Turbomachine blade for unshrouded fan rotors

Abstract

Turbomachine blade comprising a sleeve (13) including a fixing wall (18) positioned between an external radially annular flange (29) and an internal radially annular flange (29') and configured to be connected to a shimming mechanism, a recess (17) delimited by the fixing wall including a first bearing surface area (32) adjacent to the external radially annular flange and a second bearing surface area (34) adjacent to the internal radially annular flange, a fibrous structure (20) including a blade root (22) including an attachment portion (23) inserted in the recess (17), an insert (24) inserted in a cavity (1) of the attachment portion to press the root against the fixing wall, the first bearing surface area having a first external diameter D1 and the second bearing surface area having a second external diameter D2 smaller than the first external diameter D1. Fig. 3.

Description

Title of the invention: Turbomachine blade for unshrouded fan rotors technical field

[0001] The present invention relates generally to the field of turbomachinery, and in particular to turbomachine blades.

[0002] The invention relates more particularly, but not exclusively, to a blade intended for use in an unfaired fan rotor of an aircraft engine. Prior art

[0003] The advantage of engines with unshod fans is that the fan diameter is not limited by the presence of a shroud, making it possible to design an engine with a high bypass ratio (known as the "By Pass Ratio" or BPR), and consequently reduced fuel consumption. Thus, in this type of engine, the fan blades can have a large span.

[0004] In addition, these engines generally include a mechanism for changing the angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0005] However, the design of such blades requires taking into account opposing constraints.

[0006] On the one hand, the sizing of these blades must allow for optimal aerodynamic performance, in particular maximizing efficiency and providing thrust while minimizing losses. Improving the aerodynamic performance of the fan tends towards an increase in the bypass ratio, which translates into an increase in the external diameter, and therefore the span, of these blades.

[0007] On the other hand, it is also necessary to ensure resistance to the mechanical stresses that may be exerted on these blades. Since the engine is not enclosed in a fairing, the angle of incidence experienced by the various fan blades, depending on their angular position, varies according to the aircraft's angle of attack, creating a cyclic bending moment (commonly called the IP moment) on the blades. This cyclic bending moment then generates high bending stresses on the blades in addition to the centrifugal forces due to their rotation and the torsional forces induced by aerodynamics.

[0008] Consequently, the span of the blades cannot be increased indefinitely and especially not at the expense of resistance to these mechanical stresses.

[0009] To increase the dilution rate, it would be necessary to decrease the ratio between the diameter of the hub carrying the blades and the external diameter of the blower. The Since the external diameter of the blower cannot be increased, one solution would be to decrease the diameter of the hub.

[0010] However, the diameter of the hub is optimized to resist torsional forces and cannot be reduced beyond a minimum to allow it to ensure resistance to centrifugal, torsional and particularly bending forces on the blades. Description of the invention

[0011] The invention therefore aims to resolve at least in part these drawbacks by proposing a blade in particular for an unfaired fan rotor of an aircraft engine having a higher dilution ratio than prior art rotors without reducing its resistance to mechanical stresses.

[0012] The invention relates to a blade for a turbomachine comprising: - a sleeve comprising a fixing wall positioned between an external radially annular flange and an internal radially annular flange of the sleeve and configured to be connected to a variable stalling mechanism of the turbomachine, a recess formed inside the sleeve and delimited by the fixing wall, the fixing wall comprising a first bearing surface area adjacent to the external radially annular flange and a second bearing surface area adjacent to the internal radially annular flange, - a fibrous structure comprising a blade root having an attachment portion inserted into the recess of the sleeve, a cavity formed in the attachment portion and a blade connected to the blade root, and - an insert inserted into the cavity of the attachment portion to press the blade foot against the fixing wall of the sleeve.

[0013] The first bearing support area has a first external diameter DI and the second bearing support area has a second external diameter D2 which is smaller than the first external diameter DI.

[0014] The invention thus provides a blade in particular for an unfaired fan rotor of an aircraft engine having a higher dilution ratio than prior art rotors without reducing its resistance to mechanical stresses.

[0015] Reducing the diameter of the sleeve at the location of the internal bearing without reducing the diameter of the sleeve at the location of the external bearing makes it possible to decrease the overall diameter of the hub and consequently to decrease the ratio between the diameter of the hub and the external diameter of the blower and therefore to increase the dilution rate.

[0016] In some embodiments, the attachment portion of the blade foot includes a blade foot wall delimiting the cavity, the blade foot wall having a thickness which decreases radially towards a free end of the sleeve.

[0017] The narrowing of the blade root wall from the attachment portion towards the free end of the sleeve makes it possible to maintain a blade root wall thickness at the level of the external bearing which corresponds to a minimum required to ensure resistance of the blade root to centrifugal, torsional and particularly bending forces on the blades while allowing the blade root wall diameter to be reduced at the level of the internal bearing.

[0018] This reduction in the diameter of the blade root wall at the level of the internal bearing makes it possible to decrease the overall diameter of the hub and consequently to decrease the ratio between the diameter of the hub and the external diameter of the blower and therefore to increase the dilution rate.

[0019] Reducing the thickness of the blade root wall at the level of the internal bearing is possible because only centrifugal and torsional forces are taken up at this point, in particular by the blade root wall.

[0020] The transfer of bending forces, which are the most important forces, is ensured at the level of the external bearing, in particular by the blade root wall which retains a conventionally used thickness.

[0021] The invention also allows a reduction in the weight of the blade and therefore of the turbomachine.

[0022] In some embodiments, the blade root comprises an intermediate section extending between the radially external annular flange of the sleeve and the blade, and a locking portion configured to fit into a recessed portion of the fixing wall, the blade root wall having a thickness that decreases radially towards the locking portion, between the intermediate section and the locking portion of the blade root.

[0023] In certain embodiments, the blade root wall comprises a radially external portion connected to the intermediate section and positioned opposite the first bearing area, and a radially internal portion connected to the locking portion and positioned opposite the second bearing area, the radially external portion having a thickness el and the radially internal portion having a thickness e2 less than the thickness el.

[0024] In some embodiments, the radially external portion is connected to the radially internal portion by an intermediate portion having a thickness that gradually decreases towards the blocking portion.

[0025] In certain embodiments, the intermediate portion comprises a first face in contact with the insert and substantially parallel to a blade alignment axis, and a second face, opposite to the first face, in contact with the fixing wall of the sleeve and inclined relative to the first face.

[0026] In some embodiments, the thickness e2 of the radially internal portion is greater than or equal to one quarter of the thickness el of the radially external portion and less than the thickness el.

[0027] In some embodiments, the blocking portion is inclined relative to the radially internal portion and has a thickness e2.

[0028] In some embodiments, the sleeve fixing wall includes a connecting portion linking the first bearing area and the second bearing area which is inclined with respect to the blade alignment axis.

[0029] The invention also relates to a turbomachine comprising at least one blade as defined above.

[0030] The terms “internal” and “external” are defined with respect to the radial position of the elements with respect to an axis of rotation X of the hub.

[0031] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description of examples of blade embodiments. This detailed description refers to the attached drawings. Brief description of the drawings

[0032] The attached drawings are schematic and are intended primarily to illustrate the principles of the exposition.

[0033] On these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0034] [Fig-1] Fig. 1 schematically represents a blower blade assembled to a a stabilization mechanism, according to one embodiment of the invention;

[0035] [Fig.2] Fig.2 schematically represents a radial cross-sectional view of a blade root of the blade of [Fig.1] held between a sleeve and an insert;

[0036] [Fig.3] The [Fig.3] schematically represents a more detailed view of the blade root of the [Fig.2]. Description of the implementation methods

[0037] To make the explanation more concrete, an example of a blade is described in detail below, with reference to the accompanying drawings. It should be noted that the invention is not limited to this example.

[0038] The invention is applicable to turboprop type architectures comprising at least one unshrouded fan rotor (“Open Rotor” in English).

[0039] As illustrated in [Fig. 1], the fan rotor comprises a hub 6 rotatably mounted relative to a turboprop nacelle and a plurality of blades 7. The The blades 7 are fixed to the hub 6. The blades 7 extend substantially radially with respect to an axis of rotation X of the hub 6.

[0040] The fan further comprises a variable pitch mechanism 8 for collectively adjusting the pitch angle of the blades 7 to adapt the turboprop engine's performance to different flight phases. For this purpose, each blade 7 comprises a blade root 9 and a blade 12 with an aerodynamic profile. The blade root 9 is rotatably mounted relative to the hub 6 about a pitch axis Y, substantially perpendicular to the axis of rotation X. More specifically, the blade root 9 is rotatably mounted within a mounting device 10 formed in the hub 6, by means of balls 11 or other rolling elements of bearings.

[0041] The blade 12 is designed to extend into an air stream of the engine, when the engine is running, in order to generate lift. Conversely, the blade root 9 is designed to extend out of the air stream.

[0042] As illustrated in Figures 2 and 3, the blade 7 includes a sleeve 13 having a fixing part 14 configured to be connected to the variable pitching mechanism 8 of the turbomachine, in particular inside the attachment device 10. The sleeve 13 has a recess 17 delimited by a fixing wall 18.

[0043] The blade 7 also includes a fibrous structure 20 obtained by three-dimensional weaving. The fibrous structure 20 includes a blade root 22 comprising an attachment portion 23 configured to be inserted into the recess 17 formed by the attachment portion 14 of the sleeve 13.

[0044] The fibrous structure 20 also includes a blade 12 with an aerodynamic profile connected to the blade root 22.

[0045] A cavity 1 is formed in the attachment portion 23 of the blade foot 22. The cavity 1 is delimited by a blade foot wall 2.

[0046] The fixing part 14 has a rotational symmetry about the alignment axis Y. Furthermore, the fixing part 14 has an external surface 30 having different reliefs.

[0047] The fastening part 14 has at its end through which the attachment portion 23 is inserted a radially external annular flange 29.

[0048] The fixing part 14 also includes a radially internal annular flange 29' at its free end opposite to the end through which the fibrous structure 20 is inserted.

[0049] The fixing wall 18 is positioned between the radially external annular flange 29 and the radially internal annular flange 29'.

[0050] The mounting wall 18 has a shape of revolution and comprises a first bearing surface area 32 adjacent to the radially external annular flange 29 and a second bearing surface area 34 adjacent to the annular flange radially internal 29'. Each bearing surface area 32, 34 is intended to receive a bearing.

[0051] Alternatively, the first bearing surface 32 may include a first circular groove and the second bearing surface 34 may include a second circular groove, thus forming a raceway for at least one bearing, for example, a ball bearing. The mounting portion 14 thus allows the blade foot 9 to be rotatably mounted within the attachment device 10 provided in the hub 6.

[0052] The sleeve 13 is preferably metallic and monolithic.

[0053] The blade 7 also includes an insert 24 which is configured to be inserted into the cavity 1 of the blade foot 22 and to press the blade foot wall 2 against the fixing wall 18 of the sleeve 13.

[0054] The blade 7 is thus formed of few elements which fit together to form a single-piece blade. Since the blade 12 and the blade root 22 are formed by the same fibrous structure 20, there is no discontinuity between the blade 12 and the blade root 22. Furthermore, as the blade root 22 is wedged between the insert 24 and the sleeve 13, the fibrous structure 20 is thus securely joined to the blade root 9.

[0055] The blade 7 can thus withstand significant aerodynamic forces while having a limited mass and can thus be used with a variable pitching mechanism 8 and in an unshod fan rotor environment.

[0056] The blade root 22 further comprises an intermediate section 25 which extends around a continuation of the attachment portion 23. The intermediate section 25 is formed by the same fibrous structure 20 as the blade 12 and the attachment portion 23. Thus, the attachment portion 23 on the one hand, and the intermediate section 25 on the other hand, are formed by the continuation of strands forming the blade 12. This continuity between the blade 12 and the attachment portion 23, and between the blade 12 and the intermediate section 25, allows the blade 7 to resist the aerodynamic forces to which it is subjected in an optimized manner.

[0057] The fibrous structure 20, and in particular the blade 12, is suitable for being placed in an airflow when the engine is in operation in order to generate lift.

[0058] The intermediate section 25 extends between the radially external annular flange 29 of the sleeve 13 and the blade 12.

[0059] The recess 17 has a circular cross-section that widens as it approaches a free end 39 of the sleeve 13, and from the vicinity of the radially internal annular flange 29' of the sleeve 13. The mounting wall 18 then includes a recessed portion 18' which widens the recess 17 in a direction perpendicular to the Y alignment axis. The recessed portion 18' is delimited by a beveled sleeve wall 38 of the fixing wall 18.

[0060] The attachment portion 23 of the blade root 22 includes a locking portion 23' which is also beveled and fits into the recessed portion 18'. The beveled sleeve wall 38 of the sleeve 13 forms a stop for the locking portion 23' of the attachment portion 23 of the blade root 22.

[0061] The insert 24 includes a beveled insert wall 21. The blocking portion 23' of the attachment portion 23 of the blade foot 22 also forms a stop for the beveled insert wall 21 of the insert 24.

[0062] In this way, when the insert 24 is positioned in the recess 17, any translation of the attachment portion 23 outwards, that is to say away from the free end 39 of the sleeve 13, or in other words towards the radially external annular flange 29, is prevented by the beveled sleeve wall 38 of the sleeve 13 which forms a stop.

[0063] Indeed, when the fan is rotating, the blade 7 is subjected to centrifugal forces oriented in a radial direction with respect to the axis of rotation X of the hub 6, which tend to separate the blade 12 from the sleeve 13. The blocking portion 23' helps to prevent the separation of the blade 12 from the sleeve 13.

[0064] The attachment portion 23 of the blade root 22 has rotational symmetry. The blade root wall 2 has a thickness that decreases radially (along the y-axis of this alignment) as it approaches the free end 39 of the sleeve 13 or as it moves away from the intermediate section 25, i.e., towards the interior of the engine or the axis of rotation X of the hub when the blade is mounted on the engine. The thickness of the blade root wall 2 decreases between the intermediate section 25 and the locking portion 23' of the blade root 22.

[0065] Preferably, the thickness of the blade root wall 2 decreases between the first bearing area 32 and the second bearing area 34.

[0066] The blade root wall 2 comprises a radially external portion 3 connected to the intermediate section 25 and positioned opposite the first bearing area 32, and a radially internal portion 4 connected to the locking portion 23' and positioned opposite the second bearing area 34. The radially internal portion 4 has a thickness e2 less than a thickness el of the radially external portion 3.

[0067] The radially external portion 3 is also positioned opposite the radially external annular flange 29 of the sleeve 13, and the radially internal portion 4 is also positioned opposite the radially internal annular flange 29' of the sleeve 13.

[0068] The thickness e2 of the radially internal portion 4 is greater than or equal to one quarter of the thickness el of the radially external portion 3 and is less than the thickness el.

[0069] The radially external portion 3 is connected to the radially internal portion 4 by an intermediate portion 5 having a thickness which gradually decreases towards the second bearing area 34 or towards a free end 39 of the sleeve 13, i.e. towards the inside of the motor or the axis of rotation X of the hub when the blade is mounted on the motor, from the thickness e1 to the thickness e2.

[0070] The intermediate portion 5 includes a first face 36 in contact with the insert 24 and which is substantially parallel to the alignment axis Y of the blade 7. The intermediate portion 5 includes a second face 37, opposite to the first face 36, which is in contact with the fixing wall 18 of the sleeve 13 and which is inclined with respect to the first face 36 at an angle between 1° and 30° and preferably between 5° and 20°.

[0071] The thickness el is between 15 mm and 30 mm.

[0072] The radially external portion 3 comprises a first face 40 parallel to the first face 36 of the intermediate portion 5. The radially internal portion 4 comprises a second face 41 parallel to the first face 40. The first and second faces 40, 41 are inclined with respect to the second face 37 of the intermediate portion 5.

[0073] The fixing wall 18 of the sleeve 13 conforms to the shape of the blade foot wall 2. Consequently, the fixing wall 18 at the location of the first bearing area 32 opposite the radially external portion 3 and the fixing wall 18 at the location of the second bearing area 34 opposite the radially internal portion 4 are parallel to the alignment axis Y.

[0074] The fixing wall 18 of the sleeve 13 includes a connecting portion 35 linking the first bearing support zone 32 and the second bearing support zone 34. The connecting portion 35 is inclined with respect to the alignment axis Y and runs along the second face 37 of the intermediate portion 5 of the blade root wall 2.

[0075] The radially internal portion 4 of the blade root wall 2 has an external diameter that is smaller than the external diameter of the radially external portion 3.

[0076] Consequently, the first bearing support area 32 has a first external diameter DI and the second bearing support area 34 has a second external diameter D2 which is smaller than the first external diameter DI.

[0077] The ratio between the first external diameter DI and the second external diameter D2 is between 1 and 1.4.

[0078] The thickness e1 of the radially external portion 4 is sufficient to allow the absorption of bending forces and the thickness e2 of the radially internal portion 3 is sufficient to allow the recovery of tensile forces due to centrifugal and torsional forces.

[0079] This reduction in diameter at the level of the second bearing area 34 allows the use of bearing rings with smaller diameters than those of the prior art and reduces the overall diameter of the hub 6. The ratio between the diameter of the hub and the external diameter of the blower is therefore reduced and the dilution rate is increased.

[0080] The blocking portion 23' of the blade root wall 2 is inclined with respect to the radially internal portion 4 and has a thickness e2.

[0081] The insert 24 is preferably metallic.

[0082] The insert 24 comprises a first cylindrical part 42 connected to a locking end 44 and a free end 43, opposite the locking end 44. The locking end 44 is, in this embodiment, a rounded end.

[0083] The insert 24 also includes a frustoconical part 45 connected to the cylindrical part 42 and formed by the beveled insert wall 21. The beveled insert wall 21 is connected to a second cylindrical part 46 comprising the free end 43.

[0084] In an alternative (not shown), the insert 24 comprises a single cylindrical part of constant circular cross-section extending from the blocking end 44 to the free end 43. The blocking portion 23' of the blade root wall 2 is then formed by an overthickness having a thickness increasing radially from the radially internal portion 4 to a free end of the blade root wall 2.

[0085] An example of a method for manufacturing the blade 7 is described below.

[0086] The process includes a step of producing the fibrous structure 20 comprising the attachment portion 23 by three-dimensional weaving, the attachment portion 23 being produced by forming unlinks in the weaving.

[0087] Preferably, this step also includes the manufacture of the intermediate section 25 in the fibrous structure 20 by also making unlinking in the weave.

[0088] The decreasing thickness to form a preform of the blade foot wall 2 is achieved by a variation in the number of layers of woven fiber.

[0089] The method then includes a step of inserting the attachment portion 23 into the recess 17 of the sleeve 13 and positioning the attachment portion 23 against the fixing wall 18.

[0090] The insert 24 is positioned in the cavity 1 so as to block the attachment portion 23 against the fixing wall 18.

[0091] Once the fibrous structure 20, the sleeve 13 and the insert 24 are assembled, the blade 7 thus formed is inserted into a mold to obtain a preform with an aerodynamic profile.

[0092] The process includes a step in which a liquid resin is injected into the mold according to a resin transfer molding process (“Resin transfer molding” (RTM) in English) to obtain the blade 7. The resin can be in particular an epoxy resin, a thermoplastic resin or a polybismaleimide (BMI) resin.

[0093] During the injection of the resin, the latter impregnates the entire fibrous structure 20 and thus inserts itself in particular between the insert 24 and the fixing wall 18. The resin thus makes it possible to maintain the different assembled elements, namely the fibrous structure 20, the sleeve 13 and the insert 24, in a single block.

[0094] Alternatively, it is possible to add a film of glue between the fibrous structure 20 and the insert 24 or between the fibrous structure 20 and the sleeve 13. The glue film improves the transmission of torsional forces.

[0095] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

[0096] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. Blade (7) for a turbomachine comprising: - a sleeve (13) having a mounting wall (18) positioned between an external radially annular flange (29) and an internal radially annular flange (29') of the sleeve (13) and configured to be connected to a variable pitching mechanism (8) of the turbomachine, a recess (17) formed inside the sleeve (13) and delimited by the mounting wall (18), the mounting wall (18) comprising a first bearing surface area (32) adjacent to the external radially annular flange (29) and a second bearing surface area (34) adjacent to the internal radially annular flange (29'), - a fibrous structure (20) comprising a blade root (22) having an attachment portion (23) inserted into the recess (17) of the sleeve (13), a cavity (1) formed in the attachment portion (23) and a blade (12) connected to the blade root (22),and - an insert (24) inserted into the cavity (1) of the attachment portion (23) to press the blade foot (22) against the fixing wall (18) of the sleeve (13), in which the first bearing surface area (32) has a first external diameter DI and the second bearing surface area (34) has a second external diameter D2 which is smaller than the first external diameter D1.

2. Blade (7) according to claim 1, wherein the attachment portion (23) of the blade foot (22) comprises a blade foot wall (2) delimiting the cavity (1), the blade foot wall (2) having a thickness which decreases radially towards a free end (39) of the sleeve (13).

3. Blade (7) according to claim 2, wherein the blade root (22) comprises an intermediate section (25) extending between the radially external annular flange (29) of the sleeve (13) and the blade (12), and a locking portion (23') configured to fit into a recessed portion (18') of the fixing wall (18), the blade root wall (2) having a thickness that decreases radially towards the locking portion (23'), between the intermediate section (25) and the locking portion (23') of the blade root (22).

4. Blade (7) according to claim 3, wherein the blade root wall (2) comprises a radially external portion (3) connected to the intermediate section (25) and positioned opposite the first bearing area (32), and a radially internal portion (4) connected to the locking portion (23') and positioned opposite the second bearing area (34), the radially external portion (3) having a thickness el and the radially internal portion (4) having a thickness e2 less than the thickness el.

5. Blade (7) according to claim 4, wherein the radially external portion (3) is connected to the radially internal portion (4) by an intermediate portion (5) having a thickness that gradually decreases towards the blocking portion (23').

6. Blade (7) according to claim 5, wherein the intermediate portion (5) comprises a first face (36) in contact with the insert (24) and substantially parallel to a shimming axis (Y) of the blade (7), and a second face (37), opposite to the first face (36), in contact with the fixing wall (18) of the sleeve (13) and inclined with respect to the first face (6).

7. Blade (7) according to any one of claims 3 to 6, wherein the blocking portion (23') is inclined relative to the radially internal portion (4) and has a thickness e2.

8. Blade (7) according to any one of claims 6 or 7, wherein the fixing wall (18) of the sleeve (13) includes a connecting portion (35) linking the first bearing support area (32) and the second bearing support area (34) which is inclined with respect to the staking axis (Y) of the blade (7).

9. Turbomachine comprising at least one blade (7) according to any one of claims 1 to 8.

Images