Bladed rotor wheel for a turbine engine

Abstract

A bladed rotor wheel for a turbine engine, the rotor wheel including a disk including, formed in its outer periphery, at least one slot for mounting the roots of blades, and a spacer mounted between each blade root and a bottom of the slot. The spacer includes at least one member of type that is bistable in position and that can occupy a first stable position for assembly or disassembly in which the member does not exert force on the blade root, and a second stable position in which the bistable member exerts a radial force on the blade root. The spacer also includes at least one resilient damper member mounted between the bottom of the slot and the blade root.

Claims

1. A bladed rotor wheel for a turbine engine, the rotor wheel comprising: a disk including, formed in an outer periphery thereof, a slot for assembling a root of a blade; and a spacer mounted between the blade root and a bottom of the slot, the spacer including a member of type that is bistable in position and that can occupy a first stable position for assembly or disassembly in which the bistable member does not exert force on the blade root, and a second stable position which the bistable member exerts a radial force on the blade root for holding the blade stationary and stabilizing the blade in a final position, a resilient damper member mounted between the bottom of the slot and the blade root, the blade root configured to bear against the resilient damper member, at least prior to the bistable member occupying the second stable position, and a support of elongate shape, including a first zone in which the resilient damper member is mounted and a second zone in which a bistable spring in a form of a resilient strip is mounted, the spring being deformable between the first and second stable positions, wherein, in the second zone, the support includes a base and two branches projecting from the base, and the spring is fastened to ends of the branches.

2. A rotor wheel according to claim 1, wherein the bistable member is made of a shape memory material that is deformable by mechanical, thermal, or electrical stress.

3. A rotor wheel according to claim 1, wherein the support including at least one access opening for passing a tool for causing the bistable member to pass from the second stable position to the first stable position.

4. A rotor wheel according to claim 1, wherein the resilient damper member is in a form of at least one pad of resilient material, or of elastomer.

5. A rotor wheel according to claim 1, wherein shape and mass of the bistable member are determined so that the bistable member is caused to pass from the first stable position to the second stable position by centrifuging.

6. A rotor wheel according to claim 5, wherein the shape and the mass of the bistable member are determined so that the bistable member is caused to pass from the first stable position to the second stable position by rotating a wheel at a speed greater than 2000 rpm.

7. A rotor wheel according to claim 1, wherein, in the second zone, the support presents a generally U-shaped section in which the base is beside a bottom of the slot and the two branches project therefrom.

8. A rotor wheel according to claim 7, wherein the spring includes a flyweight.

9. A rotor wheel according to claim 7, wherein the branches of the support include grooves or notches.

10. A method of assembling and balancing a rotor wheel according to claim 1, the method comprising: assembling the blade and the spacer in an assembly position in the slot of the disk; rotating the rotor wheel at a speed that is sufficient to cause the blade to move by centrifuging into a normal operating position, and to cause the bistable member to pass into the second stable position to stabilize the blade in the operating positions; and reducing unbalance of the rotor wheel.

11. A method according to claim 10, wherein the reducing unbalance of the rotor wheel is performed by disassembling and interchanging the blade.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention can be better understood and other details, characteristics, and advantages of the invention appear on reading the following description made by way of non-limiting example and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a fragmentary section view of a rotor wheel of the invention;

(3) FIG. 2 is a perspective view of a spacer fitted to the rotor wheel of the invention;

(4) FIG. 3 is a perspective view of a portion of the spacer including a resilient damper member, in one embodiment of the invention;

(5) FIG. 4 is a view corresponding to FIG. 3 in a variant embodiment of the invention;

(6) FIG. 5 is a perspective view of a portion of the spacer including a member of bistable position, in an embodiment of the invention;

(7) FIG. 6 is a cross-section view of the spacer portion shown in FIG. 5; and

(8) FIG. 7 is a view corresponding to FIG. 6, showing a variant embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 shows a portion of a bladed rotor wheel of a turbine engine, e.g. a fan wheel, comprising a disk 1 with a plurality of substantially axial slots 2 formed in its outer periphery.

(10) Each blade 3 comprises an airfoil 4 and a dove-tailed root 5 that is engaged in the slot 2 of the disk 1, the slot being of a shape that is complementary to the shape of the blade root in order to hold the blade 3 radially on the disk 1. The blade 3 also has platforms 6 that are contiguous in order to define an inside surface of a fluid flow passage, and that are situated radially between the blade root 5 and the airfoils 4.

(11) A spacer 7 is mounted between each blade root and the bottom of the corresponding slot. As can be seen better in FIG. 2, the spacer 7 comprises a support 8 of elongate shape extending substantially along the axis A of the disk 1 and of the slot 2. In the embodiment shown, the spacer 7 has five general zones, namely two end zones 9, a central zone 10, and two intermediate zones 11 that are situated between the central zone 10 and respective ones of the end zones 9.

(12) Resilient damper members are mounted on the support in the end zones 9 and in the central zone 10. The damper zones are pads 12 of elastomer material, e.g. of ethylene propylene diene monomer (EPDM) or of silicone.

(13) FIG. 3 is a diagram showing the central zone 10 of a spacer 7 in a first embodiment of the invention in which a single pad 12 of generally rectangular block shape is mounted on the outer surface 13 of the support, facing towards the blade root.

(14) FIG. 4 shows another embodiment in which the inner face 14 (facing towards the bottom of the slot 2) and the outer face 13 (facing towards the blade root 5) are each fitted with two respective pads 12 of semicylindrical shape, and oriented along the axis A of the spacer 7.

(15) Naturally, other configurations may be envisaged, the embodiments shown merely being examples of possible embodiments.

(16) The intermediate zones 11 are fitted with members that are bistable in position.

(17) More particularly, in each of the intermediate zones 11, the support 8 presents a section that is generally U-shaped, having a base 15 beside the bottom of the slot 2 and from which there project two branches 16, a spring 17 in the form of a resilient strip being fastened via its ends 18 to the branches 16.

(18) The spring 17 is of the type that is bistable in position and it may occupy a first stable position for assembly or disassembly in which it does not exert a force on the blade root 5, and a second stable position in which it exerts a radial force on the blade root 5 in order to hold the blade stationary and stabilize it in a final position, as disclosed in document FR 11/54301.

(19) A flyweight 19 is fastened in a central zone of the spring 17, e.g. by means of a screw or by crimping.

(20) The shapes and the masses of the spring 17 and of the flyweight 19 are determined in such a manner that the transition from the first stable position to the second stable position takes place automatically by centrifuging when the rotor is rotating at a speed greater than 2000 rpm.

(21) The spring 17 may be made of a metal material presenting mechanical characteristics that are appropriate and compatible with the temperatures reached in the zones in question. The spring 17 may also be made of a shape memory material that is deformable by mechanical, thermal, or electrical stress.

(22) In the embodiment of FIG. 2, the branches 16 of the support 8 include notches 20, e.g. extending perpendicularly to the axis A, in order to adjust the stiffness of the branches 16 of the support 8 as a function of requirements.

(23) In another embodiment shown in FIGS. 5 and 6, the branches 16 include recesses or grooves 21 likewise for adjusting the stiffness of said branches 16. By way of example, the grooves 21 may be oriented parallel to the axis A or perpendicularly thereto.

(24) By way of example, the spring 17 may be fastened to the two branches 16 (FIGS. 2, 5, 6) by welding, or by any other fastening means.

(25) By way of example, FIG. 7 shows a variant embodiment in which the ends 18 of the spring 17 are curved towards the base 15 and are fastened by being embedded in the branches 16. This situation may be preferred in particular when the materials of the springs 17 and of the branches 16 are not suitable for performing a welding operation.

(26) The flyweights 19 have through holes 22 oriented along the axis of the spacer. The ends 9 of the support 8 also include access openings 23 (FIG. 2) allowing a tool to pass so that the end of the tool can be inserted through the access openings 23 into the holes 22 in the flyweights 19 for the purpose of moving the springs 17 from its position for holding the blade 3 towards its disassembly position.

(27) In a variant, the slots 2 may be curvilinear. Under such circumstances, the spacers 7 are no longer generally rectilinear in shape, but present a shape that is generally curvilinear, matching the shape of the slots 2.

(28) Furthermore, the number of zones 9, 10, and 11, and thus the number of bistable members and the number of damper members, and also their relative arrangements, may be varied as a function of constraints concerning the weights and the mechanical stresses involved.

(29) A method of assembling and balancing a rotor wheel of the invention is described in detail below.

(30) Firstly, the blades 3 are mounted together with the spacers 7 in the slots 2 of the disk 1. The springs 17 are then in their first stable positions, i.e. in their assembly and disassembly positions, and they do not exert any force on the blade roots 5. The pads 12 are compressed under the force exerted by the blade roots 5, with the pads 12 being flattened by about 0.1 millimeters (mm) to 0.3 mm, for example.

(31) Thereafter, the rotor is rotated at a speed that is sufficient to bring the blades 3 by centrifuging into a final operating position and to cause each of the springs 17 to pass into its second stable position. By way of example, this speed of rotation is about 2000 rpm to 3000 rpm.

(32) During this rotation, each spring 17 deforms from its first stable position towards its second stable position in which the middle zone of each of the springs 17 is pressed against the corresponding blade root 5.

(33) Also during this rotation, the pads 12 serve to some extent to hold the blades 3 in position before they are held by the springs 17. The ability of each blade 3 to move is thus greatly limited during this first rotation of the rotor, thereby avoiding damage to the abradable material of the outer casing.

(34) In their second stable positions, the springs 17 apply a radially outwardly-directed force against the blade roots 5 that is sufficient to hold the blades 3 in their operating position when the rotor is idling or stopped. This force is determined so as to be capable of compensating the weight of the blade 3 and also the inertial effects that occur on starting the turbine engine.

(35) It is then possible to slow down or stop the rotation of the rotor, with the blades 3 being held and stabilized by the springs 17 in their operating positions.

(36) If necessary, it is then possible to reduce any unbalance of the rotor, e.g. by disassembling and interchanging some of the blades 3. For this purpose, the operator can move the springs 17 towards their disassembly positions with the help of a tool, as mentioned above. The spacers 7 can then be withdrawn and reassembled freely.

(37) During a stage of operation, in the event of an impact against one or more blades 3, as a result of a bird or a solid body being ingested, the pads 12 are capable of damping the movement of the blades in question sufficiently and also of absorbing sufficient energy to avoid the blades being damaged.