Turbomachine blade

Abstract

The invention relates to a turbomachine blade (5) comprising a blade (8) extending along a radial axis, and a heel (9) located at a radially external end of the blade, characterized in that the heel (9) comprises at least two distinct radial flat areas (19), parallel to each other and circumferentially separated from each other. Figure to be published with the abstract: [Fig. 4]

Description

Description Title of the invention: Turbomachine blade. Technical field of the invention. The invention relates to a turbomachine blade, in particular a rotor blade of a low-pressure turbine. The turbomachine is, for example, a turbojet or an aircraft turboprop engine. Prior art An aircraft turbomachine typically extends around an axis and generally comprises, from upstream to downstream in the direction of gas flow along this axis, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, and a low-pressure turbine. The rotor of the low-pressure compressor is driven by the rotor of the low-pressure turbine, and the rotor of the high-pressure compressor is driven by the rotor of the high-pressure turbine. The terms axial, radial and circumferential are defined with respect to the axis of the turbomachine. Figure 1 illustrates a high-pressure turbine 1 and a low-pressure turbine 2 of a prior art turbomachine. The low-pressure turbine 2 comprises several successive stages, each stage comprising a distributor 3 belonging to the stator and a wheel Ad's movable blades belonging to the rotor. Figures 2 and 3 illustrate such movable blades 5. Each blade 5 comprises, radially from the inside out, a foot 6, a radially internal platform 7, a blade 8 and a heel 9. The heel 9 has a radially external platform 10 comprising two lateral edges 11, an upstream beak 12, and a downstream beak 13. The heel 9 further has slits 14 extending radially outwards from the external platform 10 and also extending in the circumferential direction. Each lateral edge 11 of the heel 9 has a recessed area 15 or a projecting area 16, generally triangular in shape, for example, intended to cooperate with a projecting area 16 or a recessed area 15, respectively, of the heel 9 of an adjacent blade 5. A stiffener 17 can extend from the external platform 10, upstream to downstream, in order to increase the mechanical resistance of the heel 9. The foot 6 of each blade 5 is inserted into a recess in a rotor disc 17, the blades 5 being mounted adjacently so that the radially inner platforms 7 and the radially outer platforms 10 form two annular rings delimiting part of the gas flow stream within the turbine low pressure. The 14 wipers cooperate with a ring of abradable material, as is known in itself, to ensure sealing in this area during operation. Rotor blades can accumulate residual stresses from their manufacturing process (casting and / or machining operations), which are released after heat treatment and can then cause the root tip to rotate around the radial axis of the blade. This phenomenon is all the more significant given the current trend towards reducing blade mass and sizing them as precisely as possible according to requirements. The aging of rotor blades can also cause geometric variations through blade untwisting. These variations in the orientation of the heel can exceed one hundred arcminutes, which may be unacceptable and necessitate the replacement of some blades. To ensure the smooth execution of manufacturing, maintenance, or repair procedures for such blades, for example, it is necessary to have geometric reference points that allow for the reliable quantification of the heel's position and / or orientation using a simple measurement method that can be implemented by an operator. Currently, for example, there are no flat areas at the heel that would allow for such a measurement. Indeed, the blade edges and the heel in general, although generally flat, actually have curves or complex shapes that prevent such orientation measurements from being easily and repeatedly performed by an operator. In fact, most of the heel surfaces are produced by a casting process and include draft angles or curved areas, with shapes calculated to precisely meet functional requirements (optimized profile and thin thicknesses to lighten the blade). The invention aims to facilitate such a measurement of the position and / or orientation of the heel of a blade, in a simple, efficient and inexpensive way. Presentation of the invention For this purpose, the invention relates to a turbomachine blade comprising a blade extending along a so-called radial axis, and a heel located at a radially external end of the blade, characterized in that the heel comprises at least two distinct radial flat areas, parallel to each other and circumferentially separated from each other. The flat areas are called radial because they are each parallel to the radial direction or axis, also known as the blade stacking axis. These flat areas are specifically strictly radial, meaning they extend only in the radial direction and therefore do not form an angle with said radial direction. The two flat areas form two control zones allowing the use measuring tools are used during manufacturing, maintenance, or repair operations to easily and reliably check the position and / or orientation of the heel relative to at least one other reference area of ​​the blade. Such a measurement can be performed by various methods, such as point measurement using a coordinate measuring machine (CMM), or surface measurement, for example, non-contact measurement using a laser. One control method could then consist of measuring the deviation between each flat area and a nominal reference value in order to calculate an actual positional deviation that can be directly caused by the rotation of the heel. This deviation can then be compared to tolerances that may depend, in particular, on the process chosen for manufacturing the flat areas. The two flat areas are preferably produced from the same manufacturing operation, for example, during the same casting, forging, or machining operation. Alternatively, the two flat areas can be produced from the same manufacturing sequence during an additive manufacturing operation. In this case, the flat areas do not undergo any subsequent intervention that could degrade their condition. The manufacturing process can also be adapted so that these areas undergo as few variations as possible during the manufacturing tooling process. For example, fixed parts of a wax mold during a casting step will be prioritized over potentially moving parts whose wear and tear can lead to dimensional variations that affect the desired geometry. The two flat areas may not be coplanar, and a shift may then exist between the two flat areas. The invention can be applied to a turbine blade, for example a low-pressure turbine, or to a compressor blade, for example a blower or low-pressure compressor blade. More generally, the invention is applicable to any type of deformable blade, one that is susceptible to deformation, or one that is difficult to control, for example a blade with no flat surfaces, and whose manufacturing or transformation risks deforming the part, for example by twisting following heat treatments that release residual stresses (from casting or machining, for example). The heel may include a platform from which at least one slit extends radially outwards and in a circumferential direction perpendicular to the radial direction, the flat areas being formed on said slit. Can the surface area of ​​each flat zone be at least 3 mm? This ensures that each flat area is large enough to allow for an accurate measurement of its position using the measurement methods currently in use. Each flat area may have a flatness requirement (derived from an ISO standard) representing the distance between the two planes within which the entire surface must lie. The actual surface area of ​​each flat area is less than 0.02 mm. The distance between the two flat areas must be at least 10 mm. The distance is measured, for example, outside of the flat areas, that is, not between the centers of the areas but between the corresponding circumferential ends of the flat areas. Sufficient distance allows reliable calculation of the rotation or rotational defect of the heel, from the position measurements of the flat areas. At least one of the flat areas can be made at the level of a protruding area of ​​the heel, in particular the lick. The projecting area can extend axially upstream or downstream of the corresponding slit. This embodiment facilitates the fabrication of flat areas. Each flat area can be created at the level of a protruding area of ​​the heel, in particular the lick. At least one of the flat areas can be made at the level of a hollow area of ​​the lick. Naturally, the recessed area is sized and positioned so as not to affect the mechanical characteristics of the blade. Each flat area can be created at the level of a recessed area of ​​the heel, in particular the lip. Each flat surface can extend in a radial plane. Alternatively, the two flat surfaces can extend in the same plane oblique to the radial plane. The heel may include at least two slits, each extending radially outwards from the heel platform and in a circumferential direction perpendicular to the radial direction. One of said slits may include said flat areas. At least one stiffener can extend radially outwards from the heel platform and axially between the two slats. The stiffener can also extend upstream and downstream of the corresponding slats. Such a stiffener improves the mechanical resistance of the blade at the heel. The invention also relates to a turbomachine comprising at least one blade of the aforementioned type. The blade is, for example, a rotor blade. The turbomachine is, for example, a turbojet or an aircraft turboprop engine. The aircraft can be an airplane. Brief description of the figures [Fig.1] is an axial cross-sectional view of a prior art turbomachine turbine, [Fig.2] is a perspective view of a dawn from earlier art, [Fig.3] is a perspective view of part of a bladed rotor wheel of the prior art, [Fig.4] is a top view of a blade according to one embodiment of the invention, [Fig. 5] is a perspective view of the heel and the radially external end of the blade according to the invention, [Fig. 6] is a perspective view of the heel and the radially external end of the blade according to another embodiment of the invention, [Fig. 7] is a perspective view of the heel and the radially outer end of the blade according to yet another embodiment of the invention. Detailed description of the invention Figures 2 and 3 illustrate a blade 5 according to one embodiment of the invention, for example, a rotor blade 5 of a low-pressure turbomachine turbine. The blade 5 comprises, radially from the inside out, a foot 6, a radially internal platform 7, a blade 8, and a heel 9. The blade 8 extends in the radial direction. The heel 9 has a radially external platform 10 comprising two lateral edges 11, an upstream beak 12, and a downstream beak 13. The heel 9 further has slits 14 extending radially outwards from the external platform 10 and also extending in the circumferential direction. Each lateral edge 11 of the heel has a recessed area 15 or a projecting area 16, generally triangular in shape, for example, intended to cooperate with a projecting area 16 or a recessed area 15, respectively, of the heel 9 of an adjacent blade 5. A stiffener 17 further extends from platform 10, upstream to downstream, in order to increase the mechanical resistance of the heel 9. The foot 6 of each blade 5 is intended to be inserted into a recess of a disc 17, the blades 5 being mounted adjacently so that the radially internal platforms 7 and the radially external platforms 10 form two annular rings delimiting part of the gas circulation vein within the low pressure turbine 2. The 14 licks are intended to cooperate with a ring of abradable material, as is known in itself, to ensure sealing in this area in operation. The upstream 14 lick has at least two distinct flat areas 19, parallel to each other and circumferentially separated from each other. The surface area of ​​each flat zone 19 can be at least 3 mm. Each flat zone can be square or rectangular, for example. Each flat area 19 may have a flatness requirement (derived from an ISO standard representing the distance between the two planes within which the entire actual surface of each flat area must lie) of less than 0.02 mm. The distance d between the two flat areas 19 may be at least 10 mm. This distance d is measured outside the planar zones 19, that is to say between the corresponding circumferential extremities of said zones 19. Each flat area 19 is produced, for example by machining or as cast, at the level of a projecting area 20 of the upstream slit, said projecting area extending upstream from said slit. In the embodiment shown in Figures 4 and 5, the flat areas 19 extend in a radial plane. According to another embodiment illustrated in [Fig.6], the said flat areas 19 can extend in the same plane oblique to the radial plane. Figure 7 illustrates another embodiment in which the two flat areas 19 are made at the level of hollow areas 21 of the slot 17, for example at the level of the connection area of ​​the slot 17 with the external platform 10. In each of these embodiments, the two flat areas 19 form two control zones allowing the use of measuring tools during manufacturing, maintenance, or repair operations, in order to easily and reliably check the position and / or orientation of the heel 9 relative to at least one other reference zone of the blade. Such a measurement can be carried out by various methods, such as, for example, point measurement using a three-dimensional measuring machine or DEM, or surface measurement, for example, non-contact measurement using a laser. As previously stated, one control method may then consist of measuring the deviation between each flat area 19 with a nominal reference value in order to calculate an actual position deviation which may be directly caused by the rotation of the heel 9. This deviation can then be compared to tolerances which may be a function in particular of the process chosen for the production of the flat areas.

Claims

Demands

1. Aubc (5) dc turbomachine comprising a plac (8) extending according to a radial axis, and a heel (9) located at a radially external end of the dawn, characterized in that the heel (9) comprises at least two distinct radial flat zones (19), parallel to each other and separated circumferentially to each other.

2. Dawn (5) according to the preceding claim, wherein the heel (9) includes a platform (10) from which at least one lick {14) extends radially outwards and extends in a direction circumferential perpendicular to the radial direction, the flat areas (19) being formed on said lick (14).

3. Blade (5) according to the preceding claim, wherein the surface of is each flat area (19) at least equal to 3 mm?

4. Dawn (5) according to any one of the preceding claims, in which each flat area (19) has a flatness requirement, representing the distance between the two planes in which the entirety of the actual surface area of ​​each flat area, less than 0.02mm.

5. Dawn (5) according to any one of the preceding claims, wherein the The distance (d) between the two flat areas (19) is at least equal to 10 mm.

6. Blade (5) according to any one of the preceding claims, wherein one at least flat areas (19) can be achieved at the level of an area protruding (20) from the heel (9).

7. Blade (5) according to any one of the preceding claims, wherein one at least flat areas (19) can be achieved at the level of an area in the hollow (21) of the heel (9).

8. Blade (5) according to claim 2 and according to one of the preceding claims preceding, in which the heel (9) has at least two licks (14) each extending radially outwards from the plate- shape (10) of the heel (9) and in a circumferential direction perpendicular- dicular in the radial direction, one of said licks (14) comprising said flat areas (19).

9. Blade (5) according to the preceding claim, wherein at least one stiffener (17) extends radially outwards from the platform (10) of the heel (9) and axially between the two blades (14).

10. Turbomachine comprising at least one blade (5) according to one of the claims previous instructions.