Anti-injury sealing box for movable blade stilt for turbojet engine

Abstract

Anti-injury sealing box for a moving blade stilt for a turbojet engine The sealing box (1) is intended to be positioned between the roots (13) of two adjacent moving blades (3) within the same rotor stage of a turbojet engine extending longitudinally along an axis (X), each moving blade comprising a platform (4) equipped with a stilt (2) extending radially towards the axis (X). It has: a closed upper face (8) in contact with a lower face (14) of at least one platform (4), sides (10) extending the upper face (8) downwards and ending with a free edge (15) which delimits an opening (9) in the lower part of the sealing box, a first side (10, 10a) in contact with a first stilt (2, 2a), and a second side (10, 10b) located opposite the first side (10, 10a), where, at its free edge (15), the first side (10, 10a) has a curved part (16, 16a) towards the inside of the sealing box.Figure to be published with the abstract: Figure 18.

Description

Title of the invention: Anti-injury sealing box for a moving blade stilt for a turbojet engine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of sealing boxes intended to be housed between the stilts of two moving blades of a turbojet in order to prevent the circulation of air between the platforms of said moving blades.

[0002] The present invention relates to a new sealing box designed not to damage the moving blades against which it rests. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A conventional sealing box 1' is shown in perspective in [Fig.l] and in [Fig.2], where it is shown positioned against Péchasse 2 of a moving blade 3 of a turbojet engine. On the outer side relative to the longitudinal axis X along which the turbojet engine extends, Péchasse 2 has a platform 4 equipped with a blade 5, while on the inner side, Péchasse 2 ends with a bulb 6, serving as a fixing base on a rotor disk 7. On the outer side, the sealing box 1' has a substantially flat upper face 8' provided to close the space located between the platforms 4 of two neighboring moving blades 3. Thus, a sealing box 1' is provided on each side of Péchasse 2 of a moving blade 3, between the bulb 6 and the platform 4.

[0004] A sealing box 1' is a hollow part, usually made of preformed sheet metal, the external shape of which is designed to substantially match that of the stilts 2 against which it rests. While the upper face 8' of a sealing box 1' is closed, its lower part usually has an opening 9' delimited by sides 10'. In use, the opening 9' of a sealing box 1' is open in the direction of the longitudinal axis X, while its upper face 8' is located on the side opposite this axis.

[0005] At the opening 9', the sides 10' of a sealing box 1' are bordered by an external edge 11' and by an internal edge 12'. In use, a part of the external edge 11' is in contact with a stilt 2 of a moving blade 3 and it has been observed that this contact sometimes damages said stilt 2 on the surface, generating grooves which can be designated as indications.

[0006] These injuries are not desirable because they cause premature aging of the stilts 2. They require maintenance operations, which result in particular in equipment downtime and additional costs.

[0007] There is therefore a need for a sealing box which does not injure Péchasse of a moving blade against which it is in contact. Summary of the invention

[0008] To address this problem, the applicant has carried out numerous preliminary research aimed at understanding the exact origin of these injuries. Indeed, when a conventional sealing box 1' is in place (see [Fig.5], [Fig.6] and [Fig.7]), the external edge 11' is not in contact with a stilt 2' so as to injure it. During assembly, the contact of the side 10' of the box 1' against a face of the stilt 2' is of the plane / plane type.

[0009] It has been discovered that in use, under the effect of centrifugal force, the box 1' pivots slightly and the contact of the side 10' of the box against a face of the stilt 2' becomes linear, so that the external edge 11' is in contact with said stilt 2' so as to damage it (see [Fig.8], [Fig.9] and [Fig. 10]).

[0010] The invention provides a solution to the injury risk problems discussed above by providing a dropped edge at least along the edges of the sealing box which are likely to come into contact with a stilt. The sealing box according to the invention is intended to replace the conventional sealing box of the prior art without it being necessary to modify any part of the moving blades between which it is used.

[0011] One aspect of the invention relates to a sealing assembly for two adjacent moving blades within the same rotor stage of a turbojet engine, said turbojet engine extending longitudinally along an axis X, the sealing assembly comprising: • a first foot of a first mobile blade, comprising a first platform equipped with a first stilt extending radially towards the X axis; • a second foot of a second mobile blade comprising a second platform equipped with a second stilt extending radially towards the X axis, the second platform being located opposite and in the extension of the first platform; and • a sealing box located between the first and second legs and having: • a closed upper face in contact with a lower face of at least one platform among the first and second platforms, • sides extending the upper face downwards and ending in a free edge which delimits an opening in the lower part of the sealing box, a first side being in contact with the first stilt, and a second side being located opposite the first side; and in which • at its free edge, the first side has a part curved towards the inside of the sealing box.

[0012] Advantageously, the curved portion provides a contact zone between the sealing box and a stilt which is not likely to injure said stilt, whether the sealing box is pressed parallel against this stilt (see [Fig. 13] and [Fig. 14]) or whether it is slightly pivoted under the effect of centrifugal force (see [Fig. 15] and [Fig. 16]).

[0013] According to one aspect of the invention, the first side has a substantially flat portion located between its curved portion and the closed upper face. This flat portion advantageously provides a large support surface for wedging the sealing box against Péchasse without damaging it.

[0014] According to another aspect of the invention, the substantially flat part of the first side is parallel to a face of the first stilt located opposite, which advantageously makes it possible to take advantage of the large support surface so as not to injure the stilt.

[0015] According to an additional aspect of the invention, at its free edge, the second flank also has a portion curved towards the inside of the sealing box, which advantageously makes it possible to avoid injuring the second stilt if the sealing box comes into contact against it.

[0016] According to one aspect of the invention, at their free edge, all the sides have a part curved towards the inside of the sealing box, which advantageously makes it possible to avoid injuring one or other of the stilts, whether the sealing box is pivoted or not.

[0017] According to another aspect of the invention, the second side has a substantially flat part which is parallel to a face of the second stilt located opposite, which advantageously makes it possible to benefit from a large support surface so as not to damage the second stilt.

[0018] According to a further aspect of the invention, an external face of at least one curved portion is coated with a layer of elastomer.

[0019] According to one aspect of the invention, an external face of all the curved parts is coated with a layer of elastomer.

[0020] This elastomer coating advantageously provides protection against friction and wear.

[0021] According to another aspect of the invention, an elastomer layer has an average thickness of between 0.1 and 5 mm, preferably between 0.2 and 2 mm, more preferably between 0.3 and 1 mm. The thinness of this layer makes it possible in particular not to significantly modify the external shape of the sealing box.

[0022] According to a further aspect of the invention, the sealing box has a average thickness of 0.5 ± 0.05 mm.

[0023] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0024] The figures are presented for information purposes only and in no way limit the invention.

[0025] [Fig.l] is a perspective view from below of a sealing box according to the prior art.

[0026] [Fig.2] is a perspective view from below of a sealing box according to the art front positioned against Péchasse and under a platform of a mobile blade represented in broken lines.

[0027] [Fig.3] is a perspective view from above of two sealing boxes according to the art anterior positioned against the two sides of a stilt of a moving blade represented in broken lines.

[0028] [Fig.4] is a radial sectional view of a sealing box according to the prior art positioned between two moving blades.

[0029] [Fig.5] is a detail view of the part circled in [Fig.4].

[0030] [Fig.6] is a view similar to [Fig.4] where the sealing box is pivoted under the effect of centrifugal force.

[0031] [Fig.7] is a detail view of the part circled in [Fig.6].

[0032] [Fig.8] is a perspective view from below of an example of a sealing box according to the invention.

[0033] [Fig.9] is a sectional view along the radial plane shown in broken lines on [Fig.8] of the framed part on [Fig.8].

[0034] [Fig. 10] is a perspective view from below of an example of a sealing box according to the invention, all of whose curved parts are coated with a layer of elastomer.

[0035] [Fig.11] is a detail view of the part framed in [Fig.10].

[0036] [Fig. 12] is a sectional view along the radial plane shown in broken lines on [Fig.l 1] of the framed part on [Fig.10].

[0037] [Fig. 13] is a radial sectional view of an example of a sealing box according to the invention positioned between two moving blades.

[0038] [Fig.14] is a detail view of the part circled in [Fig.13].

[0039] [Fig. 15] is a view similar to [Fig. 13] where the sealing box is pivoted under the effect of centrifugal force.

[0040] [Fig. 16] is a detail view of the part circled in [Fig. 15].

[0041] [Fig. 17] is a view similar to [Fig. 13] where the sealing box has sides opposite parallel to the stilts between which it is positioned, one of the sides being in leaning against one of the stilts.

[0042] [Fig. 18] is a view similar to [Fig. 17] where the two sides are each resting against one of the stilts.

[0043] [Fig. 19] is a detail view of the part circled in [Fig. 18].

[0044] [Fig.20] is a detail view of the part circled in [Fig. 18]. DETAILED DESCRIPTION

[0045] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0046] By convention, in the present application, the terms "upper" and "lower", and "top" and "bottom" refer to the elements as shown in the figures, it being understood that this arrangement will not necessarily be retained in use. These terms are defined radially relative to the longitudinal axis of the turbojet engine. Thus, a cylindrical part extending along the axis of the turbojet engine has a lower face facing the longitudinal axis X of the turbojet engine and an upper surface, opposite its inner surface. Similarly, the lower or bottom part of a part is a part located on the inner side relative to the longitudinal axis X along which the turbojet engine extends and therefore in the direction of this axis, while the upper or top part of a part is a part located on the outer side relative to the longitudinal axis X and therefore away from this axis.Finally, by "external" or "internal" face of a part of the sealing box, we mean a face oriented respectively towards the outside or towards the inside of said box.

[0047] The sealing box 1 according to the invention is designed to be positioned between the stilts 2 of two neighboring moving blades 3 within the same rotor stage of a turbojet, said turbojet extending longitudinally along an axis X.

[0048] Conventionally, each moving blade 3 comprises at least one platform 4 equipped with a blade 5 extending radially outwards relative to the axis X and a bulb 6 extending radially inwards relative to the axis X, a stilt 2 connecting the platform 4 to the bulb 6. The stilt 2 and the bulb 6 form the root 13 of a moving blade 3.

[0049] The sealing assembly according to the invention is provided to limit the circulation of air between two neighboring moving blades 3, 3a, 3b within the same rotor stage of a turbojet.

[0050] This sealing assembly includes: • a first foot 13a of a first mobile blade 3a, comprising a first platform 4a equipped with a first stilt 2a extending radially towards the axis X; • a second foot 13b of a second mobile blade 3b comprising a second platform 4b equipped with a second stilt 2b extending radially towards the X axis, the second platform 4b being located opposite and in the extension of the first platform 4a; and • a sealing box 1 according to the invention, designed to be positioned between the first and second feet 13a, 13b.

[0051] Conventionally, the sealing box 1 according to the invention has a closed upper face 8, designed to be positioned in contact with a lower face 14, 14a, 14b of at least one platform 4 among the first and second platforms 4a, 4b. It also has sides 10, extending the upper face 8 downwards and ending with a free edge 15 which delimits an opening 9 in the lower part of the sealing box 1, a first side 10a being in contact with the first stilt 2a, and a second side 10b being located opposite the first side 10a. This second side 10b may be in contact with the second stilt 2b or be at a distance from it.

[0052] The sealing box 1 is for example made of metal, preferably stainless steel and more preferably Z10CNT18 steel. In its upper face 8 and its sides 10, it has for example an average thickness E of the order of half a millimeter, preferably 0.5 ± 0.05 mm. By average thickness of the walls 8, 10 of the sealing box 1 is meant the average between the minimum and maximum thicknesses of said walls 8, 10. This thickness can be greater to adapt to all engine scales and meet the mechanical resistance.

[0053] As shown in [Fig.8] to [Fig.20], the sealing box 1 according to the invention is characterized in that, at its free edge 15, at least the first flank 10a has a curved portion 16, 16a towards the inside of the sealing box 1.

[0054] The free edge 15 comprises an outer edge 11, located on the outer side of the sealing box 1, and an inner edge 12 located on the inner side. Due to the curvature of the free edge 15, the outer edge 11 cannot come into contact with a stilt 2, even when the sealing box 1 is pivoted under the effect of centrifugal force.

[0055] According to a variant of the invention, the second flank 10b may also have a curved portion 16, 16b towards the inside of the sealing box 1 at its free edge 15.

[0056] According to another variant of the invention shown in [Fig.8] to [Fig.20], all the sides 10, 10a, 10b of the sealing box 1 may have a curved part 16, 16a, 16b towards the inside of the sealing box 1 at their free edge 15.

[0057] According to a variant of the invention, an external face 17 of at least one curved part 16 is coated with a layer of elastomer 18.

[0058] According to another variant of the invention, an external face 17 of all the parts curved 16, 16a, 16b is coated with a layer of elastomer 18.

[0059] According to a preferred variant of the invention shown in [Fig.10] to [Fig.12], all of the curved parts 16, 16a, 16b are coated with a layer of elastomer 18, both on their external face 17 and on their internal face 19.

[0060] This elastomer layer 18 is for example deposited by dipping the curved parts 16, 16a, 16b of the sealing box 1 in a bath of liquid elastomer and then solidifying the elastomer layer 18 thus deposited. According to a preferred embodiment of the invention, the addition of the elastomer layer 18 is carried out by dipping and polymerization in the open air, such as according to the process known as RTV (Room Temperature Vulcanization).

[0061] The elastomer layer 18 is preferably designed to withstand a temperature between 205°C and 315°C.

[0062] The elastomer layer 18 has, for example, an average thickness e of the order of half a millimeter. The average thickness e is preferably between 0.1 and 5 mm, preferably between 0.2 and 2 mm, more preferably between 0.3 and 1 mm. By average thickness of the elastomer layer 18 is meant the average between the minimum and maximum thicknesses of said elastomer layer 18.

[0063] According to an example of the invention, the first flank 10a has a substantially flat part 20a located between its curved part 16a and the closed upper face 8. This substantially flat part 20a is preferably parallel to the face 21a of the first stilt 2a against which the first flank 10a comes to bear.

[0064] Similarly, the second flank 10b may have a substantially flat part 20b located between its curved part 16b and the closed upper face 8. This substantially flat part 20b is preferably parallel to the face 21b of the second stilt 2b (see [Fig. 17] to [Fig. 20]).

[0065] Each substantially flat part 20a, 20b can constitute a contact part bearing against a stilt 2a, 2b. Its flatness allows better wedging of the sealing box 1 against said stilt 2a, 2b and prevents any damage to the latter.

[0066] According to another variant of the invention illustrated in [Fig.13] to [Fig.16], the substantially flat part 20a of the first flank 10a and the substantially flat part 20b of the second flank 10b may be parallel to each other.

[0067] According to an example of the invention illustrated in [Fig.13] to [Fig.17], the sealing box 1 can be mounted so that only the first flank 10a bears against the first stilt 2a, while the second flank 10b is at a distance D from the second stilt 2b.

[0068] According to another example of the invention illustrated in [Fig. 18] to [Fig.20], the box sealing 1 can be mounted so that both the first and second flanks 10a, 10b bear against Péchasse 2a, 2b located opposite said flanks 10a, 10b.

[0069] The curved parts 16, 16a, 16b are for example obtained by folding the sheet metal of the sealing box 1 on a die. Other means can also be envisaged, in particular by folding without a die, or by welding then grinding.

[0070] Although in the figures the various edges 11, 12 appear sharp, they are preferably rounded as a safety measure for the assembly operators.

[0071] Although described through a certain number of examples, variants and embodiments, the sealing box and the sealing assembly according to the invention include various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

Claims

1. Sealing assembly for two adjacent moving blades (3, 3a, 3b) within the same rotor stage of a turbojet engine, said turbojet engine extending longitudinally along an axis (X), the sealing assembly comprising: - a first foot (13, 13a) of a first moving blade (3, 3a), comprising a first platform (4, 4a) equipped with a first stilt (2, 2a) extending radially towards the axis (X); - a second foot (13, 13b) of a second moving blade (3, 3b) comprising a second platform (4, 4b) equipped with a second stilt (2, 2b) extending radially towards the axis (X), the second platform (4, 4b) being located opposite and in the extension of the first platform (4, 4a); and - a sealing box (1) located between the first and second feet (13, 13a, 13b) and having: • a closed upper face (8) in contact with a lower face (14, 14a, 14b) of at least one platform (4) among the first and second platforms (4a, 4b), • flanks (10, 10a, 10b) extending the upper face (8) downwards and ending in a free edge (15) which delimits an opening (9) in the lower part of the sealing box (1), a first flank (10, 10a) being in contact with the first stilt (2, 2a), and a second flank (10, 10b) being located opposite the first flank (10, 10a); and characterized in that - at its free edge (15), the first flank (10, 10a) has a curved part (16, 16a) towards the inside of the sealing box (1).

2.

3. Sealing assembly according to claim 1, characterized in that the first flank (10, 10a) has a substantially flat part (20, 20a) located between its curved part (16, 16a) and the closed upper face (8). Sealing assembly according to claim 2, characterized in that the substantially flat part (20, 20a) of the first flank (10, 10a) is parallel to a face (21a) of the first stilt (2, 2a) located opposite.

4. Sealing assembly according to any one of the preceding claims, characterized in that at its free edge (15), the second flank (10, 10b) also has a curved portion (16, 16b) towards the inside of the sealing box (1).

5. Sealing assembly according to any one of the preceding claims, characterized in that at their free edge (15), all the flanks (10, 10a, 10b) have a curved part (16, 16a, 16b) towards the inside of the sealing box (1).

6. Sealing assembly according to any one of the preceding claims, characterized in that the second flank (10, 10b) has a substantially flat part (20, 20b) which is parallel to a face (21b) of the second stilt (2, 2b) located opposite.

7. Sealing assembly according to any one of the preceding claims, characterized in that an external face (17) of at least one curved part (16, 16a, 16b) is coated with a layer of elastomer (18).

8. Sealing assembly according to any one of the preceding claims, characterized in that an external face (17) of all the curved parts (16, 16a, 16b) is coated with a layer of elastomer (18).

9. Sealing assembly according to any one of claims 7 and 8, characterized in that a layer of elastomer (18) has an average thickness of between 0.1 and 5 mm, preferably between 0.2 and 2 mm, more preferably between 0.3 and 1 mm.

10. Sealing assembly according to any one of the preceding claims, characterized in that the sealing box (1) has an average thickness of 0.5 ± 0.05 mm.

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