Turbine blade of a turbomachine with improved cooling, corresponding turbine and aircraft turbomachine

Description

TECHNICAL FIELD

[0001] The invention relates to a turbomachine blade, such as a turbojet, a turboprop, or a gas turbine, and it applies in particular to a high-pressure type turbine blade. The invention relates in particular to a turbine blade of a turbomachine as well as a turbine and a turbomachine comprising said blade. STATE OF THE PRIOR ART

[0002] In such a turbojet engine, marked 1 in the figure 1 , air is admitted into an inlet sleeve 2 to pass through a blower comprising a series of rotating blades 3 before splitting into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow is compressed by low pressure 4 and high pressure 5 compressors before reaching a combustion chamber 6, after which it expands by passing through a high pressure turbine 7 and a low pressure turbine 8, before being evacuated, generating auxiliary thrust. The secondary flow is propelled directly by the fan to generate main thrust.

[0004] Each turbine 7, 8 comprises series of blades oriented radially and regularly spaced around an axis of rotation AX, an external casing 9 surrounding the entire engine.

[0005] Cooling of the turbine blades is ensured by circulating in each blade air taken upstream of the combustion chamber and admitted at the blade root, this air being evacuated through holes and / or slots passing through the walls of these blades.

[0006] Generally speaking, the efficiency of cooling, and in particular the reduction in the flow rate required to cool the high-pressure turbine blades, makes it possible to reduce the fuel consumption of a turbojet and increase the life of the blades.

[0007] However, it appears that the cooling of high-pressure turbine blades requires constant improvement efforts, particularly due to the continual evolution of operating conditions, manufacturing processes and performance requirements.

[0008] In this context, the aim of the invention is to provide a new blade design having an improved cooling circuit.

[0009] Document US 2014 / 093392 A1 discloses a blade which comprises a serpentine circuit running along its upper surface wall, which comprises three ducts oriented in the spanwise direction, clearly connected by bent portions, and which supply the vents on its trailing edge. This blade comprises another serpentine circuit running along its lower surface wall which is substantially identical. Each serpentine circuit is necessarily supplied with air by its duct which is furthest upstream, i.e. furthest from the trailing edge.

[0010] Document EP 3 034 792 A1 is limited to disclosing a blade comprising oblique channel circuits, the blade comprising two circuits resembling serpentine circuits symmetrical to each other, and each supplied by a duct which is closest to the trailing edge among the ducts of these serpentine circuits. STATEMENT OF THE INVENTION

[0011] For this purpose, the invention relates to a turbine blade of a turbomachine as indicated in claim 1.

[0012] With this arrangement, the number of blade circuits is limited since it is not necessary to provide a circuit dedicated to cooling the trailing edge, which makes it easier to manufacture the blade root, particularly at its root.

[0013] The invention also relates to a blade thus defined, in which the first serpentine circuit supplies air to the vents closest to the root, and in which the second serpentine circuit supplies air to the other vents.

[0014] The invention also relates to a blade so defined, in which the second serpentine circuit supplies air to the vents closest to a tip portion of the blade, and in which the first serpentine circuit supplies air to the other vents.

[0015] The invention also relates to a blade thus defined, in which the first serpentine circuit comprises a first upstream duct, a first middle duct and a first terminal duct and in which the second serpentine circuit comprises a second upstream duct, a second middle duct, a second downstream duct, and a second terminal duct, and in which these ducts are elongated.

[0016] The invention also relates to a blade thus defined, in which the ducts of the first serpentine circuit extend on the intrados side along a intrados wall of the blade, and in which the ducts of the second serpentine circuit extend on the extrados side along a extrados wall of the blade.

[0017] The invention also relates to a blade thus defined, in which the blade comprises a pressure wall comprising cooling holes supplied with air by the first serpentine circuit.

[0018] The invention also relates to a blade thus defined, obtained by additive manufacturing.

[0019] The invention also relates to a blade thus defined, made of composite or ceramic material.

[0020] The invention also relates to a blade thus defined, comprising a leading edge and an upstream circuit dedicated to cooling this leading edge.

[0021] The invention also relates to a turbine comprising a blade according to one of the preceding claims.

[0022] The invention also relates to an aircraft turbomachine comprising a turbine thus defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] [ Fig. 1 ] is a sectional view of a known turbojet engine; [ Fig. 2 ] is an external perspective view of a blade according to the invention; [ Fig. 3] is a representation of the interior of the blade according to the invention according to three section planes located at its base and its middle region as well as its top and showing its internal cooling circuits. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0024] The dawn according to the invention, marked 11 on the figure 2 , comprises a foot P by which it is fixed in a cell of a rotor disk, and a blade 12 carried by this foot P, with a platform 13 connecting the foot P to the blade 12. This blade 11 which is hollow comprises internal circuits in which circulates cooling air admitted by openings located on a radially internal face 14 of the foot P.

[0025] In the example of the figures, this blade is a single-piece part from a foundry of a metallic material, which is obtained by using a set of cores to delimit its internal cooling ducts, these cores being removed after casting and cooling for example with a chemical etching process. It can also be made of composite or ceramic materials or even be obtained by additive manufacturing.

[0026] The blade 12 extends along a so-called span axis EV substantially perpendicular to an axis AX of rotation of the rotor carrying the blade, which is the longitudinal axis of the engine. It comprises a leading edge 16 substantially parallel to the span direction EV and located upstream AM or in front of the blade, relative to the general direction of circulation of the gases in the engine. It comprises a trailing edge 17 substantially parallel to the leading edge 16 and spaced from it along the axis AX to be downstream AV or behind the blade. It also comprises a tip S substantially parallel to the base B and spaced from it in the span direction EV.

[0027] The two main walls of this dawn are its intrados wall 19, visible in the figure 2, and its extrados wall 21, which are spaced from each other while being joined at the leading edge 16, at the trailing edge 17, and in the region of the apex S which comprises a wall oriented perpendicular to the span direction EV.

[0028] The leading edge 16 is curved and has cooling holes 22 passing through its wall. These holes 22 are supplied with air by an upstream circuit A of the blade, shown schematically in the figure 3 . This figure 3 is a representation of the interior of the dawn of the figure 2 in the form of three sections in planes normal to the span direction EV. The first section II is located near the base B, the second section II-II is located approximately midway between the base B and the apex S, and the third section III-III is located near the apex S.

[0029] As visible on this figure 3, the upstream circuit A mainly comprises a duct A1 running along the internal face of the leading edge and being supplied with air by an opening located at the level of the internal face 14 of the blade. The air conveyed by this duct A1 is evacuated through the holes 22 to form a film of cooling air on the external face of the leading edge.

[0030] The intrados wall comprises a first series of holes 23, and a second series of holes 24 which pass through it and are supplied by a first serpentine circuit T1 so as to form a film on the external face of the intrados 19 in order to protect it thermally. The first series of holes 23 extends in the spanwise direction while being located downstream of the leading edge, and the second series of holes 24 is located downstream of the first series and upstream of the trailing edge 17.

[0031] The holes 22, 23, 24 which are optional can be cylindrical, oblong, with flared shapes or other, with appropriate sizes and being separated from each other by an appropriate pitch. They are optimized to generate an optimal external air film in terms of cooling.

[0032] The first serpentine circuit T1 comprises an upstream duct CA1, a middle duct CM1 connected to the upstream duct CA1 by a bent portion located at the apex S, and a terminal duct CT1 connected to the middle duct by a bent portion located near the base B. These three ducts CA1, CM1 and CT1 extend in the span direction EV, they run along the internal face of the intrados wall to cool it while being delimited by internal walls of the blade. The upstream duct CA1 is located immediately downstream of the duct A1 of the upstream circuit A, the middle duct CM1 is located immediately downstream of the upstream duct CA1, and the terminal duct CT1 is located immediately downstream of the middle duct CM1, that is to say near the trailing edge.

[0033] The upstream duct CA1 is supplied with air by a mouth located at the radially inner face 14 of the blade, the radial direction corresponding to the span direction EV when the blade is carried by the disk. The air thus circulates in this blade from the base to the tip, and optionally it supplies the first series of holes 23. The middle duct CM1 is supplied with air by the upstream duct CA1 via the bent portion, so that the air circulates therein from the tip S to the base B, and optionally it supplies air to the second series of holes 24. The terminal duct CT1 is supplied with air by the middle duct CM1 via the corresponding bent portion, so that the air circulates therein from the base B to the tip S.

[0034] Similarly, the extrados wall may have cooling holes passing through it to form a cooling film on its radially external face, these holes being supplied by a second serpentine circuit T2.

[0035] This second serpentine circuit T2 comprises an upstream duct CA2, a middle duct CM2 connected to the upstream duct CA2 by a bent portion located at the level of the apex S, a downstream duct CV2 connected to the middle duct CM2 by a bent portion located at the level of the base B, and a terminal duct CT2 connected to the downstream duct CV2 by a bent portion located near the apex S. These four ducts CA2, CM2, CV2 and CT2 extend in the span direction EV, they run along the internal face of the extrados wall to cool it while being delimited by internal walls of the blade.

[0036] The upstream duct CA2 is located immediately downstream of duct A1 of the upstream circuit A, the middle duct CM2 is located immediately downstream of the upstream duct CA2, the downstream duct CV2 is located immediately downstream of the middle duct CM2, and the terminal duct CT1 is located immediately downstream of the downstream duct CV2, i.e. near the trailing edge.

[0037] The upstream duct CA2 is supplied with air through a mouth located at the radially inner face 14 of the blade root, so that the air flows therein from the base to the tip. The middle duct CM2 is supplied with air by the upstream duct CA2 via the bent portion, so that the air flows therein from the tip S to the base B. The downstream duct CV2 is supplied with air by the middle duct CM2 via another bent portion, so that the air flows therein from the base B to the tip S. The terminal duct CT2 is supplied with air by the downstream duct CV2 via the corresponding bent portion, so that the air flows therein from the tip to the base B.

[0038] In addition to supplying the cooling holes and cooling the intrados and extrados, the two serpentine circuits T1 and T2 also provide cooling air supply to the trailing edge.

[0039] The trailing edge 17 which is tapered comprises a series of cooling vents, of short lengths which extend parallel to the span direction EV, being spaced apart and in line with each other in the span direction EV, that is to say the radial direction when the blade is carried by a disc extending along a main axis. They are located a short distance from the trailing edge itself.

[0040] These vents are divided into, on the one hand, radially internal vents 26 located on the side of the base of the blade between the first section II and the second section II-II, and on the other hand, radially external vents 27 located between the second section II-II and the third section III-III. The radially internal vents 26 are thus closest to the base B while the radially external vents are closest to the tip S. Each vent blows air towards the trailing edge 17 which is provided with external ribs channeling this air parallel to the axis AX.

[0041] The radially internal vents 26 are supplied with air by the terminal duct CT1 of the first serpentine circuit T1 while the radially external vents 27 are supplied with air by the terminal duct CT2 of the second serpentine circuit T2.

[0042] As visible on the figure 3, the terminal duct CT1 of the first serpentine circuit T1 extends over substantially half the height of the blade, from its base B to the level of the second section II-II. This terminal duct CT1 supplies cooling air to radially internal vents 26 of the trailing edge.

[0043] Similarly, the terminal duct CT2 of the second serpentine circuit T2 also extends over approximately half the blade height, from the tip S to the second section II-II. As seen in the figure 3 , the terminal conduit CT2 of the second serpentine circuit T2 extends in the extension of the terminal conduit CT1 of the first serpentine circuit T1.

[0044] These two terminal conduits CT1 and CT2 are thus located in the extension of one another, extending in the span direction, and running alongside the vents 26 and 27 which they supply. They are separated from one another by a partition 28 delimiting their mutual ends located opposite each other. As visible on the figure 3 , this partition 28 is located at the level of section II-II, that is to say at mid-height of the blade in this example.

[0045] The partition 28 may be located at another position, its positioning being conditioned by the dimensioning of the blade itself, that is to say in particular by the desired distribution of air flow circulating in the first serpentine circuit and in the second. This partition 28 could thus be located at one third or two thirds of the height of the blade depending on the scenario envisaged.

[0046] The value and distribution of the air flow rates in the first serpentine circuit T1 and in the second circuit T2 is also conditioned by the size of the trailing edge cooling vents, i.e. by their passage section which constitutes another dimensioning parameter.

[0047] In the example of the figures, the first serpentine circuit T1 has three ducts and the second has four. Other numbers of ducts are possible for these serpentine circuits, provided that one of the serpentine circuits has an even number of ducts while the other has an odd number of ducts. This difference in parity of the numbers of ducts of the first and second serpentine circuits makes it possible to form terminal ducts located opposite each other to ensure a supply of all the vents of the trailing edge. More concretely, the serpentine circuit having an even number of ducts (excluding the terminal duct) supplies the radially internal vents while the serpentine circuit having an odd number of ducts (excluding the terminal duct) supplies the radially external vents.

[0048] Generally speaking, the blade according to the invention comprises a number of supply openings at the level of the radially internal face 14 of its root which can be limited to three, namely one for the upstream circuit A, one for the first serpentine circuit T1, and another for the second serpentine circuit T2, which simplifies the manufacture of the root P. Optionally, it is possible to add additional cooling air through the root in line with the conduits CM1 and CM2 to compensate for the air emitted by the cooling holes when they are present.

Claims

1. A turbine vane (11) of a turbomachine, comprising a root (P) carrying a blade (12) extending along a span direction (EV), this blade (12) comprising a trailing edge (17) provided with cooling vents (26, 27), as well as a first serpentine circuit (T1) and a second serpentine circuit (T2), and wherein: - each serpentine circuit (T1, T2) includes several ducts (CA1, CM1, CT1, CA2, CM2, CV2, CT2) extending along the span direction (EV) by being connected to each other through bent portions; - each serpentine circuit (T1, T2) is supplied with air by a mouth located at the root (P) via its duct (CA1, CA2) which is furthest from the trailing edge (17); - the first serpentine circuit (T1) has an even number of ducts and the second serpentine circuit (T2) has an odd number of ducts, or vice versa, wherein the first and second serpentine circuits (T1, T2) are terminated by a first and a second terminal duct (CT1, CT2) respectively, these two terminal ducts (CT1, CT2) running along the trailing edge (17) as an extension of each other, and by being separated from each other by an inner partition wall (28) of the blade (12) ; - the vents (26, 27) are supplied with cooling air from the first serpentine circuit (T1) and from the second serpentine circuit (T2).

2. The vane according to claim 1, wherein the first serpentine circuit (T1) supplies the vents (26) closest to the root (P) with air, and wherein the second serpentine circuit (T2) supplies the other vents (27) with air.

3. The vane according to claim 1 or 2, wherein the second serpentine circuit (T2) supplies the vents (26) closest to an apex part (S) of the blade (12) with air, and wherein the first serpentine circuit (T1) supplies the other vents (27) with air.

4. The vane according to claim 3, wherein the first serpentine circuit (T1) includes a first upstream duct (CA1), a first middle duct (CM1) and a first terminal duct (CT1) and wherein the second serpentine circuit (T2) includes a second upstream duct (CA2), a second middle duct (CM2), a second downstream duct (CV2), and a second terminal duct (CT2), and wherein these ducts are elongate.

5. The vane according to claim 1, wherein the ducts (CA1, CM1, CT1) of the first serpentine circuit (T1) extend on the lower surface side by running along a lower surface wall (19) of the blade (12), and wherein the ducts (CA2, CM2, CV2, CT2) of the second serpentine circuit (T2) extend on the upper surface side by running along an upper surface wall (21) of the blade (12).

6. The vane according to claim 1, wherein the vane includes a lower surface wall (19) including cooling holes (23, 24) supplied with air from the first serpentine circuit (T1).

7. The vane according to claim 1, comprising a leading edge (16) and an upstream circuit (A) dedicated to cooling this leading edge (16).

8. The vane according one of claims 1 to 7, obtained by additive manufacturing.

9. The vane according one of claims 1 to 7, made of composite or ceramic material.

10. A turbine comprising a vane according to claim 1.

11. An aircraft turbomachine comprising a turbine according to the preceding claim.