Background of the invention

The present invention relates to the general field of the manufacture of parts made of polymer material, in particular thermosetting material, of metal parts, of metal alloy or of ceramic by additive manufacturing and it relates more particularly, but not exclusively, to the manufacture of abradable coatings having acoustic functions, in particular for the blower housing.

Controlling noise pollution caused by airplanes in the vicinity of airports has become a public health issue. More and more stringent standards and regulations are imposed on aircraft manufacturers and airport managers. As a result, building a silent aircraft has become a strong selling point over the years. Currently, the noise generated by aircraft engines is attenuated by localized reaction acoustic coatings which make it possible to reduce the sound intensity of the engine over one or two octaves on the principle of Helmholtz resonators, these coatings being conventionally presented under the form of composite panels composed of a rigid plate associated with a honeycomb core covered with a perforated skin and arranged at the level of the nacelle or the upstream and downstream propagation conduits. However, in new generation engines (for example in turbofans), the areas available for acoustic coatings are reduced considerably as in UHBR (Ultra-High-Bypass-Ratio) technology. In addition, these areas of composite material housings are liable to exhibit defects in shape which should be remedied by an additional machining operation before the installation of the coating.

It is therefore important to propose new processes and / or new materials (in particular porous materials) making it possible to eliminate or significantly reduce the level of noise produced by aircraft engines, especially during take-off phases and landing gear and over a wider frequency range than at present including low frequencies while maintaining engine performance. This is the reason why we are now looking for new noise reduction technologies to reduce this nuisance as well as new acoustic treatment surfaces and this with a minimal impact on other engine functions such as specific fuel consumption which constitutes a significant commercial advantage.

However, within aircraft engines, the noise produced by the fan is one of the main contributors to noise pollution favored by the increase in the dilution rate sought by these new generations of aircraft.

Moreover, it is now common and advantageous to use additive manufacturing processes instead of traditional foundry, forging or mass machining processes to easily, quickly and inexpensively produce complex three-dimensional parts. The aeronautical field lends itself particularly well to the use of these methods. Among these, there may be mentioned for example the method of direct energy deposition by wire (Wire Beam Deposition).

Purpose and summary of the invention

The present invention aims to provide a method of shaping a new abradable material, further making it possible to significantly reduce the noise generated by aircraft turbojets and in particular that generated by the fan-OGV assembly. An object of the invention is also to make up for the shape defects resulting from the composite nature of the substrate on which this abradable material is intended to be deposited.

To this end, there is provided an in situ deposition method by manufacturing a coating on a turbomachine casing consisting of depositing on an internal surface of a turbomachine casing a filament of an abradable material according to a predefined deposition path in order to to create a three-dimensional scaffolding of filaments forming between them an ordered network of channels, the method being characterized by the following steps:

positioning a system for depositing filamentary material at the level of a longitudinal axis of said casing at a position and a determined distance with respect to said internal surface of said casing,

depositing a first layer of said coating over 360 ° of the circumference of said housing by a relative circumferential displacement between said housing and said filamentary material deposition system, rotating said filamentary material deposition system by a first determined angle and positioning said system for depositing filamentary material at the level of said longitudinal axis of said casing at a position and a determined distance with respect to said first layer of said coating,

depositing on a sector of said casing by a relative axial movement between said casing and said filamentary material deposition system, a second layer of said coating on said first layer of said coating,

perform a relative circumferential displacement between said casing and said filamentary material deposition system by a determined angular deviation corresponding to the first sector already covered during the deposition of said second coating layer,

and repeating the step of depositing on said housing sector and the step of relative circumferential displacement according to said angular deviation determined for the following sectors until covering the 360 ​​° of the circumference of said housing, and

after having performed a rotation of said filamentary material deposition system by a second determined angle, repeat all of the previous steps, with the exception of the first, for the following layers until a desired coating thickness is obtained.

Thus, a porous microstructure with regular and ordered porosity is obtained which ensures a significant absorption of the acoustic waves by visco-thermal dissipation within the channels.

Preferably, prior to depositing said first layer of said coating, a layer of a backlash take-up material is deposited on said turbomachine casing to obtain a deposit surface of known geometry.

Advantageously, the deposition of filamentary material is carried out by a plurality of ejection nozzles whose vertical positioning of each of said ejection nozzles is independently adjustable.

According to the embodiment envisaged, said step of rotating said filament deposition system is performed twice by successive rotation of 90 °, the first determined angle being equal to 90 ° or else said step of rotating said filament deposition system is performed as much when there are determined directions of orientation of the different filaments. More particularly, said step of rotating said filament deposition system is performed six times by successive rotation of 30 °, the first determined angle being equal to 30 °.

Preferably, additional layers of said coating are added locally to take account of a non-axisymmetric geometry of said turbomachine casing.

Advantageously, the deposition of filamentary material is carried out by a plurality of ejection nozzles whose vertical positioning of each of said ejection nozzles is independently adjustable.

Preferably, said turbomachine casing is a fan casing made of woven composite material.

The invention also relates to a system for depositing filamentary material for the implementation of the aforementioned method and to an abradable coating of a turbomachine wall obtained from the aforementioned method.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the detailed description given below, with reference to the following figures which are not in any way limiting and in which:

FIG. 1 schematically illustrates an architecture of an aircraft turbomachine in which the in situ coating manufacturing process according to the invention is implemented,

FIG. 2 is a schematic view of a first example of a device for implementing the method of the invention,

FIG. 3 is a schematic view of a second example of a device for implementing the method of the invention,

FIG. 4 illustrates a system for depositing filamentary material used in the device of FIG. 2,

FIG. 5 is an exploded view of a three-dimensional scaffolding of cylindrical filaments obtained by the system of FIG. 4,

Figures 6A to 6D are examples of ordered networks of channels obtained by the system of Figure 4, and

FIG. 7 shows the different steps of the in situ coating manufacturing process according to the invention.

Detailed description of the invention

Figure 1 very schematically shows an aircraft turbomachine architecture, in this case a bypass turbojet, at which is implemented the manufacturing process of a coating of abradable material with acoustic properties of the 'invention.

Conventionally, such a bypass turbojet 10 has a longitudinal axis 12 and consists of a gas turbine engine 14 and an annular nacelle 16 centered on the axis 12 and disposed concentrically around the engine.

an annular secondary cover 36 coaxially surrounding the primary cover in order to define with the latter an annular flow channel of the secondary flow F2 coaxial with the primary flow channel and in which are arranged rectifier vanes 38 (in the example of illustrated embodiment, the nacelle 16 of the turbojet and the secondary cowl 36 of the nozzle are one and the same part). The primary and secondary cowls integrate in particular the intermediate turbine housings 28A and 30A

surrounding the movable blades of the turbine rotors and the fan housing 20A surrounding the movable vanes of the fan rotor.

According to the invention, it is proposed to affix, by additive manufacturing, on the internal walls of housings facing the rotor blades, a coating endowed with abradable and acoustic functions and which is in the form of a scaffolding. three-dimensional filaments forming between them an ordered network of channels. Depending on the configuration envisaged, interconnections between the channels may exist in a regular manner during the superposition of the different layers of the coating intended to generate these different channels. This wall is preferably a wall of a turbomachine, such as an airplane turbojet, mounted on the immediate periphery of the moving blades, and more particularly the internal wall of the fan casing 20A made of 3D woven composite disposed at the periphery of the fan blades. However, a deposit on the turbine casing (s) 28A, 30A can also be considered, with the proviso of course that the abradable material of metallic or ceramic type then exhibits properties adapted to the environment at very high temperature of the turbine.

The advantage of the abradable functionality is to make the rotor-casing assembly compatible with the deformations to which the rotating blades undergo when the latter are subjected to the sum of the aerodynamic and centrifugal forces.

By abradable material is meant the ability of the material to dislocate (erode) in operation in contact with a facing part (low shear resistance) and its resistance to wear following the impact of particles or foreign bodies that it is required to ingest during operation. Such a material must also keep or even promote good aerodynamic properties, have sufficient resistance to oxidation and corrosion and a thermal expansion coefficient of the same order as the layer or the substrate on which it is deposited, in the latter. case the woven composite material forming the housing walls.

FIG. 2 illustrates a first example of a device allowing the production of such a coating with acoustic properties by the continuous deposition of filaments of abradable material at the level of an internal wall of a turbomachine such as a fan casing 20A.

This device comprises a casing support 40 intended to position the fan casing 20A so that its longitudinal axis 42 is parallel to the ground, thus promoting the deposition of the filamentary material by gravity (vertical deposition of material downwards) on any point on the inside wall of the housing. This support may for example consist of two synchronized drive rollers 40A, 40B to simultaneously drive the casing in rotation about its longitudinal axis, thus ensuring a degree of freedom in rotation along this longitudinal axis.

The device also comprises a mechanical assembly 44 provided with several articulations and equipped at a free end 44A with a filamentary material deposition system 46 comprising at least one ejection nozzle 46A through which the abradable material is ejected with precision. Typically, such a mechanical assembly is constituted at least by a 3-axis machine or, as illustrated, by a robot having precision “digital axes” (positioning of the order of 5 microns) making it possible via appropriate known software to control the machine. 'printing according to a deposit path defined by the user. Thanks to this equipment, it is therefore possible to guarantee precise deposition of filaments in a determined three-dimensional space, by controlling printing parameters such as the flow speed of the material,

More precisely, this mechanical assembly 44 has a degree of freedom in translation along the longitudinal axis of the casing so as to reach any point on its internal wall to deposit the abradable material. It also has a degree of freedom in vertical translation, so that the distance from the deposition surface can be adjusted in real time. In addition, this degree of freedom makes it possible to adapt the deposition system to the variations in diameter which may be observed between different architectures of turbojets. To do this, a distance sensor 48 integral with or disposed near the ejection nozzle 46A is provided in order to measure the distances between this ejection nozzle and the casing or the abradable material. This sensor can further be used, through the use of

Optionally and depending on the nature of the material used, the device can also include a solidification module 50 to promote and accelerate the solidification process of the deposited abradable material. This module can be formed by a device for emitting light waves (UV, infrared or other), by one or more fans blowing in the direction of the abradable material or by one or more heating resistors or even by any other similar heating system. , or even possibly by a cooling device depending on the nature of the material used, these different devices being able to operate alone or in combination with one another.

The control and command of all of the components of the device are provided by a management unit 51, typically a microcontroller or a microcomputer, which manages the deposition of abradable material in conjunction with the rotation of the fan casing, the dimensional tolerancing final according to the data obtained from the distance sensor 48 and when it is present the control of solidification via the module 50.

FIG. 3 illustrates an alternative embodiment of the device (the unchanged elements bear the same references) in which the single ejection nozzle is replaced by a multi-nozzle system 52 making it possible to accelerate the deposition of the abradable material by a greater factor. the number of nozzles and comprising several ejection nozzles 54A - 54E aligned on the axis of a rigid part 56 which supports them and whose vertical positioning of each of these nozzles, measurable by an associated distance sensor 48A - 48E, is independently adjustable in order to guarantee an optimal distance between each nozzle and the surface on which the filamentary material is deposited (taking into account the cylindrical shape of the fan housing). Note that the single sensor 48 could, using a post-processing of the data collected, also deduce this distance between each of the nozzles and the surface of the casing. Each nozzle is advantageously equipped with a circuit making it possible to regulate the pressure and the temperature at the nozzle outlet so as to control the geometries as well as the times and cycles of deposition.

The nozzles are preferably removable and separable from the support piece 56 so that the number of nozzles and their geometry (size and section) can be configured as a function of the coating to be used. They can also be adjustable in height as a function of the angle defined by the filamentary material deposition system with respect to the casing. Additionally, each nozzle can be supplied with different material sources, depending on the type of coating desired.

The support part 56 may have a pivot connection 58 relative to the mechanical assembly 44 which supports it. The axis of this pivot is oriented vertically, that is to say parallel to that of the nozzles. Thus, by applying a rotation to the support part, it is possible to control the spacings between the material deposition points, regardless of the direction of relative movement of the nozzles (axial or azimuthal) with respect to the fan housing 20A.

The filamentary material deposition system 46 is illustrated diagrammatically in FIG. 4. The object of this filamentary deposition system is to deposit, in conjunction with the aforementioned circuit for controlling pressure and temperature internal to the system, a material which can be abraded by extrusion via the ejection nozzle 46A of shape and dimension calibrated firstly on the substrate 62 then successively on the various superimposed layers created, until the desired thickness is obtained. The filament deposition system follows a deposition trajectory controlled by the management unit 51 to which it is connected ensuring control of the filament deposition system and controlling at any point of the treated surface both the filament arrangement and the porosity. of the medium necessary to guarantee the desired abradability.

The supply of abradable material is ensured from a conical extrusion screw 64 allowing several components to be mixed to form a thixotropic fluid having the appearance of a paste. The conical extrusion screw ensures an adequate and homogeneous mixture of the components (throughout the deposition operation), to ultimately obtain a high viscosity fluid material which will be deposited by the calibrated nozzle. During this operation, it is necessary to avoid the generation of air bubbles which form as many defects in the printed filament and it is therefore necessary to push the material very gradually. It will be noted that the change in the constitution of the deposited material can be achieved simply by checking the various components introduced successively into the conical extrusion screw which comprises at least two inlets 64A, 64B for the simultaneous introduction of the two components. A heating lamp 66 mounted near the ejection nozzle 46A and acting as a solidification module can be used to stabilize the deposited material and prevent creep during deposition.

FIG. 5 illustrates in exploded perspective a small part of the three-dimensional scaffolding 60 of filaments 100, 200, 300, advantageously cylindrical, of the abradable material allowing the production of the coating in the form of an ordered network of channels such as to confer acoustic properties to a wall 62 intended to receive this coating.

Indeed, the objective is to print, in the structure of the abradable material, specific patterns having dimensioned porosities allowing the passage or dissipation of aerodynamic fluctuations (see their modifications) and / or acoustic waves. These patterns may consist of perforations or grooves of dimensions less than 1.5 mm, furthermore making it possible to improve the aerodynamic margins. But, advantageously, these patterns consist of channels or microchannels forming an ordered network as shown by the different configurations of FIGS. 6A, 6B, 6C and 6D.

In FIG. 6A, the three-dimensional scaffolding of filaments 100, 200 consists of superimposed layers of which the filaments of a given layer are oriented alternately at 0 or at 90 ° without offset in the superposition of the filaments having the same direction.

In FIG. 6B, the three-dimensional scaffolding of filaments 100, 200 consists of superimposed layers of which the filaments of a given layer are oriented alternately at 0 or at 90 ° and have an offset in the superposition of the filaments having the same direction.

In FIG. 6C, the three-dimensional scaffolding of filaments 100, 200, 300, 400, 500, 600 consists of superimposed layers having directions of orientation of the filaments Di offset by the same angular difference, typically 30 °, to each layer i (i between 1 and 6).

And in FIG. 6D, the three-dimensional filament scaffold 100, 200 is made up of superimposed layers having, for each of the layers, both a 0 ° filament orientation and a 90 ° filament orientation, so as to form vertical perforations 700 of square sections between the filaments.

Printing on a crankcase sector with these different network configurations has shown the feasibility of such a filamentary deposit of abradable material according to the aforementioned additive manufacturing process. Tests of mechanical behavior in compression and bending were also carried out as well as samples intended for a low energy impact test or a characterization of the acoustic impedance at normal incidence. In particular, it has been observed a transmission of acoustic energy through the scaffolding and an absorption of part of this acoustic energy by modification of the aeroacoustic sources or absorption of propagating sound waves.

Figure 7 shows the different steps of the additive manufacturing process for coating on a fan casing for an orthogonal mesh structure such as that illustrated in figure 6A obtained with the device of figure 3, the fan casing 20A being positioned on its retaining support 40 movable in rotation.

In a first step 1000, the filament deposition system 46 is positioned by a series of vertical and axial translations above the material deposition zone, at the level of the axis 42 of the fan casing and at a distance determined with respect to to the internal surface of the fan casing, and the multi-nozzle support is oriented parallel to the axis 42 (so-called 0 ° position). In a following step 1002, the fan casing is set in rotation then causing a deposit of material in planes perpendicular to the axis 42, over the 360 ​​° of its circumference, with as many filaments of material as there are nozzles, the vertical position of each nozzle being individually controlled. In step 1004, the casing having returned to its initial position, the rotation of the fan casing ends and the nozzle support piece 56 then performs a rotation of 90 ° corresponding to the direction of orientation of the filaments of the second coating layer. In a step 1006, a first row of material filaments is deposited on a first sector of the housing by an axial displacement of the filament deposition system 46, so as to perform a deposit at 90 ° relative to the filaments of previously deposited materials

circumferentially around the axis 42. In the following step 1008, the fan casing performs a rotation corresponding to a determined angular deviation equal to the first sector already covered, then it is returned to step 1006 to make the deposits on the following sectors until covering the 360 ​​° circumference of the casing (test of step 1010). Steps 1000 to 1008 are then repeated until the desired material thickness is obtained (final test of step 1012).

It will be noted that if in the aforementioned description, the circumferential deposition is carried out by means of the rotation of the housing, it is understood that this deposition can also be carried out by rotation of the filament deposition system. Likewise, if the sectoral deposition is carried out by virtue of the axial displacement of the filamentary deposition system, it is understood that this deposition can also be carried out by an axial displacement of the casing. The important thing is that there is a relative displacement between the casing and the filament deposition system.

It will also be noted that if the method has been described with reference to the multi-nozzle support, it is clear that it is also applicable to the configuration with a single nozzle of FIG. 2, subject to providing after each 360 ° rotation an axial displacement. of the filament deposit system of a determined pitch (optional step 1016) in order, step by step, once all the 360 ​​° rotations have been completed, to cover the entire width of the casing.

In the manufacturing configuration of the coating having the structure with inclined mesh at regular angular intervals (every 30 °) such as that illustrated in FIG. 6C, the step 1004 of rotation is no longer 90 ° but only 30 ° , so as to carry out in the following step 1006 the deposition of the layer 200 at 30 ° and no longer at 90 °. And once this second layer 200 has been deposited, an additional rotation of 30 °, or 60 °, is carried out following the test of step 1014 to deposit the third layer 300 instead of a return to the initial position at 0 ° which is only produced in this configuration once the layer 600 corresponding to the last direction of orientation of the filaments has been deposited.

It should be noted that an additional layer can be added prior to the development of this three-dimensional scaffolding. In fact, the fan casing is a 3D woven composite casing whose three-dimensional geometry generally presents deviations.

(shape defects) with respect to the ideal calculated surface, due in particular to the tendency to form lobes linked to the weaving process used (conventionally of the poly-flex type). However, correcting these defects currently involves complex and expensive operations. It is therefore possible with the device to deposit a material for taking up play (resin or other) in order to obtain a known geometry. The advantage of this preliminary step is to return to a controlled deposit surface, precisely defined and meeting the shape constraints necessary to ensure the good aerodynamic clearances of the engine area.

It should also be noted that additional layers can be added locally in order to ensure the axisymmetry of the abradable surface. In fact, fan housings often have a non-axisy metric geometry.

The abradable material extruded by the calibrated nozzle (s) is advantageously a high viscosity thermosetting material which is devoid of solvent, the evaporation of which, as is known, generates high shrinkage. This material is preferably a resin with slow polymerization kinetics and stable filamentary flow in the form of a thixotropic mixture which therefore has the advantage of a much lower shrinkage between printing on the substrate (just after extrusion of the material) and the final structure (once heated and polymerization complete).

An example of an abradable material used in the context of the method of the invention is a material in pasty form and consisting of three components, namely a polymer base, for example an epoxy resin (in the form of blue modeling clay), a crosslinking agent or accelerator (in the form of white plasticine) and a translucent colored petroleum jelly (eg petrolatum ™). The accelerator / base components are distributed in a base to accelerator weight ratio of between 1: 1 and 2: 1 and petroleum jelly is present between 5 and 15% by weight of the total weight of the material. The base may further include hollow glass microspheres of a determined diameter to ensure the desired porosity while allowing increase the mechanical performance of the printed scaffolding. The advantage of the introduction of petroleum jelly lies in the reduction of the viscosity of the resin as well as of the reaction kinetics of the abradable, which makes its viscosity more stable during the printing time and facilitates thus the material flow. (Viscosity is directly related to the extrusion pressure needed to ensure the correct extrusion speed to maintain print quality).

By way of example, such a ratio of 2: 1 gives an abradable material comprising 0.7 g of accelerator and 1.4 g of base to which it is appropriate to add 0.2 g of petroleum jelly.

Thus, the present invention allows rapid and stable printing making it possible to efficiently reproduce high-performance controlled acoustic structures (roughness, appearance, opening rate) having a small filament size (<250 microns in diameter) and a low weight (porosity rate. improved> 70%) particularly interesting in view of the severe constraints encountered in aeronautics.

CLAIMS

1. A method of in situ deposition by additive manufacturing of a coating on a turbomachine casing consisting in depositing on an internal surface of said turbomachine casing (20A, 62) a filament (100, 200, 300, 400, 500, 600) of an abradable material along a predefined deposition path in order to create a three-dimensional scaffolding of filaments forming between them an ordered network (60) of channels, the method being characterized by the following steps:

positioning a filamentary material deposition system (46) at the level of a longitudinal axis (42) of said housing at a position and a determined distance with respect to said internal surface of said housing, depositing a first layer of said coating over 360 ° of the circumference of said casing by a relative circumferential displacement between said casing and said filamentary material deposition system (46),

rotating said filamentary material deposition system (46) by a first determined angle and positioning said filamentary material deposition system (46) at said longitudinal axis of said housing at a determined position and distance from said first layer of said coating,

depositing on a sector of said casing by a relative axial movement between said casing and said filamentary material deposition system, a second layer of said coating on said first layer of said coating,

effect a relative circumferential displacement between said casing and said filamentary material deposition system (46) by a determined angular deviation corresponding to the first sector already covered during the deposition of said second coating layer,

and repeating the step of depositing on said housing sector and the step of relative circumferential displacement according to said angular deviation determined for the following sectors until covering the 360 ​​° of the circumference of said housing, and

after having rotated said filamentary material deposition system by a second determined angle, resume

all of the previous steps for the following layers until a desired coating thickness is obtained.

2. A method of in situ deposition by additive coating manufacturing according to claim 1, characterized in that prior to the deposition of said first layer of said coating, a layer of a backlash take-up material is deposited on said turbomachine casing for obtain a deposit surface of known geometry.

3. A method of in situ deposition by additive coating manufacturing according to claim 1 or claim 2, characterized in that said step of rotating said filament deposition system is carried out twice by successive rotation of 90 °, the first determined angle being equal to 90 °.

4. A method of in situ deposition by additive coating manufacturing according to claim 1 or claim 2, characterized in that said step of rotating said filament deposition system is carried out as many times as there are determined directions of orientation of the different filaments.

5. A method of in situ deposition by additive coating manufacturing according to claim 4, characterized in that said step of rotating said filamentary deposition system is carried out six times by successive rotation of 30 °, the first determined angle being equal to 30 °. .

6. A method of in situ deposition by additive manufacturing of a coating according to any one of claims 1 to 5, characterized in that additional layers of said coating are added locally to take account of a non-axisymmetric geometry of said turbomachine casing.

7. A method of in situ deposition by additive coating manufacturing according to any one of claims 1 to 6, characterized in that the deposition of filamentary material is carried out by a plurality of ejection nozzles (54A-54E) whose positioning vertical of each of said ejection nozzles is adjustable independently.

8. A method of in situ deposition by additive coating manufacturing according to any one of claims 1 to 7, characterized in that said turbomachine casing is a fan casing made of woven composite material.

9. Filamentary material deposition system (46) for implementing the in situ deposition process by additive coating manufacturing according to any one of claims 1 to 8.

10. Abradable coating of the turbomachine wall obtained from the in situ deposition process by additive manufacturing of the coating according to any one of claims 1 to 9.