Variable timing stator vane for an aircraft turbomachine

Abstract

A variable-pitch stator blade (30) for an aircraft turbomachine, comprising: - a blade (32) having an upper 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) having serrations (35) formed by alternating teeth (35a) and grooves (35b) along the leading edge (32a), - a platform (34) connected to one end of the blade (32) and defining a blade pitch 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 movably mounted relative to the first body (36), along the alignment axis (A). Figure for the abbreviation: Figure 4

Description

Title of the invention: Variable timing stator blade 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 Downstream 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 that drives at least one propeller. The gas generator includes at least one compressor, one combustion chamber, and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the propeller rotor for its rotational drive.

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

[0005] A propeller may be unfaired. This is the case of a turboprop engine, 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 elongation axes.

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

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

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

[0010] The evolution of turbomachine performance tends towards an increase in their bypass ratio, which is mainly achieved by increasing the diameter of the propellers and therefore 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 reduces noise emissions outside the turbomachine.

[0013] In the case of an unfaired propeller, other solutions must be found for reducing propulsion noise. This is particularly the case for the turbomachine illustrated in [Fig. 1]. This turbomachine 10 comprises an upstream propeller 12, which includes rotor blades 14 with variable pitch, and a downstream stator 16, which includes stator blades 18 also with variable pitch.

[0014] To remedy the noise emission problem, a noise reduction technology already known on fans and inspired in particular by the wings of nocturnal birds of prey consists of providing 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 an alternation of teeth 20a and hollows 20b along this edge. The serrations can cause variations in the blade chord as a function of the radial height, with varying thicknesses and a very thin leading or trailing edge.

[0016] The teeth 20a are defined so as to reduce noise in the mid-emission spectrum without significantly 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 observed that, in most engine operating conditions, serrations help to reduce noise. However, a significant increase in noise has also been observed when the blades are set in reverse or thrust reversal mode. In the case of a rotor blade, the trailing edge serrations are oriented upstream in reverse mode, which greatly disrupts the aerodynamic flow. The serrations then become 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 that the serrations cannot be made of 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 serrations tearing off as well as the complexity of making these serrations which leads to significant scrap due to geometric defects.

[0022] The present invention proposes 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 an intrados and an extrados, as well as a leading edge and a trailing edge, the leading edge of the blade featuring serrations formed by an alternation of teeth and grooves along the leading edge,

[0025] - a platform connected to one end of the blade and defining a pitching axis 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 part of the leading edge of the blade and comprising at least part of the serrations, the second body being mounted movable vis-à-vis the first body, along the alignment axis.

[0029] The invention thus proposes dividing the stator blade into two parts, called bodies. The first body of the blade is made of metallic or composite material and includes the trailing edge of the blade. The second body of the blade can be made of a different material than the first body. This second body defines at least part of the leading edge and includes all or part of the serrations. The mobility of the second body relative to the first body allows the position of the serrations on the blade to be varied, in particular along the pitch axis.

[0030] The invention allows, for example, the integration of a 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 airflow in operation.

[0031] The blade according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - 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 mounted to slide on the first body; - the second body defines an upstream part of the intrados and extrados of the pale ; - the second body includes at least one actuation finger on the side of said platform; - said at least one actuation finger has an elongated shape along a direction of movement of the second body relative to the first body; - the platform includes at least one opening through which said at least one actuating finger passes; - the leading edge of the blade is a double leading edge which comprises two contiguous leading edge walls situated next to each other, each of these leading edge walls having 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 way, regardless of the engine speed; - the two leading edge walls are connected respectively to two actuation fingers which are parallel and located next to each other; - the platform includes two openings through which the two actuation fingers pass respectively;

[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 actuating finger or fingers are located outside the blade.

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

[0037] The assembly according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0038] - the housing includes at least one cam surface which cooperates with an end free of the actuating finger or fingers so that a rotation of the platform around the shimming 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 as described above. Brief description of the figures

[0041] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0042] [Fig-1] [Fig.1] is a schematic perspective view of a turbomachine unfaired propeller and unfaired straightener, the propeller and straightener 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 stator or rectifier blade with variable pitch;

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

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

[0047] [Fig. 6] [Fig. 6] is a partial schematic perspective view of the stator blade of the [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 above.

[0051] The invention relates to a variable-pitch stator blade for an aircraft turbomachine, which may be the turbomachine of [Fig.1] or another turbomachine.

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

[0053] - a blade 32 comprising an intrados 32a and an extrados 32b, as well as an edge a leading edge 32c and a trailing edge 32d, and

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

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

[0056] The distinctive feature of the blade 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 part of the leading edge 32c of the blade 32 and comprising at least part of the serrations 35, the second body 38 being mounted movable vis-à-vis the first body 36, along the alignment axis A.

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

[0060] In the example shown, the second body 38 defines the entire leading edge 32c of the blade 32 and includes all 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 include internal cavities, empty or filled for example with weights (not shown).

[0064] The cross-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 cross-section of [Fig.5] further shows a particular example of an embodiment of the invention.

[0066] This section shows, on the one hand, a particular mounting method for the second body 38 on the first body 36. The second body 38 is mounted to slide on the first body 36. The sliding motion can be achieved by means of a rail and slide system 39, the first body 36 comprising a rail or similar device and the second body 38 comprising a slide or similar device, 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 alignment axis A. It is therefore understood that the rail and slide system 39 preferably extends along the alignment axis A.

[0067] To enable the actuation of the rail and slide system 39 and thus 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 actuating 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 vis-à-vis the first body 36. This direction is preferably parallel to the axis A.

[0069] The platform 32 may include at least one orifice 42 through which the actuating finger 40 passes.

[0070] It is therefore understood that the actuation finger 40 of 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 comprising two contiguous leading edge walls 44a, 44b situated next to each other.

[0072] Each of these leading edge walls 44a, 44b has 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 mobile with respect to the first body 36 independently of the other leading edge walls (figures 6 to 8).

[0074] We can see on [Fig.5] that the two leading edge walls 44a, 44b are connected respectively to two actuation fingers 40 which are parallel and located next to each other.

[0075] In the example shown, the platform 32 includes two orifices 42 through which the two actuating fingers 40 pass respectively.

[0076] In the context of the present invention, the combination of a stator blade 30 as described above with a stator housing 50 is called an “assembly”.

[0077] The stator housing 50 is fixed and the blade 30 is mounted on the stator housing 50 so that its platform 32 is mobile in rotation around the alignment axis A vis-à-vis the housing 50.

[0078] Advantageously, the housing 50 includes 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 timing axis A causes a translation of the actuating finger 40 and a displacement of the corresponding second body 38 with respect to the first body 36.

[0079] Figures 6 and 7 show an example of an embodiment of the stator housing 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 able to cooperate 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 by an intermediate, non-inclined 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, touching (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 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 axis A. Apparently, the leading edge 32c of the blade 32 then has more serrations, i.e. more teeth 35a (figures 7 and 8).

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

[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 ranging from approximately 1 mm to 100 mm, and preferably from approximately 1 mm to 50 mm. This stroke corresponds to the maximum distance X between two extreme axial positions of a tooth 35a, measured along 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 metallic alloy or composite material.

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

Claims

Demands

1. A variable-pitch stator blade (30) for an aircraft turbomachine, said blade (30) comprising: - a blade (32) having an intrados (32a) and an extrados (32b), as well as a leading edge (32c) and a trailing edge (32d), the leading edge (32c) of the blade (32) having serrations (35) formed by an alternation of teeth (35a) and grooves (35b) along the leading edge (32a), - a platform (34) connected to one end of the blade (32) and defining a blade pitch axis (A), characterized in that the blade (32) comprises: - a first body (36) 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 movable vis-à-vis the first body (36), along the alignment axis (A).

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

3. 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 any one of claims 1 to 3, wherein the second body (38) is mounted sliding on the first body (36).

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

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

7. 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, wherein the platform (34) comprises at least one orifice (42) through which said at least one actuating finger (40) passes.

9. Blade (30) according to any one of claims 1 to 8, wherein the leading edge (32c) of the blade (32) is a double leading edge comprising two contiguous leading edge walls (44a, 44b) situated next to each other, each of these leading edge walls (44a, 44b) having serrations (35) formed by an alternation of 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. Blade (30) according to claim 9, wherein the two leading edge walls (44a, 44b) are connected respectively to two actuating fingers (40) which are parallel and located next to each other.

11. Blade (30) according to claim 10, wherein the platform (34) comprises two orifices (42) through which the two actuating fingers (40) pass respectively.

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

13. Assembly according to claim 12, the blade (30) being as defined in any one of claims 6, 7, 8, 10 or 11, wherein the housing (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) about the staking 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. 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 able to cooperate 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 any one of claims 1 to 11.

Images