Blade of a static turbomachine blade with improved attachment

Abstract

Blade of a static blade of a turbomachine with improved attachment Blade of a static blade of a turbomachine, comprising a support (11), an active straightening portion made of composite material, and a blade root (13) made of composite material extending between the support (11) and the active straightening portion (120). The blade (12) further comprises a vice (18) and at least one elastic means (19), the vice (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 arranged between the blade root (13) and a jaw (16, 11) of the jaw (18) among the first jaw (16) and the second jaw (11). Figure for the abstract: Fig. 3.

Description

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

[0001] The invention relates to turbomachines, in particular aeronautical turboshaft engines comprising a static rectifier with fixed blades made of woven composite material, possibly with variable pitch. The field of application of the invention is in particular that of aeronautical gas turbine engines. The invention is however applicable to other turbomachines. Prior art

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

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

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

[0005] In the context of the design and manufacture of composite material blades, the support to which the part is fixed is generally made of metallic material. The metallic part is a support capable of rotating in order to orient the composite part which is fixed above, and thus modify its incidence according to the variable timing of the part.

[0006] The main type of stress seen by the part concerns bending movements induced by its incidence generating vibration modes (vibration fatigue), but also a constant aerodynamic pressure according to its azimuthal position (static stress). Much greater amplitudes can be applied in the event of impacts (pieces of propeller, bird, tire, others...) in extreme events.

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

[0008] The radial attachment shown in [Fig. 1] is produced by holding a platform 2 of the blade root 3 in abutment against a metal support 4 using fixing means, for example two tightening 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 rectifier.

[0009] The tangential attachment shown in [Fig.2] is produced by holding the blade root 6 in a vice formed by two portions 7 projecting radially externally from the support 8, the vice being clamped by a tangential screw 9 passing through the portions 7 projecting radially externally and the blade root 6, the tangential screw 9 passing through them in a direction orthogonal to the radial direction DR.

[0010] In the context of static blading, the absence of rotation around the axis of the turbomachine is a disadvantage for the choice of the attachment. Indeed, on rotating blading, the centrifugal force resulting from the rotation is sufficient to press the blade root with considerable force into a cellular attachment. The blade is therefore held geometrically by the complementary shape of this cell and the blade root, generally in the form of a "dovetail".

[0011] For static blading, the absence of this rotation and therefore of centrifugal force prevents the use of this simple and well-known means of attachment. It is necessary to use a more conventional attachment, by clamping to form a radial attachment, or by a tangential attachment, as mentioned above. Statement of the invention

[0012] The invention aims to overcome the drawbacks 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 sustained in shear at the blade root during strong bending stress.

[0013] This object is achieved in a blade of a static blade 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 extending between the support and the active straightening portion.

[0014] According to a general characteristic of the invention, the blade further comprises a vice and at least one elastic means. The vice 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 root is held according to the first direction between the first jaw and the second jaw. The clamping means pass through the first jaw and the second jaw without passing through the blade root. Said at least one elastic means is arranged between the blade root and one jaw of the jaw among the first jaw and the second jaw.

[0015] When the blade is mounted on an annular rectifier, the vice forms a radial attachment holding the blade root and therefore the blade radially in position. The clamping provided by the clamping means provides sufficient force to hold the stator in place. This force is equivalent, in the case of a fan, to the centrifugal force which allows the fan blades to be held.

[0016] Clamping alone using the vice has a weakness. The attachment of the part is very stiff and has a shear damage mode in its root which appears following a strong bending stress. This bending can result from the aerodynamic pressure due to the static loading that the part undergoes, or it can result from the ingestion of a bird. When the part works in bending because of the aerodynamic pressure, the blade root and the radial jaw will maintain a significant stiffness making it possible to limit the deflection of the part.

[0017] The elastic means arranged between the blade root and the first jaw or between the blade root and the second jaw, makes it possible to modify the radial attachment to provide it with adaptive flexibility which will enable it to eliminate the problematic damage mode previously described.

[0018] The advantage of this attachment is that in the event of significant occasional stress such as the ingestion of birds or debris, the part will flex considerably and temporarily increase its flexibility thanks to the elastic means, which will limit the shearing in the root. Without the elastic means the blade would break because the stiffness of the blade root is too great.

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

[0020] According to a first embodiment of the blade, the jaw of the vice in contact with said at least one elastic means may comprise a recess inside which said at least one elastic means is arranged at least in part.

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

[0022] The elastic means may further comprise a contact plate disposed between the compression spring and the radially inner end of the blade root.

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

[0024] According to a fourth embodiment of the blade, the blade root may have a hooking portion and a joining portion, the joining portion of the blade root being directly in contact with the active straightening portion of the blade, and the blade root attachment portion having a width greater than the width of the blade root joining portion, the width being measured in a third direction orthogonal to the first direction and to the second direction.

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

[0026] According to a sixth embodiment of the blade, the support may be a pivot support intended to be fixed radially to an internal support shell of an annular rectifier.

[0027] The invention also relates to an annular rectifier 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.l], already presented, is a schematic sectional view of a fastener radial of a blade root according to the state of the art.

[0032] [Fig.2] [Fig.2], already presented, is a schematic sectional view of a radial attachment of a blade root according to the state of the art.

[0033] [Fig.3] [Fig.3] schematically represents a sectional view of an attachment of a blade root of a static rectifier according to a first embodiment of the invention.

[0034] [Fig.4] [Fig.4] schematically represents a sectional view of an attachment of a blade root of a static rectifier according to a second embodiment of the invention.

[0035] [Fig.5] [Fig.5] schematically represents a sectional view of an attachment of a blade root of a static rectifier according to a third embodiment of the invention. Description of the embodiments

[0036] In [Fig. 3] is illustrated a schematic 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 form 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 shell, an outer metal support shell, and a plurality of vanes 12 extending radially between the inner support shell and the outer support shell.

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

[0040] The support 11 is a movable support making it possible to modulate the orientation of the active rectifying portion 120 in a plane orthogonal to the radial direction DR. The movable support 11 is fixed to the internal support shell of the rectifier 10.

[0041] The blade root 13 comprises a hooking portion 14 and a joining portion 15. The joining portion 15 is located at a radially external end of the blade root 13. The joining portion 15, and therefore the radially external end of the blade root 13, are integral with the active straightening portion 120 of the blade 12.

[0042] The blade root 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 joining portion 15.

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

[0044] In a variant, the attachment portion 14 may be located between the radially internal end and the joining portion 15.

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

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

[0047] The blade 12 further comprises an elastic means 19 arranged between the blade root 13 and a jaw 11 or 16 of the vice 18.

[0048] In this embodiment, the elastic means is a compression spring 19 arranged 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 the spring could be provided in one of the surfaces of the clamping platform 16 in contact with the blade root 13.

[0050] In the illustrated embodiment, the elastic means 19 further comprises a contact plate 192 arranged between the compression spring 190 and the radially inner end of the blade root 13.

[0051] In [Fig.4] is illustrated a schematic sectional view of an attachment of a blade root of a static rectifier 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 flexible elastomer shim 194 in place of the compression spring 190 and the contact plate 192.

[0053] In [Fig.5] is illustrated a schematic sectional view of an attachment of a blade root of a static rectifier 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 root 13. This embodiment makes it possible to avoid a ball joint connection between the blade root 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 sustained in shear at the blade root during high bending stress.

Claims

Claims

1. A blade (12) of a static blade of a turbomachine, the blade (12) comprising, in a first direction (DR): - a metal support (11) intended to be connected to a hub of the turbomachine, - an active straightening portion (120) made of composite material intended to straighten a gas flow flowing in a second direction (DA) orthogonal to the first direction (DR), and - a blade root (13) made of composite material secured to 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 vice (18) and at least one elastic means (19), the vice (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) 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 root (13), the support (11) and the clamping means (17), and said at least one elastic means (19) being arranged between the blade root (13) and a jaw (16, 11) of the jaw (18) among the first jaw (16) and the second jaw (11).,

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

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

4. A blade (12) according to one of claims 1 or 2, wherein said at least one elastic means (19) comprises a flexible elastomer shim (194).

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

6. Blade (12) according to one of claims 1 to 5, in which the blade root (13) has a dovetail shape.

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

8. An annular rectifier (10) comprising a plurality of blades according to one of claims 1 to 7.

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

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

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

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