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

DOMAINE DE L'INVENTION

[0001] The invention lies in the field of turbomachine turbine rotors.

[0002] 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 shape known as "fir tree" or "bilobed".

[0003] The invention also relates to a turbomachine turbine and a turbomachine, equipped with such a rotor. ETAT DE LA TECHNIQUE

[0004] In a classic way, 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 traversed by an airflow, (upstream and downstream being defined with respect to the direction of flow of this airflow in the turbomachine).

[0005] Each turbine comprises several axially successive stages, from upstream to downstream. Each stage includes a fixed annular distributor and a movable rotor, driven in rotation around an axis of rotation, which coincides with the longitudinal axis of the turbomachine.

[0006] Each rotor comprises a rotor disc and a plurality of radial blades extending around this disc. The rotor disc is provided at its periphery with a plurality of recesses opening onto its outer circumference, each recess being configured to receive the root of such a blade.

[0007] A low-pressure turbine, known as a "high-speed" turbine, has been developed. It is called this because its rotor is driven at a higher speed than that of a conventional low-pressure turbine. To withstand this high rotational speed, the rotor blade roots have a "fir tree" or "bilobed" shape, an example of which can be seen on the... figure 1 attached.

[0008] In this figure, we can see a rotor disk A with a plurality of recesses, here a single one, labeled B, which receives the root C of a blade D. The blade root C is bilobed, meaning it comprises a radially external lobe C1 located near the blade D and extends into a radially internal lobe C2. The receiving recess B therefore has a radially external cavity B1 opening to the outside of the rotor disk and configured to receive lobe C1, and a radially internal cavity B2 opening into the radially external cavity B1 and configured to receive lobe C2.

[0009] In order to ensure effective cooling of the blade foot C, it is necessary that the cooling air passes not only into the radially internal cavity B2 of the alveolus, but also into the radially external cavity B1.

[0010] However, in the current state of the art, the blade foot C is axially retained inside the cavity B by a retaining ring and a flange (not visible on the figure 1 ) which blocks the passage of cooling air inside the radially external cavity B1 of the alveolus B. This leads to a risk of overheating and damage to the blade foot.

[0011] We already know, from document EP 2 357 321, of a turbine rotor comprising a rotor disc, provided around its periphery with a plurality of axial recesses, each configured to receive a blade root. This rotor disc also includes an axial retaining ring for the blade roots and an annular flange disposed in contact with the retaining ring. This retaining ring has notches, each having a central shaft and lateral branches.

[0012] 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 receiving cells of the blade feet and the cooling is not effective. EXPOSE DE L'INVENTION

[0013] The invention therefore aims to solve the aforementioned problem and to propose a rotor structure which allows the blade root to be axially locked inside the cavity, in both directions, i.e. upstream and downstream, while allowing efficient cooling of the radially internal cavity and the radially external cavity of the cavity.

[0014] To this end, the invention relates to a turbine rotor comprising: 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 recesses, each configured for receiving a blade root, each blade having a bilobed blade root and each recess comprising a radially internal cavity extending into a radially external cavity, an axial retaining ring for the blade roots, this retaining ring comprising a radially internal portion with notches and a solid radially external portion, an annular flange, fixed to the upstream side of the rotor disc so that its radially external end is in contact with the retaining ring, this annular flange being configured to provide a space with said rotor disc and comprising at least one air inlet orifice opening into said space, and each blade includes a receiving groove for the outer circumferential edge of said retaining ring.

[0015] In accordance with the invention: Each notch in the retaining ring is circumferentially delimited on one side and 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 disposed against the upstream face of the rotor disc, so that each of its notches is located opposite a cell of the rotor disc, so that cooling air can enter 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 disc.

[0016] Thanks to these features of the invention, the flange and the retaining ring cooperate to axially maintain the blade foot inside the receiving cavity of the rotor disc and thus prevent any movement of this blade upstream or downstream, while allowing efficient cooling of the internal and external cavities of the cavity respectively, thanks to the presence of the notches in the retaining ring.

[0017] According to other advantageous and non-limiting features of the invention, taken alone or in combination: The retaining ring comprises as many notches as the rotor disc has blade root reception holes. The rotor includes an annular seal, disposed between the radially outer end of the annular flange and the upstream face of the solid radially outer portion of said retaining ring. The annular flange comprises as many cooling ports as the rotor disc has holes. The annular flange has, overall, an axial arm and a radial arm; the axial arm is fixed to the rotor disc, and the radially outer end of said radial arm is in contact with the upstream face of the radially outer portion of said retaining ring. At least one air intake port is formed in the radial arm of the annular flange. The retaining ring comprises several ring sectors, arranged end to end circumferentially around the longitudinal axis of rotation.The height, taken along 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 along a radial direction, of the receiving cavity of a blade foot into which the notch opens.

[0018] The invention also relates to a turbomachine turbine, in particular a low pressure turbine, equipped with the aforementioned rotor.

[0019] The invention finally relates to a turbomachine comprising at least one such turbine. DESCRIPTION DES FIGURES

[0020] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which: there figure 1 represents a cavity in a rotor disc and a fir-tree-shaped blade root received in this cavity; the figure 2 is a partial perspective view of a rotor disc, blades, retaining ring and flange according to the invention; the figure 3 is a partial axial cross-sectional view of the rotor disc, a retaining ring blade, and the flange according to the invention; figure 4 is a perspective view of a portion of two ring sectors forming the retaining ring according to the invention; the figure 5 is a perspective view of a portion of the retaining ring according to the invention, arranged in front of a rotor disc. DESCRIPTION DETAILLEE DE L'INVENTION

[0021] By referring to figures 2 And 3 We can see a rotor 1 which comprises a rotor disk 2 and a plurality of radial blades 3, arranged around this rotor disk. The rotor disk 2 is driven in rotation about an axis of rotation X-X', which also constitutes its central longitudinal axis.

[0022] The rotor disk 2 has an upstream face 21 and an opposite downstream face 22.

[0023] In the rest of the description and claims, the expressions "radially internal" and "radially external" are to be taken into consideration with respect to the position of the X-X' axis.

[0024] Each blade 3 comprises a blade foot 30, which has a fir tree or bilobed shape. Each blade foot 30 thus comprises a radially external lobe 31 which extends in the radially internal direction by a radially internal lobe 32.

[0025] The rotor disc 2 further comprises at its periphery a plurality of axial sockets 23, each of which allows the reception of a blade foot 30 3. Each socket 23 opens radially outwards.

[0026] As explained previously, each alveolus 23 includes a radially external cavity 231 which opens outwards and 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 foot.

[0027] According to the invention, the rotor 1 also includes a retaining ring 4 and an annular flange 5, which will now be described in more detail.

[0028] Ring 4 provides axial retention for the feet 30 of the blades 3. As this is clearer on the figure 4 This ring 4 has a flat upstream face 40 and a flat downstream opposite face 41. Furthermore, this axial retaining ring 4 comprises a radially internal portion 42, provided with a plurality of notches 43, and a solid radially external portion 44. The radially external portion 44 is called "solid" because it does not have notches 43. In other words, the notches 43 do not extend to this portion.

[0029] The radially internal portion 42 also comprises a plurality of radial tabs 45, each tab 45 extending between two adjacent 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 on the figure 4 , each notch 43 extends radially, has a substantially U-shaped form and opens at the level of the inner circumferential edge of the ring 4. The tabs 45 allow the ring 4 to be pressed firmly against the rotor disc 2 and thus improve the seal between the two.

[0030] Advantageously, and as this appears more clearly on the figures 4 et 5 The tabs 45 may have a cutout 450 on their upstream face and near their radially internal end. Such a cutout 450 makes it possible to thin the internal end of the tab and reduce the overall weight of the ring 4.

[0031] In addition, ring 4 includes on its outer circumference a curved edge 46.

[0032] The retaining ring 4 can be a single-piece ring extending over 360° and may or may not be split. It can also be composed of several ring sectors, joined circumferentially end-to-end to form said ring. The number of sectors is not limited, but preferably it is between two and fifteen and is advantageously a divisor of the number of blades. By way of purely illustrative example, one can thus see on the figure 4 , two neighbouring ring sectors, referenced 4A and 4B.

[0033] The retaining ring 4 is positioned on the rotor disc 2, so that its flat downstream face 41 is in contact with the upstream face 21 of this disc and that its radially external part 44 is located opposite the radially external end of the holes 23, as can be seen more clearly in the figure 3 and also in such a way that its central axis is coaxial with the central longitudinal axis XX' of disk 2.

[0034] Furthermore, this retaining ring 4 is positioned so that each notch 43 is located opposite a socket 23, as is best shown in the figure 5 Preferably, the ring 4 has as many notches 43 as there are pits 23 on the rotor disc 2.

[0035] The tabs 45 do not contribute to the seal but are there to improve the contact between ring 4 and disc 2. Without these tabs, ring 4 would be more likely to move. The dimensions of each tab 45 are therefore adjusted accordingly.

[0036] By referring to the figure 5 , we can see that the tangential width (taken along a circumferential direction) L1 of a tongue 45 is less than the width L2, taken along a circumferential direction, between two adjacent alveoli 23 of the disk 2, so as not to obstruct the passage of cooling air through these alveoli 23. Preferably also, this tangential width L1 is greater than or equal to 5 millimeters (mm).

[0037] Furthermore, the height H of a tab 45 (which also corresponds to the height H of a notch 43), taken along a radial direction, is preferably greater than 2 mm. Preferably also, this height H is less than the overall height H1, taken along a radial direction, of the socket 23, since the part 44 of the ring 4 is located opposite the upper end of the radially external cavity 231 of the socket 23, as can be seen in the figure 3 As an example, the height of this cell 23 can reach 50 mm.

[0038] Finally, preferably, the dimensions of the notches 43, and in particular the width L3, taken along a circumferential direction, of a notch 43 is greater than or equal to the width, taken along a circumferential direction, of a cavity 23, so that when the retaining ring 4 is in place, the notches 43 do not obstruct the passage of air through the cavity 23 and allow the air to properly cool the radially internal cavities 232 and the radially external cavities 231.

[0039] Each blade 3 further includes a groove 33 for receiving part of the circumference of the retaining ring 4 or more precisely for receiving part of the outer circumferential edge 46 of the ring 4.

[0040] Advantageously, and as can be seen on the figure 3 , the blade 3 includes an upstream spoiler 34 which extends axially upstream and which is provided on its radially internal face with a radially internal lug 35. It is this radially internal lug 35 which is provided with said groove 33 and this groove 33 opens in the direction of the axis X-X'.

[0041] As can be seen on the figure 2 , when the different blades 3 are placed in the recesses 23 of the rotor disc 2, their respective upstream fins 34 touch.

[0042] The groove 33 is advantageously shaped and dimensioned so that the edge 46 is inserted into it without play. In other words, the groove 33 has, for example, a semi-circular cross-section in axial section, when the rim 46 is semi-circular, and this groove 33 is curved with the same radius of curvature as that of the ring 4.

[0043] Advantageously, anti-rotation fingers 47 are provided on the upstream face 40 of the ring, near the edge 46. As can be seen on the figure 5 , the anti-rotation finger 47 comes into contact with the radially internal leg 35 and cooperates with it to prevent the rotation of the ring 4 relative to the blades 3 and the rotor disc 2.

[0044] Preferably, ring 4 includes several anti-rotation fingers 47 or each sector of ring 4A, 4B includes two anti-rotation fingers, one for each direction of rotation.

[0045] As can be seen on the figure 3 , the annular flange 5 is configured to be positioned on the upstream side of the rotor disc 2 and to delimit with it a space E.

[0046] 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 includes at its radially external end 52 a projecting part which extends axially downstream.

[0047] 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 sealing gasket 6, preferably an O-ring.

[0048] In addition, the flange 5 includes at least one air inlet orifice 54, preferably provided in the radial arm 51. Preferably, the flange 5 includes several air inlet orifices 54 and even more preferably, as many orifices 54 as there are holes 23 on the rotor disc 2. Preferably, each orifice 54 is aligned with a hole 23 when the flange is in place.

[0049] The annular flange 5 is fixed on the rotor disc 2, so that its central axis is coaxial with the central longitudinal axis XX' of the disc 2 and so that its radially external end 52 is in contact with the retaining ring 4. In addition, when the sealing gasket 6, housed in the annular groove 53, is present, the flange 5 is fixed to the disc 2 so that its end 52 is in contact with the upstream face 40 of the solid radially external part 44.

[0050] Furthermore, the flange 5 is fixed to the rotor disc 2 by means of a fastening device 7. This fastening device 7 is, for example, a ring, which cooperates with the downstream end of the axial arm 50 of the flange 5 and with the rotor disc 2 to ensure fixation. Other fastening devices 7 could also be considered, for example, screw fastening.

[0051] Furthermore, it should be noted that when ring 4 is in several annular sectors, for example at least two, several projecting edges (or walls) 210 must then be provided on the upstream face 21 of the rotor disk 2, preferably as many edges as sectors. As can be seen on the figures 3 And 5 , these rims 210 are arranged so as to be radially inwards relative to the tabs 45, to block the latter and prevent the ring 4 from disengaging from the groove 33.

[0052] When the retaining ring 4 and the annular flange 5 are positioned on the rotor disc 2, as shown in the figure 3 , the cooling air coming from upstream (on the left of the figure 3 ) enters space E, through air intake ports 54, as represented by arrow i.

[0053] This cooling air can then flow into the radially internal cavity 232 of each alveolus 23, as shown by arrow ii, and also into the radially external cavity 231, as shown by arrow iii, thanks to the presence of the notches 43. For this purpose, it should be noted that on the figure 3 The respective outlines of the blade foot 30 and the cavity 23 have been deliberately represented as dashed lines, rotated by 90°. This representation is purely schematic and allows visualization of the height of the various lobes 31, 32 of the blade foot and the various cavities 231 and 232. In reality, the blade foot and the cavity obviously extend axially, as can be seen in the diagrams. figures 2 And 5 .

[0054] The annular flange 5 ensures the seal between the upstream of the flange 5 and the space E. This seal is also reinforced by the presence of the gasket 6, positioned against the radially external part 44 of the retaining ring 4 free of notches 43.

[0055] Furthermore, the flange 5 allows the calibration of the cooling air by sizing the air intake orifices 54 which are smaller than the notches 43.

[0056] Furthermore, the retaining ring 4 and the annular flange 5 cooperate to ensure the axial locking of the blade feet 30 in the recesses 23 of the disc 2. Indeed, the movement of the blade foot 30 downstream (to the right of the figure 3 ) or upstream (to the left on the figure 3 ) is prevented by the fact that the groove 33 of the blade 3 is blocked on the rim 46 of the ring 4, itself pressed against the upstream face 21 of the rotor disc 2 by the flange 5.

[0057] The device according to the invention thus makes it possible to ensure the cooling of the radially external cavities 231 of the alveoli 23 of the rotor disc 2, while ensuring the axial blocking of the blades 3.

[0058] Although not limiting, the rotor according to the invention finds particular application in turbomachine turbines and more particularly in low pressure turbines.

Claims

1. A turbine rotor (1), comprising: - a rotor disc (2) having a longitudinal axis of rotation (X-X') and a plurality of radial blades (3), this rotor disc (2) being provided on the periphery thereof with a plurality of axial slots (23) each configured to receive a blade root (30), each blade (3) having a blade root (30) of bilobed shape and each slot (23) comprising a radially inner cavity (232) extended by a radially outer cavity (231); - a ring (4) axially retaining the roots (30) of the blades, this retaining ring (4) comprising a radially inner portion (42) provided with recesses (43) and a solid radially outer portion (44); - an annular flange (5) secured on the upstream side of the rotor disc (2) so that the radially outer end thereof (52) is in contact with the retaining ring (4), this annular flange (5) being configured to form a space (E) with said rotor disc (2) and comprising at least one air-intake orifice (54) opening into said space (E), and each blade (3) comprising a groove (33) receiving the outer circumferential edge (46) of said retaining ring (4), this rotor being characterized : in that each recess (43) of the retaining ring (4) is circumferentially delimited on either side by two radial extensions (45) of the retaining ring (4), in that the width (L3),in circumferential direction, of a recess (43) is greater than or equal to the width, in circumferential direction, of a slot (23), and in that said retaining ring (4) is disposed against the upstream face (21) of the rotor disc (2) so that each of the recesses thereof (43) lies facing a slot (23) of the rotor disc (2), such that cooling air is able to enter via said at least one air-intake orifice (54) into said space (E) and to pass through the recesses (43) to reach the radially outer cavity (231) of the slots (23) of said rotor disc (2).

2. The turbine rotor (1) according to claim 1, characterized in that the retaining ring (4) comprises as many recesses (43) as the number of slots (23) on the rotor disc (2) receiving a blade root.

3. The turbine rotor (1) according to claim 1 or 2, characterized in that it comprises an annular seal (6), disposed between the radially outer end (52) of the annular flange (5) and the upstream face of the solid radially outer portion (44) of said retaining ring 4.

4. The turbine rotor (1) according to any of the preceding claims, characterized in that the annular flange (5) comprises as many cooling orifices (54) as there are slots (23) on the rotor disc (2).

5. The turbine rotor (1) according to any of the preceding claims, characterized in that the annular flange (5) generally has an axial branch (50) and a radial branch (51), in that the axial branch (50) is secured to the rotor disc (2) and the radially outer end (52) of said radial branch (51) is in contact with the upstream face of the radially outer portion (44) of said retaining ring (4), and in that said at least one air-intake orifice (54) is formed in the radial branch (51) of the annular flange (5).

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

7. The turbine rotor (1) according to any of the preceding claims, characterized in that the height (H), in radial direction, of each of the two extensions (45) disposed circumferentially on either side of a recess (43) is lower than the height (H1), in radial direction, of the slot (23) receiving a blade root, onto which the recess (43) opens.

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

9. A gas turbine engine characterized in that it comprises at least one turbine of a gas turbine engine according to claim 8.

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