Collar for fastening a cooling tube of a turbomachine casing, the collar comprising a ring made of refractory material

Abstract

One aspect of the invention relates to a fastening collar (8) for fastening a cooling tube (2) of a cooling system of a turbomachine casing, the fastening collar (8) comprising a main body (10) having: a circular portion (16) configured to surround the cooling tube over at least part of its circumference, and two planar portions (19, 20) extending in the same plane (L, T), each arranged at one end of the circular portion. The fastening collar comprises a retaining ring (32) made of a refractory material, the retaining ring (32) being inserted into the main body and bearing against an internal surface of the circular portion. A second aspect of the invention relates to an assembly (4) for fastening a cooling tube, the assembly (4) comprising: a fastening support (6) secured to the turbomachine casing, a fastening collar (8) according to the invention, and a clamping device (46) for clamping the collar to the support.

Description

DESCRIPTION TITLE: SECURING COLLAR FOR A COOLING TUBE ON A TURBOMACHINE CRANKCASE, COMPRISING A RING MADE OF REFRACTORY MATERIAL. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of aircraft turbomachinery and, in particular, to the field of cooling turbomachine housings.

[0002] The present invention relates more particularly to a device for fixing a cooling tube of a cooling system of a turbomachine casing. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Typically, a cooling system is used to cool a turbomachine casing, such as a low-pressure turbine casing. The cooling system comprises a set of cooling tubes, usually metallic, also called cooling manifolds, arranged on the outside and around the periphery of the casing to ensure uniform cooling. The system is also equipped with one or more air supply boxes for the cooling tubes.

[0004] There are different types of cooling tube mounting kits.

[0005] In a commonly used type of mounting assembly, the cooling tubes are held in position around the periphery of the housing on mounting brackets attached to the housing by means of clamps, also known as shower clamps, each tightened onto a tube and secured to the mounting bracket. The mounting brackets are usually flat plates.

[0006] Figure 1 illustrates a prior art example of a fastening assembly 4 for a cooling tube 2 of a turbomachine housing cooling system. The fastening assembly 4 comprises a mounting bracket 6, a retaining collar 8, and a screw-nut type clamping device 46. The retaining collar 8 has a main body 10 comprising a circular portion 16 designed to clamp the cooling tube 2 over at least part of its circumference. The retaining collar 8 also has two flat portions 19, 20, each arranged at one end of the circular portion 16 and each having an opening 26 for receiving the clamping device 46. In the mounted position of the retaining collar 8 on the mounting bracket 6, the flat portions 19, 20 are arranged parallel to each other.The circular portion 16 of the main body 10 of the retaining collar 8 consists of a metallic layer 28 covered by a sheath 30 of a flexible material based on silica and polytetrafluoroethylene (Teflon). The sheath 30 is designed to protect the cooling tube 2 from any contact with the metallic layer 28 of the main body 10 of the retaining collar 8 in order to prevent its degradation by friction.

[0007] However, such a retaining collar 8 has certain drawbacks. During engine operation, the radiant heat emitted by the crankcase can reach the melting temperature of the polytetrafluoroethylene contained in the casing 30 of the retaining collar 8, causing the polytetrafluoroethylene to melt and the silica layer to degrade through abrasion. Once the silica layer is degraded, metal-on-metal friction occurs between the cooling tube 2 and the metal layer 28 of the retaining collar 8. This friction damages the cooling tube 2 and can lead to its perforation. A perforation in a cooling tube causes an air leak into the cooling system, reducing the system's cooling capacity and impairing the control of the turbine's radial clearances during operation, thus affecting engine performance.

[0008] Furthermore, a damaged cooling tube necessarily requires maintenance. This generally involves removing the engine for repair and replacing the damaged parts, which incurs additional costs. SUMMARY OF THE INVENTION

[0009] The invention offers a solution to the problems mentioned above, by proposing a fastening device configured to optimize the protection of the cooling tubes during engine operation and maintain the efficiency of the cooling system while limiting maintenance costs.

[0010] One aspect of the invention relates to a retaining collar for a cooling tube of a turbomachine casing cooling system, the retaining collar comprising a main body including: a circular portion configured to enclose the cooling tube along at least part of its circumference, and two flat portions extending along the same plane (L, T), each arranged at one end of the circular portion.

[0011] The fixing collar includes a retaining ring made of a refractory material housed inside the main body, bearing against an internal surface of the circular portion.

[0012] The retaining collar according to the invention ensures optimal positioning of the cooling tube within the collar. Furthermore, the presence of the graphite retaining ring improves the protection of the cooling tube against the various thermomechanical stresses to which it is exposed, thanks to the properties of the refractory material constituting said retaining ring.

[0013] In addition to the characteristics mentioned in the preceding paragraph, the fastening collar according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: the retaining ring has a transverse slot that extends across the entire width and thickness of the retaining ring; The refractory material of the retaining ring is graphite, carbon, or a composite based on a carbon matrix reinforced with carbon fibers; the refractory material of the retaining ring may also be pyrocarbon or a composite based on a ceramic matrix reinforced with carbon fibers. In the remainder of this description, the term "graphite" will be used to refer to graphite, carbon, carbon-based composite, pyrocarbon, ceramic-based composite, or any other refractory material or composite housed within the main body of the retaining collar; the two flat portions of the main body are arranged parallel to each other. the fixing collar has two circular stops, each arranged from a peripheral edge of the main body, on either side of at least part of the circular portion, and extending in a radial direction so as to keep the retaining ring inside the main body; each circular stop extends over approximately 75% of the circumference of the main body; Each flat portion of the main body has an opening designed to receive a clamping device in the mounted position of the fixing collar; the main body is made from a folded sheet of metal.

[0014] A second aspect of the invention relates to a fixing assembly for a cooling tube of a turbomachine casing cooling system comprising: a mounting bracket attached to the turbomachine housing, a fixing collar, and a clamping device for the fixing collar on the fixing support.

[0015] The fixing collar of the fixing assembly is a collar according to the first aspect of the invention. In the mounted position of the fixing collar on the fixing support, one of the two flat portions of the main body of the fixing collar is in contact with a face of the fixing support.

[0016] A third aspect of the invention relates to an aircraft turbomachine comprising: a turbomachine casing extending along an axial direction of the turbomachine, a cooling system comprising a plurality of cooling tubes, and at least one assembly for fixing a cooling tube according to the second aspect of the invention.

[0017] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0018] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which: Figure 1, already described, is a perspective view of a fixing assembly for a cooling tube of a turbomachine housing cooling system according to the prior art; Figure 2 is a perspective view of a fixing assembly for a cooling tube of a turbomachine housing cooling system according to the invention; Figure 3 is a perspective view of a fixing collar according to figure 2. DETAILED DESCRIPTION

[0019] An example of an embodiment of a fastening collar according to the invention is described in detail below, with reference to the accompanying drawings. This example illustrates the features and advantages of the invention.

[0020] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0021] Figure 2 illustrates a fixing assembly 4 of a cooling tube 2 of a cooling system of a turbomachine casing (not visible in the figure), in which the cooling tube 2 extends along a longitudinal axis L of a VLT frame.

[0022] The fastening assembly 4 according to the invention comprises: a mounting bracket 6, a retaining collar 8 for the cooling tube 2, and a clamping device 46 for the fixing collar 8 on the fixing support 6.

[0023] The mounting bracket 6 is integral with the turbomachine housing. The mounting bracket 6 is, for example, a preferably flat sheet metal plate extending along a plane defined by the longitudinal axis L and the transverse axis T.

[0024] The fixing collar 8 according to the invention, illustrated in isolation in figure 3, comprises a main body 10 and a retaining ring 32.

[0025] The main body 10 of the fixing collar is geometrically defined by a circular portion 16 and two flat portions 19, 20. The main body 10 comprises an internal surface 12 (i.e. the surface located along the inner circumference of the main body), an external surface 14 (i.e. the surface located along the outer circumference of the main body) and two peripheral edges 24 connecting the internal 12 and external 14 surfaces together.

[0026] The flat portions 19, 20 of the main body 10 are divided into an upper flat portion 19 and a lower flat portion 20 which extend parallel to each other along the plane defined by the longitudinal axis L and the transverse axis T. Each flat portion 19, 20 is arranged on either side of the circular portion 16 of the main body 10 and their internal surfaces 12 are opposite each other.

[0027] More specifically, the circular portion 16 of the main body 10 is delimited by a first and a second endpoint 17, 18 such that: the first end 17 is connected to the connecting portion 22, itself connected to the lower flat portion 20; indeed, the lower flat portion 20 extends into a connecting portion 22, preferably curved, connecting said lower flat portion to the first end 17 of the circular portion 16; and the second end 18 is connected to the upper portion 19.

[0028] Preferably, the main body 10 of the fixing collar 8 is made in one piece from a folded sheet of metal.

[0029] Each flat portion 19, 20 of the main body 10 has an opening 26 provided to receive the clamping device 46, when the fixing collar 8 is mounted on the fixing support 6.

[0030] The retaining ring 32, for example made of graphite (or another refractory material such as those mentioned above), advantageously by machining, is housed inside the main body 10, bearing against the inner surface 12 of the circular portion 16. The retaining ring 32 is configured to hold the cooling tube 2 in position inside the main body 10. The retaining ring 32 has an annular shape with a diameter complementary to that of the circular portion 16 of the main body 10 and whose width (along the longitudinal direction L) is substantially identical to that of the circular portion 16.

[0031] The retaining ring 32 has a transverse slot 38 extending across its entire width and thickness. The slot 38 forms an opening between a first and a second end 34, 36 of the retaining ring 32 so as to adapt the retaining ring 32 to the diameter of the cooling tube 2. By definition, the retaining ring 32 is a substantially annular strip of refractory material, having: a circumference suitable for at least partially enclosing the cooling tube 2, a width extending along the longitudinal direction L, and a thickness extending along a radial direction.

[0032] As can be seen in [Fig. 2] and [Fig. 3], the retaining ring 32, made of refractory material, is in direct contact with the cooling tube 2. It has a first surface and a second surface, the second being the face opposite the first. The first surface is in surface contact with the external surface of the cooling tube 2, while part of the second surface bears against an internal surface of the circular portion 16 of the main body of the retaining collar 8. Over a portion extending from the first end 17 of the main body 10 to the second end 18 of the main body, the retaining ring 32 is not in contact with any other element of the retaining assembly 4. This is also illustrated in [Fig. 2] and [Fig. 3].

[0033] In one embodiment, the retaining ring 32 clamps the cooling tube 2 over its entire circumference, over a portion of the length of said tube 2. In another embodiment visible in [Fig. 2] and [Fig. 3], the retaining ring 32 clamps the cooling tube 2 over its entire circumference except for the area where the transverse slot 38 is located.

[0034] The use of graphite, or other materials cited as examples of refractory materials, for the production of the retaining ring 32 offers several advantages thanks to the thermomechanical properties of this material. First, due to graphite's low hardness and self-lubricating properties, the retaining ring 32 has a high capacity for absorbing friction caused by engine vibrations during operation and, in combination with the slot 38, helps control the clearances between the cooling tube 2, the mounting bracket 6, and the turbomachine housing. Furthermore, graphite's high melting point gives the retaining ring 32 high resistance to the radiant heat emitted by the housing.Such a feature makes it possible to limit, or even eliminate, any possible contact between the cooling tube 2 and the main metallic body 10 of the fixing collar 8 and, thus, to optimize the protection of the cooling tube 2.

[0035] Finally, the mechanical strength and fatigue resistance of graphite (as defined above) are sufficiently high to ensure that the retaining ring 32 maintains its mechanical integrity in the portion where it is not in contact with another component of the mechanical assembly, even in environments where the retaining ring 32 is subjected to significant mechanical, thermal, chemical, and tribological stresses. The graphite retaining ring 32 thus offers an optimal combination of properties and good durability, which is not found in known solutions, particularly PTFE-based rings or collars, or metal collars, possibly coated with a protective silica layer. Specifically, it is capable of performing its functions up to an operating temperature of 600 °C.The graphite retaining ring 32 may not require surface treatment; it may be a single-material part that can be machined. In the context of the present invention, graphite has a Young's modulus particularly well-suited for use as a retaining ring 32.

[0036] According to a particular embodiment of the invention, the fixing collar 8 comprises two circular stops 40, each arranged from one of the two peripheral edges 24 of the main body 10, on either side of the circular portion 16. The circular stops 40 extend in a radial direction so as to prevent any translation of the retaining ring 32 inside the main body 10. The retaining ring 32 is thus held fitted into the main body 10.

[0037] According to some embodiments, each circular stop 40 extends over only a circumferential portion of the peripheral edge 24 of the main body 10, between a first and a second end 42, 44 of the circular stop 40. It extends, preferably, over 75% of the circumference of the main body, such a proportion being sufficient to ensure the retention of the retaining ring 32 along the main body.

[0038] Furthermore, according to a particular embodiment, the circular stop 40 is integral with the peripheral edge 24 of the main body 10, over the entire periphery of the circular stop 40.

[0039] Advantageously, each circular stop 40 is secured to a peripheral edge 24 by brazing.

[0040] According to a particular example of the arrangement of the retaining ring 32 in the main body 10 as shown in Figures 2 and 3, the ends 34, 36 of the retaining ring 32 are arranged opposite the upper flat portion 19 of the main body 10, for example opposite the junction of this flat portion with the second end 18 of the circular portion 16. In addition, the second end 36 of the retaining ring 32 can, for example, be aligned with the second end 44 of the circular stop 40.

[0041] Thus, when the fixing collar 8 is mounted on the fixing bracket 6 of the fixing assembly 4, illustrated in figure 2: the circular portion 16 of the main body 10 of the fixing collar 8 clamps the retaining ring 32 around the cooling tube 2 over at least part of the circumference of the tube, the external surface 14 of the upper flat portion 19 of the main body 10 is arranged parallel to the mounting support 6, against one face of said mounting support 6, the internal surfaces 12 of the lower and upper flat portions 19, 20 of the main body 10 are, at least in the vicinity of the orifice 26, in contact with each other, the clamping device 46 is received in the orifice 26 of each flat portion 19, 20 so as to hold the fixing collar 8 on the fixing support 6, in a locked position.

[0042] The retaining collar 8 according to the invention improves the protection of the cooling tube 2 at its interface with the retaining collar 8 during engine operation, thanks to the retaining ring 32, for example made of graphite. The protection is further improved when the graphite ring is slotted.

[0043] Better protection increases the lifespan of cooling tubes and limits costly engine maintenance interventions as well as the need to replace damaged cooling tubes.

Claims

DEMANDS

1. A retaining collar (8) for a cooling tube (4) of a turbomachine housing cooling system, the retaining collar (8) comprising a main body (10) having: - a circular portion (16) configured to enclose the cooling tube (2) over at least part of its circumference, and - two flat portions (19, 20) extending along the same plane (L, T), each arranged at one end of the circular portion (16); the fixing collar (8) being characterized in that it comprises a retaining ring (32) made of a refractory material, housed inside the main body (10) and bearing against an internal surface (12) of the circular portion (16), the refractory material of the retaining ring (32) being graphite, carbon, or a composite based on a carbon matrix reinforced with carbon fibers.

2. Fixing collar (8) according to claim 1, characterized in that the retaining ring (32) has a transverse slot (38) which extends over the entire width and thickness of the retaining ring (32).

3. Fixing collar (8) according to any one of the preceding claims, characterized in that the retaining ring (32) made of refractory material is produced by machining.

4. Fixing collar (8) according to any one of the preceding claims, characterized in that the retaining ring (32) made of refractory material is in direct contact with the cooling tube (2).

5. Fixing collar (8) according to any one of the preceding claims, characterized in that the two flat portions (19, 20) of the main body (10) are arranged parallel to each other.

6. Fixing collar (8) according to any one of the preceding claims, characterized in that it comprises two circular stops (40), each arranged from a peripheral edge (24) of the main body (10), on either side of at least a part of the circular portion (16), and extending in a radial direction so as to retain the retaining ring (32) inside the main body.

7. Fixing collar (8) according to claim 6, characterized in that each circular stop (40) extends over approximately 75% of the circumference of the main body (10).

8. Fixing collar (8) according to any one of the preceding claims, characterized in that each flat portion (19, 20) of the main body (10) has an orifice (26) provided to receive a clamping device (46) in the mounted position of the fixing collar (8).

9. Fixing collar (8) according to any one of the preceding claims, characterized in that the main body (10) is made from a folded sheet of metal.

10. A retaining collar (8) for a cooling tube (4) of a turbomachine housing cooling system, the retaining collar (8) comprising a main body (10) having: - a circular portion (16) configured to enclose the cooling tube (2) over at least part of its circumference, and - two flat portions (19, 20) extending along the same plane (L, T), each arranged at one end of the circular portion (16); the fixing collar (8) being characterized in that it comprises a retaining ring (32) made of a refractory material, housed inside the main body (10) and bearing against an internal surface (12) of the circular portion (16), the refractory material of the retaining ring (32) being graphite, carbon, pyrocarbon or a composite based on a carbon matrix or carbon fiber reinforced ceramic.

11. A mounting assembly (4) for a cooling tube (2) of a turbomachine housing cooling system comprising: - a mounting bracket (6) attached to the turbomachine housing, - a mounting collar (8), and - a clamping device (46) for the fixing collar (8) on the fixing support (6); the fixing assembly (4) being characterized in that the fixing collar (8) is a collar according to any one of the preceding claims, and in that, in the mounted position of the fixing collar (8) on the fixing support (6), one of the two flat portions (19, 20) of the main body (10) of the fixing collar (8) is in contact with one face of the fixing support (6).

12. Aircraft turbomachine comprising: - a turbomachine casing extending along an axial direction of the turbomachine, - a cooling system comprising a plurality of cooling tubes (2), and - at least one fixing assembly (4) for a cooling tube (2) according to claim 11.

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