Turbine rotor comprising a blade stop ring configured to aid the cooling of the blade roots

Abstract

The present invention relates to a turbine rotor (1) comprising a rotor disc (2), provided at its periphery with a plurality of axial cells (23) for receiving a bilobed root (30) of a blade (3), each cell (23) comprising a radially inner cavity (232) and a radially outer cavity (231). This rotor is characterised in that it comprises a ring (4) for axially retaining the blade roots and an annular flange (5), the ring (4) comprising a radially inner portion provided with notches (43) and being arranged against the upstream face (21) of the disc (2), so that each of its notches (43) is located opposite a cell (23) of the disc (2), the flange (5) being secured against the upstream face of the ring (4), forming a space (E) with said disc (2), and comprising at least one air-intake opening (54) which opens into said space (E), and in that each blade (3) comprises a groove (33) for receiving the outer circumferential edge (46) of said ring (4).

Description

[0001] DESCRIPTION

[0002] TITLE: Turbine rotor including a blade stop ring configured to promote cooling of the blade roots.

[0003] FIELD OF THE INVENTION

[0004] The invention lies in the field of turbomachine turbine rotors.

[0005] The present invention relates more specifically to the cooling and axial retention of the blade roots of a turbine rotor, these blade roots having a so-called "fir tree" or "bi-lobed" shape.

[0006] The invention also relates to a turbomachine turbine and a turbomachine, provided with such a rotor.

[0007] STATE OF THE ART

[0008] Conventionally, a turbomachine comprises successively from upstream to downstream, a low pressure compressor, a high pressure compressor, a combustion chamber, a high pressure turbine and a low pressure turbine, which are crossed by an air flow, (upstream and downstream being defined in relation to the direction of flow of this air flow in the turbomachine).

[0009] Each turbine comprises several axially successive stages, from upstream to downstream. Each stage comprises a fixed annular distributor and a mobile rotor, driven in rotation around an axis of rotation, which merges with the longitudinal axis of the turbomachine.

[0010] Each rotor comprises a rotor disc and a plurality of radial blades extending around the disc. The rotor disc is provided at its periphery with a plurality of cells opening onto its outer circumference, each cell being configured to receive the root of such a blade.

[0011] A so-called "fast" low-pressure turbine has been developed. It is so named because its rotor is rotated at a speed higher than that of the rotor of a conventional low-pressure turbine. In order to withstand this high rotation speed, the roots of the rotor blades have a so-called "fir tree" or "bilobed" shape, an example of which can be seen in the attached figure 1.

[0012] In this figure, we can thus see a rotor disk A having a plurality of cells, here only one, referenced B, which allows the reception of the root C of a blade D. The blade root C is bilobed, that is to say that it comprises a radially external lobe C1 located near the blade D and that it is extended by a radially internal lobe C2. The reception cell B consequently comprises a radially external cavity B1 opening towards the outside of the rotor disk and configured to receive the lobe C1 and a radially internal cavity B2 opening into the radially external cavity B1 and configured to receive the lobe C2.

[0013] In order to ensure efficient cooling of the blade root C, it is necessary that the cooling air passes not only into the radially inner cavity B2 of the cell, but also into the radially outer cavity B1.

[0014] However, in the current state of the art, the blade root C is retained axially inside the cell B by a stop ring and a flange (not visible in Figure 1) which blocks the passage of cooling air inside the radially external cavity B1 of the cell B. This leads to a risk of heating and damage to the blade root.

[0015] Document EP 2 357 321 already discloses a turbine rotor comprising a rotor disc, provided at its periphery with a plurality of axial cells, each being configured to receive a blade root. This rotor disc also comprises an axial retaining ring for the blade roots and an annular flange arranged in contact with the retaining ring. This retaining ring is provided with notches, each having a central trunk and lateral branches.

[0016] However, the shape and arrangement of these notches are such that only the ends of the lateral branches are opposite a small part of the blade root receiving cells and that cooling is not effective.

[0017] STATEMENT OF THE INVENTION

[0018] The invention therefore aims to solve the aforementioned problem and to propose a rotor structure which makes it possible to axially block the blade root inside the cell, in both directions, i.e. upstream and downstream, while allowing effective cooling of the radially internal cavity and the radially external cavity of the cell.

[0019] For this purpose, the invention relates to a turbine rotor comprising:

[0020] - a rotor disc with a longitudinal axis of rotation and a plurality of radial blades, this rotor disc being provided at its periphery with a plurality of axial cells each configured to receive a blade root, each blade having a blade root of bilobed shape and each cell comprising a radially internal cavity which is extended by a radially external cavity, - an axial retaining ring for the blade roots, this retaining ring comprising a radially internal part provided with notches and a radially external, solid part,

[0021] -an annular flange, fixed on the upstream side of the rotor disk so that its radially external end is in contact with the retaining ring, this annular flange being configured so as to provide a space with said rotor disk and comprising at least one air intake orifice which opens into said space, and each blade comprises a groove for receiving the external circumferential edge of said retaining ring.

[0022] According to the invention: each notch of the retaining ring is circumferentially delimited on one side and on the other by two radial tabs of the retaining ring, the width, taken in a circumferential direction, of a notch is greater than or equal to the width, taken in a circumferential direction, of a cell, and this retaining ring is arranged against the upstream face of the rotor disk, so that each of its notches is located opposite a cell of the rotor disk, so that cooling air can penetrate through said at least one air intake orifice into said space and then pass through the notches to reach the radially external cavity of the cells of said rotor disk.

[0023] Thanks to these characteristics of the invention, the flange and the retaining ring cooperate to axially hold the blade root inside the receiving cell of the rotor disk and thus prevent any movement of this blade upstream or downstream, while allowing effective cooling of the internal and external cavities respectively of the cell, thanks to the presence of the notches of the retaining ring.

[0024] According to other advantageous and non-limiting characteristics of the invention, taken alone or in combination:

[0025] - the retaining ring includes as many notches as the rotor disc has blade root receiving cells.

[0026] - the rotor comprises an annular seal, arranged between the radially external end of the annular flange and the upstream face of the radially external solid part of said retaining ring. - the annular flange comprises as many cooling orifices as the rotor disc has cells.

[0027] - the annular flange generally has an axial branch and a radial branch, the axial branch is fixed to the rotor disk and the radially external end of said radial branch is in contact with the upstream face of the radially external part of said retaining ring and said at least one air intake orifice is formed in the radial branch of the annular flange.

[0028] - the retaining ring comprises several ring sectors, arranged end to end circumferentially around the longitudinal axis of rotation.

[0029] - the height, taken in a radial direction, of each of the two tabs arranged circumferentially on one side and the other of a notch is less than the height, taken in a radial direction, of the receiving cell of a blade root into which the notch opens.

[0030] The invention also relates to a turbomachine turbine, in particular a low-pressure turbine, equipped with the aforementioned rotor.

[0031] The invention finally relates to a turbomachine comprising at least one such turbine.

[0032] DESCRIPTION OF FIGURES

[0033] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0034] - figure 1 represents a cell of a rotor disk and a fir-tree shaped blade root, received in this cell;

[0035] - Figure 2 is a partial perspective view of a rotor disc, blades, retaining ring and flange according to the invention;

[0036] - figure 3 is an axial and partial sectional view of the rotor disk, a blade of the retaining ring and the flange according to the invention;

[0037] - figure 4 is a perspective view of part of two ring sectors forming the retaining ring according to the invention;

[0038] - Figure 5 is a perspective view of a portion of the retaining ring according to the invention, arranged in front of a rotor disk. DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring to Figures 2 and 3, a rotor 1 can be seen which comprises a rotor disc 2 and a plurality of radial blades 3, arranged around this rotor disc. The rotor disc 2 is rotated about an axis of rotation X-X', which also constitutes its central longitudinal axis.

[0040] The rotor disk 2 has an upstream face 21 and an opposite downstream face 22.

[0041] In the remainder of the description and the claims, the expressions "radially internal" and "radially external" are to be taken into consideration in relation to the position of the axis X-X'.

[0042] Each blade 3 comprises a blade root 30, which has a fir tree or bilobed shape. Each blade root 30 thus comprises a radially external lobe 31 which extends in the internal radial direction by a radially internal lobe 32.

[0043] The rotor disk 2 further comprises at its periphery a plurality of axial cells 23, each of which allows the reception of a root 30 of blade 3. Each cell 23 opens radially outwards.

[0044] As explained previously, each cell 23 comprises a radially external cavity 231 which opens outwards and which extends radially inwards by a radially internal cavity 232. The cavity 231 receives the lobe 31 and the cavity 232 receives the lobe 32 of the blade root.

[0045] According to the invention, the rotor 1 also comprises a retaining ring 4 and an annular flange 5, which will now be described in more detail.

[0046] The ring 4 allows the axial retention of the roots 30 of the blades 3. As is better seen in FIG. 4, this ring 4 has a flat upstream face 40 and an opposite downstream face 41 which is also flat. In addition, this axial retention ring 4 comprises a radially internal part 42, provided with a plurality of notches 43 and a solid radially external part

[0047] 44. The radially external part 44 is said to be “solid”, because it does not have any notches 43. In other words, the notches 43 do not extend to this part.

[0048] The radially inner portion 42 also includes a plurality of radial tabs

[0049] 45, each tab 45 extending between two neighboring notches 43. In other words, each notch 43 is circumferentially delimited on one side and the other by two radial tabs 45. Thus, as can be seen in FIG. 4, each notch 43 extends radially, has a substantially U-shape and opens out at the internal circumferential edge of the ring 4. The tabs 45 make it possible to firmly press the ring 4 against the rotor disk 2 and thus improve the seal between the two.

[0050] Advantageously, and as is better shown in Figures 4 and 5, the tabs 45 may have a cutout 450 at their upstream face and close to their radially internal end. Such a cutout 450 makes it possible to refine the internal end of the tab and to lighten the overall weight of the ring 4.

[0051] Furthermore, the ring 4 comprises at its external circumference a curved edge 46.

[0052] The retaining ring 4 may be a single-piece ring that extends over 360° and may or may not be split. It may also be composed of several ring sectors, assembled circumferentially end-to-end to form said ring. The number of sectors is not limiting, but preferably it is between two and fifteen and it is advantageously a divisor of the number of blades. As a purely illustrative example, two neighboring ring sectors, referenced 4A and 4B, can be seen in Figure 4.

[0053] The retaining ring 4 is positioned on the rotor disk 2, so that its flat downstream face 41 is in contact with the upstream face 21 of this disk and so that its radially external part 44 is located opposite the radially external end of the cells 23, as appears better in FIG. 3 and also so that its central axis is coaxial with the central longitudinal axis X-X' of the disk 2.

[0054] Furthermore, this retaining ring 4 is positioned so that each notch 43 is located opposite a cell 23, as is better seen in FIG. 5. Preferably, the ring 4 comprises as many notches 43 as there are cells 23 on the rotor disc 2.

[0055] The tabs 45 do not contribute to the sealing but are there to improve the support of the ring 4 on the disc 2. Indeed, without these tabs, the ring 4 would risk moving more. The dimensions of each tab 45 are therefore adapted accordingly.

[0056] Referring to Figure 5, it can be seen that the tangential width (taken in a circumferential direction) L1 of a tab 45 is less than the width L2, taken in a circumferential direction, between two adjacent cells 23 of the disc 2, so as not to obstruct the passage of the cooling air through these cells 23. Also preferably, this tangential width L1 is greater than or equal to 5 millimeters (mm).

[0057] Furthermore, the height H of a tab 45 (which also corresponds to the height H of a notch 43), taken in a radial direction, is preferably greater than 2 mm. Also preferably, this height H is less than the overall height H1, taken in a radial direction, of the cell 23, since the part 44 of the ring 4 is located opposite the upper end of the radially external cavity 231 of the cell 23, as can be seen in FIG. 3. By way of example, the height of this cell 23 can reach 50 mm.

[0058] Finally, preferably, the dimensions of the notches 43, and in particular the width L3, taken in a circumferential direction, of a notch 43 is greater than or equal to the width, taken in a circumferential direction of a cell 23, so that when the retaining ring 4 is in place, the notches 43 do not obstruct the passage of air through the cell 23 and allow the air to properly cool the radially internal cavities 232 and the radially external cavities 231.

[0059] Each blade 3 further comprises a groove 33 for receiving a portion of the circumference of the retaining ring 4 or more precisely for receiving a portion of the external circumferential edge 46 of the ring 4.

[0060] Advantageously, and as can be seen in Figure 3, the blade 3 comprises an upstream spoiler 34 which extends axially upstream and which is provided on its radially internal face with a radially internal tab 35. It is this radially internal tab 35 which is provided with said groove 33 and this groove 33 opens out in the direction of the axis X-X'.

[0061] As can be seen in Figure 2, when the different blades 3 are placed in the cells 23 of the rotor disk 2, their respective upstream spoilers 34 touch.

[0062] The groove 33 is advantageously shaped and dimensioned so that the edge 46 is inserted therein without play. In other words, the groove 33 has, for example, in axial section a semi-circular section, when the rim 46 is semi-circular and this groove 33 is curved according to the same radius of curvature as that of the ring 4.

[0063] Advantageously, anti-rotation fingers 47 are provided on the upstream face 40 of the ring, close to the edge 46. As can be seen in FIG. 5, the anti-rotation finger 47 comes into contact with the radially internal tab 35 and cooperates with it to prevent rotation of the ring 4 relative to the blades 3 and the rotor disk 2.

[0064] Preferably, the ring 4 comprises several anti-rotation fingers 47 or each ring sector 4A, 4B comprises two anti-rotation fingers, one for each direction of rotation.

[0065] As can be seen in Figure 3, the annular flange 5 is configured to be positioned on the upstream side of the rotor disk 2 and to delimit therewith a space E. Advantageously, the annular flange 5 thus has an L-shaped cross-section with an axial branch 50 which extends radially outwards by a radial branch 51. Preferably, the radial branch 51 comprises at its radially external end 52 a projecting part which extends axially downstream.

[0066] Advantageously, but not necessarily, an annular groove 53 is formed in this projecting part. This groove 53 opens downstream and is intended to receive an annular seal 6, preferably an O-ring.

[0067] Furthermore, the flange 5 comprises at least one air intake orifice 54, preferably arranged in the radial branch 51. Preferably, the flange 5 comprises several air intake orifices 54 and more preferably, as many orifices 54 as there are cells 23 on the rotor disk 2. Preferably, each orifice 54 is aligned with a cell 23 when the flange is in place.

[0068] The annular flange 5 is fixed to the rotor disk 2, so that its central axis is coaxial with the central longitudinal axis X-X' of the disk 2 and so that its radially external end 52 is in contact with the retaining ring 4. In addition, when the seal 6, housed in the annular groove 53, is present, the fixing of the flange 5 to the disk 2 is done so that the end 52 is in contact with the upstream face 40 of the solid radially external part 44.

[0069] Furthermore, the flange 5 is fixed to the rotor disk 2 using a fixing device 7. This fixing device 7 is for example a ring, which cooperates with the downstream end of the axial branch 50 of the flange 5 and with the rotor disk 2 to ensure fixing. Other fixing devices 7 could also be envisaged, for example a screw fixing.

[0070] Furthermore, it will be noted that when the ring 4 is in several annular sectors, for example at least two, it is then necessary to provide several projecting edges (or walls) 210 on the upstream face 21 of the rotor disk 2, preferably as many edges as sectors. As can be seen in Figures 3 and 5, these edges 210 are arranged so as to be radially inward relative to the tongues 45, to block them and prevent the ring 4 from disengaging from the groove 33.

[0071] When the retaining ring 4 and the annular flange 5 are positioned on the rotor disk 2, as shown in Figure 3, the cooling air coming from upstream (on the left in Figure 3) enters the space E, through the air intake orifices 54, as shown by the arrow i. This cooling air can then flow into the radially internal cavity 232 of each cell 23, as shown by the arrow ii and also into the radially external cavity 231, as shown by the arrow iii, thanks to the presence of the notches 43. For this purpose, it will be noted that in Figure 3, the respective contours of the blade root 30 and the cell 23 have been deliberately shown in dotted lines and by having rotated them through 90°. This representation is purely schematic and makes it possible to visualize the height at which the different lobes 31, 32 of the blade root and the different cavities 231 and 232 are located.In reality, the blade root and the cell obviously extend axially, as can be seen in figures 2 and 5.

[0072] The annular flange 5 ensures sealing between the upstream part of the flange 5 and the space E. This sealing is also reinforced by the presence of the seal 6, arranged against the radially external part 44 of the retaining ring 4 free from notches 43.

[0073] Furthermore, the flange 5 allows the calibration of the cooling air by the sizing of the air intake orifices 54 which are smaller than the notches 43.

[0074] In addition, the retaining ring 4 and the annular flange 5 cooperate to ensure the axial locking of the blade roots 30 in the cells 23 of the disc 2. Indeed, the movement of the blade root 30 downstream (towards the right in FIG. 3) or upstream (towards the left in FIG. 3) is prevented by the fact that the groove 33 of the blade 3 is locked on the rim 46 of the ring 4, itself pressed against the upstream face 21 of the rotor disc 2 by the flange 5.

[0075] The device according to the invention thus makes it possible to ensure the cooling of the radially external cavities 231 of the cells 23 of the rotor disk 2, while ensuring the axial locking of the blades 3.

[0076] Although this is not limiting, the rotor according to the invention finds a particular application in turbomachine turbines and more particularly in low pressure turbines.

Claims

DEMANDS 1. Turbine rotor (1), comprising: -a rotor disk (2) with longitudinal axis of rotation (X-X') and a plurality of radial blades (3), this rotor disk (2) being provided at its periphery with a plurality of axial sockets (23) each configured for receiving a blade foot (30), each blade (3) having a blade foot (30) of bilobed shape and each socket (23) comprising a radially internal cavity (232) which extends into a radially external cavity (231), -an axial retaining ring (4) for the feet (30) of the blades, this retaining ring (4) comprising a radially internal part (42) provided with notches (43) and a radially external part (44), solid, -an annular flange (5), fixed to the upstream side of the rotor disc (2) such that its radially external end (52) is in contact with the retaining ring (4), this annular flange (5) being configured to provide a space (E) with said rotor disc (2) and comprising at least one air inlet orifice (54) which opens into said space (E), and each blade (3) comprising a groove (33) for receiving the external circumferential edge (46) of said retaining ring (4), this rotor being characterized in that each notch (43) of the retaining ring (4) is circumferentially delimited on one side and the other by two radial tabs (45) of the retaining ring (4), in that the width (L3), taken in a circumferential direction, of a notch (43) is greater than or equal to the width, taken in a circumferential direction, of a cavity (23), and in that said retaining ring (4) is disposed against the upstream face (21) of the rotor disc (2),so that each of its notches (43) is located opposite a cavity (23) of the rotor disc (2), so that cooling air can enter through said at least one air intake orifice (54) into said space (E) and then pass through the notches (43) to reach the radially external cavity (231) of the cavities (23) of said rotor disc (2).

2. Turbine rotor (1) according to claim 1, characterized in that the retaining ring (4) includes as many notches (43) as the rotor disc (2) has receiving recesses (23) for a blade foot.

3. Turbine rotor (1) according to claim 1 or 2, characterized in that it comprises an annular sealing gasket (6), disposed between the radially external end (52) of the annular flange (5) and the upstream face of the solid radially external part (44) of said retaining ring (4).

4. Turbine rotor (1) according to any one of the preceding claims, characterized in that the annular flange (5) comprises as many cooling orifices (54) as the rotor disc (2) has alveoli (23).

5. Turbine rotor (1) according to any one of the preceding claims, characterized in that the annular flange (5) has globally an axial branch (50) and a radial branch (51), in that the axial branch (50) is fixed to the rotor disc (2) and the radially external end (52) of said radial branch (51) is in contact with the upstream face of the radially external part (44) of said retaining ring (4) and in that said at least one air inlet orifice (54) is formed in the radial branch (51) of the annular flange (5).

6. Turbine rotor (1) according to any one of the preceding claims, characterized in that the retaining ring (4) comprises several ring sectors (4A, 4B), arranged end to end circumferentially around the longitudinal axis of rotation (X-X').

7. Turbine rotor (1) according to any one of the preceding claims, characterized in that the height (H), taken along a radial direction, of each of the two tabs (45) arranged circumferentially on one side and the other of a notch (43) is less than the height (H1), taken along a radial direction, of the receiving cavity (23) of a blade foot into which the notch (43) opens.

8. Turbomachine turbine, in particular low pressure turbine, characterized in that it comprises at least one rotor (1) according to any one of the preceding claims.

9. Turbomachine, characterized in that it comprises at least one turbomachine turbine according to claim 8.

Images