Low-pressure turbine disc assembly equipped with a sealing splice

Abstract

Low-Pressure Turbine Disc Assembly Equipped with a Sealing Splice Plate. One aspect of the invention relates to a disc assembly (164) for a low-pressure turbomachine turbine (16), comprising: a first disc having a first upstream ferrule (161a) and a first downstream ferrule (161b), a second disc having a second upstream ferrule (161a) and a second downstream ferrule (161b), a movable ring (162) mounted between the first downstream ferrule and the second upstream ferrule, several bolted connections (163) mounted circumferentially at an inner end of the movable ring (162) to retain said movable ring with the first downstream ferrule (161b) and the second upstream ferrule (161a), and an annular sealing splice plate (170) enveloping the inner ends (161c, 162d) of the first downstream ferrule, the second upstream ferrule, and said movable ring, and fixed by means of bolted connections (163).Another aspect of the invention relates to a low-pressure turbine equipped with at least one such disc assembly. Figure to be published with the abbreviation: Figure 8.

Description

Title of the invention: Disc assembly for low pressure turbine equipped with a sealing joint TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a disk assembly for a turbomachine turbine, equipped with a sealing plate ensuring the seal between the disks and the movable ring to prevent air leaks between the internal cavity of the turbine and the air circulation vein.

[0002] The invention finds applications in the field of aircraft turbomachines and, in particular, in the field of inter-disc connections of low pressure turbines of turbomachines. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A turbomachine 10, an example of which is shown in [Fig.l], generally comprises several stages including a fan 11, a low-pressure compressor 12, a high-pressure compressor 13, a combustion chamber 14, a high-pressure turbine 15, a low-pressure turbine 16 and a nozzle 17. The turbomachine 10 is crossed by a primary air flow Fp circulating in a primary vein Vp and a secondary air flow Fs circulating in a secondary vein Vs, outside the primary vein.

[0004] [Fig. 2] represents an example of a low pressure turbine (called LP turbine) of the turbomachine 10. This LP turbine 16 extends around the axis of rotation XX of the turbomachine and comprises a distributor formed of a plurality of fixed blades 166 and a plurality of moving blades 165, mounted by their roots in cells 167 of disks 161 centered on the axis XX. The turbine disks 161 have the main functions of transmitting the torque of the turbine blades to the shaft of the LP turbine (not shown in the figure), of positioning the blades in the secondary flow path Vs and of ensuring the support of sealing parts such as the moving rings 162. An example of a turbine disk 161 is represented in [Fig. 3]. This disc 161, like all turbine discs, has an upstream shell 161a and a downstream shell 161b.The downstream ferrule 161b of a disc 161 is fixed to the upstream ferrule 161a of the consecutive disc 161 (i.e. of the following disc in the direction of flow of the air flow Fp) by means of a bolted connection 163. In particular, the end of each of the ferrules 161a, 161b forms a flange 161c crossed by the bolted connection 163, the flanges and the bolted connection ensuring the holding of two neighboring discs together.

[0005] A connecting ring 162, or movable ring, is disposed between the flanges 161c of the upstream 161a and downstream 161b ferrules. An example of a movable ring 162 is shown on [Fig.4]. This movable ring 162 has the main functions of ensuring the seal between the discs 161 thanks to coated lips 162a, in interface with the abradable fixed on the distributors opposite, of participating in the ventilation of the turbine 16 thanks to ventilation holes 162b and / or lunules 162c. This movable ring 162 comprises a flange 162d housed between the flanges 161c of the upstream 161a and downstream 161b shells and crossed by the bolted connection 163.

[0006] An example of a bolted connection 163 is shown in [Fig. 5]. This bolted connection 163 comprises a nut 163a and a screw 163b passing through a hole 163c formed in the flanges 161c of the upstream 161a and downstream 161b ferrules as well as a hole 163d formed in the flange 162d of the movable ring 162. Thus, each of the upstream 161a and downstream 161b ferrules comprises a ring of holes 163c and the movable ring 162 comprises a ring of holes 163d, these holes 163c, 163d being designed to be opposite each other and passed through by the screws 163b of the bolted connections 163.

[0007] When the turbine 16 is in operation, the bolted connections 163 are exposed to a high centrifugal load and the shells 161a, 161b of the discs 161 are exposed to significant bending stresses. In this configuration, plating defects of the shell flanges 161c and the movable ring flange 162d may appear, generating air leaks. To counter these plating defects, additional tightening operations of the bolted connections 163 have been implemented. However, these tightening operations require approximately 1.5 hours of additional labor in the assembly and maintenance phases, per engine, which results in a significant increase in the assembly cost and the maintenance cost. Furthermore, despite these additional tightening operations, leaks are not completely avoided, which has the effect of significantly reducing the service life of the turbine parts.

[0008] Indeed, to ensure proper operation of the turbine 16, it is essential that the turbine be sealed and that there is a balance between the so-called "fresh" air from the internal cavity Ci of the turbine (also called the upstream purge cavity) and the so-called "hot" air circulating in the primary vein Vp. As shown in [Fig.6], "fresh" air (whose temperature is of the order of 400 to 500°C) is generally taken from the HP compressor 13 in order to cool the disks 161 of the LP turbine and improve their service life. On the contrary, "hot" air (whose temperature is around 1000°C) circulates in the primary vein Vp. A purge of the internal cavity Ci is carried out by rejecting fresh air from the internal cavity Ci towards the primary vein Vp with an air flow, called the purge flow.

[0009] To allow this purging and prevent hot air from entering the internal cavity, the pressure of the “fresh” air in the internal cavity and the purge flow rate must be sufficiently high. However, if due to a plating defect, fresh air escapes from the cavity internal cavity Ci by the bolted connections 163, then the fresh air pressure inside the internal cavity Ci decreases, allowing the hot air from the primary stream Vp to rush into said internal cavity. By entering the internal cavity Ci, the hot air has the effect of heating the discs 161, which has a direct impact on their service life and can even cause the discs to rupture. A diagram shows, in [Fig.7], examples of air leak sections caused by a plating defect in a bolted connection, depending on the different flight phases of the turbomachine. Indeed, the more the turbine is stressed, for example with a high rotation speed, the more noticeable the plating defect is and the larger the air leak section.For example, during the aircraft take-off phase (phase 1), the leakage section can reach 12 mm2; during the aircraft climb phase (phase 2), the leakage section decreases compared to the take-off phase, while remaining high; during the cruise phase (phase 3), the leakage section decreases until it becomes almost zero; and during the aircraft descent or landing phase (phase 4), the leakage section increases again, for example to approximately 4 mm2, until the turbine stops.

[0010] There is therefore a real need for a device making it possible to overcome plating defects in the ferrule and movable ring flanges in order to significantly reduce the leakage section and even eliminate it. Summary of the invention

[0011] To address the above-mentioned problems of air leaks caused by plating defects, the applicant proposes installing a sealing fishplate surrounding the ends of the ferrule and movable ring flanges and fixed by the bolted connections.

[0012] In the description, the term “exterior” designates the surfaces or parts of parts located furthest from the axis of rotation XX of the turbomachine, as opposed to the term “interior” which designates the surfaces and parts of parts closest to said axis XX.

[0013] Furthermore, the terms “upstream” and “downstream” are understood according to the direction of air flow, from the fan of the turbomachine towards the nozzle.

[0014] According to a first aspect, the invention relates to a disk assembly for a turbomachine turbine, comprising: • a first disc comprising a first upstream ferrule and a first downstream ferrule, • a second disc comprising a second upstream ferrule and a second downstream ferrule, • a movable ring mounted between the first downstream shell and the second upstream shell, and • several bolted connections mounted circumferentially at an internal end of the movable ring to hold said movable ring with the first downstream shell and the second upstream shell, characterized in that it further comprises an annular sealing fishplate, surrounding the internal ends of the first downstream shell, the second upstream shell and said movable ring and fixed by means of bolted connections.

[0015] The sealing fishplate makes it possible to keep the movable ring and the first and second discs pressed against each other, not only at the bolted connections but also between two bolted connections, so as to avoid plating defects and, thus, limit air leaks and maintain the purge flow rate sufficiently high.

[0016] In addition to the characteristics which have just been mentioned in the preceding paragraph, the assembly of discs according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the sealing joint comprises several identical sealing segments, overlapping each other. • each sealing segment comprises two curved lateral portions, connected by a convex central portion, the central portion comprising a bulge enveloping a scalloped area, the lateral portions enveloping inter-scalloped areas. • the central portion of each sealing segment has a through opening designed to receive a screw for fixing the bolted connection. • each sealing segment has a U-shaped section. • each sealing segment has two end portions, of thinned thicknesses, each adapted to fit into an end portion of a neighboring sealing segment. • the end portions designed to overlap have a circumferential length less than or equal to an inter-scallop distance. • at least one sealing segment has a hole positioned in the vicinity of a lunule of the movable ring. • the sealing strip is made from folded sheet metal.

[0017] A second aspect of the invention relates to a low-pressure turbine of a turbomachine, comprising several discs and several movable rings, each movable ring being mounted between two consecutive discs and fixed to said consecutive discs by means of bolted connections. The turbine comprises several disc assemblies according to the first aspect of the invention, the number of disc assemblies being equal to the number of movable rings.

[0018] A third aspect of the invention relates to a turbomachine comprising a low pressure turbine equipped with several disk assemblies according to the first aspect of the invention. BRIEF DESCRIPTION OF THE FIGURES

[0019] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0020] [Fig.l], already described, represents a schematic view in longitudinal section of a turbomachine according to the state of the art;

[0021] [Fig. 2], already described, represents a schematic view in longitudinal section of a part of a LP turbine according to the state of the art;

[0022] [Fig. 3], already described, represents a schematic perspective view of a part of a turbine disc according to the state of the art;

[0023] [Fig. 4], already described, represents a schematic perspective view of a part of a moving ring of a turbine according to the state of the art;

[0024] [Fig. 5], already described, represents a schematic view in longitudinal section of a bolted connection of a turbine disk according to the state of the art;

[0025] [Fig. 6], already described, represents a schematic view in longitudinal section of the internal cavity of a LP turbine according to the state of the art;

[0026] [Fig. 7], already described, represents a diagram showing, as a function of the flight phase of a turbomachine, the leakage section generated by a plating defect of a bolted connection according to the state of the art;

[0027] [Fig.8] represents a schematic view in longitudinal section of a bolted connection equipped with a sealing fishplate according to the invention;

[0028] [Fig.9] shows perspective and sectional views of a sealing fishplate portion for a disc assembly according to the invention;

[0029] [Fig. 10] shows perspective and sectional views of a sealing fishplate portion for disc assembly according to one embodiment of the invention; and

[0030] [Fig. 11] shows a partial perspective view of two discs and a movable ring assembled by means of a bolted connection equipped with a sealing fishplate according to the invention.

[0031] In the figures, identical elements are identified by identical references. For reasons of readability of the figures, the size scales between elements represented are not respected. DETAILED DESCRIPTION

[0032] An exemplary embodiment of an LP turbine disk assembly equipped with a sealing joint according to the invention is described in detail below, with reference to attached drawings. This example illustrates the characteristics and advantages of the invention. It is however recalled that the invention is not limited to this example.

[0033] An example of a bolted connection of an LP turbine equipped with a sealing joint according to the invention is shown in [Fig. 8]. An assembly of discs 164 of an LP turbine 16 comprises several identical bolted connections 163 distributed over the circumference of the assembly 164 and in particular the circumference of the discs 161. The number of bolted connections may, for example, be 54.

[0034] Each bolted connection 163 comprises a screw 163b passing through a hole 163c formed in the flanges 161c of the disc ferrules and a hole 163d formed in the flange 162d of the movable ring 162. The hole 163d of the movable ring flange is positioned between the two holes 163c of the downstream ferrule 161b and the upstream ferrule 161a. The holes 163c of the disc ferrule flanges 161c and the hole 163d of the movable ring flange are called "festoons". The screw 163b therefore passes through the festoons of each of the flanges. The areas of the assembly 164 where the scallops 163c of the ferrules and the scallops 163d of the movable ring are called "scallop areas" and referenced 164c.

[0035] Each bolted connection 163 also comprises a nut 163a screwed onto the end of the screw 163b; the head of the screw 163b ensures, for example by its square or rectangular shape, the anti-rotation of the bolted connection 163. Thus the screw 163b is positioned, for example, upstream of the disk assembly 164, that is to say in the vicinity of the downstream shell 161b of a first disk, while the nut 163a is positioned downstream of the disk assembly 164, that is to say in the vicinity of the upstream shell of a second disk, consecutive to the first disk and positioned downstream of the first disk according to the direction of circulation of the air in the turbine. Of course, the positions of the screw 163b and the nut 163a can be reversed, with the screw downstream of the disc assembly 164 and the nut upstream of said assembly 164.

[0036] The bolted connection 163 of [Fig. 8] is equipped with a sealing fishplate 170 according to the invention. This sealing fishplate 170 is a part, for example metallic, whose section has a U shape. It is preferably made of folded sheet metal. This sealing splint 170 extends over the entire circumference of the disc assembly 164, at the inner end of the flanges 161c of the disc ferrules 161 and the flange 162d of the movable ring 162. In other words, the sealing splint 170 is annular and envelops the discs 161 and the movable ring 162 in their joint end zone 164a, that is to say the zone where the flanges 161c of the disc ferrules and the flange 162d of the movable ring are positioned against each other. Thus, the sealing splint 170 follows the contour of the disc assembly 164 in its inner end zone.For this, the sealing fishplate 170 surrounds not only the joining portion of the flange 162d of the movable ring and the flanges 161c of the ferrules 161a, 161b but also the scalloped areas 164c at the connections. bolted 163.

[0037] A sealing splint 170 is formed from several sealing segments 170a, 170b mounted one after the other to form a sort of ring. An example of a segment 170a of a sealing splint 170 is shown in [Fig. 9]. Drawing A of [Fig. 9] shows a profile view of a sealing segment 170a and drawing B of [Fig. 9] shows a front view of two sealing segments 170a, 170b mounted one after the other.

[0038] Each sealing segment 170a comprises two curved lateral portions 171, 172 connected by a convex central portion 175. The lateral portions 171, 172 have a curvature substantially similar to that of the internal end of the disc assembly 164 so as to match the rounded shape of a portion of the joint end zone 164a of the assembly 164. Each lateral portion 171, 172 ends with an end portion, respectively, 173 and 174, the thickness of which is thinned compared to the thickness of the rest of the sealing segment so as to allow the two end portions to fit into each other and, thus, allow said two end portions 173, 174 to overlap.One of the end portions of the sealing segment 170a, for example the end portion 173, is thinned by removing material from the outer surface of said end portion; the other end portion of the sealing segment 170a, for example the end portion 174, is thinned by removing material from the inner surface of said end portion. Thus, the end portion 173 is able to fit into the end portion 174 so that the two end portions 173, 174 overlap each other. The length of the end portions overlapping each other is dimensioned so as to envelop all of the areas having a plating defect.

[0039] The convex central portion 175, simply called the central portion, has a convex curvature substantially similar to the curvature of the assembly 164 around the scalloped area 164c. This central portion 175 forms a bulge relative to the lateral portions 171, 172, that is to say that it has a height hl greater than the height h2 of said lateral portions, the heights hl and h2 being the measurements of a leg of the U-shaped section determined along the radial direction of the LP turbine.

[0040] In other words, each sealing segment 170a, 170b has a so-called “inverted gendarme hat” shape with a central portion 175 designed to surround a scalloped area 164c of the assembly 164 and lateral portions 171, 172 designed to surround an inter-scalloped area 164b. Thus, when the sealing fishplate 170 is mounted on the assembly 164, each scalloped area 164c is surrounded by the central portion 175 of a sealing segment 170a and each inter-scalloped area 164b is surrounded partly by the lateral portion 171 of a sealing segment and partly by the lateral portion 172 of a neighboring sealing segment, the end portions 173, 174 of the two neighboring sealing segments 170a, 170b overlapping each other. The overlapping end portions 173, 174 then have a circumferential length equal to or less than the length of the inter-festoon zone 164b.

[0041] Each sealing segment 170a has an arcuate shape whose length L is equal to the distance between two inter-festoon zones 164b, which corresponds to the distance between two neighboring festoon zones 164c. Each sealing segment 170a is fixed to the disc assembly 164 by a bolted connection 163. The sealing fishplate 170 therefore comprises as many sealing segments 170a, 170b as there are bolted connections 163. To ensure the fixing of the sealing segment to the assembly 164, each sealing segment 170a comprises a through opening 176 designed to receive the screw 163b of the bolted connection 163.The through opening 176 is an orifice made in each of the walls 178 forming the U-shaped section of the sealing segment; one of the orifices forming the through opening 176 is therefore opposite the hole 163c of the flange 161c of the downstream ferrule 161b and the other orifice forming the through opening 176 is opposite the hole 163c of the flange 161c of the upstream ferrule 161a. The screw 163b of the bolted connection 163 therefore passes through the through opening 176 and the scalloped zone 164c; the nut 163a of the bolted connection 163 is mounted at the free end of this screw 163b to ensure anti-rotation of said screw and the fixing of the sealing segment 170a on the disc assembly 164.

[0042] In some LP turbines, the movable ring 162 may be provided with lunules participating in the cooling of the disks of the LP turbine. The lunules are grooves, or windows, made in the flange 162d of the movable ring 162 to allow fresh air to pass through and ensure the cooling of a portion of the disks 161. An example of lunules 162c is shown in [Fig. 4] of the prior art, the lunules of the disk assembly 164 according to the invention being similar to the lunules 162c of [Fig. 4],

[0043] When the movable ring 162 comprises lunules, the sealing fishplate 170 may comprise one or more holes 177 each positioned in the vicinity of a lunule. [Fig. 10] represents an example of a sealing segment 170a equipped with such a hole 177. Drawing A of [Fig. 10] shows a hole 177 made in the lateral portion 172 of the sealing segment 170a. Drawing B of [Fig. 10] represents a front view of two sealing segments 170a, 170b mounted one after the other with a hole 177 made in their lateral portions 171, 172. Those skilled in the art will understand that one or more holes may be made in the lateral portion 171 and / or 172 of the sealing segment. The number and location of the 177 holes are directly dependent on the number and the location of the lunules in the movable ring; the holes should not hinder the passage of air through the lunules, they are preferably offset radially relative to the lunules.

[0044] An example of a disc assembly 164 equipped with a sealing splint 170 according to the invention is shown in drawing B of [Fig.l 1], in comparison with a disc assembly according to the state of the art shown in drawing A of [Fig.l 1]. This comparison of the two disc assemblies makes it possible to understand that the sealing splint 170 is easily inserted onto a conventional disc assembly, without any modification of the discs 161, the movable ring 162 or the bolted connections 163. The sealing splint 170 is simply mounted, segment by segment, around the joint end zones of the discs and the movable ring and fixed, also segment by segment, using the original bolted connections.

[0045] Whatever the embodiment (with or without a hole), the sealing fishplate 170, formed from the plurality of sealing segments 170a, 170b overlapping one another, makes it possible to limit the inter-flange leakage sections of the disk assembly and to very significantly reduce the leaks caused by plating defects, which also makes it possible to improve the performance of the LP turbine. The sealing fishplate also makes it possible to save time during assembly and maintenance by avoiding additional tightening operations and / or plating defect checks.

[0046] Although described through a number of examples, variations and embodiments, the LP turbine disc assembly includes various variations, modifications and improvements which will be apparent to those skilled in the art, it being understood that these variations, modifications and improvements are within the scope of the invention.

Claims

Claims

1. Disk assembly (164) for a low-pressure turbine (16) of a turbomachine, comprising: - a first disk comprising a first upstream shell (161a) and a first downstream shell (161b), - a second disk comprising a second upstream shell (161a) and a second downstream shell (161b), - a movable ring (162) mounted between the first downstream shell and the second upstream shell, and - several bolted connections (163) mounted circumferentially at an inner end of the movable ring (162) to hold said movable ring with the first downstream shell (161b) and the second upstream shell (161a), characterized in that it further comprises an annular sealing fishplate (170) surrounding the inner ends (161c, 162d) of the first downstream shell, the second upstream shell and said ring mobile and fixed by means of bolted connections (163).

2. Assembly according to claim 1, characterized in that the sealing splint (170) comprises several identical sealing segments (170a, 170b), overlapping each other.

3. Assembly according to claim 2, characterized in that each sealing segment (170a, 170b) comprises two curved lateral portions (171, 172), connected by a convex central portion (175), the central portion comprising a bulge enveloping a scalloped zone (164c), the lateral portions enveloping inter-scalloped zones (164b).

4. Assembly according to claim 3, characterized in that the central portion of each sealing segment (170a, 170b) comprises a through opening (176) designed to receive a fixing screw (163b) of the bolted connection (163).

5. Assembly according to any one of claims 2 to 4, characterized in that each sealing segment (170a, 170b) has a U-shaped section.

6. Assembly according to any one of claims 2 to 5, characterized in that each sealing segment (170a, 170b) comprises two end portions (173, 174), of thinned thicknesses, adapted to each fit into an end portion of a neighboring sealing segment.

7. Assembly according to claim 6, characterized in that the end portions (173, 174) designed to overlap have a circumferential length less than or equal to an interfestoon distance.

8. Assembly according to any one of claims 2 to 7, characterized in that at least one sealing segment (170a, 170b) comprises a hole (177) positioned in the vicinity of a lunule of the movable ring (162).

9. Assembly according to any one of claims 1 to 8, characterized in that the sealing fishplate (170) is manufactured from folded sheet metal.

10. Low pressure turbine (16) of a turbomachine, comprising several discs (161) and several movable rings (162), each movable ring being mounted between two consecutive discs and fixed to said consecutive discs by means of bolted connections (163), characterized in that it comprises several disc assemblies (164) according to any one of claims 1 to 9, the number of disc assemblies (164) being equal to the number of movable rings (162).

11. A turbomachine comprising a low pressure turbine (16) equipped with several disc assemblies (164) according to any one of claims 1 to 9.

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