Blade comprising an improved cooling circuit

Abstract

Blade for a turbine, comprising a blade root and an airfoil (13) extending radially outwards from the blade root (12), the airfoil (13) comprising a first internal cooling circuit including an intrados cavity (33, 36) extending radially along the intrados wall (16) and a first inner wall (47, 45) arranged between the intrados wall (16) and the extrados wall (18), an extrados cavity (34, 37) extending radially along the extrados wall (18) and a second inner wall (47, 43) arranged between the intrados wall (16) and the extrados wall (18). The first cooling circuit includes one inner through cavity (35, 38) defined between two through walls (59, 57, 55, 53) each extending between the intrados wall (16) and the extrados wall (18). The intrados cavity (33, 36), the extrados cavity (34, 37) and the inner through cavity (35, 38) are fluidly connected in series.

Claims

1. A blade for a turbine, comprising a blade root defining a radially inner end of the blade and an airfoil extending radially outwards from the blade root and having an intrados wall and an extrados wall connected to the intrados wall at a leading edge and a trailing edge of the airfoil, the airfoil comprising at least a first internal cooling circuit including at least one intrados cavity extending radially along the intrados wall and along a first inner wall arranged between the intrados wall and the extrados wall, and at least one extrados cavity extending radially along the extrados wall and along a second inner wall arranged between the intrados wall and the extrados wall, wherein the first internal cooling circuit further includes at least one inner through cavity defined between two through walls each extending between the intrados wall and the extrados wall, the at least one inner through cavity extending radially along the intrados wall and the extrados wall, wherein the at least one intrados cavity, the at least one extrados cavity and the at least one inner through cavity are fluidly connected in series, and wherein the at least one intrados cavity and the at least one extrados cavity are arranged on either side of the at least one inner through cavity and a passage fluidly connects the at least one intrados cavity to the at least one extrados cavity without passing through the at least one inner through cavity.

2. The blade according to claim 1, wherein the at least one intrados cavity, the at least one extrados cavity and the at least one inner through cavity are fluidly connected in series in this order.

3. The blade according to claim 1, wherein the first inner wall is connected to a first one of said through walls and the second inner wall is connected to a second one of said through walls.

4. The blade according to claim 1, further comprising a third through wall connected to the first inner wall or to the second inner wall, the internal cooling circuit further including a second through cavity extending radially along the intrados wall, the extrados wall and the third through wall.

5. The blade according to claim 1, wherein the intrados cavity is arranged on the trailing edge side and the extrados cavity is arranged on the leading edge side with respect to the inner through cavity.

6. The blade according to claim 1, wherein the first inner wall and the second inner wall are each delimited by two through walls, each through wall extending between the intrados wall and the extrados wall.

7. The blade according to claim 1, wherein the intrados wall has at least one orifice connecting the at least one inner through cavity to the outside of the airfoil.

8. The blade according to claim 1, wherein the airfoil further comprises a second internal cooling circuit identical to the first internal cooling circuit.

9. The blade according to claim 1, further comprising a tub at a radially outer end, and wherein the first internal cooling circuit further includes an auxiliary extrados cavity extending radially along the extrados wall and configured to supply a cooling cavity of the tub.

10. A turbomachine comprising a blade according to claim 1.

11. The blade according to claim 8, wherein the first inner wall of the first internal cooling circuit is merged with the second inner wall of the second internal cooling circuit.

12. A blade for a turbine, comprising a blade root defining a radially inner end of the blade and an airfoil extending radially outwards from the blade root and having an intrados wall and an extrados wall connected to the intrados wall at a leading edge and a trailing edge of the airfoil, the airfoil comprising at least a first internal cooling circuit including at least one intrados cavity extending radially along the intrados wall and along a first inner wall arranged between the intrados wall and the extrados wall, and at least one extrados cavity extending radially along the extrados wall and along a second inner wall arranged between the intrados wall and the extrados wall, wherein the first internal cooling circuit further includes at least one inner through cavity defined between two through walls each extending between the intrados wall and the extrados wall, the at least one inner through cavity extending radially along the intrados wall and the extrados wall, wherein the at least one intrados cavity, the at least one extrados cavity and the at least one inner through cavity are fluidly connected in series, wherein the first inner wall and the second inner wall are distinct and each delimited by two through walls, each through wall extending between the intrados wall and the extrados wall.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages will be better understood upon reading the following detailed description, of embodiments of the invention given as non-limiting examples. This description refers to the appended drawings, wherein:

(2) FIG. 1 represents, in perspective, a blade for a turbine according to a first embodiment;

(3) FIG. 2 represents the blade according to the first embodiment in cross-section along the plane II-II of FIG. 1;

(4) FIG. 3 represents the blade according to the first embodiment in cross-section according to the plane III-III of FIG. 1;

(5) FIG. 4 represents the blade according to the first embodiment in cross-section according to the plane IV-IV of FIG. 1;

(6) FIG. 5 represents the blade according to the first embodiment in cross-section according to the plane V-V of FIG. 1;

(7) FIG. 6 represents the blade according to the first embodiment in cross-section according to the plane VI-VI of FIG. 1;

(8) FIG. 7 is a diagram synthesizing the flow of a coolant inside the blade according to the first embodiment;

(9) FIG. 8 schematically represents the deformations of the blade according to the first embodiment, in use, in cross-section according to the plane III-III of FIG. 1;

(10) FIG. 9 represents the blade according to the first embodiment in cross-section according to the plane IX-IX of FIG. 1;

(11) FIG. 10 is a diagram synthesizing the flow of a coolant inside a blade according to a second embodiment;

(12) FIG. 11 is a diagram synthesizing the flow of a coolant inside a blade according to a third embodiment;

(13) FIG. 12 is a diagram synthesizing the flow of a coolant inside a blade according to a fourth embodiment;

(14) FIG. 13 is a partial schematic sectional view of a turbomachine incorporating the blade according to one of the embodiments.

DETAILED DESCRIPTION OF THE INVENTION

(15) FIG. 1 represents, in perspective, an example of a hollow rotor blade 10 for a gas turbine, according to a first embodiment. Cooling air (not represented) flows inside the blade from the bottom of the root 12 of the blade into the airfoil 13, along the longitudinal direction R-R′ of the airfoil 13 (vertical direction in the figure and radial direction with respect to the axis of rotation X-X′ of the rotor), towards the tip 14 of the blade (at the top in FIG. 1), then this cooling air escapes through an outlet to join the main gas stream. The root 12 forms the radially inner end of the blade 10 and the tip 14 forms the radially outer end of the blade 10.

(16) Particularly, this cooling air circulates in an internal cooling circuit which is located inside the airfoil 13 and some branches of which lead to the tip 14 of the blade at through bores 15 provided in a tub.

(17) The body of the airfoil is profiled so that it defines an intrados wall 16 and an extrados wall 18. The intrados wall 16 has a generally concave shape and is the first one appearing facing the hot gas stream that is to say on the pressure side of the gases, through its external face, oriented upstream. The extrados wall 18 is convex and appears subsequently facing the hot gas stream that it is to say on the suction side of the gases, along its external face, oriented downstream.

(18) The intrados 16 and extrados 18 walls join at the location of the leading edge 20 and at the location of the trailing edge 22 which extend radially between the tip 14 of the blade and the top of the root 12 of the blade.

(19) As indicated previously, the airfoil 13 comprises a first internal cooling circuit which will be detailed with reference to FIGS. 2 to 9. Particularly, FIGS. 2 to 6 show successive cross-sections from the radially inner end of the airfoil 13 to its radially outer end.

(20) FIG. 3 represents the airfoil 13 in cross-section along a transverse plane. The plane III-III is located preferably between 10% and 90% of the dimension of the airfoil 13 in the longitudinal direction, preferably between 20% and 80%, more preferably between 25% and 75%.

(21) As illustrated in FIG. 3, the blade comprises cavities 31-41 separated from each other by radially extending walls. More particularly, the blade 10 comprises through walls each extending between the intrados wall 16 and the extrados wall 18, at a distance from the leading edge 20 and from the trailing edge 22. In this embodiment, the blade comprises seven through walls 51, 53, 55, 57, 59, 61, 63. As illustrated, the through walls may be substantially rectilinear in cross-section.

(22) Furthermore, the blade 10 comprises inner walls each arranged between the intrados wall 16 and the extrados wall 18 and at a distance from the intrados wall 16 and from the extrados wall 18, in this case three inner walls 43, 45, 47. As illustrated, the inner walls may be substantially rectilinear in cross-section.

(23) The inner walls connect the through walls in pairs so as to form generally H-shaped structures. More specifically, in this embodiment, the inner wall 43 connects the through walls 51 and 53, the inner wall 45 connects the through walls 55 and 57, and the inner wall 47 connects the through walls 59 and 61, whereby three generally H-shaped structures are formed, said three structures being connected to each other only by the intrados and extrados walls 16, 18.

(24) As illustrated in FIG. 3, the aforementioned generally H-shaped structures are separated, in pairs, by an inner through cavity. Thus, in this embodiment, the blade 10 comprises two inner through cavities 35, 38. The inner through cavity 35 (respectively the inner through cavity 38) is defined between two through walls 57, 59 (respectively two through walls 53, 55) belonging to distinct H-structures and extends radially along the intrados wall 16 and the extrados wall 18.

(25) Thus, the intrados wall 16, the extrados wall 18, the inner walls 43, 45, 47 and the through walls 51, 53, 55, 57, 59, 61, 63 define a plurality of cavities of which features and role will now be detailed.

(26) An upstream cavity 31 extends radially along the intrados wall 16 and the extrados wall 18 and is delimited by a through wall 51. The upstream cavity 31 is adjacent to the leading edge 20.

(27) A first supply cavity 32 is defined between the intrados wall 16, the through wall 51, the inner wall 43 and the through wall 53. Insofar as it extends radially along the intrados wall 16 and an inner wall, the first supply cavity 32 may also be called intrados cavity. The first supply cavity 32 is fluidly connected to the upstream cavity 31 for its supply with cooling air, for example by an impact device as previously defined. The first supply cavity 32 may be, for its part, supplied with cooling air via an air inlet section arranged in the blade root 12, for example a channel.

(28) The upstream cavity 31 and the first supply cavity 32 form a leading edge cooling circuit ensuring the cooling of the airfoil 13 at its leading edge 20.

(29) Similarly, a downstream cavity 40 extends radially along the intrados wall 16 and the extrados wall 18 and is delimited by a through wall 63. The downstream cavity 40 is adjacent to the trailing edge 22.

(30) A second supply cavity 39 is defined between the intrados wall 16, the through wall 61, the extrados wall 18 and the through wall 63. The second supply cavity 39 is fluidly connected to the downstream cavity 40 for its supply with cooling air, for example by a calibration as previously defined. The second supply cavity 39 may be, for its part, supplied with cooling air via an air inlet section arranged in the blade root 12, for example a channel.

(31) The downstream cavity 40 and the second supply cavity 39 form a trailing edge cooling circuit ensuring the cooling of the airfoil 13 at its trailing edge 22.

(32) The airfoil 13 further comprises a first internal cooling circuit including at least one intrados cavity, in this case which can be selected from among two intrados cavities 33, 36. The intrados cavity 33 (respectively the intrados cavity 36) extends radially along the intrados wall 16 and an inner wall 47 (respectively an inner wall 45) arranged between the intrados wall 16 and the extrados wall 18. Said inner wall 47 (respectively the inner wall 45) defining the intrados cavity 33 (respectively the intrados cavity 36) can be referred to as first inner wall. Furthermore, the intrados cavity 33 (respectively the intrados cavity 36) is delimited by the through walls 59, 61 (respectively the through walls 55, 57), the first inner wall 47 (respectively the first inner wall 45) being connected to said through walls 59, 61 (respectively to said through walls 55, 57).

(33) The first internal cooling circuit furthermore comprises at least one extrados cavity, in this case which can be selected from among three extrados cavities 37, 41, 34. The extrados cavity 37 (respectively the extrados cavity 41, respectively the extrados cavity 34) extends radially along the extrados wall 18 and an inner wall 43 (respectively an inner wall 45, respectively an inner wall 47) arranged between the intrados wall 16 and the extrados wall 18. Said inner wall 43 (respectively the inner wall 45, respectively the inner wall 47) defining the extrados cavity 37 (respectively the extrados cavity 41, respectively the extrados cavity 34) can be referred to as second inner wall. The second inner wall may be distinct or merged with the first inner wall mentioned above. In the case where the first inner wall and the second inner wall are merged, the corresponding intrados and extrados cavities may be located on either side of said first and second inner walls. For example, it may be the intrados cavity 33, the extrados cavity 34 and the inner wall 47. Conversely, in the case where the first and second inner walls are distinct, the corresponding intrados and extrados cavities are not located on either side of the same inner wall. This example can be illustrated by the intrados cavity 36 defined by the first inner wall 45 and the extrados cavity 37 defined by the second inner wall 43.

(34) Furthermore, the extrados cavity 37 (respectively the extrados cavity 41, respectively the extrados cavity 34) is delimited by the through walls 51, 53 (respectively the through walls 55, 57, respectively the through walls 59, 61), the second inner wall 43 (respectively the second inner wall 45, respectively the second inner wall 47) being connected to said through walls 51, 53 (respectively to said through walls 55, 57, respectively to said through walls 59, 61).

(35) In addition, the first cooling circuit further includes at least one inner through cavity, in this case which can be selected from among three inner through cavities 38, 35, 39. The inner through cavity 38 (respectively 35, respectively 39) is defined between two through walls 51, 53 (respectively 55, 57, respectively 59, 61) and extends radially along the intrados wall 16 and the extrados wall 18.

(36) Thus, in this first embodiment, a first internal cooling circuit can be identified including at least one intrados cavity 33 extending radially along the intrados wall 16 and a first inner wall 47 arranged between the intrados wall 16 and the extrados wall 18, at least one extrados cavity 34 extending radially along the extrados wall 18 and a second inner wall 47 arranged between the intrados wall 16 and the extrados wall 18, and in this case merged with the first inner wall, the first cooling circuit further including at least one inner through cavity 35 defined between two through walls 57, 59 each extending between the intrados wall 16 and the extrados wall 18, at a distance from the leading edge 20 and from the trailing edge 22, the inner through cavity 35 extending radially along the intrados wall 16 and the extrados wall 18. The first inner wall 47 (and consequently the second inner wall) is connected to one of said through walls, namely the through wall 59.

(37) In this embodiment, the airfoil 13 comprises another first internal cooling circuit including at least one intrados cavity 36 extending radially along the intrados wall 16 and a first inner wall 45 arranged between the intrados wall 16 and the extrados wall 18, at least one extrados cavity 37 extending radially along the extrados wall 18 and a second inner wall 43, arranged between the intrados wall 16 and the extrados wall 18, the first cooling circuit further including at least one inner through cavity 38 defined between two through walls 53, 55 each extending between the intrados wall 16 and the extrados wall 18, at a distance from the leading edge 20 and from the trailing edge 22, the inner through cavity 38 extending radially along the intrados wall 16 and the extrados wall 18. The first inner wall 45 and the second inner wall 43 are each connected to one of said through walls, namely respectively connected to the through walls 53, 55.

(38) FIG. 2 illustrates a section of the airfoil 13 radially further inwards than the section of FIG. 3 (see FIG. 1). As illustrated in FIG. 2, at a radially inner portion of the airfoil, a passage 53a is arranged in the through wall 53 so as to fluidly connect the extrados cavity 37 to the inner through cavity 38. Furthermore, a passage 59a is arranged in the through wall 59 so as to fluidly connect the extrados cavity 34 to the inner through cavity 35. Thus, the extrados cavity 34 (respectively the extrados cavity 37) and the inner through cavity 35 (respectively the inner through cavity 38) are fluidly connected in series, as illustrated by the arrows representing the passage of fluid from the cavities 34 to 35 (respectively from the cavities 37 to 38).

(39) More generally, a passage 59a (respectively a passage 53a) is arranged in a radially inner portion of the blade 13 so as to fluidly connect the extrados cavity 34 (respectively the extrados cavity 37) and the inner through cavity 35 (respectively the inner through cavity 38).

(40) FIG. 4 illustrates a section of the airfoil 13 radially further outwards than the section of FIG. 3 (see FIG. 1). As illustrated in FIG. 4, at a radially outer portion of the airfoil, a passage 47b is arranged in the inner wall 47 so as to fluidly connect the intrados cavity 33 to the extrados cavity 34. Thus, the intrados cavity 33 and the extrados cavity 34 are fluidly connected in series, as illustrated by the arrow representing the passage of fluid between said cavities. More generally, a passage 47b is arranged in a radially outer portion of the airfoil 13 so as to fluidly connect the intrados cavity 33 and the extrados cavity 34.

(41) In view of the above, the intrados cavity 33, the extrados cavity 34 and the inner through cavity 35 are fluidly connected in series, in this order.

(42) FIG. 5 illustrates a section of the airfoil 13 radially further outwards than the section of FIG. 4 (see FIG. 1). As can be seen in FIG. 5, a bottom wall 64 closes the radially outer end of the intrados cavity 33, of the extrados cavity 34, of the inner through cavity 35, of the second supply cavity 39 and of the downstream cavity 40. Furthermore, a bottom wall 66 closes the radially outer end of the inner through cavity 38. On the other hand, the upstream cavity 31, the first supply cavity 32, the intrados cavity 36, the extrados cavity 37 and the extrados cavity 41 extend radially beyond the bottom walls 64, 66.

(43) FIG. 6 illustrates a section of the airfoil 13 radially further outwards than the section of FIG. 5 (see FIG. 1). As can be seen in FIG. 6, a passage 68 fluidly connects the intrados cavity 36 to the extrados cavity 37 without passing through the inner through cavity 38, thanks to the bottom wall 66. Thus, the intrados cavity 36 and the extrados cavity 37 are fluidly connected in series, as illustrated by the arrow representing the passage of fluid between said cavities. In this case, the passage 68 overhangs the inner through cavity 38. More generally, a passage 68 is arranged in a radially outer portion of the airfoil 13 so as to fluidly connect the intrados cavity 36 and the extrados cavity 37.

(44) In view of the foregoing, the intrados cavity 36, the extrados cavity 37 and the inner through cavity 38 are fluidly connected in series, in that order.

(45) On the other hand, the extrados cavity 41 may serve as an auxiliary extrados cavity for the supply of a cooling cavity 42 of the tub, positioned under the tub in a radial direction. The positioning of the auxiliary extrados cavity 41 on the extrados side, away from the leading edge and from the trailing edge, preferably in an intermediate position between the leading edge 20 and the trailing edge 22, makes it possible to limit the heating of the cooling air during its flow in the auxiliary extrados cavity 41 and to deliver to the cooling cavity 42 of the tub a fluid as cold as possible, for an effective cooling of the tip 14. Because of the bottom wall 64, the cooling cavity 42 is supplied only by the auxiliary extrados cavity 41 and fluidly separated from the intrados cavity 33, from the extrados cavity 34, from the inner through cavity 35, from the second supply cavity 39 and from the downstream cavity 40.

(46) FIG. 7 schematizes, from the section of FIG. 3, the circulation of the cooling air in the embodiment previously described. The cavities fluidly connected in series together have been represented with identical densities of dots. The arrows indicate a possible direction of circulation of the fluid, this direction being determined according to the following.

(47) In the present embodiment, air inlet sections may be provided in the blade root 12 for the supply of the cooling air cavities. For example, an air inlet section may be provided for at least one or each of the following cavities: the first supply cavity 32, the intrados cavity 33, the intrados cavity 36, the second supply cavity 39, the auxiliary extrados cavity 41.

(48) The direction of circulation of the coolant obtained under these conditions is represented in FIG. 8. As can be seen from FIG. 8, the coolant circulates from the root 12 toward the tip 14 in the supply cavities 32, 39, in the intrados cavities 33, 36, in the inner through cavities 35, 38 and in the downstream cavity 40, and from the tip 14 toward the root 12 in the extrados cavities 34 and 37.

(49) When the rotor on which the blade 10 is mounted rotates in the direction S represented in FIG. 8, the cooling air is further subjected to the Coriolis force. Given the direction of circulation described above, in the supply cavities 32, 39, in the intrados cavities 33, 36, in the inner through cavities 35, 38 and in the downstream cavity 40, the air is pressed against the intrados side of said cavities, which is illustrated in solid lines in FIG. 8. In contrast, in the extrados cavities 34, 37, the air is pressed against the extrados side of said cavities.

(50) Due to this cooling and to the arrangement of the through walls and inner walls, the thermo-mechanical stresses accumulated in the airfoil 13 in operation are greatly reduced. Indeed, FIG. 8 also schematically illustrates the deformations undergone by the structure of the airfoil 13. As can be seen from FIG. 8, the intrados and extrados walls 16, 18 deform further than the inner walls 43, 45, 47, due to their higher temperature in operation. The presence of inner through cavities such as the cavities 35, 38—and to a certain extent the second supply cavity 39 which also meets the definition of an inner through cavity within the meaning of the present disclosure—makes it possible to accommodate this differential expansion and minimize the stresses within the airfoil 13, as can be deduced from the curvature taken by the through walls.

(51) In addition, the presence and the relatively small deformation of the inner walls 43, 45, 47 make it possible to properly support the bottom walls 64, 66, which extend transversely. Indeed, being at a temperature lower than the intrados and extrados walls 16, 18, the inner walls 43, 45, 47 have, all things being equal, better mechanical properties, are stiffer and better withstand the stresses that result from the centrifugal force related to the rotation of the turbine. This recovery of the forces by the inner walls 43, 45, 47 also relieves the intrados and extrados walls 16, 18, of which lifetime increases consequently.

(52) FIG. 9 is substantially identical to FIG. 3, except that the section of the airfoil 13 considered (plane IX-IX in FIG. 1) is selected to show the presence of orifices allowing the circulation of the air within the airfoil 13 and toward the outside of the airfoil 13.

(53) An orifice 62, preferably a plurality of orifices, is arranged in the through wall 51, between the first supply cavity 32 and the upstream cavity 31. The orifice 62 allows supplying the upstream cavity 31 with cooling air indirectly, as previously disclosed.

(54) An orifice 69, preferably a plurality of orifices, is arranged in the through wall 63, between the second supply cavity 39 and the downstream cavity 40. The orifice 69 allows supplying the downstream cavity 40 with cooling air indirectly, as previously disclosed.

(55) Furthermore, discharge orifices such as the orifices 31c, 35c, 38c, 40c are provided in the intrados wall 16, opening respectively onto the upstream cavity 31, the inner through cavities 35, 38 and the downstream cavity 40. The discharge orifices 31c, 35c, 38c, 40c may be configured to create a protective fluid film on the outer surface of the airfoil 13, downstream of said orifices. To this end, the orifices 31c, 35c, 38c, 40c can be oriented towards the trailing edge 22. In this case, said orifices respectively create protective films 32′, 33′, 36′ and 40′ respectively protecting the cavities 32, 33, 36, 40.

(56) Similarly, discharge orifices 31d may be provided in the extrados wall 18, in particular at the leading edge. In this case, the discharge orifices 31d connect the upstream cavity 31 to the outside of the airfoil 13 and allow the creation of a protective fluid film 37′ intended to protect the extrados cavity 37.

(57) As seen from FIG. 9, the cavities and the discharge orifices are provided so that a circuit protects itself. For example, the air entering through the intrados cavity 36 circulates towards the extrados cavity 37 and then the inner through cavity 38, and is then discharged through the discharge orifice 38c where it contributes to creating the protective fluid film 36′ which protects the intrados cavity 36. It is advantageous for this purpose that the air circulates generally in counter-flow in the cavities that is to say from the trailing edge toward the leading edge. It is the case in this example, since the air outlet cavity, namely the inner through cavity 38, is located upstream of the air inlet cavity, namely the intrados cavity 36. The same applies for the leading edge cooling circuit and for the internal cooling circuit formed by the cavities 33-35.

(58) The blade 10 may be manufactured, according to the method known per se, from lost-wax casting. To do so, cores are previously manufactured, which cores occupy the space to be arranged for the cavities during the production of the mold.

(59) The cores corresponding to the cavities 33-35 on the one hand, 36-38 on the other hand can be manufactured according to any suitable method, for example by molding with possible use of inserts in the mold, or by additive manufacturing.

(60) Holding of the cores during the manufacture of the mold can be carried out in a manner known to those skilled in the art. The cores corresponding to the cavities 33-35 on the one hand, 36-38 on the other hand, can be supported by two supports located in the root 12. In order to avoid an excessive number of supports and simplify the arrangement of the root 12 it is possible to provide only one root per core, the holding being completed by a delocalized appendage. This appendage is preferably provided to form, in the final blade, an opening which is then likely to be resealed by a brazed ball.

(61) After the pouring of the metal and the destruction of the cores, the cavities may undergo a dedusting operation. To do so, it is possible to provide in the airfoil a dedusting hole, for example at the blade tip. If necessary, for the purpose of dedusting the through cavities 35, 38 respectively closed by the bottom walls 64, 66, the shape of the cooling cavity 42 of the tub and/or of the passage 68 may be adapted to allow the passage of a rod secured to the core and the production of the dedusting hole directly from casting, and/or to allow the production of said hole by machining after casting of the airfoil. The dedusting hole can, possibly, also allow the discharge of debris in operation.

(62) FIGS. 10 to 12 present a blade for a turbine in other embodiments. In these figures, the elements corresponding or identical to those of the first embodiment will receive the same reference sign, within the hundreds digits, and will not be described again.

(63) FIGS. 10 to 12 are schematic views similar to that of FIG. 7 and represented according to the same conventions, described above.

(64) In the airfoil 113 according to a second embodiment represented in FIG. 10, the cavity 137 is used as auxiliary extrados cavity. The cavity 141 is used as an extrados cavity fluidly connected in series between the intrados cavity 136 and the inner through cavity 138. The bottom wall 66 described in relation to FIG. 5 can be extended to close the intrados cavity 136 and the extrados cavity 141, given that it is not necessary, in this embodiment, to provide a passage similar to the passage 68 described in relation to FIG. 6.

(65) Thus, in this embodiment, the airfoil comprises a first internal cooling circuit including the intrados cavity 133, the extrados cavity 134 and the inner through cavity 135, and a second internal cooling circuit including the intrados cavity 136, the extrados cavity 141 and the inner through cavity 138. Within the meaning of the present disclosure, the first and second internal cooling circuits of this embodiment are identical. Furthermore, the cavities 131, 132, 139, 140 of the leading edge and trailing edge cooling circuits are unchanged.

(66) This embodiment allows providing a cooling cavity of the tub that is larger than the cooling cavity 42 described above and allows a similar manufacture of the cores of the internal cooling circuits.

(67) In the airfoil 213 according to a third embodiment represented in FIG. 11, the first internal cooling circuit formed by the cavities 236-238 is identical to the first internal cooling circuit according to the first embodiment (cavities 36-38). However, the cavity 234 is used as an auxiliary extrados cavity. The cavity 241 is used as an extrados cavity fluidly connected in series between the intrados cavity 233 and the inner through cavity 235. Consequently, in order to arrange a passage between the intrados cavity 233 and the extrados cavity 241 that does not pass through the inner through cavity 235 (a passage similar to the passage 68 described in relation to FIG. 6), it is necessary, with respect to the first embodiment, to modify the bottom wall 64 described in relation to FIG. 5 so as to allow the intrados cavity 233 and the auxiliary extrados cavity 234 to extend through said bottom wall.

(68) Thus, in this embodiment, the airfoil comprises a first internal cooling circuit including the intrados cavity 233, the extrados cavity 241 and the inner through cavity 235, and a second internal cooling circuit including the intrados cavity 236, the extrados cavity 237 and the inner through cavity 238. Within the meaning of the present disclosure, the first and second internal cooling circuits of this embodiment are identical. In addition, the first inner wall 245 of the first internal cooling circuit is merged with the second inner wall of the second internal cooling circuit.

(69) This embodiment allows merging the air inlet section of the auxiliary extrados cavity 234 with the air inlet section of the second supply cavity 239, which facilitates the arrangement of the airfoil root and its manufacture.

(70) An airfoil 313 according to a fourth embodiment, represented in FIG. 12, is similar to the airfoil 213 according to the third embodiment, except that it comprises only a first internal cooling circuit, formed in this case by the cavities 336, 337 and 338. This embodiment can be advantageously implemented for airfoils of smaller size than those described above. To further reduce the size of the airfoil 313, it would be possible to unify on the one hand the upstream cavity 331 with the first supply cavity 332, and/or on the other hand the downstream cavity 340 with the second supply cavity 339. While the previous embodiments have inner and through walls configured to form a triple H structure, the inner and through walls of the blade 313 according to the fourth embodiment form a double H shape structure. The effects obtained by such a structure and described with respect to the other embodiments are transposed mutatis mutandis.

(71) The blade 10 according to any one of the embodiments described may be a movable blade for a turbine of a turbomachine 100, as represented schematically in FIG. 13.

(72) Although the present invention has been described with reference to specific examples of embodiment, modifications can be made to these examples without departing from the general scope of the invention as defined by the claims. For example, although the flow of fluid in the cavities has been described along a certain direction corresponding to a preferred embodiment, it will be apparent to those skilled in the art that it is possible to change the radial position of the passages between cavities and/or to rearrange the air inlet sections of the blade root so as to impose a direction of circulation of the coolant different from the one described in the present disclosure.

(73) In addition, although the cavities have been represented smooth and empty, it is possible to provide flow disruptors therein in order to increase heat exchanges.

(74) In general, individual features of the various illustrated/mentioned embodiments can be combined in additional embodiments. Consequently, the description and drawings should be considered in an illustrative rather than restrictive sense