ARRANGEMENT FOR A TURBOMACH

Description

Technical field of the invention

[0001] The invention relates to an assembly for a turbomachine, such as in particular an aircraft turbojet or turboprop. State of the prior art

[0002] There figure 1 represents a 1a turbomachine with a double flow and a double body. The axis of the turbomachine is referenced X and corresponds to the axis of rotation of the rotating parts. In the following, the terms axial and radial are defined relative to the X axis.

[0003] The turbomachine 1a comprises, from upstream to downstream in the direction of gas flow, a fan 2a, a low-pressure compressor 3a, a high-pressure compressor 4a, a combustion chamber 5a, a high-pressure turbine 6a and a low-pressure turbine 7a. The air from the fan 2a is divided into a primary flow 8a flowing in a primary annular vein 9a, and a secondary flow 10a flowing in a secondary annular vein 11a surrounding the primary annular vein 9a.

[0004] The low pressure compressor 3a, the high pressure compressor 4a, the combustion chamber 5a, the high pressure turbine 6a and the low pressure turbine 7a are arranged in the primary vein 9a.

[0005] The rotor of the high-pressure turbine 6a and the rotor of the high-pressure compressor 4a are rotationally coupled via a first shaft so as to form a high-pressure body.

[0006] The rotor of the low pressure turbine 7a and the rotor of the low pressure compressor 3a are coupled in rotation by means of a second shaft so as to form a low pressure body, the fan 2a being able to be connected directly to the rotor of the low pressure compressor 3a or by means of an epicyclic gear train for example.

[0007] The high-pressure compressor 4a comprises a stator and a rotor capable of pivoting relative to the stator around the X axis of the turbomachine.

[0008] The rotor and stator each comprise a succession of bladed wheels, each bladed wheel comprising a wheel comprising a series of blades distributed around the axis of the turbomachine.

[0009] Each stator vane comprises a blade connected to a radially outer platform and a radially inner platform delimiting the flow path of the air flow within the compressor. A block or ring of abradable material extends radially inward from the radially inner platform. The rotor comprises a shroud comprising an annular zone, wipers extending radially outward from said annular zone, the radially outer end of the wiper cooperating with the block of abradable material so as to form a seal capable of ensuring dynamic sealing in operation. A structure of this type is also known from document EP 3 023 595.

[0010] It turns out that, during operation, a relatively large air flow can pass between the upstream and downstream of the corresponding row of blades, via the radial clearance located between the wipers and the block of abradable material, which negatively impacts the efficiency of the turbomachine.

[0011] EP 1 712 743 A2 discloses a turbine with an abradable seal between a rotor and a stator component. EP 3 409 902 A1 discloses a sealing system for a turbomachine compressor. Presentation of the invention

[0012] The invention aims to remedy this drawback in a simple, inexpensive and reliable manner.

[0013] For this purpose, the invention relates to an assembly for a turbomachine, comprising the characteristics according to claim 1.

[0014] The licker and the tongue define, with the block of abradable material and the annular zone of the shell, baffles or obstacles making it possible to increase the pressure losses and to promote dynamic sealing between the rotor and the stator so as to limit the leakage flow between the upstream and downstream of the blades. In other words, the aforementioned elements form a labyrinth-type seal.

[0015] Furthermore, having a thin tongue, i.e. a low e1 / e2 ratio, makes it possible to increase pressure losses, and therefore the effectiveness of the dynamic seal.

[0016] The terms upstream and downstream are defined in relation to the direction of gas flow within the turbomachine.

[0017] The use of a block of abradable material in the form of a honeycomb makes it possible to better withstand high thermal stresses, particularly when used in a turbomachine turbine. Such a structure also makes it possible to limit the mass of the assembly.

[0018] Having a thin tab also makes it easy to accommodate the tab in the available space while avoiding the risk of collision between the tab and the wiper, particularly due to the effect of the carriage phenomenon. It should be remembered that carriage is the axial displacement of the rotor relative to the stator during operation, due in particular to the dimensional and assembly tolerances between these elements.

[0019] The tongue and / or lip may extend only in a radial plane or may extend obliquely to the radial plane.

[0020] The number of tabs and / or wipers can vary depending on your needs. For example, the set can include two or three wipers. The set can also include one, two, or three tabs, for example.

[0021] The assembly may include a tab located upstream of the lip(s), a tab located downstream of the lip(s), and / or a tab axially between two lip(s).

[0022] The thickness e2 of the lip may be at least equal to the axial dimension of the cells. In the case of cells of different sizes, the thickness e2 of the lip is at least equal to the largest axial dimension of the cells located opposite the lip.

[0023] This ensures that the gas flow cannot bypass the free end of the wiper through the cells of the abradable material block.

[0024] The radially outer surface of the ferrule may include a coating capable of reducing wear of the ferrule in the event of friction between the radially inner end of the tab and the ferrule.

[0025] The coating is for example an abrasive material.

[0026] The radial clearance J1 between the radially inner end of the tab and the ferrule can be between 0.5 and 2 times the clearance J2 between the radially outer end of the wiper and the abradable block.

[0027] This clearance can be measured in a particular configuration, for example hot or cold. In the case where different materials can be used for the different elements, these materials deform differently under the effect of thermal stresses in particular.

[0028] The radial clearance J1 is for example less than 0.5 mm.

[0029] The blade, the radially internal platform, the block of abradable material and the tongue are made in one piece.

[0030] These elements are, for example, produced by additive manufacturing.

[0031] The tongue has a wavy structure.

[0032] Such a structure allows to increase the rigidity of the tongue.

[0033] The profile of the corrugation can correspond to the general profile of the cells of the abradable material block.

[0034] The tongue may have a thickness, i.e. an axial dimension, greater in a radially external zone of the tongue than at its radially internal end.

[0035] Such an enlarged external area increases the rigidity of the tab and makes it less sensitive to vibrations. The radially internal end of the tab, however, retains a limited thickness, so as to reduce friction between the tab and the rotor shell.

[0036] A stiffening strip can be plated and mounted against an upstream or downstream face of the radially internal zone of the tab.

[0037] Such a lamella makes it possible, as previously, to increase the rigidity of the assembly of the tongue and the stiffening lamella. The lamella and the tongue can be made in a single piece or in the form of two separate elements. In the case of separate elements, the tongue and the lamella are mounted so as to be free to move and to slide slightly relative to each other during operation, so as to allow friction between them and thus dampen vibrations.

[0038] The radially inner platform, the block of abradable material and the tab may be annular and sectored, each sector comprising at least two blades connected to a radially inner platform sector, a block of abradable material and at least one tab extending radially inward from said platform sector.

[0039] The various angular sectors of the assembly form, after assembly, an annular assembly. The use of angular sectors makes it easier to assemble the assembly. The number of blades per sector is, for example, between 2 and 10.

[0040] The ferrule and the lips are also annular.

[0041] The invention also relates to a turbomachine comprising an assembly of the aforementioned type.

[0042] The assembly belongs, for example, to the compressor or turbine of the turbomachine. Brief description of the figures

[0043] [ Fig. 1 ] is a schematic axial sectional view of a prior art turbomachine; [ Fig. 2 ] is a perspective view of a rotor sector and a stator portion of an assembly according to an example which is however not covered by claims [ Fig. 3 ] is a perspective view of part of the whole figure 2 ; [ Fig. 4 ] is a side view of part of the whole figure 2 ; [ Fig. 5 ] is a view corresponding to the figure 3 , illustrating one embodiment of the invention; [ Fig. 6 ] is a view corresponding to the figure 4 , illustrating a second embodiment of the invention. Detailed description of the invention

[0044] THE figures 2 à 4 illustrate an assembly for a turbomachine according to which is not covered by the claims.

[0045] The assembly comprises a stator 1 and a rotor 2 capable of pivoting relative to the stator around an axis X, which is the axis of the turbomachine.

[0046] Stator 1 is sectorized here, only one sector being represented in the figures.

[0047] Each sector comprises blades 3, extending radially between a radially external platform 4 and a radially internal platform 5, delimiting the gas flow path within the turbomachine. The number of blades 3 per sector is for example between 2 and 10.

[0048] A block of abradable material 6 extends radially inward from the radially inner platform 5, the block of abradable material 6 has a honeycomb-like structure. The cells 7 here have a hexagonal structure, extend radially and open at their radially inner end.

[0049] Furthermore, flat tongues 8 extend radially inwards from the radially internal platform 5, and more particularly from the radially internal face of the platform 5. The number of tongues 8 is here equal to three, the tongues 8 being regularly spaced axially from each other.

[0050] The tabs 8 and the block of abradable material 6 are located entirely opposite the internal platform 5 and do not extend axially beyond said internal platform 5, so as to limit the axial size.

[0051] The tabs 8, the block of abradable material 6, the platforms 4, 5 and the blades 3 are produced in a single piece, for example by additive manufacturing.

[0052] The rotor 2 comprises a shroud comprising a cylindrical annular part 9 located axially between two rows of blades 10, 11, belonging to two compressor or turbine stages for example. Wipers 12, here two wipers 12, extend radially outwards from the cylindrical part 9. The radially external surface 13 of the cylindrical part comprises an anti-wear coating. The coating is for example an abrasive material allowing the tabs 8 to be worn without damaging the cylindrical part 9.

[0053] The free ends 14 of the wipers 12, that is to say the radially external ends 14 of the wipers 12, are capable of cooperating with the radially internal surface of the block of abradable material 6, so as to form a dynamic seal.

[0054] The free ends 15 of the tongues 8, that is to say the radially internal ends 15 of the tongues 8, are capable of cooperating with the radially external surface 13 of the cylindrical part 9, so as to improve the efficiency of the dynamic seal. The profiles of the free ends 15 of the tongues 8 preferably have projecting angles, so as to increase the pressure losses.

[0055] A clearance J1 is provided between the radially internal ends 15 of the tabs 8 and the cylindrical part 9. Similarly, a clearance J2 is provided between the radially external ends 14 of the tabs and the block of abradable material 6. These clearances J1, J2 can vary depending in particular on the effects of differential expansion.

[0056] Generally, the clearance J1 is for example between 0 and 1 mm. More generally, the clearance J1 is between 0.5 and 2 times the clearance J2. It should be noted that, since the sealing is directly a function of the smallest section of the dynamic seal, having a clearance J1 greater than 2 times J2 does not have a significant impact on the effectiveness of the tabs 8.

[0057] We define by e1 the thickness e1 of each tab 8, that is to say the axial dimension of each tab 8, at its radially internal end.

[0058] We define by e2 the thickness of each lip 12, that is to say the axial dimension of each lip 12.

[0059] The ratio e1 / e2 is for example less than or equal to 0.2.

[0060] More generally, the thickness e2 of each lip 12 is at least equal to the axial dimension of each cell 7 of the block of abradable material 6. In this way, it is ensured that the gas flow cannot bypass the free end 14 of the lip 12 through the cells 7 of the block of abradable material 6.

[0061] The licker 12 and the tongue 8 define, with the block of abradable material 6 and the cylindrical part 9, baffles or obstacles making it possible to increase the pressure losses and to promote dynamic sealing between the rotor 2 and the stator 1 so as to limit the leakage flow between the upstream and downstream of the stator blades 1. In other words, the aforementioned elements form a labyrinth-type seal.

[0062] The terms upstream and downstream are defined in relation to the direction of gas flow within the turbomachine.

[0063] The use of a block of abradable material 6 in the form of a honeycomb makes it possible to better withstand high thermal stresses, particularly in the case of use in a turbomachine turbine. Such a structure also makes it possible to limit the mass of the assembly.

[0064] The fact of having thin tabs 8, that is to say a low e1 / e2 ratio, makes it possible to easily accommodate the tabs 8 in the available space while avoiding a risk of collision between the tabs 8 and the wipers 12, in particular under the effect of the carriage phenomenon. Furthermore, the use of thin tabs 8 makes it possible to increase the pressure losses and therefore to improve the efficiency of the dynamic seal.

[0065] There figure 5 illustrates an embodiment of the invention in which each tab 8 has a corrugated structure whose corrugation profile corresponds substantially to the hexagonal profile of the cells 7 of the block of abradable material 6. Such an embodiment makes it possible to increase the rigidity of the tab 8.

[0066] There figure 6 illustrates yet another embodiment in which a flat stiffening strip 16 is pressed against and mounted against an upstream or downstream face, here a downstream face, of the radially internal zone of each tab 8.

[0067] Such a strip 16 makes it possible, as previously, to increase the rigidity of the assembly of the tongue 8 and the stiffening strip 16. The strip 16 and the tongue 8 are two separate elements and are free to move and slide slightly relative to each other during operation, so as to allow friction between them and thus dampen vibrations during operation.

Claims

1. Assembly for a turbomachine, comprising a stator (1) and a rotor (2) rotatable relative to the stator (1) about an axis (X), the stator (1) comprising blades each comprising a vane (3) connected to a radially inner platform (5), a block of abradable material (6) extending radially inwardly from the radially inner platform (5) the rotor (2) comprising a shroud which comprises an annular area (9), at least one lug (12) extending radially outwardly from said annular area (9), the radially outer end of the lug (12) cooperating with the block of abradable material (6), the block of abradable material (6) having a honeycomb structure with cells (7) opening radially inwards, at least one tab (8) extending radially inwards from the platform (5) or the block of abradable material (6), the radially inner end (15) of the tab (8) cooperating with the annular area (9) of the stator shroud (1), the ratio e1 / e2 of the thickness e1 of the tab (8), namely the axial dimension of the tab (8), to the thickness e2 of the lug (12), namely the axial dimension of the lug (12), is less than 5, preferably less than 0.2, characterised in that the tab (8) has a corrugated structure with a profile of corrugation corresponding to a general profile of the cells (7) of the block of abradable material (6).

2. Assembly according to claim 1, characterized in that the thickness e2 of the lug (12) is at least equal to the axial dimension of the cells (7).

3. Assembly according to claim 1 or 2, characterised in that the radially outer surface (13) of the shroud comprises a coating adapted to reduce wear of the shroud in the event of friction between the radially inner end (15) of the tab (8) and the shroud.

4. Assembly according to any one of claims 1 to 3, characterized in that the radial clearance J1 between the radially inner end of the tab (8) and the annular zone (9) is between 0.5 and 2 times the clearance J2 between the radially outer end of the lug (12) and the abradable block (6).

5. Assembly according to any one of claims 1 to 4, characterized in that the blade (3), the radially inner platform (5), the abradable material block (6) and the tab (8) are made of one piece.

6. Assembly according to any one of claims 1 to 5, characterized in that the tab (8) has a greater thickness, namely an axial dimension, in a radially outer area of the tab (8) than at its radially inner end.

7. Assembly according to any one of claims 1 to 5, characterised in that a stiffening plate (16) is pressed against and mounted on an upstream or downstream face of the radially inner area of the tab (8).

8. An assembly according to any of claims 1 to 7, characterised in that the radially inner platform (5), the block of abradable material (6) and the tabs (8) are annular and sectorised, each sector comprising at least two blades (3) connected to a radially inner platform sector (5), a block of abradable material (6) and at least one tab (8) extending radially inwardly from said platform sector (5).

9. A turbomachine according to any one of claims 1 to 8.