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), - a platform (34) connected to one end of the blade (32) and defining a blade setting axis (A), the blade (32) comprises: - a first body (36) defining the trailing edge (32d) of the blade (32), and - a second body (38) made of elastically deformable material which defines at least a portion of the leading edge (32c) of the blade (32) and which is fixed to the first body (36) and connected to a system actuating device which is located entirely outside the blade (32). 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 comprising serrations formed by alternating teeth and hollows,

[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 made of elastically deformable material defining at least one part of the leading edge of the blade and comprising at least part of the serrations, the second body being fixed to the first body and connected to an actuation system which is located entirely outside the blade.

[0029] The invention thus proposes to produce the rotor blade blade from two distinct materials. 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 is made of elastically deformable material such as elastomer. This second body defines at least a portion of the leading edge and comprises all or part of the serrations. It is therefore understood that these serrations are made of elastic material and are capable of deforming elastically.

[0030] The elastic deformation of the second body and therefore of the leading edge is caused by the actuation system which is offset from the blade. This actuation system therefore has no impact or little impact on the design and manufacture of the blade.

[0031] The invention makes it possible, for example, to integrate variability in the geometry and radial position of the clamping teeth as a function of the engine speed as well as the aerodynamic pressure forces exerted by the air flow in operation. Since a sator blade has a tendency to untwist in the centrifuge, it is advantageous to have a deformable material so as not to interfere with the internal forces in the blade and its own operation.

[0032] The second body is fixed to the first body, for example by gluing, as is the case with a shield of the prior art.

[0033] 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 defines an upstream part of the intrados and the extrados of the blade; - the second body is connected to at least one actuating finger on the side of said platform; - this actuating finger passes through at least one orifice of the platform; - said at least one actuating finger has an elongated shape along the wedging axis; - the orifice of the platform has a curved shape and extends in the circumferential direction around the wedging axis, over a predetermined angle, the actuating finger being able to move in the circumferential direction in this orifice; - the actuating finger is capable of coming to bear on at least one of the circumferential ends of the orifice and of transmitting to the second body a force which is a function of a force generated by the pressure of the actuating finger on this end; - at least some of the teeth are hollow and include, for example, internal cavities; the cavities make it possible to modify the dynamic behavior of the teeth in operation; - at least some of the teeth are full.

[0034] 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.

[0035] 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:

[0036] - the casing comprises a housing for receiving a free end of the finger actuation;

[0037] - the free end of the actuating finger is mounted without play in the housing of so as to be fixed relative to the casing during rotation of the platform around the wedging axis;

[0038] - which housing has a curved shape and extends in the circumferential direction around the wedging axis, at a predetermined angle, the actuating finger being able to move in the circumferential direction in this housing;

[0039] - the actuating finger is capable of coming to bear on at least one of the ends circumferential of the housing and to transmit a force to the second body which is a function of a force generated by the pressure of the actuating finger on this end.

[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 schematic view of a variable-pitch stator or rectifier blade, according to an alternative embodiment of the invention, and further shows a stator casing associated with this blade;

[0047] [Fig.6] [Fig.6] is a sectional view along line VLVI of [Fig.5];

[0048] [Fig.7a-7b] Figures 7a and 7b are views similar to that of [Fig.6] and show two positions of blade setting and deformation of its leading edge; and

[0049] [Fig.8a-8b] Figures 8a and 8b are views similar to those of Figures 6a and 6b and show a variant of the two positions of blade setting and deformation of its leading edge. 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.

[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 made of elastically deformable material defining at least a portion of the leading edge 32c of the blade 32 and comprising at least a portion of the serrations 35, the second body 38 being fixed to the first body 36.

[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 in [Fig.4], 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.

[0062] In the example shown in [Fig.5], the second body 38 defines only a portion of the leading edge 32c of the blade 32 and comprises a portion of the serrations 35.

[0063] The second body 38 may extend over approximately 50 to 80% of the longitudinal extent of the blade 32 along the pitch axis A.

[0064] The second body 38 is preferably made of elastomer.

[0065] The second body 38 can define a downstream portion of the intrados 32a and the extrados 32b of the blade 32.

[0066] The fixing of the second body 38 on the first body 36 can be carried out by gluing on the body 36.

[0067] In the embodiment shown in Figures 4 and 5, 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.

[0068] Alternatively, the teeth 35a or at least some of the teeth could be hollow and include internal cavities that are empty or filled, for example with weights (not shown).

[0069] The second body 38 can define an upstream portion of the intrados 32c and the extrados 32d of the blade 32.

[0070] To allow the elastic deformation of the second body 38, the second body 38 is advantageously connected to an actuation system which preferably comprises at least one actuation finger 40 located on the side of the platform 34.

[0071] The actuation system and therefore the actuation finger 40 is entirely located outside the blade 32.

[0072] 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.

[0073] The platform 34 may comprise at least one orifice 42 crossed by the actuating finger 40.

[0074] 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.

[0075] The stator casing 50 is fixed and the blade 30 is 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.

[0076] Advantageously, a rotation of the platform 34 around the wedging axis A causes, over all or part of its travel, a torque force on the second body 38 which will then deform elastically.

[0077] Figures 5 and 6 show an exemplary embodiment of the platform 34 and the stator casing 50.

[0078] The orifice 42 of the platform 34 has a curved shape and extends in the circumferential direction around the wedging axis A, over a predetermined angle α.

[0079] The actuating finger 40 is able to move in the circumferential direction in the orifice 42. The actuating finger 40 is able to come to bear on at least one of the circumferential ends of the orifice 42 and to transmit a force to the rest of the second body 38 which is a function of a force generated by the pressure of the actuating finger 40 on this end.

[0080] The free end of the finger 40 is here engaged in a housing 52 of the casing 50.

[0081] This housing 52 may have a shape complementary to that of the free end of the finger 50 so that the second body 38 is deformed upon a first rotation of the blade 30 around its setting axis A.

[0082] Alternatively, the orifice 52 could have a curved shape like the orifice 42, and extend circumferentially around the setting axis A, over a predetermined angle.

[0083] The orifice 42 and the housing 52 may have different angular extents or not depending on the deformations desired for the second body 38. In the case where the orifice 42 and the housing 52 have the same angular extent, they are preferably angularly offset from each other around the A axis. In case they have different angular extents, they can be superimposed and centered relative to each other, or they can also be offset.

[0084] The position of the end of the finger 40 in the orifice 42 and the housing 52, when the turbomachine is stopped or at rest, can be chosen according to the deformations envisaged for the different engine speeds.

[0085] Figures 7a and 7b, on the one hand, and 8a and 8b, on the other hand, illustrate two cases in this regard.

[0086] These figures show the behavior of the second body 38 and of the serrations 35 as a function of the speed of the turbomachine equipped with the rotor blades according to the invention.

[0087] In Figure 7a, the turbomachine is in cruising mode and the finger 40 of the blade 32 is centered in the orifice 42 of the platform. It can be seen that the finger 40 does not transmit any force to the second body which is not deformed.

[0088] In Figure 7b, the turbomachine takes off. The blade 30 is wedged and the finger 40 bears on a circumferential end of the orifice 42. The finger 40 then transmits a force to the second body 38 which deforms elastically and causes a deformation of at least some of its teeth 35a. The teeth 35a located near the platform 34 can be deformed more than the teeth 35a located opposite the platform 34.

[0089] Alternatively, in Figure 8a, the turbomachine is in cruising mode and the finger 40 of the blade 32 is already located at a circumferential end of the orifice 42 of the platform. It can be seen that the finger 40 does not transmit any force to the second body 38 which is not deformed.

[0090] In Figure 8b, the turbomachine is in thrust reversal mode. The blade 30 is wedged and the finger 40 bears on the circumferential end of the orifice 42. The finger 40 transmits a force to the second body 38 which deforms elastically and causes deformation of at least some of its teeth 35a. The teeth 35a located near the platform 34 may be deformed more than the teeth 35a located opposite the platform 34.

[0091] The teeth 35a can thus adopt different positions depending on the engine speeds. These positions are advantageously designed to attenuate the noise generated during operation. It is therefore understood that, whatever the engine speed, the serrations 35 can attenuate the noise generated during operation, including in thrust reversal mode.

[0092] The clampings 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 variable timing.

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 an alternation of teeth (35a) and hollows (35b), - a platform (34) connected to one end of the blade (32) and defining a blade setting 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) made of elastically deformable material defining at least a portion of the leading edge (32c) of the blade (32) and comprising at least a portion of the serrations (35), the second body (38) being fixed to the first body (36) and connected to an actuation system which is located entirely outside the blade (32).

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) defines an upstream portion of the intrados (32c) and the extrados (32d) of the blade (32).

5. Blade (30) according to one of claims 1 to 4, in which the second body (38) is connected to at least one actuating finger (40) on the side of said platform (34), this actuating finger (40) passing through at least one orifice (42) of the platform (34).

6. A blade (30) according to claim 5, wherein said at least one actuating finger (40) has an elongated shape along the setting axis (A).

7. A blade (30) according to claim 5 or 6, wherein the orifice (42) of the platform (34) has a curved shape and extends in the circumferential direction around the setting axis (A), at an angle (a) predetermined, the actuating finger (40) being able to move in the circumferential direction in this orifice (42).

8. Blade (30) according to claim 7, in which the actuating finger (40) is capable of coming to bear on at least one of the circumferential ends of the orifice (42) and of transmitting to the second body (38) a force which is a function of a force generated by the pressure of the actuating finger (40) on this end.

9. A blade (30) according to one of claims 1 to 8, wherein at least some of the teeth (35a) are hollow.

10. A blade (30) according to one of claims 1 to 8, wherein at least some of the teeth (35a) are solid.

11. Assembly comprising a blade (30) according to one of claims 1 to 10 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).

12. Assembly according to claim 11, the blade (30) being as defined in one of claims 7 to 9, in which the casing (50) comprises a housing (52) for receiving a free end of the actuating finger (40).

13. Assembly according to claim 12, in which the free end of the actuating finger (40) is mounted without play in the housing (52) so as to be fixed relative to the casing (50) during a rotation of the platform (34) around the wedging axis (A).

14. An assembly according to claim 13, wherein the housing (52) has a curved shape and extends in the circumferential direction around the wedging axis (A), over a predetermined angle, the actuating finger (40) being able to move in the circumferential direction in this housing (52).

15. Assembly according to claim 14, in which the actuating finger (40) is capable of coming to bear on at least one of the circumferential ends of the housing (52) and of transmitting a force to the second body (38) which is a function of a force generated by the pressure of the actuating finger (40) on this end.

16. Turbomachine for an aircraft, comprising blades (30) according to one of claims 1 to 10.

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