TURBINE BLADE WITH OPTIMIZED COOLING CHANNELS

Description

TECHNICAL FIELD

[0001] The invention relates to a turbine blade for an aircraft engine of the turbomachine type, such as a turbojet or a turboprop. STATE OF PRIOR ART

[0002] In such an engine, outside air is admitted through an inlet sleeve to pass through a fan having a series of rotating blades before splitting into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow is then compressed before entering a combustion chamber, after which it expands through a set of turbines before being exhausted to the rear, generating thrust. The secondary flow is propelled directly to the rear by the fan to generate additional thrust.

[0004] The expansion in the turbines, which drives the compressor and the fan, takes place at high temperature because it occurs immediately after combustion. This turbine is therefore designed and sized to operate under severe conditions of temperature, pressure and fluid flow.

[0005] Each turbine consists of a succession of stages, each comprising a series of radially oriented blades regularly spaced around an engine rotation shaft. This central shaft carries the rotating elements of the turbine as well as the rotating elements of the compressor and the fan.

[0006] Concretely, the turbine blades which are subjected to the most severe conditions are those of the first expansion stages of this turbine, namely the stages closest to the combustion zone and which are commonly called high pressure stages.

[0007] Generally speaking, increased performance requirements and evolving regulations are leading to the design of smaller engines operating in increasingly harsh environments. This means increasing the durability and performance of high-pressure turbine blades, particularly with regard to their temperature resistance.

[0008] However, existing improvements in the materials and coatings of these blades are not sufficient to enable them to withstand the high temperatures that can be reached by the flow downstream of the combustion chamber. This situation leads to reconsidering the cooling of these blades to improve it so that they can withstand these new operating conditions.

[0009] This cooling is ensured by circulating fresh air inside these blades, which is taken from the turbojet upstream of combustion. This air is admitted at the base of the blade, to travel along an internal circuit of the blade in order to cool it, and it is evacuated from the blade by holes passing through the wall of this blade and distributed on this wall. These holes are used to evacuate the cooling air, but they also create on the external surface of the blade a film of air colder than the air from the combustion, which also helps to limit the temperature of the blade.

[0010] To increase cooling efficiency, the interior regions of the blade through which the cooling air circulates have artifices, i.e. internal reliefs which disturb the fluid flow of the cooling air to increase the heat transfer from the blade wall to this cooling air circulating in the internal ducts of the blade.

[0011] These traditional cooling architectures are penalized by the fact that the length of the internal circuit of the blade gives rise to air that is too highly heated when it reaches the end of this circuit, so that its cooling efficiency is limited in the end-of-path regions, and in particular at the level of the blade tip where, on the contrary, we seek to obtain increased cooling efficiency.

[0012] In practice in known blades, in particular documents EP2119873A2, EP1065343A2, WO03042503A1, EP1895098B1, US2008080979A1 and EP1882819B1, the cooling efficiency proves to be inadequate.

[0013] The aim of the invention is to propose a blade structure making it possible to improve the cooling efficiency of this blade. SUMMARY OF THE INVENTION

[0014] To this end, the invention relates to a turbomachine turbine blade and molding means for manufacturing such a blade, as defined in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] There figure 1 is a schematic view of a dual-flow turbojet engine in longitudinal section; The figure 2 is a perspective view of a turbojet turbine blade shown in the figure 1 ; There figure 3is a perspective view showing the hollow internal parts of a turbine blade according to a first embodiment of the invention not covered by the claims; The figure 4 is a perspective view showing the hollow internal parts of a turbine blade according to a second embodiment of the invention; The Figure 5 is a perspective view showing the hollow internal parts of a turbine blade according to a third embodiment of the invention; The figure 6 is a perspective view showing the hollow internal parts of a turbine blade according to a fourth embodiment of the invention; The figure 7 is a perspective view showing the hollow internal parts of a turbine blade according to a fifth embodiment of the invention; The figure 8is a perspective view showing the hollow internal parts of a turbine blade according to a sixth embodiment of the invention not covered by the claims; DETAILED PRESENTATION OF SPECIFIC EMBODIMENTS

[0016] As visible on the figure 1 , a front part of a dual-flow turbojet 1 comprises an inlet sleeve 2 into which the air is admitted before being sucked in by the blades of a fan 3. After passing the fan region, the air divides into a central primary flow and a secondary flow which surrounds the primary flow.

[0017] The primary air flow then passes through a first compressor 4 located immediately after the blower 3 while the secondary flow is propelled backwards to directly generate additional thrust by being blown around the primary flow.

[0018] The primary flow then passes through a second compression stage 6, before reaching a chamber 7 where it combusts, after injection and vaporization of a fuel. After combustion, this primary flow expands in a high-pressure turbine 8 then in a low-pressure turbine (not shown) to rotate the compression stages and the fan, before being expelled towards the rear of the engine to generate thrust.

[0019] The engine 1 and its components have a shape of revolution around a longitudinal axis AX. It comprises in particular an external casing 9 also having a shape of revolution and extending from the front of the engine where it delimits the air intake sleeve, to the rear part where it delimits the duct through which the primary and secondary flows are evacuated, the front and the rear to be considered relative to the direction of advance of the aircraft equipped with this turbojet. This casing 9 supports the rotating components located in the center of the engine and which include a rotating shaft carrying the fan blades as well as the compression stages and the turbine with their blades.

[0020] Such a dawn, which is marked by 11 on the figure 2 , comprises a foot P by which it is fixed to a rotating body not shown, called a turbine disk, and a blade 12 carried by this foot P and constituting the aerodynamic part of this blade. As visible on the figure 2 , the blade 11 comprises between the root P and the blade 12 an intermediate region 13 called platform.

[0021] The assembly formed by the foot P and the blade 12 is a single, hollow, single-piece cast piece comprising internal ducts through which cooling air circulates. These internal ducts, not visible in the figure 2 have intake vents opening on the lower face 14 of the foot P and through which these conduits are supplied with fresh air. The hollow wall of the blade 12 has through holes and slots through which the cooling air is evacuated.

[0022] The blade 12 has a twisted left shape having a substantially rectangular outline, approaching a parallelepiped. It comprises a base 16 by which it is connected to the root P and which extends approximately parallel to the axis of rotation AX. It also comprises a leading edge 17 oriented radially relative to the axis AX and located at the upstream AM of the blade, that is to say the front region of this blade, relative to the direction of advance of the engine with which it is equipped in service. This blade also comprises a trailing edge 18 oriented approximately parallel to the leading edge 17 while being spaced from it along the axis AX to be located at the downstream AV or rear region of the blade. It also comprises a tip S approximately parallel to the base 16 and spaced from it in a radial direction relative to the axis AX.

[0023] The two main walls of this blade are its intrados wall 21, which is the wall visible in the figure 2, and its extrados wall which is the opposite wall spaced from the intrados wall, and which is not visible in the figure 2 because it is masked by the intrados wall 21. The intrados and extrados walls are joined at the leading edge 17, at the trailing edge 18 and also in the region of the tip S of this blade. These walls are spaced from each other at the base 16 to allow the admission of cooling air into the internal region of the blade.

[0024] The leading edge 17 has a curved shape and is provided with a series of cooling holes 22 passing through the wall of the blade in this region. The trailing edge 18 has a tapered shape, and it comprises a series of cooling slots 23. These slots 23 are slots of short lengths extending along the span direction and which are spaced from each other while being located in the extension of each other at a short distance from the trailing edge.

[0025] Each slot 23 passes through the blade wall to take cooling air from inside this blade and blow it onto the intrados wall at the trailing edge. In addition, the trailing edge is provided with external ribs oriented parallel to the axis AX to channel the cooling air coming from these slots.

[0026] In operation, the fluid in which this blade 11 is located moves relative to it from the leading edge 17 to the trailing edge 18 along the intrados 21 and the extrados. The intrados wall which is subjected to significant heating in operation, comprises a series of holes 24 substantially parallel to the leading edge 17 while being located downstream of this leading edge, and another series of holes 26 substantially parallel to the trailing edge 18 while being located upstream of this trailing edge 18 and the slots 23 which it comprises. The series of holes 24 and 26 thus extend one and the other in the span direction EV of the blade, which is the radial direction relative to the axis AX.

[0027] The region of the tip S of the blade 11 has, unlike the leading edge 17 and the trailing edge 18, a certain thickness, and it also has a shape delimiting a hollow portion called a bathtub.

[0028] More concretely, this summit S has a closing wall which connects the intrados and extrados walls, this closing wall having an orientation which is generally perpendicular to the intrados and extrados walls and parallel to the axis AX, which corresponds to an orientation perpendicular to the span direction EV. This closing wall which is not visible on the figure 2 is located set back towards the axis AX relative to the free edge of the intrados wall and the free edge of the extrados wall, so that it constitutes, together with these edges, a hollow portion open in the direction opposite to the axis AX.

[0029] A series of additional holes 27 passing through the intrados wall is provided along the apex S to ensure significant cooling of this blade apex which is subject to significant stresses due to the fact that it constitutes the part having the highest speed relative to the fluid.

[0030] The series of holes 27 extends parallel to the closing wall, and the blade additionally includes holes not visible on the figure 2 which pass through the closing wall to open into the hollow portion called the bathtub which is at the top of the blade.

[0031] As mentioned above, such a blade is a hollow, one-piece part. It is manufactured by casting a metallic material, using a set of cores to delineate the internal ducts of its hollow portion as well as rod portions to form its through holes. The cores, rods and the like are removed once the casting operation is complete, typically with a chemical etching process capable of dissolving these elements without altering the cast material.

[0032] The following figures show internal regions of the blade according to the invention which are represented therein by the shapes of the cores used to manufacture this blade. In other words, the shapes which are in relief in the following figures constitute representations of the hollow shapes of the blade according to the invention.

[0033] The idea behind the invention is to improve the cooling of the blade in the region of the intrados wall which is in the vicinity of the trailing edge and the tip of the blade, since in practice this region is the first to deteriorate during the life of a blade.

[0034] This is achieved by providing in the blade tip region an upper cavity extending from the front to the rear of the blade and which is supplied directly with air from the blade root by a supply duct from this upper cavity.

[0035] The air taken from the root thus travels directly, in a substantially straight line, to the upper cavity. The length of the path taken by this air, in the supply duct, to reach the upper cavity is thus less than or equal to the length of the blade in the span direction EV. In other words, by providing a direct supply, this duct makes it possible to minimize the heating of the air supplied to the upper cavity.

[0036] In the first embodiment, not covered by the claims, corresponding to the figure 3 , this supply duct is formed by a leading edge cooling ramp located upstream. In the other embodiments, corresponding to the figures 4 to 8 , this supply duct is constituted by a central duct of the blade, that is to say located approximately halfway between its leading edge and its trailing edge.

[0037] In the first embodiment of the invention, the blade, which is marked 31 in the figure 3 where it is represented, thus comprises internal ducts arranged to bring into the region of the tip of the blade on the intrados side, the coolest possible cooling air so as to increase the cooling efficiency there.

[0038] The interior of this blade 31 thus comprises in its upstream region, identified by AM, an upstream ramp 32 oriented according to its span direction EV and which runs along its leading edge. This upstream ramp 32 directly supplies an upper cavity 33 of the blade, while supplying fresh air to cooling holes passing through the portion of wall forming the leading edge of the blade. This upstream ramp 32 extends from the root of the blade, identified by P, and by which it is supplied with air directly, to the top of the blade identified by S.

[0039] The upper cavity 33 which is located near the top extends along the closing wall of this blade 31 and along its intrados wall, from the front to the rear of the blade which is identified by AV. These two walls are not visible in the figure 3 since it is a representation of the hollow regions of this dawn.

[0040] The entire part of the tip S of the blade 31 which is located on the side of its intrados, over substantially its entire length and in particular up to the downstream end of this tip S is thus supplied with air by the upper cavity 33 which is itself supplied by the upstream ramp 32 forming a conduit.

[0041] The upper cavity 33 reaches the trailing edge of the blade, in the downstream region AV, to supply fresh air to at least one cooling slot of this trailing edge, namely the slot closest to the tip which corresponds to one of the most severely stressed regions of the blade.

[0042] This upper cavity 33 runs along the intrados wall, extending over a width less than the width or thickness of the blade, that is to say it has a width less than the distance separating the intrados and extrados walls. It is delimited laterally by a first face 34 which runs along the intrados and a second face 36 spaced from the first. The first face 34 and the second face 36 are joined at the front and rear of this upper cavity.

[0043] The upper cavity 33 is delimited vertically by a bottom 37 parallel to the closing wall and spaced from it and by an upper face 38 which is the lower face of the closing wall.

[0044] In the region of the tip S of the blade, the intrados wall may comprise through holes, not shown, allowing the upper cavity 33 to additionally cool the external face of the intrados wall in this region.

[0045] The interior of the blade 31 also includes a downstream ramp 41 extending along the trailing edge from the root P to the region of the apex S to terminate under the rear part of the upper cavity 33. This downstream ramp 41 feeds a series of trailing edge cooling slots, not visible in the figure 3 .

[0046] The majority of the cooling slots of the trailing edge are thus supplied with air by the downstream ramp 41, but it is the upper cavity which supplies the slot(s) closest to the apex S, which is a region subject to greater thermal stresses. The slots close to the apex are thus supplied with cooler air and / or having a greater flow rate than the others.

[0047] The dawn of the figure 3further comprises a first central duct 42, a second central duct 43 and a downstream duct 44, oriented in the span direction, and communicating with each other in a so-called trombone arrangement. The first central duct 42 which runs along the upstream ramp 32 collects air at the level of the foot of the blade, and it communicates at the level of the tip S with the second central duct 43 to supply it with air.

[0048] This second central duct 43 is connected at the base of the blade with the downstream duct 44 to supply it with air. This downstream duct 44 extends in a straight line from the root P to the top S, parallel to the downstream ramp 41 which it runs along while being located upstream of this downstream ramp 41.

[0049] As visible in the figure, the end of the downstream duct 44 ends in the region of the apex S by running along the second face 36 of the upper cavity 33 to bypass it. The intrados wall can be provided with through holes allowing the ducts 42, 43, 44 to supply cooling air to the external face of this wall to cool it by forming an external film there.

[0050] The intrados wall may comprise, at the level of the downstream duct 44, through holes through which this downstream duct 44 supplies air cooling the external face of the intrados wall upstream of the trailing edge of the blade.

[0051] In addition to or alternatively to these cooling holes in the intrados wall upstream of the trailing edge, the downstream duct 44 can supply the downstream ramp 41 via a series of calibrated passages (not shown) that are regularly spaced apart from each other along the span direction EV. In this case, instead of being supplied by the second duct 43, the downstream duct 44 then directly collects cooling air at the level of the blade root, so that the air it supplies to the downstream ramp is as cool as possible.

[0052] Thus, depending on the design choice, the downstream ramp 41 can be supplied in a calibrated manner by the downstream conduit 44, or, on the contrary, it can be supplied directly in the region of the foot of the blade.

[0053] These passages are then calibrated to approximately achieve a desired airflow rate in each trailing edge cooling slot. The desired airflow rate for a given slot is conditioned by the trailing edge thermal constraints in the region cooled by that slot.

[0054] In a second embodiment of the invention shown in figure 4 , the blade which is identified by 51 comprises an upper cavity 52 which is supplied directly by a central conduit 53 entirely dedicated to this upper cavity 52. ​​Thus, unlike the first embodiment of the figure 3 , the supply duct of the upper cavity does not participate in the cooling of the leading edge.

[0055] In this dawn 51 of the figure 4, a first lateral cavity 54 is also provided along the intrados wall, and a second lateral cavity 56 along the extrados. These two lateral cavities thermally insulate the central duct as well as an upstream duct for calibrated supply of a cooling ramp for the leading edge of the blade, the intrados and extrados walls which are heated by the gas flows surrounding the blade.

[0056] The upper cavity 52 of this blade 51 has a shape substantially identical to that of the blade 31 of the figure 3. It is located near the apex S, extends along the closing and intrados walls, from the front to the rear of the blade. Here too, the entire part of the apex S located on the intrados side is supplied with air by this upper cavity 52, over substantially its entire length up to the rear end. This upper cavity 52 also extends to the trailing edge, to supply fresh air at least to the slot closest to the apex S, marked by 55, and possibly some adjacent slots.

[0057] The thickness of this upper cavity 52 is also less than the thickness of the blade. It is delimited laterally by a first face 57 which runs along the intrados and a second face 58 spaced from the first face, these faces being joined at the front and at the rear. In the vertical direction, the upper cavity 52 is delimited by a bottom 59 parallel to the closing wall, and by the lower face 61 of this closing wall.

[0058] In the blade tip region S, the intrados wall may also have through holes to cool the outer face of the intrados wall in the tip region.

[0059] The central duct 53 feeds this upper cavity 52 by extending from the root P of the blade through which it is supplied with air, to the top of this blade, where it opens entirely into the bottom 59 of this upper cavity 52.

[0060] The leading edge of the blade 51 is cooled by an upstream ramp 62 which extends from the base of the blade to the tip S, but which is supplied not directly by the root, but by an upstream duct 63 in a calibrated manner. This calibrated supply is ensured by calibrated passages 64 regularly spaced along the span direction EV of the blade and which each connect the upstream duct 63 to the upstream ramp 62. Each passage 64 has a calibrated diameter, that is to say chosen at the design stage to obtain in the area of ​​the ramp 62 that it supplies a desired air flow which is conditioned by the thermal of the blade in this region.

[0061] The blade wall has holes in the leading edge region (not shown) through which the air flowing in the ramp passes through the wall to cool the outer face of the leading edge.

[0062] As visible in the figure 4, the first lateral cavity 54 has a small thickness, and it extends from the foot P to the region of the summit S while having a generally rectangular outline. This first lateral cavity 54 ends under the upper cavity 52 so as not to cover it. It has a width sufficient to mask or cover the central conduit 53 as well as the upstream conduit 63 which runs along this central conduit.

[0063] Similarly, the second lateral cavity 56 also has a small thickness, and it extends from the foot P to the region of the apex S but covering the upper cavity 52. ​​This second lateral cavity has a generally rectangular outline, having a sufficient width to mask or cover the central duct as well as the upstream duct 63 and the upper cavity 52 on the extrados side.

[0064] Thanks to these two lateral cavities, the air which is supplied to the upper cavity 52 by the central duct 53 is kept cool during its travel in this duct, thanks to the thermal screens which the lateral cavities 54 and 56 form. Similarly, the air which is supplied by the upstream duct 63 is also kept cool during its travel in this upstream duct.

[0065] As indicated above, the cooling slot(s) of the trailing edge located in the region of the apex S are supplied with air by the upper cavity 52. ​​The other slots of the trailing edge, identified by 67, are supplied by a downstream ramp 66 which extends from the foot P, where it is supplied directly via this foot, to the region of the apex S to terminate under the rear part of the upper cavity 52.

[0066] The slots 67 are thus supplied with air by the downstream ramp 66, but it is the upper cavity 52 which supplies the slot(s) closest to the top S with cooler air and / or having a higher flow rate.

[0067] In the third embodiment of the invention which is shown in the Figure 5 , the blade which is identified by 71 also comprises an upper cavity 72 supplied by a dedicated central duct 73 which is thermally insulated by two lateral cavities 74 and 76. These two lateral cavities also isolate an upstream duct of calibrated supply of a cooling ramp of the leading edge of the blade. But in this third embodiment, the two lateral cavities 74 and 76 are joined in the rear or downstream part of the blade to envelop this central duct 73 over three quarters of its circumference, so as to offer better thermal insulation for this duct 73.

[0068] The upper cavity 72 has a shape substantially identical to that of the blades of the figures 3 And 4 . It is located near the apex S, extends along the closing and intrados walls, from the front to the rear of the blade. The entire part of the apex S located on the intrados side is supplied by this upper cavity 72, over its entire length up to the rear end. This upper cavity 72 also extends to the trailing edge, to supply at least the slot closest to the apex S, marked by 75, and possibly some adjacent slots.

[0069] The thickness of this upper cavity 72 is also less than the thickness of the blade. It is delimited laterally by a first face 77 which runs along the intrados and a second face 78 spaced from the first, these faces being joined at the front and at the rear. In the vertical direction, the upper cavity 72 is delimited by a bottom 79 parallel to the closing wall, and by the lower face 81 of this closing wall. In the region of the tip S of the blade, the intrados wall may also have through holes for cooling the external face of the intrados wall in the tip region.

[0070] The central duct 73 feeds this upper cavity 72 by extending from the foot of the blade through which it is supplied with air, to the top S, where it opens entirely into the bottom 79 of the upper cavity.

[0071] The leading edge of the blade 71 is cooled by an upstream ramp 82 which extends from the base of the blade to the tip S, and which is supplied by an upstream duct 83 in a calibrated manner by means of calibrated passages regularly spaced along the span direction EV of the blade and which each connect the upstream duct to the upstream ramp. The wall of the blade has holes in the region of the leading edge, not shown, through which the air from the ramp passes through the wall to cool the external face of the leading edge.

[0072] The first lateral cavity 74 has a small thickness and extends from the foot to the region of the apex S, having a generally rectangular outline. It ends below the upper cavity 72 without covering it. It has a width sufficient to mask or cover the central conduit 73 as well as the upstream conduit 83 which runs alongside this central conduit.

[0073] The second lateral cavity 76 also has a small thickness, and it extends from the foot to the region of the apex S but covering the upper cavity 72. It has a generally rectangular outline, having a sufficient width to mask or cover the central conduit 73 and the upstream conduit 83 and the upper cavity 72 on the extrados side.

[0074] Unlike the second embodiment, the two lateral cavities 74 and 76 are here joined together in the rear or downstream part instead of being separate. In this way, these two lateral cavities surround the central duct 73 over three-quarters of its circumference so as to further improve its thermal insulation from the external environment, so that it can provide the upper cavity 72 which it supplies with even cooler air.

[0075] As visible in the Figure 5, these two cavities are joined by a junction zone located downstream from the central duct, and which extends over the majority of the height of this central duct. These two cavities with their junction zone thus constitute a single cavity enveloping the central duct over the majority of its external surface. In practice, and as visible on the Figure 5 , the height or length of the junction zone along the span direction EV corresponds to the height or length of the first lateral cavity along the span direction EV.

[0076] The supply of these two lateral cavities can be carried out separately by two supply ducts taking the air separately from the blade root, the lateral cavities then being united only in the region of the blade. It may also be possible to provide a single supply channel for the two lateral cavities having a cross-sectional shape corresponding to that of the letter U.

[0077] The trailing edge cooling slot(s) located in the region of the apex S are supplied with air by the upper cavity 72. The other trailing edge slots, marked by 86, are supplied by a downstream ramp 87 which extends from the root, where it is supplied directly via this root, to the region of the apex S to terminate under the rear part of the upper cavity 72.

[0078] In a fourth embodiment of the invention shown in figure 6, the blade which is marked by 91 also comprises an upper cavity 92 supplied by a central duct 93 isolated by two lateral cavities 94 and 96. But in this fourth embodiment, the trailing edge is cooled by a downstream ramp which is supplied in a calibrated manner by a downstream duct.

[0079] The upper cavity 92 has a shape substantially identical to that of the blades of the figures 3 to 5 . It is located near the apex S, extends along the closing and intrados walls, from the front to the rear of the blade. The entire part of the apex S located on the intrados side is supplied with cooling air by this upper cavity 92, over its entire length up to the rear end. This upper cavity 92 also extends to the trailing edge, to supply at least the slot closest to the apex S, marked by 95, and possibly some adjacent slots.

[0080] This upper cavity 92 is delimited laterally by a first face 97 which runs along the intrados and a second face 98 spaced from the first, these faces being joined at the front and at the rear. It is delimited vertically by a bottom 99 parallel to the closing wall, and by the lower face 101 of this closing wall. In the region of the apex S, the intrados wall may also have through holes for cooling the external face of the intrados wall in the apex region. The central duct 93 feeds this upper cavity 92 by extending from the root of the blade by which it is supplied with air, to the apex S, where it opens entirely into the bottom 99.

[0081] The leading edge of the blade 91 is cooled by an upstream ramp 102 which extends from the base of the blade to the tip S, being supplied by an upstream duct 103 in a calibrated manner by means of calibrated passages 105 regularly spaced along the span direction EV of the blade and which each connect the upstream duct 103 to the upstream ramp 102. The wall of the blade comprises, in the region of the leading edge, through holes by means of which the air from the ramp cools the external face of the leading edge.

[0082] The first lateral cavity 94 has a small thickness and extends from the foot to the region of the apex S, having a generally rectangular outline. It ends under the upper cavity 92 without covering it. It has a width sufficient to mask or cover the central conduit 93 as well as the upstream conduit 103 which runs alongside this central conduit 93.

[0083] The second lateral cavity 96 also has a small thickness, and it extends from the foot to the region of the apex S but covering the upper cavity 92. It has a generally rectangular outline, of sufficient width to mask or cover the central conduit 93 and the upstream conduit 103 and the upper cavity 92 on the extrados side.

[0084] The trailing edge cooling slot(s) located in the region of the apex S are supplied with air by the upper cavity 92. The other trailing edge slots, marked 106, are supplied by a downstream ramp 107 which extends from the root to the region of the apex S.

[0085] This downstream ramp 107 is here supplied in a calibrated manner by a downstream duct 108 which extends from the root of the blade to the region of its apex S where it bypasses a rear part of the upper cavity 92. This downstream duct 108 is located between the central duct 93 and the downstream ramp 107, and it is not masked by either the lateral cavity 94 or the lateral cavity 96. The downstream duct 108 supplies the downstream ramp 107 in a calibrated manner, by means of a series of calibrated passages 109 regularly spaced from one another along the span direction EV and each joining the downstream duct to the ramp 107.

[0086] In a fifth embodiment of the invention shown in figure 7, the blade which is identified by 111 also comprises an upper cavity 112 supplied by a central duct 113 isolated by two lateral cavities 114 and 116. The trailing edge is also cooled by a downstream ramp supplied in a calibrated manner by a downstream duct, but this downstream duct is thermally protected by lateral cavities of the blade so as to provide cooler air for cooling the trailing edge.

[0087] The upper cavity 112 has a shape substantially identical to that of the blades of the figures 3 to 6. It is located near the apex S, extends along the closing and intrados walls, from the front to the rear of the blade. The entire part of the apex S located on the intrados side is supplied with cooling air by this upper cavity 112, over its entire length up to the rear end. This upper cavity 112 also extends to the trailing edge, to supply at least the slot closest to the apex S, marked by 115, and possibly some adjacent slots.

[0088] This upper cavity 112 is delimited laterally by a first face 117 which runs along the intrados and a second face 118 spaced from the first, these faces being joined at the front and at the rear. It is delimited vertically by a bottom 119 parallel to the closing wall, and by the lower face 121 of this closing wall. The central duct 113 feeds this upper cavity 112 by extending from the foot of the blade by which it is supplied with air, to the top S, where it opens entirely into the bottom 119.

[0089] The leading edge of the blade 111 is cooled by an upstream ramp 122 which extends from the base of the blade to the tip S, supplied by an upstream duct 123 in a calibrated manner thanks to calibrated passages 124 regularly spaced along the span direction EV of the blade and which each connect the upstream duct 123 to the upstream ramp 122.

[0090] The wall of the blade has through holes in the leading edge region through which the air from the ramp cools the outer face of the leading edge. The first lateral cavity 114 has a small thickness and extends from the root to the top region S, having a generally rectangular outline. It ends under the upper cavity 112 without covering it, and it has a width sufficient to mask or cover the central duct 113 as well as the upstream duct 123 which runs along this central duct 113, and the downstream duct for calibrated supply of the downstream ramp.

[0091] The second lateral cavity 116 also has a small thickness, and it extends from the foot to the region of the apex S but covering the upper cavity 112. It has a generally rectangular outline, of sufficient width to mask or cover the central conduit 113, the upstream conduit 123 and the upper cavity 112 on the extrados side, as well as the downstream conduit for calibrated supply of the downstream ramp.

[0092] The cooling slot 115 of the trailing edge located in the region of the apex S is supplied with air by the upper cavity 112. The other slots of the trailing edge, identified by 126, are supplied by the downstream ramp 127 which extends from the root to the region of the apex S.

[0093] This downstream ramp 127 is here supplied in a calibrated manner by the downstream duct 128 which extends from the foot of the blade to the region of its tip to end at the level of the tip S, bypassing the upper cavity 112. This downstream duct 128 is located between the central duct 113 and the downstream ramp 127. The downstream duct 128 supplies the downstream ramp 127 in a calibrated manner, by means of a series of calibrated passages 129 regularly spaced from one another and each joining the downstream duct 128 to the ramp 127.

[0094] As visible in the figure 7 , the lateral cavities 114 and 116 are here arranged to cover the upstream conduit 123, the central conduit 113 as well as the downstream conduit 128 so as to jointly cover these three elements to thermally insulate them from the intrados wall and the extrados wall.

[0095] In a sixth embodiment of the invention, not covered by the claims, shown in figure 8, the blade which is marked by 131 also has an upper cavity 132 supplied by a central duct 133, but this is isolated by a single lateral cavity 134 located on the intrados side. This makes it possible to simplify the manufacture of the blade while providing satisfactory cooling efficiency due to the fact that in practice, the intrados wall tends to heat up significantly more than the extrados wall.

[0096] The upper cavity 132 has a shape substantially identical to that of the blades of the figures 3 to 7. It is located near the apex S, extends along the closing and intrados walls, from the front to the rear of the blade. The entire part of the apex S located on the intrados side is supplied with cooling air by this upper cavity 132, over its entire length up to the rear end. This upper cavity 132 also extends to the trailing edge, to supply at least the slot closest to the apex S, marked by 135, and possibly some adjacent slots.

[0097] This upper cavity 132 is delimited laterally by a first face 137 which runs along the intrados and a second face 138 spaced from the first, these faces being joined at the front and at the rear. It is delimited vertically by a bottom 139 parallel to the closing wall, and by the lower face 141 of this closing wall. The central duct 133 feeds this upper cavity 132 by extending from the foot of the blade by which it is supplied with air, to the top S, where it opens entirely into the bottom 139.

[0098] The leading edge of the blade 131 is cooled by an upstream ramp 142 which extends from the base of the blade to the tip S, which is supplied by an upstream duct 143 in a calibrated manner by means of calibrated passages 144 which are regularly spaced along the span direction EV of the blade and which each connect the upstream duct 143 to the upstream ramp 142. The wall of the blade comprises in the region of the leading edge through holes by means of which the air from the ramp cools the external face of the leading edge.

[0099] The lateral cavity 134 has a small thickness and extends from the foot to the region of the apex S, having a generally rectangular outline. It ends below the upper cavity 132 without covering it. It has a width sufficient to mask or cover the central conduit 133 as well as the upstream conduit 143 which runs alongside this central conduit 133.

[0100] The cooling slot 135 of the trailing edge located in the region of the apex S is supplied with air by the upper cavity 132. The other slots of the trailing edge, identified by 146, are supplied by a downstream ramp 147 which extends from the root to the region of the apex S.

[0101] This downstream ramp 147 is here supplied in a calibrated manner by a downstream conduit 148 which extends from the foot of the blade to the region of its tip to end at the level of the tip S, bypassing the upper cavity 132. This downstream conduit 148 is located between the central conduit 133 and the downstream ramp 147. The downstream conduit 148 supplies the downstream ramp 147 in a calibrated manner, by means of a series of calibrated passages 149 regularly spaced from each other along the span direction EV and each joining this downstream conduit 148 to the ramp 147.

[0102] As visible in the figure 8, the lateral cavity 134 covers the upstream duct 143 as well as the central duct 133 and the downstream duct 148 so as to thermally insulate these three elements from the intrados wall to reduce the heating of the air which they carry.

[0103] As will be understood, in general, in each of the embodiments of the invention, the apex region is supplied with air by the upper cavity with respect to the entire portion of the apex extending along the intrados. The other portions of the apex are supplied with air by the other ducts, ramps or cavities of the blade, such as in particular the upstream ramp and possibly the upstream duct, the downstream ramp and possibly the downstream duct, and where appropriate the second lateral cavity running along the extrados.

[0104] In the examples described, the upper cavity has a thickness less than the thickness of the blade, i.e. the distance separating the intrados from the extrados. In practice, the thickness of this cavity can be reduced to less than half the thickness of the blade.

[0105] In the various embodiments, the upper cavity makes it possible to significantly improve the cooling of the blade tip region, in particular by supplying very cool air to the trailing edge slot which is closest to the tip. This upper cavity also ensures cooling by thermal conduction of the blade walls which delimit it, such as for example the closing wall of the blade.

[0106] Furthermore, holes passing through the walls of the blade and opening into the internal lateral cavities forming a heat shield may be provided to establish optimal air circulation in these cavities. Each of these holes is advantageously located at a depression zone to promote air circulation. Each of these holes ensures that the air collected at the root of the blade and which is conveyed into a cavity forming a heat shield, is sucked out of the blade, after having passed through this cavity.

[0107] In the various embodiments, the cooling of the blade is further optimized by minimizing the pressure losses in each internal duct to reduce heat exchanges, and on the contrary by providing turbulence promoters in each lateral cavity to increase heat exchanges.

[0108] The side cavities thus have increased efficiency as a thermal screen because they absorb the heat from the external walls they run alongside, and the air circulating in the internal ducts is subject to few pressure losses in order to circulate quickly and heat up as little as possible.

[0109] Internal ducts such as the upstream duct, the central duct and the downstream duct thus have smooth internal walls to promote rapid circulation of the cooling air by minimizing heat exchange between this air and the walls of the duct in which it travels. Each lateral cavity is advantageously provided with deflectors which promote air circulation in all regions of the cavity. In addition, the internal faces of the cavity are provided with disruptors and / or bridges to create turbulence in the circulation of the air in order to promote a high level of heat exchange between the air and the walls it passes along.

[0110] Generally speaking, the described blade can be made by direct manufacturing, by additive manufacturing, or by casting.

Claims

1. Turbine blade (51, 71, 91, 111, 131) for a turbine of a turbomachine such as a turboprop engine or a turbojet engine, this turbine blade being a hollow one-piece part manufactured by molding, this turbine blade comprising a root (P), a blade supported by this root and extending in a span direction (EV) terminating in a tip (S), this blade comprising a leading edge and a trailing edge located downstream of the leading edge, said blade comprising an intrados wall and an extrados wall which are spaced apart laterally from one another and each connect the leading edge to the trailing edge, said blade comprising: - a plurality of ducts (53, 63, 73, 83, 93, 103, 108, 113, 123, 128, 133, 143, 148) configured to collect cooling air at the root of the turbine blade and to circulate it through the blade to cool it; - holes (22, 24, 26, 27) and / or slots (55, 67, 75, 86, 95, 106, 115, 126, 135, 146) formed in its walls for discharging the cooling air from the blade; - an upper internal cavity (52, 72, 92, 112, 132) located at the tip of the blade for cooling this blade tip (S); at least one of the plurality of ducts (53, 73, 93, 113, 133) is a central duct directly supplying the upper cavity (52, 72, 92, 112, 132) with cooling air collected at the root (P) by being exclusively dedicated to the supply of cooling air to this upper cavity (52, 72, 92, 112, 132), characterized in that - it comprises a first internal lateral cavity (54, 74, 94, 114, 134) extending along the intrados wall while being separate from the direct feed duct (53, 73, 93, 113, 133) for forming a heat shield which thermally insulates this direct feed duct (53, 73, 93, 113, 133) from the intrados wall, - it comprises a second internal lateral cavity (56, 76, 96, 116) extending along the extrados wall while being separate from the direct feed duct (53, 73, 93, 113) to form a thermal shield which thermally insulates this direct feed duct (53, 73, 93, 113) from the extrados wall, - the upper cavity (52, 72, 92, 112, 132) extends from upstream to downstream of the blade, for supplying at least one slot (55, 75, 95, 115, 135) for cooling the trailing edge of the blade, and in that it comprises: - an upstream ramp (62, 82, 102, 122) for supplying cooling holes (22) of the leading edge, and an upstream duct (63, 83, 103, 123) for calibrated supply to this upstream ramp (62, 82, 102, 122) which is thermally insulated by each internal lateral cavity (54, 56, 74, 76, 94, 96, 114, 116); and / or - a downstream ramp (127) for supplying cooling slots (126) of the trailing edge located in the intrados wall, and a calibrated downstream supply duct (128) for this downstream ramp (127) which is thermally insulated by each internal lateral cavity (114, 116).

2. Turbine blade (51, 71, 91, 111, 131) according to claim 1, wherein the intrados wall includes at least one through hole (27) or through slot (55, 75, 95, 115, 135) which opens into the upper cavity (52, 72, 92, 112, 132).

3. Turbine blade (51, 71, 91, 111) according to claim 1 or 2, wherein each internal lateral cavity (54, 56, 74, 76, 94, 96, 114, 116) is provided with turbulence promoters and / or deflectors to increase heat exchange therein, and wherein each direct feed duct (53, 73, 93, 113) has smooth walls for limiting pressure losses.

4. Turbine blade (71) according to claim 1, wherein the two internal lateral cavities (74, 76) are joined by a junction zone located downstream of the direct supply duct (73) to form a single cavity enveloping three quarters of the circumference of this direct supply duct (73) and extending over the majority of the length of this direct supply duct (73).

5. Molding means configured for the manufacture of a turbine blade, comprising impressions and a set of cores intended for the formation of internal ducts (53, 63, 73, 83, 93, 103, 108, 113, 123, 128, 133, 143, 148) of internal lateral cavities (54, 56, 74, 76, 94, 96, 114, 116, 134), ramps (62, 82, 102, 122, 127) and slots (55, 67, 75, 86, 95, 106, 115, 126, 135, 146) of a turbine blade according to any one of claims 1 to 4.

6. Turbine of a turbomachine comprising a turbine blade according to any one of claims 1 to 4.

7. Turbomachine comprising a turbine according to the preceding claim.