LOW PRESSURE TURBINE ROTOR DISC HEAD AND INTER-DISC SEAL SYSTEM FOR LOW PRESSURE TURBINE ROTOR DISCS

Abstract

LOW PRESSURE TURBINE ROTOR DISC HEAD AND LOW PRESSURE TURBINE ROTOR DISC INTER-DISC SEAL SYSTEM Low pressure turbine rotor disc head (300) of a turbomachine, said turbine having an axis of rotation X, said disc head (300): Extending axially in a direction parallel to the axis X between an upstream face (301) and a downstream face (302) opposite the upstream face (301); Comprising an upstream flap (303), said upstream flap (303) comprising an upstream flap body (303.1) extending axially from the upstream face (301) and a downstream flap (305), said downstream flap comprising a downstream flap body (305.1) extending axially from the downstream face (302). Figure to be published with the abbreviation: Figure 3

Description

Title of the invention: LOW PRESSURE TURBINE ROTOR DISC HEAD AND SEALING SYSTEM INTER LOW PRESSURE TURBINE ROTOR DISCS TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of aeronautics and particularly to the field of inter-rotor disc sealing systems for low-pressure turbines of aircraft turbomachines.

[0002] The invention relates to a low pressure turbine rotor disc head. The invention further relates to a low pressure turbine rotor disc inter-disc sealing system. Another subject of the invention is a method of mounting an axial blade root retention ring of a rotor disc comprising a disc head according to one aspect of the invention. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] An aeronautical turbomachine conventionally comprises a compressor, a combustion chamber and a turbine. The role of the turbine is to ensure the rotational drive of the compressor by taking part of the pressure energy from the hot gases leaving the combustion chamber and transforming it into mechanical energy.

[0004] A compressor consists of a rotating part, a rotor comprising an axis of rotation, a fixed part, the stator, and a casing, the casing and the stator being integral with each other. The rotor comprises a drum consisting of an assembly of several discs on which rotating blades are circumferentially fixed. The stator consists of a plurality of fixed blades (because they do not rotate around the axis of rotation of the rotor but can be mobile in rotation along their own axis) fixed circumferentially on the casing or on shells. Each row of fixed blades of the stator, called rectifiers, constitutes a rectifier or distributor. A row of moving blades and a row of fixed blades form a compressor stage.

[0005] In order to ensure engine performance and extend the life of the limiting zones on the discs, technologies aim to reduce leaks between the air stream and the cavity under the disc. Such leaks can damage the discs, in particular because of the high temperatures of the air flowing in the stream.

[0006] [Fig.l] illustrates a low-pressure turbine rotor disc inter-disc sealing system 1 according to the state of the art. A bolted connection 11 secures in rotation an upstream rotor disc 12 and a downstream rotor disc 13. A rotating movable ring 14 is fixed between the upstream disc 12 and the downstream disc 13 so as to isolate the bolted connection 11 from the air stream. The rotor discs 12, 13 allow, by cooperating with the blades 15, to recover the energy of the fluid flowing in the air stream by transforming it into mechanical energy.

[0007] Retaining rings, respectively upstream 16 and downstream 17, are used to axially retain the blades which are pushed by the fluid towards the rear of the turbine.

[0008] The low pressure distributor 18, a fixed part between the blades 15, serves to accelerate the fluid throughout the turbine. The low pressure distributor also ensures sealing between the fixed parts (stator) and the rotating parts (rotor) by the interface between an abradable 19 and the wipers 20 of the movable ring 14.

[0009] The movable rings 14 lock the retaining rings 16, 17 in the fasteners. In addition, these rings regulate the pressure difference between the air coming from the vein (hot) and the air coming from the cavity under the disc (cold).

[0010] The abradable 19 is in contact with the lips 20 of the movable ring 14, which ensures the sealing of the part below the movable disc 14.

[0011] However, the sealing system 1 according to the state of the art does not allow the service life of several elements such as holes and festoons on the upstream and downstream flanges 21 of the discs to be sufficiently extended. Indeed, this service life is impacted by: • thermal leaks between the upstream and downstream arms of the movable ring 14 and the retaining rings 16 and 17; • Significant mechanical stresses in the bolted connection 11.

[0012] [Fig. 2] illustrates how some of these phenomena manifest themselves in a state-of-the-art device such as the sealing system 1 illustrated with reference to [Fig. 1].

[0013] In operation, the upstream and downstream arms of the movable ring 14 deform radially towards the vein and no longer ensure their sealing functions at the rims and the retaining rings. This deformation is illustrated schematically by the arrow 210.

[0014] The holes and festoons are stressed by the thermal gradient between the movable ring 14 (heated by the hot air 211 coming from the vein) and the bolted connection (air coming from the cavity under the discs) and by the centrifugal force 212 undergone by the movable ring.

[0015] This hot air coming from the vein heats the bolted connection and the disc ferrules, thus creating additional stress 213 in these areas.

[0016] In addition, the upward deformation 212 of the ring 14 adds traction to the flanges 21 and bending to the ferrules 22.

[0017] There is currently no sealing system for low pressure turbines that can reduce the various thermomechanical deformations of the parts of the turbine and therefore extend their lifespan. Summary of the invention

[0018] The invention provides a solution to the problems mentioned above by proposing an improved disc head and sealing system.

[0019] A first aspect of the invention relates to a low pressure turbine rotor disk head of a turbomachine, said turbine having an axis of rotation X, said disk head: - Extending axially in a direction parallel to the X axis between an upstream face and a downstream face opposite the upstream face; - Comprising an upstream lip, said upstream lip comprising: • An upstream wiper body extending axially from the upstream face and • An upstream rim extending radially from the upstream wiper body and forming an upstream groove with the upstream face of the disc head; - Comprising a downstream lip, said downstream lip comprising: • A downstream wiper body extending axially from the downstream face and • A downstream rim extending radially from the downstream wiper body and forming a downstream groove with the downstream face of the disc head.

[0020] In the description, the terms “upstream” and “downstream” are defined in relation to the direction of air flow from the air inlet into the turbomachine to the air outlet from the turbomachine.

[0021] The term radial refers to a direction normal to the axis of rotation X of the low pressure turbine.

[0022] The upstream groove and the downstream groove make it possible to house axial blade root retaining rings. It is therefore possible to replace the movable rings used in known systems which are responsible for significant thermomechanical stresses. In other words, a disc head according to the first aspect of the invention makes it possible to reduce thermomechanical stresses and therefore to extend the service life of the parts of a low-pressure turbine.

[0023] According to one embodiment, the upstream wiper and the downstream wiper comprise a coating comprising a nickel-carbon alloy mixture. This material is a coating applied by plasma deposition and has the function of degrading according to the wear of the engine and of adjusting in the abradable.

[0024] A second aspect of the invention relates to a low pressure turbine rotor inter-disc sealing system, said sealing system comprising: • An upstream disk head according to the first aspect of the invention; • A low pressure distributor foot, said distributor foot comprising: - An abradable support extending axially between an upstream face support and a downstream support face opposite the upstream support face; - An upstream abradable extending axially between the upstream support face and an upstream abradable surface opposite the upstream support face; - A downstream abradable extending axially between the downstream support face and a downstream abradable surface opposite the downstream support face; • A downstream disk head according to the first aspect of the invention;

[0025] In which: - The downstream wiper body of the upstream disc head is in contact with the upstream abradable surface of the low pressure stator distributor foot; - The upstream wiper body of the downstream disc head is in contact with the downstream abradable surface of the low pressure distributor foot.

[0026] The sealing system according to the second aspect of the invention makes it possible to reduce the stress in the areas with limiting life, such as holes, scallops or ferrules, while maintaining engine performance. In particular, the sealing system according to the second aspect of the invention makes it possible to obtain sealing between the air stream and the cavities under the discs while reducing the traction of the bolted connection.

[0027] Thanks to the contact between the axially extending wipers and the abradables, respectively upstream and downstream, positioned on the low pressure distributor, it is possible to obtain the sealing necessary to protect certain parts of the turbine from the hot air flowing in the air stream.

[0028] In other words, the sealing system according to the second aspect of the invention makes it possible to obtain axial sealing eliminating contact between the hot air circulating in the main air stream and certain parts of the low pressure turbine such as the inter-disc bolted connections.

[0029] By modifying the rotor disc head and modifying the abradable support, it is possible to achieve sealing of the inter-disc region without using movable rings as in systems according to the state of the art. This makes it possible to reduce thermomechanical stresses and in particular the upward traction of the bolted connection.

[0030] Among the technical effects linked to the installation of a disk head according to the invention, it is possible to cite: - Reduction of leaks from the vein and improvement of the thermal gradient in the bolted connections with a reduction of the mechanical stress in the disc flanges; - Reduction of the upward bolted connection traction with a reduction of the local stress; Reducing the rotor mass, for example by eliminating the moving inter-disc rings.

[0031] Other advantages obtained by implementing a disk head according to the first aspect of the invention are: A simplification of the low pressure turbine and a financial gain by eliminating the material and machining of the moving rings; A reduction in stress in the flanges leading to a gain in service life in these areas; A turbine disc operability margin corresponding to a gain in service life. This gain makes it possible to increase gas temperatures without reducing the declared service life potential.

[0032] According to one embodiment, the upstream abradable and the downstream abradable comprise a material having a honeycomb structure formed by a multiplicity of adjacent cells.

[0033] A third aspect of the invention relates to a method for mounting an axial retention ring for blade roots of a rotor disk of a low-pressure turbine of a turbomachine comprising a disk head according to the first aspect of the invention, said method comprising the following steps: Introduction of the axial retention ring into the downstream groove of the disc head; Introduction of a moving blade comprising a blade hook into the disc head, so as to position the blade hook opposite the downstream groove of the disc; Radial displacement of the axial retaining ring so as to house it at least partially in the blade hook.

[0034] The method according to the third aspect of the invention makes it possible to mount the axial retention rings of blade roots on a disc head according to the first aspect of the invention.

[0035] According to one embodiment, the displacement of the axial retention ring is carried out after having positioned all the blades in the rotor disk.

[0036] According to one embodiment, the radial displacement of the ring is carried out using a tool.

[0037] The invention and its various applications will be better understood upon reading the description which follows and the examination of the figures which accompany it. BRIEF DESCRIPTION OF THE FIGURES

[0038] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0039] [Fig.l] schematically illustrates a sealing system according to the state of the art;

[0040] [Fig.2] schematically illustrates the thermomechanical and local constraints in a system such as that illustrated in [Fig.l];

[0041] [Fig.3] illustrates an example of a disk head according to a first aspect of the invention;

[0042] [Fig.4] schematically illustrates an embodiment of a stator foot used in a sealing system according to the invention;

[0043] [Fig.5] illustrates an embodiment of a sealing system according to a second aspect of the invention;

[0044] [Fig.6] illustrates a flowchart of an embodiment of a method of mounting an axial retention ring according to a third aspect of the invention.

[0045] [Fig.7] schematically illustrates the carrying out of certain steps of an embodiment of the method of mounting an axial retention ring according to the third aspect of the invention. DETAILED DESCRIPTION

[0046] Figures 1 and 2 have been described in relation to the state of the art.

[0047] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0048] For the understanding of the invention, the radial R, tangential T and axial A orientations will be adopted according to the reference RTA indicated in the figures, the tangent T and axial A axes of which extend in a horizontal plane according to the orientation in the figures. The axial axis A is parallel to an axis of rotation X of an aircraft turbomachine comprising the anti-icing system according to the first aspect of the invention.

[0049] [Fig. 3] illustrates an embodiment of a disk head 300 of a rotor disk of a low pressure turbine according to one aspect of the invention.

[0050] The disc head 300 extends axially between an upstream face 301 and a downstream face 302 opposite the upstream face. The disc head 300 comprises a cell (not referenced in the figure) intended to accommodate a blade root (not shown in the figure).

[0051] The disk head 300 comprises, as illustrated in [Fig. 3], an upstream wiper 303. The upstream wiper 303 comprises an upstream wiper body 303.1 and an upstream rim 303.2. The upstream wiper body 303.1 extends axially from the upstream face 301. The upstream rim 303.2 extends radially from the upstream wiper body 303.1.

[0052] The upstream rim 303.2 forms with the upstream face 301 an upstream groove 304. The upstream groove 304 is intended to accommodate an upstream axial retention ring 307.

[0053] Similarly, the disk head 303 includes a downstream wiper 305. The Downstream wiper 305 comprises a downstream wiper body 305.1 extending axially from the downstream face 302 and a downstream rim 305.2 extending radially from the downstream wiper body 305.1.

[0054] The downstream rim 305.2 forms with the downstream face 302 a downstream groove 306. The downstream groove 306 is intended to accommodate a downstream axial retaining ring 308.

[0055] [Fig.4] illustrates an example of a distributor foot 400 of a stator of a low pressure turbine included in an embodiment of a sealing system according to the second aspect of the invention.

[0056] According to the example illustrated in [Fig.4], the low pressure distributor foot 400 comprises an abradable support 401 extending radially from a stator base and extending axially between an upstream support face 402 and a downstream support face 403.

[0057] The low pressure distributor foot 400 further comprises an upstream abradable 404 and a downstream abradable 405.

[0058] The upstream abradable 404 extends axially between the upstream face 402 of the support abradable and an upstream face 404.1 of upstream abradable.

[0059] The downstream abradable 405 extends axially between a downstream support face 403 downstream abradable and a downstream face of abradable support 405.1.

[0060] According to one embodiment, the upstream 404 and downstream 405 abradables comprise a material comprising a honeycomb structure.

[0061] [Fig.5] illustrates an embodiment of a sealing system 500 according to the second aspect of the invention.

[0062] In the example illustrated in [Fig. 5], the sealing system 500 comprises an upstream disc head 501 according to the second aspect of the invention, a low pressure distributor foot such as that illustrated with reference to [Fig. 4] and a downstream disc head 503 according to the first aspect of the invention.

[0063] The downstream wiper body 305.1 of the upstream disc head 501 comes into contact with the upstream abradable 404. Similarly, the upstream wiper body 303.1 of the downstream disc head 503 comes into contact with the downstream abradable 405.

[0064] The system formed by the wiper body 305.1, the upstream abradable 404, the downstream abradable 405 and the wiper body 303.1 is watertight and therefore protects the bolted connection from the flow of hot air circulating in the primary vein.

[0065] The disk heads and the low pressure distributors being mounted in circumferential rows on the rotor disks and the stators respectively, sealing is therefore obtained over the entire circumference of each stage of the low pressure turbine.

[0066] The sealing system 500 according to the second aspect of the invention modifies the axial retention mechanism of the blade roots in the disk heads. In other words, the sealing system no longer requires the use of a movable ring in rotation to lock the axial retaining rings.

[0067] It is therefore necessary to modify the method of mounting the axial retaining rings by using a mounting method which is also an object of the present invention.

[0068] [Fig.6] schematically illustrates a flowchart of an embodiment of the method 600 for mounting an axial retaining ring according to the third aspect of the invention.

[0069] According to the embodiment illustrated in [Fig.6], the method 600 comprises a step 601 of introducing the axial retention ring 308 into the downstream groove 306 of the disc head 300.

[0070] The method 600 further comprises a step 602 of introducing a moving blade comprising a blade hook into the disk head 300. Following the introduction of the moving blade into the disk head 300, the blade hook is located opposite the downstream groove 306 of the disk.

[0071] The method 600 according to the embodiment illustrated in [Fig. 6] further comprises a step 603 of radial displacement of the axial retaining ring 308 so as to house it at least partially in the blade hook. This step makes it possible to position the retaining ring in axial abutment against the blade root and to prevent the movement of the blades downstream due to the pressure of the air flowing in the vein.

[0072] According to one embodiment, the displacement of the axial retention ring is carried out after having positioned all the blades in the rotor disk.

[0073] According to another embodiment, the radial displacement of the ring is carried out using a tool.

[0074] [Fig.7] illustrates certain steps of an embodiment of the method 600 according to one aspect of the invention.

[0075] During step 601, the downstream retention ring 308 is inserted into the downstream groove 306 of the disk head 300 according to an object of the invention.

[0076] During step 602, a moving blade 309 is inserted into the disk head 300. The moving blade comprises a blade hook 309a which comes opposite the downstream groove 306.

[0077] During step 603, the axial retaining ring 308 is moved at least partially into the blade hook 309a so as to form an axial stop for the moving blade 309.

Claims

1.

2.

3. Claims Low pressure turbine rotor disc head (300) of a turbomachine, said turbine having an axis of rotation X, said disc head (300): - Extending axially in a direction parallel to the X axis between an upstream face (301) and a downstream face (302) opposite the upstream face (301); - Comprising an upstream lip (303), said upstream lip (303) comprising: • an upstream wiper body (303.1) extending axially from the upstream face (301) and • an upstream rim (303.2) extending radially from the upstream wiper body (303.1) and forming an upstream groove (304) with the upstream face (301) of the disc head (300); - Comprising a downstream lip (305), said downstream lip comprising: • A downstream wiper body (305.1) extending axially from the downstream face (302) and • A downstream rim (305.2) extending radially from the downstream wiper body (305.1) and forming a downstream groove (306) with the downstream face (302) of the disc head (300). Disc head (300) according to the preceding claim in which the upstream licker (301) and the downstream licker (305) comprise a coating comprising a mixture of nickel carbon alloy. Low pressure turbine rotor inter-disc sealing system (500) of a turbomachine, said sealing system comprising: - An upstream disk head (501) according to claim 1 or claim 2; - A low pressure stator distributor foot (400), said distributor foot (400) comprising: • An abradable support (401) extending axially between an upstream support face (402) and a downstream support face (403) opposite the upstream face of support (402); • An upstream abradable (404) extending axially between the upstream support face (402) and an upstream abradable surface (404.1) opposite the upstream support face (402); • A downstream abradable (405) extending axially between the downstream support face (403) and a downstream abradable surface (405.1) opposite the downstream support face (403). - A downstream disc head (503) according to claim 1 or claim 2; - In which: - The downstream wiper body (305.1) of the upstream disc head (501) is in contact with the upstream abradable surface (404) of the low pressure stator distributor foot (400); - The upstream wiper body (303.1) of the downstream disc head (503) is in contact with the downstream abradable surface (405) of the low pressure distributor foot (400).

4. Sealing system (500) according to the preceding claim in which the upstream abradable (404) and the downstream abradable (405) comprise a material having a honeycomb structure formed by a multiplicity of adjacent cells.

5. A turbomachine comprising a low pressure turbine comprising a sealing system according to claim 3 or 4.

6. Method for mounting (600) an axial retention ring for blade roots of a rotor disk of a low-pressure turbine of a turbomachine comprising a disk head according to one of claims 1 or 2, said method comprising the following steps: - Introduction of the axial retention ring (601) into the downstream groove of the disk head; - Introduction of a movable blade (602) comprising a blade hook into the disk head, so as to position the blade hook opposite the downstream groove of the disk; - Radial displacement (603) of the axial retention ring so as to house it at least partially in the blade hook.

7. Method according to the preceding claim in which the displacement of the axial retention ring is carried out after having positioned all the blades in the rotor disc.

8. Method according to claim 7 in which the radial displacement of the ring is carried out using a tool.

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