COMPOSITE BLADE COMPRISING A PLATFORM EQUIPPED WITH A STIFFENER

Abstract

A fiber preform for a turbine engine blade and also a single-piece blade suitable for being formed using such a preform, a rotor wheel, and a turbine engine including such a blade, the fiber preform being obtained by three-dimensional weaving and comprising a first longitudinal segment suitable for forming a blade root (21), a second longitudinal segment extending the first longitudinal segment upwards and suitable for forming an airfoil portion (22), a first transverse segment extending transversely from the junction between the first and second longitudinal segments and suitable for forming a first platform (23), and a first stiffener strip extending downwards from the distal edge of the first transverse portion and suitable for forming a first platform stiffener (25).

Claims

1. A fiber preform for a turbine engine blade obtained by three-dimensional weaving, the preform comprising: a first longitudinal segment suitable for forming a blade root; a second longitudinal segment extending the first longitudinal segment upwards and suitable for forming an airfoil portion; a first transverse segment extending transversely from the junction between the first and second longitudinal segments and suitable for forming a first platform; and a first stiffener strip extending downwards from the distal edge of the first transverse portion and suitable for forming a first platform stiffener.

2. A preform according to claim 1, wherein the first stiffener strip is of varying width.

3. A preform according to claim 1, wherein the first stiffener strip extends all along the distal edge of the first transverse segment.

4. A preform according to claim 3, wherein the first stiffener strip is of minimum width where the width of the first transverse segment is at a maximum; and the first stiffener strip is of maximum width where the width of the first transverse segment is at a minimum.

5. A preform according to claim 3, wherein, on going along the distal edge of the first transverse segment, the width of the first stiffener strip increases while the width of the first transverse segment decreases, and decreases while the width of the first transverse segment increases.

6. A preform according to claim 5, wherein the width of the first stiffener strip in a given longitudinal plane is inversely proportional to the width of the first transverse segment in said longitudinal plane.

7. A preform according to claim 1, wherein the first stiffener strip forms an angle with the first transverse segment, the angle lying in the range 60° to 89°, and preferably in the range 75° to 85°.

8. A preform according to claim 1, including a second transverse segment extending transversely from the junction between the first and second longitudinal segments in line with and away from the first transverse segment, and suitable for forming a second platform, and a second stiffener strip extending downwards from the distal edge of the second transverse segment, suitable for forming a second platform stiffener.

9. A preform according to claim 8, wherein the first transverse segment is suitable for forming the suction side platform of the blade and the second transverse segment is suitable for forming the pressure side platform of the blade; wherein the first stiffener strip suitable for forming the stiffener of the suction side platform is of width that is greater in its middle zone than at its upstream and downstream ends; and wherein the second stiffener strip suitable for forming the stiffener of the pressure side platform is of width that is smaller in its middle zone than at its upstream and downstream ends.

10. A turbine engine blade comprising: a blade root; and an airfoil portion extending upwards from the blade root; a platform extending transversely from the airfoil at a junction between the blade root and the airfoil portion; and a stiffener in the form of a strip extending downwardly along the distal edge of the platform.

11. A turbine engine blade comprising: a blade root; an air foil portion extending upwards from the blade root; a platform extending transversely from the airfoil at a junction between the blade root and the airfoil portion; and a stiffener in the form of a strip extending downwardly along the distal edge of the platform, wherein the blade is made as a single piece out of composite material by means of a fiber preform according to claim 1, said preform having been shaped in a mold and embedded in a matrix, preferably a matrix of organic type.

12. A blade wheel for a turbine engine including a plurality of blades according to claim 11.

13. A turbine engine including at least one blade according to claim 11.

14. A turbine engine including at least one bladed wheel according to claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are diagrammatic and seek above all to illustrate the principles of the invention.

[0043] In the drawings, from one figure to another, elements (or portions of an element) that are identical are identified by the same reference signs.

[0044] FIG. 1 is a view in axial section of a turbine engine of the invention.

[0045] FIG. 2 is a fragmentary diagram in radial section of a rotor wheel of the invention.

[0046] FIG. 3 is a perspective view of a blade in one embodiment.

[0047] FIG. 4 is a fragmentary view of the pressure side of the FIG. 3 blade.

[0048] FIG. 5 is a fragmentary view of the suction side of the FIG. 3 blade.

[0049] FIG. 6 is a diagram showing the preform corresponding to this embodiment of a blade prior to being shaped.

[0050] FIG. 7 is a diagram showing the preform corresponding to this embodiment of a blade after it has been shaped.

DETAILED DESCRIPTION OF EMBODIMENTS

[0051] In order to make the invention more concrete, embodiments are described in detail below with reference to the accompanying drawings. It should be understood that the invention is not limited to these examples.

[0052] FIG. 1 is a section view on a vertical plane containing the main axis A of a bypass turbojet 1 of the invention. From upstream to downstream in the flow direction of the air stream, it comprises a fan 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6, and a low pressure turbine 7.

[0053] As shown in FIG. 2, the fan 2 has a plurality of fan blades 10 mounted angularly around the axis A on a disk 11 that is connected to the low pressure shaft of the turbine engine 1.

[0054] Such a fan blade is shown in FIG. 3. It has a blade root 21 of dovetail shape configured to engage in a slot 12 in the disk 11 in order to fasten it to the disk 11. The blade root 21 is extended outwards by an airfoil 22 presenting a suction side face 22e and a pressure side face 22i, each extending from upstream to downstream between a leading edge 22a and a trailing edge 22f.

[0055] The blade 10 also has a suction side platform 23 extending transversely between the suction side of the blade from the junction between the blade root 21 and the airfoil 22, and a pressure side platform 24 extending transversely beside the pressure side of the blade from the junction between the blade root 21 and the airfoil 22.

[0056] In accordance with the invention, each platform 23, 24 is also provided with a stiffener 25, 26. As can be seen more clearly in FIGS. 4 and 5, each of these stiffeners is in the form of a flange constituted by a strip or a rim extending radially all along the distal edge of the corresponding platform 23, 24; more precisely, each stiffener 25, 26 extends inwards from the distal edge of its platform 23, 24, i.e. it extends downwards in the reference frame of the blade, forming an angle λ relative to the platform 23, 24; a rounded connection may be provided between the stiffener 25, 26 and the platform 23, 24.

[0057] As shown in FIG. 2, this angle λ is substantially equal to half the angular difference μ between two blades 10 within the rotor wheel 2. By way of example, if the wheel 2 has one blade 10 every 20°, then the stiffeners 25, 26 form an angle λ of 10° relative to the platforms 23, 24. In this way, when the blades 10 are mounted on the disk 11 of the rotor wheel 2, the suction side and pressure side platforms 23 and 24 of each consecutive pair of blades follow one another in continuous manner and their stiffeners 25 and 26 bear against each other, ignoring operating clearance, over all or practically all of their surface areas.

[0058] Furthermore, as can be seen in FIGS. 4 and 5, the width L5 and L6 of each of the stiffeners 25, 26 varies along its platform 23, 24 as a function of the width L3, L4 of the platform. More precisely, in a given longitudinal plane, the wider the platform 23, 24, the narrower its stiffener 25, 26. Still more precisely, the width of a given stiffener 25, 26 varies along the distal edge of the corresponding platform 23, 24 in a manner that is inversely proportional to the width of the platform 23, 24.

[0059] As can be seen in FIG. 4, because of the concave curvature of the suction side face of the blade 10, the suction side platform 24 possesses a width L4 that, going from upstream to downstream, increases up to a substantially middle zone of the airfoil 22 and then decreases down to the trailing edge 22f: under such circumstances, the width L6 of the stiffener 26 decreases from its upstream edge to that middle zone, and then increases once more going to its downstream end.

[0060] Conversely, as can be seen in FIG. 5, because of the convex curvature of the suction side face of the blade 10, the suction side platform 23 possesses a width L3 that, going from upstream to downstream, decreases to a substantially middle zone of the airfoil 22 and then increases to the trailing edge 22f: under such circumstances, the width L5 of the stiffener 25 increases from its upstream end as far as that middle zone, and then decreases once more to its downstream end where, given the great width of the suction side platform 23, it becomes zero or practically zero.

[0061] In this example, the blade 10 is obtained as a single piece by three-dimensional weaving of a fiber preform 30, and by injecting an organic resin using the resin transfer molding (RTM) method known to the person skilled in the art.

[0062] FIG. 6 shows this three-dimensionally woven preform 30 suitable for making this embodiment of a blade 10. FIG. 7 shows the same preform 30 after it has been shaped. The preform 30 is described from bottom to top, i.e. from upstream to downstream in the weaving direction T. Nevertheless, it should be understood that weaving could be performed starting from the other end and going in the opposite direction.

[0063] In this embodiment, the preform 30 is three-dimensionally woven out of carbon fibers using a 3D interlock weave. Only the surfaces of the preform 30 are woven two-dimensionally using a satin type weave.

[0064] At the bottom end, the weaving begins by making a first longitudinal segment 31 that is to form the root 21 of the blade 10.

[0065] Above this first longitudinal section 31, there begins a zone of non-interlinking D in which a first free flap 33a, a second longitudinal segment 32, and a second free flap 34a are woven jointly in non-interlinked manner with respective non-interlinking planes 43 and 44. Weaving methods that make such non-interlinking possible are now well known in the field of 3D weaving.

[0066] Layer exits may also be formed along the weaving direction T between the second longitudinal segment 32 and each of the free flaps 34a, 34b in order to refine the second longitudinal segment 32 and thus the future airfoil 22. Weaving methods that enable such layer exits to be provided are nowadays well known in the field of 3D weaving.

[0067] Once the weaving has been finished, the free flaps 33a and 34a are cut to size so that the first flap forms a first transverse segment 33 that is to form the suction side platform 23 of the blade 10 and a first stiffener strip 35 that is to form the suction side stiffener 25, and the second flap forms a second transverse segment 34 that is to form the pressure side platform 24 of the blade 10 and the second stiffener strip 36 that is to form the pressure side stiffener 26.

[0068] It should be observed at this point that the terms “transverse” and “longitudinal” are given relative to the final position of the segment under consideration, the transverse segments being necessarily woven longitudinally before being folded transversely.

[0069] Once the free flaps 33a and 34a have been cut to size, the floating yarns that result from the layer exits located in the surface of the second longitudinal segment 32 are accessible and can be shaved off.

[0070] The preform 30 may be moistened in order to make it more flexible and in order to make it easier to move the fibers out of register. The preform is then placed in a shaping mold with inside space that matches the shape desired for the preform 30.

[0071] The preform 30 is then dried so that it becomes stiff, thus blocking the shape imposed during shaping. Finally, the preform 30 is placed in an injection mold having the dimensions desired for the final blade 10, and a matrix is injected into that mold, specifically an epoxy resin is injected. Such injection may be performed using the known RTM method, for example.

[0072] At the end of this step, a blade 10 is obtained that is made of composite material comprising a preform 30 woven out of carbon fibers embedded in an epoxy matrix. Machining steps may optionally be used to finish off the method and obtain the final blade 10.

[0073] Naturally, the weaving example described above is merely one example amongst many other possibilities that the person skilled in the art will recognize easily. In particular, it is possible to imagine other zones of non-interlinking or to use other weaving techniques such as crossed layers, layer exits, or thickness transitions in order to obtain a preform of analogous shape. The person skilled in the art will in particular find numerous examples of weaving in Document WO 2014/076408.

[0074] The embodiments described in the present description are given by way of non-limiting illustration, and in the light of this description, a person skilled in the art can easily modify these embodiments, or can envisage others, while remaining within the scope of the invention.

[0075] Furthermore, the various characteristics of these embodiments can be used singly or in combination with one another. When they are combined, these characteristics may be combined as described above or in other ways, the invention not being limited to the specific combinations described in the present description. In particular, unless specified to the contrary, a characteristic described with reference to one particular embodiment may be applied in analogous manner to some other embodiment.