Movable blade for turbomachine turbine, comprising a strut equipped with radial blade retention protrusions

Abstract

The invention relates to a blade (20) for a rotating turbine wheel of an aircraft turbomachine, comprising successively a blade root (24), a strut (26), a platform (28), and a blade (30), the blade root being intended to be housed in a blade housing groove (66) provided on a peripheral portion (64) of a turbine disk (62), the housing groove (66) being defined between two directly consecutive disk teeth (70). According to the invention, on each of its two sides along the circumferential direction (32) of the blade, the strut (26) is provided with a radial blade retaining protrusion (50), each protrusion comprising a thrust surface (52) oriented radially inward and intended to cooperate with a radially outward surface of a disk tooth. Figure 3.

Description

Title of the invention: Moving blade for a turbomachine turbine, comprising a stilt equipped with radial blade retaining protrusions Technical field

[0001] The invention relates to the field of moving turbine blades for turbomachines, preferably for aircraft turbomachines. It relates more particularly to the means implemented to ensure the radial retention of the blades relative to the turbine disk, in order to prevent certain blades from moving towards the axis of the wheel too significantly when stopped and under the effect of gravity.

[0002] The invention applies to any type of turbomachine, such as for example a turbojet or a turboprop. STATE OF PRIOR ART

[0003] In an aircraft turbomachine, the moving turbine wheels are generally made using a disc, on the periphery of which turbine blades are mounted. The gas circulation vein is delimited radially inwards by platforms provided on the blades, near their roots.

[0004] The blades have already been the subject of numerous developments, and an example of design is for example known from document FR 2 954 797 AL

[0005] In operation, it is known to radially retain each moving blade using its root, by housing it in a groove in the periphery of the turbine disk. To do this, the root is generally equipped with two circumferentially opposite bearing surfaces, respectively bearing against the two teeth of the peripheral part of the disk which delimit between them the groove receiving the root. Thanks to these supports resulting from the centrifugal force, each blade is in a first configuration of radial retention by its root, preventing it from escaping radially outwards relative to the turbine disk.

[0006] When the turbomachine is not in operation, that is to say when the rotor is at a standstill, the moving blades of the upper part of the blade ring can fall under the effect of gravity, that is to say move towards the axis of the wheel. In the absence of means to stop this radial movement towards the inside, each blade concerned can see its root come into abutment in the bottom of the groove of the periphery of the disc. If it is too great, this radial movement of the blade can prove problematic in that it is likely to lead to a circumferential misalignment of the blade heads, with the possible consequence of a detrimental overlap of these heads when the turbine is next put into operation. bomachine.

[0007] To avoid this risk, it is known to provide two low walls arranged on either side of the blade's Péchasse, in the axial direction thereof. Each low wall originates from the platform and extends radially inwards until it is very close to the teeth of the peripheral part of the disc.

[0008] Although these walls are satisfactory in that they make it possible to limit the radial displacement of certain blades when the turbomachine is stopped, they nevertheless constitute a solution which significantly penalizes the overall mass of the blade. Summary of the invention

[0009] To at least partially address the drawback mentioned above, the invention firstly relates to a blade for a mobile turbine wheel of a turbomachine, preferably for an aircraft turbomachine, the mobile wheel being intended to be centered on an axis, and the blade successively comprising, in a radial direction of height of the blade relative to this axis, a blade root, a stilt, a platform, as well as a blade, the blade root being intended to be housed in a blade housing groove provided on a peripheral part of a turbine disk of the mobile wheel, said housing groove being defined between two directly consecutive disk teeth in a circumferential direction around the aforementioned axis,

[0010] the platform comprising a first surface as well as a second surface opposite the first in the height direction, the first surface, from which the blade extends, being intended to delimit a gas circulation vein, and the second surface, from which Péchasse extends, partly delimiting a first and a second cavity arranged on either side of Péchasse in the circumferential direction.

[0011] According to the invention, on each of its two sides in the circumferential direction, Péchasse is provided with a radially retaining protrusion of the blade, each protrusion comprising a stop surface oriented radially inwards and intended to cooperate with a radially external surface of a disc tooth.

[0012] With the solution proposed by the present invention, the radial retention of the blade, towards the inside, is advantageously achieved using simple protrusions fitted to Péchasse. These protrusions remain simple to produce, reliable, and contribute to limiting the overall mass of the blade in comparison with the wall solutions known from the prior art.

[0013] Furthermore, the reduction in mass caused by the implementation of the protrusions, associated with the removal of all or part of the walls on the blade, leads to a reduction in the mechanical stresses exerted on the blade root during operation. This also makes it possible to limit the dimensioning of the blade root, as well as that of the teeth of the peripheral part of the turbine disc.

[0014] The invention preferably comprises at least any one of the following optional features, taken alone or in combination.

[0015] Preferably, each radial retaining protrusion of the blade has a shape that narrows as it moves away circumferentially from Péchasse, for example a generally triangular shape. Other shapes are nevertheless conceivable, such as a bead shape, without departing from the scope of the invention.

[0016] Preferably, each radial retaining protrusion of the blade extends over all or part of the axial length of Péchasse.

[0017] Preferably, each of the first and second cavities is also delimited in part, in an axial direction of the blade, by a first and a second connecting wall, the blade also comprising an upstream spoiler and a downstream spoiler, both spaced from the platform in the height direction, the first connecting wall connecting the upstream spoiler to an upstream axial end of the platform, and the second wall connecting the downstream spoiler to a downstream axial end of the platform, each radial retaining protrusion of the blade being arranged radially between the upstream and downstream spoilers, and the blade root.

[0018] Preferably, the blade further comprises a first and a second stiffening wall extending respectively from the upstream spoiler and the downstream spoiler, in the direction of the blade root, the first and second stiffening walls also each participating in delimiting the first and second cavities, and each radial retaining protrusion of the blade is arranged radially between the stiffening walls and the blade root.

[0019] The invention also relates to a mobile turbine wheel for an aircraft turbomachine, comprising a turbine disk having a peripheral part provided with grooves for housing blades following one another in a circumferential direction of the wheel, the latter also comprising a plurality of blades such as that described above, the root of each blade being housed in one of the grooves of the peripheral part of the disk.

[0020] Preferably, in a first configuration of radial retention of the blade by its root, radially inwards relative to the turbine disc, each stop surface defines a clearance with the radially outer surface of its associated disc tooth, the clearance being for example between 0.10 and 0.15 mm.

[0021] Preferably, in a second configuration of radial retention of the blade by the protrusions, radially outwardly relative to the turbine disc, each abutment surface defines, with the radially outer surface of its associated disc tooth, a contact zone extending over a circumferential length by example greater than or equal to 1 mm.

[0022] The invention also relates to a turbomachine turbine comprising at least one moving wheel as described above, the turbine preferably being a low pressure turbine, but alternatively being able to be a high pressure turbine.

[0023] Finally, the invention relates to an aircraft turbomachine comprising at least one such turbine, the turbomachine preferably being a double-flow, double-spool turbojet.

[0024] Other advantages and characteristics of the invention will appear in the detailed non-limiting description below. Brief description of the drawings

[0025] This description will be made with regard to the attached drawings among which;

[0026] [Fig.l] represents a schematic axial sectional view of a twin-turbojet flow according to the invention;

[0027] [Fig.2] represents a perspective view of a moving turbine blade of the turbo reactor shown in [Fig.l], and in the form of a preferred embodiment of the invention;

[0028] [Fig.3] represents a partial and enlarged perspective view of the blade shown in the preceding figure;

[0029] [Fig.4] represents a front view of a part of a turbine wheel, comprising blades such as that shown in Figures 2 and 3;

[0030] [Fig.5] is a further enlarged front view of a portion of the wheel shown in [Fig.4], with one of the wheel blades shown in a first radially retained configuration by its root; and

[0031] [Fig.6] is a front view similar to that of [Fig.5], with the same blade shown in a second radial retention configuration by the protrusions equipping Péchasse with this blade. DETAILED PRESENTATION OF IMPLEMENTATION METHODS

[0032] Referring firstly to [Fig.l], there is shown an aircraft turbomachine 1, according to a preferred embodiment of the invention. This is a double-flow, double-spool turbojet. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0033] The turbomachine 1 has a longitudinal axis 2 around which its various components extend. It comprises, from upstream to downstream along a main direction 5 of flow of the gases through this turbomachine, a fan 3, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 11, a high-pressure turbine 7 and a low-pressure turbine 8.

[0034] Conventionally, after passing through the fan, the air divides into a central primary flow 12a and a secondary flow 12b which surrounds the primary flow. The primary flow 12a flows in a main gas circulation vein 14a passing through the compressors 4, 6, the combustion chamber 11 and the turbines 7, 8. The secondary flow 12b flows in a secondary vein 14b delimited radially outwards by a motor casing, surrounded by a nacelle 9.

[0035] Figures 2 and 3 represent a moving blade 20 according to a preferred embodiment of the invention, this blade 20 being intended to equip a moving wheel of any one of the turbines 7 and 8, and in particular the low pressure turbine 8. The moving wheel is, in a conventional manner, centered on the axis 2.

[0036] The elements of the blade 20 will be presented in the order as they appear successively according to the direction of the height 22 of this blade, from bottom to top, or from the inside to the outside since this direction of the height 22 also corresponds to the radial direction of the blade and of the moving turbine wheel in which this blade is intended to be integrated.

[0037] Conventionally, the blade 20 comprises a blade root 24, a stilt 26, a platform 28, a blade 30 constituting the aerodynamic part of the blade, and possibly a head structure 31 comprising another platform.

[0038] The blade root 24 adopts an external shape called a “fir tree” or “bulb”, allowing its insertion into a corresponding blade housing groove of a turbine disk intended to carry the moving blades. The stilt 26 usually has a small thickness in a circumferential direction 32 of the blade and the wheel, while the platform 28 also extends on either side of the stilt 26 in this same circumferential direction 32.

[0039] More precisely, the platform 28 can extend circumferentially beyond the intrados 34 and the extrados 36 of the blade 30, and can also extend beyond a leading edge 38 and a trailing edge 40 of the blade, in an axial direction 42 of the blade and of the wheel into which this blade is intended to be integrated.

[0040] With its outer surface 29a, called the first surface from which the blade 30 extends in the direction 22, the platform 28 delimits radially inwards the main gas circulation vein 14a.

[0041] With its inner surface 29b, called the second surface opposite the first surface 29a in the direction 22, and from which Péchasse 26 extends in this same direction substantially in the extension of the blade 30, the platform 28 delimits radially towards the outside a first cavity 33a as well as a second cavity 33b, arranged on either side of Péchasse 26 in the direction 32.

[0042] The platform 28 has an upstream axial end 35a, as well as a downstream axial end 35b. A first connecting wall 37a extends from the end upstream axial end 35a of the platform, radially inwards and parallel or substantially parallel to the directions 22, 32, to an upstream spoiler 40a projecting axially upstream. Similarly, a second connecting wall 37b extends from the downstream axial end 35b of the platform, radially inwards and parallel or substantially parallel to the directions 22, 32, to an upstream spoiler 40b projecting axially downstream.

[0043] The first connecting wall 37a partially delimits, axially upstream, each of the two cavities 33a, 33b provided under the platform 28. Similarly, the second connecting wall 37b also partially delimits, axially downstream, each of these two cavities 33a, 33b.

[0044] The spoilers 40a, 40b are thus offset radially inwards relative to the platform 28, being brought closer to the foot 24. A connection radius is preferably provided at the junction between each spoiler 40a, 40b and its associated connection wall 37a, 37b, and the same is true between each of these walls 37a, 37b and the platform 28.

[0045] From the upstream spoiler 40a, a first stiffening wall 42a may be provided extending radially inwards and parallel or substantially parallel to the directions 22, 32, over a limited height. The inner edge of this first stiffening wall 42a is located at a large radial distance from the foot 24, and therefore only axially covers a radially outer part of Péchasse 26.

[0046] Similarly, from the downstream spoiler 40b, a second stiffening wall 42b may be provided extending radially inwards and parallel or substantially parallel to the directions 22, 32, also over a limited height.

[0047] The stiffening walls 42a, 42b, also called “low walls”, may be located respectively in the radial extensions of the connecting walls 37a, 37b, or else be slightly offset axially from the latter, as shown in Figures 2 and 3.

[0048] The first stiffening wall 42a partially delimits, axially upstream, each of the two cavities 33a, 33b provided under the platform 28, just as the second stiffening wall 42b also partially delimits, axially downstream, each of these two cavities 33a, 33b.

[0049] The first cavity 33a remains open circumferentially in the direction opposite to Péchasse 26, while it also remains open radially in the direction opposite to the platform 28. In the circumferential direction 32, the first cavity 33a thus opens at a first circumferential opening 44a referenced in [Fig. 3]. This first opening 44a is delimited by a first junction zone 46a with the second cavity 33b of a blade directly consecutive on the wheel, as is known to those skilled in the art. The first junction zone 46a located at a low circumferential end of the blade, and has a general shape of an inverted U, open radially inwards.

[0050] One of the particularities of the invention lies in the absence of the first and second stiffening walls 42a, 42b under the spoilers, or in the fact that they are maintained but at a low height, so as to considerably reduce their mass. In the bare part of Péchasse 26, not covered axially by the elements 37a, 42a, 37b, 42b, another particularity of the invention consists in providing that on each of its two sides in the circumferential direction 32, this stilt 26 is provided with a protrusion 50 for radially retaining the blade.

[0051] Each of the two protrusions 50 comprises a stop surface 52 oriented radially inwards, and intended to cooperate with a radially external surface of one of the two disc teeth defining the groove in which the root 24 of the blade concerned is housed, as will be described later.

[0052] In this preferred embodiment, each radially retaining protrusion 50 of the blade has a shape that narrows as it moves away circumferentially from Péchasse 26, adopting a generally triangular or beaded shape. Each protrusion 50 is preferably made in one piece with Péchasse, extending over a limited circumferential length, strictly less than that of the aforementioned elements 37a, 37b, 40a, 40b, 42a, 42b, and for example identical or similar to that of the circumferential length of the part of the foot 24 most extended in the direction 32. It also extends over an axial length corresponding for example to the entire axial length of Péchasse 26, as has been shown in FIGS. 2 and 3. Alternatively, each protrusion 50 could extend only over a part of the axial length of Péchasse 26, for example by being formed by axial sections spaced axially from each other.

[0053] Each radial retaining protrusion 50 is arranged radially between, on the one hand, the radially inner edges of the stiffening walls 42a, 42b, and on the other hand the upper part of the blade root 24, while remaining radially distant from each of these elements 42a, 42b, 24. Furthermore, each radial retaining protrusion 50 extends axially between the stiffening walls 42a, 42b, and therefore also between the spoilers 40a, 40b.

[0054] [Fig.4] shows a part of a turbine wheel 60, comprising a disc 62 centered on the axis 2 and equipped with a peripheral part 64 provided with axial grooves 66 for housing the blades 20. The axial grooves 66 follow one another in the circumferential direction 32.

[0055] The wheel 60 also comprises a crown of blades 20 of the design of the type described above, with the root 24 of each blade being housed in one of the grooves 66 of the peripheral part 64 of the disc.

[0056] In [Fig. 5], the blade 20 is shown in a first configuration of radial retention by its root 24, this configuration being observed in operation when the centrifugal force causes the blade root 24 to press radially against an inner surface 72 of teeth 70. These teeth 70 are those which form the peripheral part 64 of the disc, extending radially outwards and defining between them, in the direction 32, the grooves 66 for housing the blade roots.

[0057] Thus, the blade root 24 is equipped with two circumferentially opposite bearing surfaces 74, which, in operation, respectively bear against the two surfaces 72 of two directly consecutive teeth in the direction 32, and which delimit between them the axial groove 66 receiving this root. Thanks to these supports resulting from the centrifugal force, each blade is in the first radial retention configuration by its root 24, preventing it from escaping radially outwards relative to the turbine disk 62. The blade 20 is designed so that in this first radial retention configuration, a small radial clearance 76 remains between the abutment surface 52 of each protrusion 50, and the radially outer surface 78 of its associated disk tooth 70 which it faces. This clearance 76 is preferably between 0.10 and 0.15 mm.

[0058] In [Fig. 6], the blade 20 is shown in a second radial retention configuration by its protrusions 50. This second configuration is observed when the turbomachine is not in operation, that is to say when it is stopped, and the blades 20 of the upper part of the blade ring can fall under the effect of gravity, and approach the axis of the wheel. This movement is limited to the consumption of the radial clearance 76, described with reference to [Fig. 5]. Once this clearance 76 has been consumed and the protrusions 50 have come into contact with the two teeth 70, each stop surface 52 defines, with the radially outer surface 78 of its associated disc tooth 70, a contact zone / interface extending over a circumferential length 80 greater than or equal to 1 mm.This also causes the bearing surfaces 74 of the blade root 24 to shift radially from the inner surfaces 72 of the teeth 70, leaving a small clearance 82 between them.

[0059] Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims.

Claims

Claims

1. Mobile wheel (60) of an aircraft turbomachine turbine, comprising a turbine disk (62) having a peripheral portion (64) provided with grooves (66) for housing blades succeeding one another in a circumferential direction (32) of the wheel, the latter also comprising a plurality of blades (20), the root (24) of each blade being housed in one of the grooves (66) of the peripheral portion (64) of the disk, each blade successively comprising in a radial direction (22) of height of the blade relative to the axis (2), a blade root (24), a stilt (26), a platform (28), as well as a blade (30), said housing groove (66) being defined between two directly consecutive disk teeth (70) in a circumferential direction (32) around the axis (2), the platform (28) comprising a first surface (29a) as well as a second surface (29b) opposite the first in the radial direction (22), the first surface (29a),from which the blade (30) extends, being intended to delimit a gas circulation vein (14a), and the second surface (29b), from which Péchasse (26) extends, partly delimiting a first (33a) and a second cavity (33b) arranged on either side of Péchasse (26) in the circumferential direction (32), characterized in that on each of its two sides in the circumferential direction (32), Péchasse (26) is provided with a protrusion (50) for radially retaining the blade, each protrusion (50) comprising a stop surface (52) oriented radially inwards and intended to cooperate with a radially external surface (78) of a disc tooth (70).,

2. Wheel according to claim 1, characterized in that each radially retaining protrusion (50) of the blade has a shape which narrows as it moves away circumferentially from Péchasse (26), for example a generally triangular shape.

3. Wheel according to claim 1 or 2, characterized in that each radial retaining protrusion (50) of the blade extends over all or part of the axial length of Péchasse (26).

4. Wheel according to any one of the preceding claims, characterized in that each of the first and second cavities (33a, 33b) is also partially delimited, in an axial direction (42) of the blade, by a first (37a) and a second connecting wall (37b), the blade also comprising an upstream spoiler (40a) and a downstream spoiler (40b), both spaced from the platform (28) in the radial direction (22), the first connecting wall (37a) connecting the upstream spoiler (40a) to an upstream axial end (35a) of the platform, and the second wall (37b) connecting the downstream spoiler (40b) to a downstream axial end (35b) of the platform, each radially retaining protrusion (50) of the blade being arranged radially between the upstream and downstream spoilers (40a, 40b), and the blade root (24).

5. Wheel according to claim 4, characterized in that the blade further comprises a first (42a) and a second stiffening wall (42b) extending respectively from the upstream spoiler (40a) and the downstream spoiler (40b), in the direction of the blade root (24), the first and second stiffening walls (42a, 42b) also each participating in delimiting the first and second cavities (33a, 33b), and in that each radial retaining protrusion (50) of the blade is arranged radially between the stiffening walls (42a, 42b), and the blade root (24).

6. A movable wheel according to any one of the preceding claims, characterized in that in a first configuration of radial retention of the blade by its root (24), radially inwards relative to the turbine disc (62), each stop surface (52) defines a clearance (76) with the radially outer surface (78) of its associated disc tooth (70).

7. A movable wheel according to any one of the preceding claims, characterized in that in a second configuration of radial retention of the blade by the protrusions (50), radially outwardly relative to the turbine disc (62), each abutment surface (52) defines, with the radially outer surface (78) of its associated disc tooth (70), a contact zone extending over a circumferential length (80).

8. Turbine (8) of a turbomachine comprising at least one moving wheel (60) according to any one of the preceding claims, the turbine preferably being a low pressure turbine.

9. Aircraft turbomachine (1) comprising at least one turbine (8) according to claim 8, the turbomachine preferably being a double-flow, double-spool turbojet.

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