EP0761978A1 - Thermostructural composite material rotor, particularly of large diameter and its method of manufacturing - Google Patents

Abstract

The procedure consists of making a hub, flanges and blades from a thermo-structural composition material. The hub is made from a series of flat annular plates (21) which are fixed relative to one another. The blades are made individually from a two-dimensional fibrous material in plate or sheet form. Each blade is made in a pre-form which is compressed in a matrix to make a blank and then machines to the required shape. The two turbine flanges are also made from pre-forms of annular shape, essentially two-dimensional and compressed in a matrix, and when all the components have been made they are assembled, connecting each blade to the hub by inserting the blade foot (13) into a radial slot (23) of corresponding shape in the hub. The turbine components are made from a composition material such as carbon/carbon, or carbon fibres and a matrix of silicon carbide.

Description

The present invention relates to turbines, and more particularly those intended to operate at high temperatures, typically above 1000 ° C.

One field of application of such turbines is the mixing of gases or ventilation in ovens or similar installations used to carry out physicochemical treatments at high temperatures, the ambient medium being for example made up of neutral or inert gases.

Usually, these turbines are made of metal, generally made up of several elements assembled by welding. The use of metal has several drawbacks. Thus, the high mass of the rotating parts requires large shaft lines and very powerful motors and imposes anyway a limitation of the speed of rotation. A temperature limitation is added due to the risk of metal creep.

In addition, the sensitivity of the metal to thermal shock can cause cracks or deformation. This results in imbalances in the rotating mass favoring a reduction in the service life of the turbines and their drive motors. However, in the applications mentioned above, significant thermal shocks can occur, in particular in the event of massive injection of a cold gas, to cause the temperature to drop rapidly inside an oven in order to reduce the duration treatment cycles.

In order to avoid the problems encountered with metals, other materials have already been proposed for making turbines, in particular thmmtrostructural composite materials. These materials generally consist of a fibrous reinforcement texture, or preform, densified by a matrix and are characterized by their mechanical properties which make them suitable for constituting structural elements and by their capacity to maintain these properties up to high temperatures. . Common examples of thermostructural composite materials are carbon-carbon composites (CC) made of carbon fiber reinforcement and a carbon matrix, and ceramic matrix composites (CMC) made of carbon fiber reinforcement carbon or ceramic and a ceramic matrix.

Compared to metals, thermostructural composite materials have the essential advantages of a much lower density and great stability at high temperatures. The reduction in mass and the elimination of risk of creep can allow high speeds of rotation and, by the same token, very high ventilation rates without requiring oversizing of the drive members. In addition, thermostructural composite materials have a very high resistance to thermal shock.

Thermostructural composite materials therefore have significant performance advantages, but their use is limited due to their fairly high cost. In addition to the materials used, the cost comes essentially from the difficulties encountered in producing fibrous preforms, in particular when the parts to be manufactured have complex shapes, which is the case with turbines, and by the duration of the densification cycles.

Also, an object of the present invention is to provide a turbine architecture particularly suited to its production in thermostructural composite material in order to benefit from the advantages of this material but with a manufacturing cost as reduced as possible.

Another object of the present invention is to provide a turbine architecture suitable for the production of turbines of large dimensions, that is to say those whose diameter can greatly exceed 1 m.

• (a) on réalise le moyeu par empilement suivant un même axe de plaques annulaires planes en matériau composite thermostructural, et immobilisation des plaques les unes par rapport aux autres en rotation autour de l'axe,
• (b) on réalise individuellement chaque pale en mettant en oeuvre les étapes consistant à :
  • mettre en forme une texture fibreuse essentiellement bidimensionnelle en plaque ou en feuille, pour obtenir une préforme de pale,
  • densifier la préforme par une matrice pour obtenir une ébauche de pale en matériau composite thcrmostructural, et
  • usiner le contour de la préforme densifiée,
• (c) on réalise chaque flasque en mettant en oeuvre les étapes consistant à :
  • réaliser une préforme annulaire ou sensiblement annulaire au moyen d'une texture fibreuse essentiellement bidimensionnelle en plaque ou en feuille, et
  • densifier la préforme par une matrice pour obtenir une pièce en matériau composite thermostructural, et
• (d) on assemble les pales au moyeu, entre les flasques, chaque pale étant reliée au moyeu par une partie formant pied de pale.

According to one of its aspects, the subject of the present invention is a method for manufacturing a turbine comprising a plurality of blades arranged around a hub, between two flanges, the blades, the hub and the flanges being of thermostructural composite material, process by which:

• (a) the hub is produced by stacking, along the same axis, flat annular plates of thermostructural composite material, and immobilizing the plates in relation to each other in rotation about the axis,
• (b) each blade is produced individually by implementing the steps consisting in:
  • shaping an essentially two-dimensional fibrous texture into a plate or a sheet, in order to obtain a blade preform,
  • densify the preform with a matrix to obtain a blank of thcrmostructural composite material, and
  • machine the contour of the densified preform,
• (c) each flange is produced by implementing the steps consisting in:
  • producing an annular or substantially annular preform by means of an essentially two-dimensional fibrous texture in plate or sheet, and
  • densify the preform with a matrix to obtain a part made of thermostructural composite material, and
• (d) the blades are assembled to the hub, between the flanges, each blade being connected to the hub by a part forming the blade root.

Thus, for its essential parts, the turbine is produced by assembling parts having a simple shape, for example the flat annular plates composing the hub, or parts made from fibrous preforms having a simple shape (plate or two-dimensional sheet), for example blades and flanges.

This avoids the difficulties encountered in the manufacture and densification of preforms having complex shapes, or the material losses caused by machining of complex shaped parts in massive blocks of thermostructural composite material.

The connection of each blade with the hub can be achieved by inserting the blade root into a correspondingly shaped groove made in the hub. According to a particular feature of the process, the blade root is formed by placing an insert in a slot made in the fibrous texture used to make the preform of a blade.

According to another particular feature of the method, the constituent plates of the hub are assembled with at least one annular plate, constituting a first flange closing the passages between blades at one end of the turbine, by axial clamping on a shaft on which the turbine is mounted.

The second flange, which forms an annular fluid entry zone with the hub for suction through the passages between blades, is mounted on the blades, for example by engagement in notches of the flange of heels formed on the adjacent edges of the blades , and / or by gluing. As a variant, this second flange may be static.

According to another of its aspects, the invention relates to a turbine made of thermostructural composite material comprising a plurality of blades arranged around a hub, between two flanges, the turbine being characterized in that it comprises planar annular plates in thermostructural composite material stacked along the same axis, immobilized with respect to each other in rotation about the axis and forming a hub, and the blades made of thermostructural composite material are individually connected to the hub by a portion forming a blade root.

Advantageously, said flat annular plates of thermostructural composite material form an assembly comprising the hub and a first flange closing the passages between blades at one end of the turbine.

• la figure 1 est une vue en perspective partiellement arrachée montrant une turbine conforme à l'invention assemblée et montée sur un arbre ;
• la figure 2 est une vue partielle en coupe de la turbine de la figure 1 ;
• la figure 3 est une vue très schématique d'une pale de la turbine de la figure 1 ; et
• la figure 4 montre les étapes successives de réalisation de la pale de la figure 3.

Other features and advantages of the invention will emerge on reading the description given below, by way of indication but not limitation, with reference to the appended drawings, in which:

• Figure 1 is a partially broken away perspective view showing a turbine according to the invention assembled and mounted on a shaft;
• Figure 2 is a partial sectional view of the turbine of Figure 1;
• Figure 3 is a very schematic view of a blade of the turbine of Figure 1; and
• FIG. 4 shows the successive stages in the production of the blade of FIG. 3.

FIGS. 1 and 2 illustrate a turbine comprising a plurality of blades 10 regularly arranged around a hub 20, between two end flanges 30, 40. These various constituent elements of the turbine are made of a thermostructural composite material, for example a carbon-carbon composite material (CC) or a ceramic matrix composite material such as a C-SiC composite material (carbon fiber reinforcement and silicon carbide matrix).

The blades 10 delimit between them passages 11 for the circulation of fluid. At one axial end of the turbine, the passages 11 are closed by the annular flange 30 which extends from the hub 20 to the free outer edge 12 of the blades 10. At the other axial end, the flange 40, substantially annular in shape, extends over only part of the length of the blades 10, from their outer edge 12.

The free space between the internal edge 41 of the flange 40 and the hub 20 defines an entry zone from which a fluid can be sucked, through the passages 11, to be ejected at the level of the external crown of the turbine, as shown by the arrows F in Figure 2.

We will now describe the way in which the various constituent parts of the turbine are produced and, then, assembled.

The hub 20 is formed of annular plates 21 which are stacked along the axis A of the turbine. The plates 21 have the same internal diameter defining the central passage of the hub. In each plate, the outside diameter gradually increases from the face closest to the fluid entry zone to the opposite face, and the contacting faces of two neighboring plates have the same outside diameter, so that the assembly plates 21 forms a hub of regularly increasing thickness between the flange 40 and the flange 30, without discontinuity. Dovetail-shaped grooves 23 are formed at the periphery of the hub 20 in order to receive the feet of the blades 10 and ensure the connection of these with the hub as indicated in more detail in the following description. The grooves 23 extend axially over the entire length of the hub 20 while being regularly distributed around it. In the plates 21 of larger outside diameter, the grooves 23 communicate with the outside through grooves 23a whose width corresponds substantially to the thickness of a blade.

Each annular plate 21 is made individually of thermostructural composite material. For this purpose, it is possible to use a fibrous structure in the form of a plate in which an annular preform is cut. Such a structure is produced, for example, by flat stacking of layers of two-dimensional fibrous texture, such as a web of wires or cables, fabric, etc., and bonding of the layers between them by needling, as described for example in the document FR- A-2,584,106.

The annular preform cut from this plate is densified by the material constituting the matrix of the thermostructural composite material to be produced. Densification is carried out in a manner known per se by chemical vapor infiltration, or by liquid, that is to say impregnation with a precursor of the matrix in the liquid state and transformation of the precursor. After densification, the annular plate is machined to be brought to its final dimensions and to form the notches which, after stacking of the plates, constitute the grooves 23 and grooves 23a.

The plates 21 are secured in rotation about the axis A of the turbine by means of screws 26 which extend axially through all the plates. The screws 26 are machined from a block of thermostructural composite material.

The flange 30, which closes the passages 11 opposite the fluid entry zone, is made of thermostructural composite material by densification of a fibrous preform. The preform is produced for example by flat stacking of two-dimensional layers and bonding of the layers together by needling.

In the example illustrated, the flange 30 has a thickness which increases continuously from its periphery to its internal circumference. An annular intermediate plate 31 can be interposed between the hub 20 proper and the flange 30 proper, this plate 31 having an external profile such that it allows the face of the flange 30 facing the inside of the turbine to be connected without discontinuity on the outer surface of the hub 10. The plate 31 is secured in rotation with the plates 21 by means of the screws 26 made of composite material thermostructural. It will be noted that the profile of the flange 30 can be obtained from a preform produced by stacking annular layers whose outside diameter gradually decreases.

After densification, the flange is machined to its final dimensions. In particular, the internal annular face 37 of the flange 30 is given a frustoconical shape for mounting the turbine on a shaft. The flange 30 is joined to the hub 20 in rotation about the axis A by means of screws 36 made of thermostructural composite material which connect the flange 30 to the plate 31.

Each blade 10 is in the form of a thin plate with a curved surface, the outline of which is shown very schematically in FIG. 3. On the internal side intended to be connected to the hub 20, each blade 10 has a bulged part forming the foot of the blade 13 whose shape and dimensions correspond to those of the grooves 23 of the hub. The edge of the blade 10 located on the side of the fluid entry zone has, from the foot 13, a first concave curved portion 14a which ends in a radial projection forming a heel 16. The latter is connected to the edge d end 12 by a second concave part 14b. The edge of the blade opposite the fluid entry zone has, from the base 13, a radial part 15a extended by a convex part 15b which follows the profile of the adjacent faces of the intermediate plate 31 and of the flange 30.

Successive steps enabling the blade 10 to be made of thermostructural composite material are indicated in FIG. 4.

A deformable fibrous structure in the form of a sheet or plate is used, the thickness of which corresponds to that of the blade and which is formed for example by superposition and needling of two-dimensional fibrous layers as described in document FR-A-2 584 106 or else document FR-A-2 686 907.

The fibrous structure is cut to roughly reproduce the outline of the blade (step 100), then the edge corresponding to the location of the foot is split in order to introduce an insert I around which the parts of the fibrous structure located on the right and left sides. 'other of the slot are folded (step 101). The fibrous structure is then pre-impregnated with a resin and shaped in a tool T in order to give it a shape close to that of the blade to be produced (step 102). After crosslinking the resin in the tooling, a preform P of the blade is obtained. The resin is then pyrolyzed, leaving a residue, for example of carbon, which binds the fibers sufficiently together so that the preform P retains its shape. Densification can then be continued outside of the tool either by continuing by the liquid route, or by chemical vapor infiltration (step 103).

After densification, precise contouring of the blade is carried out in order in particular to form the heel 16 and the edges 12, 14, 15 (step 104).

The annular flange 40 has a curved profile corresponding to that of the edge portion 14b of the blades. It is produced by densification of a fibrous texture in the form of a sheet or plate, in the same way as the blades 10. After densification, the flange 40 is machined to be brought to its final dimensions and to form notches 46 intended to receive the heels 16 of the blades 10.

The assembly of the turbine is carried out as follows.

The blades 10 are hooked on the flange 40 by engagement of the heels 16 in the notches 46. Then, the hub 20 is formed by placing plates 21 one after the other, while inserting the feet 13 of the blades in the grooves 23. The plate 31 is put in place then the plates 21 are linked together and with the plate 31 by the screws 26. The flange 30 is then put in place, as are the screws 36. It will be noted that grooves respectively 44, 35 can be formed on the internal faces of the flanges 40 and 30 in which the edges 24b and 25b of the blades respectively can be inserted to ensure more effective retention of the blades.

Maintaining the assembled state of the various parts of the turbine is ensured by mounting on a shaft 50 (only shown in Figure 2). This has a frustoconical shoulder 51, which rests on the corresponding frustoconical internal annular surface 37 of the flange 30, passes through the hub 20 and projects beyond it by a threaded part 52.

A ring 53 is disposed on the plate 21 at the end of the hub opposite the flange 30, the ring 53 having a diameter sufficient to close the grooves 23. The mutual tightening of the plates 21, 31 and the flange 30 is ensured by a nut 55 engaged on the threaded part 52 and exerting a force on the ring 53 by means of another ring 56, the rings 53 and 56 being in mutual support by frustoconical surfaces.

Maintaining the flange 40 is provided simply by hooking on the heels 16 of the blades.

The attachment of the flange 40 to the blades may alternatively be carried out by gluing, with or without mechanical attachment of the heels of the blades in the notches of the flange. After bonding, it may be advantageous to carry out a cycle chemical vapor infiltration in order to densify the adhesive joint and establish a continuity of the matrix at the interfaces between the glued parts.

Still alternatively, and insofar as effective retention of the blades is ensured by their mounting on the hub and their insertion into the grooves of the flange 30, the flange 40 may be constituted by a static part, that is to say not linked in rotation to the rest of the turbine.

A turbine as illustrated in FIGS. 1 and 2 was produced from composite C-C having a diameter of 950 mm and a width, in the axial direction, of 250 mm. It was used to carry out a gas suction of a temperature of 1200 ° C at a rotation speed of 3000 rpm ensuring a flow rate of 130,000 m3 / h.

Compared to a metal turbine of the same dimensions, the mass gain is a ratio of about 5, that is to say about 40 kg for the C-C composite turbine against 200 kg for the metal turbine. The mass of the metal turbine means that its rotation speed cannot in practice exceed around 800 rpm.

Claims (12)

Method of manufacturing a turbine comprising a plurality of blades arranged around a hub, between two flanges, the blades, the hub and the flanges being made of thermostructural composite material, characterized in that: (a) the hub is produced by stacking, along the same axis, flat annular plates of thermostructural composite material, and immobilizing the plates in relation to each other in rotation about the axis, (b) each blade is produced individually by implementing the steps consisting in: - shaping an essentially two-dimensional fibrous texture into a plate or sheet, in order to obtain a blade preform, - densify the preform with a matrix to obtain a blade blank in thermostructural composite material, and - machine the contour of the densified preform, (c) each flange is produced by implementing the steps consisting in: - producing an annular or substantially annular preform by means of a substantially two-dimensional fibrous texture in plate or sheet, and - densify the preform with a matrix to obtain a part made of thermostructural composite material, and (d) the blades are assembled to the hub, between the flanges, each blade being connected to the hub by a part forming the blade root. Method according to claim 1, characterized in that each blade is connected to the hub by insertion of the blade root into a groove of corresponding shape made in the hub. Method according to any one of claims 1 and 2, characterized in that the preform of each blade is produced by shaping a fibrous prepreg texture. Method according to any one of claims 1 to 3, characterized in that a blade root is formed by placing an insert in a slot made in the fibrous texture used to make the preform of a blade. Method according to any one of claims 1 to 4, characterized in that the constituent plates of the hub are assembled with at least one annular plate constituting a first flange closing the passages between blades at one end of the turbine to which the blades by axial clamping on a shaft on which the turbine is mounted. A method according to claim 5, characterized in that the second flange, which provides with the hub an annular fluid entry zone for suction through the passages between blades, is mounted on the blades. A method according to claim 6, characterized in that the second flange has notches in which engage heels formed on the adjacent edges of the blades. Method according to either of Claims 6 and 7, characterized in that the second flange is glued to the adjacent edges of the blades. Turbine made of thermostructural composite material comprising a plurality of blades (10) arranged around a hub (20), between two flanges (30, 40), characterized in that it comprises flat annular plates (21) made of thermostructural composite material stacked along the same axis, immobilized with respect to each other in rotation about the axis and forming a hub (20), and the blades (10) made of thermostructural composite material are individually connected to the hub by a portion forming a blade root (13). Turbine according to claim 9, characterized in that said planar annular plates (21, 31, 30) of thermostructural composite material form an assembly comprising the hub (20) and a first flange (30) closing the passages between blades at one end of the turbine. Turbine according to any one of claims 9 and 10, characterized in that the second flange (40) which provides with the hub (20) an annular fluid entry zone for suction through the passages (11) between blades, is fixed on the blades. Turbine according to any one of claims 9 and 10, characterized in that the second flange which provides with the hub an annular fluid inlet zone for suction through the passages between blades, is static.

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