Blade of a static turbomachine blade with improved attachment

Abstract

A static turbine blade of a turbomachine with an improved attachment. A static turbine blade of a turbomachine, comprising a support (11), a straightening active portion made of composite material, and a blade root (13) made of composite material extending between the support (11) and the straightening active portion (120). The blade (12) further comprises a clamp (18) and at least one elastic means (19), the clamp (18) having a first jaw (16), a second jaw formed by the support (11), and clamping means (17) configured to bring the first jaw (16) closer to the second jaw (11). The blade root (13) is held between the first jaw (16) and the second jaw (11). The clamping means (17) pass through the first jaw (16) and the second jaw (11) without passing through the blade root (13).And said at least one elastic means (19) is disposed between the foot of the awl (13) and a jaw (16, 11) of the bit (18) between the first jaw (16) and the second jaw (11). Figure for the abbreviation: Fig. 3.

Description

Title of the invention: Blade of a static turbomachine blade with improved attachment technical field

[0001] The invention relates to turbomachinery, in particular aeronautical turboshaft engines comprising a static stator with fixed blades made of woven composite material, optionally with variable pitch. The field of application of the invention is notably that of aeronautical gas turbine engines. The invention is, however, applicable to other turbomachinery. Previous technique

[0002] In a turbomachine, the fixed blades of a rectifier have the role of a stator in a conventional compressor. Combined with the moving blades of a fan, or of a propeller for an unfaired turbomachine, they make it possible to straighten the airflow which has been accelerated by the moving fan blades and deflected by them.

[0003] In recent turbomachinery, large blade parts are increasingly made of organic matrix composite materials, because these materials allow, compared to metallic materials, a significant mass reduction with equivalent mechanical properties and / or a mechanical gain for an equivalent mass.

[0004] It is known to produce these parts by layering two-dimensional fibrous reinforcements subsequently densified with resin, or by three-dimensional weaving of a single preform which will subsequently be densified.

[0005] In the design and manufacture of composite material blades, the support to which the part is attached is generally made of metallic material. The metallic part is a support that can rotate in order to orient the composite part that is fixed above it, and thus modify its angle of incidence according to the variable positioning of the part.

[0006] The main type of stress experienced by the part concerns bending movements induced by its angle of incidence, generating vibrational modes (vibrational fatigue), but also a constant aerodynamic pressure depending on its azimuthal position (static stress). Much larger amplitudes can be applied in the event of impacts (propeller fragments, birds, tires, etc.) in extreme events.

[0007] The simplest means of fastening between a metal part and a composite part can be achieved by bolting. For this purpose, two types of fasteners are commonly used, the radial clamping fastener, shown schematically in [Fig. 1], and the tangential fastener shown schematically in [Fig. 2].

[0008] The radial attachment shown in [Fig. 1] is made by holding a platform 2 of the blade foot 3 against a metallic support 4 using fastening means, for example two clamping screws 5 passing through the platform 2 in a radial direction DR to be screwed into the support 4, the support 4 being fixed on a ferrule to form an annular straightener.

[0009] The tangential attachment shown in [Fig.2] is made by holding the blade foot 6 in a vise formed by two portions 7 in external radial projection of the support 8, the vise being tightened by a tangential screw 9 passing through the external radial projection portions 7 and the blade foot 6, the tangential screw 9 passing through them in a direction orthogonal to the radial direction DR.

[0010] In the context of a static blade, the absence of rotation around the turbine's axis is a disadvantage for the choice of fastening. Indeed, on a rotating blade, the resulting centrifugal force is sufficient to press the blade root into a socket with considerable force. The blade is therefore held geometrically by the complementary shape of this socket and the blade root, which is generally dovetail-shaped.

[0011] For a static blade, the absence of this rotation, and therefore of centrifugal force, precludes the use of this simple and well-known fastening method. A more conventional fastening method must be used, either by clamping to form a radial attachment, or by a tangential attachment, as mentioned above. Description of the invention

[0012] The invention aims to overcome the disadvantages mentioned above and to provide an alternative solution for attaching a fixed blade made of composite material, making it possible to reduce, or even eliminate, the risk of damage suffered in shear at the level of the blade foot during a high bending stress.

[0013] This objective is achieved at a blade of a static turbine blade assembly of a turbomachine, the blade comprising, in a first direction, a metal support, an active straightening portion made of composite material, and a blade root made of composite material. The metal support is intended to be connected to a hub of the turbomachine. The active straightening portion is intended to straighten a gas flow flowing in a second direction orthogonal to the first direction. The blade root is integral with the active straightening portion and extends between the support and the active straightening portion.

[0014] According to a general feature of the invention, the blade further comprises a vise and at least one elastic means. The vise has a first jaw, a second jaw formed by the support, and clamping means configured to bring the first jaw closer to the second jaw. The blade foot is held according to the The first direction is between the first jaw and the second jaw. The clamping means pass through the first jaw and the second jaw without passing through the jawbone. At least one elastic means is disposed between the jawbone and one jaw of the bit between the first and second jaws.

[0015] When the blade is mounted on an annular straightener, the vise forms a radial clamp that radially holds the blade root, and therefore the blade itself, in position. The clamping force provided by the clamping means is sufficient to hold the stator in place. This force is equivalent, in the case of a blower, to the centrifugal force that holds the blower blades in place.

[0016] Clamping the part using only a vise presents a weakness. The part's attachment is very stiff and exhibits a shear failure mode in its foot that appears following high bending stress. This bending can result from aerodynamic pressure due to the static load on the part, or it can result from the ingestion of a bird. When the part is subjected to bending due to aerodynamic pressure, the blade foot and the radial jaw will retain significant stiffness, thus limiting the part's deflection.

[0017] The elastic means disposed between the blade foot and the first jaw or between the blade foot and the second jaw, allows the radial attachment to be modified to offer it an adaptive flexibility which will allow it to eliminate the problematic mode of damage previously described.

[0018] The advantage of this attachment is that in the event of significant, localized stress, such as the ingestion of birds or debris, the part will flex considerably and temporarily increase its flexibility thanks to the elastic element, thus limiting shear stress in the foot. Without the elastic element, the blade would break because the stiffness of the blade foot is too great.

[0019] Preferably, the composite material is an organic matrix composite, CMO.

[0020] According to a first embodiment of the vane, the jaw of the vise in contact with said at least one elastic means may include a recess within which said at least one elastic means is disposed, at least in part.

[0021] According to a second embodiment of the blade, said at least one elastic means may include a spring, and preferably a compression spring.

[0022] The elastic means may further include a contact plate disposed between the compression spring and the radially internal end of the blade foot.

[0023] According to a third embodiment of the blade, said at least one elastic means may include a wedge made of flexible elastomer.

[0024] According to a fourth embodiment of the blade, the blade foot may have a gripping portion and a connecting portion, the connecting portion of the blade foot being in direct contact with the active righting portion of the blade, and the portion of the blade foot attachment having a width greater than the width of the junction portion of the blade foot, the width being measured along a third direction orthogonal to the first and second directions.

[0025] According to a fifth embodiment of the blade, the foot section may have a dovetail shape.

[0026] According to a sixth embodiment of the blade, the support can be a pivot support intended to be radially fixed to an internal support ferrule of an annular straightener.

[0027] The invention also relates to an annular straightener comprising a plurality of blades as defined above.

[0028] The invention also relates to a turbomachine turbine comprising an annular rectifier as defined above.

[0029] The invention also relates to a turbomachine compressor comprising an annular rectifier as defined above.

[0030] The invention also relates to a turbomachine comprising a turbine as defined above and / or a compressor as defined above. Brief description of the drawings

[0031] [Fig-1] Fig. 1, already presented, is a schematic cross-sectional view of a fastener radial of a blade foot according to the state of the art.

[0032] [Fig.2] The [Fig.2], already presented, is a schematic cross-sectional view of a radial attachment of a blade foot according to the prior art.

[0033] [Fig.3] The [Fig.3] schematically represents a cross-sectional view of a blade foot attachment of a static straightener according to a first embodiment of the invention.

[0034] [Fig.4] Fig.4 schematically represents a cross-sectional view of a blade foot attachment of a static straightener according to a second embodiment of the invention.

[0035] [Fig.5] Fig.5 schematically represents a cross-sectional view of a blade foot attachment of a static straightener according to a third embodiment of the invention. Description of the implementation methods

[0036] Figure 3 shows a schematic cross-sectional view of a foot attachment blade of a static rectifier according to a first embodiment of the invention.

[0037] The turbomachine rectifier 10, on which the blade 12 is mounted, is a static rectifier in the shape of a ring. The annular rectifier forms an annular stator defining an axial direction DA, a radial direction DR, and a circumferential direction Dc.

[0038] The rectifier 10 comprises an inner metal support ferrule, an outer metal support ferrule, and a plurality of blades 12 extending radially between the inner support ferrule and the outer support ferrule.

[0039] Each fixed blade 12 comprises a support 11, an active straightening portion 120, and a blade foot 13, the blade foot 13 being radially arranged between the support 11 and the active straightening portion 120.

[0040] The support 11 is a movable support allowing the orientation of the active rectifier portion 120 to be modulated in a plane orthogonal to the radial direction DR. The movable support 11 is fixed to the internal support ferrule of the rectifier 10.

[0041] The blade foot 13 comprises a hook portion 14 and a junction portion 15. The junction portion 15 is located at a radially external end of the blade foot 13. The junction portion 15, and therefore the radially external end of the blade foot 13, are integral with the active righting portion 120 of the blade 12.

[0042] The blade foot 13 comprises a section in a plane orthogonal to the axial direction Da with a width measured in a direction orthogonal to the axial direction and to the radial direction greater for the attachment portion 14 than that of the junction portion 15.

[0043] In the embodiment illustrated in [Fig. 3], the section comprises a dovetail section with its greatest width along the circumferential direction Dc located at the internal radial end. In other words, in this embodiment, the attachment portion 14 is located at the internal radial end.

[0044] In one variant, the hook portion 14 can be located between the radially internal end and the junction portion 15.

[0045] As illustrated in [Fig. 3], the blade 12 further comprises a metal clamping platform 16, and clamping screws 17 passing through the clamping platform 16 and the support 11 but not through the blade foot 13. The clamping platform 16 and the support 11 thus together form a vise 18 actuated by the clamping screws 17 and configured to radially clamp the gripping portion 14 of the blade foot 13 between the clamping platform 16 and the support 11. The clamping platform 16 forms a first jaw of the vise 18 and the support 11 forms a second jaw of the vise 18.

[0046] In one variant, the clamping screws 17 could be replaced by springs or bolts.

[0047] The blade 12 further includes an elastic means 19 disposed between the blade foot 13 and a jaw 11 or 16 of the vise 18.

[0048] In this embodiment, the elastic means is a compression spring 19 disposed in a housing 20, or a recess, provided in the support 11.

[0049] In one variant, there might be no housing. In another variant, the housing and spring could be provided in one of the surfaces of the clamping platform 16 in contact with the blade foot 13.

[0050] In the illustrated embodiment, the elastic means 19 further includes a contact plate 192 disposed between the compression spring 190 and the radially internal end of the blade foot 13.

[0051] Figure 4 illustrates a schematic cross-sectional view of a blade foot attachment of a static straightener according to a second embodiment of the invention.

[0052] The second embodiment of the invention differs from the first embodiment illustrated in [Fig.3] in that the elastic means 19 comprises a soft elastomer wedge 194 in place of the compression spring 190 and the contact plate 192.

[0053] Figure 5 illustrates a schematic cross-sectional view of a blade foot attachment of a static straightener according to a third embodiment of the invention.

[0054] The third embodiment of the invention differs from the second embodiment illustrated in [Fig.4] in that the elastic means 19 further comprise two additional elastomer wedges 192 arranged in two separate housings made in the clamping platform 16 and in contact with the blade foot 13. This embodiment makes it possible to avoid a ball joint between the blade foot 13 and the jaw 18.

[0055] The invention thus provides an alternative solution for attaching a fixed blade made of composite material, making it possible to reduce, or even eliminate, the risk of damage suffered in shear at the level of the blade foot during a high bending stress.

Claims

Demands

1. Blade (12) of a static turbine blade of a turbomachine, the blade (12) comprising along a first direction (DR): - a metallic support (11) intended to be connected to a hub of the turbomachine, - an active straightening portion (120) of composite material intended to straighten a gas flow flowing along a second direction (DA) orthogonal to the first direction (DR), and - a blade foot (13) of composite material integral with the active straightening portion and extending between the support (11) and the active straightening portion (120), characterized in that the blade (12) further comprises a clamp (18) and at least one elastic means (19), the clamp (18) having a first jaw (16), a second jaw formed by the support (11), and clamping means (17) configured to bring the first jaw (16) closer to the second jaw (11),the blade foot (13) being held in the first direction (DR) between the first jaw (16) and the second jaw (H), the clamping means (17) passing through the first jaw (16) and the second jaw (11) without passing through the blade foot (13), the support (11) and the clamping means (17), and said at least one elastic means (19) being disposed between the blade foot (13) and a jaw (16, 11) of the jaw (18) between the first jaw (16) and the second jaw (11).

2. Blade (12) according to claim 1, wherein the jaw (16, 11) of the vise (18) in contact with said at least one elastic means (19) has a recess (20) inside which said at least one elastic means (19) is disposed at least in part.

3. Blade (12) according to any one of claims 1 or 2, wherein said at least one elastic means (19) comprises a spring (190).

4. Blade (12) according to any one of claims 1 or 2, wherein said at least one elastic means (19) comprises a soft elastomer wedge (194).

5. Blade (12) according to any one of claims 1 to 4, wherein the blade foot (13) has a gripping portion (14) and a connecting portion (15), the connecting portion (15) of the blade foot (13) being in direct contact with the active righting portion (120) of the blade (12), and the attachment portion (14) of the blade foot (13) having a width greater than the width of the joining portion (15) of the blade foot (13), the width being measured along a third direction (Dc) orthogonal to the first direction (DR) and to the second direction (DA).

6. Blade (12) according to any one of claims 1 to 5, wherein the blade foot (13) has a dovetail shape.

7. Blade (12) according to any one of claims 1 to 6, wherein the support (11) is a pivot support intended to be radially fixed to an internal support ferrule of an annular straightener.

8. Annular straightener (10) comprising a plurality of blades according to any one of claims 1 to 7.

9. Turbomachine turbine comprising an annular rectifier (10) according to claim 8.

10. Turbomachine compressor comprising an annular compressor rectifier (10) according to claim 8.

11. Turbomachine comprising a turbine according to claim 9 and / or a compressor according to claim 10.

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