Turbomachine moving blade with cooling circuit having a double row of discharge slots

Abstract

The invention relates to a turbomachine moving blade (2) comprising at least one cooling circuit comprising at least one cavity (16; 16a, 16b) extending radially between the foot and the vertex, at least one air intake opening at a radial end of the cavity, a plurality of first discharge slots (18) arranged to open out along the trailing edge between the foot and the vertex, and a plurality of second discharge slots (20) which are separate from the first discharge slots and provided along the trailing edge (14) between the foot and the vertex, the second discharge slots (20) being axially offset upstream from the first discharge slots (18) and each of the first discharge slots being radially offset from each of the second discharge slots, without any overlap between the first and second discharge slots.

Description

Technical Field

[0001] The present invention relates to the general field of turbomachine blades, and more particularly to the evacuation at the trailing edge of the cooling air from the blades of a high-pressure turbomachine turbine. Prior art

[0002] The blades of a high-pressure turbine are subjected to the high temperatures of the gases coming from the combustion chamber and passing through the high-pressure turbine. These temperatures reach values ​​well above those that the blades in contact with these gases can withstand, which has the consequence of limiting their service life.

[0003] In order to limit the damage caused by these hot gases on the blades, it is known to equip them with internal cooling circuits aimed at reducing the temperature of the latter. Thanks to such circuits, cooling air, which is generally introduced into the blade through its root, passes through it following a path formed by cavities made in the blade before being ejected through slots opening on the surface of the blade, between the root and the tip of the blade.

[0004] Growing demands for performance, efficiency, lifespan, and reliability are driving the need to design increasingly efficient cooling circuits. Increasing the efficiency of these cooling circuits offers numerous advantages. In particular, the permissible thermal level in the flow path will be higher, and the engine will be more efficient at the same cooling flow rate. In addition, the cooling flow rate required to ensure the integrity of the parts cooled by these cooling circuits will be lower for a given operating point. Finally, the lifespan of these parts will be longer for the same ventilation flow rate and under the same thermodynamic conditions.

[0005] In this perspective of increasing the efficiency of the cooling circuits, it is noted that the trailing edge of the moving blade is a critical zone from a thermal and mechanical point of view due to the difficulty in cooling it efficiently. This is mainly due to the lack of space, in particular because of the minimum thicknesses of material required for the manufacture of the blade, and in particular at the junction of the intrados and extrados walls at the trailing edge.

[0006] To effectively cool the trailing edge, it is known to cast cooling circuit discharge slots on the intrados side of the blade. These slots allow cooling of the material at the trailing edge by pumping, and by film ("film cooling" in English) with an ejection almost tangent to the blade profile, which greatly increases its efficiency.

[0007] On the other hand, the area of ​​the blade upstream of the exhaust slots is a difficult area to cool and regularly displays a high thermal level. This is due in particular to the lack of space to install turbulence promoters for cooling and to have two cooling cavities in the thickness of the blade.

[0008] Document JP 2014 111901 discloses a blade comprising two rows of cooling orifices. Document JP 2003 056301 discloses a blade comprising two rows of cooling slots. Statement of the invention

[0009] The present invention therefore aims to propose a moving turbomachine blade which does not have the aforementioned drawbacks.

[0010] According to the invention, this object is achieved by means of a moving turbomachine blade, comprising a blade extending radially between a blade root and a blade tip and axially between a leading edge and a trailing edge, and at least one cooling circuit comprising at least one cavity extending radially between the root and the tip, at least one air intake opening at a radial end of the cavity, a plurality of first discharge slots arranged along the trailing edge between the root and the tip, and a plurality of second discharge slots distinct from the first slots and arranged along the trailing edge between the root and the tip, the second discharge slots being axially offset upstream relative to the first discharge slots and each of the first discharge slots being radially offset relative to each of the second discharge slots,without radial overlap between the first and second discharge slots.,

[0011] The invention is remarkable in that it provides an additional row of discharge slots upstream and radially offset without overlapping with respect to the usual row of discharge slots. Thus, this additional row makes it possible to benefit from cooling upstream of the usual slots. The intrados face of the blade is then cooled on a larger curvilinear abscissa at the trailing edge of the blade. Furthermore, upstream of this additional row of discharge slots, the thickness of the blade profile is greater, which makes it possible to have a cavity provided with cooling promoters or to have two separate cavities. Finally, this radially offset arrangement of the slots of the two rows without overlapping between them makes it possible to increase the cooling efficiency, in particular for the cooling of the slot ribs located downstream.

[0012] The first drain slots and the second drain slots may open into the same cavity of the cooling circuit.

[0013] Alternatively, the first exhaust slots and the second exhaust slots may open into two separate cavities of the cooling circuit.

[0014] In this case, the cavity into which the second discharge slots open is preferably axially offset upstream relative to the cavity into which the first discharge slots open.

[0015] The first exhaust slots open at the trailing edge and the second exhaust slots can open at an intrados face of the blade.

[0016] Alternatively, the first exhaust slots and the second exhaust slots may open at an intrados face of the blade.

[0017] The first discharge slots and the second discharge slots may be arranged in columns. Similarly, the second discharge slots may occupy exactly each of the radial spaces left between the first discharge slots. The invention also relates to a method for manufacturing by casting a blade as defined above, comprising the production of a ceramic core by additive manufacturing, the core making it possible to produce the first discharge slots and the second discharge slots. This manufacturing solution makes it possible to produce the foundry cores necessary to reserve the locations for the cavities of the cooling circuit. The invention also relates to a high-pressure turbine for a turbomachine, comprising a disk which has a plurality of cells which open at the periphery of the disk and a plurality of blades as defined above. Brief description of the drawings

[0018] [ Fig. 1 ] There figure 1 is a perspective view of an example of a blade to which the invention applies. Fig. 2 ] There figure 2 is a cross-sectional view of a blade according to one embodiment of the invention showing the cooling circuit of the trailing edge of the blade. Fig. 3 ] There figure 3 is a partial and perspective view of the intrados side of a blade according to another embodiment of the invention showing the evacuation slots of the cooling circuit of the trailing edge of the blade. Fig. 4 ] There figure 4 is a partial and perspective view of the intrados side of a blade according to yet another embodiment of the invention. Description of the embodiments

[0019] There figure 1 represents in perspective a turbine blade 2, for example a moving blade of a high-pressure turbine of a turbomachine. The blade 2 is fixed on a turbine rotor (not shown) by means of a fitting 4 generally in the shape of a fir tree.

[0020] In a known manner, the blade 2 comprises a blade 6 which extends radially between a blade root 8 and a blade tip 10, and axially between a leading edge 12 and a trailing edge 14. The blade 6 of the blade thus defines the intrados 6a and the extrados 6b of the blade.

[0021] The blade 2, which is subjected to the high temperatures of the combustion gases passing through the turbine, needs to be cooled. For this purpose, and still in a known manner, the blade 2 comprises one or more internal cooling circuits, and in particular an internal trailing edge cooling circuit.

[0022] As shown in the figure 2 , the internal cooling circuit of the trailing edge of the blade comprises at least one cavity 16 extending radially between the root 8 and the tip 10. The cavity 16 is supplied with cooling air at one of its radial ends by an air intake opening (not shown) which is generally provided at the root 4 of the blade.

[0023] In the embodiment shown in the figure 2 , the internal cooling circuit of the trailing edge of the blade comprises two separate cavities 16a, 16b which are axially offset from each other.

[0024] According to the invention, the trailing edge cooling circuit also comprises a plurality of first discharge slots 18 which are arranged along the trailing edge 14 of the blade between the root 8 and the tip 10, and a plurality of second discharge slots 20 which are distinct from the first discharge slots 18 and which are also arranged along the trailing edge between the root and the tip of the blade.

[0025] In the embodiment shown in the figure 2 , the first evacuation slots 18 open into the cavity 16b of the cooling circuit and open onto the intrados face 6a of the blade near its trailing edge 14. As for the second evacuation slots 20, they open into the cavity 16a of the cooling circuit and also open onto the intrados face 6a of the blade near its trailing edge 14.

[0026] Furthermore, as more precisely represented on the figure 3 , the second discharge slots 20 are axially offset upstream relative to the first discharge slots 18 and arranged to be radially offset relative to the first discharge slots without overlapping therebetween, i.e. the lower wall of a given slot does not overlap the upper wall of the adjacent radially offset slot and vice versa.

[0027] Thus, the first and second discharge slots 18, 20 are arranged so as to form two distinct rows of slots which are axially and radially offset from each other.

[0028] There figure 3 represents a second embodiment of the invention in which the first discharge slots 18 and the second discharge slots 20 open into the same cavity 16 of the cooling circuit of the trailing edge of the blade. More precisely, in this example which cannot be limited to this supply by a single cavity, the lower walls of the first slots 18 coincide with the upper walls of the adjacent second slots 20 and the upper walls of the first slots 18 coincide with the lower walls of the adjacent second slots 20, so that the second slots occupy exactly each of the radial spaces left between the first slots.

[0029] There figure 4represents a third embodiment of the invention in which the first discharge slots 18 of the trailing edge cooling circuit open at the trailing edge 14 of the blade, while the second discharge slots 20 open at the intrados face 6a of the blade 2.

[0030] The blade 2 according to the invention is obtained directly by molding. For this purpose, the blade is produced by casting a metal into a mold containing a ceramic core which has the function in particular of reserving a location for the cooling circuit of the blade, and in particular for the cavity 16 and the first and second evacuation slots 18, 20 of the cooling circuit of the trailing edge of the blade.

[0031] In order to obtain the double row of evacuation slots directly from the foundry, the ceramic core is advantageously produced by additive manufacturing.

Claims

1. A movable turbomachine blade (2) comprising: a vane (6) extending radially between a blade root (8) and a blade tip (10) and axially between a leading edge (12) and a trailing edge (14); and at least one cooling circuit comprising at least one cavity (16; 16a, 16b) extending radially between the root (8) and the tip (10), at least one air intake opening at a radial end of the cavity (16; 16a, 16b), a plurality of first discharge slots (18) arranged to open out along the trailing edge between the root (8) and the tip (10), and a plurality of second discharge slots (20) separate from the first discharge slots and arranged along the trailing edge (14) between the root (8) and the tip (10), the second discharge slots (20) being offset axially upstream relative to the first discharge slots (18) and each of the first discharge slots (18) being radially offset relative to each of the second discharge slots (20), with no overlap between the first and second discharge slots.

2. The blade (2) according to claim 1, wherein the first discharge slots (18) and the second discharge slots (20) open out into the same cavity (16) of the cooling circuit.

3. The blade (2) according to claim 1, wherein the first discharge slots (18) and the second discharge slots (20) open out into two separate cavities (16a, 16b) of the cooling circuit.

4. The blade (2) according to claim 3, wherein the cavity (16a) into which the second discharge slots (20) open out is offset axially upstream relative to the cavity (16b) into which the first discharge slots (18) open out.

5. The blade (2) according to any one of claims 1 to 4, wherein the first discharge slots (18) open out at the trailing edge (14) and the second discharge slots (20) open out at an intrados face (6a) of the blade.

6. The blade (2) according to any one of claims 1 to 4, wherein the first discharge slots (18) and the second discharge slots (20) open out at an intrados face (6a) of the blade.

7. The blade (2) according to any one of claims 1 to 6, wherein the first discharge slots (18) and the second discharge slots (20) are arranged in columns.

8. The blade (2) according to any one of claims 1 to 6, wherein the second discharge slots (20) occupy exactly each of the radial spaces left between the first discharge slots (18).

9. A method for manufacturing, by foundry, a blade according to any one of claims 1 to 6, comprising the production of a ceramic core by additive manufacturing, the core making it possible to produce the first discharge slots (18) and the second discharge slots (20).

10. A high-pressure turbomachine turbine comprising a disk which has a plurality of cells which open out at the periphery of the disk and a plurality of blades (2) according to any one of claims 1 to 7, the root of each blade (2) being mounted in a respective cell of the disk.

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