The present disclosure concerns a rotor disc for a turbomachine, for example a low-pressure turbine rotor disc of a turbojet engine.
In a known manner, a turbomachine includes an aerodynamic flow path in which movable impellers (rotor portion) which recover the energy from the gases derived from the combustion chamber and distributors (stator portion) which straighten the flow of gases in the aerodynamic flow path follow each other. The movable impellers generally include a disc movable in rotation about an axis of rotation, the disc being provided with blades. The blades may be manufactured separately and assembled on the disc by interlocking of the blade roots in cavities of the disc. The shape of the cavities is generally obtained by broaching of each cavity. The cavities are therefore through cavities. Therefore, the blades are generally axially blocked on their upstream and downstream faces by retention rings.
In particular in a low-pressure turbine of a turbomachine, the rings of axial retention of the blades located generally upstream and downstream of the blade roots undergo stresses that may cause gas leaks, particularly the downstream retention ring which undergoes more stresses than the upstream retention ring, because it is subjected to mechanical and thermal stresses which are greater, in particular because of the aerodynamic axial force which tends to push the blade downstream. In addition, the blade is also axially blocked by a movable ring bearing against the downstream retention ring. This movable ring rotates about the axis of rotation with the rotor and generally bears against two successive stages of the rotor of the turbine, the movable ring being axially clamped between the two stages in order to ensure the axial blocking of the blades in the disc. Also, the service life of the retention rings, particularly of the downstream retention ring, and of the movable ring is dependent on the mechanical and thermal stresses that these parts undergo in operation. Replacing these parts may turn out to be a very complex, costly and time consuming operation.
It will be noted that the terms “upstream” and “downstream” are defined in relation to the direction of circulation of air in the turbomachine.
The present disclosure aims at overcoming at least partly these drawbacks.
To this end, the present disclosure concerns a rotor disc for a turbomachine, the disc extending circumferentially about an axis and including a plurality of cavities configured to receive blade roots, each cavity including a downstream radial wall configured to axially block the blade root in the cavity, each downstream radial wall including a channel of ventilation of the cavity, including an inlet orifice which opens into the cavity and an outlet orifice which opens onto a downstream surface of the disc.
The axis of rotation of the disc defines an axial direction which corresponds to the direction of the axis of symmetry (or quasi-symmetry) of the disc. The radial direction is a direction perpendicular to the axis about which the disc extends circumferentially and intersecting this axis. Likewise, an axial plane is a plane containing the axis of the disc and a radial plane is a plane perpendicular to this axis.
Unless otherwise specified, the adjectives “internal/inner” and “external/outer” are used with reference to a radial direction so that the internal portion of an element is, along a radial direction, closer to the axis of rotation of the disc as the external portion of the same element.
Each cavity including a downstream radial wall, it is possible to axially block the blade in the cavity and dispense with the use of a downstream retention ring. It is understood that the downstream radial wall may be formed integrally with the disc.
In addition, due to the absence of the downstream retention ring, it is also possible to eliminate the hook for holding the ring of downstream retention of the blade. Thus, the blade, in particular the blade root and the inner platform, may have a simpler geometric shape. The manufacture of the blade is therefore less complex.
In addition, due to the absence of the downstream retention ring, it is also possible to dispense with the upstream portion of the movable ring, that is to say the portion of the movable ring upstream of the sealing wipers. Indeed, the movable disc may no longer be in compression between two rotor stages to maintain the downstream retention ring.
Assembling the stages of the rotor, and particularly the blades on the discs of the different stages of the rotor, is less complex and involves using a reduced number of elements. This results in a reduction in the rotor weight.
Thanks to the presence of a ventilation channel whose inlet orifice is present in each downstream radial wall, it is possible to ventilate each cavity and thus ensure efficient and uniform cooling of all the cavities of the disc.
In addition, the cooling of the disc is monitored by the dimension of the outlet orifice of the ventilation channel.
With this arrangement, it is possible to reduce the leakage of the air stream into the cooling stream. The flow rate of the cooling stream may therefore be better monitored and therefore reduced, which allows increasing the purge flow rate upstream of the first movable impeller at a constant total flow rate (purge stream and cooling stream). Thus, this arrangement allows improving the efficiency of the turbomachine.
The turbomachine may for example be a turbojet engine.
The rotor may for example be a turbine rotor.
The turbine may for example be a low-pressure turbine.
In some embodiments, the outlet orifice opens onto a downstream surface of the downstream radial wall.
In some embodiments, each downstream radial wall includes an outlet orifice.
In some embodiments, the ventilation channel links at least two inlet orifices and one outlet orifice.
The ventilation channel is present in the downstream radial wall and also in portions of the disc delimiting the cavities, for example teeth of the disc which delimit the cavity, along the circumferential direction.
In some embodiments, the ventilation channel links all of the inlet orifices.
The ventilation channel may be a circumferential channel linking all the inlet orifices to each other.
The circumferential direction is a direction along a circle which lies in a radial plane and whose center is the axis of rotation.
It is understood that the ventilation channel may have a shape other than a circumferential shape.
In some embodiments, the inlet orifices have an inlet diameter and the outlet orifices have an outlet diameter, the number of inlet orifices being greater than or equal to the number of outlet orifices and the inlet diameter being greater than or equal to the outlet diameter.
In some embodiments, the inlet orifices have a frustoconical shape that flares from downstream to upstream.
The flaring of the frustoconical shape allows limiting the head loss in the ventilation channel.
In some embodiments, the inlet orifices have an inlet diameter and the outlet orifices have an outlet diameter, the number of inlet orifices being greater than or equal to the number of outlet orifices and the inlet diameter being smaller than or equal to the outlet diameter.
When the number of inlet orifices is greater than the number of outlet orifices, the manufacture of the disc is facilitated because the number of outlet orifices is limited.
Furthermore, when the outlet diameter is greater than the inlet diameter, the discharge of dust that may be present in the air stream is facilitated.
In some embodiments, at least one among the inlet orifices is axially aligned with at least one among the outlet orifices.
The orifices being of generally circular shape, it is understood that the center of the circle forming the inlet orifice and the center of the circle forming the outlet orifice are aligned along a direction parallel to the axis of rotation when a line segment linking the center of the inlet orifice to the center of the outlet orifice is parallel to the axis of rotation.
In some embodiments, at least one among the inlet orifices is circumferentially and/or radially offset relative to at least one among the outlet orifices.
Thus, the center of the circle forming the inlet orifice and the center of the circle forming the outlet orifice may be offset relative to each other along a circumferential and/or radial direction.
In some embodiments, the downstream radial wall has a thickness greater than or equal to 0.5 mm (millimeter) and less than or equal to 10 mm.
The thickness of the walls allows limiting the mass of the disc.
In some embodiments, the inlet orifices have a diameter greater than or equal to 0.5 mm and less than or equal to 10 mm.
The inlet orifice with a diameter greater than or equal to 0.5 mm allows limiting the risk of clogging of the ventilation duct.
In some embodiments, the outlet orifices have a diameter greater than or equal to 0.5 mm and less than or equal to 10 mm.
The outlet orifice with a diameter greater than or equal to 0.5 mm allows limiting the risk of clogging of the ventilation duct.
The present disclosure also concerns an assembly for a turbomachine including a disc as defined above and an upstream retention ring.
The assembly may include blades assembled on the disc.
The present disclosure also concerns a turbomachine including an assembly as defined above.
It is understood that the turbomachine may include one or more stages including an assembly as defined above. For example, the turbomachine may be a turbojet engine. For example, the assembly as defined above may be disposed in the low-pressure turbine of the turbojet engine.
Other characteristics and advantages of the object of the present disclosure will emerge from the following description of embodiments, given by way of non-limiting examples, with reference to the appended figures, in which:
In all the figures, the elements in common are identified by identical numeric references.
The terms “upstream” and “downstream” are defined in relation to the direction of circulation of the air in the turbomachine, in this case, according to the circulation of the air stream F in the turbojet engine 10.
The turbojet engine 10 includes a fan casing 24 extended rearward, that is to say downstream, by an intermediate casing 26, including an outer shroud 28 as well as a parallel inner shroud 30 disposed, along a radial direction R, internally relative to the outer shroud 28. The radial direction R is perpendicular to the main axis A.
The terms “outer” and “inner” are defined in relation to the radial direction R so that the inner portion of an element is, along the radial direction, closer to the main axis A than the outer portion of the same element.
The intermediate casing 26 further includes structural arms 32 distributed circumferentially and extending radially between the inner shroud 30 up to the outer shroud 28. For example, the structural arms 32 are bolted to the outer shroud 28 and on the inner shroud 30. The structural arms 32 allow stiffening the structure of the intermediate casing 26.
The main axis A is the axis of rotation of the turbojet engine 10 and of the low-pressure turbine 22. This main axis A is therefore parallel to the axial direction.
The low-pressure turbine 22 comprises a plurality of blade impellers which form the rotor of the low-pressure turbine 22.
The first and second discs 36, 42 of the rotor each include at least a linking shroud 46.
In the embodiment of
In
The movable ring 50 carries sealing wipers 54 which sealingly cooperate with a ring of abradable material 56 carried by the distributor 44.
As represented in
As can be seen in
In the embodiment of
In one embodiment, not represented, the outlet orifice 70 could open onto a portion of the downstream face 34A of the disc 34 which is not the downstream face of the downstream radial wall 64.
In the embodiment of
The blades 38 of the first blade impeller 34 include a hook for holding 72 an upstream retention ring 74 for the axial blocking of the blades 38 in the cavities 60.
In the embodiment of
For example, the first disc 36 may be produced by additive manufacture, in particular by a powder bed-based additive manufacturing method.
In the following, the elements common to the different embodiments are identified by the same numeric references.
In the embodiment of
For example, in the embodiment of
In the embodiment of
In the embodiment of
Although the present disclosure has been described with reference to a specific exemplary embodiment, it is obvious that various modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. For example, the inlet orifice might not be aligned along a direction parallel to the main axis A with the outlet orifice.
Furthermore, individual characteristics of the different embodiments mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in an illustrative rather than a restrictive sense.
Number | Date | Country | Kind |
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1857926 | Sep 2018 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2019/051963 | 8/26/2019 | WO | 00 |