DEVICE FOR SEALING AND RETURNING A SIDE FLOW FOR A TURBINE NOZZLE

Description

Technical field

[0001] The invention relates to the field of turbomachine turbines, in particular for an aircraft propulsion unit. State of the prior art

[0002] A conventional turbomachine turbine comprises one or more stages each formed by a distributor and a moving wheel equipped with platforms which radially delimit between them a main flow vein of a fluid. The distributor of a stage is configured so as to accelerate the fluid and deflect it towards the blades of the moving wheel of the same stage to drive the latter in rotation.

[0003] In order to reduce the flow rate of vein fluid which tends to bypass such a distributor outside the main vein, it is known to mount at the foot of the distributor a sealing device as described in document FR3027343A1. Another example is disclosed in CN110273712A.

[0004] The bypass fluid, generally called "bypass", which passes through such a sealing device returns to the main vein, generating mixing losses, thus reducing the performance and efficiency of the turbine. Statement of the invention

[0005] In order to improve the performance and efficiency of a turbomachine turbine, the invention relates to a turbomachine distributor extending around a longitudinal axis and comprising a platform, a blade extending radially with respect to the longitudinal axis outwards from the platform, a main flange extending radially inwards from the platform, an abradable element and a support element carrying the abradable element, the support element comprising a flange connected to said main flange, the abradable element being intended to be arranged opposite two wipers carried by a rotor of the turbomachine and which define between them an inter-wiper cavity.According to the invention, the distributor comprises a reinjection duct comprising an inlet configured to open into the inter-lick cavity and an outlet formed at a radially external end of the flange of the support element and configured to open into a cavity extending axially downstream of the distributor, the reinjection duct comprising a section extending into the flange of the support element.

[0006] During operation, a bypass fluid enters the inter-lick cavity. Under the action of the differential pressure between the inter-lick cavity and the cavity downstream of the distributor, which is connected to the main vein, part of the bypass fluid passes through the reinjection conduit.

[0007] Positioning the conduit outlet at the radially outer end of the support element flange allows the bypass fluid to be reinjected into the main vein radially close to the main vein.

[0008] The invention thus makes it possible to reduce mixing losses, which increases the performance and efficiency of the turbine.

[0009] The invention also makes it possible to simplify the manufacture of the distributor and in particular the machining of the reinjection conduit.

[0010] Preferably, said section of the reinjection conduit is straight.

[0011] In one embodiment, the reinjection conduit comprises an inlet section passing through the abradable element.

[0012] This entry section is preferably straight.

[0013] Generally speaking, the presence of straight sections in the reinjection duct makes it easier to machine.

[0014] In one embodiment, the inlet section defines an inlet direction perpendicular to said outlet direction, or forming with it an angle close to 90°.

[0015] In one embodiment, the reinjection conduit comprises an axially extending outlet section.

[0016] The axial orientation of the outlet section thus makes it possible to reinject the bypass fluid into the main vein in a way that minimizes mixing losses with the fluid circulating in the main vein.

[0017] The outlet section of the reinjection duct may have an outlet direction parallel to the longitudinal axis, in order to maximize the axial component of the velocity of the reinjected flow.

[0018] Alternatively, the outlet direction may be oblique to the longitudinal axis so that the outlet section extends both axially and radially. In this case, the angle between the outlet direction and the longitudinal axis, considered in a plane passing both through the longitudinal axis and through a point of intersection of the outlet direction with the outlet section of the reinjection duct, is preferably relatively small, for example less than 20°, so that the radial component is relatively small compared to the axial component of the velocity of the reinjected flow.

[0019] In one embodiment, said outlet section of the reinjection conduit extends tangentially relative to the longitudinal axis.

[0020] The tangential orientation of the outlet section allows the bypass fluid to be reinjected into the main vein by increasing the tangential component of the velocity of the fluid leaving the reinjection conduit, in the same rotating direction as the main flow of fluid circulating in the main vein.

[0021] This further reduces mixing losses and consequently increases turbine performance and efficiency.

[0022] In one embodiment, the outlet section of the reinjection conduit has a section which decreases towards the outlet.

[0023] The outlet section can thus form a cavity converging towards the outlet, making it possible to accelerate the flow leaving the reinjection conduit.

[0024] Preferably, the cross-section of the outlet section decreases monotonically towards the outlet.

[0025] In one embodiment, the flange of the support element comprises a downstream surface and an element extending projecting from this downstream surface and forming the outlet section of the reinjection conduit.

[0026] This element can be an added element or be made with said flange in one piece.

[0027] In one embodiment, the support element is connected to said main flange so as to allow radial movement of the support element relative to this main flange.

[0028] In one embodiment, said flange of the support element is a downstream flange, the support element comprising an upstream flange, said main flange of the distributor extending axially between the upstream flange and the downstream flange of the support element.

[0029] In one embodiment, the distributor comprises a thermal protection sheet fixed on the downstream flange of the support element.

[0030] In a variant of this embodiment, the distributor also comprises another thermal protection sheet fixed to the upstream flange of the support element so that the reinjection conduit extends axially between these two sheets.

[0031] In one embodiment, the blade has a trailing edge defining a line in the extension of which the outlet of the reinjection duct extends.

[0032] In other words, the outlet of the reinjection duct can be placed in the wake of the trailing edge of the blade, approximately in line with it.

[0033] The pressure in the trailing edge wake of the blade is lower than in circumferentially adjacent regions, i.e., extending circumferentially between the trailing edges of two adjacent blades.

[0034] Positioning the outlet of the reinjection duct in the wake of the trailing edge of the blade increases the pressure difference between the inlet and outlet of the duct.

[0035] In one embodiment, the support member of the sealing device is annular.

[0036] The invention also relates to a turbine for a turbomachine, comprising a distributor as defined above.

[0037] In one embodiment, the turbine is a low pressure turbine.

[0038] In one embodiment, the turbine comprises a movable wheel extending axially downstream of the distributor, the movable wheel comprising a spoiler, the outlet of the reinjection duct of the distributor opening radially above said spoiler.

[0039] The invention also relates to a turbomachine for an aircraft propulsion unit, comprising such a turbine.

[0040] According to another aspect, the invention relates to a method of manufacturing a dispenser as defined above.

[0041] In one embodiment, the method comprises a step of machining the support element of the sealing device so as to form the reinjection conduit.

[0042] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the drawings

[0043] The following detailed description refers to the attached drawings in which: [ Fig. 1 ] is a schematic longitudinal sectional view of an aircraft propulsion system; [ Fig. 2 ] is a partial schematic half-view in longitudinal section of a turbomachine turbine according to the invention; [ Fig. 3] is a schematic perspective view of a circumferential portion of a sealing device according to the invention, showing a support element and an abradable element which form a reinjection conduit; [ Fig. 4 ] is a schematic longitudinal sectional view of the sealing device of the figure 3 , according to a section plane passing through part of the reinjection conduit; [ Fig. 5 ] is a schematic view of a circumferential portion of the support element of the sealing device of the figure 3 . Detailed description of embodiments

[0044] The figures include a reference frame L, R and C defining respectively longitudinal / axial, radial and circumferential / tangential directions orthogonal to each other.

[0045] He is represented at the figure 1an aircraft propulsion unit 1 comprising a turbomachine 2 shrouded by a nacelle 3. In this example, the turbomachine 2 is a twin-spool, twin-flow turbojet.

[0046] Subsequently, the terms “upstream” and “downstream” are defined in relation to a direction S1 of flow of gases through the propulsion unit 1 when the latter is propelled.

[0047] The turbojet 2 has a longitudinal central axis A1 around which its various components extend, in this case, from upstream to downstream, a fan 4, a low-pressure compressor 5, a high-pressure compressor 6, a combustion chamber 7, a high-pressure turbine 8 and a low-pressure turbine 9. The compressors 5 and 6, the combustion chamber 7 and the turbines 8 and 9 form a gas generator.

[0048] In operation, an air flow 10 enters the propulsion unit 1 through an air inlet upstream of the nacelle 3, passes through the fan 4 and then divides into a central primary flow 10A and a secondary flow 10B. The primary flow 10A flows in a main gas circulation vein 11A passing through the gas generator. The secondary flow 10B flows in a secondary vein 11B surrounding the gas generator and delimited radially outwards by the nacelle 3.

[0049] The low pressure turbine 9, partially represented in the figure 2 , is configured to recover part of the combustion energy in order to drive in rotation around the axis A1 moving wheels forming the rotor of the turbine 9. Between each pair of adjacent moving wheels, the turbine 9 comprises a stator bladed crown forming a distributor.

[0050] There figure 2partially shows two moving wheels 15 and 16 and turbine 9.

[0051] The distributor 17 extends axially between the movable wheel 15 forming an upstream wheel and the movable wheel 16 forming a downstream wheel.

[0052] In a manner known per se, each of the moving wheels 15 and 16 comprises a disc 20 and blades 21 carried by the disc 20.

[0053] In this example, the disc 20 of the upstream wheel 15 comprises a ferrule 22 extending axially in the direction of the downstream wheel 16, radially inside the distributor 17. A downstream end of the ferrule 22 is connected to the disc 20 of the downstream wheel 16 so as to secure the wheels 15 and 16 to each other in rotation around the axis A1.

[0054] The distributor 17 comprises in this example several sectors arranged circumferentially end to end so as to form together said bladed crown.

[0055] In a manner known per se, each sector of the distributor 17 comprises a platform 25 delimiting radially inwards a portion of the main vein 11A, blades 26 extending radially outwards from the platform 25 and being circumferentially spaced around the axis A1, as well as a flange 27 extending radially inwards from the platform 25.

[0056] The distributor 17 also comprises a sealing device 18 comprising an abradable element 30, also called a wear part, a support element 31 and two wipers 32.

[0057] The abradable element 30, the support element 31 and the wipers 32 each form an annular part of axis A1.

[0058] The support element 31 comprises an axial portion 35 as well as an upstream flange 36 and a downstream flange 37 each extending radially outward from the axial portion 35.

[0059] The axial portion 35 of the support element 31 defines an internal surface on which the abradable element 30 is fixed.

[0060] The flanges 36 and 37 of the support element 31 axially define between them a space receiving the flange 27 of each sector of the distributor 17. The width of this space corresponds substantially to that of the flange 27 of each sector so as to block the axial position of the support element 31 relative to the distributor 17.

[0061] In this example, the position of the support element 31 is also circumferentially locked but is free to move radially relative to the flange 27 of the distributor 17.

[0062] To do this, the flange 27 of each sector of the distributor 17 comprises in this example a radial bore in which a pin 38 mounted tightly in a corresponding orifice of each of the flanges 36 and 37 can slide radially.

[0063] Of course, several pins distributed around the axis A1 can be implemented and cooperate with the flanges 27, 36 and 37 in a similar manner for each of the sectors of the distributor 17.

[0064] The support element 31 is thus connected to the flange 27 so as to allow relative radial displacement of one with respect to the other, it being understood that this freedom of displacement can be ensured by any other sliding means.

[0065] In the example of the figure 2 , the licks 32 of the sealing device 18 are carried by the ferrule 22.

[0066] In operation, the moving wheels 15 and 16 are rotated around the axis A1, which causes friction of the wipers 32 on the abradable element 30, which in this example has a honeycomb structure.

[0067] The device 18 thus ensures dynamic sealing reducing the phenomenon of bypassing of the primary flow 10A radially inside the distributor 17.

[0068] Distributor 17 of the figure 2 also includes thermal protection sheets 65 and 67 carried by flanges 37 and 36 respectively.

[0069] The invention relates more specifically to a means of re-injecting into the main vein 11A a part of the bypass flow passing through the sealing device 18.

[0070] In the embodiment of the figures 2 to 4 , the sealing device 18 forms a reinjection conduit 40 passing through the abradable element 30 and the support element 31.

[0071] The conduit 40 comprises an inlet 41 opening onto an internal surface 42 of the abradable element 30 which corresponds in this case to a friction surface of the wipers 32.

[0072] Axially, the inlet 41 of the conduit 40 extends between the two wipers 32 so as to open into an inter-wiper cavity 43, which is delimited axially upstream by one of the wipers 32, axially downstream by the other wiper 32, radially inwards by the ferrule 22 and radially outwards by the abradable element 30 (see figure 2 ).

[0073] From the inlet 41, the conduit 40 extends radially through the abradable element 30 to an intermediate cavity 45 formed in the axial portion 35 of the support element 31.

[0074] The part of the conduit 40 extending between the inlet 41 and this intermediate cavity 45 forms a straight inlet section 46 having in this example an axis A2 perpendicular to the axis A1.

[0075] In the embodiment of the figures 3 And 4, the support element 31 comprises an element 39 forming a protuberance which extends axially projecting from the downstream flange 37 at one end of this flange 37 radially opposite the axial part 35.

[0076] The conduit 40 comprises an outlet 47 opening onto a downstream surface 48 of the protuberance 39 and consequently at a radially external end of the flange 37.

[0077] Between the intermediate cavity 45 and the outlet 47, the conduit 40 comprises a straight section 49 extending radially through the downstream flange 37 and an outlet section 50 extending axially and tangentially through the protuberance 39.

[0078] In this example, the output section 50 has an axis A3 parallel to the axis A1 and perpendicular to the axis A2 as well as to an axis A4 of the section 49.

[0079] In reference to the figures 3 And 5, the protuberance 39 forming the outlet section 50 of the conduit 40 is oriented in the circumferential direction so that the axis A3 intersects a plane PA1 containing the axis A1.

[0080] In this example, axis A3 and plane PA1 form an angle B1 between 40° and 90°.

[0081] Given this circumferential orientation of the outlet section 50, the inlet 41 and the outlet 47 of the conduit 40 have a different circumferential position relative to each other around the axis A1.

[0082] In reference to the figure 2 , the protuberance 39 is configured so that the outlet 47 of the conduit 40 opens into a cavity 51 extending downstream of the flange 27 of the distributor 17 and being fluidically connected to the main vein 11A.

[0083] In this example, the outlet 47 of the conduit 40 opens radially above a spoiler 60 of the moving wheel 16, this spoiler 60 extending towards the front of the moving wheel 16 axially in the direction of the distributor 17.

[0084] Under the action of the differential pressure between this cavity 51 and the inter-lick cavity 43, a portion of the bypass fluid present in the inter-lick cavity 43 is sucked into the conduit 40 via the inlet 41 and is ejected from it via the outlet 47.

[0085] This portion of fluid is thus reinjected into the cavity 51 and subsequently into the main vein 11A so as to present a speed having a strong axial component as well as a tangential component, which makes it possible to significantly reduce mixing losses.

[0086] In order to accelerate the fluid exiting the reinjection conduit 40, the outlet section 50 of the reinjection conduit 40 has a section which decreases monotonically towards the outlet 47, thus forming a convergent outlet cavity.

[0087] In this example, the protrusion 39 is configured so that the outlet 47 of the reinjection duct 40 extends in the extension of the trailing edge of one of the blades 26 of the distributor 17, in order to accentuate the pressure difference between the cavities 43 and 51.

[0088] Of course, the invention is not limited to the examples and embodiments described above, it also covering, in particular, numerous geometries of the reinjection conduit 40 and / or of the support element 31 and / or of the abradable element 30 and / or of the wipers 32 and / or of the relative position of these different members with respect to each other.

[0089] For example, the sections 46 and / or 49 and / or 50 of the reinjection conduit 40 may have a circular or ovoid or even rectangular cross-section.

[0090] In embodiments not shown, the sealing device comprises more than two lips and the reinjection conduit has an inlet opening into a cavity delimited by a first and a second of said lips and / or an inlet opening into a cavity delimited by the second and by a third of said lips.

[0091] The device may also comprise several reinjection conduits 40 such as that described above, which may for example be circumferentially distributed around the axis A1 so as to each extend under a respective blade 26 of the distributor 17.

[0092] Furthermore, the invention can be implemented in a turbine other than that described above, for example within the high pressure turbine 8.

[0093] Finally, it is recalled that the support element 31 is connected to the flange 27 so as to allow relative radial displacement of one with respect to the other, it being understood that this freedom of movement can be ensured by any other sliding means. A dissociation is thus carried out between, on the one hand, the angular distributor sectors comprising the platform sectors 25, the blades 26 and the main flanges 27, and on the other hand the assembly comprising the abradable element 30 and the support element 31 carrying this abradable element, both preferably annular and non-sectored, and for example produced in a single piece. This embodiment prevents leaks in the intersector spaces of the distributor, thanks to the annular and non-sectored nature of the aforementioned elements. Thus, the main blade flanges 27 are inserted between the elements 36 and 37, and can move radially without driving the annular and non-sectored elements.The radial movements of these separate sets are thus advantageously separated.

[0094] In the invention, the position of the reinjection duct 40 is therefore independent of the radial movements of the blades and of the angular distributor sectors integrating these blades. This makes it possible to control leaks in the intersector spaces, as well as leaks at the labyrinth seal integrating the wipers 32.

Claims

1. A turbine engine (2) nozzle (17) extending around a longitudinal axis (A1) and comprising a platform (25), a blade (26) extending radially with respect to the longitudinal axis (A1) outwards from the platform (25), a main flange (27) extending radially inwards from the platform (25), an abradable element (30) and a support element (31) carrying the abradable element (30), the support element (31) comprising a flange (37) connected to said main flange (27), the abradable element (30) being intended to be arranged opposite two wipers (32) carried by a rotor of the turbine engine (2) and which define therebetween an inter-wiper cavity (43), characterised in that it comprises a reinjection duct (40) comprising an inlet (41) configured to open out into the inter-wiper cavity (43) and an outlet (47) formed at a radially outer end of the flange (37) of the support element (31) and configured to open out into a cavity (51) extending axially downstream of the nozzle (17), the reinjection duct (40) comprising a section (49) extending in the flange (37) of the support element (31).

2. The nozzle (17) according to claim 1, wherein said section (49) of the reinjection duct (40) is straight.

3. The nozzle (17) according to claim 1 or 2, wherein the reinjection duct (40) comprises a straight inlet section (46) passing through the abradable element (30).

4. The nozzle (17) according to any one of claims 1 to 3, wherein the reinjection duct (40) comprises an outlet section (50) extending axially and preferably tangentially with respect to the longitudinal axis (A1).

5. The nozzle (17) according to claim 4, wherein the flange (37) of the support element (31) comprises a downstream surface and an element (39) projecting from this downstream surface and forming the outlet section (50) of the reinjection duct (40).

6. The nozzle (17) according to any one of claims 1 to 5, wherein said flange (37) of the support element (31) is a downstream flange, the support element (31) comprising an upstream flange (36), said main flange (27) of the nozzle (17) extending axially between the upstream flange (36) and the downstream flange (37) of the support element (31).

7. The nozzle (17) according to claim 6, comprising a thermal protection sheet metal (65) fastened on the downstream flange (37) of the support element (31) and preferably another thermal protection sheet metal (67) fastened on the upstream flange (36) of the support element (31) so that the reinjection duct (40) extends axially between these two sheet metals (65, 67).

8. The nozzle (17) according to any one of claims 1 to 7, wherein the blade (26) has a trailing edge defining a line in the continuation of which the outlet (47) of the reinjection duct (40) extends.

9. The nozzle (17) according to any one of claims 1 to 8, wherein the support element (31) is connected to the main flange (27) so as to enable a relative radial movement thereof relative to one another.

10. A turbine (9) for a turbine engine (2), comprising a nozzle (17) according to any one of claims 1 to 9.

11. The turbine (9) according to claim 10, comprising a movable wheel (16) extending axially downstream of the nozzle (17), the movable wheel (16) comprising a spoiler (60), the outlet (47) of the reinjection duct (40) of the nozzle (17) opening out radially above said spoiler (60).

12. A method for manufacturing a nozzle (17) according to any one of claims 1 to 9, comprising a step of machining the support element (31) so as to form the reinjection duct (40).