fan housing mentioned above and showing the prior art;

[0047] [ Figure 3 ] Figure 3 is a schematic partial cross-sectional view of the fan housing mentioned above and showing the prior art;

[0048] [ Figure 4 ] Figure 4 is a highly schematic transverse cross-sectional view of a housing according to the invention to illustrate its risk of ovalization;

[0049] [ Figure 5 ] Figure 5 is a perspective view of the fan housing and two forming rings;

[0050] [ Figure 6 ] Figure 6 In the assembly position Figure 5 An axial cross-sectional perspective view of a fan housing and a forming ring;

[0051] [ Figure 7 ] Figure 7 yes Figure 5 An axial cross-sectional perspective view of a forming ring; and

[0052] [ Figure 8 ] Figure 8 yes Figure 5 A larger-scale perspective view of the circumferential ends of two segments of a shaped ring. DETAILED DESCRIPTION

[0053] In the following description, the present invention is applied to the fan casing 3. However, the present invention is not limited to this type of casing, and may be applied to other turbine casings.

[0054] The housing 3 to which the method according to the invention is applied has a generally annular shape around an axis A. This housing 3 comprises:

[0055] an annular shell 9 extending around the axis A and made of a composite material comprising woven fibers impregnated in resin, and

[0056] an annular layer 4 comprising a wear-resistant material arranged inside the shell 9 and covering a first inner annular surface 9ab ( Figure 3 ).

[0057] The annular layer 4 is intended to be fixed to the first internal surface 9bb of the shell 9 by gluing. This layer 4 may comprise a sandwich structure comprising an annular surface layer supporting a wear-resistant annular coating. As mentioned above, during this gluing step, the shell 3 is heated and compressed and may undergo ovalization ( Figure 4 ). In order to prevent this ovalization, the invention proposes a special tool 10 which is arranged inside the shell 3 and which forms the shell 3 during the gluing operation during which the shell 3 is subjected to a pressurized heat treatment.

[0058] Figures 5 to 8 An embodiment of this tool 10 is shown which comprises two rings 12, 14. Apart from the components for holding the rings 12, 14 and possibly fixing them to the housing 3, the tool 10 does not comprise any other parts and is therefore relatively simple.

[0059] In practice, during the gluing operation, the shell 3 is arranged in the autoclave 16 so that its axis A is oriented vertically. A pressurization system 18 is installed inside the shell 3, said system 18 being arranged in a manner similar to that of the embodiment of the present invention. Figure 6 The system 18 occupies a portion of the interior space of the housing 3 and the tool 10 is designed to take this constraint into account.

[0060] The first ring 12 (e.g., the upper ring) is arranged inside the shell 9 of the housing 3 and covers the second inner annular surface 9ba of the end section 9aa of the shell, and the second ring 14 (e.g., the lower ring) is arranged inside the shell and covers the third inner annular surface 9bc of the other end section 9ac of the shell. The middle section 9ab of the shell is arranged between the two end sections 9aa and 9ac ( Figure 3 and Figure 5 ), the inner surface 9bb of the middle section is covered by the wear-resistant layer 4.

[0061] The rings 12, 14 are not necessarily identical. Each ring is adapted and dimensioned according to the shape and size of the surface 9ba, 9bc to which it is applied. The upper ring 12 may, for example, have an outer surface 12a with a cylindrical shape, whereas the lower ring 14 may have an outer surface 14a with a truncated cone shape. Thus, on the one hand, the surface 12a and the surface 9ba are complementary, and on the other hand, the surface 14a and the surface 9bc are complementary.

[0062] As shown in the figures, the rings 12, 14 are preferably divided into a plurality of sectors in order to facilitate mounting the rings in the housing 3. In fact, if the rings consist of a single part, it would be difficult or even impossible to arrange the rings inside the housing, in particular if the housing has undergone ovalization. Each ring may comprise at least two sectors arranged circumferentially end to end.

[0063] Figure 8 The circumferential ends of the segments of the rings 12, 14 are shown overlapping each other and may comprise holes 20 for the passage of attachment members 22, for example of the screw-nut type. Thus, each ring segment is fixed to one or more adjacent segments at the level of its circumferential ends.

[0064] In order to ensure the correct positioning of the rings 12, 14 inside the housing 3, it is further conceivable to align the holes 20 of the rings with the holes 24 of the shell 9 ( Figure 5 ). The attachment assembly 22 passes through the hole 20 of the segment and can be screwed into the hole 24 of the shell, or passes through these holes and receives, for example, a nut. For example, the hole 24 of the shell is a hole that is intended to fix the shell to the above-mentioned and Figure 3 Acoustic insulation panels 7, 8 are shown in FIG.

[0065] In alternative solutions, the ring segments may be secured to each other by other types of components.

[0066] Preferably, the rings 12, 14 are oval-shaped and made of a material that is more rigid than the material of the shell. For example, the rings are made of metal.

[0067] In a particular example of embodiment of the invention, each ring 12, 14 has:

[0068] - a diameter in the range of 1000 mm to 3000 mm, preferably a diameter in the range of 1500 mm to 2500 mm,

[0069] - an axial dimension in the range of 50 mm to 300 mm, preferably in the range of 100 mm to 200 mm, and

[0070] - A radial thickness in the range of 10 mm to 100 mm, preferably in the range of 20 mm to 50 mm.

[0071] Rings 12, 14 are therefore arranged inside the shell 3 and on the surfaces 9ba, 9bc of the shell 9 to prevent ovalization of the shell during the gluing step of the wear layer 4 during which the shell is subjected to a double heat and pressure treatment.

[0072] During this operation, the shell 3 is subjected to a pressure ranging from 1 bar to 10 bar, preferably ranging from 2 bar to 6 bar. This compression can be achieved by placing the shell in a vacuum, for example by placing it between two annular elements, which are arranged inside the wear layer and outside the shell, respectively. The shell 3 can be subjected to a temperature ranging from 25° C. to 300° C., preferably between 80° C. and 200° C. This operation can be carried out during a cycle lasting between 60 minutes and 500 minutes, preferably between 180 minutes and 300 minutes.

[0073] At the end of this operation, the temperature and pressure to which the housing 3 is subjected are reduced. After the housing 3 has cooled completely, the wear layer is glued and fixed to the shell 9 and the rings 12, 14 can be disassembled and removed.

[0074] The invention is advantageous on different levels. On the technical side, it is no longer necessary to take into account the ovalization effect when defining the shell. On the industrial side, no specific machining operations of the wear layer or the shell are required. The manufacture and assembly of the shell are simplified, as is the three-dimensional inspection of the shell. The invention thus makes it possible to improve the mechanical and aerodynamic properties of the shell, as well as the method of manufacturing the shell, thus providing a time gain for the entire cycle.

Claims

1. A method for producing a casing (3) for an aircraft turbine, the casing comprising: - an annular shell (9) extending around the axis A and made of a composite material comprising woven fibers impregnated in a resin, - an annular layer (4) comprising a wear-resistant material arranged inside the shell and covering a first inner annular surface (9bb) of the middle section (9ab) of the shell, The method comprises a step of gluing the layer onto the first inner annular surface, during which the shell is heated and compressed by a system located at least partially inside the shell, The invention is characterized in that before the shell is heated and compressed, a forming tool (10) is installed inside the shell, and the forming tool is composed of two rings (12, 14), namely a first ring (12) and a second ring (14), the first ring is arranged inside the shell and covers the second inner annular surface (9ba) of the end section (9aa) of the shell, the second ring is arranged inside the shell and covers the third inner annular surface (9bc) of the other end section (9ac) of the shell, and the middle section is arranged between the two end sections.

2. The method according to claim 1, wherein: During the compression, the housing (3) is subjected to a pressure in the range of 1 bar to 10 bar.

3. The method according to claim 1 or 2, wherein: During the heating, the housing (3) is subjected to a temperature in the range of 25°C to 300°C.

4. The method according to claim 1 or 2, wherein: The duration for which the housing (3) is subjected to the heating and the compression is in the range of 60 minutes to 500 minutes.

5. The method according to claim 1 or 2, wherein: The rings (12, 14) are divided into a plurality of segments, and each ring comprises ring segments which are arranged circumferentially end-to-end and comprise circumferential ends which overlap one another.

6. The method according to claim 5, wherein: The circumferential end portion includes a first hole (20) for passage of an attachment assembly (22).

7. The method according to claim 6, wherein: The first holes (20) of the rings (12, 14) are aligned with the second holes (24) of the shell, and the attachment assembly (22) is screwed into or passed through these second holes.

8. The method according to claim 1 or 2, wherein: The rings (12, 14) each have: - diameters in the range of 1000 mm to 3000 mm, - an axial dimension in the range of 50 mm to 300 mm, and - Radial thickness in the range of 10mm to 100mm.

9. The method according to claim 1 or 2, wherein: The method includes disassembling and removing the rings (12, 14) after the heating and the compressing.

10. The method according to claim 1 or 2, wherein: During the heating process, the housing (3) is arranged in an autoclave (16).

11. The method according to claim 2, wherein: During the compression, the housing (3) is subjected to a pressure in the range of 2 to 6 bar.

12. The method according to claim 3, wherein: During the heating, the housing (3) is subjected to a temperature in the range of 80°C to 200°C.

13. The method according to claim 4, wherein: The duration for which the housing (3) is subjected to the heating and the compression is in the range of 180 minutes to 300 minutes.

14. The method according to claim 8, wherein: The rings (12, 14) each have a diameter in the range of 1500 mm to 2500 mm.

15. The method according to claim 8, wherein: The rings (12, 14) each have an axial dimension in the range of 100 mm to 200 mm.

16. The method according to claim 8, wherein: The rings (12, 14) each have a radial thickness in the range of 20 mm to 50 mm.

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