Turbine engine blade made of composite material with a bulb-shaped root

Abstract

A turbine engine blade made of composite material including fiber reinforcement obtained by three dimensionally weaving yarns and densified with a matrix, the blade including an airfoil and a blade root forming a single part. The blade root includes two opposite lateral flanks that are substantially plane and that are clamped between two independent pads made of composite material, which pads are fastened against the lateral flanks of the blade root to form a blade root that is bulb-shaped.

Claims

1. A turbine engine blade comprising: an airfoil and a blade root forming a single part, the blade root including two opposite lateral flanks that are substantially plane, wherein the blade root is clamped between two independent pads made of composite material, which pads are fastened against the lateral flanks of the blade root to form a blade root that is bulb-shaped, wherein the blade is made of composite material comprising fiber reinforcement obtained by three dimensionally weaving yarns and densified with a matrix.

2. A blade according to claim 1, wherein each pad comprises a substantially plane lateral flank for coming into contact with a lateral flank of the blade root, and an opposite lateral flank that presents a varying profile reproducing a blade root bearing surface.

3. A blade according to claim 2, wherein the pads are obtained by molding a fiber preform and densifying the molded preform.

4. A blade according to claim 1, wherein the pads are fastened against the lateral flanks of the blade root by brazing, by co-densification, or by matrix deposition.

5. A blade according to claim 1, further comprising a platform formed integrally with the airfoil and with the blade root.

6. A blade according to claim 1, wherein the blade root and the pads are made of ceramic matrix composite material.

7. A blade according to claim 6, wherein the pads are made from fiber reinforcement based on SiC fibers.

8. A blade according to claim 2, wherein the varying profile of the opposite lateral flank of each of the pads presents a face without any cut fibers.

9. A turbine engine comprising a plurality of blades according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other characteristics and advantages of the present invention appear from the following description made with reference to the accompanying drawings, which show an implementation having no limiting character. In the figures:

(2) FIG. 1 is a view showing how a turbine engine blade in accordance with the invention is assembled;

(3) FIG. 2 is a perspective view of the FIG. 1 blade once assembled;

(4) FIG. 3 is a profile view of the FIG. 2 blade; and

(5) FIG. 4 is a section view of blade roots in accordance with the invention when mounted on a rotor disk.

DETAILED DESCRIPTION OF THE INVENTION

(6) The invention is applicable to various turbine engine blades made of composite material, and in particular to compressor blades and to turbine blades of various spools of a gas turbine engine, for example low-pressure turbine blades such as those shown in FIGS. 1 to 4.

(7) In known manner, the blade 10 as shown in these figures comprises an airfoil 12, a root 14 extended by a tang 16, and a platform 18 situated between the tang 16 and the airfoil 12. The blade could also have an outer platform (not shown) in the vicinity of its free end 20 (or tip).

(8) The airfoil 12 of the blade presents a curved aerodynamic profile that extends (in a longitudinal direction) from the platform 18 to its tip 20. This profile is of varying thickness and is made up of a pressure side surface 12a and a suction side surface 12b that are connected together transversely by a leading edge 12c and by a trailing edge 12d.

(9) The root 14 of the blade in this example is bulb-shaped and is for mounting in a slot formed in the periphery of a rotor disk by means of a dovetail type connection.

(10) The blade 10 is made of composite material, preferably of ceramic matrix composite (CMC) material. By way of example, reference may be made to International patent application number WO 2010/061140, which describes an example of fabricating a turbine engine blade by making a fiber preform by three-dimensional weaving and by densifying the preform with a matrix.

(11) More particularly, that method provides the making of a fiber blank as a single piece by three-dimensional weaving, shaping the fiber blank to obtain a fiber preform as a single piece having a first portion forming a preform for the airfoil and the root of the blade and at least one second portion forming a preform for an inner or outer platform of a blade, and then densifying the preform with a matrix. The method thus makes it possible to obtain a blade made of composite material having fiber reinforcement constituted by the preform and densified by the matrix, and forming a single piece with an incorporated (inner and/or outer) platform.

(12) By virtue of its particular fabrication method, the blade root 14 presents the shape of a plate (i.e. of a rectangular parallelepiped) with two opposite lateral flanks 22 that are substantially plane and that are formed extending the pressure side and suction side surfaces 12a and 12b respectively of the airfoil 12.

(13) According to the invention, the root 14 of the blade 10 is clamped between two independent pads 24 made of composite material, which pads are fastened against the lateral flanks 22 of the blade root so as to form a blade root that is bulb-shaped.

(14) Each of the composite material pads 24 has a lateral flank 26 that is substantially plane (referred to below as the “plane lateral flank”) for coming into plane contact against a lateral flank 22 of the blade root 14, and an opposite lateral flank 28 that presents a varying profile reproducing a blade root bearing surface (referred to below as the “profiled lateral flank”).

(15) The pads 24 are preferably obtained by three-dimensionally weaving a fiber blank, followed by molding the fiber blank in order to obtain a fiber preform for a place having the desired geometrical shapes, and then densifying the fiber preform with a matrix. In particular, the lateral face of the fiber blank corresponding to the profiled lateral flank of the pad is molded so as to give it the profile of a blade root bearing surface.

(16) The fiber blank is preferably woven so as to present a warp-to-weft ratio that is as high as possible, or indeed solely with yarns in the warp direction (the warp direction corresponding to the longitudinal direction of the blade that is to be fabricated). As a result, the stress that such a material can accept is considerably greater than the stress of the material used for fabricating the blade root.

(17) Likewise, because of the molding, the pads may be made in such a manner as to obtain a profiled lateral flank 28 of “net” shape, i.e. a face without any cut fibers. Since this is the zone of the root that is subjected to the highest levels of mechanical stress, such a net shape method greatly improves the mechanical strength of the blade root against the rotor disk.

(18) For the composite material, it is preferable to select a ceramic matrix composite material (as for making the blade). Advantageously, the fiber reinforcement is based on silicon carbide fiber sold under the name “Hi-Nicalon® of type S” by the supplier Nippon Carbon Co., Ltd. Such fibers present the advantage of locally imparting excellent mechanical strength to the blade root.

(19) Furthermore, it is possible to apply a specific surface coating to the profiled lateral flanks 28 of the pads 24 for the purpose of improving the friction behavior of the pads. This coating may be different from the coating optionally applied to the airfoil of the blade. For example, it is possible to apply coatings having a lubricating function such as graphite, CoCrAlYSi, or MoS.sub.2.

(20) The pads 24 are fastened to the lateral flanks 22 of the blade root 14 by any method known for fastening parts made of composite material. Thus, it is possible to have recourse to brazing, to co-densification, to matrix deposition, or to any other equivalent method. This fastening takes place between two surfaces that are substantially plane, thereby making it easier to perform.

(21) It should be observed that it is possible to fasten additional elements to the blade root in the same manner as for fastening the pads that give the root its bulb shape. These elements can make it possible to provide the blade with sealing and/or anti-tilting functions, thereby simplifying the provision of the blade platform. Alternatively, these elements could be directly incorporated in the pads.

(22) FIG. 4 shows blades 10 as described above that are mounted in slots 30 (or sockets) formed in the periphery of a rotor disk 32. Typically, such slots extend axially between the two lateral faces of the rotor disk, and each is of a shape complementary to the bulb shape of the blade roots.

(23) In this figure, there can be seen the warp and the weft yarns of the weaving of the fiber blanks for the blades and for the pads. In particular, compared with weaving the blade root 14, it can be seen that the fiber blanks of the pads 24 are advantageously woven solely with yarns in the warp direction, thereby significantly increasing the stress that these pads can accept.