FR3104050A1 - MANUFACTURING PROCESS OF AN ANNULAR WALL OF AN AIRCRAFT TURBOMACHINE - Google Patents

Abstract

The invention relates in particular to a method of manufacturing an annular wall for an aircraft turbomachine, this wall having a conical or frustoconical shape around a longitudinal axis (A) and comprising an annular flange for fixing to at least one of its longitudinal ends, this wall being made of a metal alloy and comprising at least one aerodynamic annular surface intended to be swept by a flow of gas during operation of the turbomachine. According to the invention, the wall and at least part of its flange are made in one piece by plastic deformation of a sheet (30), this plastic deformation being produced by means of at least one roller (40) which is applied in force on the sheet (30) integral with a mandrel (50) rotating about said axis (A). Figure for abstract: Figure 6

Description

METHOD FOR MANUFACTURING AN ANNULAR WALL OF AN AIRCRAFT TURBOMACHINE

Technical field of the invention

The present invention relates to a method for manufacturing an annular wall of an aircraft turbine engine, this wall being for example an exhaust cone or shroud.

Technical background

A turbojet engine comprises an air inlet duct, upstream, through which air is drawn into the engine and a downstream nozzle through which the hot gases produced by the combustion of a fuel are ejected to provide at least some thrust. Between the inlet sleeve and the gas ejection nozzle, the air sucked in is compressed by compression means, heated and expanded in turbines which drive the compression means. Multi-flow turbojet engines also comprise at least one fan rotor moving a large mass of air, forming the secondary flow and supplying most of the thrust, the primary flow being the part of the aspirated air flow which is heated then expanded in the turbine, before being ejected through the primary flow nozzle.

A turbojet engine consists of rotors mounted on a fixed structure via bearings. The fixed structure has, upstream, a casing supporting the upstream bearings and forming the so-called intermediate casing. Downstream of the engine, the structure supporting the bearings forms the exhaust casing. The latter comprises a hub and annular shrouds interconnected by radial arms, the latter crossing the primary flow stream.

Downstream of the exhaust casing, the vein is delimited externally by the primary flow ejection nozzle and, internally, by a part of generally frustoconical shape which is designated by the expression exhaust cone. This part is generally attached to the exhaust casing via a flange located on the upstream edge of the exhaust cone.

Such cones are generally made in four quarter cones welded longitudinally because the material used (in particular a titanium-based alloy) has a very high elastic return and does not allow the rolling of a sheet in one or even two parts to form a cone. In addition, a disc is welded downstream of the cone on the small diameter and the mounting flange to the housing is welded upstream. This flange is manufactured by circular rolling or is spun and then rolled flash welded. Thus the numerous assembly operations, and in particular the numerous welds, make the manufacturing cycle of an exhaust cone long and expensive.

The invention thus aims to improve the method of manufacturing such an exhaust cone and to propose a cone that does not have these drawbacks.

The invention therefore proposes a method of manufacturing an annular wall for an aircraft turbomachine, this wall, for example of conical or frustoconical shape, extending around a longitudinal axis and comprising an annular flange for fixing to at least one of its longitudinal ends, this wall being made of metal alloy and comprising at least one aerodynamic annular surface intended to be swept by a flow of gas in operation of the turbomachine.

According to the invention, the wall and at least a part of its flange are made in one piece by plastic deformation of a sheet, this plastic deformation being carried out by means of at least one shaping member, such as a roller, which is applied by force to the sheet integral with a mandrel rotating around said axis.

The invention thus makes it possible to manufacture a wall of conical shape, in particular a cone or an exhaust ferrule, without welding and by integrating in particular the flange and the disc in a single piece.

The invention thus makes it possible to eliminate the laser cutting, the rolling, the longitudinal and circular welds as well as the control of the longitudinal welds of the four quarter cones, of the circular weld and of the exhaust of the prior art. The invention also makes it possible to avoid the manufacture and assembly of added elements such as the flange and the disc as well as the heat treatment of the assembly.

By merging parts (annular disc, flange) previously added and assembled by welding/assembly processes, the invention also allows a gain in mass linked to the disappearance of the means for fixing the parts together, the gain is very low because it only represents the weld allowances.

The invention also makes it possible to limit the springback effects linked to the shaping of the B21S sheet.

The invention thus makes it possible to reduce the cycles, manufacturing costs and to optimize the mass of an exhaust cone.

The method according to the invention may comprise one or more of the characteristics below, taken in isolation with each other or in combination with each other:

• the sheet is flat before plastic deformation;
• the sheet has a square or round shape before plastic deformation;
• the plastic deformation is carried out by flow spinning, the thickness of the sheet after deformation being less than the thickness of the sheet before deformation;
• the plastic deformation is carried out by spinning, the thickness of the sheet after deformation being substantially equal to the thickness of the sheet before deformation;
• the sheet has a thickness greater than 5mm, or even greater than 7mm, before plastic deformation;
• the sheet has a thickness less than or equal to 30mm, and preferably 20mm;
• the mandrel has a conical or frustoconical shape and includes an annular groove configured to receive material and to define said flange;
• after plastic deformation, part of the sheet is intended to completely fill the groove to define said flange;
• after plastic deformation, part of the sheet is intended to cover a strip of material inserted into said groove;
• after plastic deformation, the flange is machined;
• before or after plastic deformation, the sheet is machined to define at least part of the flange;
• the wall is an exhaust cone or ferrule; And
• the plastic deformation is carried out hot, by heating the sheet to a predetermined temperature, for example up to approximately 900°C.

The invention also relates to an exhaust cone or shroud manufactured by a method as described above, in which it comprises an annular wall, for example of conical or frustoconical shape, extending around a longitudinal axis and comprising an annular attachment flange at at least one of its longitudinal ends, this wall being made of metal alloy and comprising at least one aerodynamic annular surface intended to be swept by a flow of gas in operation of the turbomachine, the wall and at least one part of its flange being made in one piece from plastically deformed sheet metal, this wall being free of weld bead.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

Figure 1 is a schematic view in axial section of a turbofan engine;

Figure 2 is a schematic view in perspective and in axial section of an exhaust cone;

Figure 3 is a schematic view in axial section of an exhaust cone;

Figure 4 is a schematic view in axial section of part of an exhaust cone comprising a flange;

Figure 5 is a schematic view in axial section of a mandrel and a sheet during an exhaust cone manufacturing process;

Figure 6 is a schematic view similar to that of Figure 5 during a later step of the method;

Figure 7 is a schematic view in axial section of part of a mandrel and a sheet during a process for manufacturing an exhaust cone;

Figure 8 is a schematic view in axial section of part of an exhaust cone;

Figure 9 is a schematic view of part of a mandrel and a sheet during an exhaust cone manufacturing process;

Figure 10 is a schematic view in axial section of part of an exhaust cone; And

FIG. 11 is a schematic view of the steps of the method for manufacturing an exhaust cone according to an embodiment variant of the invention.

Detailed description of the invention

A turbomachine is shown in Figure 1. This is a double-flow, double-body turbomachine with successively from downstream to upstream, that is to say in the direction of the air path. in the engine, an air inlet 1 upstream, a fan 2 delivering air into an annular channel 3 of secondary flow F2 and towards compressors 4 of primary flow F1 in the center, a combustion chamber 5, and turbine stages 6. Downstream, rotors are supported by an exhaust casing 7. The primary flow F1 is ejected through a primary flow nozzle 8 downstream of the exhaust casing 7. The flow is annular and the stream of the primary flow F1 is delimited internally by an exhaust cone or ferrule 9. The exhaust cone 9 is a hollow part of substantially frustoconical shape, secured to the exhaust casing 7 and open on the downstream side.

Such an exhaust cone 9 is better visible in Figures 2 and 3. This exhaust cone 9 comprises a wall 10 of conical or frustoconical shape around a longitudinal axis A. It has in particular an angle of 20°, the large diameter being approximately 1200mm and the small diameter 90mm.

This wall 10 is made of a metal alloy, in particular based on titanium such as Ti 6242 which is more economical than B21S. This material thus has the advantage of being available in a thickness greater than that of B21S, which makes it possible to use all industrial forming processes such as flow spinning / spinning / forging / hot forming / machining and to avoid thus welds of the prior art. As a variant, the wall can be made of a nickel-based alloy, such as INCO.

The wall 10 comprises at least one aerodynamic annular surface 13 intended to be swept by the primary flow F1 of gas in operation of the turbomachine.

The wall 10 also comprises an annular flange 20 for attachment to the exhaust casing 7. The flange 20 is located at at least one of the longitudinal ends 11, 12, of the wall 10 and in particular at its downstream end 11.

As visible in Figure 4, the flange 20 is thicker than the rest of the wall 10. The flange 20 extends in particular towards the inside of the exhaust cone. The wall 10 and at least part of its flange 20 are made in one piece from plastically deformed sheet metal. The wall 10 is thus free of weld bead. Before the plastic deformation, the sheet is in particular flat and has for example a square or round shape.

An embodiment of the method for manufacturing the wall 10 according to the invention is illustrated in Figures 5 and 6.

The sheet 30 is in particular integral with a mandrel 50 rotating around the axis A, in particular by means of a screw 54. The mandrel 50 is mounted on a parallel lathe equipped with a mechanical arm 55 driving it in rotation.

The plastic deformation of the sheet 30 is then carried out by means of at least one roller 40 which is applied by force on the sheet 30. The roller or rollers 40 therefore press the sheet 30 against the mandrel 50. The disk which was reported in the prior art is thus an integral part of the wall and is located where the sheet is first in contact with the mandrel 50.

It is possible to use several rollers (in particular 3 or 4) to limit the number of passes of the roller and to be more precise in thickness. The shape of the rollers 40 is specific to best adapt to the part to be formed, such as for example a conical, cylindrical, spherical or disc shape.

The mandrel 50 has in particular a conical or frustoconical shape complementary to the shape of the wall. The sheet 30 is thus caught between the mandrel 50 and the roller(s) 40 until the wall is formed following a plastic deformation of the sheet 30.

The plastic deformation is carried out here by flow forming with possible addition of heat, the thickness of the sheet 30 after deformation being less than the thickness of the sheet 30 before deformation. Flow forming consists in effect of the plastic deformation of metals, creep, between a mandrel and one or more wheels or one or more rollers, between which the material “flows”, hence its name. It differs from spinning by the fact that it involves a reduction in thickness, whereas spinning is done at a constant thickness. This flow forming process can be carried out cold or hot, depending on the metals used and is here carried out in particular cold.

Heat input can improve the ductility of the material, and can be achieved by induction, flame, IR, etc. It is possible to heat the sheet alone or the sheet and mandrel assembly. After heating and plastic deformation, the wall can be subjected to a surface machining step in order to remove any oxide layer. This machining step can be carried out mechanically or chemically.

The sheet 30 has a thickness greater than 5mm, or even greater than 7mm, before plastic deformation, and which can reach 20mm or more. The sheet 30 has a thickness in particular about three times less after the flow forming process. Thus the thickness of the starting sheet is determined by ensuring that it is three times thicker than the thickness of the final product. The process could also provide for a reduction in thickness of four or even eight times compared to the initial thickness.

Mandrel 50 includes an annular groove 51 configured to receive material and to define the flange.

Thus according to this embodiment, after plastic deformation, a part 31 of the sheet 30 is intended to completely fill the groove 51 to define the flange. One or more rollers 40 will thus press on this part 31 so that it completely fills the groove 51 and defines the flange. Part 31 is located at a periphery of sheet 30.

According to a variant embodiment illustrated in FIG. 7, after plastic deformation, a part 32 of the sheet 30 is intended to cover a strip of material 33 added in the groove 51. The flow forming of the flange is here replaced by hot forming between the part 32 of the sheet 30 and the strip of material 33. The part 32 is located at a periphery of the sheet 30.

Thanks to this embodiment, it is possible to avoid starting from a sheet with a thickness three times greater than that required at the level of the flange.

In order to be able to unmold the cone with the flange "folded down" when hot, the mandrel 50 comprises two parts 52, 53. The part 52 comprising the groove 51 is thus removable to allow the exhaust cone to be unmolded once formed.

According to another embodiment visible in Figures 8 and 9, the sheet 30 can be machined beforehand, for example on a lathe in order to have a greater thickness at the level of the flange 20. Another embodiment can replace the machining by matrixing. Providing, before the flow forming process, a flange thickness e2 greater than the thickness e1 of the rest of the sheet thus makes it possible, after the flow forming, to directly have the desired thicknesses of the flange 20 and the rest of the wall. In particular, a thickness e2 of approximately 7.5 mm is provided before the flow forming on the surface corresponding to that of the flange 20 and a thickness e1 of approximately 4 mm on the rest of the sheet so as to obtain after flow forming respectively approximately 2 .5mm and 1.33mm.

In all the embodiments of the invention, and as illustrated in FIG. 10, the method can provide for a step subsequent to the plastic deformation, of machining the flange 20 in order to respect the thicknesses and shapes (in particular the shelving and corner breaking) requested. It is in particular the pieces 21 which are machined.

According to another embodiment and as visible in Figure 11, the plastic deformation can be carried out by spinning, the thickness of the sheet 30 after deformation being substantially equal to the thickness of the sheet 30 before deformation. The sheet 30 is then bent, in particular by means of a roller 40. After this plastic deformation, the sheet 30 is machined, in particular pieces 22 of the sheet, to define at least a part of the flange 20, and in particular whole bridle 20.

In the above description, the sheet is pressed against the mandrel starting from the small diameter to go towards the large diameter of the frustoconical shape. It is of course also possible to start from the large diameter to go to the small diameter.

Furthermore, the above description was made with reference to an exhaust cone 9 but the invention applies to any other type of annular wall for an aircraft turbine engine.

Claims (13)

Method of manufacturing an annular wall (10) for an aircraft turbine engine, this wall (10) extending around a longitudinal axis (A) and comprising an annular flange (20) for attachment to at least one of its longitudinal ends (11, 12), this wall (10) being made of metal alloy and comprising at least one aerodynamic annular surface (13) intended to be swept by a flow of gas (F1) in operation of the turbomachine, characterized in that the wall (10) and at least a part of its flange (20) are produced in a single piece by plastic deformation of a sheet (30), this plastic deformation being carried out by means of at least one shaping member, such as a roller (40), which is applied by force to the sheet (30) secured to a mandrel (50) rotating around said axis (A). Method according to the preceding claim, in which the sheet (30) is flat before plastic deformation. Method according to one of the preceding claims, in which the sheet (30) has a square or round shape before plastic deformation. Method according to one of the preceding claims, in which the plastic deformation is carried out by flow spinning, the thickness of the sheet (30) after deformation being less than the thickness of the sheet (30) before deformation. Method according to one of Claims 1 to 3, in which the plastic deformation is carried out by spinning, the thickness of the sheet (30) after deformation being substantially equal to the thickness of the sheet (30) before deformation. Method according to one of the preceding claims, in which the sheet (30) has a thickness greater than 5mm, or even greater than 7mm, before plastic deformation. Method according to one of the preceding claims, in which the mandrel (50) has a conical or frustoconical shape and comprises an annular groove (51) configured to receive material and to define said flange (20). Method according to Claim 7, in which, after plastic deformation, a part (31) of the sheet (30) is intended to completely fill the groove (51) to define the said flange (20). Process according to Claim 7, in which, after plastic deformation, a part (32) of the sheet (30) is intended to cover a strip of material (33) inserted in the said groove (51). Method according to one of Claims 7 to 9, in which, after plastic deformation, the flange (20) is machined. Method according to one of Claims 1 to 6, in which, before or after plastic deformation, the sheet (30) is machined to define at least a part of the flange (20). Method according to one of Claims 1 to 6, in which the wall (10) is an exhaust cone or shell. Exhaust cone or shroud (9) manufactured by a process according to one of the preceding claims, in which it or it comprises an annular wall (10) extending around a longitudinal axis (A) and comprising an annular flange (20) for attachment to at least one of its longitudinal ends (11, 12), this wall (10) being made of metal alloy and comprising at least one aerodynamic annular surface (13) intended to be swept by a flow of gas ( F1) in operation of the turbomachine, the wall (10) and at least a part of its flange (20) being made in one piece from a plastically deformed sheet (30), this wall (10) being free weld bead.