EP0761977B1 - High temperature composite material impellor, particularly of small diameter, and its manufacturing method - Google Patents

Description

The present invention relates to turbines, and more particularly those intended to operate at high temperatures, typically higher at 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 physico-chemical treatments at high temperatures, the ambient environment being example consisting of neutral or inert gases.

Usually, these turbines are made of metal, generally made up of several elements assembled by welding. We can however note GB 813 133-A which shows a set of two metal parts, one molded with a flange, a hub, and blades formed integrally with the flange, and the other molded in the form of a flange, the two parts being assembled by screw-nut at their axis.

The use of metal has several drawbacks. So the mass high rotating parts requires large shaft lines and very powerful engines and in any case imposes a speed limitation rotation. A temperature limitation is added due to the risk of creep of the metal.

In addition, the sensitivity of the metal to thermal shock can cause formation of cracks or deformations. 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 shock can occur, especially when injected massive cold gas, to quickly lower the temperature inside an oven to reduce the duration of treatment cycles.

In order to avoid problems with metals, other materials have already been proposed for making turbines, in particular materials thermostructural composites. 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 elements by their ability to maintain these properties up to temperatures high. Common examples of thermostructural composite materials are carbon-carbon composites (C-C) consisting of a fiber reinforcement carbon and a carbon matrix, and ceramic matrix composites (CMC) consisting of a carbon fiber or ceramic reinforcement and a matrix ceramic.

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

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

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

(a) on réalise une première pièce en une seule partie monobloc en matériau composite thermostructural formant un premier flasque et les pales en mettant en oeuvre les étapes consistant à :

• fabriquer une première préforme fibreuse sous forme de plaque ayant des dimensions externes choisies en fonction de celles de la première pièce à réaliser,
• densifier la première préforme fibreuse par une matrice de façon au moins partielle, de sorte que la préforme soit au moins consolidée, et
• usiner la première préforme fibreuse au moins partiellement densifiée pour lui donner la forme de la première pièce ;

(b) on réalise une deuxième pièce formant le deuxième flasque en une seule partie monobloc en matériau composite thermostructural par fabrication d'une deuxième préforme fibreuse, densification de celle-ci par une matrice, et usinage pour former le deuxième flasque, et

(c) on assemble la turbine en appliquant la deuxième pièce contre les pales de la première pièce.

According to one of its aspects, the subject of the present invention is a process for manufacturing a turbine comprising a plurality of blades arranged between two annular flanges and delimiting circulation passages between an inner ring and an outer ring, the blades and side plates being of thermostructural composite material, process according to which:

(a) a first part is produced in a single monobloc part made of thermostructural composite material forming a first flange and the blades by implementing the steps consisting in:

• manufacture a first fibrous preform in the form of a plate having external dimensions chosen as a function of those of the first part to be produced,
• densifying the first fibrous preform with a matrix at least partially, so that the preform is at least consolidated, and
• machining the first at least partially densified fiber preform to give it the shape of the first part;

(b) a second part is formed forming the second flange in a single monobloc part made of thermostructural composite material by manufacturing a second fibrous preform, densification of the latter by a matrix, and machining to form the second flange, and

(c) the turbine is assembled by applying the second part against the blades of the first part.

Thus, the turbine is for its essential part formed of only two pieces, which simplifies assembly, and each piece is made from a fibrous preform having a simple shape. This is so for the second piece, since it simply forms a flange, so that the second fibrous preform can be constituted by a plate. As for the first piece, it is produced by machining from a first preform constituted by a plate. Preferably, the first fibrous preform is machined in the consolidated state, partially densified, and densification by the matrix is continued after machining.

The machining of the first part leads to substantial losses of material, so that the present invention is more particularly suitable, although that not exclusively, for small diameter turbines. By small turbine diameter, here we mean a turbine whose diameter of the outer ring does not not exceed about 500 mm.

According to another advantageous feature of the process according to the invention, the turbine is assembled only by mutual tightening of the first room and the second room at their central parts. It was found that this single tightening ensures the assembly of the turbine in all configurations of operation, thanks to the rigidity of the composite material. This is all the more true that the diameter of the turbine is smaller. So there is no need to do use of screw type clamping elements penetrating the two parts. It's about an important advantage because, otherwise, the screws used should have been made of material composite, to withstand high temperatures and have a coefficient of expansion thermal compatible with that of the assembled parts, which would have increased the cost significantly.

The fibrous preforms are made using techniques known per se. So the first fiber preform, as well as the second, can be made from a flat stack of strata with a fibrous texture two-dimensional and bonding of the strata together by needling.

Alternatively, and because it must have a fairly large thickness, the first fibrous preform can be produced from a winding of a two-dimensional fibrous texture strip in superimposed layers and bonding of layers together by needling.

According to another of its aspects, the invention relates to a turbine which has a first and a second part, each made in one monobloc part, the first part forming a first flange and blades which delimit circulation passages between an inner ring and a outer crown, while the second piece forms a second flange applied against the blades of the first part, the first and the second part each being made of thermostructural composite material.

Advantageously, they are assembled only by tightening mutual at the level of their central parts.

• la figure 1 est une vue en coupe montrant une turbine conforme à l'invention montée sur un arbre ;
• la figure 2 est une vue en perspective montrant une première pièce constitutive de la turbine de la figure 1 ;
• la figure 3 est une vue en coupe partielle selon les plans III-III de la figure 2 ;
• la figure 4 montre des étapes successives d'élaboration d'une première pièce constitutive de la turbine de la figure 1 ;
• la figure 5 montre des étapes successives relatives à une variante de fabrication de préforme pour l'élaboration d'une première pièce constitutive de la turbine de la figure 1 ;
• la figure 6 montre des étapes successives d'élaboration d'une deuxième pièce constitutive de la turbine de la figure 1 ;
• la figure 7 est une vue en coupe montrant une variante de réalisation d'une turbine selon l'invention ; et
• la figure 8 est une vue en coupe montrant une autre variante de réalisation d'une turbine selon l'invention.

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 sectional view showing a turbine according to the invention mounted on a shaft;
• Figure 2 is a perspective view showing a first component of the turbine of Figure 1;
• Figure 3 is a partial sectional view along planes III-III of Figure 2;
• Figure 4 shows successive stages in the development of a first component part of the turbine of Figure 1;
• Figure 5 shows successive steps relating to a variant preform manufacturing for the development of a first component of the turbine of Figure 1;
• Figure 6 shows successive stages in the development of a second component part of the turbine of Figure 1;
• Figure 7 is a sectional view showing an alternative embodiment of a turbine according to the invention; and
• Figure 8 is a sectional view showing another alternative embodiment of a turbine according to the invention.

Figure 1 illustrates in section a turbine 10 comprising two parts monoblocks 20, 30 of thermostructural composite material assembled by clamping mutual on a shaft 12. The material of the parts 20 and 30 is for example a carbon-carbon composite material (C-C) or a composite material with ceramic matrix such as a C-SiC composite material (fiber reinforcement carbon and silicon carbide matrix).

The part 20 (Figures 1 to 3) comprises a plurality of blades 22 which are located on an internal face 24 a of an annular flange 24 in the form of a disc. The blades 22 extend between the outer circumference and the inner circumference of the flange 24, substantially perpendicular thereto. The heels 22 has blades 22 are connected to a central part forming a hub 26 whose internal diameter is substantially less than that of the flange 24. The hub 26 also has a thickness less than the length of the blades 22, and is spaced from the flange 24, along the axis A of the turbine, so that the external face 24 b of the flange, on the one hand, and the external face 26 b of the hub with the longitudinal edges 22 b of the blades 22, on the other hand, form the opposite faces of the part 20.

The part 30 constitutes an annular flange in the form of a disc, the outer diameter is equal to that of the flange 24 and whose inner diameter is equal to that of hub 26.

The part 30 is applied against the external face 26 b of the hub 26 and against the longitudinal edges 22 b of the blades 22. The mutual tightening of the parts 20 and 30 is carried out by blocking between a shoulder 12 a of the shaft 12 and a ring 14, by means of a nut 15.

The suction by the turbine is carried out from the space 16 which is located between the flange 24 and the hub 26, and is surrounded by the inner ring 17 of the turbine at the feet of the blades 22. The suction fluid is ejected through the outer ring 19 of the turbine at the blade ends 22, after circulation through the passages 18 delimited by the blades 22 and the flanges 24 and 30.

The rigidity of the thermostructural composite material means that the only clamping force at the central parts of parts 20 and 30 is sufficient to maintain assemblies, including during turbine operation, no detachment not observed. As already indicated, this is all the more true since the present invention applies preferably to small turbines diameter, that is to say an outside diameter not exceeding about 500 mm.

As shown in FIG. 1, the surfaces of the hub 26 and of the flange 30 on which the shoulder 12 a and the ring 14 are supported have a frustoconical shape, as do the corresponding faces of the shoulder 12 a and of the ring 14. These frustoconical bearing faces have substantially coincident vertices located on the axis A of the turbine. In this way, thermal expansion differences between, on the one hand, the parts 20 and 30 and, on the other hand, the shaft 12 and the ring 14, will result in a slip, without destructive effect.

Successive stages of a part 20 manufacturing process are shown in Figure 4. The part 20 is made from a structure fibrous plaque-shaped 200 (phase 41). Such a structure is manufactured by example by flat stacking of layers of two-dimensional fibrous texture, such as sheet of wires or cables, fabric, ..., and connection of the strata together by needling. A method of manufacturing such fibrous structures is described in document FR-A-2 584 106.

A first preform 201 of annular shape is cut in the plate 200, the dimensions of the preform 201 being chosen as a function of those of the part 20 to be produced (phase 42).

The preform 201 is subjected to a first densification step by the matrix of the thermostructural composite material to be produced (phase 43). Densification is made so as to consolidate the preform, that is to say to link between them the fibers of the preform sufficiently to allow handling and the machining of the consolidated preform. Densification is carried out in a known manner 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.

The consolidated preform is subjected to a first machining phase at during which the blades are formed from one face of the preform (phase 44), then to a second machining phase during which it is hollowed out in its center from the opposite side, so as to form the suction zone in leaving the hub part (phase 45).

The consolidated and machined preform 202 is then subjected to one or more several densification cycles until the desired degree of densification is obtained by the matrix (phase 46).

The preform thus finally densified is subjected to a final machining to bring it to the precise dimensions of part 20 (phase 47).

We have considered above the machining of the preform after consolidation and before complete densification, which favors final densification since this is more difficult to achieve homogeneously in structures thick fibrous. It is not however excluded to carry out the machining of the preform after complete densification.

According to another variant (FIG. 5), the preform of the part 20 is made from a cylindrical fibrous structure 200 'produced by winding a strip of two-dimensional fibrous texture in layers superimposed on a mandrel and bonding of the layers together by needling (phase 51). A method for manufacturing fibrous structures of this type is described in the document FR-A-2 584 107.

Preforms 201 'of annular shape are cut in the cylindrical structure 200 ′ along radial planes (phase 52).

Each preform 201 ′ is then treated in the same way as the preform 201 of FIG. 4.

As shown in Figure 6, the part 30 is made from a fibrous structure in the form of a plate 300. This structure is for example manufactured by flat stacking of layers of two-dimensional fibrous texture and connection of the strata together by needling (phase 61).

A preform 301 of annular shape is cut from the plate 300, the dimensions of the preform being chosen as a function of those of the part 30 to perform (phase 62).

The preform 301 is densified by the matrix, the densification being performed by chemical vapor or liquid infiltration (phase 63).

The densified preform is subjected to final machining in order to be brought at the dimensions of part 30 (phase 64).

Other embodiments of a turbine using two parts monoblocks of thermostructural composite material defining two flanges of the blades and a hub can be adopted.

The turbine 110 of FIG. 7 is formed essentially of two parts 120, 130 of thermostructural composite material. It is distinguished from the turbine of Figure 1 in that in the part 120, the blades 122 have a decreasing height between the inner ring 117 and the outer ring 119 of the turbine. This decreasing height compensates for the fact that the width of the passages 118 bordered by the blades 122 crosses between the inner ring and the outer ring, so that the inlet and outlet sections of the passages 118 are substantially equal.

The 130 applied against the flange part 120 has then a disk-shaped in its central part 130 has applied against the hub 126 and a frustoconical shape in its circumferential portion applied against the blades 122.

To make the flange 130, it is possible to start from a preform disc-shaped annular fibrous which is formed into the desired shape by means of of a tool, and consolidated by partial densification while being maintained in the tools. After consolidation, the preform can be removed from the tooling in order to continue densification.

As already indicated, the present invention applies more particularly turbines with relatively small diameters. The flow of the turbine can be increased or decreased, for a given diameter, by increasing or reducing the height of the passages, that is to say the thickness of the turbine. The loss of material during the machining of the blades being all the greater as their height is higher, it is preferable for cost reasons to limit the thickness of the turbine, for example by not exceeding about 100 mm.

A solution to increase the flow then consists in coupling two 10 ', 10 "turbines on the same axis as illustrated in Figure 8. Each turbine 10 ', 10 "includes two one-piece pieces of thermostructural composite material, a first part 20 ', 20 "forming blades 22', 22", flange 24 ', 24 "and hub 26', 26 ", and a second part 30 ', 30" forming a flange.

The turbine 10 ′ is similar to the turbine 10 in FIG. 1, while the 10 "turbine is distinguished by the arrangement of the blades. Indeed, the arrangement of the blades 22 "on the part 20" is symmetrical with respect to a radial plane of the arrangement of blades 22 'on part 20'. In this way, when the turbines 10 ', 10 " are joined by mutual contact between the external faces of the flanges 24 ', 24 ", the blades 22 ', 22 "define circulation passages oriented in the same way around the axis common to the turbines.

The parts 20 ', 30', 30 "and 20" are assembled by mutual tightening on a common shaft 12 'between a shoulder 12' a and a ring 14 ', by means of a nut 15'. The surfaces of the hubs 26 'and 26 "on which the shoulder 12' a and the ring 14 'rest have a frustoconical shape, as do the corresponding faces of the shoulder 12' a and of the ring 14 '. An additional ring 14 "of triangular section is interposed between the flanges 30 'and 30", the surfaces of these bearing on the ring 14 "having a frustoconical shape. The frustoconical bearing surfaces of the flange 30 'on the ring 14 "and of the hub 26' on the shoulder 12 ' a have substantially coincident vertices situated on the axis of the turbines, as do the bearing surfaces of the flange 30 "on the ring 14" and the hub 26 "on the ring 14 '. In this way, dimensional variations of thermal origin between the parts of the turbines, on the one hand, and the shaft and the clamping rings, on the other hand, can be compensated for by sliding parallel to the frustoconical bearing surfaces, in the same way as with the turbine 10 in FIG. 1.

Claims (16)

1. A method of manufacturing a turbine comprising a plurality of blades disposed between two end plates, the blades and the end plates being made of thermostructural composite material, in which:

   (a) a first part is made as a single one-piece part out of thermostructural composite material to constitute both a first end plate and the blades by implementing the following steps:

   a first fiber preform is fabricated in the form of a plate having outside dimensions that are selected as a function of the outside dimensions of the first part to be made;

   the first fiber preform is at least partially densified by a matrix so that the preform is at least consolidated; and

   the at least partially densified first fiber preform is machined to give it the shape of the first part;

   (b) a second part forming the second end plate is made as a single one-piece part out of thermostructural composite material by fabricating a second fiber preform, by densifying it with a matrix, and by machining it to form the second end plate; and

   (c) the turbine is assembled by applying the second part against the blades of the first part.
2. A method according to claim 1, characterised in that the first fiber preform is machined in the partially densified consolidated state, and matrix densification is continued after machining.
3. A method according to claim 1 or 2, characterised in that the machining of the first fiber preform in the form of an at least partially densified plate comprises making the blades by machining from one face of the plate and making a suction zone by hollowing out a central portion of the plate from the opposite face thereof, while leaving a central hub.
4. A method according to any one of claims 1 to 3, characterised in that the first fiber preform is made from a flat stack of plies of a two-dimensional fiber fabric with the plies being linked together by needling.
5. A method according to any one of claims 1 to 3, characterised in that the first fiber preform is made by rolling a strip of two-dimensional fiber fabric into superposed layers with the layers being linked together by needling.
6. A method according to any one of claims 1 to 5, characterised in that the second fiber preform is made from a flat stack of plies of a two-dimensional fiber fabric and the plies are linked together by needling.
7. A method according to any one of claims 1 to 6, characterised in that the turbine is assembled by clamping together the first part and the second part solely in the central portions thereof.
8. A turbine comprising a first part and a second part, each of the parts being made as a single one-piece part, the first part (20) forming both a first end plate (24) and the blades (22) defining flow passages between an inner ring (17) and an outer ring (19), while the second part forms the second end plate (30) which is applied against the blades (22) of the first part,
   characterized in that the first part and the second part are made of thermostructural composite material.
9. A turbine according to claim 8, characterised in that the first part (20) and the second part (30) are assembled to each other solely by clamping their central portions together.
10. A turbine according to claim 8 or 9, characterised in that, in the first part, the blades (22) extend between the outer circumference and the inner circumference on one side of a disk-shaped annular part forming the first end plate (24), and are connected, at their roots, to a hub-forming central portion (26).
11. A turbine according to claim 10, characterised in that the thickness of the hub-forming central portion (26) is smaller than the width of the blades (22).
12. A turbine according to claim 10 or 11, characterised in that, in the first part, the portion forming the annular end plate (24) and the portion forming the hub (26) occupy two opposite faces of the part.
13. A turbine according to any one of claims 10 to 12, characterised in that, in the first part, the hub-forming central portion (26) has an inside diameter that is smaller than that of the annular portion forming the end plate (24).
14. A turbine according to any one of claims 8 to 13, characterised in that the first and second parts (20, 30) are assembled together by clamping exerted against bearing surfaces belonging respectively to the first part and to the second part, located in the central portions thereof, said bearing surfaces being frustoconical in shape and having apexes that substantially coincide and are situated on the axis of the turbine.
15. A turbine according to any one of claims 8 to 14, characterised in that the height of the blades (22) tapers from the inner ring to the outer ring so as to define passages having outlet sections that are substantially equal to their inlet sections.
16. A turbine according to any one of claims 8 to 15, characterised in that it comprises a plurality of coaxial assemblies each comprising a first part (20', 20") and a second part (30', 30") assembled to one another solely by being clamped together via their central portions.

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