EP3976928B1 - Assembly for turbomachine and turbomachine - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to an assembly for a turbomachine and a turbomachine.

The invention relates more specifically to an assembly for a turbomachine comprising a damper.

STATE OF THE ART

A turbomachine known from the state of the art comprises a casing and a fan capable of being rotated relative to the casing, around a longitudinal axis, thanks to a fan shaft.

The fan comprises a disc centered on the longitudinal axis, and a plurality of vanes distributed circumferentially at the level of the external part of the disc.

The operating range of the blower is limited. More precisely, the evolution of a compression ratio of the fan as a function of a flow of air that it sucks in when it is put into rotation, is restricted to a predetermined range.

Beyond this range, the fan is in fact subject to aeroelastic phenomena which destabilize it. More specifically, the air circulating through the fan in operation brings energy to the blades, and the blades respond in their own modes to levels that may exceed the endurance limit of the material from which they are made. This fluid-structure coupling therefore generates vibratory instabilities which accelerate the wear of the fan, and reduce its service life.

A fan which comprises a reduced number of blades, and which is subjected to high aerodynamic loads, is very sensitive to this type of phenomenon.

This is the reason why it is necessary to guarantee a sufficient margin between the stable operating range and the areas of instability, so as to accommodate the endurance limits of the fan.

To do this, it is known to provide the fan with dampers. Examples of shock absorbers were described in the documents FR 2 949 142 , EP 1 985 810 And FR 2 923 557 , on behalf of the Claimant. These dampers are all configured to be housed between the platform and the root of each blade, within the housing delimited by the respective stilts of two successive blades. Furthermore, such dampers operate during relative movement between two successive blade platforms, by dissipation of vibration energy, for example by friction. Therefore, these dampers only aim to damp a first vibratory mode of the blades which characterizes a synchronous response of the blades to aerodynamic stresses. In this first vibratory mode, the inter-blade phase shift is non-zero. Other shock absorbers have been described in the document WO 2016/059348 .

However, such dampers are totally ineffective for damping a second vibratory mode in which each blade beats relative to the disc with zero inter-blade phase shift. Indeed, in this second vibratory mode, there is no relative displacement between two successive blade platforms. This particular response of the blades to aerodynamic stresses, although asynchronous, nevertheless implies a non-zero moment on the fan shaft. Furthermore, this second vibratory mode is coupled between the blades, the disc, and the fan shaft. The amplitude of this second vibratory mode is all the greater as the blades are large.

There is therefore a need to overcome at least one of the disadvantages of the prior art described above.

DISCLOSURE OF THE INVENTION

An object of the invention is to damp a mode of vibration of a rotor in which the phase difference between the blades of said rotor is zero.

Another object of the invention is to influence the damping of vibration modes of a rotor in which the phase difference between the blades of said rotor is non-zero.

Another object of the invention is to provide a damping solution that is simple and easy to implement.

To this end, according to a first aspect of the invention, there is proposed an assembly for a turbomachine as indicated in claim 1.

It is by damping a displacement of the first rotor relative to the second rotor, in a plane orthogonal to the longitudinal axis, that it is possible to influence the second vibratory mode. In fact, unlike the first vibratory mode, the second vibratory mode is characterized by a zero inter-blade phase shift. Consequently, placing a damper between two successive blades of a rotor, as has already been proposed in the prior art, produces no effect on the second vibratory mode. The damper of the previously described assembly has, for its part, the advantage of influencing the second vibratory mode because it plays on an effect of the second vibratory mode: the displacement of the first rotor relative to the second rotor, in the plane orthogonal to the longitudinal axis. By opposing this effect, the damper disrupts the cause, ie dampens the second vibrational mode. It should nevertheless be noted that the first vibratory mode also contributes to the displacement of the first rotor relative to the second rotor, in the plane orthogonal to the longitudinal axis. Therefore, by opposing this effect, the damper also participates in disturbing another cause, i.e. damping the first mode vibratory. In addition, the damper being annular, it makes it possible to distribute the support stresses applied by the damper on the first rotor and on the second rotor, over a larger surface. From there, the damper wears less the first rotor and the second rotor on which it bears. Finally, the third part being thicker than the first part and the second part, it is more massive. The third part therefore makes it possible to limit the tangential propagation of the vibrational modes to which the first rotor and the second rotor are subjected. Thus, the shock absorber is capable, thanks to this third part, of dissipating the vibrations by its work in bending and inertia.

• dans un tel ensemble :
  • ∘ la première partie est configurée pour appliquer un premier effort centrifuge sur le premier rotor, et
  • ∘ la deuxième partie est configurée pour appliquer un deuxième effort centrifuge sur le deuxième rotor,
• la troisième épaisseur radiale est supérieure à chacune parmi la première épaisseur radiale et à la deuxième épaisseur radiale,
• la deuxième épaisseur radiale est supérieure à la première épaisseur radiale,
• le renflement comprend une première lèvre faisant radialement saillie vers l'intérieur de l'amortisseur,
• le renflement comprend une deuxième lèvre faisant radialement saillie vers l'extérieur de l'amortisseur,
• la troisième partie comprend une dépression,
• chacune des aubes parmi la pluralité d'aubes comprend :
  • ∘ un pied d'aube reliant l'aube au disque,
  • ∘ un aubage profilé,
  • ∘ une échasse reliant l'aubage au pied d'aube, et
  • ∘ une plateforme reliant l'aubage à l'échasse et s'étendant transversalement à l'échasse, la première partie d'appui venant en appui sur chacune des plateformes des aubes parmi la pluralité d'aubes,
• le deuxième rotor comprend une virole, la virole comprenant une extension circonférentielle, la deuxième partie d'appui venant en appui sur l'extension circonférentielle, et
• l'amortisseur est annulaire, et s'étend tout autour de l'axe longitudinal.

Advantageously, but optionally, the assembly according to the invention may further comprise one of the following characteristics, taken alone or in combination with one or more of the other of the following characteristics:

• in such a set:
  • ∘ the first part is configured to apply a first centrifugal force on the first rotor, and
  • ∘ the second part is configured to apply a second centrifugal force on the second rotor,
• the third radial thickness is greater than each of the first radial thickness and the second radial thickness,
• the second radial thickness is greater than the first radial thickness,
• the bulge comprises a first lip projecting radially towards the inside of the damper,
• the bulge comprises a second lip projecting radially outward from the damper,
• the third part includes a depression,
• each of the vanes among the plurality of vanes comprises:
  • ∘ a blade foot connecting the blade to the disc,
  • ∘ profiled blading,
  • ∘ a stilt connecting the blading to the blade foot, and
  • ∘ a platform connecting the blading to the stilt and extending transversely to the stilt, the first support part coming to bear on each of the platforms of the blades among the plurality of blades,
• the second rotor comprises a shroud, the shroud comprising a circumferential extension, the second support part coming to bear on the circumferential extension, and
• the damper is annular, and extends all around the longitudinal axis.

According to a second aspect of the invention, there is proposed a turbomachine as indicated in claim 11, comprising an assembly as previously described, and in which the first rotor is a fan, and the second rotor is a low-pressure compressor.

DESCRIPTION OF FIGURES

• La figure 1 illustre de façon schématique une turbomachine,
• La figure 2 comprend une vue en coupe d'une partie d'une turbomachine, et une courbe indiquant un déplacement tangentiel de différents éléments de cette partie de turbomachine en fonction de la position desdits éléments le long d'un axe longitudinal de la turbomachine,
• La figure 3 est une vue en coupe d'une partie d'un exemple de réalisation d'un ensemble selon l'invention,
• La figure 4 est une vue en perspective d'une partie d'un exemple de réalisation d'un ensemble selon l'invention, et
• La figure 5 est une vue en perspective d'une partie d'un amortisseur d'un exemple de réalisation d'un ensemble selon l'invention.

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended drawings in which:

• There figure 1 schematically illustrates a turbomachine,
• There figure 2 comprises a sectional view of a part of a turbomachine, and a curve indicating a tangential displacement of various elements of this part of the turbomachine as a function of the position of said elements along a longitudinal axis of the turbomachine,
• There picture 3 is a sectional view of part of an embodiment of an assembly according to the invention,
• There figure 4 is a perspective view of part of an exemplary embodiment of an assembly according to the invention, and
• There figure 5 is a perspective view of part of a damper of an embodiment of an assembly according to the invention.

In all the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION Turbomachine 1

With reference to the figure 1 , a turbomachine 1 comprises a casing 10, a fan 12, a low pressure compressor 140, a high pressure compressor 142, a combustion chamber 16, a high pressure turbine 180 and a low pressure turbine 182.

Each of the fan 12, the low pressure compressor 140, the high pressure compressor 142, the high pressure turbine 180, and the low pressure turbine 182, is rotatable relative to the casing 10 around a longitudinal axis X-X.

In the embodiment illustrated in figure 1 , and as also visible on the figure 2 And 3 , the fan 12 and the low pressure compressor 140 are integral in rotation, and are capable of being rotated by a low pressure shaft 13 which is itself capable of being rotated by the low pressure turbine 182. The high pressure compressor 142 is, for its part, capable of being rotated by a high pressure shaft 15, which is itself capable of being rotated by the high pressure turbine 180.

In operation, the fan 12 draws in a flow of air 110 which separates between a secondary flow 112, circulating around the casing 10, and a primary flow 111, successively compressed within the low pressure compressor 140 and the high pressure compressor 142, ignited within the combustion chamber 16, then successively expanded within the high pressure turbine 180 and the low pressure turbine 182.

Upstream and downstream are defined here with respect to the direction of normal air flow 110, 111, 112 through the turbine engine 1. Similarly, an axial direction corresponds to the direction of the longitudinal axis X-X, an radial direction is a direction which is perpendicular to this longitudinal axis X-X and which passes through said longitudinal axis X-X, and a circumferential, or tangential, direction corresponds to the direction of a flat and closed curved line, all the points of which lie at equal distance from the longitudinal axis X-X. Finally, and unless otherwise specified, the terms "internal (or interior)" and "external (or exterior)", respectively, are used in reference to a radial direction so that the internal (i.e. radially internal) part or face d an element is closer to the longitudinal axis X-X than the external (i.e. radially external) part or face of the same element.

Blower 12 and low pressure compressor 140

• un pied d'aube 1220 reliant l'aube 122 au disque 120,
• un aubage profilé 1222,
• une échasse 1224 reliant l'aubage 1222 au pied d'aube 1220, et
• une plateforme 1226 reliant l'aubage 1222 à l'échasse 1224, et s'étendant transversalement à l'échasse 1224.

With reference to figures 1 to 3 , the fan 12 comprises a disk 120 and a plurality of vanes 122 distributed circumferentially at the level of an outer part of the disk 120. With reference to the figure 2 And 3 , each of the vanes 122 of the plurality of vanes 122 comprises:

• a blade root 1220 connecting the blade 122 to the disc 120,
• a profiled blading 1222,
• a stilt 1224 connecting the blade 1222 to the blade root 1220, and
• a platform 1226 connecting the blading 1222 to the stilt 1224, and extending transversely to the stilt 1224.

The blade root 1220 can be integral with the disc 120 when the fan 12 is a one-piece bladed disc. Alternatively, as shown in picture 3 , the blade root 1220 can be configured to be housed in a cell 1200 of the disc 120 provided for this purpose.

As seen on the figure 2 And 3 , the low-pressure compressor 140 also comprises a plurality of vanes 1400 fixedly mounted at an outer part of a shroud 1402, said shroud 1402 comprising a circumferential extension 1404 at the outer end of which radial sealing wipers 1406 extend. The radial sealing wipers 1406 come opposite the platforms 1226 of the blades 122 of the fan 12, so as to guarantee the internal sealing of the flow stream within which the primary flow 111 circulates. picture 3 , the shroud 1402 of the low pressure compressor 140 is fixed to the disc 120 of the fan 12, for example by bolting.

Each of the blades 122 of the plurality of blades 122 of the fan 12 is capable of beating, by vibrating with respect to the disc 120 during a rotation of the fan 12 with respect to the casing 10. More precisely, during the coupling between the air 110 circulating within the fan 12 and the profiled blades 1222, the blades 122 are the seat of aeroelastic phenomena of flutter on different vibratory modes, and whose amplitude can be such that it exceeds the endurance limits of the materials constituting the fan 12. These vibratory modes are furthermore coupled to the opposing forces of compression upstream of the turbine engine 1, and of expansion downstream of the latter.

A first vibratory mode characterizes a synchronous response of the blades 122 to aerodynamic stresses, in which the inter-blade phase shift is non-zero.

A second vibratory mode characterizes an asynchronous response of the blades 122 to aerodynamic stresses, in which the inter-blade phase shift is zero. The amplitude of the beats of the second vibratory mode is also greater than the blades 122 of fan 12 are large. Furthermore, this second vibratory mode is coupled between the blades 122, the disk 120, and the fan shaft 13. The frequency of the second vibratory mode is, moreover, one and a half times greater than that of the first vibratory mode. Finally, the second vibratory mode has a nodal deformation at mid-height of the blades 122 of the fan 12.

In vibratory modes, including the second vibratory mode, the beating of the blades 122 implies a non-zero moment on the low pressure shaft 13. In particular, these vibratory modes lead to intense torsional forces within the low pressure shaft 13. The vibrations induced by the beating of the blades 122 of the fan 12, but also by the beating of the blades 1400 of the low pressure compressor 140, lead to significant relative tangential displacements between the fan 12 and the low pressure compressor 140. Indeed, the length of the blades 122 of the fan 12 is greater than the length of the blades 1400 of the low pressure compressor 140. Consequently, the tangential bending moment caused by the beats of a blade 122 of the fan 12 is greater than the tangential bending moment driven by beats of a blade 1400 of the low pressure compressor 140. The blades of the blades 122 of the fan 12 and of the blades 1400 of the low pressure compressor 140 then have very different behaviors. Furthermore, the mounting stiffness within the fan 12 is different from the mounting stiffness within the low pressure compressor 140.

As visible more precisely on the figure 2 , this results in particular in a large-amplitude displacement of the fan 12 relative to the low-pressure compressor 140, in a plane orthogonal to the longitudinal axis XX, at the interface between the platforms 1226 of the blades 122 of the fan 12 and the radial sealing wipers 1406 of the circumferential extension 1404 of the shroud 1402 of the low pressure compressor 140. The amplitude of this displacement for the second vibratory mode is for example between 0.01 and 0.09 millimeters, typically 1 'order of 0.06 millimeters, or, in another example, is of the order of a few tenths of a millimeter, for example 0.1 or 0.2 or 0.3 millimeters.

Shock absorber 2

A damper 2 is used in order to dampen these vibrations of the fan 12 and/or of the low pressure compressor 140.

The damper 2 is in particular configured to damp a displacement of the fan 12 relative to the low pressure compressor 140, in a plane orthogonal to the longitudinal axis X-X, the displacement being caused by a beat of at least one blade 122 among the plurality of blades 122 of the fan 12.

• une première partie 21 venant en appui sur la soufflante 12,
• une deuxième partie 22 venant en appui sur le compresseur basse pression 140, et
• une troisième partie 23 reliant la première partie 21 à la deuxième partie 22.

With reference to figures 3 to 5 , damper 2 includes:

• a first part 21 bearing on the fan 12,
• a second part 22 bearing on the low pressure compressor 140, and
• a third part 23 connecting the first part 21 to the second part 22.

As particularly visible on the figure 5 , the damper 2 is annular, and therefore extends all around the longitudinal axis XX. More precisely, the first part 21 has a first radially internal surface 211 extending all around the longitudinal axis XX, and a first radially outer surface 212 extending all around the first radially inner surface 211. In addition, the second part 22 has a second radially inner surface 221 extending all around the longitudinal axis XX, and a second radially external surface 222 extending all around the second radially internal surface 221. Finally, the third part 23 has a third radially internal surface 2310 extending all around the longitudinal axis XX, and a third radially external surface 2320 extending all around the third radially inner surface 2310.

Furthermore, as seen in the figure 4 , the first part 21 has a first radial thickness E1 measured perpendicular to the longitudinal axis XX between the first radially inner surface 211 and the first radially outer surface 212. Similarly, the second part 22 has a second radial thickness E2 measured perpendicular to the longitudinal axis XX between the second radially internal surface 221 and the second radially external surface 222. Finally, the third part 23 has a third radial thickness E3 measured perpendicularly to the longitudinal axis XX between the third radially internal surface 2310 and the third radially outer surface 2320.

The third radial thickness E3 is greater than at least one of the first radial thickness E1 and the second radial thickness E2. In one embodiment, for example illustrated in figure 4 , the third radial thickness E3 is greater than each of the first radial thickness E1 and the second radial thickness E2. In this way, the third part 23 is more massive than the first part 21 and than the second part 22. In an equally advantageous variant, the second radial thickness E2 is greater than the first radial thickness E1, so as to promote the support of the second part 22 on the low pressure compressor 140.

In an advantageous embodiment, the first part 21 bears against each of the platforms 1226 of the blades 122 of the fan 12, preferably at the level of an internal surface of each of the platforms 1226. An annular damper 2 is moreover particularly adapted for a fan 12 comprising a disk 120 which is bladed in one piece. Indeed, in a fan 12 where the blades 122 are attached to the disk 120, if the damper 2 is annular, then the support of the first part 21 on the different platforms 1226 of the blades 122 is not uniform. This induces inhomogeneous damping around the longitudinal axis XX and, from there, risks of wear of the platforms 1226 and of the damper 2. The internal surfaces of the platforms 1226 can comprise reliefs so as to be axisymmetric. This circumferential non-symmetry of the interior side of the platforms 1226 can thus optimize the mutual bearings of the shock absorber 2, in particular their distributions, while privileging, where appropriate, bearing wear on these reliefs.

In addition, the second part 22 bears against the circumferential extension 1404 of the ferrule 1402 of the low pressure compressor 140, at the level of an internal surface of the radial sealing wipers 1406. Indeed, it is at this position that the displacement of the fan 12 relative to the low pressure compressor 140, in the plane orthogonal to the longitudinal axis X-X, is of greater amplitude, typically a few millimeters. Consequently, the damper 2 is particularly effective there.

In one embodiment, the damper 2 comprises a material from the range having the trade name “SMACTANE ^® ST” and/or “SMACTANE ^® SP”, for example a material of the “SMACTANE ^® ST 70” type and/or “ ^SMACTANE® SP 50”. It has in fact been observed that such materials have appropriate damping properties.

With reference to the picture 3 , in one embodiment, the first part 21 is configured to apply a first centrifugal force C1 to the fan 12, while the second part 22 is configured to apply a second centrifugal force C2 to the low pressure compressor 140. To apply the first centrifugal force C1, the first bearing part 21 has a radially outer surface coming into contact with a radially inner surface of the fan 12, typically a radially inner surface of the platform 1226. To apply the second centrifugal force C2, the second bearing part 22 has a radially outer surface coming into contact with a radially inner surface of the low pressure compressor 140, typically a radially inner surface of the circumferential extension 1404, for example a radially inner surface of the sealing wipers 1406. In this way, these parts 21, 22 are each dynamically coupled respectively to the fan 12 and to the low pressure compressor 140 on which each bears, so as to undergo the same vibrations as each of the fan 12 and of the low pressure compressor 140.

The third part 23 is steeper, in particular in a tangential direction. Thus, in operation, a displacement of the fan 12 relative to the low pressure compressor 140, in a plane orthogonal to the longitudinal axis XX, causes tangential shearing of the damper 2 which causes circumferential displacements of said damper 2. The supports respectively on the fan 12 and the low pressure compressor 140 are therefore broken, then quickly resumed to apply the centrifugal forces C1, C2 again. These ruptures and resumptions of the supports allow damping. Advantageously, the tangential displacements of the high-frequency fan 12 are damped when the parts 21, 22 bear against the fan 12 and the low-pressure compressor 140. The rupture of the supports, then the circumferential sliding, makes it possible to dampen frequencies weaker. In this way, the damper 2 is effective over a wide range of frequencies. With reference to the figure 4 , according to the invention, the third part 23 comprises a bulge 231, 232, preferably annular. Advantageously, the bulge 231, 232 comprises a first lip 231, also annular, and projecting radially towards the inside of the damper 2. The first lip 231 is intended to make the third part 23 heavier, which advantageously increases its tangential inertia. Alternatively, or in addition as illustrated in the figure 4 , the bulge 231, 232 comprises a second lip 232, also annular, and projecting radially outwards from the damper 2. In addition to its function of weighting down the third part 23 which advantageously leads to an increase in the tangential rigidity, the second lip also ensures the axial setting of the damper 2 between the fan 12 and the low pressure compressor 140.

• la troisième partie 23 présente une première surface d'appui 2321 agencée pour appliquer un premier effort F1 sur le compresseur basse pression 140, le premier effort F1 ayant une première composante longitudinale F1L dans une première direction parallèle à l'axe longitudinal X-X, et une première composante radiale F1R dans une deuxième direction orthogonale à l'axe longitudinal X-X, la première composante longitudinale F1L étant supérieure à la première composante radiale F1R,
• la deuxième partie 22 présente une deuxième surface d'appui 2200 agencée pour appliquer un deuxième effort F2 sur le compresseur base pression 140, le deuxième effort F2 ayant une deuxième composante longitudinale F2L dans la première direction, et une deuxième composante radiale F2R dans la deuxième direction, la deuxième composante radiale F2R étant supérieure à la deuxième composante longitudinale F2L.

With reference to the figure 4 , in one embodiment:

• the third part 23 has a first support surface 2321 arranged to apply a first force F1 to the low pressure compressor 140, the first force F1 having a first longitudinal component F1L in a first direction parallel to the longitudinal axis XX, and a first radial component F1R in a second direction orthogonal to the longitudinal axis XX, the first longitudinal component F1L being greater than the first radial component F1R,
• the second part 22 has a second bearing surface 2200 arranged to apply a second force F2 on the low-pressure compressor 140, the second force F2 having a second longitudinal component F2L in the first direction, and a second radial component F2R in the second direction, the second radial component F2R being greater than the second longitudinal component F2L.

In other words, the third part 23 provides axially positioned support for the damper 2, via the first support surface 2321, since it is a downstream axial surface of the damper 2 coming into contact with an upstream axial surface of the low-pressure compressor 140. Furthermore, the second part 22 provides radially positioned support for the damper 2, via the second support surface 2200, since it is a radially outer surface of the damper 2 coming into contact with a radially inner surface of the low pressure compressor 140. In addition, in operation, the second bearing surface 2200 contributes to the application of the second centrifugal force C2 on the low pressure compressor 140. Advantageously, it is the second lip 232 of the third part 23 which presents the first bearing surface 2321, as visible on the figure 4 .

With reference to figure 4 And 5 , in one embodiment, the third part 23 comprises a depression 233, preferably annular. The depression 233 can be made at the level of an external surface 2320 or of an internal surface 2310 of the third part 23, upstream or downstream of the bulge 231, 232. In the embodiment illustrated in the figure 5 , the depression 233 extends upstream of the bulge. When the depression 233 extends downstream of the bulge 231, 232, as illustrated in the figure 4 , at an outer surface 2320 of the third part 23, it provides clearance which allows the damper 2 to avoid rubbing on a corner of the radial sealing wipers 1406. In any event, the depression 233 promotes the axial setting of the damper 2 between the fan 12 and the low pressure compressor 140, but also the sealing of the flow path of the flow of primary air 111. Indeed, under the effect of the first effort centrifugal C1, the first part 21 can thus be compressed downstream.

In one embodiment, at least one of the first part 21, the second part 22 and the third part 23 comprises an additional coating, configured to reduce the friction and/or the wear of the fan and/or the compressor. low pressure 140. This additional coating is mounted fixed on an outer surface of the damper 2, for example by gluing. The additional coating is of the dissipative and/or viscoelastic and/or damping type. It may in fact comprise a material from the range having the trade name “SMACTANE ^® ST” and/or “SMACTANE ^® SP”, for example a material of the “SMACTANE ^® ST 70” and/or “SMACTANE ^® SP 50” type. . It can also comprise a material chosen from among those having mechanical properties similar to those of vespel, Teflon or any other material with lubricating properties. More generally, the additional coating material advantageously has a friction coefficient of between 0.3 and 0.07. The coating makes it possible in particular to increase the tangential stiffness of the damper 2 when, in operation, it applies the centrifugal forces C1, C2 so that the movement of the fan 12 relative to the low pressure compressor 140, in the plane orthogonal to the longitudinal axis XX, or damped by energy dissipation by means of viscoelastic shearing of its coating. In one embodiment, at least one of the first part 21, the second part 22 and the third part 23 is treated by dry lubrication, with a view to perpetuating the value of the coefficient of friction between the damper 2 and the one and/or the other of the fan 12 and of the low-pressure compressor 140. This material with lubricating properties is for example of the MoS2 type.

In all that has been described above, the damper 2 is configured to damp a displacement of the fan 12 relative to the low pressure compressor 140, in the plane orthogonal to the longitudinal axis X-X.

This is however not limiting, since the damper 2 is also configured to damp a displacement of any first rotor 12 relative to any second rotor 140, in a plane orthogonal to the longitudinal axis XX, as long as the first rotor 12 is rotatable relative to the casing 10 around the longitudinal axis XX and comprises a disc 120 as well as a plurality of blades 122 capable of beating while vibrating relative to disc 120 during rotation of first rotor 12 relative to housing 10, and that second rotor 140 is also rotatable relative to housing 10 around longitudinal axis XX.

Thus, the first rotor 12 can be a first stage of the high pressure compressor 142 or low pressure compressor 140, and the second rotor 140 be a second stage of said compressor 140, 142, successive to the first compressor stage 140, 142, upstream or downstream from it. Alternatively, the first rotor 12 can be a first stage of a high pressure turbine 180 or a low pressure turbine 182, and the second rotor 140 can be a second stage of said turbine 180, 182, successive to the first turbine stage 180, 182, in upstream or downstream of it.

In any event, the damper 2 has a restricted size. Therefore, it can easily be integrated into existing turbomachinery.

• soit par frottement et/ou oscillations entre un état où l'amortisseur 2 est collé sur les rotors 12, 140 et un état où l'amortisseur 2 glisse sur les rotors 12, 140, ce qui permet d'amortir notamment les basses fréquences,
• soit par cisaillement viscoélastique au sein de l'amortisseur 2, ce qui permet d'amortir notamment les hautes fréquences.

Moreover, by being configured to exert centrifugal forces C1, C2 on the first rotor 12 and on the second rotor 140, the damper 2 ensures a high tangential stiffness between the first rotor 12 and the second rotor 140. It thus stands out an overly flexible damper which would only become deformed when the first rotor 12 moves relative to the second rotor 140, in the plane orthogonal to the longitudinal axis XX. On the contrary, damper 2 dissipates such a displacement:

• either by friction and/or oscillations between a state where the damper 2 is stuck on the rotors 12, 140 and a state where the damper 2 slides on the rotors 12, 140, which makes it possible to dampen in particular the low frequencies,
• or by viscoelastic shear within the damper 2, which in particular makes it possible to damp the high frequencies.

However, the damper 2 remains flexible enough to maximize the contact surfaces between said damper 2 and the rotors 12, 140 on which it bears. To do this, the damper 2 has a greater tangential stiffness than an axial stiffness and a radial stiffness.

The contact forces between the damper 2 and the rotors 12, 140 can in particular be adjusted by means of additional coatings. At low frequencies, it is indeed necessary to ensure that the centrifugal forces C1, C2 exerted by the damper 2 on the rotors 12, 140 are not too great, in order to guarantee that the damper 2 can oscillate between a bonded state and a slippery state on the rotors 12, 140, and thus dampen by friction. At high frequencies, on the other hand, it is necessary to ensure that the centrifugal forces C1, C2 exerted by the damper 2 on the rotors 12, 140 are sufficiently great for the preload of the damper 2 on the rotors 12, 140 is sufficient to ensure that the damper 2 can be the viscoelastic shear seat.

The wear of the rotors 12, 140 is in particular limited by treatment of the surfaces of the damper 2 resting on the rotors 12, 140, for example to provide them with a coating with a low coefficient of friction.

Claims (11)

1. An assembly for a turbomachine (1) comprising:

   - a casing (10),

   - a first rotor (12) :

   ∘ movable in rotation relative to the casing (10) around a longitudinal axis (X-X), and

   ∘ comprising:

   * a disk (120), and

   * a plurality of blades (122) capable of flapping relative to the disk (120) during a rotation of the first rotor (12) relative to the casing (10),

   - a second rotor (140) movable in rotation relative to the casing (10) around the longitudinal axis (X-X), and

   - a damper (2) configured to damp a movement of the first rotor (12) relative to the second rotor (140), in a plane orthogonal to the longitudinal axis (X-X), the movement being caused by a flapping of at least one blade (122) among the plurality of blades (122), the damper (2) comprising:

   ∘ a first part (21) bearing on the first rotor (12), and having:

   * a first radially inner surface (211) extending all around the longitudinal axis (X-X),

   * a first radially outer surface (212) extending all around the first radially inner surface (211),

   * a first radial thickness (E1) measured perpendicular to the longitudinal axis (X-X) between the first radially inner surface (211) and the first radially outer surface (212), and

   * the radially outer surface coming into contact with a radially inner surface of the first rotor (12),

   ∘ a second part (22) bearing on the second rotor (140), and having:

   * a second radially inner surface (221) extending all around the longitudinal axis (X-X),

   * a second radially outer surface (222) extending all around the second radially inner surface (221), and

   * a second radial thickness (E2) measured perpendicular to the longitudinal axis (X-X) between the second radially inner surface (221) and the second radially outer surface (222), and

   * the radially outer surface coming into contact with a radially inner surface of the second rotor (140), and

   ∘ a third part (23) connecting the first part (21) to the second part (22), and having:

   * a third radially inner surface (231) extending all around the longitudinal axis (X-X),

   * a third radially outer surface (232) extending all around the third radially inner surface (231), and

   * a third radial thickness (E3) measured perpendicular to the longitudinal axis (X-X) between the third radially inner surface (231) and the third radially outer surface (232),

   characterized in that the third radial thickness (E3) is greater than at least one among the first radial thickness (E1) and the second radial thickness (E2) and the third part (23) comprises a bulge (231, 232).
2. The assembly according to claim 1, wherein:

   - the first part (21) is configured to apply a first centrifugal force (C1) on the first rotor (12), and

   - the second part (22) is configured to apply a second centrifugal force (C2) on the second rotor (140).
3. The assembly according to any of claims 1 and 2, wherein the third radial thickness (E3) is greater than each among the first radial thickness (E1) and of the second radial thickness (E2).
4. The assembly according to any of claims 1 to 3, wherein the second radial thickness (E2) is greater than the first radial thickness (E1).
5. The assembly according to any of claims 1 to 4, wherein the bulge (231, 232) comprises a first lip (231) protruding radially inwardly from the damper (2).
6. The assembly according to any of claims 1 to 5, wherein the bulge (231, 232) comprises a second lip (232) protruding radially outwardly from the damper (2).
7. The assembly according to any of claims 1 to 6, wherein the third part (23) comprises a depression (233).
8. The assembly according to any of claims 1 to 7, wherein each of the blades (122) among the plurality of blades (122) comprises:

   - a blade root (1220) connecting the blade (122) to the disk (120),

   - a profiled blading (1222),

   - a stilt (1224) connecting the blading (1222) to the blade root (1220), and

   - a platform (1226) connecting the blading (1222) to the stilt (1224) and extending transversely to the stilt (1224), the first bearing part (21) bearing on each of the platforms (1226) of the blades (122) among the plurality of blades (122).
9. The assembly according to any of claims 1 to 8, wherein the second rotor (140) comprises a shroud (1402), the shroud (1402) comprising a circumferential extension (1404), the second bearing part (22) bearing on the circumferential extension (1404).
10. The assembly according to any of claims 1 to 9, wherein the damper (2) is annular, and extends all around the longitudinal axis (X-X).
11. A turbomachine (1) comprising an assembly according to any of claims 1 to 10, and wherein the first rotor (12) is a fan and the second rotor (140) is a low-pressure compressor.

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