FR3118991A1 - TURBOMACHINE TURBINE ASSEMBLY - Google Patents

Abstract

This concerns a turbomachine rotor assembly comprising a rotor disc (20) adapted to rotate around an axis (X) and having on the periphery cells (50) each having a bottom; vanes (90) having roots (110) individually disposed in said cells; and shims (130) each interposed between a root (110) of one of said blades and the bottom (70) of a cell. The shims (130) incorporate damping devices (52) with a return effect, to push the blade roots (110) radially outwards. Figure to be published with abstract: Figure 3

Description

TURBOMACHINE TURBINE ASSEMBLY

The present disclosure relates to a turbomachine rotor assembly comprising a substitute for the shims which are conventionally interposed between the blade roots and the disc cells adapted to receive them. It also relates to a turbomachine comprising such an assembly and to a method of mounting, with good positioning, the blades in the cells of the disc.

More specifically, the invention relates to an assembly for a turbomachine, comprising:
- a rotor disc adapted to rotate around an axis (X) and having in the radially outer periphery cells each having a bottom;
- blades having feet arranged individually in said cells, and
- wedges, each wedge being interposed between a root of one of said blades and the bottom of a cell.

In the present application, an axial direction is defined as being a direction parallel to the axis (denoted below X) of rotation of the rotor disk, and therefore of the blades. The upstream and downstream of a part are defined with respect to the normal direction of gas flow passing between the blades. Orientation qualifiers, such as “longitudinal,” “radial,” and “circumferential,” are defined by reference to the axis of rotation (X). Radially, exterior is that which is farther from the axis (X) than interior.

A known example of an assembly of the aforementioned type and disclosed in EP2042689 is shown partially, in exploded view, on the .

This is a known rotor assembly 10, which may belong to the fan module (or "fan" module) of an aircraft turbojet engine.

The turbomachine kit shown includes:
- A rotor disk 2 adapted to rotate around an axis (X) and therefore having, in the radially outer periphery, cells 5 each having a bottom 7;
- blades 9 having feet 11 arranged individually in the cells 5, and
- wedges 13, each interposed between a root 11 of blade 9 and the bottom 7 of a cell 5.

A lock 15 is also provided, or even a foil 17.

The rotor assembly 10 is shown assembled in the .

To assemble the assembly 10, the shim 17 is first mounted (if it exists) on the blade root 11, by sliding the latter by the upstream of the blade, following the arrow F (see ). The shim 17 thus envelops the blade root 11, the side branches 17a (see ) foil respectively covering the side surfaces 11a of the blade root. The surfaces of the blade roots and the cells 5 (ie of the disc 2) which come into abutment against each other, under the effect of the centrifugal forces during the rotation of the assembly 10.

Next, the blade root 11 (and the shim 17 which surrounds it, if present) is slid into a cell 5. Downstream, the blade 9 abuts axially against a front wall 19 of the drum of the turbojet low-pressure compressor (see ).

Then the lock 15 is positioned in front of the blade root 11 (i.e. its upstream side), against the blade root 11, or against the shim 17 (if it exists and is provided with a frontal edge 18).

For its maintenance, the lock can be inserted into a slot 13a of the wedge 13, transverse to the X axis and located just downstream of a hook or rim 13b erected radially towards the upstream end of the wedge 13.

Finally, the wedge 13 is slid between the bottom of the foot 11 of the blade (or the foil 17 if it exists) and the bottom 7 of the cell 5. The lock 15 is then retained between the rim 13b upstream of the wedge 13 and the root 11 of the blade, which makes it possible to prevent the axial displacement of the shim 17 (if present) with respect to the root 11 of the blade.

For the record, it is recalled that a foil, such as that 17, is an intermediate part between the blade and the rotor disc. It is a kind of sock which envelops the root 11 of the blade and which makes it possible to fill the clearance between the root of the blade and the rotor disc. This backlash may exist from the start (i.e. from the design of the blade and the disc) but it may be due to a mechanical recovery of disc 1 being repaired.

These parts, and at least the shims 13, represent a compromise between the capacity of each shim to be mounted simply in the cavity 5 of the disc 2 and the holding force exerted on the blade 9.

Each part, and therefore at least 13 wedges, represent an additional cost of design, production, supply, assembly and maintenance.

Integrating the wedges 13 (or at least some of their functions), or even parts associated with them (such as the locks 15 and/or the shims 17) into the parts that will replace them, could allow overall simplifications of the interfaces and cost reduction.

Summary

To this end, a turbomachine rotor assembly is proposed comprising:
- a rotor disc adapted to rotate around an axis (X) and having, in the radially outer periphery, cells each having a bottom;
- blades having feet arranged individually in said cells; And
- wedges, each interposed between a foot of one of said blades and the bottom of a cell,
characterized in that the wedges define damping devices with a return effect, to push the blade roots radially outwards.

These damping devices can also be called resilient.

This should make it possible to functionalize the holds by improving their efficiency, or even their implementation, by aiming for overall simplification of the interfaces and a reduction in certain costs.

The blade roots may be pushed radially outwards all the more as they have been forced radially inwards. So the effectiveness of the solution can increase with the efforts exerted operationally.

To best combine efficiency, ease of implementation and cost, it is proposed that the damping devices include springs.

Even if other alveolar or cellular materials could be used, a cushioning device comprising a foam can also promote the best efficiency, ease of implementation and costs. Foam is easy to shape. Its damping or resilient effect is controllable. A foam can have different densities and/or hardnesses and/or thicknesses at different places in its volume.

It will be understood that the term "foam" means "solid foam", that is to say a cluster of bubbles separated from each other by solid walls, and not liquid. In other words, it is a plastic material or an elastomer that comes in a cellular or alveolar form.

To best absorb the radial forces with a means whose behavior can be well controlled, it is proposed that the springs be compression springs oriented to act radially.

To further promote the implementation of damping devices (ease of installation, or even removal for maintenance or replacement), it is proposed that the damping device concerned comprise a foam and several springs, the foam being interposed between the springs and the blade root and/or the bottom of the cell.

For a balancing of the forces undergone by the blades and transmitted to the disc, and of the return effect vis-à-vis these, it is proposed:
- that, parallel to a direction of elongation of the cell in which it is arranged, the corresponding blade root has a direction of elongation along which the springs are arranged along several lines, and/or,
- that circumferentially, and therefore transversely to this direction of elongation of the corresponding blade root, the springs are arranged along several lines.

To promote damping or resilience with also an effect in a direction other than radial and/or to also facilitate the implementation of the damping device concerned, it is proposed that the foam surrounds the springs circumferentially (including in the direction: all around).

For a comparable purpose, it is also proposed that the foam contain cavities where the springs are arranged.

Maintaining the springs and overall ease of handling are expected. On this subject, it is also proposed that a means of adhesion make the foam and the springs adhere.

To promote balancing of the forces and the expected damping, it is also proposed that, parallel to a direction of elongation of the cell in which a said blade root is arranged, the corresponding blade root has:
- A direction of elongation along which the springs are arranged along a line, the line can be unique; and or
- a length (L3) (see ), the damping device then extending in one piece over more than 75% of the length (L3) of the blade root.

For a comparable purpose, and more generally to be able to further refine the control of the behavior of the damping device, it is also proposed:
- that the foam has different densities and/or hardnesses and/or thicknesses at different places, and/or
- that the springs have different stiffnesses between them.

In particular, in the same cell, the springs can usefully have different stiffnesses between them: per cell, the springs will then exert different radial forces in different places of the blade root and of the disk cell.

Thus it is possible, if necessary cell by cell, to optimize the reaction of the springs, according to the forces undergone, according to the location considered, and in particular parallel to the direction of elongation of the cell and/or parallel to the axis X.

The invention also concerns an aeronautical turbomachine comprising the assembly provided with all or part of the above characteristics.

And in the context of the proposed method of mounting turbomachine blades on a rotor disk of this turbomachine, which disk is therefore adapted to rotate around an axis (X) and has, at the radially outer periphery, cells each having a bottom , the blades having feet, it is recommended:
- to produce damping devices with a return effect;
- to insert these damping devices in the cells and to hold them there, each forced into a state in which it is compressed radially to the axis (X);
- to insert the roots of the blades in said cells, so that, in the cells, the damping devices are interposed between the roots of the blades and the bottoms of the cells; And
- To release the aforementioned radial compression stresses of the damping devices in the cells, so that the damping devices then act radially outwards, on the blade roots.

It is even offered:
- To carry out said restraints under stress of the damping devices by inserting into the cells tongues which compress radially to the axis (X) the damping devices against the bottoms of the cells; Then,
- To ensure said release of these radial compressive stresses of the damping devices, to remove the tongues from the cells, by sliding them along the respective cells.

An industrial implementation, well controllable, easily reproducible, applicable both in original equipment and in maintenance, and effective in terms of the effect to be achieved is expected.

Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

partially represents, in exploded view, a known example of a rotor assembly;

shows in axial section, the rotor assembly of the in assembled condition;

is a partial schematic front view of part of a rotor assembly, as shown in the arrow III of the , after replacement, in this example and for the blade illustrated, at least of the wedge 13, the shim 17 and the lock 15, by a wedge 130 integrating one or more damping devices with a return effect in accordance with invention;

is a schematic view of a wedge part according to the invention seen along section IV-IV of the , according to an exemplary embodiment;

is a view of part of a rotor assembly according to the invention seen along the line LL of the , according to an exemplary embodiment;

is a schematic view of a tab for positioning, radially constrained, a damping device according to the invention,

is a schematic view of a turbofan engine whose fan may include the solution of the invention, for example in the embodiment of the .

Reference is now made to FIGS. 3 to 7 which partially represent, for FIGS. 3 and 5, a turbomachine rotor assembly 100 which can be implemented in a turbomachine with a longitudinal axis X which can correspond to the axis X cited above; see Figures 1.2 and to that of .

The common parts or parts between the aforementioned example of the prior art, and therefore of Figures 1, 2, and the solution of the invention presented below, with reference to the example of Figures 3-5, which correspond carry the same reference numerals, with a trailing zero added for the solution of the invention shown. Thus, the turbomachine rotor assembly 10 becomes the assembly 100.

As schematized , the turbomachine rotor assembly 100 may in particular be a fan turbine engine fan rotor (FAN) 101 arranged upstream of a LP (low pressure) compressor 102, itself followed axially by a compressor HP (high pressure) 104, then a combustion chamber 106, an HP turbine 108 then a LP turbine 111. The low pressure and high pressure compressors 102, 104, the combustion chamber 106 and the high pressure and low pressure 108, 110 are located in a so-called primary vein 114. A so-called secondary vein 116 extends around the primary vein 114, downstream of the fan 101. The secondary vein 116 extends radially to the axis X, between a radially outer casing 118 and a radially inner casing 120 surrounding the low pressure compressor 102.

Mounted on a known turbofan engine 112 and thus designed, the rotor assembly 100 will typically be such that the HP turbine 108 will drive the HP compressor 104 and the LP turbine 111 will drive the LP compressor 102 and the fan 101.

Thus, the rotor assembly 100 may be identical to the turbomachine rotor assembly 10 presented, except that, in the cavities 50 existing in the radially outer periphery 30 of the disk 20, the shims 130 concerned incorporate damping devices 52 at recall effect.

Preferably in each cell 50, there is a spacer 130 incorporating at least one damping device 52 with a return effect.

As before, the wedges 130 are individually still interposed between a root 110 of one of said blades 90 and the bottom 70 of the cell 50 where this blade root is arranged.

Thus, the roots 110 of the blades 90 will be pushed radially outward, particularly if they are radially inwardly constrained, when the rotor assembly 100 rotates about the X axis.

Individually, the damping devices 52 preferably include:
- a resilient coating material, and/or
- springs 22.

Thus, opposite each root 110 of blade 90, the damping device 52 comprises a foam 24.

The foam 24 can serve as a resilient encapsulating material.

Care will be taken to adapt the shape of the damping device 52, and in particular of the foam 24, to the particular shape of the cell 50 of the disc 20, and in particular of its bottom 70, so that the respective shapes noticeably match.

The foam 24 can be polyethylene. It can be a reticulated closed-cell foam made of polyethylene, also called polyethylene or polyolefin or emalene foam. A trade name is “Plastazote” (registered trademark).

A foam 24 of the cellular foam type may also be suitable.

A range of these two foam options exist, each with variations on the following properties: nominal density, nominal hardness and thickness.

A hybrid foam with heterogeneous properties can also be envisaged to adapt in particular to variations in forces following (in particular) the axial direction.

In this regard, the foam 24 can therefore usefully have different densities and/or hardnesses and/or thicknesses at different places.

Thus, it is possible to provide blocks of different types of foam, joined together for example by gluing and having different densities and/or a block of the same foam of different thicknesses at different places.

You may wish to use a "high density foam" to hold the pre-tension applied by the springs. Just as for springs, and in particular their stiffness(es) - see below - a fairly wide range of mechanical properties can be proposed: E _t (tensile modulus) between 200 and 500 MPa; E _c (modulus in compression) between 75 and 110 MPa; G (shear modulus) between 35 and 75 MPa and ν (Poisson's coefficient) of the order of 0.3 (between 0.2 and 0.4).

To optimize the management of the forces in question, it may be preferred that, per blade foot 110, the damping device 52 comprises a foam 24 and several springs 22.

By blade foot 110, the foam 24 will then be interposed between the springs 22 and the blade foot 90, and/or the bottom of the cell 70, located radially opposite.

With several springs 22 per blade root 110 and parallel to a direction of elongation L1 of the slot 5 considered, in which a blade root 110 is arranged, it will be possible to usefully organize the springs 22 so that they are arranged along several parallel lines, along the same direction of elongation L2 along which the root 110 of the blade extends.

The directions of elongation L1 and L2 can therefore be confused and extend parallel to the X axis.

We can thus all the better promote a balancing of the forces and the expected damping.

For a potentially comparable effect, ease of manufacture and/or handling, it is also recommended that, per blade foot 110, foam 24 circumferentially surrounds each spring 22.

In connection with the foregoing, the foam 24 may contain cavities 26 where the springs 22 are arranged.

One spring 22 per cavity 26 can stabilize each spring as well as possible.

Per cell 50, and therefore opposite a single blade root 110, it is also useful to find a single block of foam 24 provided with a succession of cavities 26 organized as follows:
- several parallel lines, along the same general direction of elongation L2, and
- several lines transverse to the general direction of elongation L2 (therefore along the circumference C), while being parallel to each other; see figures 3 and 5 for an example.

A cavity or cell 26 may be provided every 10 to 20 mm for a length L3 of foot 110 (see below) of approximately 300 to 310 mm and a cavity or cell 26 every 10 mm for a section of foot width C1 about 60 to 65mm; see figures 4 and 5. C1 almost corresponds to the curvilinear distance between the lateral bearing surfaces 70a of a cell 50, to the sliding clearance of the foot 110 in the cell.

To promote a precise directional effect, easy manufacture and/or limited bulk, it is proposed, as in , that the springs 22 are compression springs oriented to act radially (axis Z).

Spiral springs 22 are suitable.

The springs 22 will each be a priori metallic.

In this regard, a wide range of coil springs commonly used in aeronautics can be used, focusing on the Young's modulus E, the shear modulus G and the density values.

The following intervals can be proposed, per spring: E (Young's modulus) between 100 and 400 GPa; G between 40 and 160 GPa and a density between 7 and 9 g/cm ³ .

For the stabilizing effects, balance and control and transfer of efforts already mentioned, it is also proposed:
- that parallel to the direction of elongation L1 or L2, the (each) blade root 110 considered has a length L3,
- And that the damping device 52, disposed in the cell 50 which receives it, extends in one piece over more than 75% of the length L3 of said root 110 of the blade.

The length L3 will a priori be common to all the feet 110 of blade of the turbomachine rotor considered, over the entire circumference of this rotor.

To again facilitate the handling of the damping devices 52, and more generally the implementation of the wedges 130, provision is made for an adhesion means 28 to make the foam 24 and the springs 22 adhere.

The adhesion means 28 can be an adhesive.

Now concerning the method that can be recommended for mounting the blades 90, each in one of the cells 50 of the rotor disc 20, it can be implemented as follows:
- a) first, at least as many damping devices 52 with a return effect are provided as there are cells 50 on the circumference of the disc 20, at the periphery 30;
- b) while maintaining each of the damping devices 52 constrained in a state where it is compressed radially to the X axis (radial F stresses inwards, along Z), the damping devices 52 are then inserted into the cells 50, by sliding them there, in the direction L1;
- c) the roots 110 of the blades 90 are then inserted into the said cells 50, so that, in the cells 50, the damping devices 52 are each interposed between a root 110 of the blade and the bottom 70 of the cell which makes it opposite; And
- d) the radial compressive stresses F are then released inwards from the damping devices 52 in place in the cells 50, so that the damping devices 52 then act radially outwards on the roots 110 of the blades which their face, respectively.

It is specified that the preceding paragraph also covers the case where all or part of steps b) to d) would be carried out cell by cell; and therefore that steps b) to d) would be carried out in a single cell and with the blade which is slipped into it, before moving on to another cell and blade with which steps b) would be carried out again together to d), and so on around the circumference of the disk.

To ensure said restraints F of the damping devices 52, it is possible to insert in the direction L1, in the cells 50, tabs 32 (see ) which, by pressing on them, will compress the damping devices 52 radially to the X axis against the cell bottoms 70.

Then, to ensure said release of these radial compressive stresses F, the tabs 32 will be removed from said cells 50, by causing them to slide in the opposite direction, in the direction L1.

To ensure the inward radial compressive stress F, each tongue 32, of suitable width, may bear laterally against the side bearing surfaces 70a of the cells 50, in their respective parts closest to the corresponding bottom 70, where the section (or width) of the cell tapers radially outwards. Between the tongue 32 thus wedged in the cell and the bottom 70 facing this cell, it will be possible to slide, in the direction L1, a damping device 52.

The tab 32 can be removed in the same way, in the opposite direction.

The solution of the invention can be implemented both on a new rotor disc 20 and on an older disc 20, undergoing maintenance or repair, for example in the context of replacing a blade 90 .

Optionally, locks and/or shims, functionally comparable or even identical to locks 15 and/or shims 17, may be used in association with wedges 130.

Tinsels, such as those 17 of the , would then envelop the blade roots 110, possibly with lateral branches 17a of these foils respectively covering the lateral bearing surfaces of the blade roots.

Claims (15)

Turbomachine rotor assembly including:
- a rotor disc (20) adapted to rotate around an axis (X) and having in the radially outer periphery cells (50) each having a bottom (70);
- blades (90) having feet (110) individually arranged in said cells; And
- wedges (130), each wedge (130) being interposed between a root (110) of one of said blades (90) and the bottom (70) of a cell,
characterized in that the wedges (130) incorporate damping devices (52) with a return effect, to push the blade roots (110) radially outwards. An assembly according to claim 1, wherein the damping devices (52) comprise springs (22). Assembly according to Claim 1 or 2, in which, opposite each root (110) of the blade (90), the damping device (52) comprises a foam (24). Assembly according to claim 1 in which, per root (110) of blade (90), the damping device (52) comprises a foam (24) and several springs (22), the foam being interposed between the springs (22) and the root (110) of the blade and/or the bottom (70) of the cell. An assembly according to claim 4 or claims 2 and 3, wherein the foam (24) circumferentially surrounds the springs (22). Assembly according to Claim 5, in which the foam (24) contains cavities (26) in which the springs (22) are arranged. An assembly according to claim 2 or 4, taken individually or in combination with any one of claims 5 or 6, wherein the springs (22) are compression springs oriented to act radially. Assembly according to Claim 2 or 4, taken individually or in combination with any one of Claims 5 to 7, in which, parallel to a direction of elongation of the cell (50) in which it is arranged, the foot ( 110) corresponding blade has a direction of elongation along which the springs (22) are arranged in several lines. Assembly according to any one of Claims 1 to 7, in which, parallel to a direction of elongation of the cell (50) in which it is arranged, the corresponding blade root (110) has a length (L3) and the damping device (52) extends in one piece over more than 75% of the length (L3) of the blade root (110). Assembly according to Claim 3 or 4 taken individually or in combination with any one of Claims 5 to 9, in which the foam (24) has different densities and/or hardnesses and/or thicknesses at different places. Assembly according to Claim 2 or 4, taken individually or in combination with any one of Claims 5 to 10, in which, in the same cell (50), the springs (22) have different stiffnesses between them. An assembly according to Claim 4 or Claims 2 and 3, taken individually or in combination with any one of Claims 5 to 11, in which an adhesion means (28) adheres the foam (24) and the springs (22 ). Aeronautical turbomachine comprising the assembly according to any one of the preceding claims. Method for mounting turbomachine blades (90) on a rotor disk (121) of the turbomachine adapted to rotate around an axis (X) and having in the radially outer periphery cells (50) each having a bottom, the blades (90) having feet (110), in which:
- damping devices (52) with a return effect are produced;
- the damping devices (52) are inserted into the cells (50) and they are held there, each constrained in a state in which it is compressed radially to the axis (X);
- inserting the roots (110) of the blades in said cells, so that the damping devices (52) are interposed between the roots (11) of the blade and the bottoms of said cells (50); And
- the radial compression stresses of the damping devices (52) in the cells (50) are released, so that the damping devices act radially outwards on the roots (110) of the blades. . A method according to claim 14, wherein:
- Said restraints of the damping devices (52) are carried out by inserting into the cells (50) tabs (32) which compress radially to the axis (X) the damping devices (52) against the bottoms of the cells (70 ); Then,
- To ensure said release of these constraints, the tabs (32) are removed from the cells (50), by sliding them.