SECTOR OF A RING FOR A TURBINE OF AN AIRCRAFT TURBOMACHINE

Abstract

Sector (16) of a ring (15) for a turbine (1) of an aircraft turbomachine (2), the sector (16) being circular around a longitudinal axis (X), the sector (16) comprising a body (17) having an internal face (18) on which an abradable layer (19) is attached, the abradable layer (19) being intended to be opposite at least one tip (11) of a blade (9) of a mobile wheel (5), characterized in that the body (17) comprises an upstream rim (20) which projects radially towards the axis (X) and which exceeds the abradable layer (19), the rim (20) being intended to radially cover the tip (11) of the blade (9), the sector (16) further comprising a first internal air circuit (21) which comprises at least one duct (22a-22d) opening onto the upstream edge (20) and / or on the abradable layer (19), the duct (22a-22d) being oriented so that the air jet (J1) coming from the duct (22a-22d) is projected onto the top (11) of the blade (9). Figure for the abstract: 2

Description

Title of the invention: SECTOR OF A RING FOR A TURBINE OF AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a sector of a ring for a turbine of an aircraft turbomachine, as well as to a ring formed by such sectors, but also to a turbine comprising such a ring, and finally to a turbomachine comprising such a turbine. Technical background

[0002] Conventionally, an axial turbine of a turbomachine comprises one or more axial stages arranged one behind the other, each stage comprising a bladed distributor (stator) and a bladed moving wheel (rotor).

[0003] A moving wheel comprises a disc carrying an annular row of blades.

[0004] In the remainder of the application, we will focus on so-called “heelless” blades. A so-called “heelless” blade comprises a blade which has a tip at its free external end. Conversely, a so-called “heeled” blade comprises a blade which has an external end connected to a heel, this heel generally being provided with one or more wipers.

[0005] In order to optimize the efficiency of a turbine, it is necessary to maximize the quantity of exhaust gas acting on the different blades.

[0006] For this, it is known to implant a sectored ring around the moving wheel, this ring being fixed to a casing of the turbine. The ring comprises an abradable layer (for example a metallic or ceramic layer with a honeycomb structure) which is arranged opposite the tips of the blades and which is intended to cooperate with these tips, to form a dynamic labyrinth-type seal.

[0007] From experience, engine manufacturers have observed premature wear of the tip of the blade, which is largely explained by a locally higher temperature of the tip, this temperature being able to reach 1200°C.

[0008] This locally higher temperature is the cause of various harmful phenomena for the summit, namely corrosion, oxidation, burns and cracks.

[0009] Engine manufacturers are therefore mobilized to find solutions to lower the temperature of the blade tip, and consequently to maximize the blade's lifespan.

[0010] The objective of the present invention is therefore to provide a simple, effective solution and economical way to respond to the aforementioned problem. Summary of the invention

[0011] The invention thus proposes a sector of a ring for a turbine of an aircraft turbomachine, the sector being circular around a longitudinal axis X, the sector comprising a body having an internal face on which an abradable layer is attached, the abradable layer being intended to be opposite at least one tip of a blade of a mobile wheel, characterized in that the body comprises an upstream rim which projects radially towards the axis X and which exceeds the abradable layer, the rim being intended to radially cover the tip of the blade, the sector further comprising a first internal air circuit which comprises at least one duct opening onto the upstream rim and / or onto the abradable layer, the duct being oriented so that the air jet from the duct is projected onto the tip of the blade.

[0012] The upstream rim and the air jet from the duct (first air circuit) make it possible to significantly lower the temperature of the tip of the blade, and consequently to maximize the life of the blade.

[0013] In fact, the upstream rim forms a protection or a deflector which deflects the exhaust gases heading towards the peaks, so as to prevent the exhaust gases from coming into direct contact with the peaks.

[0014] In addition, the air jet from the duct (first air circuit) directly impacts the blade tips to maximize their cooling. In addition, the air jet from the duct forms a layer of cold air (or a cold air curtain) between the tips and the ring which not only helps to cool the blade tips, but also forms a barrier (or obstacle) preventing the rise of hot exhaust gases.

[0015] The cold air layer also makes it possible to relax certain dimensional requirements which were associated with obtaining the functional clearance (particularly precise) between the vertices and the abradable layer of the ring.

[0016] The layer of cold air finally forms an additional seal between the peaks and the ring, whatever the operating speed of the turbine, to the benefit of its efficiency.

[0017] The sector according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: - the sector comprises a second internal air circuit which is independent of the first internal air circuit, the second air circuit comprising at least one passage opening onto the abradable layer, the passage being oriented so that the air jet from the passage is projected onto the tip of the blade; - the duct and the passage are each defined by an air inlet and an air outlet, the duct and the passage each extending upstream to downstream from their air inlet to their air outlet; - the passage is supplied by a recess which is formed in the body of the sector and which is open to the outside, the sector further comprising a pierced sheet which covers the recess; - the rim has an upstream end which has in cross section a face inclined relative to the X axis, the radial dimension of the inclined face decreasing from upstream to downstream, so as to deflect the exhaust gases in the direction of the X axis; - the first air circuit comprises several ducts which each open onto the upstream edge and / or onto the abradable layer, each duct being oriented so that the corresponding air jet is projected onto the tip of the blade, the ducts being supplied by a common chamber which is formed in the body; - the sector comprises several first air circuits distributed around the X axis, the first air circuits preferably being distributed regularly.

[0018] The present invention also relates to a ring for a turbine of an aircraft turbomachine, the ring comprising a plurality of sectors as described previously, the sectors being arranged end to end around the X axis.

[0019] The present invention also relates to a turbine of an aircraft turbomachine comprising a ring as described previously and a moving wheel arranged inside the ring, the moving wheel comprising a disc carrying an annular row of blades, each blade comprising a blade which has a tip at its free external end, the abradable layers of the different sectors of the ring being opposite the tips of the blades.

[0020] The present invention finally relates to an aircraft turbomachine comprising a turbine as described previously. Brief description of the figures

[0021] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0022] [Fig-1] [Fig.l] is a schematic and partial view in longitudinal half-section of a turbine of an aircraft turbomachine according to the invention;

[0023] [Fig.2] [Fig.2] is a detail view of [Fig.l];

[0024] [Fig.3] [Fig.3] corresponds to [Fig.2] on which is illustrated the path of cooling air through a sector of a turbine ring;

[0025] [Fig.4] [Fig.4] is a perspective view of a sector of the turbine ring. Detailed description of the invention

[0026] Figures 1 and 2 show a part of a high-pressure turbine 1 (hereinafter referred to as the “turbine”) of a turbomachine 2. The turbine 1 is part of a gas generator which also comprises a compressor and a combustion chamber. More specifically, the turbine 1 is here arranged directly downstream of the combustion chamber, the turbine 1 thus being particularly exposed to high temperatures.

[0027] The turbine 1 comprises at least one stage comprising a bladed distributor 3 which is secured to a casing 4 of the turbine 1 and a bladed wheel 5 which is rotatable about a longitudinal axis X of the turbine 1 (common with the longitudinal axis of the turbomachine). The bladed wheel 5 is arranged downstream of the bladed distributor 3.

[0028] The bladed distributor 3 comprises an annular row of straightening vanes 6. The straightening vanes 6 are arranged between external and internal platforms 7, 47 which define between them the vein 8 of the turbine 1 in which the exhaust gases G from the combustion chamber flow. The bladed distributor 3 is preferably sectorized, each sector comprising for example two or three straightening vanes 6.

[0029] The movable wheel 5 comprises a disc 48 carrying an annular row of blades 9. A blade 9 comprises a root 49 mounted in a cell 50 of the disc 48 and a blade 10 which has a tip 11 at its free external end.

[0030] More precisely, the blade 10 of the vane 9 extends along a stacking axis Z which is substantially perpendicular to the axis X. The blade 10 has a pressure face 12 and an extrados face connected to each other by a leading edge 13 and a trailing edge 14. The exhaust gases G flow around the blade 10 from the leading edge 13 towards the trailing edge 14, the leading edge 13 thus being arranged upstream of the trailing edge 14 in the direction of flow of the exhaust gases G.

[0031] Advantageously, each blade 9 comprises an internal cooling circuit. The internal cooling circuit may for example comprise one or more inlets located at the root 49 of the blade 9 and outlets located along the trailing edge 14 of the blade 10.

[0032] The movable wheel 5 is arranged inside a sectored ring 15 which is integral with the casing 4. The ring 15 thus comprises a plurality of sectors 16 arranged end to end around the axis X.

[0033] Advantageously, sealing means (for example slats and / or plates) are arranged between the sectors 16 to minimize intersector leaks.

[0034] Each sector 16 of the ring 15 is circular around the longitudinal axis X. Each sector 16 comprises a body 17 having an internal face 18 on which an abradable layer 19 is attached. The abradable layer 19 is opposite the tips 11 of the blades 9 surrounded by the sector 16.

[0035] According to the invention, the body 17 of each sector 16 comprises an upstream rim 20 which projects radially towards the axis X and which exceeds the abradable layer 19, the rim 20 radially covering the tips 11 of the blades 9 surrounded by the sector 16. Each sector 16 further comprises a first internal air circuit 21 which comprises at least one duct 22a-22d opening onto the upstream rim 20 and / or onto the abradable layer 19, the duct 22a-22d being oriented so that the air jet J1 coming from the duct 22a-22d is projected onto the tips 11 of the blades 9.

[0036] The upstream rim and the air jet from the duct (first air circuit) make it possible to significantly lower the temperature of the tip of the blade, and consequently to maximize the life of the blade.

[0037] In fact, the upstream rim forms a protection or a deflector which deflects the exhaust gases heading towards the peaks, so as to prevent the exhaust gases from coming into direct contact with the peaks.

[0038] Furthermore, the air jet from the duct (first air circuit) directly impacts the tips of the blades to maximize their cooling. Furthermore, the air jet from the duct forms a layer of cold air (or a curtain of cold air) between the tips and the ring which not only contributes to cooling the tips of the blades, but also forms a barrier (or obstacle) preventing the rise of hot exhaust gases.

[0039] The cold air layer also makes it possible to relax certain dimensional requirements which were associated with obtaining the functional clearance (particularly precise) between the vertices and the abradable layer of the ring.

[0040] The layer of cold air finally forms an additional seal between the peaks and the ring, whatever the operating speed of the turbine, to the benefit of its efficiency.

[0041] In the same way as the turbine 1 or the turbomachine 2, a sector 16 of the ring 15 is defined relative to the longitudinal axis X.

[0042] In the present application, the terms "internal" and "external" are defined with respect to the longitudinal axis X.

[0043] In the present application, the term “interior” associated with an element of sector 16 indicates that this element is arranged inside sector 16. Conversely, the term “exterior” associated with an element of sector 16 indicates that this element is arranged outside sector 16.

[0044] Furthermore, in the present application, the terms "upstream" and "downstream" are defined with respect to the direction of flow of the exhaust gases G.

[0045] The abradable layers of the different sectors 16 of the ring 15 are opposite the tips 11 of the blades 9. The abradable layers are intended to cooperate with the tips 11 of the blades 9 to form a dynamic sealing joint of the la- type labyrinth.

[0046] The abradable layer 19 of a sector 16 may have a constant or variable thickness. The abradable layer 19 may also be stepped.

[0047] The abradable layer 19 may for example be a metallic or ceramic layer with a honeycomb structure.

[0048] The rim 20 extends beyond the abradable layer 19, and in other words the rim 20 extends radially beyond the abradable layer 19, so as to radially cover the tips 11 of the blades 9 surrounded by the sector 16.

[0049] The rim 20 may have an upstream end which has in cross section an inclined face 23 relative to the axis X, the radial dimension of the inclined face 23 decreasing from upstream to downstream, so as to deflect the exhaust gases G in the direction of the axis X. Such an inclination of the upstream end makes it possible to limit disturbances.

[0050] Advantageously, the inclined face 23 of the upstream end is located in the extension of the external platform 7 of the distributor 3, to guarantee aerodynamic continuity, and thus minimize disturbances.

[0051] The first internal air circuit 21 (hereinafter called “first circuit”) of each sector 16 can obviously comprise several ducts 22a-22d which each open onto the upstream rim 20 and / or onto the abradable layer 19. Each duct 22a-22d is oriented so that the corresponding air jet J1 is projected onto the tips 11 of the blades 9.

[0052] Advantageously, the conduits 22a-22d are supplied by a common chamber 24 which is formed in the body 17 of the sector 16. The conduits 22a-22d are connected directly or indirectly to the chamber 24.

[0053] Advantageously, the first circuit 21 comprises at least one conduit 22c, 22d which opens onto the upstream rim 20.

[0054] Each duct 22a-22d is defined by an air inlet 25, an air outlet 26 and an elongation axis.

[0055] For example, a conduit 22a-22d may be of circular, rectangular, etc. section.

[0056] A conduit 22a-22d may have a constant or variable section along its axis of elongation.

[0057] Advantageously, when a conduit 22a-22d has a variable section, its section converges from its air inlet 25 to its air outlet 26, so as to increase the speed of the corresponding air jet J1, and thus increase the cooling of the vertices 11.

[0058] A conduit 22a-22d may extend parallel to the X axis (its axis elongation then being parallel to the X axis) or inclined relative to the axis X (its axis of elongation then being inclined relative to the X axis).

[0059] Advantageously, each conduit 22a-22d extends from upstream to downstream, with reference to the direction of flow of the exhaust gases G, from its air inlet 25 to its air outlet 26. Such an orientation of the conduit(s) 22a-22d makes it possible to have air jets J1 directed in the direction of flow of the exhaust gases G, so as to minimize disturbances.

[0060] Each sector 16 can comprise several first circuits 21 distributed around the X axis.

[0061] Advantageously, the first circuits 21 are distributed regularly.

[0062] The first circuits 21 can be arranged in the form of a row around the X axis.

[0063] Advantageously, the first circuit(s) 21 are supplied with compressed air coming for example from the compressor of the gas generator.

[0064] Each sector 16 may comprise a second internal air circuit 27 (hereinafter called “second circuit”) which is independent of the first circuit 21.

[0065] The second circuit 27 may comprise one or more passages 28 each opening onto the abradable layer 19. Each passage 28 is oriented so that the corresponding air jet J2 is projected onto the tips 11 of the blades 9.

[0066] The passage(s) 28 of a sector 16 may be supplied by a recess 29 which is formed in the body 17 of the sector 16 and which is open to the outside.

[0067] Each sector 16 may further comprise a perforated sheet 30 which covers the recess 29, in particular to regulate the temperature of the body 17.

[0068] In the same way as a conduit 22a-22d, each passage 28 is defined by an air inlet 25, an air outlet 26 and an elongation axis.

[0069] For example, a passage 28 may be of circular, rectangular, etc. section.

[0070] A passage 28 may have a constant or variable section along its axis of elongation.

[0071] Advantageously, when a passage 28 has a variable section, its section converges from its air inlet 25 to its air outlet 26, so as to increase the speed of the corresponding air jet J2, and thus increase the cooling of the tops 11.

[0072] Advantageously, each passage 28 extends from upstream to downstream, with reference to the direction of flow of the exhaust gases G, from its air inlet 25 to its air outlet 26. Such an orientation of the passage(s) 28 makes it possible to have air jets J2 directed in the direction of flow of the exhaust gases G, so as to minimize disturbances.

[0073] Advantageously, the second circuit 27 is supplied with compressed air coming for example from the compressor of the gas generator.

[0074] According to the embodiment illustrated in Figures 1 to 4, each sector 16 is in the form of an arc of a circle around the X axis.

[0075] As illustrated in Figures 1 to 3, each sector 16 comprises an upstream groove 31 in which is housed an upstream hook 32 of the casing 4 and a downstream tab 33 which is secured to a downstream hook 34 of the casing 4 via a holding element 35. The holding element 35 has a “U” shape in cross section.

[0076] As illustrated in Figures 1 to 3, the rim 20 of each sector 16 is arranged upstream of the abradable layer 19. The rim 20 thus radially covers the tips 11 of the blades 9 surrounded by the sector 16.

[0077] The rim 20 is notably defined by an upstream edge 36, a first face 23, a second face 37 and a downstream edge 38.

[0078] More precisely, the upstream edge 36 is in straight and radial cross-section.

[0079] The first face 23 (hereinafter called “inclined face”) is in cross-section inclined relative to the axis X. The radial dimension of the inclined face 23 decreases from upstream to downstream, so as to deflect the exhaust gases G in the direction of the axis X.

[0080] The inclined face 23 is here in the extension of the external platform 7 of the distributor 3, to minimize disturbances.

[0081] The second face 37 is in straight and axial cross-section (i.e. along the X axis).

[0082] The downstream edge 38 is in straight and radial cross-section. The downstream edge 38 is located opposite the leading edge 13 of the blade 10 at its tip 11.

[0083] As illustrated in the figures, the abradable layer 19 of each sector 16 here has a constant thickness.

[0084] As illustrated in [Fig.4], each sector 16 comprises a row of first circuits 21 distributed around the X axis in a regular manner. Each sector 16 also comprises a single second circuit 27.

[0085] The first and second circuits 21, 27 are supplied with compressed air (cooling air or cold air) which is conveyed to an enclosure 39 defined radially between the casing 4 and the ring 15. The compressed air here comes from a compressor of the turbomachine 2.

[0086] As illustrated in [Fig.4], the second circuit 27 comprises three rows of four passages 28. The passages 28 of the same row are distributed around the axis X in a regular manner. The passages 28 each open onto the abradable layer 19, and more precisely onto the internal surface 40 of the abradable layer 19.

[0087] As illustrated in [Fig.3], the passages 28 are oriented so that the air jets J2 corresponding to them are projected onto the tips 11 of the blades 9.

[0088] As illustrated in Figures 1 to 3, the passages 28 each extend so inclined relative to the X axis.

[0089] The passages 28 each extend from upstream to downstream, with reference to the direction of flow of the exhaust gases G, from their air inlet 25 to their air outlet 26.

[0090] The passages 28 each extend radially from the outside to the inside from their air inlet 25 to their air outlet 26.

[0091] The passages 28 are supplied by a central recess 29 which is formed in the body 17 of the sector 16 and which is open to the outside. The recess 29 is notably defined by a bottom wall 41 and an upstream side wall 42 of the body 17. The passages 28 are partly formed in the bottom wall 41 of the body 17 and partly in the abradable layer 19.

[0092] A pierced sheet metal 30 covers the recess 29. The sheet metal 30 comprises a plurality of holes 46 to allow cooling air to pass from the enclosure 39 to a housing 43 defined between the sheet metal 30 and the bottom wall 41 of the body 17.

[0093] As illustrated in Figures 1 to 3, each first circuit 21 comprises four superimposed conduits 22a-22d, namely a first conduit 22a, a second conduit 22b, a third conduit 22c and a fourth conduit 22d. The conduits 22a-22d are referenced from the outside to the inside.

[0094] The first and second conduits 22a, 22b open onto the abradable layer 19, and more precisely onto the internal surface 40 of the abradable layer 19.

[0095] The third and fourth conduits 22c, 22d open onto the rim 20, and more precisely onto the downstream edge 38 of the rim 20.

[0096] As illustrated in [Fig.3], the ducts 22a-22d are oriented so that the corresponding air jets J1 are projected onto the tips 11 of the blades 9.

[0097] More specifically, the first, second and third conduits 22a-22c each extend inclined relative to the X axis. The fourth conduit 22d extends parallel to the X axis.

[0098] The ducts 22a-22d each extend from upstream to downstream, with reference to the direction of flow of the exhaust gases G, from their air inlet 25 to their air outlet 26.

[0099] Furthermore, the first, second and third ducts 22a-22c each extend radially from the outside to the inside from their air inlet 25 to their air outlet 26.

[0100] The conduits 22a-22d are supplied by a common chamber 24 which is formed in the body 17. The chamber 24 comprises an inlet orifice 44 which communicates directly with the enclosure 39. The chamber 24 is partly formed in the upstream side wall 42 and partly in the rim 20 of the body 17.

[0101] The first, second and third conduits 22a-22c are connected directly with the room 24. The fourth conduit 22d is connected indirectly with room 24 via a connector 45.

[0102] As illustrated in [Fig.3], the air jets J1, J2 coming from the ducts 22a-22d and the passages 28 form the layer of cold air C (shown in dotted lines) between the peaks 11 and the ring 15 which not only participates in the cooling of the peaks 11, but which also forms a barrier (or an obstacle) preventing the rise of the exhaust gases G.

[0103] The body 17 of the sector 16 may be metallic, ceramic or made of a composite material (for example a ceramic matrix composite material which has the advantage of resisting very high temperatures).

[0104] The body 17 of the sector 16 is for example produced via a method comprising firstly obtaining a raw body (in particular without the first and second circuits 21, 27) via for example a molding method, and secondly various machining operations carried out on the raw body (in particular the first and second circuits 21, 27), in order to obtain the finished body 17.

[0105] The body 17 of sector 16 could also be obtained by additive manufacturing.

[0106] The illustrated example is in no way limiting, the sector 16 (or the ring) according to the invention could of course be mounted in a low pressure turbine of the turbomachine.

Claims

Claims

1. Sector (16) of a ring (15) for a turbine (1) of an aircraft turbomachine (2), the sector (16) being circular about a longitudinal axis (X), the sector (16) comprising a body (17) having an internal face (18) on which an abradable layer (19) is attached, the abradable layer (19) being intended to be opposite at least one tip (11) of a blade (9) of a mobile wheel (5), characterized in that the body (17) comprises an upstream rim (20) which projects radially towards the axis (X) and which exceeds the abradable layer (19), the rim (20) being intended to radially cover the tip (11) of the blade (9), the sector (16) further comprising a first internal air circuit (21) which comprises at least one duct (22a-22d) opening onto the upstream edge (20) and / or onto the abradable layer (19), the duct (22a-22d) being oriented so that the air jet (J 1 ) coming from the duct (22a-22d) is projected onto the top (11) of the blade (9).

2. Sector (16) according to claim 1, characterized in that the sector (16) comprises a second internal air circuit (27) which is independent of the first internal air circuit (21), the second air circuit (27) comprising at least one passage (28) opening onto the abradable layer (19), the passage (28) being oriented so that the air jet (J2) coming from the passage (28) is projected onto the tip (11) of the blade (9).

3. Sector (16) according to claim 2, characterized in that the duct (22a-22d) and the passage (28) are each defined by an air inlet (25) and an air outlet (26), the duct (22a-22d) and the passage (28) each extending from upstream to downstream from their air inlet (25) to their air outlet (26).

4. Sector (16) according to claim 2 or 3 when dependent on claim 2, characterized in that the passage (28) is supplied by a recess (29) which is formed in the body (17) of the sector (16) and which is open to the outside, the sector (16) further comprising a pierced sheet metal (30) which covers the recess (29).

5. Sector (16) according to one of the preceding claims, characterized in that the rim (20) has an upstream end which has in cross section an inclined face (23) relative to the axis (X), the radial dimension of the inclined face (23) decreasing from upstream to downstream, so as to deflect the exhaust gases (G) in the direction of the axis (X).

6. Sector (16) according to one of the preceding claims, characterized in that the first air circuit (21) comprises several ducts (22a-22d) which each open onto the upstream edge (20) and / or onto the abradable layer (19), each duct (22a-22d) being oriented so that the corresponding air jet (J 1 ) is projected onto the top (11) of the blade (9), the ducts (22a-22d) being supplied by a common chamber (24) which is formed in the body (17).

7. Sector (16) according to one of the preceding claims, characterized in that the sector (16) comprises several first air circuits (21) distributed around the axis (X), the first air circuits (21) preferably being distributed regularly.

8. Ring (15) for a turbine (1) of an aircraft turbomachine (2), the ring (15) comprising a plurality of sectors (16) according to one of the preceding claims, the sectors (16) being arranged end to end around the axis (X).

9. Turbine (1) of an aircraft turbomachine (2) comprising a ring (15) according to the preceding claim and a movable wheel (5) arranged inside the ring (15), the movable wheel (5) comprising a disc (48) carrying an annular row of blades (9), each blade (9) comprising a blade (10) which has a tip (11) at its free external end, the abradable layers of the different sectors (16) of the ring (15) being opposite the tips (11) of the blades (9).

10. Aircraft turbomachine (2) comprising a turbine (1) according to the preceding claim.

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