Fan blade including a rigid fiber insert

Abstract

The invention relates to a fan blade (3), which has a structure made of composite material, the structure comprising a fiber reinforcement (5) and a matrix, the fiber reinforcement being obtained by three-dimensional weaving of warp and weft threads, the fiber reinforcement (5) being embedded in the matrix, wherein the fiber reinforcement (5) comprises a first part (14) forming a trailing edge (9) of the structure made of composite material and a second part (15) forming a leading edge (8) of the structure, and wherein the warp threads of the fiber reinforcement (5) comprise a first thread (12) and a second thread (13), the first thread having a predetermined stiffness, the stiffness of the second thread being greater than the stiffness of the first thread (12), the first part (14) comprising all or part of the first threads (12) and not comprising the second threads (13), and the second part (15) comprising all or part of the second threads (13).

Description

Technical Field

[0001] The present invention relates generally to the field of turbomachines and more particularly to the field of fan blades for such turbomachines and methods of making the same.

[0002] More specifically, the present invention applies to fan blades made of composite materials and the interaction of the fan blades with the inlet of a primary flow channel. Background Art

[0003] Turbine blades, especially fan blades, are subject to extreme mechanical and thermal stresses and must meet stringent weight and volume conditions. Therefore, it is advisable to use composite blades comprising a fiber reinforcement densified by a polymer matrix, which are lighter and have satisfactory thermal resistance compared to metal blades with equivalent propulsion characteristics.

[0004] As is known, such a composite blade comprises a structure made of composite material, comprising a fiber reinforcement obtained by three-dimensional weaving and a matrix in which the fiber reinforcement is embedded, and also forms the leading edge, the trailing edge, the inner buttress and the outer buttress.

[0005] Metal shielding is often added to the leading edge of the blade to improve the blade's resistance to inhalation under fast dynamic conditions. However, statically, this shielding introduces stiffness and added mass that increases the centrifugal forces near the leading edge.

[0006] Statically, each fan blade is subjected to the effects of centrifugal loads and aerodynamic pressure. The blade then deforms significantly and unevenly. In particular, it appears that the leading edge of the blade moves more than the trailing edge of the blade.

[0007] In the case of a fan comprising blades made of composite material, the pitch angle is an important parameter affecting the aerodynamic performance of the fan blades. The pitch angle is defined as the angle formed between the chord of the fan blade (i.e., the section connecting the leading edge and the trailing edge of the blade in the tangent plane) and the axis of rotation of the fan in a plane tangent to the platform of the fan blade. The larger the pitch angle, the more "closed" the fan blades are. The smaller the pitch angle, the more "open" the fan blades are.

[0008] The pitch angle is an aerodynamic parameter optimized for the operating point at the top of the cruising speed or climbing speed in order to achieve the required flow. The pitch angles at other operating points are obtained by finite element calculations. The pitch angle can be plotted as a function of the blade height, that is, the pitch angle varies between the root and the tip of the blade (due to the twisted shape of the blade).

[0009] It is also possible to plot the pitch difference corresponding to the pitch angle difference value between two given speeds. High pitch angle difference values ​​are directly due to high blade static displacement values, in particular to the untwisting of the blades (caused by a greater displacement of the leading edge than of the trailing edge depending on the engine speed).

[0010] When designing fan blades, one of the goals of aerodynamic iteration is to reduce the untwisting of the blades. To this end, it is known to modify the laws of the blades, in particular the stacking laws, according to the height and chord of the blades. However, these modifications can be particularly detrimental to aerodynamic performance.

[0011] Furthermore, to improve the aerodynamics of the blades, the pitch angle is preferably "open" at the top of the climb phase (to ensure flow) and "closed" during part of the climb phase and / or to achieve surge / flutter margin.

[0012] However, in most fan blades made of composite materials, the difference in tangential displacement between the leading and trailing edges of the blade is greater during the climb phase than at the top of the climb phase. The results show that the pitch of the fan blade is more open during the climb phase than at the top of the climb phase, and therefore the pitch angle of the blade is greater at the top of the climb phase than during the climb phase. Therefore, the untwisting of the blade is detrimental to its aerodynamic performance. Summary of the invention

[0013] Therefore, one of the objects of the present invention is to overcome the above-mentioned drawbacks by proposing a fan blade for a turbine engine, the displacement of which is consistent with the required aerodynamic performance between the different operating phases of the engine, in particular during the climb phase and the top of the climb / cruise phase.

[0014] To this end, according to a first aspect of the invention, a fan blade for a turbomachine is proposed, the fan blade comprising a composite material structure comprising a fiber reinforcement and a matrix, the fiber reinforcement being obtained by three-dimensional weaving of warp and weft threads, the fiber reinforcement being embedded in the matrix,

[0015] - Composite structure including leading and trailing edges,

[0016] - the fiber reinforcement comprises a first portion forming the trailing edge and a second portion forming the leading edge,

[0017] The warp threads of the fiber reinforcement comprise first threads having a predetermined stiffness.

[0018] The warp threads of the fiber reinforcement further include second threads having a stiffness greater than that of the first threads, the first portion includes all or part of the first threads and has no second threads, and the second portion includes all or part of the second threads.

[0019] Some preferred but non-limiting characteristics of the blade according to the first aspect are the following taken alone or in combination:

[0020] - the second portion of warp threads further comprises the first thread;

[0021] - the blade further comprises an airfoil blade adapted to extend in the airflow, the airfoil blade having a tip and a root, the root being configured to be fixed to a disk of the fan, wherein the second portion extends from the root to the tip over the entire height of the blade;

[0022] - the blade further comprises an airfoil blade adapted to extend in the airflow, the airfoil blade having a tip and a root, the root being configured to be fixed to a disk of the fan, wherein the second portion extends over a chord portion of the composite structure, the chord portion being variable between the root and the tip of the blade;

[0023] - at the root of the blade, the second portion extends over a length between 25% and 40% of the chord length of the composite structure;

[0024] - the blade further comprises a metal shield added and fixed to the leading edge, the second portion exceeding the metal shield at the root but being covered by the metal shield at the tip;

[0025] - a second portion extends beyond the metal shield at the root until 40% to 50% of the height of the blade, and then the second portion is covered by the metal shield until the tip;

[0026] - at half the height of the blade, the second portion extends over a length between 10% and 30% of the chord length of the composite structure;

[0027] - at the tip of the blade, the second portion extends over a length between 0% and 5% of the chord length of the composite structure;

[0028] - the fiber reinforcement further comprises a third portion extending between the second portion and the first portion, the density of the second threads gradually decreasing from the second portion to the first portion in the third portion;

[0029] - the third portion extends over a length between 5% and 10% of the chord length of the composite structure;

[0030] - the blade further comprises a metal shield added and fixed to the leading edge, said metal shield covering the second portion and leaving the first portion exposed;

[0031] - the Young's modulus of the second thread is between 1.2 and 1.5 times the Young's modulus of the first thread;

[0032] - The first thread and the second thread comprise carbon fibers.

[0033] According to a second aspect, the invention proposes a fan for a turbomachine and a turbomachine comprising such a fan, the fan comprising a plurality of blades according to the first aspect.

[0034] According to a third aspect, the invention proposes an aircraft comprising such a turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will appear from the following description, which is merely illustrative and not restrictive and should be read with reference to the accompanying drawings, in which:

[0036] Figure 1 An exemplary embodiment of a fiber reinforcement for a fan blade made of composite material according to the invention is schematically shown.

[0037] Figure 2 After the matrix is ​​injected and the metal shield is fixed, it includes Figure 1 Side view of a blade with fiber reinforcement.

[0038] Figure 3 It is shown that at the root of the blade, Figure 1 An example of a fiber reinforcement arranged along the warp of a plane perpendicular to the stacking axis Z.

[0039] Figure 4 is a perspective view of an exemplary embodiment of a fan including blades according to the present invention.

[0040] Figure 5 Schematically shows Figure 1 The braiding of the reinforcement.

[0041] Similar elements have the same reference numerals throughout the drawings. DETAILED DESCRIPTION

[0042] In the present application, upstream and downstream are defined relative to the normal flow direction of the gases in the fan 1 through the turbine. Furthermore, the "axis of rotation of the fan 1" refers to the radial symmetry axis X of the fan 1. The axial direction corresponds to the direction of the axis X of the fan 1, the radial direction being the direction perpendicular to and passing through this axis. Finally, "inner" and "outer" will be used with reference to the radial direction, respectively, so that an inner part or face of an element is closer to the axis X than an outer part or face of the same element.

[0043] The turbomachine fan 1 comprises a fan disk 2 carrying a plurality of fan blades 3 associated with inter-blade platforms.

[0044] Each blade 3 comprises a composite material structure comprising a fiber reinforcement and a matrix, the fiber reinforcement being obtained by three-dimensional weaving, the fiber reinforcement being embedded in the matrix. By "three-dimensional weaving" is meant that the warp threads follow a zigzag path to tie the weft threads together, it being noted that a three-dimensional weaving, in particular an interlocking weaving, may comprise a two-dimensional weaving on the surface. Different three-dimensional weavings may be used, such as interlocking, multi-satin or multi-canvas weavings, for example, in particular as described in document WO 2006 / 136755.

[0045] The composite structure comprises a root 6 and an airfoil blade 7 having a leading edge 8, a trailing edge 9 and a tip 10. The leading edge 8 is configured to extend facing the gas flow entering the turbine. The leading edge 8 corresponds to the front part of the airfoil, which faces the airflow and divides it into an internal flow and an external flow. The trailing edge 9, for its part, corresponds to the rear part of the airfoil, where the internal flow and the external flow meet.

[0046] Finally, the structure is formed by a plurality of blade segments stacked from the root 6 along a stacking axis Z extending radially with respect to the axis of rotation X of the fan 1 .

[0047] The root 6 of each blade 3 engages in an axial groove formed in the fan disk 2. The airfoil blade 7 is suitable for being placed in the airflow when the engine is running, so as to divide the airflow into an inner flow and an outer flow, thereby generating lift. The height h of the blade 3 corresponds to the size of the blade section at the lower radial end of the root 6 and the tip 10 along the stacking axis Z. For example, the height h can be measured at the intersection between the leading edge 8 and the lower limit of the blade 7 (corresponding to the junction between the leading edge 8 and the platform 11). In the fiber reinforcement 5 shown Figure 1 In FIG. 1 , the platform position 11 is indicated by a dotted line.

[0048] In one embodiment, the blade 3 further comprises a metal shield 4 added and fixed to the leading edge 8 to protect the blade 3, in particular from damage by ingested objects, such as birds.

[0049] The fiber reinforcement 5 may be formed by a one-piece fiber preform obtained by three-dimensional weaving. The fiber reinforcement 5 comprises fibers, which may be made of carbon, glass, basalt or aramid in particular. For its part, the matrix is ​​usually a polymer matrix, such as epoxy resin, bismaleimide or polyamide. The blade 3 is then molded by a vacuum resin injection process of the resin transfer molding (RTM) or vacuum resin transfer molding (VARTM) type.

[0050] The fiber reinforcement 5 is formed by three-dimensional weaving of warp and weft. The warp includes a first wire 12 having a predetermined stiffness and a second wire 13 having a predetermined stiffness greater than that of the first wire 12. In one embodiment, the weft includes only the first wire 12.

[0051] Therefore, the fiber reinforcement 5 is obtained by intermixing the warp threads constituting the fiber reinforcement 5 so as to best exploit the mechanical properties of each warp thread according to the area of ​​the blade 3 and the type of load.

[0052] Herein, “stiffness” means Young's modulus (E). In one embodiment, the stiffness of the second wire 13 is between 1.2 and 1.5 times the stiffness of the first wire 12 .

[0053] The first wire 12 and the second wire 13 have a high Young's modulus, for example greater than or equal to 250 GPa, and have the function of being able to meet the design criteria of the blade 3, in particular the frequency state of the blade 3. Therefore, this allows limiting the frequency crossover between the first energy eigenmode of the blade 3 and the engine harmonics, or at least moving the frequency crossover between the first energy eigenmode of the blade 3 and the engine harmonics. In addition, adding a wire with greater stiffness (the second wire 13) in the reinforcement 5 makes it possible to increase the frequency of the first eigenmode of the blade 3.

[0054] Thus, the first threads 12 are used to weave all or part of the fiber preform to form the reinforcement 5, including that portion (or first portion 14) of the reinforcement 5 comprising the trailing edge 9. The first portion 14 of the reinforcement 5 is free of the second threads 13.

[0055] The second wire 13 has a stiffness greater than that of the first wire 12, and the second wire 13 has the function of statically reducing the untwisting of the blade 7. Therefore, these second wires 13 are used to weave the fiber preform to form the portion (or the second portion 15) of the reinforcement 5 that forms the leading edge 8. Therefore, the second wire 13 that forms the leading edge 8 can harden the area of ​​the leading edge 8 and reduce the tangential displacement of the leading edge 8. Therefore, the tangential displacement difference between the leading edge 8 and the trailing edge 9 is more balanced or even zero. Therefore, during changes in engine speed, the pitch of the blade 3 changes little.

[0056] The Applicant has noted the fact that, although the stiffness of the blade 3 is increased in the region of the leading edge 8 , this has no adverse effect on the performance of the blade 3 in the event of an ingestion of an object, since the deformation is mainly absorbed by the metal shield 4 .

[0057] The second part 15 comprises the first thread 12 and the second thread 13. However, the second part 15 comprises more second threads 13 than the first threads 12, in order to sufficiently increase the stiffness of the blade 7 in the region of the leading edge 8. Typically, the second part 15 comprises between 70% and 90% of the second thread 13. In one embodiment, only the first thread 12 and the second thread 13 are used in the weaving of the second part 15. The complementary part (i.e., respectively between 30% and 10%) consists of the first thread 12.

[0058] In one embodiment, in order to ensure optimal use of the stiffness of the second wire 13 in the region of the leading edge 8, the second wire 13 can be arranged as a skin, that is to say placed at the inner and outer faces of the blade 3. Thus, the rigid skin makes it possible to limit the torsional and bending deformations of the blade 3 and thus reduce the pitch angle difference.

[0059] The second portion 15 extends from the root 6 to the tip 10 over the entire height h of the blade 3 in order to increase the rigidity of the reinforcement 5 in the region of the leading edge 8 over the entire height h of the blade 3 .

[0060] The second portion 15 extends axially substantially over a portion of the chord L of the composite structure that is variable between the root 6 and the tip 10 of the blade 3, in order to adapt the stiffness of the region of the leading edge 8 according to the loads on the blade 3, which are directly related to the engine speed (in particular the pitch angle) and the fan diameter (which determines the size of the birds that can be inhaled and therefore the resistance requirements of the blade 3 against inhalation). In this context, the chord L means the straight line segment parallel to the tangent plane relative to the axis X and connecting the leading edge 8 and the trailing edge 9.

[0061] Therefore, if Figure 2 As shown, the length of the second portion 15 can extend sufficiently to exceed the end of the metal shield 4 by a first percentage of the height h of the blade 3 (up to half the height h / 2), because at these heights, the suction load is low. Starting from 40% to 50% of the height h up to the tip 10, the length of the second portion 15 can gradually decrease to meet the resistance requirements against suction, so that in the upper half of the second portion 15 (i.e., the portion located radially outside relative to the axis X), the second portion 15 is covered by the shield 4.

[0062] For example, in the root 6 of the blade 3, the second portion 15 extends over a length L1 between 25% and 40% of the chord length L, for example, at the root 6 of the blade, the second portion 15 extends over a length L1 approximately equal to one third of the chord length L. At half the height h / 2 of the blade 3, the second portion 15 extends over a length L2 between 10% and 30% of the chord length, for example, at half the height L of the blade 3, the second portion 15 extends over a length L2 approximately equal to one quarter of the chord length. On the other hand, at the tip 10, the second portion 15 is very narrow or even has a zero length L3, since this region is usually subject to significant suction loads.

[0063] The reinforcement body 5 further includes a third portion 16 extending between the second portion 15 and the first portion 14, and in the third portion 16, the density of the second wire 13 gradually decreases from the second portion 15 toward the first portion 14 until the density of the second wire 13 is zero. In one embodiment, when weaving the third portion 16, only the first wire 12 and the second wire 13 are used as warp threads.

[0064] The third portion 16 is configured to serve as a boundary between the first portion 14 and the second portion 15 in order to limit the weakening due to material discontinuity. When the first portion 14 and the second portion 15 meet end to end in the reinforcement 5, the blade 3 thus obtained has a pitch angle difference value that is effectively reduced or even zero, regardless of the engine speed. However, the applicant has noted the fact that in the absence of the third portion 16 (that is, by abruptly increasing the first line 12 and removing the second line 13 located at the boundary between the first portion 14 and the second portion 15 of the fiber reinforcement 5), the blade 3 obtained may be severely damaged at this boundary in the event of a collision, because the boundary between the two portions 14, 15 of the reinforcement 5 is weakened due to the discontinuity of the material properties.

[0065] The third portion 16 thus enables a transition between the material properties of the first portion 14 and the material properties of the second portion 15. To this end, the density of the first threads 12 gradually increases within the third intermediate portion 16 from the second portion 15 to the first portion 14.

[0066] For example, near the second portion 15, the third portion 16 comprises the second threads 13 between 50% and 30% thereof, and the complementary part (i.e., between 50% and 70% respectively) is then constituted by the first threads 12. Thus, the proportion of the second threads 13 in the third portion 16 gradually decreases until it reaches 0% near the first portion 14, while the proportion of the first threads 12 gradually increases in a complementary manner until it reaches 100% near the first portion 14.

[0067] In one embodiment, the third portion 16 extends over a length L4 between 5% and 10% of the chord length L. The length L4 of the third portion 16 may be constant over the entire height h of the blade 3 to ensure a smooth transition between the second portion 15 and the first portion 14. Alternatively, the length L4 of the third portion 16 may be generally proportional to the length of the second portion 15. In this variant, the length L4 of the third portion is maximum at the root 6 of the blade 3, and then, starting from 40% to 50% of the height h, the length of the third portion 16 may gradually decrease until it becomes substantially zero at the tip 10. Thus, starting from half the height h / 2 of the blade 3, the third portion 16 is covered by the shield 4.

[0068] The first thread 12 and the second thread 13 may include carbon fibers.

[0069] For example, the first thread 12 may include HexTow IM7 carbon fiber sold by HERCEL, which has a Young's modulus of approximately 276 GPa.

[0070] The second thread 13 may include TORAYCA T1100G carbon fiber sold by TORAY (whose Young's modulus is 294 GPa) and / or Tenax UMS45 carbon fiber sold by TEIJIN (whose Young's modulus is 425 GPa).

[0071] Figure 1 Schematically shown is a blade 3 whose fiber reinforcement 5 is formed from a three-dimensionally woven fiber preform, then injected with resin or densified by means of a matrix and possibly machined to obtain a fan 1 blade 3 made of composite material according to the invention.

[0072] Figure 1 A schematic example of the warp arrangement C1 of the fiber reinforcement 5 is already shown in Figure 3 The warp arrangement C1 is a cross-sectional view of the fiber preform at the root 6 of the blade 3 along a plane perpendicular to the stacking axis Z (see Figure 1 In the fiber reinforcement 5, each warp arrangement is separated from the adjacent warp arrangement by a row of weft lines. It should be noted that Figure 3 A warp arrangement C1 is shown, in which only the warp threads (ie, along the stacking direction of the segments) are shown, the weft threads being omitted, in order to simplify the reading of the figure. Figure 3 A first example of warp intermixing is schematically shown.

[0073] If you can Figure 3As can be seen in the figure, in the second portion 15 (herein, the second portion 15 is at the root 6 of the blade 3, extending over approximately one third of the chord length L), between 70% and 90% of the warp threads are second threads 13, the complement being made up of second threads 13. In the third portion 16, the density of the second threads 13 decreases gradually from the second portion 15 in the direction of the first portion 14 until it becomes zero (the density of the first threads 12 increases gradually in a complementary manner). In the first portion 14, 100% of the warp threads are made up of the first threads 12.

[0074] Typically, the described configuration is valid for engines whose fan 1 may have an outer diameter of about 1.8 meters to 3 meters. The number of blades 3 of the fan 1 may be equal to 16 or 18. Whatever the diameter of the fan, the number of blades 3 of the fan 1 will be reduced as much as possible. In different standards, the choice of parameters (in particular the length of the second portion 15 and the choice of the constituent material of the second wire 13) will depend more specifically on the performance of the fan blade 3 and the "frequency / detwist" combination of the blade 3.

Claims

1. A blade (3) of a fan (1) of a turbine, comprising a composite material structure, the composite material structure comprising a fiber reinforcement (5) and a matrix, the fiber reinforcement being obtained by three-dimensional weaving of warp and weft, the fiber reinforcement (5) being embedded in the matrix, - the composite material structure comprises a leading edge (8) and a trailing edge (9); - the fiber reinforcement (5) comprises a first portion (14) forming the trailing edge (9) and a second portion (15) forming the leading edge (8); and - the warp threads of the fiber reinforcement (5) comprise first threads (12) having a predetermined stiffness; The blade (3) is characterized in that the warp threads of the fiber reinforcement (5) further include second threads (13), the stiffness of the second threads is greater than the stiffness of the first threads (12), and the Young's modulus of the second threads is between 1.2 and 1.5 times the Young's modulus of the first threads (12), the first portion (14) includes all or part of the first threads (12) and does not have the second threads (13), and the second portion (15) includes all or part of the second threads (13).

2. The blade (3) according to claim 1, wherein: The warp threads of the second portion (15) further comprise a first thread (12).

3. The blade (3) according to any one of claims 1 or 2, further comprising an airfoil blade (7) adapted to extend in the airflow, the airfoil blade having a tip (10) and a root (6), the root being configured to be fixed to a disk (2) of the fan (1), wherein: The second portion (15) extends from the root (6) to the tip (10) over the entire height (h) of the blade (3).

4. The blade (3) according to claim 1 or 2, further comprising an airfoil blade (7) adapted to extend in the airflow, the airfoil blade having a tip (10) and a root (6), the root being configured to be fixed to a disk (2) of the fan (1), wherein The second portion (15) extends over a portion of a chord length (L) of the composite structure, the portion of the chord length being variable between the root (6) and the tip (10) of the blade (3).

5. The blade (3) according to claim 4, wherein: At the root (6) of the blade (3), the second portion (15) extends over a length (L1) between 25% and 40% of the chord length (L) of the composite structure.

6. The blade (3) according to claim 4, further comprising a metal shield (4) added and fixed to the leading edge (8), the second portion (15) extending beyond the metal shield (4) at the root (6) but being completely covered by the metal shield (4) at the tip (10).

7. The blade (3) according to claim 6, wherein: The second portion (15) extends beyond the metal shield (4) at the root (6) to 40% to 50% of the height (h) of the blade (3), and then the second portion (15) is completely covered by the metal shield (4) to the tip (10).

8. The blade (3) according to claim 4, wherein: At half the height (h / 2) of the blade (3), the second portion (15) extends over a length (L2) comprised between 10% and 30% of the chord length (L) of the composite structure.

9. The blade (3) according to claim 4, wherein: At the tip (10) of the blade (3), the second portion (15) extends over a length (L3) between 0% and 5% of the chord length (L) of the composite structure.

10. The blade (3) according to claim 1 or 2, wherein: The fiber reinforcement (5) further comprises a third portion (16) extending between the second portion (15) and the first portion (14), the density of the second wires (13) gradually decreasing from the second portion (15) to the first portion (14) in the third portion (16).

11. The blade (3) according to claim 10, wherein: The third portion (16) extends over a length (L4) between 5% and 10% of a chord length (L) of the composite structure.

12. The blade (3) according to claim 1 or 2, further comprising a metal shield added and fixed to the leading edge (8), the metal shield covering the second portion (15) and leaving the first portion (14) exposed.

13. The blade (3) according to claim 1 or 2, wherein: The first thread (12) and the second thread (13) include carbon fibers.

14. A fan (1) for a turbomachine, comprising a plurality of blades (3) according to any one of claims 1 to 13.

15. A turbomachine comprising at least one fan (1) according to claim 14.

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