Assembly for a turbomachine

Abstract

The invention relates to an assembly for a turbomachine, comprising a stator (1) and a rotor (2) rotatable relative to the stator (1) about an axis, the rotor (2) 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 stator (1) having a shroud comprising 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).

Claims

1. An 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)e; the rotor (2) having a shroud comprising 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); characterized in that the block of abradable material (6) has 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) in the axial dimension of the tab (8), to the thickness e2 of the lug (12), in the axial dimension of the lug (12), is less than 5, wherein tab (8) has a corrugated structure with a corrugation profile substantially corresponding to the honeycomb structure of the cells (7).

2. The 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. The assembly according to claim 1, 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. The assembly according to claim 1, 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. The assembly according to claim 1, 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. The assembly according to claim 1, characterized in that the tab (8) has a corrugated structure.

7. The assembly according to claim 1, characterized in that the tab (8) has a greater thickness in the axial dimension, in a radially outer area of the tab (8) than at its radially inner end.

8. The assembly according to claim 1, 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).

9. The assembly according to claim 1, 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).

10. A turbomachine according to claim 1.

11. The assembly according to claim 1, wherein the ratio e1/e2 is less than 0.2.

12. An 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) having a shroud comprising 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); characterized in that the block of abradable material (6) has 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) in the axial dimension of the tab (8), to the thickness e2 of the lug (12) in the axial dimension of the lug (12), is less than 5, preferably less than 0.2; and wherein 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), and tab (8) has a corrugated structure with a corrugation profile substantially corresponding to the honeycomb structure of the cells (7).

13. The assembly according to claim 12, 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.

14. The assembly according to claim 12, characterized in that the tab (8) has a corrugated structure.

15. The assembly according to claim 12, characterized in that the tab (8) has a greater thickness in the axial dimension, in a radially outer area of the tab (8) than at its radially inner end.

16. The assembly according to claim 12, 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).

17. The assembly according to claim 12, 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).

18. A turbomachine according to claim 12.

19. The assembly according to claim 12, wherein the ratio e1/e2 is less than 0.2.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic axial sectional view of a turbomachine of the prior art;

(2) FIG. 2 is a perspective view of a rotor sector and part of the stator of an assembly according to a first embodiment of the invention;

(3) FIG. 3 is a perspective view of a part of the assembly of FIG. 2;

(4) FIG. 4 is a side view of a part of the assembly of FIG. 2;

(5) FIG. 5 is a view corresponding to FIG. 3, illustrating a second embodiment of the invention;

(6) FIG. 6 is a view corresponding to FIG. 4, illustrating a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIGS. 2 to 4 illustrate an assembly for a turbomachine according to a first embodiment of the invention.

(8) The assembly comprises a stator 1 and a rotor 2 capable of pivoting relative to the stator about an axis X, which is the axis of the turbomachine.

(9) The stator 1 is sectorised here, with only one sector shown in the figures.

(10) Each sector comprises blades 3, extending radially between a radially outer platform 4 and a radially inner platform 5, delimiting the gas flow path within the turbomachine. The number of blades 3 per sector is for example between 2 and 10.

(11) A block of abradable material 6 extends radially inwardly from the radially inner platform 5, the block of abradable material 6 has a honeycomb structure. The cells 7 have a hexagonal structure, extend radially and are open at their radially inner end.

(12) In addition, planar tabs 8 extend radially inwardly from the radially inner platform 5, and more particularly from the radially inner side of the platform 5. The number of tabs 8 is here equal to three, the tabs 8 being evenly spaced axially from each other.

(13) The tabs 8 and the abradable material block 6 are located entirely opposite the inner platform 5 and do not extend axially beyond said inner platform 5, so as to limit the axial bulk.

(14) The tabs 8, the abradable material block 6, the platforms 4, 5 and the blades 3 are made in one piece, for example by additive manufacturing.

(15) The rotor 2 has a shroud comprising a cylindrical annular portion 9 located axially between two rows of blades 10, 11, belonging to two compressor or turbine stages for example. lugs 12, in this case two lugs 12, extend radially outwardly from the cylindrical portion 9. The radially outer surface 13 of the cylindrical part has a wear resistant coating. The coating is, for example, an abrasive material which allows the tabs 8 to be worn away without damaging the cylindrical part 9.

(16) The free ends 14 of the lugs 12, i.e. the radially outer ends 14 of the lugs 12, are adapted to cooperate with the radially inner surface of the abradable material block 6, so as to form a dynamic seal.

(17) The free ends 15 of the tabs 8, i.e. the radially inner ends 15 of the tabs 8, are adapted to cooperate with the radially outer surface 13 of the cylindrical portion 9, so as to improve the efficiency of the dynamic seal. The profiles of the free ends 15 of the tabs 8 preferably have protruding angles, so as to increase the pressure losses.

(18) A clearance J1 is provided between the radially inner ends 15 of the tabs 8 and the cylindrical portion 9. Similarly, a clearance J2 is provided between the radially outer ends 14 of the lugs and the abradable material block 6. These clearances J1, J2 can vary depending in particular on the effects of differential expansion.

(19) In general, 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, as the sealing is a direct function of the smallest section of the dynamic seal, having a clearance J1 greater than 2 times J2 has no appreciable impact on the effectiveness of the tabs 8.

(20) The thickness e1 of each tab 8 is defined as the axial dimension of each tab 8 at its radially inner end.

(21) The thickness of each lug 12 is defined by e2, i.e. the axial dimension of each lug 12. The ratio e1/e2 is, for example, less than or equal to 0.2.

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

(23) The lug 12 and the tab 8 define, together with the abradable material block 6 and the cylindrical part 9, baffles or obstacles allowing to increase the pressure losses and to favour the 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 above-mentioned elements form a labyrinth-like joint.

(24) The terms ‘upstream’ and ‘downstream’ are defined with respect to the gas flows through the turbomachine.

(25) 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 whole.

(26) The fact of having thin tabs 8, i.e. a low ratio e1/e2, 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 lugs 12, in particular under the effect of the phenomenon of carriage. In addition, the use of thin tabs 8 increases the pressure drop and thus improves the efficiency of the dynamic seal. FIG. 5 illustrates a further embodiment in which each tab 8 has a corrugated structure with a corrugation profile substantially corresponding to the hexagonal profile of the cells 7 of the abradable material block 6. Such an embodiment increases the rigidity of the tab 8. FIG. 6 illustrates yet another embodiment in which a planar stiffening plate 16 is plated and mounted against an upstream or downstream face, here a downstream face, of the radially inner area of each tab 8.

(27) Such a plate 16 makes it possible, as before, to increase the rigidity of the assembly of the tab 8 and the stiffening plate 16. The plate 16 and the tab 8 are two separate elements and are free to move and slide slightly relative to each other in operation, so as to allow friction between them and thus dampen vibrations in operation.