FR3140115A1 - Part for damping deformations of an oil recovery casing, assembly which comprises it and turbomachine thus equipped - Google Patents

Abstract

The present invention relates in particular to a part (3) for damping deformations of an oil recovery casing (2) of a turbomachine, characterized in that it comprises: a metal sheet (30) of generally annular shape and of longitudinal axis (X-X'), which comprises a slot (31) which extends parallel to its generators and defines two longitudinal slot edges (300, 301), this sheet (30) being deformable between two positions extremes, namely first extreme position called "free state position" in which said edges (300, 301) of slot (31) are distant from each other and a "restricted state position" in which said edges (300, 301) of slot (31) are contiguous or almost contiguous, which gives said ring an axisymmetric shape. Figure for the abstract: figure 5

Description

Part for damping deformations of an oil recovery casing, assembly which comprises it and turbomachine thus equipped FIELD OF THE INVENTION

The present invention relates to a part for damping deformations of an oil recovery casing, an assembly which comprises this part as well as a casing, and turbomachine thus equipped.

STATE OF THE ART

For the record, we briefly recall below the structure of a double-flow turbomachine, with reference to the annexed.

On this, we can see a turbomachine 1 with double flow and double body with successively, in the direction of air circulation, that is to say from upstream (on the left in the figure) towards downstream (on the right in the figure), an air inlet 10 and a blower 11, which delivers the air on the one hand in a primary vein 12 and on the other hand in a secondary vein 13. By "vein ", we mean the volume through which an air flow circulates.

The longitudinal axis of the turbomachine is referenced X-X’.

The air flow circulating in the primary vein 12 successively passes through a low pressure compressor 14a, a high pressure compressor 14b, a combustion chamber 15, a high pressure turbine 16a and a low pressure turbine 16b, before being ejected.

The present invention concerns an oil recovery casing which is a member part of the aforementioned low pressure turbine 16b, and whose main functions are to ensure oil/air sealing, and the drainage of the oil contained. in an enclosure downstream of the turbomachine.

More precisely, with reference to the aforementioned and to the also annexed, the blower 11 and the low pressure compressor 14b are integral with the low pressure turbine 16b intended to rotate them, via two cylindrical parts called low pressure compressor shaft (or "Fan Shaft") and low pressure turbine shaft.

Within a turbomachine, the low pressure turbine shaft (not shown in the ) is supported by a bearing R itself lubricated by an oil mist in a lubrication chamber CL surrounding this bearing R. This lubrication chamber is defined between an exhaust casing (which is a fixed part) and a part rotating constituted by the downstream end of the low pressure turbine shaft. In practice, sealing in this area is guaranteed by a first rotating seal.

This lubrication chamber CL is, in general, surrounded radially outwards by two chambers, namely a pressurization chamber CP and a recovery chamber CR, also called in terms of the cavity profession “Sump Flooding”.

The sealing of the CP chamber in relation to its two neighbors is ensured by wipes L and cartridges of abradable material AB. As its name suggests, the CP pressurization chamber presents a pressure differential compared to the CL lubrication chamber, which opposes possible oil leaks.

These chambers are therefore designed to prevent infiltration of possible oil leaks into engine compartments not designed to support them. This phenomenon could in particular occur in the rotor of the low pressure turbine, which would have the effect of creating an unbalance damaging the rotor.

In practice and in any case, even if oil flows into the recovery chamber CR, the latter is delimited radially towards the outside by an oil recovery casing 2 which has the function to receive the oil and direct it towards a recovery pipe T. The path of the oil is shown in by an arrow in broken lines.

This architecture ensuring the sealing of the CL enclosure of the bearing R as well as the recovery of the oil used is effective. However, it may present limits from the point of view of the mechanical integrity of certain parts.

This is particularly the case of the oil recovery casing 2 which is not only subjected to aerodynamic forces induced by the pressures of the cavities surrounding this casing, but also to mechanical stresses on the cartridge of abradable material AB which equips it. , leading to radial movements of this part of the casing.

In Figures 3 and 4 is schematically represented such a type of casing 2 on which we identify its cylindrical barrel 20 of axis X-X', its peripheral fixing flange 21 which extends circumferentially outwards at one end of the barrel and perpendicular to said axis, as well as its peripheral ring 22 which equips the opposite end of the barrel 20 and which is lined with an abradable material 23 on its radially internal face.

The two aforementioned stresses can couple together and lead to the instability of the labyrinth (consisting of the ring 22 and the abradable opposite) of the casing 2. Thus, the deflection of a part of the casing causes the variation the maze game. This variation in clearance then disrupts the pressure fields of the associated cavities. The alternating variation of the pressure fields can animate the casing with a random vibratory movement, which excites the latter on one or more of its own vibration modes. These modal deformations then induce a fluctuation of the pressure fields out of phase with the movements of the casing.

One of the components of the pressure fields is homogeneous with a damping force, so that if the value of this component is positive then, the damping will attenuate the movement. The corresponding vibration mode is said to be stable. If the damping is negative, the movement diverges, which will lead to damage to the structure. The vibrational mode is said to be unstable.

At worst, this can lead to cracks or micro-cracks in the connection area of barrel 20 to flange 21.

In such circumstances and to solve such a problem, there is currently no other solution than to design a new casing. Unfortunately, such "re-designs" are time-consuming and very expensive. Indeed, this requires carrying out engine tests, validating new designs and making the corresponding adaptations to the parts in operation concerned, that is to say in use.

The present invention aims precisely to solve, at least in part, these difficulties.

For this purpose, a first aspect of the invention relates to a part for damping the deformations of an oil recovery casing of a turbomachine, characterized in that it comprises:
a metal sheet of generally annular shape and longitudinal axis, which includes a slot which extends parallel to its generators and defines two longitudinal slot edges,
this sheet being deformable between two extreme positions, namely first extreme position called "free state position" in which said slot edges are spaced apart from each other and a "clamped state position" in which said edges slots are contiguous or almost contiguous, which gives said ring an axisymmetric shape.

Thanks to these characteristics and as will be seen in more detail in the description, when this part is inserted into the barrel of the oil recovery sump, it actively participates in the dissipation of the vibration energy of the latter and contributes to prolonging noticeably the "lifespan" of this casing.

According to other advantageous and non-limiting characteristics of this part, taken alone or according to a technically compatible combination of at least two of them:

- said sheet metal is crenellated, so that its section, along a longitudinal section plane, presents, alternately and in the clamped state position, angular sectors of a first and a second diameter;

- the periphery of one of the ends of said sheet is provided with a plurality of tabs directed radially outwards;

- said legs are distributed into two groups of legs which face each other angularly;

- in said free state position, said slot edges are angularly spaced apart by an angle of between 10 and 15°;

- said sheet is made of a nickel-based metal;

- said sheet metal is multi-perforated;

- said sheet has a thickness of between 0.4mm and one millimeter.

The present invention also relates to a low pressure turbine assembly of a turbomachine comprising, on the one hand, an oil recovery casing arranged between, radially inside, an oil recovery chamber and radially inside. the outside, a rotor cavity of the low pressure turbine, the oil recovery chamber itself being arranged radially outside a pressurization chamber and a lubrication chamber radially separated from one of the other by a casing, the oil recovery casing comprising a cylindrical barrel, a peripheral fixing flange which extends circumferentially outwards at one end of said barrel and perpendicular to the axis of the latter, and a peripheral ring which equips the opposite end of said barrel and is lined on its radially internal face with an abradable material arranged opposite annular lips of a sealing labyrinth, and on the other hand a piece of damping, said damping piece being at least partially pressed against the radially internal wall of said barrel.

Advantageously, said damping part has a length at most equal to that of the barrel of the casing.

The invention finally relates to a turbomachine equipped with such an assembly.

DESCRIPTION OF FIGURES

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

is a simplified view in axial section of a double-flow turbomachine of the state of the art;

is a simplified sectional view of a part of a turbomachine, this view being intended to illustrate the architecture of chambers in the vicinity of the low pressure turbine shaft of the turbomachine;

is a perspective view of an oil recovery casing which equips one of these chambers;

is a detailed sectional view of part of the casing of the ;

is a first perspective view of an embodiment of a damping part according to the present invention;

is a second perspective view of the piece from the ;

is a first perspective view of an assembly formed by a casing conforming to the and a damping part conforming to Figures 5 and 6, the latter, seen through transparency, being engaged in the barrel of the casing;

is a second perspective view of the entire ;

is a partial view, along a longitudinal section plane of all of Figures 7 and 8;

is a diagram symbolically showing the damping part in two different states;

is a diagram symbolically showing the damping part arranged inside the casing;

is a diagram analogous to the which shows the possible positions of the barrel of the casing and the damping part as a function of alternations of a first mode of vibration;

is a diagram analogous to the which shows the possible positions of the barrel of the casing and the damping part as a function of alternation of a second mode of vibration;

is a diagram intended to symbolically show the deformation modes of the damping part.

In all the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

As indicated previously, a first aspect of the invention relates to a part for damping deformations of an oil recovery casing as described above.

An example of such a damping part 3 is particularly visible in Figures 5 and 6.

It comprises a metal sheet 30 of generally annular shape and of longitudinal axis XX'. To the , its longitudinal dimension (length) is referenced L and its opposite ends (forming opposite circular edges) are referenced 32 and 33.

This sheet 30 includes a slot 31 which extends parallel to its generators and defines two longitudinal edges 300 and 301 of slot 31.

This sheet 30 is deformable between two extreme positions, namely a first extreme position called "free state position" in which said slot edges 300 and 301 are spaced apart from each other (this is the position shown on Figures 5 and 6) and a "clamped state position" (not shown in the figures) in which said slot edges 300 and 301) are contiguous or almost contiguous, which gives the ring an axisymmetric shape.

Of course, the sheet metal is likely to occupy intermediate positions between these extreme positions, which can however also be described as clamped state positions.

According to a possible embodiment, in the free state position of Figures 5 and 6, the edges 300 and 301 of slot 31 are angularly spaced apart by an angle α of between 10 and 15°.

Advantageously and as shown in the appended figures, the sheet metal 30 is crenellated, so that its section, along a longitudinal section plane passing through the slot 31, presents, alternately and in the extreme position of the clamped state, angular sectors 302 and 303 respectively of a first diameter and a second diameter, the second diameter being smaller than the previous one. The benefit of such a structure will be explained later in the description.

In a variant not shown here, the surface of the sheet 30 could be regular, that is to say not crenellated.

According to the embodiment shown here, the periphery of one 32 of the ends of the sheet 30 is provided with a plurality of four tabs 34 directed outwards. These legs 34 are in one piece with the sheet 30 and constitute as many appendages curved at 90° outwards. We will explain its function later.

In the embodiment shown here, these legs 34, eight in number, are distributed into two groups of legs which face each other angularly. Of course, we could be dealing with a different number, for example higher, and/or with a regular distribution of these all around the periphery of the sheet.

In one possible embodiment, the sheet 30 is made of a nickel-based metal, for example an Inconel type alloy (registered trademark) in order to withstand the mechanical stresses and the high temperatures present within the turbine in which such part 3 is intended to be assembled.

Advantageously, the sheet has a thickness of between 0.4 mm and one millimeter.

According to the embodiment shown in the figures, said sheet metal 30 has a multitude of perforations 35. This makes it possible to limit its mass and reduce the mass impact linked to the installation of this part in its environment.

This part 3 aims to cooperate with the casing 2 described above to form an assembly E, in order to absorb the vibrations of this casing.

To do this, the length L of the sheet 30 is at most equal to that of the barrel 20 of the casing 2.

In free state position visible at the and considering that part 3 is axisymmetric, it has a diameter D2 greater than the diameter D1 of the barrel 20 of the casing 2.

By mechanically closing the slot 31, that is to say by bringing the edges 300 and 301 of this slot 31 together using suitable tools, the sheet 30 closes, becomes axisymmetric, so that its diameter is reduced to go from D2 to D0.

In this clamped state position, the aforementioned diameter D0 is less than the diameter D1 of the barrel 20 of the casing 2, so that the sheet 30 can be installed inside this casing.

The tooling can then be released. Prior to this operation, care will have been taken to position the part 3 so that the tabs 34 are positioned at the base of the flange 21 of the casing 2. Thus, the tabs 34 form stops which limit the axial movement of the sheet metal within the casing, as this is particularly visible at the .

The observation of the allows us to clearly understand how the sheet metal 30 of part 3 is supported against the barrel 20 of the casing 2 only by the crenellated sectors 302.

It appears from the above that the integration of part 3 into the casing is easy and that it is easily accessible if necessary.

The function of part 3 is to dissipate the vibration energy of casing 2 in which it is installed.

We have schematically represented in the the positions E1 and E2 respectively of free state and partially clamped state of part 3.

Part 3 installed in housing 2, as shown in , is in a partially constrained or restrained state, and in fact, tends to want to return to its natural or free state, which presses it against the internal wall of the barrel 20. In other words, the part 3 naturally presents, c that is to say in the free state, a diameter D2 greater than the diameter of the part when it is placed in the barrel 20. The part 3 inserted in the barrel is thus prestressed so as to remain in contact with the barrel by being pressed against the radially internal wall of the barrel 20.

To the , the barrel 20 is represented firstly in its static state ES, that is to say not subject to vibrations. It is again represented in another position while it is subjected to a first vibrational mode EV. We thus see that the barrel 20 and the part 3 deform in substantially the same way.

There is similar to the previous one, except that the two elements are subject to another vibrational mode.

In accordance with the invention, the dissipation of the vibration energy suffered by the casing 2 is done by dry friction between the barrel 20 of the casing 2 which deforms under aeroelastic stresses and the sheet metal 30 of the damping part.

When the surface of the sheet 30 is regular, that is to say not crenellated, it is normally this entire surface which participates in this dry friction.

When it is crenellated (as shown in the figures), only the zones 302 of larger diameter bearing on the barrel 20 participate in the dry friction. In other words, the zones 301 of smaller diameter are not in contact with the radially internal wall of the barrel 20. We therefore observe an alternation of portions in contact or not with the radially internal wall of the barrel, as illustrated as an example of , which reduces the contact surface of the sheet 30 with the barrel 20 and thus the dry friction between these two elements, in comparison with a regular sheet, that is to say without crenellations or undulations. It should nevertheless be noted that by multiplying the zones of larger diameter, we increase the probability that the majority of them are in support against the barrel (unlike a single regular non-crenellated surface which risks only being in support on a region thereof) so as to improve the shock absorber function of the sheet 30.

Thus, the part 3 forming a shock absorber placed inside the barrel 20, that is to say against its radially internal wall, directly dampens the majority of the vibration modes of the casing 2 by stressing it by the dry friction between the barrel and part 3, which dissipates much of the vibrational energy by converting it into heat energy.

It appears from the above that using a simple insert, we can dampen the vibration responses of the structure. This is a more lasting and corrective technical solution than existing solutions which consist of replacing existing casings.

The proposed solution has the specificity of tackling the source of the damage, namely the high levels of vibration response of the structure's own modes.

It should also be noted that if any damage appears on part 3, it is easy to access and replace it. Finally, from a financial point of view and compared to replacing a casing, part 3 is easy to produce and very inexpensive.

Claims (11)

Part (3) for damping deformations of an oil recovery casing (2) of a turbomachine (1), characterized in that it comprises:
a metal sheet (30) of generally annular shape and longitudinal axis (X-X'), which includes a slot (31) which extends parallel to its generators and defines two longitudinal slot edges (300, 301),
this sheet (30) being deformable between two extreme positions, namely first extreme position called "free state position" in which said edges (300, 301) of slot (31) are distant from each other and a "clamped state position" in which said edges (300, 301) of slot (31) are contiguous or almost contiguous, which gives said ring an axisymmetric shape. Damping part (3) according to claim 1, characterized in that said sheet metal (30) is crenellated, so that its section, along a longitudinal section plane, presents, alternately and in the clamped state position, angular sectors of a first (302) and a second (303) diameter. Damping part (3) according to one of claims 1 or 2, characterized in that the periphery of one of the ends (32) of said sheet (30) is provided with a plurality of tabs (34) directed radially outwards. Damping part (3) according to claim 3, characterized in that said tabs (34) are distributed according to two groups of tabs which face each other angularly. Damping part (3) according to one of claims 1 to 4, characterized in that in said free state position, said edges (300, 301) of slot (31) are angularly spaced apart by an angle comprised between 10 and 15°. Damping part (3) according to one of claims 1 to 5, characterized in that said sheet (30) is made of a nickel-based metal. Damping part (3) according to one of claims 1 to 6, characterized in that said sheet metal (30) is multi-perforated. Damping part (3) according to one of claims 1 to 7, characterized in that said sheet metal (30) has a thickness of between 0.4mm and one millimeter. Low pressure turbine assembly (E) of a turbomachine (1) comprising, on the one hand, an oil recovery casing (2) arranged between, radially inside, an oil recovery chamber (CR ) and, radially outside, a rotor cavity of the low pressure turbine, the oil recovery chamber (CR) itself being arranged radially outside a pressurization chamber (CP) and d 'a lubrication chamber (CL) separated radially from one another by a casing, the oil recovery casing (2) comprising a cylindrical barrel (20), a peripheral fixing flange (21) which is extends circumferentially outwards at one end of said barrel (20) and perpendicular to the axis of the latter, and a peripheral ring (22) which equips the opposite end of said barrel (20) and is lined on its radially internal face of an abradable material (23) arranged opposite annular lips (L) of a sealing labyrinth, and on the other hand a damping part (3) in accordance with one of the preceding claims , said damping piece (3) being at least partially pressed against the radially internal wall of said barrel (20). Assembly (E) according to claim 9, characterized in that said damping part (3) has a length at most equal to that of the barrel (20) of the casing (2). Double flow turbomachine, characterized in that it comprises an assembly (E) according to claim 9 or claim 10.