FR3135110A1 - Aeronautical turbomachine with improved balancing device and process for balancing the turbomachine - Google Patents

Abstract

Aeronautical turbomachine with improved balancing device and method of balancing the turbomachine Aeronautical turbomachine (1) comprising a gas generator having at least one rotor (22, 62) movable in rotation around a central axis (X) and carrying moving blades (24, 64), the turbomachine (1) comprising a balancing device (70) fixed on the rotor (22, 62) and configured to balance the rotor (22, 62) in rotation, the device balancing (70) comprising a plurality of weights (72) distributed circumferentially around the central axis (X), the weights (72) comprising a shape memory alloy. Figure for abstract: Fig. 1.

Description

Aeronautical turbomachine with improved balancing device and process for balancing the turbomachine

The invention relates to the field of aeronautical turbomachines. More specifically, the invention concerns the rotational balancing of turbomachine rotors, and in particular the correction of unbalance in an aircraft turbomachine.

In rotating machines, notably aeronautical turbomachines and in particular in aircraft engines, balancing the rotors is necessary in order to reduce the loads and vibrations transmitted to the structures.

This balancing is planned in advance, during the manufacture and assembly of the rotors. However, the final unbalance after assembly cannot be estimated precisely. Furthermore, it is common for an imbalance to set in after entry into service, particularly following specific events.

However, once the turbomachine is assembled and comes into service, changing the distribution of masses on the rotor requires very substantial maintenance operations. Such operations to correct an unbalance in a difficult-to-access area of the rotor therefore require dismantling of the turbomachine. These maintenance operations can be complex, time-consuming and expensive. There is therefore a need to at least partially overcome the aforementioned drawbacks.

The present presentation relates to an aeronautical turbomachine comprising a gas generator having at least one movable rotor rotating around a central axis and carrying movable blades, the turbomachine comprising a balancing device fixed on the rotor and configured to balance the rotor in rotation, the balancing device comprising a plurality of weights distributed circumferentially around the central axis, the weights comprising a shape memory alloy.

In a known manner, the gas generator can comprise, from upstream to downstream according to the normal direction of flow of the gases in the turbomachine, a low pressure compressor, a high pressure compressor, a combustion chamber, a high pressure turbine and a low pressure turbine. The turbines and compressors extend around the central axis, and each include at least one stator carrying fixed blades, and at least one rotor carrying movable blades and rotating around the central axis.

The balancing device can be fixed on the rotor of the high or low pressure compressor, and/or on the rotor of the high or low pressure turbine. The balancing device makes it possible to balance the rotor during its rotation, by compensating for the existence or appearance of an unbalance on this rotor. The balancing device thus makes it possible to limit the loads and vibrations transmitted to the structures of the turbomachine. Furthermore, reducing rotor vibrations improves the comfort of aircraft passengers and also limits the cyclic stresses on the parts.

To do this, the balancing device comprises a plurality of balancing weights distributed circumferentially, preferably at regular intervals, around the central axis. In addition, the weights are made of a shape memory alloy, preferably metallic. By “shape memory”, we understand an alloy which, after having been deformed from an initial geometry, can regain its initial geometry by application of heat.

Thus, by fixing weights with shape memory on the rotor and having been previously deformed, it is possible, in particular by a simple application of heat, to modify the geometry of these so that they return to their initial geometry. , such a change in geometry leading to a modification of the distribution of their mass. Such an operation can in particular be carried out in a targeted manner on a particular weight, making it possible to compensate for the presence of an unbalance located opposite this weight.

The balancing device thus allows so-called “in-situ” balancing, that is to say it can be carried out on the ground without requiring any dismantling operation. More precisely, apart from simple and unrestrictive operations such as removing a plug, a cover, the nozzle cone, or passing through a boroscopy hole, it is not necessary to dismantle the engine, the wing of the aircraft or dismantling the low pressure turbine. In particular, this device allows balancing without dismantling the turbomachine even in difficult to access areas of the rotor. This makes it possible to simplify maintenance operations, notably by reducing their cost and duration.

In certain embodiments, each of the flyweights is configured to present a deformed geometry when a temperature in the rotor is lower than a predetermined threshold value, and to return to an initial geometry when the temperature is greater than or equal to the predetermined threshold value, a center of gravity of each of the weights in the initial geometry being different from a center of gravity in the deformed geometry.

We understand that the initial geometry is the nominal geometry, or “natural” geometry of the flyweight, in the absence of any deformation thereof. It is also understood that the predetermined threshold value of the temperature is the temperature from which the shape memory flyweight having been deformed, regains its initial geometry, that is to say its nominal geometry. It is understood in this regard that the predetermined threshold value depends on the shape memory material used.

Thus, when the temperature within the rotor is lower than the predetermined threshold value, the shape memory weights remain in their deformed geometry. Conversely, when the temperature at a point of the rotor becomes greater than the predetermined threshold value, the weight(s) adjacent to this point deform to return to their initial geometry, which is distinct from the deformed geometry.

This change in geometry causes a modification in the distribution of the mass of the flyweight(s), and therefore a shift in its center of gravity. Such a shift in the center of gravity thus makes it possible, in a simple manner, to compensate for the presence of an unbalance at a point on the rotor opposite the point at which the deformed flyweight is adjacent.

In certain embodiments, the predetermined threshold value is at least 100°C higher than a nominal operating temperature of the rotor of the turbomachine.

“Nominal operating temperature” means a normal operating temperature of the turbomachine when it is in operation, and when the aircraft comprising the turbomachine is in flight, in the absence of any anomaly within the turbomachine. . It is also understood that this nominal operating temperature depends on the zone considered of the turbomachine.

For example, when the balancing device is placed on the rotor of the low pressure compressor, a nominal operating temperature of the rotor of the low pressure compressor being approximately 200°C, the shape memory alloy chosen for the weights will be such that the predetermined threshold value is greater than 300°C (200°C + 100°C). This value makes it possible to provide a sufficient margin so that, during normal operation of the turbomachine and in the absence of unbalance, the shape memory weights do not deform when this is not desired.

In certain embodiments, the balancing device comprises at least one pair of weights, the two weights of the pair of weights being fixed on the rotor diametrically opposed to each other with respect to the central axis .

The fact of arranging the weights diametrically opposite each other in relation to the central axis ensures that the balancing of the rotor is maintained even in the event of abnormal overheating of the rotor, leading to a modification of the geometry of all the weights.

In certain embodiments, the balancing device comprises between 1 and 80 pairs of weights, preferably at least 30 pairs of weights.

A high number of weights preferably distributed at regular intervals around the central axis makes it possible to improve the efficiency of the device, by allowing balancing whatever the position of the unbalance.

In certain embodiments, the balancing device comprises a support ring fixed on a flange of the rotor, the weights being strips fixed on the support ring.

We understand that the support crown comprises a “classic” metallic material, that is to say a material which does not have shape memory, and which does not deform under the application of heat unlike the weights which she supports. In addition, the fact of fixing the weights, in other words the strips on the crown, then fixing the latter on the rotor, makes it possible to simplify the operation of installing the balancing device in the turbomachine. The strips have the shape of small plates, having a length, a width, and a thickness much less than the length and the width, and which can be fixed to the support crown by screwing, by gluing or by welding.

In some embodiments, each of the strips is configured to move from a retracted position when the temperature in the rotor is below a predetermined threshold value, to an deployed position when the temperature in the rotor is greater than or equal to the threshold value predetermined.

The retracted position may be a position in which the strips are folded upon itself, and the deployed position may be a position in which the strips are unfolded.

In some embodiments, the weights extend in a plane of deformation perpendicular to the central axis and are configured to deform in a radial direction perpendicular to the central axis.

It is understood that the weights, in particular the strips, are included in the deformation plane, and are also deformed in this deformation plane in a radial direction outwards, such that they are in this deformation plane when they are in the deployed position.

Preferably, a main length of the strips extends in a radial direction relative to the central axis, and the strips also deform in the radial direction, in the plane of deformation. In other words, the center of gravity moves in the radial direction, so as to improve the compensation of an existing unbalance.

In some embodiments, the shape memory alloy is one of an alloy comprising nickel, titanium, copper, zinc or aluminum.

In certain embodiments, the turbomachine comprises at least one boroscopy inspection hole, one end of the inspection hole opening opposite the balancing device.

Boroscopy inspection holes are usually present in aeronautical turbomachines, and allow the insertion of a boroscope that can reach difficult-to-access areas. The fact of arranging the balancing device opposite one end of such an inspection hole allows, without the need to dismantle the rotor, the application of heat to the weights in order to cause the deformation of the one or more of them, through this inspection hole.

The present presentation also relates to a method of balancing a rotor of an aeronautical turbomachine according to any of the preceding embodiments, comprising:
- fixing the balancing device on the rotor,
- the detection of an unbalance in the rotor during rotation of the rotor,
- applying heat to the balancing device so as to deform at least one weight comprising a shape memory alloy, so as to compensate for said unbalance.

Fixing the balancing device on the rotor includes fixing each of the weights, in particular the strips, either directly on a flange of the rotor for example, or on a support ring, itself then fixed on the rotor. The rotor can be equipped with at least one sensor allowing the detection of an unbalance generating vibrations of the turbomachine, and the position of this unbalance. From the detection of this unbalance and its position, the application of heat, for example via a boroscopy inspection hole, on one of the memory weights located diametrically opposite to at the position of the unbalance, makes it possible to cause the deformation of this weight returning to its initial geometry, and thus allows the compensation of the unbalance, without requiring the dismantling of the rotor.

In certain embodiments, the method comprises, before fixing the balancing device on the rotor, the deformation of the weights from an initial geometry to a deformed geometry, the weights returning to their initial geometry from a predetermined threshold value of temperature when applying heat to the balancing device.

The initial geometry is the “natural” shape of the weights, in particular the strips, before any deformation of them. These weights are then deformed so as to obtain a deformed geometry compared to their initial geometry. For example, metal strips can be folded in half on themselves. The weights are then fixed on the rotor in this deformed geometry. Given the mechanical properties of shape memory weights, the application of heat allows, from a certain temperature threshold value, to deform the weights again so that they return to their initial geometry. Note that the heating is maintained until the band is completely deployed.

The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended figures, on which:

There is a sectional view of a turbomachine comprising a balancing device according to one embodiment,

There schematically represents different phases of deformation of a shape memory flyweight in a side view,

There is a front view of a shape memory weight used in the balancing device,

There represents the weight of the in an initial geometry (on the left) and in a deformed geometry (on the right),

There is a front plan view of the balancing device used in the turbomachine of the ,

There represents the balancing device of the before application of heat (left) and after application of heat on the shape memory weights (right),

There schematically represents the different stages of a process for balancing a turbomachine rotor.

The terms “upstream” and “downstream” are subsequently defined in relation to the direction of flow of gases through a turbomachine, indicated by the arrow F on the .

There illustrates a double flow turbomachine 1 comprising in a known manner from upstream to downstream successively at least one fan 10, an engine part comprising successively at least one stage of low pressure compressor 20, of high pressure compressor 30, a combustion chamber 40, at least one stage of high pressure turbine 50 and low pressure turbine 60. The high and low pressure turbines and compressors each comprise a rotor rotating around the central axis transmission and gears.

For example, the low pressure turbine 60 includes a stator and a rotor. The rotor 62 carries a plurality of moving blades 64 and rotates around the central axis X. Likewise, the low pressure compressor 20 comprises a stator and rotor. The rotor 22 carries a plurality of moving blades 24 and rotates around the central axis X.

Furthermore, the turbomachine 1 comprises at least one, in this example two, balancing devices 70, one being fixed upstream of the turbomachine 1 on the rotor 22 of the low pressure compressor 20, the other being fixed at downstream of the turbomachine 1 on the rotor 62 of the high pressure turbine 60. Each balancing device 70 comprises a support ring (or disc) 74 fixed on the rotor 22, 62, for example on a free space of 'a flange of the rotor or on a disc carrying the blades 24, 64 of the rotor 22, 62. In addition, each balancing device 70 comprises a plurality of weights (only one of which is visible on the for each balancing device) which are, according to the present embodiment, strips 72.

The strips 72 are distributed circumferentially, preferably at regular intervals, around the central axis X, being fixed on the support crown 74 by screwing, by gluing or by welding. The strips 72 comprise a shape memory metal alloy.

The shape memory materials (known by the acronym “SMA” for “Shape Memory Alloys”) used for the strips 72 can be any alloy that can contain, for example, but not limited to, nickel Ni, titanium Ti , copper Cu, zinc Zn or aluminum Al, and exhibiting two-way shape memory properties with transformation temperatures between 10°C and 1000°C. It is thus possible to place the balancing device 70 in different operating zones of the engine, choosing the material accordingly. For example, a shape memory material comprising an alloy of titanium and nickel can be used, having a density µ = 6.45 g.cm ^-3 . This alloy makes it possible in particular to have activation temperatures, that is to say deformation threshold temperatures greater than 600°C, above the operating temperatures of the low pressure parts of the turbomachine 1.

Conversely, the support ring 74 comprises a so-called “classic” material, which does not have shape memory, for example an alloy of titanium, aluminum or polycrystalline nickel.

There illustrates the mechanical behavior of a shape memory strip 72. The latter presents an initial geometry (image (a)), corresponding to its “natural” shape, in the absence of any application of force. Image (b) represents a situation in which forces F, represented by the arrows in this image, are applied to the strip 72, causing it to deform. After the application of these forces, the strip 72 is thus in a deformed geometry, which it maintains at room temperature (image (c)). Image (d) represents a situation in which a heat source is applied to the strip 72. When the temperature reaches a threshold value, depending on the material used, the strip 72 then deforms to find its initial geometry shown on the image (a).

Each strip 72 has the shape of a flat plate, having a main length L, a width l, and a thickness e which is very small compared to the length L and the width l. On the , the strip has a trapezoidal shape, with a greater width l at one of the two ends of its main length. This shape is not limiting, the strips 72 may have a rectangular shape. Thus, the represents a side view of a strip 72 on its edge, that is to say according to the thickness e, and the represents a strip 72 in a front view, perpendicular to the plane formed by its length L and its width l.

Considering for example a strip 72 comprising an alloy of titanium and nickel, with a width l of 1 cm, a thickness of 0.1 cm e, and a length L of 25 cm, each strip 72 weighs 16.1 g. After heating the strip 72 causing its deformation by shape memory to return to its initial geometry, its center of gravity moves during said deformation. Under these conditions, the movement of the center of gravity allows each strip 72 to provide 400 cm.g of unbalance.

Taking into account these mechanical properties of the shape memory strips 72, a process for balancing the rotor 22, 62 of the aeronautical turbomachine 1 will be described with reference to Figures 4 to 7.

Firstly, each strip 72 is deformed from its initial geometry, towards a deformed geometry (step S100, ). This deformation is obtained by applying a force F to one end of the strip 72, so as to reduce its main length L, for example by folding it back on itself, by crushing it like an accordion, or any other deformation involving a reduction in the main length L and a movement of the center of gravity of the strip 72 in the direction of the main length L.

Then, each of the strips 72, in its deformed geometry, is fixed on the support ring 74, and the support ring 74 is fixed on the rotor 22, 62 (step S200). There represents a front view of the balancing device 70 alone, without representing the rotor 22, 62. It will be noted that the strips 72 are fixed on the support ring 74 so that the main length L, the dimension of which is reduced in the deformed geometry, extends in the radial direction of the support ring 74, that is to say perpendicular to the central axis X when the support ring 74 is fixed on the rotor.

The balancing device 70 is fixed on the rotor 22, 62 of material such that the support ring 74 is concentric with the central axis X. In this example, the balancing device 70 comprises eight strips 72, i.e. four pairs of strips 72, it being understood that the two strips 72 of each pair of strips 72 are arranged diametrically opposite each other with respect to the central axis not limiting, and is given by way of illustration in order to simplify the description of the device, it being understood that the latter preferably comprises at least thirty pairs of strips 72.

During the operation of the turbomachine 1, the rotors 22, 62 being in rotation, detection, possibly continuously, of the presence of an unbalance is carried out (step S300). This detection can be carried out by sensors placed in the rotors 22, 62 connected to a control unit, making it possible to detect the presence of a vibration caused by an unbalance, and to locate this unbalance. In particular, the vibration “monitoring” sensors usually installed in aeronautical turbomachines are capable of detecting unbalances synchronous to the engine rotation speed and determining the angular phase of appearance of these unbalances.

When an unbalance in an angular sector is detected and located, the turbomachine 1 is stopped so as to apply a heat source to the balancing device 70 on one or more strips 72 opposite this unbalance, so as to deform the strip(s) 72 (step S400, ). More precisely, the strips 72 return, under the effect of heat, to their initial geometry by moving their center of gravity radially outwards, in a direction R perpendicular to the central axis X, so as to compensate for the unbalance. On the example of the , a strip 72 is fully deployed, the two strips 72 adjacent to it are being deployed, the heating being maintained until the strips 72 are completely deployed.

It will be noted that the strips 72 extend in a plane P perpendicular to the central axis

To carry out this heating, the balancing devices 70 are initially arranged opposite a first end 81 of boroscopy inspection holes 80, already present in the turbomachine 1. A boroscope equipped with a conductive tip electricity can be inserted into the inspection hole 80 via a second end 82 until the tip comes into contact for example with the base of the strip 72 to be deployed, the rotor having previously been oriented so place the base of said strip 72 opposite the first end 81 of the inspection hole 80. The electric current thus passes through the strip 72 allowing it to be heated by the Joule effect. It is also preferable that the strips are electrically isolated from each other.

It will be noted that this configuration is not limiting, the balancing devices 70 being able to be arranged in positions not accessible through the boroscopy inspection holes 80. Thus, alternatively, access from the inside of the rotor shaft is also possible. To do this, a heating tool can access the strip 72 to be heated via the rotor shaft, and heat this strip 72 by electrical contact with it in the same way as described previously, or by induction, the tool introduced inside the shaft can be equipped with an inductive system concentrated on an angular sector heating and deploying the strip(s) 72.

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 different illustrated/mentioned embodiments can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

It is also obvious that all the characteristics described with reference to a process can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a process.

Claims (11)

Aeronautical turbomachine (1) comprising a gas generator having at least one rotor (22, 62) movable in rotation around a central axis (X) and carrying movable blades (24, 64), the turbomachine (1) comprising a balancing device (70) fixed on the rotor (22, 62) and configured to balance the rotor (22, 62) in rotation, the balancing device (70) comprising a plurality of weights (72) distributed circumferentially around the central axis (X), the weights (72) comprising a shape memory alloy. Turbomachine (1) according to claim 1, in which each of the weights (72) is configured to present a deformed geometry when a temperature in the rotor (22, 62) is lower than a predetermined threshold value, and to find an initial geometry when the temperature is greater than or equal to the predetermined threshold value, a center of gravity of each of the weights (72) in the initial geometry being different from a center of gravity in the deformed geometry. Turbomachine (1) according to claim 2, in which the predetermined threshold value is at least 100°C higher than a nominal operating temperature of the rotor (22, 62) of the turbomachine (1). Turbomachine (1) according to any one of claims 1 to 3, in which the balancing device (70) comprises at least one pair of weights (70), the two weights (72) of the pair of weights (72) being fixed on the rotor (22, 62) diametrically opposite each other with respect to the central axis (X). Turbomachine (1) according to claim 4, in which the balancing device (70) comprises between 1 and 80 pairs of weights (72), preferably at least 30 pairs of weights (72). Turbomachine (1) according to any one of claims 1 to 5, in which the balancing device (70) comprises a support ring (74) fixed on a flange of the rotor (22, 62), the weights (72) being strips fixed on the support crown (74). Turbomachine (1) according to any one of claims 1 to 6, in which the weights (72) extend in a deformation plane (P) perpendicular to the central axis (X) and are configured to deform in a radial direction (R) perpendicular to the central axis (X). Turbomachine (1) according to any one of claims 1 to 7, in which the shape memory alloy is one of an alloy comprising nickel, titanium, copper, zinc or aluminum. Turbomachine (1) according to any one of claims 1 to 8, comprising at least one inspection hole (80) by boroscopy, one end (81) of the inspection hole (80) opening facing the balancing device (70). Method for balancing a rotor (22, 62) of an aeronautical turbomachine (1) according to any one of the preceding claims, comprising:
- fixing the balancing device (70) on the rotor (22, 62),
- the detection of an unbalance in the rotor (22, 62) during the rotation of the rotor (22, 62),
- applying heat to the balancing device (70) so as to deform at least one weight (72) comprising a shape memory alloy, so as to compensate for said unbalance. Method according to claim 10 comprising, before fixing the balancing device (70) on the rotor (22, 62), the deformation of the weights (72) from an initial geometry towards a deformed geometry, the weights (72) regaining their initial geometry from a predetermined threshold temperature value when applying heat to the balancing device (70).