TURBOMACHINE TURBINE DISC ASSEMBLY

Abstract

TITLE: TURBOMACHINE TURBINE DISC ASSEMBLY One aspect of the invention relates to a turbomachine turbine disc assembly (10) comprising: a first annular flange (200) of an upstream disc (20) and a second annular flange (300) of a downstream disc (30), the annular flanges having circumferentially distributed fixing holes (210, 310), a connecting interface (400) of a sealing ring (40) arranged between the two flanges, the connecting interface (400) having circumferentially distributed fixing holes (410), means for fixing the two flanges with the sealing ring, each means for fixing comprising: a screw (510) having a head (513) bearing against the second flange, and a nut (520) bearing against the first flange. The assembly includes a protective plate (60) bearing against an anti-rotation surface (306) of the second annular flange and received in a notch (518) of the screw head.Figure to be published with the abbreviation: Figure 3.

Description

Title of the invention: TURBOMACHINE TURBINE DISC ASSEMBLY TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of turbine discs of a turbomachine such as an aircraft turbojet.

[0002] The present invention relates more particularly to a means of fixing the annular flanges of two discs, one relative to the other. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Conventionally, a low-pressure turbomachine turbine comprises several discs, each ensuring the positioning of the turbine blades in an air stream and providing support for turbine sealing components, such as movable sealing rings. Furthermore, each disc includes a first and a second annular flange for transmitting the torque from the low-pressure turbine blades to a low-pressure turbine shaft.

[0004] A turbomachine turbine comprises several sets of disks. As shown in [Fig. 1], a set of disks 10 comprises: - an upstream disc 20 comprising a first annular flange 200, - a downstream disc 30 comprising a second annular flange 300, and - means of fixing 50 of the first and second annular flanges 200, 300.

[0005] The first and second annular flanges 200, 300 each comprise mounting holes 210, 310 aligned with each other and distributed circumferentially. Each fastening means 50 comprises a screw 510 having a head 513 arranged to bear against the second annular flange 300, and a nut 520 arranged to bear against the first annular flange 200.

[0006] The second annular flange 300 comprises a contact surface 302 and a fixing surface 304 axially opposed to each other, and an anti-rotation surface 306 which extends substantially perpendicularly from the fixing surface 304.

[0007] According to a particular embodiment illustrated in [Fig.2], the turbomachine turbine includes a sealing ring 40 having a connecting interface 400 arranged between the first and second annular flanges 200, 300. The connecting interface 400 also includes fixing holes 210, 310 aligned with the fixing holes 210, 310 of the first and second annular flanges 200, 300 and distributed circumferentially.

[0008] The space around the head 513 of the screw 510 does not allow the passage of a tool for tightening the screw 510, therefore the tightening of the fastening means 50 is carried out by tightening the nut 520. Consequently, in order to block the rotation of the screw 510 when tightening the nut 520, the head 513 of the screw 510 has a lateral edge 516, part of which is in contact with the anti-rotation surface 306 of the second annular flange 300.

[0009] However, when tightening the fastening means 50, the bearing of a portion of the lateral edge 516 of the head 513 of the screw 510 against the anti-rotation surface 306 of the second annular flange 300 is significant. This can damage the anti-rotation surface 306 and cause marks such as fine nicks or rounded-bottom impacts on this surface. In some cases, the screw 510 is misaligned so that its head 513 does not bear properly against the fastening surface 304 of the second annular flange 300, which can cause deeper marks or nicks on the anti-rotation surface 306 of the second annular flange 300 when tightening the fastening means 50.

[0010] The presence of at least one mark on the anti-rotation surface of the annular flange corresponds to a geometric defect which causes a decrease in the life of the disc, and premature replacement of the disc. Summary of the invention

[0011] The invention offers a solution to the problems mentioned above, by proposing a set of turbomachine turbine discs comprising a means for fixing the annular flanges of two discs and an element for protecting the annular flanges from the fixing means.

[0012] A first aspect of the invention relates to an assembly of turbomachine turbine discs comprising: - a first annular flange of an upstream disc and a second annular flange of a downstream disc, the first and second annular flanges each having circumferentially distributed fixing holes, - means for fixing the first and second annular flanges, each means of fixing comprising: • a screw having a head arranged to bear against the second annular flange, and • a nut arranged to bear against the first annular flange,

[0013] The turbomachine turbine disc assembly includes an annular protective plate arranged to bear against an anti-rotation surface of the second annular flange and received in a notch in the head of the screw.

[0014] The set of discs according to the invention allows, thanks to the presence of a plate of protection between the screw head and the anti-rotation surface of the second annular flange, to protect the anti-rotation surface when tightening the fastening means and thus limit damage to the anti-rotation surface.

[0015] Advantageously, the second annular flange comprises a contact surface and a fixing surface opposite to each other, and the anti-rotation surface of the second annular flange extends substantially perpendicularly from its fixing surface.

[0016] Preferably, the notch in the screw head is arranged in a lateral edge of the screw head and is open on an internal surface of the screw.

[0017] Advantageously, the notch in the head of the screw extends at least partially along the perimeter of the lateral edge of the head.

[0018] According to a first embodiment of the screw, the notch in the head of the screw extends along only a part of the perimeter of the lateral edge of the head.

[0019] According to a second embodiment of the screw, the notch in the head of the screw extends along the entire perimeter of the lateral edge of the head.

[0020] Preferably, the protective plate has an L-shaped cross-section comprising: - a radial portion comprising a free internal end housed in the notch of the screw head, and - an axial part substantially perpendicular to the radial part and having a free end external to the outside of the notch in the head of the screw.

[0021] Advantageously, the protective plate is a split ring that extends circumferentially along the anti-rotation surface of the second annular flange.

[0022] Preferably, the protective plate in the form of a split ring includes a slot positioned between two fastening means.

[0023] According to a particular embodiment, the turbine disc assembly of the tur-bomachine includes a sealing ring having a connecting interface arranged between the first and second annular flanges and including circumferentially distributed fixing holes arranged opposite the fixing holes of the first and second annular flanges.

[0024] A second aspect of the invention relates to a low pressure turbine of a tur-bomachine comprising assemblies of discs according to the first aspect of the invention.

[0025] A third aspect of the invention relates to a turbomachine comprising assemblies of discs according to the first aspect of the invention.

[0026] A fourth aspect of the invention relates to a method for assembling a set of discs according to the first aspect of the invention, the method comprising the steps successive following: - positioning of the first annular flange of the upstream disc so that the fixing hole extends in a vertical direction, - positioning of the second annular flange of the downstream disc opposite the first annular flange, - alignment of the fixing holes of the first and second annular flanges, - positioning of the protective plate against the anti-rotation surface of the second annular flange, - Inserting the screw of the fastening means into the fastening holes so that the protective plate is housed in the notch of the screw head, and the screw head is resting against the second annular flange, and - tighten the nut relative to the screw until the nut is pressed against the first annular flange.

[0027] Advantageously, the assembly method includes, before the tightening step, an additional step of orienting the notch of the head of the screw of the fastening means opposite the anti-rotation surface of the second annular flange.

[0028] Preferably, the positioning step of the protective plate in the form of a split ring includes a sub-step of positioning its slot between two fixing holes of the second annular flange.

[0029] 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

[0030] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which: - Fig. 1, already described, is a front view of a set of turbomachine turbine discs according to the prior art; - Fig. 2, already described, is a front view of a set of turbomachine turbine discs according to a particular embodiment of the prior art; - Fig. 3 is a front view of a set of turbomachine turbine discs including a protective plate according to a first embodiment of the invention; - Fig. 4 is a front view of a set of turbomachine turbine discs according to a second embodiment of the invention; - Fig. 5 is a side view in perspective of a protective plate from figures 3 and 4; - Figure 6 is a front view of an assembly of several sets of turbomachine turbine discs according to the second embodiment of the invention. DETAILED DESCRIPTION

[0031] An example of an embodiment of a turbomachine turbine disc assembly 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.

[0032] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0033] For the purposes of understanding the invention, the radial, tangential, and axial orientations of the RTA frame shown in the figures shall be adopted, the tangent T and axial A axes of which extend in a horizontal plane in the orientation shown in the figures. The axial axis A is parallel to an X axis of the annular flanges of the upstream and downstream discs of the turbomachine turbine disc assembly. An upstream disc towards a downstream disc of the turbomachine turbine disc assembly is oriented along the axial axis A of the RTA frame.

[0034] In the description, the terms "upstream" and "downstream" are defined with respect to the direction of air flow from the air inlet into the turbomachine to the air outlet out of the turbomachine.

[0035] Figure 3 illustrates a set of 10 discs according to a first embodiment of the invention comprising: - an upstream disc 20 comprising a first annular flange 200 with X-axis connected to a ferrule 220, - a downstream disc 30 comprising a second annular flange 300 with X-axis connected to a ferrule 320, - means of fixing 50 of the first and second annular flanges, and - a 60 annular X-axis protection plate.

[0036] The first and second annular flanges 200, 300 each comprise: - a contact surface 202, 302 and a fixing surface 204, 304 axially opposed to each other, and - fixing holes 210, 310, distributed circumferentially and each passing through the first or second annular flange 200, 300 from its contact surface 202, 302 to its fixing surface 204, 304.

[0037] As shown in figures 3 and 4, the second annular flange 300 also includes an anti-rotation surface 306 which extends substantially perpendicularly downstream, that is to say from its fixing surface 304 towards the ferrule 320 of the second annular flange 300.

[0038] As shown in [Fig. 3], the anti-rotation surface 306 of the second flange annular 300 includes a connecting section 306C in the form of a circular arc connecting the anti-rotation surface 306 to the fixing surface 304.

[0039] According to an unrepresented variant of the annular flange 300, its anti-rotation surface 306 extends substantially upstream, that is to say from its fixing surface 304 to its contact surface 302.

[0040] Each fastening means 50 comprises: - a screw 510 comprising a main body 512 extending parallel to the X-axis and connected to a head 513, the head 513 comprising: • an internal surface 514 and an external surface 515 axially opposed to each other, the internal surface being connected to the main body 512, and • a lateral edge 516 connecting the inner surface 514 to the outer surface 515 and comprising a notch 518 which is open on the inner surface 514 and which extends at least partially along the perimeter of the lateral edge 516 of the head 513, - a nut 520 comprising an external surface 522 and an internal surface 524 axially opposed to each other, the internal surface 524 being opposite the internal surface 514 of the screw 510.

[0041] According to a second embodiment of the invention as represented in [Fig.4], the set of discs 10 differs from that of the first embodiment in that it includes a sealing ring 40 having a connecting interface 400 arranged between the first and second annular flanges 200, 300.

[0042] The 400 link interface comprises: - a first and a second bearing surfaces 402, 404 axially opposed to each other, - fixing holes 410 distributed circumferentially and each passing through the linking interface 400 from its first bearing surface 402 to its second bearing surface 404.

[0043] As shown in Figures 3 and 4, the notch 518 in the head of the screw 510 corresponds to a cut in the lateral edge 516, the notch 518 comprising: - a first section 518A extending radially from the lateral edge 516 of the head 513 towards the inside of the head 513 of the screw 510, - a second section 518B extending axially from the internal surface 514 of the head 513 to the internal surface 514 of the screw 510, and - a connecting section 518C in the form of a circular arc linking the first section to the second section.

[0044] According to a first variant of the screw 510, the notch 518 of the head 513 of the screw 510 extends along only a part of the perimeter of the lateral edge 516 of the head 513. According to a second variant of the screw 510, the notch 518 of the head 513 of the screw 510 extends along the entire perimeter of the lateral edge 516 of the head 513.

[0045] Advantageously, the head 513 of the screw 510 has a hexagonal, rectangular or square shaped surface so as to optimize the surface between the lateral edge 516 of the head and the anti-rotation surface 306 of the second annular flange 300.

[0046] As shown in [Fig. 5], the protective plate 60 is a split ring extending circumferentially between a first edge 60A and a second edge 60B separated from each other by a slot 64. The protective plate 60 has an L-shaped cross-section and comprises: - a radial portion 610 comprising an internal free end 612, and - an axial part 620 substantially perpendicular to the radial part 610 and comprising an external free end 622.

[0047] The protective plate 60 is flexible between a rest position of the protective plate 60, according to which the size of the slot 64 is initial, and a retraction position of the protective plate 60, according to which the size of the slot 64 is less than its initial size, or even zero.

[0048] Advantageously, the protective plate 60 is made of a metallic material and has a thickness greater than or equal to 0.1 millimeter, preferably between 0.1 and 1 millimeter. The length of the axial portion 620 of the protective plate 60 is greater than the axial length of the anti-rotation surface 306 of the second annular flange 300 in order to completely protect the anti-rotation surface 306 of the head 513 of the screw 510 when the fastening means 50 is tightened. Preferably, the length of the axial portion 620 is equal to the axial length of the anti-rotation surface 306 plus an axial distance of between 2 and 3 millimeters.

[0049] According to an unshown variant of the protective plate 60, it includes a connecting section in the form of a circular arc linking the radial part 610 and the axial part 620. This feature, by rounding the angle between the radial part 610 and the axial part 620, limits the risk of marking the anti-rotation surface 306 by the corner of the protective plate 60. Consequently, only the axial part 620 of the protective plate is in contact with the anti-rotation surface 306 and the protective plate 60.

[0050] In the assembled position of the set of discs 10 according to the first and second embodiments of the invention: - the contact surface 202 of the first annular flange 200 is opposite the contact surface 302 of the second annular flange 300, - the fixing holes 210, 310 of the first annular flange 200, the second annular flange 300 and the connecting interface 400 are aligned compared to each other, - the head 513 of the screw 510 is supported against the second annular flange 300 so that its internal surface 514 is in contact with the fixing surface 304 of the second annular flange 300, - the nut 520 is supported against the first annular flange 200 so that its internal surface 524 is in contact with the fixing surface 204 of the first annular flange 200, and - the protective plate 60 extends circumferentially along the anti-rotation surface 306 of the second annular flange 300 according to which: • the radial part 610 of the protective plate 60 is arranged parallel to the fixing surface 304 of the second annular flange 300 so that the free internal end 612 is received in the notch 518 of the head 513 of the screw 510, • the axial portion 620 of the protective plate 60 is arranged against the anti-rotation surface 306 of the second annular flange 300 such that its external free end 622 is outside the notch 518 of the head 513 of the screw 510 and extends beyond the head 513 of the screw 510, and • the slot 64 of the protective plate 60 is positioned between two fixing means 50 of the disc assembly 10.

[0051] In the assembled position of the set of discs 10 according to the first embodiment of the invention, the contact surface 202 of the first annular flange 200 is in contact with the contact surface 302 of the second annular flange 300.

[0052] In the assembled position of the set of discs 10 according to the second embodiment of the invention, the connecting interface 400 of the sealing ring 40 is arranged between the first and second annular flanges 200, 300 so that its first bearing surface 402 is in contact with the contact surface 202 of the first annular flange 200 and its second bearing surface 404 is in contact with the contact surface 302 of the second annular flange 300.

[0053] As shown in [Fig. 6], a turbomachine turbine comprises several sets of discs 10 connected to each other. More particularly, the upstream disc 20 of each set of discs 10 is necessarily arranged upstream of the downstream disc 30 of the same set of discs 10, along the axial direction A.

[0054] As illustrated in [Fig. 4], each set of discs 10 is connected to another set of discs 10 by a leek 23, that is, the combination of a web (thin part) and a bore (wide part) which extends radially between a first end 23A and a second free end 23B. More particularly, a leek 23 connects the ferrule 220 of the first annular flange 200 of the upstream disc 20 of a set of discs 10 to the ferrule 320 of the second annular flange 300 of the downstream disc 30 of another set of discs 10, at its first end 23A. Therefore, the first annular flange 200, the leek 23 and the second annular flange 300 form one and the same piece.

[0055] The method for assembling a set of discs 10 according to the first embodiment comprises the following successive steps: - positioning of the first annular flange 200 of the upstream disc 20 so that its axis X extends along a vertical direction V, - positioning of the second annular flange 300 of the downstream disc 30 so that its axis X extends along the vertical direction V, and bringing its contact surface 302 into contact with the contact surface 202 of the first annular flange 200, - alignment of the fixing holes 210, 310, 410 of the first and second annular flanges 200, 300 relative to each other, - positioning of the protective plate 60 so that its radial part 610 is opposite the fixing surface 304 of the second annular flange 300 and that its axial part 620 is in contact with the anti-rotation surface 306 of the second annular flange 300, and positioning of its slot 64 between two fixing holes 310 of the second annular flange 300, - insertion of the screw 510 of the fastening means 50 into the fastening holes 210, 310, 410 so that the head 513 of the screw 510 is bearing against the second annular flange 300, and - tightening the nut 520 relative to the screw 510 until the internal surface 524 of the nut 520 is in contact with the fixing surface 204 of the first annular flange 200.

[0056] The method for mounting a set of discs 10 according to the second embodiment of the invention differs from that of the first embodiment in that: - it comprises, after the positioning step of the first annular flange 200, an additional positioning step of the connecting interface 400 of the sealing ring 40 so that its axis X extends along the vertical direction V, and bringing its first bearing surface 402 into contact with the contact surface 202 of the first annular flange 200, - during the positioning step of the second annular flange 300, its contact surface 302 is brought into contact with the second bearing surface 404 of the connecting interface 400, and - the alignment step consists of aligning the fixing holes 210, 310, 410 of the first and second annular flanges 200, 300 and of the linking interface 400 with respect to each other.

[0057] The positioning step of the protective plate 60 comprises the following sub-steps: - bringing the first and second edges 60A, 60B of the protective plate 60 closer together until the protective plate 60 reaches the retraction position in which the size of the slot 64 is less than its initial size, or even zero, - installation of the protective plate 60 around the anti-rotation surface 306 of the second annular flange 300, and - release of the protective plate 60 to its rest position in which the size of the slot 64 corresponds to its initial size, the protective plate 60 is thus pressed against the anti-rotation surface 306 and held in position relative to the second annular flange 300.

[0058] In the case where each fastening means 50 includes a screw 510 according to its first embodiment, i.e. according to which the notch 518 extends along only a part of the perimeter of the head 513 of the screw 510, the assembly method includes, before the tightening step, an additional step of orienting the notch 518 of the head 513 of the screw 510 opposite the anti-rotation surface 306 of the second annular flange 300 in order to house the radial part 610 of the protective plate 60 in the notch 518.

[0059] In the case where each fastening means 50 includes a screw 510 according to its second embodiment, i.e. according to which the notch 518 extends along the entire perimeter of the head 513 of the screw 510, no orientation step of the notch 518 of the head 513 of the screw 510 is required during the assembly process.

[0060] A set of discs 10 according to the invention provides protection for the anti-rotation surface 306 of the second annular flange 300 of the downstream disc 30 by means of the protective plate 60 and the notch 518 in the head 513 of the screw 510 configured to receive the protective plate 60 in the assembled position of the disc set 10. The installation of a protective plate 60 significantly limits damage to the anti-rotation surface 306, such as the appearance of marks when tightening the fastening means 50. Protecting the anti-rotation surface of the discs increases the service life of the turbine discs and reduces the need for repairs and the replacement of damaged discs.

Claims

Claims

1. Set of turbomachine turbine disks (10) comprising: - a first annular flange (200) of an upstream disk (20) and a second annular flange (300) of a downstream disk (30), the first and second annular flanges (200, 300) each comprising circumferentially distributed fixing holes (210, 310), - fixing means (50) of the first and second annular flanges (200, 300), each fixing means (50) comprising: • a screw (510) comprising a head (513) arranged to bear against the second annular flange (300), and • a nut (520) arranged to bear against the first annular flange (200), characterized in that it comprises an annular protection plate (60) arranged to bear against an anti-rotation surface (306) of the second annular flange (300) and received in a notch (518) of the head (513) of the screw (510).

2. A turbine disc assembly (10) according to claim 1, characterized in that: - the second annular flange (300) comprises a contact surface (302) and a fixing surface (304) opposite each other, and, - the anti-rotation surface (306) of the second annular flange (300) extends substantially perpendicularly from its fixing surface (304).

3. A turbine disc assembly (10) according to any preceding claim, characterized in that the notch (518) of the head (513) of the screw (510) is arranged in a lateral edge (516) of the head (513) of the screw (510) and is open on an inner surface (514) of the screw (510).

4. A turbine disc assembly (10) according to claim 3, characterized in that the notch (518) of the head (513) of the screw (510) extends at least partially along the perimeter of the lateral edge (516) of the head (513).

5. A set of turbine discs (10) according to any one of the preceding claims, characterized in that the protective plate (60) has an L-shaped section comprising: - a radial portion (610) comprising an internal free end (612) housed in the notch (518) of the head (513) of the screw (510), and - an axial portion (620) substantially perpendicular to the radial portion and comprising an external free end (622) outside the notch (518) of the head (513) of the screw (510).

6. A turbine disc assembly (10) according to any preceding claim, characterized in that the protective plate (60) is a split ring which extends circumferentially along the anti-rotation surface (306) of the second annular flange (300).

7. A turbine disc assembly (10) according to claim 6, characterized in that the protective plate (60) comprises a slot (64) positioned between two fixing means (50).

8. A set of turbine discs (10) according to any one of the preceding claims, characterized in that it comprises a sealing ring (40) comprising a connecting interface (400) arranged between the first and second annular flanges (200, 300) and comprising fixing holes (410) distributed circumferentially and arranged opposite the fixing holes (210, 310) of the first and second annular flanges (200, 300).

9. Turbomachine, characterized in that it comprises sets of discs (10) according to any one of claims 1 to 7.

10. A method of mounting a set of discs (10) according to any one of claims 1 to 8, the method comprising the following successive steps: - positioning the first annular flange (200) of the upstream disc (20) so that the fixing hole (210) extends in a vertical direction, - positioning the second annular flange (300) of the downstream disc (30) opposite the first annular flange (200), - aligning the fixing holes (210, 310, 410) of the first

11. and second annular flanges (200, 300), - positioning the protective plate (60) in abutment against the anti-rotation surface (306) of the second annular flange (300), - introduction of the screw (510) of the fixing means (50) into the fixing holes (210, 310, 410) so that the protective plate (60) is housed in the notch (518) of the head (513) of the screw (510), and that the head (513) of the screw (510) bears against the second annular flange (300), - tightening the nut (520) relative to the screw (510) until the nut (520) is in contact with the first annular flange (200). Mounting method according to claim 10, characterized in that it comprises, before the tightening step, an additional step of orienting the notch (518) of the head (513) of the screw (510) of the fixing means (50) opposite the anti-rotation surface (306) of the second annular flange (300).

Images