EP3724454A1

EP3724454A1 - Multi-blade vane for a turbomachine rotor and rotor comprising same

Info

Publication number: EP3724454A1
Application number: EP18829759.2A
Authority: EP
Inventors: Arnaud Nicolas NEGRI
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2017-12-13
Filing date: 2018-12-12
Publication date: 2020-10-21
Anticipated expiration: 2038-12-12
Also published as: FR3074839A1; WO2019115578A1; US11156108B2; FR3074839B1; CN111448366A; US20200392855A1; EP3724454B1; CN111448366B

Abstract

The invention relates to a vane (1) for a turbomachine rotor comprising a first blade (2) and a second blade (3) arranged to form two successive blades for a bladed rotor, a platform (4) substantially forming an angular wall sector in an axial direction (X), the two blades (2, 3) being connected to the platform (4) by one of the ends thereof extending substantially in a direction referred to as radial (R) which is substantially perpendicular to the axial direction (X), and attachment means connected to the platform (4) which are designed to cooperate with fastening means on a disk (6) of the rotor, characterised in that the attachment means comprise two individual supports (12, 13), each support extending from the platform (4), in the radial direction (R), in the extension of one of the two blades (2, 3), and bearing an attachment member (16, 17) at an end opposite the platform (4), the attachment member extending substantially parallel to the axial direction (X) and having at least one surface (S1, S2) facing the platform (4) with a constant cross-sectional profile perpendicular to the axial direction (X), so as to form a bearing surface for retaining the vane (1) in the radial direction (R) oriented from the platform to the blades (2, 3). The invention further relates to the rotor comprising the vane.

Description

TURBOMACHINE ROTOR MULTIPAL ROTOR AND ROTOR LA

UNDERSTANDING

Technical area :

The present invention relates to the field of paddle rotors in turbomachines, more particularly the case where the blades are made individually and fixed on a disk to form the paddle rotor.

State of the art :

In particular, a low pressure turbine rotor is generally composed of several tens or hundreds of vanes mounted on a disk. Each blade is composed of at least one blade, a clip to fit in the disk of the rotor and a platform, placed between the two, so as to form the inner face of the vein in which passes the flow of gas crossed by the blades.

Such a rotor can be heavily loaded by a very high rotational speed. The maintenance of the blades on the rotors and the sealing against the flow of gas at the platforms are part of the problems to be solved in the design of these rotors and their blades.

There are several advantages to providing several blades on the same blade. Firstly, producing several blades on the same part makes it possible to reduce the production costs of the complete rotor. In addition, between each blade, games are needed for mounting and to avoid contact during thermal expansion. These games cause leaks between the vein and the out-vein, harmful for the performance of the turbomachine.

It is thus known to use two-blade vanes, as is presented in EP-B1 -1447525 where the concept is adapted to adjust the resonant frequencies of the blades.

With reference to FIG. 1, a two-blade blade 100 according to the state of the art comprises two blades 101, 102 extending in span along a radial direction R between an internal platform 103 and an external platform 104 delimiting the vein of passage of the gas flow. The inner platform 103 also connects the blades 101, 102, and a monoblock foot 105 which fits between the teeth 106 of a rotor disc. 107 (shown only in the vicinity of the dawn). The dovetail-shaped fastener comprises a bulb 107 placed at the end of a stilt 108 in two parts, each of the two parts joining the base of a blade. The manufacture of the blade being made by casting, not to have a solid zone between the two parts of the stilt 108, a cavity 109 is formed between the two parts of the stilt 108 using a core used during the foundry process.

The attachment foot 105 is substantially centered in the circumferential direction T between the two blades 101, 102, so as to balance the stresses to retain the blades under the centrifugal forces. We see in Figure 1, that it requires the two parts of the stilt 108 to have a non-radial part to reach the base of the blades. The arrows in FIG. 1 schematically show the path of the stresses due to the centrifugal forces, along the stilt 108 and the blades 101, 102. In the part where the arrows are not aligned with the radial direction R this creates a moment in the stilt and therefore supplements constraints.

From a dimensioning point of view, the attachment foot 105 must hold two blades instead of one, withstanding additional constraints due to the offset of the foot 105 relative to the blades. In addition, the foot 105 being traversed by the core 109, it must be even wider than the double of a single foot to hold a single blade.

Another known solution would be to have two separate attachment feet under each blade, but the mounting would be highly hyperstatic. Indeed, in the state of the art, the dawn and the disc are already hyperstatic in operation, because there are two contact planes. If you put two normal fasteners, there will be four contact plans, so many more problems of hyperstatism.

Moreover, there is a need to minimize the mass of the blades, to reduce the constraints on the links with the disk as well as for the overall mass balance.

The object of the invention is to propose a solution for minimizing the mass of the attachment of a two-blade blade, in particular by reducing the level of the stresses to which the fastening of the blades must withstand during the operation of the rotor.

The invention also aims to avoid too much hyperstatism between the disk and the blade, which would require expensive adjustments in precision between the blade attachments and the fixing teeth on the disk. The invention also aims to minimize the mass of the entire rotor at the link with the blades.

Presentation of the invention

The invention relates to a turbomachine rotor blade comprising a first blade and a second blade arranged to form two successive blades of a blade rotor, a platform forming substantially an angular sector of wall in an axial direction, said two blades being connected at the platform by one of their ends extending substantially in a so-called radial direction substantially perpendicular to said axial direction, and attachment means connected to the platform which are intended to cooperate with fixing means on a rotor disc .

Said dawn is characterized in that said attachment means comprise two separate stilts, each stilt extending from the platform, in the radial direction, in the extension of one of said two blades, and carrying an attachment element to a end opposite the platform, said attachment member extending substantially parallel to said axial direction and having at least one surface facing the platform with a constant sectional profile perpendicular to said axial direction, so as to form a surface support for retaining the blade in said radial direction oriented from the platform to the blades.

The fact that the fastening element of each stilt extends parallel to the axial direction with a constant profile of the bearing surface makes it possible to mount the blade according to the invention by sliding the fastening element. against teeth of the rotor disk in the axial direction.

The fact of putting each stilt in the extension of each blade makes it possible to better align the passage of the stresses to hold the blade between the blades and the stilts during the rotation of the rotor. There is therefore no extra thickness to provide in the sizing of the stilts to withstand significant torsional moments and this allows a mass gain on the dawn compared to the state of the art of a two-blade dawn with a central foot.

Moreover, when the disc is thus equipped with a succession of vanes such that the blades can be associated two by two with stilts which are in their extension, it may be sufficient to provide holding teeth only in a circumferential interval out of two between the stilts. Indeed, if the fastening means are symmetrical, every second interval corresponds to the presence of the bearing surfaces and the other is empty holding means.

This therefore reduces the mass of the holding teeth on the periphery of the disc. Indeed, compared to single blades, the number of teeth is reduced by two, and compared to two-blade vanes according to the state of the art with a central foot, the mass of the teeth is reduced by separating them and by decreasing their circumferential width.

Finally, from the point of view of keeping the blade on the rotating disc, in the case of a two-blade blade, thus comprising only the first and second blades, the invention makes it possible to limit the hyperstatic character of the radial retention. against centrifugal efforts. Indeed, compared to a solution of the state of the art for a two-blade blade with a complete attachment under each blade, the blade according to the invention has only two contact planes instead of four. With four contact planes, much tighter manufacturing tolerances should be imposed than in the state of the art to ensure that one or two of the bearing surfaces are not inoperative.

In addition the greater spacing of the bearing surfaces is also advantageous for positioning the blades of the blade relative to the disk and therefore their positioning in the engine. Indeed, these bearing surfaces define with the teeth of the disk contact surfaces that position the blades. The greater the distance between the two contact surfaces, the more defects on these surfaces will have a small impact on the angular positioning defect of the blades.

Preferably, the bearing surface of the fastening element carried by each stilt is on one side of the outer fastening element with respect to the two stilts in a circumferential direction perpendicular to said axial and radial directions.

In this case, the stilts with their attachment element can be slid to the mounting between two successive teeth of the disc leaving a gap between the two stilts. The bearing surface is itself generally inclined relative to the radial direction.

In addition, in the case of a two-blade blade, the placement of the bearing surfaces circumferentially outside the stilts contributes to the stability of the connection to the disc vis-à-vis the forces exerted on the blade during operation of the rotor.

Advantageously, each stilt comprises a substantially plane web parallel to the axial direction forming said end bearing the fastening element, said web and the fastener element being arranged to have a side face turned in the opposite direction to the another stilt that is parallel to the axial direction with a constant profile.

In this configuration, a part of the web can also be engaged between the teeth of the disc and thus cooperate with the teeth to participate in the lateral retention of the blade.

In a preferred embodiment, the fastening element comprises a lug forming a lug with respect to said end veil of the stilt.

This embodiment minimizes the mass used to achieve the attachment of the blade.

Preferably, the blades being offset by a given distance at their junction with the platform in a circumferential direction, perpendicular to said axial and radial directions, said ends of the two stilts carrying the attachment element are offset by a distance substantially equal to said given distance.

Thus, the fasteners of several successive blades on the rotor create a repetitive pattern that can cooperate with a uniform distribution of similar teeth at the periphery of the rotor disc.

Preferably, the attachment element of each stilt is positioned in a circumferential direction, perpendicular to said axial and radial directions, on an average position of the end connected to the platform of the corresponding blade.

In this way, it minimizes the offsets that the stilt must catch between the curved blades and the bearing surfaces having a straight axial extension. This minimizes the dimensioning of the stilts with respect to the stresses induced by the centrifugal forces. Advantageously, each stilt is shaped so that the junction of the stilt with the platform follows the junction with the platform of the corresponding blade in its evolution along the axial direction.

The blade may advantageously comprise at least one wall connecting the two stilts transversely to said axial direction.

Such a wall has a stiffener function. It will prevent the deformations of the stilts under the centrifugal forces and can make it possible to reduce the thickness of the stilts, therefore their mass.

Said wall may extend radially between the stilts from the platform to a line joining the radial ends of the fastening elements opposite the platform.

This closes the air passage under the platform of the dawn, between the teeth of the disc.

The invention also relates to a turbomachine rotor comprising blades as described above.

Advantageously, the disk of said rotor carries at its periphery a succession of similar teeth shaped to cooperate with the blade attachment means, two successive teeth being separated in the circumferential direction by a distance at least equal to the width of a tooth following this direction.

Brief description of the figures:

The present invention will be better understood and other details, features and advantages of the present invention will become more apparent upon reading the following description with reference to the accompanying drawings, in which:

Figure 1 shows a rear view along the axis of rotation of a two-blade blade according to the state of the art cut in a radial plane.

Figure 2 shows a rear view along the axis of rotation of a two-blade blade according to the invention.

3 shows a rear view along the axis of rotation of a two-blade blade according to the invention cut in a radial plane. FIG. 4 represents a radial projection view on the internal platform of the elements of a blade according to the invention.

FIG. 5 represents a detail of FIG. 3 with the representation of a fictitious tooth eliminated by virtue of the invention with respect to certain embodiments according to the state of the art.

Figure 6 shows a perspective view of the rear of an improvement of the two-blade blade according to the invention cut in a radial plane.

FIG. 7 represents part of the rear view along the axis of rotation of a variant with respect to the blade of FIG. 6.

FIG. 8 represents a view part of the rear of a variant with respect to the blade of FIG. 6.

The elements having the same functions in different blade variants according to the invention are identified with the same references in the figures.

Description of an embodiment of the invention

With reference to FIGS. 2, 3 and 4, in a preferred embodiment, a blade 1 of a turbine according to the invention comprises two blades 2, 3 extending in a span along a radial direction R between an internal platform 4 and a platform external 5. The blade 1 is fixed on a rotor disc 6 movable about a direction axis X (shown in Figure 4), of which only a peripheral portion is shown with the teeth 7 holding the blade.

The axial and radial directions refer to the axis of the rotor, the internal and external terms refer to the radial direction. The terms upstream and downstream in the axial direction refer to the direction of flow for which the vanes were designed.

The inner and outer platforms 5 and 5 delimit an angular sector of the vein of passage of the flow of gas around said axis X. The outer platform 5 is not concerned with the invention and may possibly not exist, it is elsewhere, generally, the case for compressor blades. It is therefore not described further. More particularly, the internal platform 4 is delimited in the circumferential direction T between two axial planes, so as to adjust with the platforms adjacent blades to ensure continuity of the vein wall. The body 8 of the internal platform 4 defining the vein has a radial profile determined by the design of the turbine which can be inclined relative to the radial direction R. In the example, this profile deviates from the axis X of the rotor from upstream to downstream. At the axial ends of said body 8, the inner platform 4 here comprises an upstream radial web 9 and a downstream radial web 10 which extend radially so as to come into contact with the holding teeth 7 on the disc 6, at the same distance of the X axis. Here, the upstream web 9 and the downstream web 10 have a function of maintaining the blade 1, on the one hand to block its movement in the radial direction towards the X axis, on the other hand to block rotation around a direction parallel to the X axis. The inner platform 4 generally comprises devices attached to the upstream and downstream sails 9, for example annular spoilers January 1, for sealing with the stator elements. of the turbine that surround the rotor in the axial direction.

The two blades 2, 3 have a curved profile inclined with respect to the axial direction X which can evolve along their span in the radial direction R. FIG. 4 shows the shape of this profile at the base of the blades 2, 3, at their junction with the platform 4. The geometries of the two blades 2, 3 are similar with an angular offset corresponding to the rotor design and the number of blades to be installed. The bases of the blades 2, 3 are therefore shifted by a distance D determined at the level of the internal platform 4.

The attachment of the blade 1 to the disc 6 here comprises two separate stilts 12, 13 which are connected to the body 8 of the platform 4 and extend therefrom in the radial extension of one of the blades 2, 3, having substantially the same extension as said blades 2, 3 in the axial direction X. Each stub 12, 13 ends here, on the opposite side to the platform, by an axial web 14, 15, parallel to the radial direction R , which is connected to a tab 16, 17, parallel to the axial direction X and inclined relative to the radial direction, which tab forms the free end of the stilt. Said tab 16, 17 deviates laterally outwards starting from the axial web 14, 15, forming, in transverse section, an end pin, so that its outer lateral surface S1, S2 is turned towards the platform 4. The bearing surface S1, S2 is generally inclined relative to the radial direction. The angle of inclination depends on the design made by the skilled person according to the geometry of the turbine and operating constraints. Classically it takes values between 40 and 50 °, but can be outside this range. Each lug 16, 17 thus forms an attachment element of the blade 1 and the surfaces S1, S2 form bearing surfaces for retaining the blade in the radial direction R oriented from the platform to the blades. The axial webs 14, 15 of the stilts 12, 13 and the end tabs 16, 17 cooperate with the teeth 7 of the disc 6 to maintain the blade 1 according to an operation which will be described later.

The axial webs 14, 15 of the ends of each stalk 12, 13 are centered on an average position of the bases of the blades 2, 3 on the platform 4 in the circumferential direction T and are therefore shifted in this direction by a distance D 'substantially equal to the offset D between the bases of said blades 2, 3. Here, the sets formed of the axial webs 14, 15 and the end tabs 16, 17 are substantially symmetrical with respect to an axial plane passing through the middle of the stilts 12, 13.

Each stilt 12, 13 has a three-dimensional shape between the axial web 14, 15, and the platform 4, to follow the profile of the base of the corresponding blade 2, 3 at its junction with the body 8 of the platform 4.

In correspondence, the disc 6 of the rotor comprises at its periphery a ring of similar teeth 7 which are offset in the circumferential direction T by a distance substantially equal to twice the offset distance D between the bases of the blades 2, 3, of so that there are half as many teeth 7 than blades 2, 3 on the rotor.

Each tooth 7 extends here parallel to the X axis over a distance substantially corresponding to the gap between the upstream and downstream sails 10 of the platform, with a constant transverse profile. In this way, the blade 1 described above can be installed between two successive teeth 7 by sliding, in the axial direction X, the axial webs 14, 15 of the stilts 12, 13 and the end lugs 16, 17, between two successive 7 teeth. Known devices, not described here, then allow to maintain the blade 1 in its axial position relative to the rotor. These devices are not concerned by the invention. The profile of each tooth 7 here has the shape of a bulb. Starting from the outer surface of the disc 6, the tooth therefore has a portion of constant thickness given followed by enlargement. The shape of this widening is defined so as to form, on one side of the tooth 7, a surface facing the disk 6 which is in contact with the bearing surface S1 connected to one of the stilts 12 of the blade 1 and forming on the other side of the tooth, another surface facing the disk 6 which is in contact with the bearing surface S2 connected to the other of the stilts 13 of an adjacent blade, similar to the dawn 1. When the fastening elements 16, 17, of the two stems 12, 13 of the vanes are symmetrical, as described above, the profile of the teeth 7 is symmetrical with respect to a median radial plane of the tooth.

Finally the tooth 7 has a radially outer surface substantially flat or forming a circular cylinder portion centered on the axis X of the rotor. Thus, the free edges of the upstream sails 9 and downstream 10 of the platform 4 can bear on when the engine is stopped. As indicated above, the support of the upstream and downstream sails 10 blocks the radial displacements of the blade 1 towards the disc 6, so as to maintain the correct positioning of the blade 1 on the rotor.

The bearing surface S1, S2 of the end lug 16, 17, carried by each stalk 12, 13 is designed to take up about half of the centrifugal forces applied to the blade 1, ie substantially those corresponding to one of said blades. 2, 3. A stilt 12, 13 with its end tab 16, 17 must be dimensioned substantially to withstand the stresses imposed by a blade. Moreover, as represented by the arrows in FIG. 3, the three-dimensional portion of the stilt 12, 13 takes up these forces towards the base of the corresponding blade 2, 3 with a small radial inclination since it is here essentially to compensate for the curved shape of the profile of the blade 2, 3 but not a circumferential offset of half a gap with said blade. The dimensioning of the stilt 12, 13 and the end lug 16, 17, therefore results in giving them a thickness in the transverse direction slightly greater than half the thickness that would be necessary for the foot of a monal dawn but significantly less than half that for a single foot centered for a two-blade dawn. We thus gain mass on the attachment means to the disk 6 for the blade 1. It will be noted that, with regard to resisting centrifugal forces, the blade 1 is held by the contacts of only two bearing surfaces S1 and S2, each extending inclined with respect to the radial direction, at the same time as outside a stilt 12, 13 in the circumferential direction T. This limits the hyperstatism between the blade and the disk. In addition, the two stilts 12, 13 being spaced apart, said bearing surfaces S1, S2 are themselves spaced apart and located near the edges of the blade 1 in the circumferential direction T. This improves the stability of the assembly under the stress of the forces centrifugal, compared to a single fastener gathered in the center of the dawn.

The invention also allows a saving in mass on the disc 6. It can be seen in Figures 3 and 4 that the space between the two stalks 12, 13 of a two-blade blade 1 is empty of tooth. On the other hand, by repetition of a blade 1 to another, each tooth 7 of the disk 6 occupies a space extending between two blades in the circumferential direction T, one belonging to a blade, the other belonging to the next dawn. Therefore, compared to the known solution of a two-blade blade with a central foot, the teeth 7 of a disk adapted to blades according to the invention are significantly smaller than for a disk adapted to two-blade blades with a single foot , as can be seen by comparing Figure 3 and Figure 1. Moreover, FIG. 5 illustrates the gain in mass obtained with respect to the use of single blades or two-blade vanes with two fasteners according to the state of the art and which would therefore have 4 contact surfaces between the disc. and dawn. The teeth with the single blades would have a smaller thickness in the circumferential direction T but would be twice as many since it would be necessary to add the indicated tooth T in dotted lines to retain each blade, which results in the fact that, overall, the invention allows to gain on the mass of the teeth of the disc.

According to an improvement of the invention, with reference to FIG. 6, the blade 21 further comprises one or more transverse stiffening webs 18 which connect the two stilts 13, 14. Advantageously, such a stiffening web 18 extends radially to from the body 8 of the platform 4. In the example shown in FIG. 6, it closes the space between the stilts 12, 13 only at the level of the three-dimensional part, leaving free the space between the axial webs 14, 15. As shown in Figure 7, such a realization leaves free an air passage zone under the platform 4 and the upstream sails 9 and downstream 10, between the teeth 7 of the disc 6 of the rotor.

In a variant, represented in FIG. 8, the blade 31 comprises at least one stiffening web 19 which extends to the radial end of the fastening lugs 16, 17 carried by the stilts 12, 13, in the following manner. the periphery of the disc 6, so as to close the axial passage of the air between the teeth 7 under the platform 4 and the upstream and downstream sails 9 9.

The description of the embodiments of the invention made in this document is not limiting. The dawn described here is two-bladed but one can consider blades having a succession of pairs of blades with their stilts in the extension. In this case, however, the mounting of the bearing surfaces on the teeth becomes hyperstatic for the dawn, so more difficult to adjust. Other embodiments of the connection means with the disk, not shown, can also be envisaged. For example, the radial blocking of the blade towards the axis can be provided by an element carried by the stilts which presses on the disc 6 or on the radial crown of the teeth 7. The inner platform 4 may then have no sail upstream or downstream having a holding function. The invention has been described in the case of a turbine blade but it can also relate to blades adapted to other types of rotors, such as compressor rotors, for example. Furthermore, an attachment element at the end of the stilts 12, 13 other than a tab forming a bend with respect to the axial web 14, 15 may be used to make the bearing surfaces S1, S2. It can be realized, for example, by spoilers deviating from the surface of the veil. The shape of the teeth on the disc will then be adapted to the shape of the fasteners used on the blade.

Claims

claims

1. A turbomachine rotor blade (1) comprising a first blade (2) and a second blade (3) arranged to form two successive blades of a blade rotor, a platform (4) forming substantially an angular sector of the following wall an axial direction (X), said two blades (2, 3) being connected to the platform (4) by one of their ends extending substantially in a so-called radial direction (R) substantially perpendicular to said axial direction (X) , and attachment means connected to the platform (4) which are intended to cooperate with means (7) for attachment to a disk (6) of the rotor, characterized in that said attachment means comprise two stilts (12). , 13) separated, each stilt extending from the platform (4), in the radial direction (R), in the extension of one of said two blades (2, 3), and carrying a fastening element (16, 17) at an end opposite the platform (4), said element of staple extending substantially parallel to said axial direction (X) and having at least one surface (S1, S2) facing the platform (4) with a constant sectional profile perpendicular to said axial direction (X), forming a bearing surface for retaining the blade (1) in said radial direction (R) oriented platform (4) to the blades (2, 3).

2. blade (1) according to the preceding claim, characterized in that the bearing surface (S1, S2) of the fastening element (16, 17) carried by each stilt is on one side of the element external attachment relative to the two stilts (12, 13) in a circumferential direction (T) perpendicular to said axial (X) and radial (R) directions.

3. blade (1) according to one of the preceding claims, characterized in that each stilt (12, 13) comprises a web (14, 15) substantially plane and parallel to the axial direction (X) forming said end bearing the fastening element (16, 17), said web (14, 15) and the fastening element (16, 17) being arranged to have a lateral face facing in the opposite direction to the other stub which is parallel to the axial direction (X) with a constant profile.

4. blade (1) according to one of the preceding claims, characterized in that the fastening element (16, 17) comprises a lug forming a lug relative to the web (14, 15) at the end of the stilt .

5. blade (1) according to one of the preceding claims, characterized in that, the blades (2, 3) being offset by a given distance (D) at their junction with the platform (4) in a direction circumferential (T), perpendicular to said axial (X) and radial (R) directions, said ends of the two stilts (12, 13) carrying the fastening element (16, 17) are offset by a distance (D ') substantially equal to said given distance (D).

6. blade (1) according to one of the preceding claims, characterized in that the fastening element (16, 17) of each stilt (12, 13) is positioned in a circumferential direction (T), perpendicular to said directions axial (X) and radial (R), on an average position of the end connected to the platform (4) of the blade (2, 3) corresponding.

7. blade (1) according to one of the preceding claims, characterized in that each stilt (12, 13) is shaped so that the junction of the stilt with the platform (4) follows the junction with the platform (4) of the blade (2, 3) corresponding in its evolution in the axial direction (X).

8. blade (21, 31) according to one of the preceding claims, characterized in that it comprises at least one wall (18, 19) connecting the two stilts (12, 13) transversely to said axial direction (X ).

9. blade (31) according to the preceding claim, characterized in that said wall (18, 19) extends radially between the stilts (12, 13) from the platform (4) to a line joining the radial ends fastening elements (16, 17) opposite to the platform.

10. Turbomachine rotor comprising blades according to one of the preceding claims.