VARIABLE PITCH STATOR BLADE FOR AN AIRCRAFT TURBOMACHINE

Abstract

Variable-pitch stator vane (30) for an aircraft turbomachine, comprising: - a blade (32) comprising a lower surface (32a) and an upper surface (32b), as well as a leading edge (32c) and a trailing edge (32d), the leading edge (32c) of the blade (32) comprising serrations (35) formed by alternating teeth (35a) and hollows (35b) along the leading edge (32a), - a platform (34) connected to one end of the blade (32) and defining a blade setting axis (A), the blade (32) comprising: - a first body (36) defining the trailing edge (32d) of the blade (32), and - a second body (38) which defines at least a portion of the leading edge (32c) of the blade (32) and which is mounted to move relative to the first body (36), along the setting axis (A). Figure for abstract: Figure 4

Description

Title of the invention: VARIABLE-PITCH STATOR VANE FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a variable-pitch stator blade for an aircraft turbomachine. Technical approval plan

[0002] The state of the art includes in particular document FR-A1-3 073 017.

[0003] An aircraft turbomachine conventionally comprises a gas generator which drives at least one propeller. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the rotor of the propeller for its rotational drive.

[0004] A propeller can be shrouded. This is the case for a fan in a turbomachine of the turbojet or turbofan type, for example.

[0005] A propeller can be unducted. This is the case for a turboprop, for example.

[0006] A propeller comprises a hub and an annular row of blades which are mounted all around the hub. The blades can be fixed and therefore have a fixed angular position around their axes of elongation.

[0007] In the context of the present invention, the blades are on the contrary variable pitch, that is to say they are capable of being moved in rotation around axes called pitch axes, which generally extend along the axes of elongation of the blades. The pitch axes may be radial axes relative to the axis of rotation of the propeller.

[0008] A variable-pitch rotor blade conventionally comprises a blade having a lower surface and an upper surface, as well as a leading edge and a trailing edge, and a platform connected to one end of the blade and defining the pitch axis of the blade. The platform is generally mounted in an orifice in the hub and centered and guided in rotation in this orifice around the pitch axis.

[0009] It is known to produce such blades from metallic, ceramic or composite material. A well-known composite material for a variable-pitch rotor blade comprises a body based on woven carbon fibers which is embedded in a polymer matrix based on epoxy, for example. The leading edge of the blade can be reinforced by a bonded metal shield.

[0010] The evolution of the performance of turbomachines tends towards the increase of their dilution ratio, which is mainly achieved by the increase of the diameter of the propellers and therefore of the length and mass of their blades.

[0011] In addition, a so-called slow and high bypass ratio propeller comprises a reduced number of blades whose chord is increased to improve the propulsive efficiency of the turbomachine.

[0012] In the case of a shrouded propeller, the nacelle surrounding the propeller includes an internal acoustic treatment which makes it possible to reduce noise emissions outside the turbomachine.

[0013] In the case of an unducted propeller, other solutions must be found for reducing propulsive noise. This is particularly the case for the turbomachine illustrated in [Fig.l]. This turbomachine 10 comprises a propeller 12 upstream, which comprises variable-pitch rotor blades 14, and a rectifier 16 downstream, which comprises stator blades 18 also with variable pitch.

[0014] To remedy the problem of noise emission, a noise reduction technology already known on fans and inspired in particular by the wings of nocturnal birds of prey consists of arranging serrations 20 on the trailing edges of the rotor blades 14 or on the leading edges of the stator blades 18 (figures 2 and 3).

[0015] Serrations 20 of a leading or trailing edge are formed by alternating teeth 20a and hollows 20b along this edge. The serrations can cause variations in the chord of the blade as a function of the radial height, with variable thicknesses and a very thin trailing or leading edge.

[0016] The teeth 20a are defined so as to reduce noise in the average emission spectrum without unduly worsening other frequencies at other engine speeds.

[0017] The angular setting of the blades implies variable acoustics of the blades depending on the engine speed and the orientation of the blades.

[0018] It has been found that, in most engine speeds, the serrations make it possible to reduce the noise emitted. However, a significant increase in the noise emitted has also been observed when the blades are set in reverse or thrust reversal mode. In the case of a rotor blade, the serrations of the trailing edge are oriented upstream in reverse mode, which greatly disrupts the aerodynamic flow. The serrations are then counterproductive.

[0019] The thrust reversal phase is a phase which, on the contrary, should be as quiet as possible because it generally takes place in a nearby urban environment.

[0020] Another disadvantage of the prior art is related to the fact that the serrations cannot be manufactured with the same material as the woven or ceramic blades because the serrations are too thin, and they would be too fragile and in particular brittle.

[0021] For metal blades, the problem comes from the risk of tearing of the serrations as well as the complexity of producing these serrations which leads to significant rejects due to geometric defects.

[0022] The present invention provides a solution to at least some of the problems of the prior art, which is simple, effective and economical. Summary of the invention

[0023] The invention relates to a variable-pitch stator blade for an aircraft turbomachine, this blade comprising:

[0024] - a blade comprising a lower surface and an upper surface, as well as a leading edge and a trailing edge, the leading edge of the blade having serrations formed by alternating teeth and hollows along the leading edge,

[0025] - a platform connected to one end of the blade and defining a setting axis of dawn,

[0026] characterized in that the blade comprises:

[0027] - a first body made of metallic or composite material defining the trailing edge of the blade, and

[0028] - a second body defining at least a portion of the leading edge of the blade and comprising at least part of the clamps, the second body being mounted to move relative to the first body, along the wedging axis.

[0029] The invention thus proposes dividing the blade of the stator vane into two parts, called bodies. The first body of the blade is made of metallic or composite material and comprises the trailing edge of the blade. The second body of the blade may be made of a material different from that of the first body. This second body defines at least part of the leading edge and comprises all or part of the serrations. The mobility of the second body relative to the first body makes it possible to vary the position of the serrations on the blade, in particular along the pitch axis.

[0030] The invention makes it possible, for example, to integrate variability in the radial position of the teeth as a function of the engine speed as well as the aerodynamic pressure forces exerted by the air flow in operation.

[0031] The blade according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another: - the second body defines the entire leading edge of the blade and includes all the serrations; - the second body extends over the entire longitudinal extent of the blade along the pitch axis; - the second body is slidably mounted on the first body; - the second body defines an upstream part of the intrados and the extrados of the pale ; - the second body comprises at least one actuating finger on the side of said platform; - said at least one actuating finger has an elongated shape along a direction of movement of the second body relative to the first body; - the platform comprises at least one orifice crossed by said at least one actuating finger; - the leading edge of the blade is a double leading edge which comprises two adjoining leading edge walls located next to each other, each of these leading edge walls comprising serrations formed by an alternation of teeth and hollows along the leading edge, each of the leading edge walls being movable relative to the first body independently of the other of the leading edge walls; the double leading edge makes it possible to reduce the noise emitted in an optimal manner, whatever the engine speed; - the two leading edge walls are respectively connected to two actuating fingers which are parallel and located next to each other; - the platform comprises two orifices crossed respectively by the two actuating fingers;

[0032] — at least some of the teeth include internal cavities; the cavities allow the dynamic behavior of the teeth to be modified during operation;

[0033] — at least some of the internal cavities are empty;

[0034] — at least some of the internal cavities contain weights;

[0035] — the or each actuating finger is located outside the blade.

[0036] The present invention also relates to an assembly comprising a blade as described above and a stator casing, the stator casing being fixed and the blade being mounted on the stator casing so that its platform is movable in rotation around the setting axis with respect to the casing.

[0037] The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0038] - the housing comprises at least one cam surface which cooperates with one end free of the or each actuating finger so that a rotation of the platform around the wedging axis causes a translation of the actuating finger and a displacement of the second body relative to the first body;

[0039] - said at least one cam surface is capable of cooperating with the two fingers actuation so as to impose two different positions on the leading edge walls with respect to the first body.

[0040] The invention further relates to a turbomachine for an aircraft, comprising a rotor equipped with blades such as described above. Brief description of the figures

[0041] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0042] [Fig-1] [Fig.l] is a schematic perspective view of a turbomachine with unducted propeller and an unducted stator, the propeller and stator having variable pitch blades;

[0043] [Fig.2] [Fig.2] is a schematic view of a variable pitch rotor or propeller blade;

[0044] [Fig.3] [Fig.3] is a schematic view of a variable-pitch stator or rectifier blade;

[0045] [Fig.4] [Fig.4] is a schematic view of a variable-pitch stator or rectifier blade, according to one embodiment of the invention;

[0046] [Fig.5] [Fig.5] is a sectional view along line VV of [Fig.4];

[0047] [Fig.6] [Fig.6] is a partial schematic perspective view of the stator blade of [Fig.4], and shows a position of the serrations of this blade;

[0048] [Fig.7] [Fig.7] is another partial schematic perspective view of the stator blade of [Fig.4], and shows another position of the serrations of this blade; and

[0049] [Fig.8] [Fig.8] is a view similar to that of [Fig.4] and shows the position of the serrations of [Fig.7]. Detailed description of the invention

[0050] Figures 1 to 3 have been described in the above.

[0051] The invention relates to a variable-pitch stator blade for an aircraft turbomachine, which may be the turbomachine of [Fig.l] or another turbomachine.

[0052] [Fig. 4] illustrates a first embodiment of a stator blade 30 according to the invention. It is a variable-pitch stator blade 30 for an aircraft turbomachine, which comprises:

[0053] - a blade 32 comprising a lower surface 32a and an upper surface 32b, as well as an edge 32c leading edge and a 32d trailing edge, and

[0054] - a platform 34 connected to one end of the blade 32 and defining an axis A of dawn setting 30.

[0055] The leading edge 32c of the blade 32 comprises serrations 35 formed by an alternation of teeth 35a and hollows 35 along the leading edge.

[0056] The particularity of the dawn 30 is that its blade 32 comprises:

[0057] - a first body 36 made of metallic or composite material defining the edge of leak 32d of blade 32, and

[0058] - a second body 38 defining at least a portion of the leading edge 32c of the blade 32 and comprising at least part of the clamps 35, the second body 38 being mounted to move relative to the first body 36, along the wedging axis A.

[0059] As seen in the drawing, the platform 34 may be made of the first material. The first body 36 and the platform 34 may be made monolithically.

[0060] In the example shown, the second body 38 defines the entire leading edge 32c of the blade 32 and comprises all of the serrations 35.

[0061] The second body 38 can extend over the entire longitudinal extent of the blade 32 along the pitch axis A, or over at least 90% of this extent as is the case in the example shown.

[0062] In the embodiment shown in [Fig.4], the teeth 35a are solid. It can be seen that these teeth 35a can have different shapes and / or dimensions, all the teeth 35a being able to be different.

[0063] Alternatively, the teeth 35a could comprise internal cavities, empty or filled for example with weights (not shown).

[0064] The section of [Fig.5] shows that the second body 38 can define an upstream part of the intrados 32a and the extrados 32b of the blade 32.

[0065] The section of [Fig.5] further shows a particular example of embodiment of the invention.

[0066] This section shows on the one hand a particular method of mounting the second body 38 on the first body 36. The second body 38 is slidably mounted on the first body 36. The sliding can be obtained by means of a rail and slide system 39, the first body 36 comprising a rail or the like and the second body 38 comprising a slide or the like, or vice versa. The slide is mounted in or on the rail and cooperates with it to guide the second body 38 relative to the first body 36, along the wedging axis A. It is therefore understood that the rail and slide system 39 preferably extends along the wedging axis A.

[0067] To enable the actuation of the rail and slide system 39 and therefore the movement of the second body 38 relative to the first body 36, the second body 38 advantageously comprises or is connected to at least one actuation finger 40 located on the side of the platform 32.

[0068] This actuating finger 40 has an elongated shape along a direction of movement of the second body 38 relative to the first body 36. This direction is preferably parallel to the axis A.

[0069] The platform 32 may comprise at least one orifice 42 crossed by the actuating finger 40.

[0070] It is therefore understood that the finger 40 for actuating the second body 38 is located outside the blade 32.

[0071] [Fig. 5] further shows a particular embodiment of the invention in which the leading edge 32c of the blade 32 is a double leading edge which comprises two leading edge walls 44a, 44b which are joined and located next to each other.

[0072] Each of these leading edge walls 44a, 44b comprises serrations 35 formed by an alternation of teeth 35a and hollows 35b along the leading edge.

[0073] Each of the leading edge walls 44a, 44b is also movable relative to the first body 36 independently of the other of the leading edge walls (FIGS. 6 to 8).

[0074] It can be seen in [Fig. 5] that the two leading edge walls 44a, 44b are connected respectively to two actuating fingers 40 which are parallel and located next to each other.

[0075] In the example shown, the platform 32 comprises two orifices 42 crossed respectively by the two actuating fingers 40.

[0076] In the context of the present invention, the term "assembly" refers to the combination of a stator blade 30 as described above with a stator casing 50.

[0077] The stator casing 50 is fixed and the blade 30 is mounted on the stator casing 50 so that its platform 32 is movable in rotation around the setting axis A with respect to the casing 50.

[0078] Advantageously, the casing 50 comprises at least one cam surface 52 which cooperates with a free end 40a of the or each actuating finger 40 so that a rotation of the platform 32 around the setting axis A causes a translation of the actuating finger 40 and a displacement of the corresponding second body 38 relative to the first body 36.

[0079] Figures 6 and 7 show an example of embodiment of the stator casing 50 in the aforementioned case of [Fig.5] where the blade 30 comprises two leading edge walls 44a, 44b.

[0080] The cam surface 52 is capable of cooperating with the two actuating fingers 40 so as to impose two different positions on the leading edge walls 44a, 44b with respect to the first body 36.

[0081] In the example shown, the cam surface 52 comprises two inclined parts 52a, 52b connected to each other by a non-inclined intermediate part 52c. When the ends 40a of the two fingers 40a are on the intermediate part 52c ([Fig. 6]), the walls 44a, 44b are in the same position along the axis A, in which the teeth 35a of the two walls are located next to each other and are for example contiguous (Figures 4 and 6).

[0082] When the end 40a of one of the fingers 40a is on one of the inclined parts 52a or 52b ([Fig.7]), the walls 44a, 44b are in different positions along the axis A, and the teeth 35a of the two walls 44a, 44b are no longer located next to each other. On the contrary, they are offset from each other along the axis A. In appearance, the leading edge 32c of the blade 32 then comprises more serrations, that is to say more teeth 35a (figures 7 and 8).

[0083] The clamps 35 are thus adaptable according to several operating points. This allows an acoustic reduction of the stator blades or a reduction in degradation on, for example, transient phases of the variable timing.

[0084] The second body 38 or each of the leading edge walls 44a, 44b can be moved relative to the first body 36 over a stroke which can represent between 1 mm and 100 mm approximately, and preferably between 1 and 50 mm approximately. This stroke corresponds to the maximum distance X between two extreme axial positions of a tooth 35a, measured along the axis A (Figures 6 to 8).

[0085] The second body 38 or the leading edge walls 44a, 44b of the second body 38 is / are preferably made of a metal alloy or a composite material.

[0086] To facilitate the sliding of the walls 44a, 44b between them, they can be covered with copper on their interface.

Claims

Claims

1. Variable-pitch stator vane (30) for an aircraft turbomachine, this vane (30) comprising: - a blade (32) comprising a lower surface (32a) and an upper surface (32b), as well as a leading edge (32c) and a trailing edge (32d), the leading edge (32c) of the blade (32) comprising serrations (35) formed by alternating teeth (35a) and hollows (35b) along the leading edge (32a), - a platform (34) connected to one end of the blade (32) and defining a vane pitch axis (A), characterized in that the blade (32) comprises: - a first body (36) made of metallic or composite material defining the trailing edge (32d) of the blade (32), and - a second body (38) defining at least a portion of the leading edge (32c) of the blade (32) and comprising at least part of the serrations (35), the second body (38) being mounted to move relative to the first body (36), along the setting axis (A).

2. A blade (30) according to claim 1, wherein the second body (38) defines the entire leading edge (32c) of the blade (32) and includes all of the serrations (35).

3. A blade (30) according to claim 1 or 2, wherein the second body (38) extends over the entire longitudinal extent of the blade (32) along the pitch axis (A).

4. Blade (30) according to one of claims 1 to 3, in which the second body (38) is slidably mounted on the first body (36).

5. Blade (30) according to one of claims 1 to 4, in which the second body (38) defines an upstream portion of the intrados (32c) and the extrados (32d) of the blade (32).

6. Blade (30) according to one of claims 1 to 5, in which the second body (38) comprises at least one actuating finger (40) on the side of said platform (34).

7. A blade (30) according to claim 1 to 6, wherein said at least one actuating finger (40) has an elongated shape along a direction of movement of the second body (38) relative to the first body (36).

8. Blade (30) according to claim 1 to 7, in which the platform (34) comprises at least one orifice (42) crossed by said at least one actuating finger (40).

9. A blade (30) according to one of claims 1 to 8, wherein the leading edge (32c) of the blade (32) is a double leading edge which comprises two adjoining leading edge walls (44a, 44b) located next to each other, each of these leading edge walls (44a, 44b) comprising serrations (35) formed by alternating teeth (35a) and hollows (35b) along the leading edge, each of the leading edge walls (44a, 44b) being movable relative to the first body (36) independently of the other of the leading edge walls (44a, 44b).

10. A blade (30) according to claim 9, wherein the two leading edge walls (44a, 44b) are respectively connected to two actuating fingers (40) which are parallel and located next to each other.

11. Blade (30) according to claim 10, in which the platform (34) comprises two orifices (42) crossed respectively by the two actuating fingers (40).

12. Assembly comprising a blade (30) according to one of claims 1 to 11 and a stator casing (50), the stator casing (50) being fixed and the blade (30) being mounted on the stator casing (50) so that its platform (34) is movable in rotation around the setting axis (A) with respect to the casing (50).

13. An assembly according to claim 12, the blade (30) being as defined in one of claims 6, 7, 8, 10 or 11, in which the casing (50) comprises at least one cam surface (52) which cooperates with a free end (40a) of the or each actuating finger (40) so that a rotation of the platform (34) around the setting axis (A) causes a translation of the actuating finger (40) and a displacement of the second body (38) relative to the first body (36).

14. An assembly according to claim 13, the blade (30) being as defined in claim 10 or 11, wherein said at least one cam surface (52) is capable of cooperating with the two actuating fingers (40) so as to impose two different positions on the leading edge walls (44a, 44b) with respect to the first body (36).

15. Turbomachine for an aircraft, comprising blades (30) according to one of claims 1 to 11.

Images