Turbine engine blade, rotor comprising such a blade and turbine engine comprising such a rotor

Abstract

The invention relates to a turbine engine blade comprising a blade root extending axially between two opposite axial end faces of the blade root. Each axial end face extends in the radial (Y) and transverse (Z) directions and radially between a radially inner end of the blade root intended to be arranged radially facing a bottom of a rotor disk socket and a neck (C) of the blade root. The blade comprises two axial end walls extending respectively from the two axial end faces. One wall has a radially inner end region (M1.1) connected to the neck (C) by a connection region which comprises a concave portion (Pcc) connected to the neck (C) and extending transversely and radially outward away from the neck, and a convex portion (Pcv) connected to the radially inner end region (M1.1) of the wall and extending transversely and radially inward from the concave portion.

Description

Description Title of the invention: Turbomachine blade, rotor comprising such a blade, and turbomachine comprising such a rotor Technical Field

[0001] The present presentation concerns a turbomachine blade, a turbomachine rotor comprising such a blade, and more particularly a plurality of such blades and a turbomachine comprising such a turbomachine rotor. Previous technique

[0002] It is known for a turbomachine to have a low-pressure turbine, downstream of a high-pressure turbine, which recovers some of the energy from the combustion of the gases to operate the blower, the compressor(s) and accessories.

[0003] The low-pressure turbine typically features an alternating axial arrangement of several stages, consisting of annular rows or rings of fixed blades and annular rows or rings of blades, known as rotating wheels, each positioned between two rows of fixed blades. The rotating blades are generally mounted on the outer periphery of a rotor disk capable of rotating around a longitudinal axis of the turbomachine. More specifically, the rotating blades are mounted by their roots in recesses in this disk, which open radially onto the outer periphery of the disk. These recesses are designed to receive the blade roots and cooperate with them to ensure their radial retention within these recesses during the rotation of the rotor disk. The recesses are located between teeth arranged circumferentially around the periphery of the rotor disk.

[0004] The moving blades generally extend radially relative to the longitudinal axis of rotation of the rotor disk. Moving blades comprise a blade root designed to be mounted in a cavity of the rotor disk and a blade that is located in the airflow channel to which the turbine is exposed. The blade includes at its base a platform that extends substantially perpendicularly to the radial extension (height) of the blade and a strut that connects the platform to the blade root. The blade root, for example, has a dovetail shape in a cross-sectional view in a plane defined by a radial direction and a transverse or tangential direction, these two directions being perpendicular to the longitudinal axis of rotation of the rotor disk. The blade root extends axially between a first axial end face and a second opposing axial end face, each extending in the radial and transverse directions. The blade comprises, in the stilt-forming portion, two walls or spars, each extending in the radial and transverse directions, forming respectively an upstream and a downstream stilt face, which are aligned with the first and second opposing end faces of the blade root.

[0005] The blade foot generally comprises a bulb mounted in the hollow of the cell and an area at the radial opening of the cell that forms a narrowing in cross-section, called the neck, in a plane defined by the radial and transverse directions. The area of ​​connection between the radially inner part of each wall and the neck of the blade foot includes, in a cross-sectional view, a connecting radius.

[0006] It turns out that the radius of connection between the throat and each wall is an area of ​​high mechanical stress concentration when the turbine is operating. Depending on the configuration, this area is even the most stressed area of ​​the blade and therefore the most limiting area in terms of lifespan and vibration capacity.

[0007] The inventors found that the value of the local stress depends strongly on the value of the connecting radius and, more specifically, the smaller the value of the connecting radius, the higher the stress.

[0008] Therefore, for good mechanical strength of the blade foot, it is desirable that the radius value be as large as possible.

[0009] However, this is not always feasible without adversely impacting the sizing of the attachment between the blade and the rotor disc or the control of radial clearances between the blade and the rotor disc.

[0010] If we want to avoid impacting the dimensions of the attachment between the blade and the rotor disc, the connection radius can be increased by offsetting upwards (i.e., in a radial direction away from the blade root) is the radially inner portion of each blade wall. However, such a configuration implies an increase in radial clearance between the radially inner portion of the blade wall and the opposing rotor disc tooth. This can result, for example, in increased tangential blade tilt and therefore an increased risk of blade root dislodgement (the blade root is located at one end of the blade opposite the blade root) and / or increased leakage, thus causing a decrease in turbine performance.

[0011] Controlling radial clearances between the blade and the rotor disc could be achieved by increasing the height of the rotor disc tooth. However, this is not always possible due to the impact on the dimensions of the attachment between the blade and the rotor disc. Indeed, increasing the mass of the rotor disc tooth affects the stress levels in the throats. This can also lead to increased stiffness in the attachments, which can affect the distribution of forces between the attachment bearing surfaces in the case of a double-bulb blade root configuration.

[0012] There is therefore a real need to reduce the constraints in the connection areas between walls and the necks of the moving turbine blades of turbomachinery by overcoming, at least in part, the aforementioned disadvantages. Description of the invention

[0013] The present exposition concerns, in its first aspect, a turbomachine blade comprising a root and a blade extending from the root. The root is intended to be mounted in an open cavity that opens onto an external periphery of a turbomachine rotor disk. The blade extends radially along a radial direction Y relative to a longitudinal axis about which the blade is intended to rotate. The blade extends axially along an axial direction X parallel to the longitudinal axis and transversely along a transverse direction Z perpendicular to the axial direction X and radial direction Y. The blade root extends axially between a first axial end face of the blade root and a second opposite axial end face of said blade root. Each face axial end face of the blade foot extending along the radial Y and transverse Z directions, each axial end face of the blade foot extending radially between, on the one hand, a radially internal end of the blade foot intended to be arranged radially opposite a bottom of a rotor disk cavity and, on the other hand, a neck C of the blade foot, the neck C of the blade foot forming a local narrowing of the cross-section of the blade foot along the radial Y and transverse Z directions which is arranged in a radially external position relative to the radially internal end of the blade foot, the blade comprising two axial end walls which each extend, at least along the radial Y and transverse Z directions, respectively from the first and second axial end faces of the blade foot and radially outwards from them,at least one axial end wall having a radially internal end zone of the axial end wall which is connected to the neck of the blade foot by a connecting zone, the connecting zone comprising, a concave portion which is connected to the neck and which extends transversely and radially outwards so as to move away from the neck and, a convex portion which is connected to the radially internal end zone of the axial end wall and which extends transversely and radially inwards from the concave portion, the blade foot comprising, from the neck of the blade foot, another concave portion comprising a first portion of a circle Cl of radius RI which connects the neck of the blade foot to a contact point Pc, the contact point Pc being intended to come into contact with an edge of the opening of the cell in which the blade foot is intended to be mounted,the concave part Pcc of the connecting zone comprising a second circular portion C2 of radius R2, the radius RI of the first circular portion Cl of the other concave part being different from the radius R2 of the second circular portion C2 of the concave part Pcc of the connecting zone.

[0014] The above configuration of the connection zone between the awl foot's neck and the radially internal zone of the corresponding wall provides an enlarged (more notched) concave section compared to the previous art (relatively small connection radius) and which extends both radially and Transversely, moving away from the tooth opposite the rotor disc (on both sides of the blade root, opposite the two disc teeth that define the recess receiving the blade root). This enlarged concave section reduces / relieves the mechanical stresses Kt in the connection zone, thus improving the blade's mechanical strength. It should be noted that the cross-section of the blade root is enlarged on both sides of the constriction (blade root neck), whether moving inwards, towards the radially inner end of the blade root, or outwards, away from this end.

[0015] According to possible characteristics - radii R1 and R2 satisfy the relation 0.5 <R2 / R1 <0,95 ; -the convex part of the connection zone is formed by a portion of a circle C3, 03' of radius R3, R3', of reversed curvature with respect to the portions of circles of the concave part Pcc; Pcc', and which connects the concave part Pcc; Pcc' to the radially internal end zone of the axial end wall; -the first portion of circle 01 and the second portion of circle 02 are connected to each other at a connection point Pt which has a radially internal position relative to the radially internal position Pri of the radially internal end zone of the axial end wall; -the awl foot is in the shape of a fir tree foot or in a dovetail joint; -the blade foot includes at least one bulb intended to be mounted in a cavity of a turbomachine rotor disc; - the aven's foot comprises two bulbs.

[0016] The present presentation concerns, according to a second aspect, a turbomachine rotor, comprising a plurality of turbomachine blades as briefly described above.

[0017] The present presentation concerns, according to a third aspect, a turbomachine, comprising a turbomachine rotor as briefly described above.

[0018] The characteristics and advantages of the moving turbine blade of turbomachinery mentioned above apply to the rotor and to the turbomachine including the rotor and will therefore not be repeated.

[0019] In this exposition, the terms "longitudinal", "transverse", "lower", "upper" and their derivatives are defined with respect to the main direction of the blades; the terms "axial", "radial", "tangential", "inner", "outer" and their derivatives are defined with respect to the main axis (axis of rotation) of the turbomachine; "axial plane" means a plane passing through the main axis of the turbomachine and "radial plane" means a plane perpendicular to this main axis; finally, the terms "upstream" and "downstream" are defined with respect to the airflow in the turbomachine.

[0020] In this discussion, an element is considered "removable" when it is possible to separate the element from the rest of the device without the aid of special tools.

[0021] The aforementioned features and advantages, as well as others, will become apparent upon reading the detailed description that follows, which includes examples of the implementation of a moving turbine blade for a turbomachine. This detailed description refers to the attached drawings. Brief description of the drawings

[0022] The attached drawings are schematic and are primarily intended to illustrate the principles of the presentation.

[0023] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference symbols.

[0024] [Fig. 1] Figure 1 is a partial schematic axial cross-sectional view of a low-pressure turbine according to an embodiment of the invention.

[0025] [Fig. 2A] Figure 2A is an enlarged schematic perspective view of the foot of a movable blade.

[0026] [Fig. 2B] Figure 2B is an enlarged schematic view of the blade foot of Figure 2A in cross-section in a Y, Z plane, showing the first end face of the blade foot.

[0027] [Fig. 3] Figure 3 is an enlarged schematic cross-sectional view of the wall-collar connection area of ​​the blade foot of figures 2A and 2B according to an embodiment of the invention.

[0028] [Fig. 4] Figure 4 is an enlarged schematic cross-sectional view of the wall-collar connection area of ​​the blade foot of figures 2A and 2B according to another embodiment of the invention.

[0029] [Fig. 5] Figure 5 is an enlarged schematic cross-sectional view of a double-bulb blade foot. Description of the implementation methods

[0030] To make the explanation more concrete, an example of a low-pressure turbine is described in detail below, with reference to Figure 1. It should be noted that the invention is not limited to this example and that the turbomachine blade described herein is applicable to high-pressure turbine blades, fan blades, low-pressure compressor blades, and high-pressure compressor blades. The turbomachine blade can be a blade from an aircraft turbomachine or a land-based turbomachine.

[0031] As shown in Figure 1 and designated by the general reference number 10, a low-pressure turbine is arranged, in an aircraft turbomachine, downstream of a high-pressure turbine 12. The terms upstream AM and downstream AV such that the upstream is axially located (considering the X-axis of the turbomachine, which is the axis around which the moving parts of the turbomachine are rotating) on ​​the side from which the general flow of the turbomachine originates, and the downstream is axially located on the side towards which this flow is directed.

[0032] The low-pressure turbine 10 comprises a succession of stages of annular rows of blades, alternating successively, in an axial arrangement, a stage of fixed annular rows of blades 18, called distributors, and a stage of rotating disk 16, and so on. These stages are arranged around the longitudinal axis X of the turbomachine. Each rotating disk 16 carries, on its outer periphery, a plurality of movable blades 14.

[0033] More specifically, each disc 16 comprises, on its outer periphery, circumferentially distributed teeth (the apex of which is referenced 20 in Figure 1) and recesses or grooves (the bottom of which is referenced 22 in Figure 1) arranged between the teeth, and in each of which a blade root (the radially internal end of which is referenced 24 in Figure 1) is mounted. In practice, the blade root is engaged axially (along an axial direction) parallel to the longitudinal axis X) within a cavity and held radially there, for example by a mechanical connection achieved through the cooperation of complementary shapes of the blade root and the cavity. In the example described, the blade root has, for example, a dovetail shape or a single bulbous shape similar to that of a dovetail to ensure its radial retention within the cavity. According to one variant, a blade root with a dovetail shape and two bulbs can be considered. According to another variant, a blade root with a fir-tree shape can also be considered.

[0034] The blades 14 extend radially, along a radial direction Y, from the bottoms 22 of the cells where they are mounted, away from the cells, in an annular flow channel 26 of a hot gas flow from an upstream combustion chamber of the turbomachine (not shown in Figure 1)-

[0035] Each blade 14 comprises, according to its radial dimension, radially from the outside to the inside, a blade 28 disposed in the annular flow channel 26 of the hot gas flow, a platform 30 which extends substantially perpendicularly to the (radial) extension axis of the blade and a strut 32 which connects the platform 30 to the radially internal end blade foot 24.

[0036] Figure 2A is a partial schematic view of a blade 14 which can, for example, be integrated into the low-pressure turbine 10 of Figure 1, in a downstream stage (not shown) located in the downdraft. This blade comprises the blade 28, the platform 30, the strut 32, and a blade root 34 with the radially inner end 24. The blade 14 also includes an airfoil formed by two profiled surfaces, the upper surface and the lower surface, each connecting a leading edge BA to a trailing edge BF of the blade.

[0037] As shown in Figure 2A, the platform 30 has an upstream spoiler 36 extending upstream and a downstream spoiler 38 extending downstream. The spoilers extend axially between consecutive turbine stages in order to partially maintain the structural integrity of the annular flow channel 26 between each turbine stage, thereby limiting the radial flow of hot gas into the turbine.

[0038] As shown in Figure 2A, the blade 14 extends not only radially along the radial direction Y, but also axially along the axial direction X, and transversely along a transverse direction Z perpendicular to the axial X and radial Y directions.

[0039] As shown in Figure 2A, the blade foot 34 extends axially along the axial direction X between a first end face 34a, called the upstream end face, and a second opposite end face 34b, called the downstream end face.

[0040] Each end face 34a, 34b of the blade foot extends along the radial direction Y and along the transverse direction Z (this extension defines the width of the blade foot), as illustrated in Figure 2B which shows a view, in a plane defined by the directions Y and Z, of the first end face 34a of the blade foot 34. In this figure, the partial contour of two consecutive teeth D1 and D2 of the rotor disk which define between them the cavity A in which the blade foot 34 is mounted according to a cross-section of the blade foot - cavity arrangement has been schematically represented in dashed lines.

[0041] Each end face 34a, 34b extends radially, along the radial direction Y, between, on the one hand, the radially internal end 24 of the blade foot 34 intended to be positioned opposite the bottom 22 of the cavity A and, on the other hand, a neck C of the blade foot which forms a narrowing of the cross-section (in the Y, Z plane) of the blade foot. In general, the neck of the blade foot is defined by the area of ​​the blade foot where the cross-section is minimal and which is identified, in the manner of Figure 3, by the point Pt. As shown in the figures, the cross-section of the blade foot is enlarged on both sides of the neck, whether in the lower part, in the direction of the end 24 (Fig. 2B), or in the upper part, away from end 24 and towards the low wall.

[0042] The neck C of the blade foot is arranged in a radially external position relative to the radially internal position of the radially internal end 24 of the blade foot, as illustrated in Figure 2B. The neck C of the blade foot is arranged at the level of a radially external opening, marked O in Figure 2B, of the cell A.

[0043] As shown in Figures 2A and 2B, the blade 14 also includes two end walls, labeled M1 and M2, each extending, at least in the radial direction Y and the transverse direction Z, respectively from the first and second opposite end faces of the blade root 34a, 34b, extending from and away from them. The radial wall M1, visible in Figure 2B, extends radially from the first end face 34a, in a plane defined by the radial direction Y and the transverse direction Z, until it reaches the radially inner face of the platform 30 (Figure 2A). The blade shown in Figure 2A is that of a downstream stage of the turbine, and the wall M2 has a different configuration from that of the wall M1. However, for the majority of turbine blades, the configuration of wall M2 corresponds to that of wall M1 which will be described below.

[0044] As shown, for example, in Figure 2B, for the wall M1, the latter includes a so-called radially internal zone which, here, corresponds to the radially internal face of the wall and which extends mainly in a transverse direction, on either side of the neck C of the end face 34a of the blade foot. In Figure 2B, the radially internal zone of the wall M1 is illustrated by two portions M1.1 and M1.2 which extend along the transverse direction Z on either side of the neck C, respectively. Each of these portions is considered a radially internal zone of the wall for the purposes of this discussion. The radially internal zone of the wall M1 is connected to the neck C by a connecting zone described below.

[0045] Figure 3 shows, in a half-cross-sectional view taken with respect to the plane of symmetry Ps of the blade foot in Figure 2B (the plane Ps extends along the axial X and radial Y directions), the connection zone between the neck C of the blade foot and the radially internal zone of the wall, namely here the portion M1.1. The connection zone between the neck C and the portion M1.2 of the wall (Fig. 2B) is obtained by symmetry from the connection zone of Figure 3.

[0046] As shown in Figure 3, the profile of tooth D1 is represented by a solid line, as is that of the blade root 34 and the connection zone between the blade root and the radially internal zone M1.1 of the wall. The two profiles of the blade root and the tooth are shown here in contact with each other via a bearing surface 34c of the blade root in contact with a face support D1.1 of the tooth. The blade foot moves away from the edge of the tooth from the contact point Pc.

[0047] In the present embodiment, the connection zone generally comprises a concave part Pcc which extends transversely (along the transverse direction Z) and radially (along the radial direction Y) outwards (radially external direction) away from the collar C to a radially external position Pre relative to the radially internal position Pri of the beginning of the radially internal zone M1.1 of the wall M1.

[0048] The connection zone also includes a convex part Pcv which extends transversely (along the transverse direction Z) and radially (along the radial direction Y) inwards (radially internal direction) from the concave part Pcc, extending the latter so as to join the beginning of the radially internal zone M1.1 of the wall M1.

[0049] Figure 3 shows the connection zone of the previous art in dotted lines. This connection zone includes, from the neck C of the foot of the blade, a portion of a circle of radius R1' which is extended by a straight portion L1, tangential to the portion of the circle, until it joins the beginning of the radially internal zone M1.1 (lower face) of the wall M1, without exceeding the radially internal position Pri of the radially internal zone M1.1.

[0050] As shown in Figure 3, the concave part Pcc of the new connection zone extends upwards (along the radial direction Y and away from the throat C) radially beyond the radially internal position Pri and widens, for example in a bulb shape, to reach the radially external position Pre, before descending again to join the radially internal zone M1.1. This widening of the curvature or radius of connection reduces the mechanical stresses applied in this area of ​​the blade and thus improves its mechanical strength.

[0051] More specifically, as shown in Figure 3, the blade foot includes another concave portion that connects the throat C to the contact point Pc, which takes the form of a circular segment of radius R1. The concave portion Pcc of the new connection zone includes, starting from the throat C, a second circular segment C2 with a radius R2 different from RI. The radius R2 is adjusted by in order to allow the portion of the circle C2 to extend radially above the connection zone of the anterior art and in particular radially above the radially internal position Pri. The radius R2 is enlarged compared to the radius RI', which allows it to give the concave part Pcc this enlarged shape, favorable to the reduction of mechanical stresses.

[0052] In a preferred embodiment, the radii R1 and R2 satisfy the relation 0.5 <R2 / R1 <0,95.

[0053] In this configuration, the first circular segment C1 and the second circular segment C2 are joined at a connection point Pt, which has a radially internal position relative to the radially internal position Pri of the radially internal zone M1.1 of the wall M1. In this configuration, the tangent between the circular segments C1 and C2 is vertical (radial). This configuration positions the connection point at the level of the blade root collar C, where the blade root's cross-section is minimal.

[0054] Furthermore, the convex terminal portion Pcv of the connection zone is formed by a third circular segment C3 of radius R3, with a curvature reversed relative to that of the first and second circular segments C1 and C2. The third circular segment C3 connects the second circular segment C2 of radius R2 to the radially internal zone M1.1 of the wall M1, whose radial position has not been modified.

[0055] It should be noted that the configuration described above allows the radial clearance J (figure 3) to be preserved between the radially internal zone M1.1 of the wall (lower face) and the radially external zone of the tooth (upper face) and thus to minimize the leakage section.

[0056] In addition, this configuration also makes it possible not to modify the part of the blade foot located radially below the connection point (Pt).

[0057] It should be noted that the configuration described above can also be applied to the wall M2, considering the connection area between this wall and the neck of the awl foot at the level of the downstream end face 34b.

[0058] Figure 4 illustrates another way of implementing a connection zone between the wall M1 and the neck of the awl foot.

[0059] In this other embodiment, the concave part Pcc' includes a portion of a circle Cl' which extends the portion of a circle Cl of radius RI from Figure 3 and which has the same radius RI. This extension of the circle Cl extends to a connection point Pt' which has a radially external position Pre' relative to the radially internal position Pri of the radially internal zone Ml.l of the wall Ml.

[0060] As shown in Figure 4, the connecting point Pt' is radially more external than the connecting point Pt in Figure 3 and is also offset transversely in the transverse direction Z, away from the throat C of the blade foot (away from the plane of symmetry Ps). The circular portion Cl' is connected at point Pt' to a circular portion C2' of the concave part Pcc'.

[0061] This connection configuration allows for consideration of certain operating conditions where, due to the three-dimensional change applied to the blade, the area of ​​maximum stress is not always located at the throat of the blade root, but sometimes in a position radially external to the throat. Thus, the circular portion Cl' of radius RI extends into the area of ​​the blade where the stresses are maximum, thereby reducing them.

[0062] Furthermore, in this connection configuration, the circular portion C2' of the connection zone, which extends the circular portion C1', has a radius R2' smaller than the radius R2 of the circular portion C2 in Figure 3. This allows the connection to the radially internal zone M1.1 of the wall M1 to be initiated without modifying the latter, thus preserving the clearance J and minimizing the leakage area. The connection to the radially internal zone M1.1 is made by the third circular portion C3', whose radius R3' is smaller than the radius R3 of the third circular portion C3 in Figure 3. These modifications to the radii of the two circular portions C2' and C3' do not, however, affect the stresses, as these circles are located outside the zone of maximum stress.

[0063] According to an alternative embodiment not shown in the figures, the circular portion C2' of radius R2' can be subdivided into two circular portions of different radii. This configuration allows for a greater local curvature and thus, in some cases, further improved leakage reduction by reducing the cross-sectional area.

[0064] Furthermore, such a variant also makes it possible to limit the leakage in the cavity created by the portion of the circle with radius R2'.

[0065] As shown in Figure 5, the movable blade according to this description can also be a 14' blade whose blade root has two bulbs, each defining a blade root neck, in this case an upper neck Cs and a lower neck Ci. The connection zone described above according to the different embodiments and variants refers here to the upper neck Cs.

[0066] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Demands

1. Turbomachine blade (14) comprising a foot (34) and a blade extending from the foot, the foot being intended to be mounted in an open cavity (A) opening onto an external periphery of a turbomachine rotor disk, the blade extending radially in a radial direction (Y) relative to a longitudinal axis about which the blade is intended to rotate, the blade extending axially in an axial direction (X) parallel to the longitudinal axis and transversely along a transverse direction (Z) perpendicular to the axial (X) and radial (Y) directions, the blade foot (34) extending axially between a first axial end face (34a) of the blade foot and a second opposite axial end face (34b) of said blade foot, each axial end face of the blade foot extending along the radial (Y) and transverse (Z) directions, each axial end face of the blade foot extending radially between, on the one hand, an internal radial end (24) of the blade foot intended to be arranged radially opposite a bottom (22) of a rotor disk cavity and, on the other hand, a neck (C) of the blade foot, the neck (C) of the blade foot forming a local narrowing of the cross-section of the blade foot along the radial directions (Y) and transverse (Z) which is disposed in a radially external position relative to the radially internal end of the blade root, the blade comprising two axial end walls (M1, M2) which each extend, at least in the radial (Y) and transverse (Z) directions, respectively from the first and second axial end faces of the blade root and radially outward from them, at least one axial end wall (M1) having a radially internal end zone (M1.1) of the axial end wall (M1) which is connected to the neck of the blade root by a connecting zone, the connecting zone comprising, a concave portion (Pcc; Pcc') which is connected to the neck (C) and which extends transversely and radially outward so as to move away from the neck and, a convex portion (Pcv; Pcv') which is connected to the radially internal end zone (Ml.l) of the axial end wall (Ml) and which extends transversely and radially inwards from the concave part (Pcc; Pcc'), the blade foot (34) comprising, from the neck (C) of the blade foot, another concave part comprising a first portion of a circle (Cl) of radius RI which connects the neck of the blade foot to a point of contact (Pc), the point of contact (Pc) being intended to come into contact with an edge of the opening of the cell in which the blade foot is intended to be mounted, the concave part (Pcc) of the connecting zone comprising a second portion of a circle (C2) of radius R2, the radius RI of the first portion of a circle Cl of the other concave part being different from the radius R2 of the second portion of a circle C2 of the concave part (Pcc) of the connecting zone.

2. Turbomachine blade according to claim 1, characterized in that the radii RI and R2 satisfy the relation 0.5 <R2 / Rl<0,95.

3. Turbomachine blade according to claim 1 or 2, characterized in that the convex part (Pcv; Pcv') of the connecting zone is formed by a portion of a circle (C3; C3') of radius R3, R3', with a curvature reversed with respect to the portions of circles of the concave part (Pcc; Pcc 7 ), and which connects the concave part (Pcc; Pcc 7 ) to the radially internal end zone (Ml.l) of the axial end wall (Ml).

4. Turbomachine blade according to any one of claims 1 to 3, characterized in that the first circular portion (Cl) and the second circular portion (C2, Cl) 7 ) of the concave part (Pcc; Pcc 7 ) are connected together at a connection point (Pt, C) which has a radially internal position relative to the radially internal position (Pri) of the radially internal end zone (Ml.l) of the axial end wall (Ml).

5. Turbomachine blade according to any one of the preceding claims, characterized in that the blade foot (34) is in the form of a fir tree foot or a dovetail.

6. Turbomachine blade according to the preceding claim, characterized in that the blade foot (34) comprises at least one bulb intended to be mounted in a cavity of a turbomachine rotor disk.

7. Turbomachine blade according to the preceding claim, characterized in that the blade root comprises two bulbs.

8. Turbomachine rotor, comprising a disk centered on an axis (X) and having a plurality of open cavities (A) opening onto an external periphery of the disk and a plurality of turbomachine blades (14) according to any one of the preceding claims, each blade being mounted in a cavity of the disk.

9. Turbomachine, comprising a turbomachine rotor according to the preceding claim.

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