Improving sealing in a turbomachine turbine
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2022-09-22
- Publication Date
- 2026-07-24
AI Technical Summary
Existing sealing solutions for turbomachine turbines face issues with thermal protection and crack formation due to different material expansion coefficients, and potential contact with moving parts, compromising performance and integrity.
A sealing assembly featuring an annular thermal deflector with multiple walls and an elastic member that thermally protects structural elements without welding, reducing the risk of crack formation and contact with moving parts, and is easily assembled.
The solution effectively prevents crack formation and contact issues while improving thermal protection and assembly ease, enhancing the turbomachine's performance and reliability.
Abstract
Description
Description Title of the invention: Improving sealing in a turbine of turbomachine
[0001] GENERAL TECHNICAL FIELD
[0002] = The field of the invention is that of turbomachines. More precisely, the invention relates to a sealing assembly for a turbomachine turbine, as well as a tur- machine comprising such a set. STATE OF THE ART
[0003] A turbomachine, in particular a double-spool turbomachine, comprises class- ically, from upstream to downstream depending on the direction of flow circulation in the tur- bomachine, a blower, a low pressure compressor, a high pressure compressor pressure, a combustion chamber, a high pressure turbine and a low pressure turbine pressure.
[0004] — The low pressure turbine makes it possible to exploit and release the power generated in the combustion chamber.
[0005] — Ace title, the sealing of the vein delimiting the flow crossing the low turbine pressure must be ensured in order to guarantee a high level of performance of the tur- bomachine. It is therefore necessary to avoid leaks from the vein to the organs making up the low pressure turbine housing.
[0006] [Fig. 1] illustrates a turbine 1 for a turbomachine of known type.
[0007] Such a turbine comprises several successive stages each comprising a blade fixed 2 and a blade 3 rotating around an axis X of rotation (and longitudinal of the tur- bomachine).
[0008] — By convention, in the present application, the terms "upstream" AM and "downstream" AV are defined in relation to the direction of air circulation in the turbine, i.e. the left to right in [Fig.1]. Similarly, by convention in this request, the terms "interior" and "exterior", and "internal" and "external" are defined radially relative to the X axis of the turbomachine. Finally, the term "circumferential » is used in relation to any annular part or sector of an annular part for designate an orientation, a direction or even a dimension considered in reference to the circumference of that part or sector.
[0009] = Each fixed blade 2 comprises a radially internal annular platform 21 and a radially outer annular platform 22.
[0010] = The fixed blade 2 is attached radially outwards to an external casing 4 of the turbine.
[0011] = The blades 3 rotate inside an annular structure or sectored ring 5 attached to the external casing 4. This ring 5 is advantageously formed of several ring sectors 50 to overcome expansion problems of the assembly. These ring sectors 50 which extend circumferentially in an arc of a circle are arranged circumferentially end to end. The ring sectors 50 each internally carry a block of abradable material 51. These blocks of abradable material are capable of cooperating by friction with annular wipers 32 arranged at the radially external periphery of each blade 3 of the rotor. As visible in detail in [Fig.2], the ring 5 comprises a main body 52 which extends radially inwards to define a first substantially radial branch 53, the radially internal end of this first branch 53 extending axially upstream by a second branch 54. At the circumferential ends of the ring 5, slot-shaped housings 56 are provided into which tabs L are inserted. More precisely, the tabs L are partly mounted in housings 56 formed in the ring 5. In the case of several, such an assembly helps to ensure sealing between sectors. In the area of connection of the body 52 to the first branch 53, the ring 5 comprises at least one appendage directed downstream which forms a hook 57, for its attachment to the casing 4 in which a reservation 40 is provided for this purpose. Upstream of these two parts, there is an annular ferrule 6 which is used for positioning the casing and more generally for that of the high pressure turbine in relation to the low pressure turbine, in order to ensure geometric continuity of the primary vein of the machine. This ferrule 6 has a through opening 61 which has the function of directing air coming from the upstream compressor to cool the casing 4, mainly in the region of the hook 57. A member 7 forming a seal is inserted between the ferrule 6 and the first branch 53 of the sector 50 and contributes to thermally protecting the region of the hook 57. As shown in [Fig.2], the ferrule 6 extends radially inwards well below the second branch 54 of the sector 50. This configuration exposes the radially internal part 60 of the shell 6, and more particularly its face 62 facing downstream, to the hot air of the vein V. Furthermore, by construction, there is a significant space at the level of the first stage of the low pressure turbine and the first blade of the low pressure turbine, which makes the shell 6 vulnerable to a potential reintroduction of vein air, symbolized by the arrow R, via the space E separating the shell 6 from the second branch 54. In any case, unless a piece is introduced to form a barrier to this reinstatement, introduction of vein air, the shell 6 is subjected to high temperatures and significant radiation, as symbolized by the undulations S in [Fig.2]. This potentially exposes oneself to the formation of cracks, which is not desirable. One solution to resolve this problem consists of adding to the radially internal part 60 of the ferrule, a part (not shown here) forming a barrier. In practice, this part is welded to the ferrule 6. But again, there is a risk of cracks forming, particularly due to the different nature of the materials of the ferrule and the part forming the wall, which causes different expansion coefficients. It is therefore impossible to avoid the stresses leading to these cracks. Another solution, as illustrated in [Fig. 3], consists of extending the second branch 54 of the sector 50 by a third radially internal branch 55 thus forming a single-piece deflector which ensures the aforementioned function of a bulwark part. However, due to the need to place a tab L there, this branch necessarily has a negligible thickness, so that the spacing e between the ferrule 6 and the upstream face of this branch 55, taking into account the assembly tolerances, is relatively high. However, a well-known phenomenon in this area of the turbine is that the blade 3 is subjected to significant axial displacement, so that the wipers 32 risk coming into contact with the branch 55, which must absolutely be avoided. PRESENTATION OF THE INVENTION The aim of the invention is to propose a solution for thermally protecting structural elements while avoiding the problems of crack formation explained above, and without the risk of contact with moving elements. To this end, the invention relates, according to a first aspect, to a sealing assembly for a low-pressure turbine casing of a turbomachine, the sealing assembly comprising: - an annular structure extending around a longitudinal axis and going from upstream to downstream, the annular structure comprising an upstream end extending radially towards the inside of the structure to define a first branch from which a second branch extends axially towards the upstream, - a ferrule comprising a face arranged opposite and at a distance from the first and second branches of the annular structure, the sealing assembly comprising an annular heat deflector disposed between the annular structure and the shell, the heat deflector comprising a first axial wall resting on an external surface of the second branch, a second radial wall extending from a downstream end of the first wall along the first branch, a third radial wall extending from an upstream end of the first wall inwardly so as to be opposite and spaced from the face. According to other advantageous and non-limiting characteristics of the invention, taken alone or according to a technically compatible combination of at least two of them: - the thermal deflector comprises a fourth axial wall which extends upstream from the second wall, parallel to and opposite the first wall; - the assembly comprises an elastic member arranged between the ferrule and the deflector, and extending from the face so as to press the thermal deflector against the first and second branches of the first structural element; - the elastic member is a seal; - the organ extends at least partly between the first and fourth walls; - the annular structure comprises several annular sectors which extend circumferentially around the longitudinal axis, the sectors being adjacent; - the annular thermal deflector is formed of several sectors arranged circumferentially around the longitudinal axis, the sectors of the deflector being adjacent; - the circumferential dimension of a heat deflector sector is equal to that of an annular sector, or is substantially equal to a multiple of that of an annular sector; - one end of the third wall of each deflector sector comprises in the circumferential direction a tab forming a male member, while the opposite end comprises a tab forming a complementary female member; - at least one sealing tab is mounted partly in a housing of a circumferential edge of an annular sector and for the other part, in a housing of a circumferential edge of an adjacent annular sector located opposite; - each annular sector has a hook suitable for being fixed to a casing; - each deflector sector comprises a pair of legs positioned on either side of said hook, to immobilize said deflector sector circumferentially; - the annular structure is arranged at the inlet of a low pressure turbine. The invention relates, according to a second aspect, to a turbomachine assembly comprising a low pressure turbine, the low pressure turbine comprising a fixed external casing connected to an upstream shroud, the turbomachine assembly comprising a sealing assembly according to the first aspect of the invention. The invention relates, according to a third aspect, to a turbomachine comprising a turbomachine assembly according to the second aspect of the invention. The invention relates, according to a fourth aspect, to an aircraft comprising a turbomachine according to the third aspect of the invention. The advantages of the invention are multiple. There is no need to fix the heat deflector to the first structural element, so potential cracking problems associated with different expansion coefficients are completely avoided. In addition, the ease of assembly is improved. Furthermore, the thickness of this profile-shaped deflector can be significantly reduced, in any case compared to the solution illustrated in [Fig. 3], so that any potential contact between the defector and other elements is eliminated. PRESENTATION OF THE FIGURES Other characteristics and advantages of the invention will appear from the description which will now be given, with reference to the appended drawings, which represent, for informational but non-limiting purposes, different possible embodiments. On these drawings: - [Fig. 1] is a sectional view of a low-pressure turbine according to the state of the art; - [Fig.2] is a detailed view of part of the turbine of [Fig.1]; - [Fig.3] is a view similar to [Fig.2], according to a different embodiment; - [Fig.4] is also a view similar to the two previous figures, integrating the sealing assembly according to the invention: - [Fig.5] is a detail of [Fig.4], intended to show more particularly the particular shape of a deflector of the sealing assembly; - [Fig.6] is a detailed view showing more particularly one end of the aforementioned deflector; - [Fig.7] is a perspective view of a sealing ring sector according to an embodiment of the invention; - [Fig.8] is a detail view intended to show how a hook secured to a ring sector cooperates with the aforementioned deflector; - [Fig.9] is a perspective view of two adjacent ring sectors, which cooperate with a single deflector. Throughout the figures, identical elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION Figures 4 to 9 illustrate a sealing assembly according to one embodiment. It is noted that the elements which are identical to those of the low pressure turbine previously described in relation to Figures 1 and 2 will not be described again. The sealing assembly according to the invention is essentially distinguished from that which has been described with reference to [Fig.2] or 3 by the fact that it comprises an annular thermal deflector D of the sheet metal type. As can be seen in particular in [Fig.5], the thermal deflector D comprises a first wall 80 directed axially. This first wall 80 extends at its downstream end by a second wall 81 directed radially outwards, and at its upstream end by a third wall 82 directed radially inwards. As can be seen in particular in [Fig. 4], a ring 5 extends around a longitudinal axis and extends upstream radially inwards to define a first substantially radial branch 53 and the radially internal end of this first branch 53 extending axially upstream by a second branch 54. The second branch 54 has an external circumferential face 540. Furthermore, an annular ferrule 6 comprises a portion 60 which extends radially inwards well below the second branch 54 of the ring 5 comprising a face 62 arranged opposite and at a distance from the first and second branches 53, 54 of the first structural element 5. This configuration exposes the radially internal portion 60, and more particularly the portion of its face 62 oriented downstream which extends inwards well below the second branch 54, to the hot air of the vein V. And as shown more particularly in [Fig. 4], the first and second walls 80 and 81 of the annular thermal deflector D are dimensioned to come into contact with and cover on the one hand the face 540 of the second branch 54 of the ring 5 and, on the other hand, the first branch 53. And the third wall 82 extends, for its part, opposite the face 62 of the ferrule 6, in order to materialize a thermal protection rampart of this face. Advantageously, the installation of the annular thermal deflector D does not require any welding or other means of connection to the first structural element 5. In fact, it rests by its wall 80 against the second branch 54. According to one embodiment, the annular thermal deflector D is axially blocked by a member 7 which, as presented in the introduction, preferably consists of a seal, this elastic member pressing the wall 80 against the first branch 53 of the first structural element 5. The member 7 can optionally be an Omega type seal. As can be seen in the figures, the annular thermal deflector D comprises a fourth wall 83, which extends in the extension of the second wall 81, parallel and opposite the first wall 80. This fourth wall 83 contributes to centering the member 7 and to protecting it thermally. According to a possible embodiment, the ring 5 is formed from several ring sectors 50 in order to solve the expansion problems of the assembly. These ring sectors 50 extend circumferentially in an arc of a circle, and are arranged circumferentially end to end. According to one embodiment, at the circumferential ends of the ring sectors 50, slot-shaped housings 56 are provided into which tabs L can be inserted. More precisely, the tabs would be mounted partly in the housings 56 of a sector 50 and partly in the housings of an adjacent sector. This assembly helps to ensure sealing between sectors. In the same way as for the ring 5, the deflector D can be made up of several identical sectors 8 arranged adjacently in the circumferential direction. According to one embodiment, the length, that is to say the circumferential dimension of a sector 8 is substantially equal to that of a ring sector 50. Alternatively, this length is substantially equal to a multiple of that of a ring sector 50. Thus, as illustrated in [Fig.9], the sector 8 has a length such that it covers two adjacent sectors 50. As is particularly visible in [Fig. 6], and according to a possible embodiment, one end of the third wall 82 of the sector 8 of the annular thermal deflector D comprises, in the circumferential direction, a tab 820 which forms a male member, while the opposite end of this wall (not visible in the figure), comprises a tab forming a complementary female member. In this way, when two sectors are positioned in continuity with each other, the male members of one and the female members of the other overlap. As mentioned previously, each sector 50 comprises at least one hook-shaped appendage 57 suitable for its attachment to the casing 4. According to an advantageous embodiment of the present invention, a single appendage 57 is provided on each sector. This helps to eliminate its hyperstaticity, while improving its assembly and manufacturability. Furthermore, sector 8 is provided with locking means which allow it to be blocked circumferentially relative to ring sector 50 via appendage 57. These locking means are particularly visible in [Fig. 8]. These are two tangential stop tabs 810 which are integral with the wall 81 and whose spacing is equal, apart from the clearance, to the length, that is to say the circumferential dimension of the appendage 57. In the embodiment presented in which the sector comprises a fourth wall 83 ([Fig.8]), the latter is interrupted locally to allow the passage of said legs 810.
Claims
Claims
1. Sealing assembly for a low pressure turbine (1) casing (4) turbomachine, the sealing assembly comprising: - an annular structure {5) extending around a longitudinal axis (X) and going from upstream to downstream, the annular structure (5) comprising an upstream end extending radially inward of the structure (5) to define a first branch (53) from which extends axially upstream a second branch (54), - a ferrule (6) comprising a face (62) arranged opposite and at a distance first and second branches (53, 54) of the annular structure (5), the sealing assembly comprising a thermal deflector (D) annular arranged between the annular structure (5) and the ferrule (6), the de- thermal deflector (D) comprising a first axial wall (80) resting on an external surface (540) of the second branch (54), a second radial wall (81) extending from a downstream end of the first wall (80) along the first branch (53), a third radial wall (82) extending from an upstream end of the first wall (80) inward so as to be opposite and at a distance from the face (62).
2. A sealing assembly according to claim 1, wherein the deflector thermal (D) comprises a fourth axial wall (83) which extends upstream from the second wall (81), parallel and opposite the first wall (80).
3. A sealing assembly according to any one of claims 1 to 2, comprising an elastic member (7) arranged between the ferrule (6) and the de- deflector, and extending from the face (62) so as to press the de- thermal deflector (D) against the first and second branches of the first structural element (5).
4. An assembly according to claim 3, wherein the elastic member (7) is a seal.
5. A sealing assembly according to claim 4 in combination with the claim 2, wherein the member (7) extends at least partly between the first (80) and fourth walls (83).
6. A sealing assembly according to one of claims 1 to 5, wherein the annular structure (5) comprises several annular sectors (50) which extend circumferentially around the longitudinal axis, the sectors (50) being adjacent.
7. Sealing assembly according to one of claims 1 to 6, in which the annular thermal deflector (D) is formed of several sectors (8) arranged circumferentially around the longitudinal axis, the sectors {8) of the deflector being adjacent.
8. A sealing assembly according to claim 7, wherein the circumferential dimension of a sector (8) of thermal deflector (D) is equal to that of an annular sector (50), or is substantially equal to a multiple of that of an annular sector (50).
9. A sealing assembly according to one of claims 7 to 8, wherein one end of the third wall (82) of each sector (8) of de- deflector (D) comprises in the circumferential direction a tab (820) forming a male organ, while the opposite end has a leg forming a complementary female organ.
10. A sealing assembly according to one of claims 6 to 9, wherein at least one sealing tab (L) is partly mounted in a housing (56) of a circumferential edge of an annular sector (50) and for the other part, in a housing of a circumferential edge of a adjacent annular sector (50) located opposite.
11. A sealing assembly according to one of claims 6 to 10, wherein each annular sector (50) has a hook (57) adapted to be fixed to a casing (4).
12. A sealing assembly according to one of claims 7 to 11, wherein in that each sector (8) of deflector (D) comprises a pair of legs (810) positioned on either side of said hook (57), to im- mobilizing said deflector sector (8) circumferentially.
13. Turbomachine assembly comprising a low pressure turbine, the low pressure turbine comprising an external casing (4) fixed in connection with an upstream shell (6), the turbomachine assembly comprising a sealing assembly according to one of claims 1 to 12 arranged in downstream of the ferrule (6).
14. An assembly according to claim 13, wherein the annular structure is located at the inlet of the low pressure turbine.
15. Turbomachine comprising a turbomachine assembly according to one of of claims 13 to 14.