Composite blade for a turbine engine rotor

Abstract

The invention relates to a composite blade (5) for a turbine rotor, for example unducted propeller, comprising a skin (6) made of woven fibers and forming the external profile of the blade, and an attachment piece (11) having a cylindrical geometry in the direction of the span starting from the blade root (9), intended to hold the blade (5) on the hub of the rotor, characterized in that the composite blade further comprises a spar (16) having the structure of a hollow tube made of woven carbon fibers, fixed to the attachment piece (11) and extending on at least a part of the span of the blade (5) inside the skin (6). The invention also relates to a propeller comprising said blade and to a method for manufacturing said blade.

Description

Technical Field

[0001] This invention relates to rotor blades for turbine engines. More particularly, this invention relates to ductless propellers for turbine engine architectures, such as open rotor types (i.e., ductless propellers with ductless fans). Open rotor architectures include counter-rotating open rotors (CRORs) with two rows of counter-rotating propellers, unducted single fan (USF) engines, or turboprop engines. Background Technology

[0002] Prior art includes, in particular, documents EP-B1-0610273, EP-A2-2679487, US-A-3923421 and FR-A1-2954271.

[0003] Based on a typical architecture, such as in Figure 1 As shown, an open rotor turbine engine (more precisely, a USF) may include a single propeller 1 upstream of a downstream fixed stator blade 2. The turbine engine driving the propeller is located inside a cowling that carries the stator blade 2. The blades of the propeller 1 are typically variable pitch, meaning that the propeller blades rotate about a radial axis on the propeller hub, and the attachment of the propeller blades to the hub must be designed for this purpose.

[0004] The detailed design of such blades involves multiple disciplines with often conflicting objectives. The design must achieve optimal aerodynamic performance, i.e., providing thrust with minimal loss for different flight conditions, while ensuring the mechanical strength of the blades with minimal mass and limiting their acoustic characteristics.

[0005] Improved aerodynamic performance of propellers tends to increase the ratio of the moving airflow to the airflow passing through the engine, which translates into an increase in the outer diameter of the blades, and therefore an increase in the blade span.

[0006] In open rotor and USF architectures, the propeller blades transmit very high torque to the propeller hub. Furthermore, aerodynamic optimization and acoustic considerations for the blades result in a thin blade design where the blade profile and pitch vary along the blade span.

[0007] In addition, ductless propellers are subjected to forces whose intensity can vary greatly depending on flight conditions and may fluctuate violently under some conditions.

[0008] Furthermore, in ductless architectures, the aerodynamic flow through the blades is strongly influenced by the engine's mounting on the aircraft and the overall upstream flow direction (e.g., the angle of attack relative to the wind). This can lead to, for example:

[0009] - Because there is no cowling, the engine is affected by the ground and the surrounding fuselage, and the engine mounting causes distortion, resulting in asymmetrical propeller feed rates based on the engine azimuth angle. This leads to a vibrational response in the first engine order, according to the spatial Fourier series decomposition of the distortion on the circumference; and - during the aircraft's climb or approach phase, due to the lack of a cowling, the direction of the flow through the blades is not parallel to the engine axis, resulting in increased sensitivity to crosswinds or the aircraft's angle of attack. This slip angle causes a vibrational response in the first engine order.

[0010] Furthermore, in open rotor, USF, and turboprop engine architectures, based on existing propeller technology, engine startup occurs at a very open pitch. In fact, a very open pitch (known as feathering) allows power to be dissipated through torque, which ensures machine safety by maintaining a low propeller speed (rotational speed). More precisely, by simple consideration, power is proportional to the product of speed and torque; and this torque increases with the angle of attack (and therefore with the pitch relative to the propeller plane). Aerodynamic forces increase with increasing angle of attack because this increases the deflection of the flow tended by the profile. Moreover, those skilled in aerodynamics should understand that for a very open pitch, the forces generated on the blade profile are almost perpendicular to the direction of incidence. Most of the generated forces are directed towards the propeller plane, resulting in zero thrust from the propeller, maximum torque, and minimum speed.

[0011] On the other hand, with such a wide pitch and angle of attack, the blades experience turbulence (a completely non-adhesive aerodynamic flow that generates broadband vibrational excitation). In particular, on blades with large chord lengths and wide spans, the bending forces are strong even at low speeds.

[0012] However, according to the prior art of the aforementioned turbine engine architecture, the blade 3 is attached by a pin-connected attachment 4, which is elongated along the blade chord at the horizontal position at the root of the blade, as in... Figure 2 As shown in the figure. This solution allows forces to be absorbed over a large length of the attachment and is adapted to thin composite propeller blades 3, suitable for turbine engines covered by the present invention.

[0013] However, at present, pin-fitted attachments do not seem to be a viable solution for propeller blades with large chord lengths and large spans.

[0014] The purpose of this invention is to provide a solution for obtaining composite blades suitable for open rotor, USF, and turboprop engine architectures, wherein the composite blades have sufficiently rigid root attachments to withstand broadband vibration stresses caused by fully lifted aerodynamics, as well as vibrations caused by torsion due to engine mounting or forces caused by the incident angle of the upstream flow. Summary of the Invention

[0015] Therefore, the present invention relates to a composite blade for a turbine engine rotor, such as a ductless propeller, the composite blade comprising a skin and an attachment, the skin being made of woven fibers and forming the outer profile of the blade, the attachment having a cylindrical geometry in the direction of the span starting from the blade root, the attachment being intended to hold the blade on the hub of the rotor, characterized in that the composite blade further comprises a spars having a hollow tube structure made of woven carbon fibers, the spars being fixed to the attachment and extending inside the skin over at least a portion of the blade span.

[0016] Preferably, the spars extend from the blade root at a distance between 30% and 70% of the span. The blade span is here understood as the distance between the blade root at the level of the leading edge and the blade tip at the level of the leading edge.

[0017] The cylindrical root attachment can be sized to withstand broadband vibrational stresses caused by fully lifted aerodynamics and vibrations caused by torsion (installation effects), as well as forces caused by the angle of incidence and wind slip. However, to achieve sufficient rigidity for the assembly, the installation of such an attachment according to the prior art results in a blade structure with a thick profile across the entire blade span. A woven fiber sparsity provides a rigid structure attached to the attachment, which absorbs forces across a portion of the blade span to provide sufficient rigidity for the assembly. Furthermore, the woven fiber structure of the sparsity is stretchable during manufacturing, allowing the sparsity to be flattened from the root to create a propeller blade with a thin profile across most of the span, compatible with designs such as open-rotor type turbine propellers.

[0018] Advantageously, the attachment includes a bell-shaped portion inserted at one end of the spar. Preferably, a fiberglass winding surrounds said end of the spar to secure the spar around the bell-shaped portion.

[0019] Inserting the bell-shaped portion into the hollow tube of the spar allows lateral forces to be absorbed over a sufficient distance. Furthermore, the bell-shaped portion and the fiberglass winding ensure the spar is held in place against centrifugal forces. Under centrifugal force, the fiberglass acts as a tension element due to the open shape of the bell-shaped portion. Although the spar is preferably inserted tightly around the bell-shaped portion, the fiberglass winding ensures the connection between the spar and the attachment.

[0020] Preferably, the attachment is made of a metallic material, and even more preferably, of martensitic steel.

[0021] This type of material allows for attachments with sufficient rigidity and a relatively small diameter to limit the thickness at the blade root. Furthermore, the material enables the mechanical connecting elements to be manufactured together with the rotating system on the hub to change the blade pitch for integration into variable-pitch propellers.

[0022] Therefore, advantageously, the attachment includes at least one reinforcement designed to form a ring for the ball, so that the blade can pivot relative to the hub about an axis parallel to the span of the blade.

[0023] Preferably, the foam-shaped portion ensures the interface between the spar and the skin.

[0024] The foam-shaped section allows the blades to take shape and ensures that the skin is held in place in a way that resists overturning caused by centrifugal force.

[0025] Preferably, the interior of the spar is filled with a foam-shaped section.

[0026] Because the foam-shaped section can be gradually tapered and the spars can be flattened around the shape during manufacturing, the foam-shaped section allows the shape of the hollow spars to match the overall shape of the blade in terms of pitch and thickness, thus ensuring the thickness of the blade profile.

[0027] The blade may include an integral part of woven skin at the blade tip, which does not include inserted spars or foam.

[0028] This allows for very fine blade tips, with the spars fulfilling their structural function on the portion of the blade near the root.

[0029] The present invention also relates to a turbine engine propeller comprising blades as described above.

[0030] The present invention also relates to a method for manufacturing the blade as described above, the method comprising weaving a preform for the skin, characterized in that the method includes the steps of manufacturing an assembly, inserting the assembly into the skin preform, and forming the blade with the final shape of the blade by a resin transfer molding method known as RTM, the assembly comprising a woven preform of hollow spars fixed together and a cylindrical attachment.

[0031] Therefore, the formation of the spars and attachment assemblies enables the blade to be rigidized while absorbing vibrations at the blade root. The resin transfer molding method and the polymerization stage of the resin transfer molding method enable the different components of the blade to be joined together.

[0032] Advantageously, the weaving of the prefabricated skin is accomplished by interlacing the warp and weft threads and forming a detachment on a portion of the skin, the detachment being arranged to allow the insertion of an assembly including the woven spar prefabricated components and attachments.

[0033] Preferably, the unwinding is achieved at the trailing edge, which does not weaken the structure of the final blade, while allowing the insertion of the spar to be well controlled within a possible foam-shaped section that follows the internal contour of the woven skin.

[0034] Preferably, when assembling the attachment assembly and the preform of the spar weaving, the foam-shaped portion is inserted into the preform of the spar weaving so that the preform of the spar weaving conforms to the final shape of the blade profile. Attached Figure Description

[0035] Other features and advantages of the invention will become apparent from the following detailed description, and with reference to the accompanying drawings, in order to understand the description:

[0036] [ Figure 1 ] Figure 1 This is a schematic perspective view of an open rotor type turbine engine involved in this invention;

[0037] [ Figure 2 ] Figure 2 It is used for Figure 1 A schematic side view of the blades of a turbine engine propeller, according to the prior art;

[0038] [ Figure 3 ] Figure 3 It is used for Figure 1 A schematic side view of the blades of a turbine engine propeller according to the invention;

[0039] [ Figure 4 ] Figure 4 It is inserted into Figure 3A schematic side view of the spars in the blade and the attachments of the spars, with the attachments of the spars attached to the root of the blade.

[0040] [ Figures 5A to 5B ] Figure 5A yes Figure 3 A schematic cross-sectional view of the leaf near the root (along...) Figure 6 (The cross section of line A in the diagram); Figure 5B yes Figure 3 A schematic diagram of the cross-section of a leaf in the main body of the leaf away from the root (along...) Figure 6 (The cross section of line B in the middle);

[0041] [ Figure 6 ] Figure 6 yes Figure 3 A schematic side view of the blade, showing its internal structure; and

[0042] [ Figure 7 ] Figure 7 This occurs during the weaving process of the prefabricated components. Figure 3 A schematic diagram of the longitudinal structure of the prefabricated blade skin. Detailed Implementation

[0043] Reference Figure 3 The composite propeller blade 5 according to the invention includes a woven skin 6 made of carbon fiber, which forms the aerodynamic surface of the blade 5 and contacts the air moved by the propeller. The skin 6 forms the convex and concave surfaces of the blade 5, which are connected to the leading edge 7 and the trailing edge 8. The weave of the skin 8 includes warp and weft threads, with the warp threads oriented longitudinally from the root 9 toward the head 10 and the weft threads oriented transversely along the chord of the blade 5. Specifically, at the level of the leading edge 7, a good path for the weft threads is ensured by an interlocking method to ensure a good connection between the convex and concave portions of the skin 8 at that level. Other features of the weave of the skin 6 are described later in the description of the method of manufacturing the blade 5.

[0044] The profile of blade 5 is relatively thick at the level of the root 9 and becomes thinner along the span toward the blade tip 10. The blade 5 in this example has almost no deflection, but other examples may have positive or negative deflection. Furthermore, blade 5 is shown here in radial projection, but the blade may have tilt and twist around the radial axis, which are not shown in the accompanying drawings.

[0045] According to the invention, at the root 9 of the blade 5, a cylindrical attachment 11 (also referred to as the root) about the radial axis R is partially inserted between the arched back and arched belly surfaces of the woven skin 6. The portion 12 of the attachment 11 inserted between the two surfaces of the skin 6 is bell-shaped and flares outward along the direction of the head 10 of the blade 5. A second portion 13 outside the blade profile defined by the woven skin 6 is shaped to mount the blade 5 in a propeller hub and to allow the blade to rotate about the radial axis R to change the pitch. Here, the second portion 13 of the attachment 11 is designed to be mounted on a device with two rolling lines and to serve as an inner ring. Schematably, the groove 14 at the bottom of the attachment 11 is intended for the inner ring of the first row of beads (large beads absorbing centrifugal force), and the groove 15 near the bell-shaped portion 12 is intended for the inner ring of the second row of beads (small beads absorbing aerodynamic forces).

[0046] The device can be reversed by arranging the balls bearing radial forces on top and the balls bearing secondary forces on the bottom. This arrangement can be made for integrated constraints.

[0047] The attachment 11 is made of a metallic material, preferably martensitic steel, to withstand the force between the blade 5 and the hub of the propeller.

[0048] Also according to the invention, the spar 16 extends between the arched ventral and arched abaxial surfaces of the skin 6, over a large portion of the span of the blade 5, and is attached to the bell-shaped portion 12 of the attachment 11. In the example shown, the spar extends to approximately two-thirds of the span. Preferably, depending on the design choice, the length of the spar 16 is between 30% and 70% of the span of the blade 5, where 0% corresponds to the radius of the blade root at the level of the leading edge 9, and 100% corresponds to the radius of the head 10 at the level of the leading edge. The spar 16 is a hollow tube made of woven carbon fiber. Figure 5A and Figure 5B As shown, at the level of the root 9 of the blade 5, where the thickness of the profile allows, the spar has an almost circular cross-section, and the cross-section of the spar gradually flattens outward to reach the area where the profile of the blade 5 is thinner in the body of the blade 5.

[0049] Reference Figure 4 The spar 16 is inserted around the bell-shaped portion 12 of the attachment 11, and here is wound around the attachment by a glass fiber winding portion 17. This winding enables the blade to resist centrifugal force. Here, glass fiber is an example, and the winding must be made of fibers selected by those skilled in the art based on the existing mechanical constraints.

[0050] In addition, refer to Figure 5AIn this foam-shaped section 18, the interior of the spars 16 is filled. Similarly, foam 19 fills the space between the blade's spars and skin. Figure 6 In the diagram, the free volume filled with foam 19 is shown by dashed lines 20 within the boundaries of the free volume in the longitudinal and transverse directions.

[0051] The component is injected with resin and polymerized using a known resin transfer molding (RTM) method to achieve its mechanical strength. Other features of blade 5 are described below in the description of the blade manufacturing method, which uses the RTM method.

[0052] In the steps preceding the method itself, the metal attachment 11 and the bell-shaped portion 12 of the metal attachment can be machined by conventional methods.

[0053] Therefore, the method includes two steps that can be executed in parallel.

[0054] The first of these two steps involves the assembly of the prefabricated spar 16 with the attachment 11.

[0055] The first step involves weaving a preform of the spar 16, which is made of carbon fiber on an industrial weaving machine. The preform is a hollow tube open at both ends. The cross-section of the tube can be circular with a variable diameter, specifically to subsequently adapt the cross-section of the spar 16 to the thickness variation of the blade 5 profile along the span.

[0056] The prefabricated spar 16 is then assembled with the bell-shaped portion 12 of the attachment. The assembly of the prefabricated spar 16 with the bell-shaped portion 12 is accomplished by inserting the bell-shaped portion 12 into the prefabricated spar 16 and then fabricating the previously described fiberglass winding portion 17. Preferably, these operations are performed around the very cold bell-shaped portion 12 by forcing the bell-shaped portion 12 into the prefabricated spar 16.

[0057] The previously machined foam component 18 can then be inserted into the preform of the spar 16. The function of the foam component 18 is to fill the cavities left inside the preform of the spar and to ensure the final shape of the spar 16 during the forming of the blade 5. Note that the foam component 18 can be non-cylindrical. In this case, as described above, the preform of the spar 16 may be compressed into a thinner portion of the blade profile. The foam component 18 can be stopped before the free end of the preform of the spar 16.

[0058] At the end of this step, a fixed assembly is obtained, which includes a prefabricated part of the attachment 11 and the spar 16, the spar prefabricated part integrating the foam shape 18 that the spar will surround into the blade.

[0059] The second step in the first step involves weaving the prefabricated parts used for weaving the skin 6.

[0060] Reference Figure 7 As described previously, this is essentially a conventional weave, in which warp threads 21 extend in the span direction and weft threads 22 extend around the profile in a generally perpendicular direction. The weaving of the preform is achieved using carbon fiber on an industrial loom. Thickness connections or "interlocking" are achieved by creating specific weft paths 22 between the warp threads 21.

[0061] Reference Figure 7 The preform of the skin 6 includes a lower portion 23 and an upper portion 25. The lower portion begins from the root 9 and has a cleaving portion 24 at its horizontal level. The upper portion includes an integral head. Here, the cleaving portion 4 is a longitudinally extending line along which the weft thread stops, allowing the preform to open along this line to allow the preform of the spar 16 to pass through.

[0062] Figure 6 The diagram shows a possible form of the detachment portion 24 with a constant skin thickness 6, as well as the detachment portion at the trailing edge 8. This detachment portion 8 also... Figure 5A and Figure 5B As shown in the cross-section, the detachment is used only to open the prefabricated skin 6 for inserting the spar. The shape of the detachment 24 is chosen to ensure proper insertion of the spar. Furthermore, depending on the strategy regarding skin thickness in the detachment, the shape of the detachment 24 is more or less extended.

[0063] For these reasons, the unwinding is achieved at the level of the trailing edge, rather than, for example, at the leading edge, where the woven preforms are fully interwoven or interlocked along the leading edge 7.

[0064] In order to allow the spar to be inserted, the disassembly part 24 covers the area where the spar is integrated.

[0065] Therefore, the span of the lower portion 23 of the spar is designed to be at least equal to the span of the spar 16. The upper portion 25 is integral. On the one hand, the skin 6 has no detachment; on the other hand, the thickness of the skin 6 does not allow for gaps between the two sides, as this part is entirely made of woven carbon fiber. Figure 6 The dashed line 26 in the figure shows the boundary of this part 25 when viewed from the side.

[0066] Reference Figure 7The weaving strategy involves initiating the weaving of the original prefabricated skin 6 through the root 9 by integrating all the warp threads 21 required for weaving the component into the false root 27.

[0067] Once the prefabricated component is woven, the float is trimmed, followed by waterjet cutting to remove the false root 27. The result is an opening at the root 9 to prepare for receiving the assembly of the attachment 11 and the prefabricated component 16 of the wing spars.

[0068] As with conventional precast parts, once the false root 27 is removed, the original precast part still has excess length. Excess length exists at the head, leading edge, and trailing edge levels. On the lower portion of the skin 6, the ability to rework after injection is limited due to its assembly onto the spar and bell-shaped section. However, small excess lengths may be present except in the vicinity of the root 9.

[0069] Following the previous two steps, the third step involves the shaping and injection of blade 5.

[0070] The attachment 11, the prefabricated spar 16, and the foam-shaped part 18 assembly are inserted into the woven prefabricated part of the skin 6 at the level of the unraveling part 24. A pre-machined foam structure 19 can be used at the interface between the prefabricated part of the skin 6 and the prefabricated spar 16. The geometry of this interface part 19 can be designed to ensure the centrifugal retention of the skin 6.

[0071] The component is then injected and polymerized using the RTM method to obtain a blank for blade 5.

[0072] The final steps in the manufacturing process are cutting and finishing.

[0073] It should be noted that resin overflow may occur during polymerization at excessive lengths. Resin overflow is eliminated during rework, which includes trimming the leading edge 7 and trailing edge 8, as well as trimming the blade head 10.

[0074] This step typically also includes rework at the lower part of the blade (on the hub line), because rework must be done precisely for assembly with attachment 11.

[0075] Alternatively, the method is accomplished by bonding the installed trailing edge and / or leading edge and protective film to the skin.

Claims

1. A composite blade (5) for a turbine engine rotor, the composite blade comprising a skin (6) and an attachment (11), the skin being made of woven fibers and forming the outer profile of the composite blade, the attachment having a cylindrical geometry in a direction spanning from the blade root (9), the attachment being intended to hold the composite blade (5) on the hub of the rotor, the composite blade (5) extending radially between the head and the blade root (9). Its features are, The composite blade also includes a sparsity (16) having a hollow tube structure made of woven carbon fiber, the sparsity being fixed to the attachment (11) and extending over at least a portion of the span of the composite blade (5) within the skin (6). The skin (6) includes a lower part (23) and an upper part (25). The lower part (23) starts from the root (9) of the blade and has an unraveling part (24) at the horizontal level of the lower part. The lower part (23) surrounds the spar (16). The upper part (25) includes the head (10) of the composite blade, which is an integral part of the woven skin and does not include the spar (16). The tip of the composite blade is located away from the tip of the spar.

2. The composite blade (5) according to claim 1, characterized in that, The attachment (11) includes a bell-shaped portion (12) inserted at one end of the spar (16).

3. The composite blade (5) according to claim 1 or 2, characterized in that, The attachment (11) is made of metal.

4. The composite blade (5) according to claim 3, characterized in that, The attachment (11) is made of martensitic steel.

5. The composite blade (5) according to claim 1 or 2, characterized in that, Foam (19) fills the space between the spar (16) and the skin (6) of the composite blade (5).

6. The composite blade (5) according to claim 1 or 2, characterized in that, The interior of the wing spars is filled with a foam-shaped section (18).

7. The composite blade according to claim 1 or 2, characterized in that, The attachment (11) includes at least one reinforcement (14, 15) designed to form a ring for the ball.

8. The composite blade according to claim 1 or 2, characterized in that, The spar (16) extends inside the skin (6) from the blade root (9) at a distance between 30% and 70% of the span.

9. The composite blade according to claim 1, characterized in that, The turbine engine rotor is a ductless propeller.

10. The composite blade according to claim 2, characterized in that, A fiberglass winding (17) surrounds the end of the spar (16) to secure the spar around the bell-shaped portion (12).

11. A turbine engine propeller comprising composite blades (5) according to any one of claims 1 to 10.

12. A method for manufacturing a composite blade (5) according to any one of claims 1 to 10, the method comprising weaving a preform for the skin (6), characterized in that, The method includes the steps of manufacturing the component, inserting the component into the preform of the skin, and forming the composite blade (5) having the final shape of the composite blade by a resin transfer molding method known as RTM. The component includes a preform of hollow spar (16) fixed together and a cylindrical attachment (11).

13. The method according to claim 12, wherein, The weaving of the prefabricated parts of the skin (6) is accomplished by interlacing the warp (21) and weft (22) and forming a detachment (24) on the lower part (23) of the skin, the detachment being arranged to allow the components including the woven prefabricated parts of the wing beam and the attachment (11) to be inserted.

14. The method according to claim 13, characterized in that, The detachment (24) is formed at the rear edge (8) of the preform of the skin.

15. The method according to any one of claims 12 to 14, wherein, When assembling the attachment (11) and the woven preform of the spar, the foam-shaped part (18) is inserted into the woven preform of the spar (16) so that the woven preform of the spar conforms to the final shape of the outline of the composite blade (5).

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