This application is the U.S. national phase entry under 35 U.S.C. § 371 of International Application No. PCT/FR2019/051139, filed on May 20, 2019, which claims priority to French Patent Application No. 1854308, filed on May 23, 2018.
The present invention relates to the general field of aeronautical turbomachines, and more precisely the field of fan discs of an aeronautical turbomachine, an assembly comprising the fan platforms and the disc, and a fan comprising this assembly.
In a turbomachine, the blade platforms of the fan must provide several functions. From an aerodynamic point of view, these platforms have the primary function of defining the air flow stream of the air. In addition, they must also be capable of resisting large forces while deforming as little as possible and while remaining integral with the disc that carries them.
In order to satisfy these different requirements, certain configurations have been proposed in which the platforms have a first portion allowing defining the air flow stream and ensuring the retention of the platform when the motor is in rotation, and a second portion allowing limiting the deformations of the first portion under the influence of the centrifugal forces and maintaining the platform in position when the engine is stopped.
In the existing solutions, the platform can take the form of a box with a two-dimensional stream wall retained downstream by a drum and upstream by a shroud, the upstream retention by the shroud being accomplished above the tooth of the fan disc (one flange of the shroud axially and radially blocking the platform upstream).
An upstream retention of this type carried out above the tooth of the disc with a shroud has the disadvantage of imposing a high hub ratio, the hub ratio being the radius ratio taken between the axis of rotation and the outermost point on the leading edge of the blade.
Moreover, this upstream retention is likely to cause overstresses in the tooth and in the disc socket, at the connection between the shroud and the disc.
In order to optimize the performance of the fan, and more generally of the turbomachine, it is desirable to have an assembly of an applied fan blade platform on a fan disc which has the smallest possible hub ratio, while limiting the stresses at the tooth and the socket of the disc.
One embodiment relates to a disc able to support platforms and blades of a fan, and including:
By “upstream face” is meant upstream relative to the direction of flow of the air, when the disc is disposed in a fan.
By “axial protrusions” is meant axial in the direction of flow of the air, or along the axis of rotation of the disc, when the disc is disposed in a fan.
By “offset radially” is meant offset toward the interior of the disc, i.e. toward the axis of rotation of the disc.
The radial protrusions being offset radially toward the interior of the disc relative to the grooves of the disc, and disposed circumferentially between two teeth of the disc, when the protrusions are fastened to a platform retaining flange, the fastening zone being located on the protrusions is thus offset radially and circumferentially relative to the teeth of the disc. This has the advantage of limiting the stresses at the tooth of the disc when an external element, for example a platform retaining flange, is fastened to the disc.
Moreover, this fastening zone being radially offset relative to the teeth of the disc, this has the advantage of liberating space in the upstream axial end of the tooth of the disc, allowing for example machining the tooth of the disc. Machining of this type can allow the modification of the shape of the upstream axial end of a platform supported by said tooth, relative to known platforms, and thus modifying the air flow stream when the platform is disposed in a fan. It is thus possible to reduce the hub ratio in order to improve the performance of the fan, and therefore of the turbomachine in which the fan is mounted.
In certain embodiments, the radial protrusions are tabs machined on the upstream face of the disc and folded toward the center of the disc.
The tabs can have a principal face perpendicular to the axis of the disc, and a thickness, along the axis of the disc, that is small relative to the dimensions of the principal face. The shape of these radial protrusions has the advantage of being simple to make.
In certain embodiments, one face of the radial protrusions includes an opening with an axis parallel to the axis of the disc.
The opening can be made on the principal face of the tab. It allows fastening an exterior element to the disc, for example a retaining flange or a ferrule, by means of a screw or a bolt, for example.
In certain embodiments, in an upstream side view of the disc along the axis of the disc, the center of the opening of each radial protrusion is disposed on a straight line passing through the center of the disc and the bottom of a groove of the disc, the bottom of a groove being the point in the groove, in this view, situated at equal distance from the two teeth between which it is located.
In other words, the center of the opening of each radial protrusion is aligned radially with the bottom of a groove. The end of the teeth of the disc is the seat of high mechanical stresses when the disc is disposed in a fan. This disposition thus allows optimizing the circumferential spacing, in the upstream side view of the disc along the axis of the disc, from the center of each protrusion relative to the two teeth, where the mechanical stresses are high, between which it is located. The fastening of a shroud or ferrule to the radial protrusions can then be carried out in a less mechanically stressed zone than if the protrusions were aligned with the teeth. The distribution of stresses within the disc, when it is disposed in a fan, is thus optimized, and the existence of local excess stresses can thus be limited or avoided.
In certain embodiments, a radius of the disc being a segment between the center of the disc and the bottom of a groove, a distance between the center of the disc and the center of the opening of the radial protrusion is less than 95% of the radius of the disc, preferably less than 90%, more preferably less than 80%.
The fact of moving the center of the opening of the radial protrusion closer to the center of the disc allows spacing the more mechanically stressed zones from the fastening point between a shroud and the disc, when it is disposed in a fan.
In certain embodiments, the radial protrusions are disposed on the upstream face of the disc at regular intervals along the circumference of the disc. This allows a uniform distribution of the mechanical stresses on the upstream face of the disc, when a shroud is fastened to it.
In certain embodiments, the number of radial protrusions is equal to half the number of grooves of the disc.
Preferably, the radial protrusions are distributed at regular intervals in such a manner as to be aligned radially with the bottom of one groove in every two. Consequently, two times fewer connection means are necessary between the disc and a shroud, when a shroud is fastened to the disc, than if a radial protrusion were provided for each groove. This allows reducing the number of assembly steps and the number of connection parts necessary. The time and cost of assembly can thus be limited.
The present disclosure also relates to an assembly comprising a disc according to any one of the preceding embodiments, at least one platform, and at least one upstream retaining flange to ensure the axial and radial retention of the upstream axial end of the platform, wherein the upstream retaining flange is fastened to the radial protrusions of the upstream face of the disc.
When the retaining flange is fastened to the disc, the interface between the flange and the disc, corresponding to the fastening zone of the flange to a radial protrusion of the disc, is offset radially toward the interior of the disc, relative to a groove of the disc, and is circumferentially interposed between two teeth of the disc, unlike known systems in which this interface is located at the tooth of the disc. This offset allows limiting the stresses at the upstream axial end of the teeth. Moreover, the offset of this interface allows liberating space at the upstream axial end of the tooth of the disc, offering better possibilities of machining the tooth and therefore of modifying the shape of the platform and thus, reducing the hub ratio.
In certain embodiments, the upstream retaining flange is a shroud.
The present disclosure also relates to a turbomachine fan comprising an assembly according to any one of the embodiments described in the present disclosure, and a plurality of blades mounted in the grooves of the disc.
The invention and its advantages will be better understood upon reading the detailed description made hereafter of different embodiments of the invention, given by way of non-limiting examples. This description refers to the appended pages of figures, in which:
In the present disclosure, the term “longitudinal” and its derivatives are defined relative to the principal direction of the platform considered; the terms “radial,” “interior” and their derivatives are, for their part, defined relative to the axis of the disc, corresponding to the principal axis of the turbomachine; finally, the terms “upstream” and “downstream” are defined relative to the flow direction of the fluid passing through the turbomachine. Thus, unless otherwise indicated, the same reference symbols designate the same features on different figures.
The fan 2 also comprises a plurality of blades 20 with a curvilinear profile (only four blades 20 are shown in
Finally, the fan 2 comprises a plurality of applied platforms 30, each platform 30 being mounted in the interval between two adjacent fan blades 20, in proximity to their roots 20a, in order to delimit, on the interior side, an annular air entry stream in the fan 2, the stream being delimited on the exterior side by a fan casing.
Moreover, the disc 40 comprises, on its upstream face 40b, a plurality of radial protrusions 46, having the shape of tongues, and being disposed circumferentially at regular intervals around the axis A. These protrusions can be made for example by machining the upstream face 40b of the disc, for example on the disc stem. The number of radial protrusions 46 can be equal to half the number of grooves 42, each protrusion 46 being aligned radially with the corresponding groove 42. In other words, each protrusion 46 is interposed circumferentially between two teeth 44 of the disc 40. Moreover, each radial protrusion 46 is radially offset toward the interior of the disc, i.e. toward the axis A, relative to the corresponding groove 42.
Each radial protrusion 46 can include a fastening opening 46a on its upstream face 46b, allowing inserting a fastening means 49, for example a screw or a bolt. The attachment of an upstream retaining flange 50, a shroud for example, can thus be carried out at a radial protrusion 46, for example by inserting the fastening means 49 through a flange opening 52 and the fastening opening 46a of the protrusion, the fastening means 49 then being fastened, for example by a bolt, to the radial protrusion 46. The retaining flange 50 being fastened to the disc 40, an upper surface 54 of the flange 50 then allows ensuring the radial retention of a retaining surface 32 situated at the upstream axial end of the platform 30.
The fastening zone between the disc 40 and the retaining flange 50 being situated at the radial protrusions 46, therefore closer to the center of the disc, allows limiting the stresses exerted during the operation of the fan at sensitive surfaces such as the upstream axial end of the teeth 44. Moreover, this interface between the disc 40 and the retaining flange 50 being offset radially relative to the grooves in the disc, in comparison to known structures, the cantilevers 44c, usually allowing the fastening of the shroud to the upstream end of the disc teeth, can be eliminated. This allows liberating space at the upstream axial end of the teeth 44 of the disc. It is also possible to modify more freely the upstream axial end of the teeth 44, and therefore the upstream axial end of the platform 30, for example by providing an inclined wall 34 over the upstream end of the platform 30, the inclined wall 34 coming into contact with the tapered surface 44b of the tooth 44. It is thus possible to reduce the hub ratio in order to optimize the performance of the fan, and therefore of the turbomachine in which the fan is mounted.
Although the present machine has been described by referring to specific embodiments, it is obvious that modifications and changes can be performed on these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different embodiments illustrated/mentioned can be combined into additional embodiments. Consequently, the description and the drawings can be considered in an illustrative, rather than a restrictive sense.
Number | Date | Country | Kind |
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1854308 | May 2018 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2019/051139 | 5/20/2019 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2019/224464 | 11/28/2019 | WO | A |
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3048448 | Sep 2017 | FR |
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Entry |
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Search Report dated Jan. 18, 2018, in FR Application No. 1854308 (2 pages). |
International Search Report issued in International Application No. PCT/FR2019/051139 dated Sep. 6, 2019 (3 pages). |
Number | Date | Country | |
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20210189893 A1 | Jun 2021 | US |