WO2024256783A1 - Preheating module, furnace comprising such a preheating module and method for densifying and consolidating a part by means of such a preheating module - Google Patents

Abstract

The invention relates to a preheating module (10) comprising a dispersion chamber (11) that comprises a unit (20) for distributing the gas mixture comprising an inlet (25) located at the lower edge (17) and a plurality of inner walls (22) forming a flow path (21) for the gas mixture; and a diffusion chamber (12) located downstream of the dispersion chamber (11) and arranged above the dispersion chamber, and forming, together with the dispersion chamber, a stack. The flow path (21) of the gas mixture runs mainly along longitudinal (Y) and transverse (Z) axes orthogonal to a stacking axis (X), and the dimension of the diffusion chamber (12) along the stacking axis (X) does not differ by more than 20% relative to the dimension of the dispersion chamber (11) along this stacking axis.

Description

DESCRIPTION

TITLE: PREHEATING MODULE, OVEN COMPRISING SUCH A PREHEATING MODULE AND METHOD FOR DENSIFICATION AND

CONSOLIDATION OF A PART BY MEANS OF SUCH A PREHEATING MODULE

Technical field of the invention

The invention relates to the technical field of preheating modules intended to equip furnaces for the densification and consolidation of parts made of ceramic matrix composite (CMC), in particular carbide-based. The invention also relates to such furnaces. Finally, the invention relates to methods for densifying and/or consolidating a part made of ceramic matrix composite using such preheating modules.

Technical background

Such densification and/or consolidation processes are used, for example, in the aeronautics field in order to manufacture parts capable of withstanding high temperatures. This is particularly the case for parts forming the turbine(s) of an aircraft turbomachine, for example the sectors of the rings used to delimit the external periphery of a turbine vein.

Carbide-based CMC material parts are particularly proposed as an alternative to metal alloy-based parts because they have better mechanical properties at high temperatures and for a significantly lower density. For the purpose of manufacturing these parts, a mixture of reactive gases is injected into the furnace, then by decomposing on the hot surfaces of said parts, these reactive gases form a ceramic coating whose composition can be controlled. On the operational level, the formation of the ceramic layer is implemented by densifying and then consolidating the parts. These steps are generally implemented by Chemical Vapor Infiltration.

Before being injected into the furnace and reaching the parts, the gas mixture must be heated in order to prevent inhomogeneity of the gas mixture and to avoid a mismatch between the desired composition of the mixture and the composition actually obtained. In this respect, the gas mixture must be prepared to ensure its homogeneity and it must also be brought to the right temperature in order to obtain a coating of appropriate composition. Figures 1a and 1b respectively illustrate a 1-well furnace and a cellular furnace 1 for the consolidation and densification of a part made of CMC material. Each furnace comprises a treatment module 2 in which the consolidation and densification operations of the part(s) P are implemented, a depletion module 5 used to capture the residual part of the gas mixture and the reaction by-products, as well as a preheating module 10' used to gradually bring the gas mixture to the desired temperature in the treatment module 2. In this regard, each furnace 1 comprises, as the case may be, one or more injectors 4 conveying the reagents to be used. The reagents can thus, via an inlet located at a lower edge 17' of the preheating module 10', be released into the furnace 1. As illustrated in FIG. 1 a, the well furnace, the capacity of which is greater than the cellular furnace, can advantageously comprise several crucibles 4.

The preheating module 10’, the treatment module 2 and the depletion module are stacked in this order from a lower edge of the furnace to an upper edge of the furnace. In other words, the preheating module 10’ is located upstream of the treatment module 2 and the treatment module 2 is itself located upstream of the depletion module 5 along a stacking axis X of the preheating module 10’, the treatment module 2 and the depletion module 5. This stacking axis X also defines the main flow direction of the gas mixture. In this regard, the treatment module 2 comprises a cavity 3 for accommodating the part(s) P. As illustrated in FIGS. 1 a and 1 b, the well furnace differs from the cellular furnace in that it comprises a cavity 3 generally comprising several stages superimposed along the stacking axis X. In the example illustrated in Figure 1a, the cavity 3 comprises two stages. The cavity of the cellular furnace illustrated in Figure 1b comprises only one stage, but it can comprise several stages.

Figure 2a illustrates more precisely a preheating module 10' known from the prior art. This preheating module 10' can be used indifferently in a well furnace or a cellular furnace. The preheating module 10' according to the prior art comprises a dispersion chamber 1 T of the gas mixture and a diffusion chamber 12' of this gas mixture as is better visible in Figure 2a. The diffusion chamber 12' is separated from the dispersion chamber 1 T by a heat transfer cavity 30' comprising a plurality of horizontal walls spaced from each other vertically. The dispersion chamber 1 T comprises, at the lower edge 17' of the preheating module, an inlet 25' as well as one or more horizontal walls 22', spaced from each other along the stacking axis X, which comprise a plurality of openings for dispersing the gas mixture. If the homogeneity of the gas mixture is to be improved, the number of horizontal walls 22' must be increased. The diffusion chamber 12', including the cavity 30' of heat transfer, also includes a plurality of walls having openings for diffusing the gas mixture.

Thus, when the gas mixture circulates within the preheating module 10’, including within the dispersion chamber 11’, it moves mainly vertically, that is to say from the lower edge 17’ of the preheating module to an upper edge 18’ of the preheating module, using the passages created by the openings. These movements of the gas mixture through the openings produce what is called a “baffle” of the gas mixture, which makes it possible to offer this gas mixture a hot surface allowing it to gradually reach the desired temperature, namely the temperature at which it is desired to carry out the consolidation and densification of the CMC material, by heat exchanges with the surfaces of the walls. These exchanges are effective when the gas mixture diffuses transversely relative to the convective flow, which is favored when the gas mixture moves at low speed and low flow rate. The flow is generally of the laminar type.

That being said, in such furnaces, the preheating module 10’ occupies a relatively large volume. Typically, the volume of the preheating module represents approximately 20% of the volume of the stack. This is explained by the respective dimensions of the dispersion chamber 1 T and the diffusion chamber 12’ in the direction of the stack. Indeed, the diffusion chamber 12’, including the heat transfer cavity 30’, also comprises a plurality of walls having openings for diffusing the gas mixture. The diffusion chamber 12’ can therefore have a dimension up to three times greater than that of the dispersion chamber 1 T in the stacking axis. In pit furnaces, this is acceptable to the extent that the parts can be loaded onto the different stages. However, manufacturers are forced to adapt the furnaces and in particular to reduce their dimensions, especially along the stacking axis, in order to allow easier integration of these furnaces into pre-existing production lines. It is in this context that the cellular furnaces, previously mentioned, were developed.

The invention aims to overcome at least part of the above problems and provides a preheating module for a furnace for the consolidation and densification of CMC material parts having reduced dimensions in the main direction of movement of the gas mixture and allowing improved gas mixing despite the reduced dimensions.

Documents US 2017/002466 A1 , US 6,572,371 B1 , US 5,480,678 A, US 2007/275339 A1 and CN 109,400,198 A disclose preheating modules for an oven. However, none of these documents addresses the above-mentioned problems, in particular improved gas mixing in the preheating module despite its reduced dimensions.

Summary of the invention

The invention provides for this purpose a preheating module for a furnace, the preheating module comprising a dispersion chamber and a diffusion chamber arranged above the dispersion chamber and forming with the dispersion chamber a stack along a stack axis, the preheating module being intended to be traversed by a gas mixture moving along said stack axis from a lower edge of the preheating module to an upper edge of the preheating module, the dispersion chamber comprising a gas mixture bursting unit comprising an inlet located at the lower edge and a plurality of inner walls forming a flow path for the gas mixture, and the gas mixture diffusion chamber being located downstream of the dispersion chamber in the direction of circulation of the gas mixture, and comprising a heat transfer wall separating this diffusion chamber from the dispersion chamber, the gas mixture flow path extending mainly in directions of longitudinal and transverse axes orthogonal to the stacking axis, and the dimension of the diffusion chamber along the stacking axis not differing by more than 20% from the dimension of the dispersion chamber along this stacking axis.

The preheating module is characterized in that each inner wall comprises a plurality of fins extending from at least one surface of this inner wall, each fin making an open angle with the associated inner wall in the principal directions of flow of the gas mixture within the bursting unit.

Thus, in contrast to known preheating modules, the preheating module according to the invention has a significantly reduced dimension along the stacking axis. In fact, when the gas mixture enters the bursting unit and flows in the flow path, it can flow mainly along the longitudinal axis and transverse axis directions and thus orthogonally to the main direction of movement. In other words, the main components of the movement of the gas mixture are the components of movement along the longitudinal axis and the transverse axis. The dispersion of the gas mixture therefore takes place mainly orthogonally to the stacking axis instead of along this stacking axis. This makes it possible to significantly reduce the dimensions of the dispersion chamber along the stacking axis. Furthermore, in addition to being able to reduce the dimensions of the dispersion chamber, it is also possible to reduce the dimensions of the diffusion chamber. Indeed, since the dispersion chamber comprises a plurality of internal walls, numerous heat exchanges occur therein, which makes it possible to increase the potential for heat exchanges of the gas mixture in the dispersion chamber compared to the furnaces of the prior art. Incidentally, it is possible to reduce the surface area required for heat exchanges in the stacking axis, which makes it possible to reduce the transfer cavity to a simple heat transfer wall. Indeed, as previously mentioned, the preheating modules of the prior art comprise a cavity serving to provide contact surface area for heat exchanges which separates the dispersion chamber and the diffusion chamber. However, this cavity comprises a plurality of horizontal walls spaced from each other, which increases the dimension of the preheating module in the stacking axis. Thus, the diffusion chamber can have, along the stacking axis, dimensions comparable to those of the dispersion chamber.

The fins further improve the mixing of the gases injected into the bursting unit. Each of them makes an open angle with the associated inner wall in the main flow directions, which allows the gas mixture to maintain an appropriate flow velocity within the bursting unit while improving the mixing process.

According to various features of the invention which may be taken together or separately: a ratio between a length of the flow path and a dimension of the preheating module, along the longitudinal axis and/or the transverse axis is between 4 and 150; the inner walls are separated from each other by a distance between 20 mm and 100 mm; the bursting unit comprises at least one stage delimited, along the stacking axis, by a first peripheral wall and a second peripheral wall, the inner walls extending between the first peripheral wall and the second peripheral wall orthogonally to said first and second peripheral walls; the preheating module comprises at least one side wall extending around the stacking axis, said side wall comprising at least two diametrically opposed portions, and wherein a first series of inner walls extends from a first portion of the side wall and a second series of inner walls extends from a second portion of the side wall, the inner walls of the first series and the inner walls of the second series being arranged parallel to each other in a one-to-one alternating manner; the inner walls comprise two walls distal to a center of the first peripheral wall, the distal walls having a plurality of openings; the inner walls are arranged in a spiral shape; a third series of inner walls extends from the first peripheral wall and a fourth series of inner walls extends from the second peripheral wall, the inner walls of the third series and the inner walls of the fourth series being arranged parallel to each other in a one-to-one alternating manner; the transfer wall comprises a plurality of first openings occupying 20% to 35%, not inclusive, of a total surface area of the transfer wall; the diffusion chamber comprises a plurality of diffusion walls, each diffusion wall having second openings occupying 35% to 50% of a total surface area of the diffusion walls, preferably between 40% and 60% of a total surface area of the diffusion walls.

The invention also relates to a furnace for the consolidation and densification of a part made of ceramic matrix composite material, the furnace comprising a treatment module comprising a cavity for receiving this part, and a preheating module as previously described, the preheating module being located under the treatment module and forming with the treatment module a second stack along the stacking axis.

The invention further relates to a method for consolidating and densifying a ceramic matrix composite part implemented using a furnace as previously described, the method comprising the following steps in this order:

110) provide an oven as previously described,

120) waiting for the temperature in the bursting unit to reach a value between -100°C and -200°C relative to a desired temperature in the treatment module and the temperature in the diffusion chamber to reach a value between -30°C and -5°C relative to the desired temperature in the treatment module,

130) concomitantly or subsequently to step 120), inject the gas mixture into the oven and wait until it reaches the desired temperature.

Brief description of the figures

Other objects, characteristics and advantages of the invention will appear more clearly in the description which follows, made with reference to the appended figures, in which: - figure 1a is a schematic sectional view of a shaft furnace,

- figure 1 b is a schematic sectional view of a cellular furnace,

- figure 2a is a schematic sectional view of a preheating module known from the prior art,

- figure 2b is a schematic sectional view of a preheating module according to one embodiment of the invention,

- figure 2c is a schematic sectional view of a preheating module according to the invention,

- figure 3 is a schematic top view of a first example of a bursting unit for a preheating module according to an embodiment of the invention,

- figure 4 is a schematic top view of a second example of a bursting unit for a preheating module according to the invention,

- figure 5 is a schematic top view of a third example of a bursting unit for a preheating module according to the invention,

- figure 6 is a schematic sectional view of a fourth example of a bursting unit for a preheating module according to the invention,

- Figure 7 is a schematic view of a method of consolidating and densifying a part made of CMC material according to the invention.

Detailed description of the invention

In the present description, the terms “upper”, “lower” are not limiting and simply serve to better understand the invention with reference to the illustrated figures. The use of the term “lower” simply indicates that the element considered is closer to a lower edge, for example of the oven, in comparison with an element with which the term “upper” is associated. For example, “a lower edge of the preheating module” designates a part of the preheating module closer to the lower edge of the oven according to the invention.

When it is indicated that a first element is “upstream” of a second element, this means that the first element is located before the second element in relation to the direction of circulation, or travel, of the gas mixture. Similarly, when the term “downstream” is used to describe the positioning of an element in relation to another element, this means that the first of the elements considered is located after the other of the elements in relation to the direction of circulation, or travel, of the gas mixture.

With reference to Figures 1a, 1b and 2b, the invention relates to a furnace 1 for the consolidation and densification of a part P made of ceramic matrix composite material. The furnaces illustrated in Figures 1a and 1b and described in the preamble to this description are, respectively, a pit furnace and a cellular furnace. A preheating module 10, also the subject of the present invention, which will be described below, is equally well suited to a pit furnace, such as that of FIG. 1 a, as to a cellular furnace, such as illustrated in FIG. 1 b. The preheating module 10 is also suited to other types of furnaces which are not mentioned in the present description and which are used for the consolidation and densification of parts made of CMC material. Preferably, the furnace is capable of being placed under vacuum.

Before detailing this preheating module 10 in more detail and as mentioned previously, the furnace 1 comprises a treatment module 2 in which the consolidation and densification operations of the part(s) P are implemented, a depletion module 5 used to capture the residual part of the gas mixture and the reaction by-products, as well as the preheating module 10, the latter used to gradually bring the gas mixture to the desired temperature in the treatment module 2.

The preheating module 10, the treatment module 2 and the depletion module 5 are stacked in this order from a lower edge of the furnace 1 to an upper edge of this furnace 1. In other words, the preheating module 10 is located under the treatment module 2, the latter itself being located under the depletion module 5 from the lower edge of the furnace 1. More precisely, the gas mixture circulates from a lower edge 17 of the preheating module to an upper edge 18 of this preheating module by crossing the different zones of the preheating module 10.

The gas mixture is composed of several reactive gases. The reactivity of the gases can come from several factors known to those skilled in the art. It can, for example, be reinforced by the temperatures at which these gases are heated within the preheating module 10. In the context of the present invention, the gas mixture is not limited to a particular type of precursor. It is simply appropriate to choose a gas mixture appropriate for the intended application. In this regard, according to an application of the invention, the part P is made of a composite material with a ceramic matrix based on carbide. For example, the part P can be made of silicon carbide (SiC), boron nitride (BN), carbon, or even SiBN. In all cases, it is appropriate to use reactive gases appropriate for the consolidation and densification of the part in the material from which this part is made.

The preheating module 10 according to the invention comprises a dispersion chamber 11 and a diffusion chamber 12 arranged above the dispersion chamber 11 and forming with the dispersion chamber 11 a stack along a stacking axis X. This stacking axis X also defines the main flow direction of the gas mixture. in the furnace 1 and the stacking axis of the preheating module, the treatment module 2 and the depletion module 5. The diffusion chamber 12 is located downstream of the dispersion chamber 11 in the direction of circulation of the gas mixture. The diffusion chamber 12 comprises a heat transfer wall 30 which separates it from the dispersion chamber 11. We will return to this in more detail later.

The dispersion chamber 11 has the role of dispersing the gases in order to allow a first mixing of these gases. The gases therefore do not necessarily enter in the form of a gas mixture into the dispersion chamber 11 and may only be mixed inside this dispersion chamber 11. The dispersion chamber 11 also has the function of homogenizing the gas mixture. This improves the heating of the gas mixture, that is to say that the temperature setting of said gas mixture is facilitated. On leaving the dispersion chamber 11, the gases are therefore not only in the form of a mixture but also in the form of a homogeneous mixture. In this regard, the dispersion chamber 11 comprises a unit 20 for bursting the gas mixture making it possible to mix and homogenize the gases.

The bursting unit 20 is provided with an inlet 25 located at the lower edge 17 of the preheating module. It is through the inlet 25 that the gases or the gas mixture, as the case may be, enter(s) the furnace 1 according to the invention. As mentioned above, the furnace 1 comprises one or more injectors 4 containing the reagents necessary for the process of consolidation and densification of the part. The reagents are generally brought into the furnace in a gaseous form at room temperature. The reagents are more precisely injected into the bursting unit 20 via the inlet 25 in order to be mixed therein homogeneously.

In the embodiment illustrated in FIG. 2b, the inlet 25 consists of a single opening formed in the lower edge 17 of the preheating module. However, the inlet 25 may be formed of a plurality of openings. The number, shape and dimensions of the openings are not limiting within the scope of the invention. That being said, as we will see later, it is preferable for the dimensions of the opening or openings forming the inlet 25 to be chosen so as to allow the reactants to enter the bursting unit 20 at a speed of between 0.1 m/s (meters per second) and 10 m/s, preferably between 0.1 m/s and 2 m/s. This in fact gives the gas mixture appropriate movement kinetics within the bursting unit 20.

The bursting unit 20 includes a plurality of interior walls 22 that form a flow path 21 for the gas mixture. The flow path 21 is a passage formed in the flow unit 20 that guides the gas mixture from the inlet 25 of the bursting unit to an outlet 26 of the bursting unit. The path 21 marks thus the path of the gas mixture as it flows within the bursting unit 20. Beyond these considerations, the path 21 is configured to disperse the gas mixture as it flows within the bursting unit 20, which we will discuss in more detail later.

In the embodiment illustrated in FIG. 2b, the bursting unit 20 comprises a stage 20a delimited, along the stacking axis X, by a first peripheral wall 23 and a second peripheral wall 24 between which the inner walls 22 extend. That being said, the bursting unit 20 may comprise a plurality of stages 20a, 20b, ... as illustrated in FIG. 2c, the stages being located one after the other along the stacking axis X. In this configuration, the bursting unit 20 comprises intermediate walls 23i between each stage 20a, 20b, ... which form the physical limit between each stage.

Preferably, the intermediate walls 23i have the same longitudinal and transverse dimensions as the first 23 and second 24 peripheral walls. Also preferably, the configuration, namely the arrangement of the inner walls 22, is identical from one stage to the next. This makes it possible in particular to simplify the manufacturing process of the preheating module 10. However, this is not mandatory. In addition, it is preferable for the number of stages in the bursting unit 20 not to exceed two, which makes it possible to have a good compromise between obtaining a sufficient and homogeneous gas mixture on the one hand and a height of the preheating module 10, the height of the preheating module 10 being its dimension along the stacking axis X. It is preferable to maintain a height of at least 20 mm for each stage in order to allow sufficient flow of the gas mixture in the path 21 while promoting heat exchanges.

In the illustrated embodiment, the distal inner walls 22 are continuous, i.e. they do not include openings. The gas mixture passes from one stage to the other by means of openings 22f located near the ends of the intermediate walls 23i. The gas mixture therefore travels through almost the entire upstream stage, i.e. the lower stage, before reaching the downstream stage, the upper stage. Furthermore, it can only exit the upper stage through a distal opening 24a of the openings 22f of the lower stage. In the illustrated embodiment, the distal opening 24a is made in the center of the second peripheral wall 24, which allows the mixture to travel the path 21 of the upper stage again before exiting the bursting unit 20.

As illustrated in FIG. 2b, it is advantageous to leave a passage between the stage 20a and the transfer wall 30 so that the gas mixture can reach the diffusion chamber 12 from the bursting unit 20. When the bursting unit 20 comprises several stages 20a, 20b, etc., it is advisable to leave a sufficient gap between the last stage and the wall 30 transfer along the stacking axis X, the last stage being the downstream stage of the bursting unit 20 in the direction of gas flow. Preferably, the gap between the last stage of the bursting unit 20 and the transfer wall 30 along the stacking axis X is greater than or equal to 20 mm.

According to the invention, the flow path 21 of the gas mixture extends mainly in directions of longitudinal axes Y and transverse axes Z, the longitudinal axis Y and the transverse axis Z being orthogonal to the stacking axis X. This can be better seen in FIGS. 3 to 5 illustrating a top view in section of the interior of the bursting unit 20 according to alternative embodiments of the preheating module 10 according to the invention. In these different alternative embodiments which will be described in more detail below, the inner walls 22 are arranged so that the flow path 21 of the gas mixture extends mainly orthogonally to the stacking axis X.

Thus, the gas mixture, forced to follow the path 21, flows mainly in directions orthogonal to the stacking axis X. In other words, the main components of the three-dimensional displacement of the gas mixture are defined along the longitudinal axis Y and the transverse axis Z. Under these conditions, the “horizontal” volume of the bursting unit 20 is therefore essentially used to mix and homogenize the gas mixture instead of its “vertical” volume. Rather than increasing the number of walls along the stacking axis X to improve the dispersion and homogenization of the gases, it is possible to increase the number of inner walls 22 along the longitudinal axis Y or the transverse axis Z. Better results can also be obtained in terms of mixing and homogenization of the gas mixture compared to the prior art because the path 21 to be traveled can be significantly lengthened, this without adversely affecting the dimensions of the preheating module 10, and subsequently of the furnace 1 in the stacking axis X. Since the gases are mixed better and moreover more homogeneously, the gas mixture is able to heat up more quickly than in the furnaces of the prior art.

Still according to the invention, the dimension of the diffusion chamber 12 along the stacking axis X does not differ by more than 20% compared to the dimension of the dispersion chamber 11 along this stacking axis. Indeed, the dimension of the diffusion chamber 12 along the stacking axis X can be significantly reduced to the extent that, as indicated above, the gas mixture can be heated more quickly. This has the direct consequence of allowing a reduction in the useful surface, that is to say of the useful area, for heating the gas mixture. The diffusion chamber 12 can therefore have much fewer walls either at the level of the transfer zone (transfer wall 30) heat than in the diffusion zone (diffusion walls 35). In the invention, the heat transfer zone can therefore be reduced to a transfer wall 30 instead of having a heat transfer cavity 30' comprising a plurality of transfer walls. The size of the diffusion chamber 12 can therefore be divided by three in comparison with the size of the diffusion chambers 12' known from the prior art.

Very advantageously, a ratio between a length of the flow path 21 and a dimension of the preheating module, along the longitudinal axis Y and/or the transverse axis Z is between 4 and 150. The term “length of the path 21” is understood to mean the distance over which the flow path 21 extends, taking into account the tortuosities made by the latter. The term “tortuosities” is understood to mean the different changes of direction made by the flow path 21 in the absence of discontinuity, i.e. of break in said path 21. The appropriate length of the flow path 21 depends on the dimensions of the preheating module 10, so that it is appropriate to adapt the length of the path 21 according to the dimensions of the preheating module.

In this range of values, the gas mixture is forced to make at least one change of direction while moving inside the bursting unit 20. In practice, in this range of values, the gas mixture undergoes several changes of direction while circulating within the bursting unit 20, which increases the residence time of the gas mixture in the bursting unit 20 and therefore further promotes gas mixtures. Furthermore, the longer the residence time of the gas mixture in the bursting unit 20, the more homogeneous the gas mixture obtained. For example, if the number and nature of the reactants justify it, it is appropriate to choose a path 21 of great length while taking into account the overall dimensions of the preheating module 10. A person skilled in the art will therefore adapt the length of the path 21 according to these parameters.

The homogenization of the gas mixture can be continued at the outlet of the bursting unit 20. In this regard, inner walls 22 distal to the inlet 25 can comprise a plurality of openings 22e. The openings 22e in fact make it possible to manage the pressure losses at the outlet of the bursting unit 20. In FIG. 2b which does not show a sectional view, one of these openings 22e can be seen. The distal inner walls 22 are the inner walls 22 furthest from the inlet 25 through which the gas mixture enters the bursting unit 20. In the exemplary embodiment illustrated in FIG. 2b, these distal inner walls 22 are the outer inner walls 22 relative to the central position of the inlet 25. However, the inlet 25 does not necessarily occupy a central position in the preheating module 10 and, similarly, the distal inner walls 22 are not necessarily the outer inner walls 22. As best seen in Figure 2b, the inner walls 22 extend between the first 23 peripheral wall and the second 24 peripheral wall orthogonally to said first 23 and second 24 peripheral walls. The inner walls 22 of the unit

20 bursting units therefore extend vertically in this case - unlike the horizontal walls 22' of the dispersion chamber 11' known from the prior art - over the entire height of the stage 20a of the bursting unit. It should be noted that the height of the stage 20a corresponds to the distance separating the first peripheral wall 23 and the second peripheral wall 24.

When there are several floors 20a, 20b, ... as illustrated in FIG. 2c, it is then important that at each floor the interior walls 22 extend between the walls delimiting this floor. This may be, depending on the case, between the first peripheral wall 23 and one of the intermediate walls 23i or between two intermediate walls 23i or between one of the intermediate walls 23i and the second peripheral wall 24. Furthermore, as can be well understood, these are the interior walls 22 with the exception of the interior walls 22 distal to the entrance when the latter are perforated, that is to say comprise a plurality of openings 22e, since by nature these distal interior walls 22 do not extend over the entire height of the floor 20a or of each floor.

The fact, as described above, that the inner walls 22 extend over the entire height of the bursting unit 20 makes it possible to promote a laminar flow in which the shear stresses are imposed by the tortuosities of the path 21. Thus the mixing and homogenization of the gas mixture are adjustable by the length of the path.

21 and the path imposed on the gas mixture by the path 21 and little, if any, dependent on the surface properties of the inner walls 22 themselves. In other words, the continuity of the inner walls 22 over the height of the stage 20a allows the control of the flow dynamics of the gas mixture in the bursting unit 20 to be ensured by the tortuosities of the path 21. Similarly, the roughness and textures of the surfaces of these inner walls 22 could also play a role in this flow dynamics. In the present case, the flow dynamics is little dependent on the roughness or texture of the surfaces because the phenomena occurring at the macroscopic level, taking into account the tortuosities of the path 21, are preponderant.

In this regard, according to one aspect of the invention, each of the inner walls comprises a plurality of fins 27 extending from at least one surface of this inner wall. Such fins are for example visible in FIG. 4. They make it possible to further improve the mixing of the gases injected into the bursting unit 20. The fins 27 are in the form of projections extending obliquely from the surfaces of the inner walls 22. More precisely, each fin 27 makes an open angle with the wall 22 internal to which it is associated in the main directions of flow of the gas mixture within the bursting unit 20.

Each of them makes an open angle with the associated inner wall in the main flow directions, which allows the gas mixture to maintain an appropriate flow speed within the bursting unit while improving the mixing process. Indeed, a flow speed that is too low would increase the preheating time, which would impact the duration of the densification and consolidation process implemented with the furnace 1. A flow speed that is too high would not allow sufficient exchange to be obtained, which would therefore not allow the desired temperature to be reached at the outlet of the preheating module 10. The presence of the fins 27 and their respective positioning with respect to the inner wall, i.e. with an open angle in the main flow directions, therefore makes it possible to find a compromise between flow speed of the mixture and improvement of the mixing of the gases. In this regard, let us specify at this stage that the mixing of the gases is improved in that the mixing process results in better homogenization of the gases in the mixture.

As illustrated in FIG. 4, the fins 27 can extend as desired from both surfaces of an inner wall 22 or extend only from one of the surfaces of an inner wall 22. This choice is made ab initio, that is to say at the time of designing the preheating module 10 according to the invention, depending on the dimensional constraints, in particular along the longitudinal axis Y and/or along the transverse axis X, for the manufacture of said preheating module.

It should be noted that when speaking of the surfaces of the inner walls 22, as is the case above, we are speaking of the two large surfaces of the inner walls 22. These surfaces are “large” as opposed to the four lateral surfaces of the inner walls 22, these lateral surfaces each having at least one dimension smaller than the others which corresponds in particular to the thickness of the associated inner wall 22. The large surfaces are directly swept by the gas mixture unlike the four lateral surfaces.

Preferably, the inner walls 22 are separated from each other by a distance or gap of between 20 mm and 100 mm, which makes it possible to provide heat exchange surfaces between the gas mixture and the solid surfaces of the inner walls 22. These distances may vary according to the general dimensions of the preheating module. Too small a gap may lead to premature blocking of the path 21 and pressure loss phenomena may occur. In such a situation, it may be difficult to achieve the appropriate pressure in the furnace 1. Too large a gap makes the heat exchanges between the gas mixture and the less efficient inner walls 22. Preferably, the inner walls 22 are separated from each other by a distance of between 40 mm and 60 mm, which represents a good compromise between the risk of blockage of the path 21 and the efficiency of the heat exchanges.

For the same reasons, the first peripheral wall 23 and the second peripheral wall 24 are preferably separated by a distance di between 20 mm and 100 mm, and more preferably between 40 mm and 60 mm.

In the following sections, we describe various alternative embodiments of the bursting unit 20. These alternative embodiments are only examples and the invention is in no way limited by the illustrated configurations.

As a preliminary point, with regard to the embodiments illustrated in FIGS. 2b to 6, let us specify that the preheating module 10 comprises at least one side wall 13 extending around the main axis X, this side wall 13 preferably comprising at least two diametrically opposed portions 13a, 13b. In the illustrated embodiments, the side wall 13 has a parallelepiped shape in sectional view. However, this is not obligatory and the side wall 13 may quite have a section of another shape, for example a circular section. Whatever the shape chosen, and as indicated above, the wall may preferably comprise at least a first portion 13a and a second portion 13b diametrically opposed to the first portion 13b.

According to a first embodiment variant illustrated in FIG. 3, a first series of interior walls 22a extends from the first portion 13a of the side wall and a second series of interior walls 22b extends from a second portion 13b of the side wall, the interior walls 22a of the first series and the interior walls 22b of the second series being arranged parallel to each other alternately one by one. In other words, the interior walls 22a of the first series and the interior walls 22b of the second series are parallel and arranged so that an interior wall of one of the series is interposed between two successive interior walls of the other of the series, with the exception of course of the distal interior walls 22. In the illustrated example, each series comprises a total of four interior walls 22a, 22b respectively. This forms a path 21 in which substantially II-shaped half-loops follow one another. This configuration makes it possible to obtain a path 21 which is both compact and which promotes heat exchange.

The bursting unit 20 illustrated in Figure 4 differs substantially from that illustrated in Figure 3 only in that the inner walls 22 include fins 27, which as seen previously, further promotes heat exchange. As Also illustrated in Figures 3 and 4, the inlet 25 occupies a substantially central position on the first peripheral wall 23, so that the inner walls 22a of the first series and the inner walls 22b of the second series are arranged on each side thereof. In this configuration, there are in practice two paths 21 in which the gas mixture circulates by performing the same paths but in opposite longitudinal and transverse directions.

According to a second embodiment variant illustrated in FIG. 5, the inner walls 22 are arranged in a spiral or labyrinth shape. This configuration has the advantage of offering a path 21 of greater length than the configuration seen with reference to the first embodiment variant. Indeed, there is less wasted space around the central zone of the first peripheral wall 23, which in this embodiment is occupied by the outlet 26 of the bursting unit 20. Thus, the gas mixture travels a longer path, which makes it possible to further promote the mixing and homogenization of the gases between the inlet 25 and the outlet 26. In this regard, in this embodiment, the inlet 25 is positioned at one end of the bursting unit 20, while as indicated above the outlet 26 occupies a central position. This makes it easier to implement the labyrinthine profile of the path 21.

According to a third embodiment variant illustrated in FIG. 6, a third series of interior walls 22c extends from the first peripheral wall 23 and a fourth series of interior walls 22d extends from the second peripheral wall 24, the interior walls 22c of the first series and the interior walls 22d of the second series being arranged parallel to each other in alternation one by one. This configuration differs from that seen in the first variant only in that instead of extending from the first and second portions 13a, 13b of the side wall, the interior walls 22 extend from the first 23 and second 24 peripheral walls.

Thus, the inner walls 22c of the third series and the inner walls 22d of the fourth series are parallel and arranged so that an inner wall of one of the series is interposed between two successive inner walls of the other of the series, with the exception of course of the distal inner walls 22. In the example illustrated, each series comprises a total of eight inner walls 22a, 22b respectively. This forms a path 21 in which substantially II-shaped half-loops follow one another. This configuration makes it possible to obtain a path 21 which is both compact and which promotes heat exchange.

According to a particularly advantageous embodiment, the ratio between the surface created on the one hand by the interior walls 22, the peripheral walls 23, 24 and, where appropriate where appropriate, the intermediate walls 23i and on the other hand by the volume of the bursting unit 20 is between 3.1 and 3.3. It should be noted, at this stage, that this ratio is between 3 and 4 in the dispersion chambers 11 'known from the prior art. This gives very high efficiency to the bursting unit 20 and more generally to the furnace 1. Indeed, the ratio between heat exchange surfaces and overall volume of the preheating zone is lowered. In a smaller volume, heat exchange is maintained at the appropriate level, or even at a higher level. This ratio may even be lower depending on the design methods.

When the gas mixture leaves the bursting unit 20, the heat exchanges must advantageously continue efficiently with the transfer wall 30. In this regard, the transfer wall 30 comprises a plurality of first openings 31 occupying 20% to 35%, not included, of its total surface area. Thus, the transfer wall 30 allows the mixture to continue its journey to the diffusion chamber 12 while having a useful surface area sufficient to carry out heat exchanges with the gas mixture. As will be seen below, the difference between the temperature of the transfer wall 30 and the desired temperature in the treatment module 2 is smaller than the difference between the temperature in the bursting unit 20 and the desired temperature in the treatment module 2.

Advantageously, the diffusion chamber 12 may in this regard comprise a plurality of diffusion walls 35, each diffusion wall 35 comprising second openings 36 occupying 35% to 50% of a total surface area of the diffusion walls 35, preferably between 40% and 60% of a total surface area of the diffusion walls 35. Thus, when the gas mixture arrives in the diffusion chamber 12, it can be diffused homogeneously to the treatment module 2.

The invention also relates to a method 100 for consolidating and densifying a ceramic matrix composite part P implemented by means of a furnace as described above. Before describing the method in more detail, in the following section, we detail the temperature ranges to which the different parts of the preheating module 10 are brought. However, it should be noted that the temperatures will depend on the methods implemented and the types of furnace used. The following section therefore only presents a guide for obtaining the desired temperature at the outlet of the preheating module 10.

Preferably, the dispersion chamber 11 is the furthest from the treatment module 2. It has a temperature between -200°C and -30°C relative to the desired temperature in the treatment module 2. More specifically, the bursting unit 20 has a temperature between -200°C and -100°C relative to the desired temperature in the treatment module 2. relative to the desired temperature in the treatment module 2. The transfer wall 30 may advantageously have a temperature of -30°C relative to the desired temperature in the treatment module 2. Preferably, the diffusion chamber 12 has a temperature between -30°C (at its transfer wall 30) and -5°C (at the upper edge 18 of the preheating module 10) relative to the desired temperature in the treatment module 2. This is how the area at which the object is located in the treatment module 2 can reach the desired temperature. The difference of 5°C relative to the upper edge 18°C of the preheating module is directly filled in a lower part of the treatment module.

With reference to FIG. 7, the method 100 comprises a first step 110) consisting of providing an oven 1 as previously described. Preferably, the part P made of CMC material is placed concomitantly in the treatment module 2 of the oven.

The method 100 comprises a second step 120) comprising two sub-steps 122) and 124). During the first sub-step 122), the temperature TUE in the bursting unit 20 is expected to reach a value between -100°C and -200°C relative to a desired TMC temperature in the treatment module 2. Indeed, the preheating module is supplied with cold gas, these gases subsequently being caused to heat up in the preheating module 10. During the second sub-step 124), the temperature TCD in the diffusion chamber 12 is expected to reach a value between -30°C and -5°C relative to the desired TMC temperature in the treatment module 2. The first sub-step 122) and the second sub-step 124) may be carried out concomitantly. This second step 120) can advantageously be implemented by means of a control module (not shown) used to control the oven 1 according to the invention. In this regard, the control module can be provided with a processor comprising the instructions for implementing the second step 120).

The method 100 comprises a third step 130) which can be carried out concomitantly or subsequently to the second step 120). During this third step 130, the gas mixture is injected into the furnace 1 and waited until it reaches the desired TMC temperature. This temperature is reached by means of the preheating module 10 as previously described. For this, the gas mixture passes successively from the preheating module 10 to the treatment module 2. Within the preheating module 10, the gas mixture passes, in this order, the bursting unit 20, the dispersion chamber 11 (zone outside the bursting unit), the transfer wall 30 and the diffusion chamber 12. As seen previously, the gas mixture carries out numerous heat exchanges with the surfaces of the interior walls 22 of the bursting unit 20 and then with the transfer wall 30 which makes it possible to reach the desired temperatures by extending the path of this gas mixture. Of course, if the bursting unit 20 comprises several stages 20a, 20b, ... then the gas mixture passes through each stage before exiting the bursting unit 20. Advantageously, the dimensions of the opening or openings forming the inlet 25 are chosen so as to allow the reactants to enter the bursting unit 20 at a speed of between 0.1 m/s and 10 m/s, preferably between 0.1 m/s and 2 m/s.

Then, during a fourth step 140), as the gas mixture has reached the desired temperature in the treatment module 2, the part is consolidated. The duration of this step depends on the process that is desired to be carried out and the pressure and temperature parameters chosen. During a fifth step 150), the part is densified. As for the consolidation step 140), the duration of this fifth step depends on the process that is desired to be carried out and the pressure and temperature parameters chosen.

Claims

1. Preheating module (10) for an oven (1), the preheating module (10) comprising a dispersion chamber (11) and a diffusion chamber (12) arranged above the dispersion chamber (11) and forming with the dispersion chamber (11) a stack along a stack axis (X), the preheating module (10) being intended to be traversed by a gas mixture moving along said stack axis (X) from a lower edge (17) of the preheating module to an upper edge (18) of the preheating module, the dispersion chamber (11) comprising a gas mixture bursting unit (20) comprising an inlet (25) located at the lower edge (17) and a plurality of interior walls (22) forming a flow path (21) for the gas mixture, and the gas mixture diffusion chamber (12) being located downstream of the dispersion chamber (11) in the direction of circulation of the gas mixture, and comprising a heat transfer wall (30) separating this diffusion chamber (12) from the dispersion chamber (11), the flow path (21) of the gas mixture extending mainly in directions of longitudinal (Y) and transverse (Z) axes orthogonal to the stacking axis (X), and the dimension of the diffusion chamber (12) along the stacking axis (X) not differing by more than 20% compared to the dimension of the dispersion chamber (11) along this stacking axis, the preheating module (10) being characterized in that each inner wall (22) comprises a plurality of fins (27) extending from at least one surface of this inner wall (22), each fin (27) making an open angle with the associated inner wall (22) in the main flow directions of the gas mixture within the bursting unit (20). 2. Preheating module (10) according to claim 1, wherein a ratio between a length of the flow path (21) and a dimension of the preheating module, along the longitudinal axis (Y) and/or the transverse axis (Z) is between 4 and 150. 3. Preheating module (10) according to any one of the preceding claims, in which the interior walls (22) are separated from each other by a distance of between 20 mm and 100 mm. 4. Preheating module (10) according to any one of claims 1 to 3, in which the bursting unit (20) comprises at least one stage (20a) delimited, along the stacking axis (X), by a first peripheral wall (23) and a second peripheral wall (24), the interior walls (22) extending between the first (23) wall peripheral and the second (24) peripheral wall orthogonally to said first (23) and second (24) peripheral walls. 5. Preheating module (10) according to claim 4, wherein the preheating module (10) comprises at least one side wall (13) extending around the stacking axis (X), said side wall (13) comprising at least two diametrically opposed portions (13a, 13b), and wherein a first series of interior walls (22a) extends from a first portion (13a) of the side wall and a second series of interior walls (22b) extends from a second portion (13b) of the side wall, the interior walls (22a) of the first series and the interior walls (22b) of the second series being arranged parallel to each other alternately one by one. 6. A preheating module (10) according to claim 5, wherein the inner walls (22) comprise two walls distal to a center of the first peripheral wall (23), the distal walls comprising a plurality of openings (22e). 7. Preheating module (10) according to claim 4, in which the inner walls (22) are arranged in a spiral shape. 8. Preheating module (10) according to claim 4, wherein a third series of inner walls (22c) extends from the first peripheral wall (23) and a fourth series of inner walls (22d) extends from the second peripheral wall (24), the inner walls (22c) of the third series and the inner walls (22d) of the fourth series being arranged parallel to each other alternately one by one. 9. Preheating module (10) according to any one of the preceding claims, in which the transfer wall (30) comprises a plurality of first openings (31) occupying 20% to 35%, not inclusive, of a total surface area of the transfer wall (30). 10. Preheating module (10) according to any one of the preceding claims, wherein the diffusion chamber (12) comprises a plurality of diffusion walls (35), each diffusion wall (35) comprising second openings (36) occupying 35% to 50% of a total surface area of the diffusion walls (35), preferably between 40% and 60% of a total surface area of the diffusion walls (35). 11. Oven (1) for the consolidation and densification of a part (P) made of ceramic matrix composite material, the oven (1) comprising a treatment module (2) comprising a cavity (3) for receiving this part (P), and a preheating module (10) according to any one of the preceding claims, the preheating module being located under the processing module (2) and forming with this processing module (2) a second stack along the stacking axis (X). 12. Method (100) for consolidating and densifying a ceramic matrix composite part (P) implemented by means of an oven according to claim 11, the method comprising the following steps in this order: 110) providing an oven according to claim 11, 120) waiting for the temperature (TUE) in the bursting unit (20) to reach a value between -100°C and -200°C relative to a desired temperature (TMC) in the treatment module (2) and the temperature (TCD) in the diffusion chamber (12) to reach a value between -30°C and -5°C relative to the desired temperature (TMC) in the treatment module (2), 130) concomitantly or subsequently to step 120), inject the gas mixture into the oven and wait until it reaches the desired temperature (TMC).