Turbine engine blade provided with an optimized cooling circuit

Abstract

The invention relates to a turbine engine blade (20), comprising: an airfoil (21), the airfoil having a pressure side wall and a suction side wall, the pressure side wall and the suction side wall being connected upstream by a leading edge (26) and connected downstream by a trailing edge (27), a cooling circuit (28), the cooling circuit comprising an inner cavity extending inside the airfoil and a plurality of outlet openings, each outlet opening being oriented approximately along a longitudinal axis X, each outlet opening being connected to the cavity and being arranged near the trailing edge, and a calibration device (33), the calibration device being arranged in the cavity and being provided with a calibration duct (34), the calibration duct being arranged approximately opposite to the outlet opening, wherein according to the invention, the calibration ducts (34) each comprise an oblong cross section approximately perpendicular to the longitudinal axis.

Description

Technical Field

[0001] The present invention relates to the field of turbine engines and in particular to a turbine engine blade equipped with a cooling circuit intended to cool the turbine engine blade. Background Art

[0002] Prior art includes documents EP-A2-1 793 083, EP-A1-1 267 039 and US-A1-2013 / 259645.

[0003] The turbine engine blades, in particular the high-pressure turbine blades, are subjected to very high temperatures, which can shorten the service life of the turbine engine blades and reduce the performance of the turbine engine. In fact, the turbine engine turbine is arranged downstream of the combustion chamber of the turbine engine, which ejects the hot gas flow expanded by the turbine and enables the turbine engine turbine to be driven in rotation for the operation of the turbine engine. The high-pressure turbine is located directly at the outlet of the combustion chamber and is subjected to the highest temperature.

[0004] In order to enable the turbine blades to withstand these severe thermal stresses, it is known to provide a cooling circuit in which relatively cool air circulates, this air being taken up at the level of the compressor, which is positioned upstream of the combustion chamber. More specifically, each turbine blade comprises a blade having a pressure side surface and a suction side surface, which are connected upstream by a leading edge and downstream by a trailing edge. The cooling circuit comprises a cavity positioned inside the blade and opening into orifices, which are positioned near the trailing edge. These orifices deliver jets of cooling air to the wall of the blade.

[0005] However, the orifices are not uniformly supplied with air. A calibration device has been developed to ensure that most of the cooling air flow is delivered only to the first orifice that is radially closest to the blade root. The calibration device comprises a baffle provided with holes and arranged in the cooling air path upstream of the orifices. These holes enable each orifice to generate a local jet that will cool the pressure side surface.

[0006] However, the bore of the calibration device is subject to extremely strong mechanical loads due to local thermal gradients, centrifugal forces associated with the rotation of the blades (which introduce tensile stresses) and the geometry of the bore (which causes a stress concentration factor "kt"). Summary of the invention

[0007] The object of the invention is to reduce the mechanical stresses to which the holes of a device for calibrating the cooling air are subjected, in particular, while avoiding significant structural modifications to the device itself and to the blades.

[0008] According to the invention, this is achieved by a turbine engine blade comprising:

[0009] a blade having a pressure side wall and a suction side wall connected upstream by a leading edge and downstream by a trailing edge,

[0010] a cooling circuit comprising an inner cavity extending inside the blade and a plurality of outlet orifices, each outlet orifice being oriented substantially along the longitudinal axis X, each outlet orifice communicating with the inner cavity and being arranged in the vicinity of the trailing edge, and

[0011] - a calibration device arranged in the inner cavity and provided with calibration ducts arranged substantially opposite the outlet orifice, the calibration ducts each comprising an oblong or substantially oblong cross-section substantially perpendicular to the longitudinal axis.

[0012] This solution therefore makes it possible to achieve the above-mentioned objectives. In particular, the specific shape of the calibration duct makes it possible to greatly reduce the mechanical stresses, in particular the static stresses, and to increase the radius of the section of the duct while keeping the duct at an iso section and thus at an iso flow rate. The load is distributed between the elongated ends of the holes, which increases the contact area of ​​the holes and further reduces the stresses. This shape also makes it possible to limit the risks of recrystallization of the grains of the material making up the calibration device and the blades. Finally, this structure makes it possible to increase the mass compared to traditional solutions consisting in increasing the thickness of the partitions of the calibration device (and therefore increasing the mass).

[0013] The blade also includes one or more of the following features, which are used alone or in combination:

[0014] The calibration device comprises a calibration chamber arranged downstream of the calibration conduit, the calibration chamber being in fluid communication with the calibration conduit and the outlet orifice.

[0015] The calibration duct is carried by a partition extending radially in the blade and forming upstream of the internal cavity and downstream of a calibration cavity forming the reservoir.

[0016] - Each calibration conduit comprises a first straight portion and a second straight portion opposite each other along a predetermined width passing through a central axis of each conduit.

[0017] Each first straight portion and second straight portion extends over a distance d of approximately 0.2 mm.

[0018] - Each calibration conduit extends over a predetermined height and comprises a first circular end and a second circular end opposite along the predetermined height.

[0019] - A ratio of the predetermined height to the predetermined width is between 0.5 and 2.5.

[0020] Each calibration duct comprises an arc portion having a first radius R1 , each arc portion being symmetrical relative to a first median plane passing through the central axis and perpendicular to the width L, and relative to a second median plane passing through the central axis and perpendicular to the predetermined height H.

[0021] The first end and the second end are rounded along an arc having a second radius R2 , the value of which is smaller than the value of the first radius R1 .

[0022] The value of the first radius R1 is equal to twice the nominal radius R0 of the calibration duct with circular cross section, the passage area of ​​which is equal to the passage area of ​​the cross section of the calibration duct with oblong cross section.

[0023] - The central axis is determined by the middle of the predetermined height and the predetermined width of each calibration conduit.

[0024] The invention also relates to a turbine engine turbine comprising at least one turbine engine blade having the above-mentioned characteristics.

[0025] The invention also relates to a turbine engine comprising at least one turbine engine turbine as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will be better understood and other objects, details, features and advantages of the invention will become more apparent on reading the following detailed description of an embodiment of the invention given as a purely illustrative and non-limiting example, with reference to the schematic drawings, in which:

[0027] [ Figure 1 ] Figure 1 is a partial axial cross-sectional view of an example of a turbine engine to which the present invention is applied;

[0028] [ Figure 2 ] Figure 2 is a schematic view of an axial section of an example of a turbine engine blade according to the invention;

[0029] [ Figure 3 ] Figure 3 is a cross-sectional view of a cooled turbine engine blade equipped with means for calibrating the cooling air intended to be ejected through orifices at the level of its trailing edge;

[0030] [ Figure 4 ] Figure 4 is a schematic view of an example of a calibration duct of a calibration device of a turbine engine blade intended to be cooled according to the invention;

[0031] [ Figure 5 ] Figure 5 A map showing the static stresses applied to a calibration conduit of circular cross-section of a prior art calibration device;

[0032] [ Figure 6 ] Figure 6 A map of the static stresses applied to a calibration conduit of an oblong segment of a calibration device according to the invention is shown. DETAILED DESCRIPTION

[0033] Figure 1 A turbine engine 1 applied to the invention is shown in an axial cross-sectional view along the longitudinal axis X. The turbine engine shown is a twin-flow and twin-shaft turbine engine intended to be installed on an aircraft according to the invention. Of course, the invention is not limited to this type of turbine engine.

[0034] This turbine engine 1 with double flow generally comprises a fan 2 mounted upstream of a gas generator 3. In the present invention, and generally, the terms "upstream" and "downstream" refer to the gas flow in the turbine engine and here along the longitudinal axis X (even in Figure 1 The terms "axial" and "axially" are defined relative to the longitudinal axis X. Similarly, the terms "radial", "inner" and "outer" are defined relative to a radial axis Z perpendicular to the longitudinal axis X and relative to a distance from the longitudinal axis X.

[0035] The gas generator 3 includes, from upstream to downstream, a low-pressure compressor 4 a , a high-pressure compressor 4 b , a combustion chamber 5 , a high-pressure turbine 6 a , and a low-pressure turbine 6 b .

[0036] The fan 2, surrounded by a fan casing 7 carried by a nacelle 8, divides the air entering the turbine engine into a primary air flow, which passes through the gas generator 3 and flows in particular into the primary duct 9, and a secondary air flow which circulates around the gas generator in the secondary duct 10.

[0037] The secondary air flow is injected by a secondary nozzle 11 terminating the nacelle, whereas the primary air flow is injected to the outside of the turbine engine via an injection nozzle 12 positioned downstream of the gas generator 3 .

[0038] The high-pressure turbine 6a, like the low-pressure turbine 6b, comprises one or more stages. Each stage comprises a stator blade ring mounted upstream of a mobile blade ring. The stator blade ring comprises a plurality of stator or fixed blades, referred to as distributors, which are distributed circumferentially around the longitudinal axis X. The mobile blade ring comprises a plurality of mobile blades, which are distributed equidistantly around the disk centered on the longitudinal axis X. The distributor deflects the aerodynamic flow towards the mobile blades and accelerates them out of the combustion chamber so that the mobile blades are driven in rotation.

[0039] Reference Figure 2 and Figure 3 , each turbine blade, here a moving blade 20 of a high-pressure turbine, comprises a blade 21 rising radially from a platform 22. The platform is carried by a root 23 intended to be embedded in one of the corresponding grooves of the turbine disk. Each blade 21 comprises a pressure side wall 24 and a suction side wall 25 connected upstream by a leading edge 26 and downstream by a trailing edge 27. The pressure side wall (with a pressure side surface 24a) and the suction side wall (with a suction side surface 25a) are opposite each other along a transverse axis perpendicular to the longitudinal axis and the radial axis.

[0040] The blade 20 comprises a cooling circuit 28 intended to cool the wall of the blade which is subjected to the high temperatures of the main air flow passing through and leaving the combustion chamber 5. The cooling circuit 28 comprises an internal cavity 29 extending radially inside the blade, in particular between the pressure side wall 24 and the suction side wall 25. The root 23 comprises a supply channel 30 comprising an inlet 31 for a cooling fluid (here cooling air) upstream of the combustion chamber, for example at the low-pressure compressor, and opening into the cavity 29. The channel 30 also opens onto a radially inner surface 41 of the root of the blade. The cooling circuit also comprises outlet orifices 32 arranged in the vicinity of the trailing edge 27 of the blade. The outlet orifices are oriented along the longitudinal axis X. Furthermore, the outlet orifices 32 are substantially aligned along the radial axis and are evenly distributed.

[0041] exist Figure 3 In , the outlet orifice 32 is arranged in the pressure side wall 24 and opens into the pressure side surface 24a. In this example of embodiment, the cavity 29 is also positioned downstream of the blade, ie more towards the trailing edge.

[0042] from Figure 2 and Figure 3 It can also be seen that the blade comprises a calibration device 33, which is arranged in the path of the cooling air in order to adjust the flow rate of this cooling air. The calibration device 33 comprises a plurality of calibration ducts 34 and is advantageously arranged in the cavity 29 inside the blade. The calibration ducts 34 enable the air flow to be more evenly distributed throughout the orifice without loss of flow rate.

[0043] More specifically, the calibration device 33 comprises a partition 35 extending along a radial axis (in the installed condition) and defined in a mid-plane containing the radial axis. The partition 35 is pierced on both sides by a calibration duct 34 along an axis substantially perpendicular to the mid-plane of the partition. The thickness of the wall of the partition is approximately 1.5 mm. The ducts 34 are aligned and evenly distributed along the radial axis of the partition. Similarly, in the installed condition, the ducts 34 are substantially opposite to the outlet orifices 32 of the blades. In other words, the cooling air flows substantially axially through the calibration duct.

[0044] In the example of this embodiment, Figure 3 As can be seen in detail, the partition 35 is formed as a single piece (integral) with the blade. The partition 35 connects the pressure side wall and the suction side wall inside the cavity 29. The calibration device includes a calibration cavity 42 arranged downstream of the calibration duct 34. The calibration cavity 42 is in fluid communication with the calibration duct and the outlet orifice. In other words, the calibration cavity 42 is arranged in the path of the cooling air toward the outlet orifice (or alternatively between the duct 34 and the outlet orifice). In this way, the cooling air flows to the inner cavity 29 through the duct 30 to pass through the calibration duct 34 and is then received in the calibration cavity acting as a container. Then, the cooling air occupying the entire calibration cavity 42 can flow through the outlet orifice at the same flow rate. Then, we understand that there is a single calibration cavity 42.

[0045] Advantageously, but in a non-limiting manner, the blades are made of a metal alloy and according to a manufacturing method using the lost wax casting technique. Preferably, the metal alloy is nickel-based and may be single-crystalline.

[0046] Reference Figure 4 , each duct has an oblong (or elongated or elliptical) or substantially oblong cross-section. In this specification, the term "oblong" refers to a shape that is longer than it is wide. In particular, the oblong duct extends over a predetermined height H and a predetermined width L. The central axis A of each calibration duct is determined by the intersection of the height and the width in the middle of the calibration duct. The central axis A is perpendicular to the plane B of the partition 35. In this example and in the installed state, the height H of the duct 34 is aligned in a direction parallel to the radial axis, while the width L is aligned in a direction parallel to the transverse axis.

[0047] The ratio of height to width H / L is between 0.5 and 3, and preferably between 1.4 and 2. In particular, the height H is between 1.4 times the width L and 2 times the width L. In this way, the conduits are radially spaced far enough apart to reduce static stresses. The lower limit of the H / L ratio is the limit at which the increase in static stresses becomes noticeable.

[0048] Each conduit 34 also has two rectilinear portions, called "first portion" 36 and "second portion" 37, which are opposite relative to the width L passing through the central axis A. The first portion 36 and the second portion 37 are parallel to each other and extend along the radial axis. This structure makes it possible to locally reduce the stress concentration factor "Kt" and therefore the stress. This is because the tensile force is applied in a direction parallel to the radial axis. The two portions 36, 37 each extend over a distance d between the first top 36a, 37a and the second top 36b, 37b. This distance d is about 0.2 mm.

[0049] Likewise, each duct comprises two circular ends, referred to as “first end” 38 and “second end” 39 , which are opposite relative to a height H passing through the central axis A.

[0050] Advantageously, but in a non-limiting manner, each duct 34 comprises a double radius in order to increase the value of the nominal radius R0 of a conventional duct TA of circular section of the prior art (in Figure 3 The double radius is arranged where the stress is greatest on the wall or periphery of the conduit. In particular, each conduit comprises an arc portion 40, each having a radius R1 referred to as a "first radius R1". These arc portions 40 are positioned along the periphery of the conduit between the first and second straight portions 36, 37 and the first and second circular ends 38, 39, respectively.

[0051] We can see that there are four arc sections 40 of the first radius R1. These sections 40 are symmetrical with respect to a first median plane P1 passing through the central axis and perpendicular to the width L. These sections 40 are also symmetrical with respect to a second median plane P2 passing through the central axis and perpendicular to the height H.

[0052] exist Figure 4 In the example of FIG. 4 , the center of the portion 40 of the cross section of the conduit of radius R1 arranged on one side of the median plane P2 is arranged at one of the ends 36a, 36b, 37a, 37b of the straight portions 36, 37 respectively opposite to the portion 40 with respect to the median plane P1, and the ends are arranged on the same side of the median plane P2 of the portion 40. Of course, different arrangements of the centers of the radius are possible.

[0053] In this example, the value of the first radius R1 is twice the nominal radius R0 of the circular conduit. The passage area of ​​the conduit with a circular cross section is equal to the passage area of ​​the cross section of the conduit with an oblong cross section. The value of the nominal radius R0 is approximately 0.35 mm.

[0054] The first end 38 and the second end 39 are rounded along an arc, each of which has a radius R2, referred to as a “second radius R2”. In this example, the value of the second radius R2 is smaller than the value of the first radius R1. In particular, the value of the second radius is equal to 0.4×R1.

[0055] For a given value of the first radius R1 , the value of the distance d and the value of the second radius R2 enable the cross section of the conduit to be minimized while ensuring a consistent first radius R1 where the stresses are important.

[0056] Figure 5 and Figure 6An ISO scale mapping of the static stresses that are a result of the loads borne by the baffles (primarily the thermal baffles and the centrifugal baffles) carrying the calibration duct 34 through which the cooling air passes before passing through the outlet orifice is shown. Figure 4 In FIG. 1 , we see a prior art catheter having a circular cross section with a nominal radius R0 in perspective and elevation view. Figure 5 In the embodiment, the conduit is a conduit with an oblong cross section with a double radius in particular. We see that under this size and geometry, a comparative analysis by finite element calculation shows that the local static stress on the wall portion of the conduit drops from 1546 MPa (a small point very close to it indicates the maximum stress) of the circular hole to 1018 MPa of the oblong conduit, i.e., a decrease of about 34%.

Claims

1. A turbine engine blade (20), the turbine engine blade comprising: - a blade (21) having a pressure side wall and a suction side wall, the pressure side wall and the suction side wall being connected upstream by a leading edge (26) and downstream by a trailing edge (27), - a cooling circuit (28) comprising an inner cavity (29) extending inside the blade and a plurality of outlet orifices (32), each outlet orifice being oriented substantially along the longitudinal axis X, each outlet orifice communicating with the inner cavity (29) and being arranged in the vicinity of the trailing edge (27), and - a calibration device (33) arranged in the inner cavity (29) and provided with a calibration duct (34) arranged substantially opposite the plurality of outlet orifices (32), the calibration ducts (34) each comprising an oblong cross-section substantially perpendicular to the longitudinal axis, Characterized in that the calibration device comprises a calibration chamber (42) arranged downstream of the calibration conduit (34), the calibration chamber (42) being in fluid communication with the calibration conduit (34) and the outlet orifice (32), and wherein each calibration conduit (34) comprises a first straight portion (36) and a second straight portion (37) opposite each other along a predetermined width L of a central axis A passing through each calibration conduit (34), Each calibration conduit (34) extends over a predetermined height H and comprises a first circular end (38) and a second circular end (39) opposite each other along said predetermined height, Each calibration conduit (34) comprises an arc portion (40) having a first radius R1, the arc portion being symmetrical with respect to a first middle plane (P1) passing through the central axis A and perpendicular to the predetermined width L, and being symmetrical with respect to a second middle plane (P2) passing through the central axis and perpendicular to the predetermined height H, The first circular end (38) and the second circular end (39) are rounded along an arc having a second radius R2, wherein the value of the second radius R2 is smaller than the value of the first radius R1.

2. The impeller blade (20) according to claim 1, characterized in that: The calibration duct (34) is carried by a partition (35) extending radially in the blade and forming upstream of the inner cavity (29) and downstream of the calibration cavity (42) forming a reservoir.

3. The impeller blade (20) according to claim 1 or 2, characterized in that: Each of the first straight portion (36) and the second straight portion (37) extends over a distance d of approximately 0.2 mm.

4. The impeller (20) according to claim 1, characterized in that: The ratio of the predetermined height to the predetermined width is between 0.5 and 2.

5.

5. The impeller (20) according to claim 1, characterized in that: The value of the first radius R1 is equal to twice the nominal radius R0 of the calibration duct having a circular cross section, the passage area of ​​which is equal to the passage area of ​​the cross section of each calibration duct having the oblong cross section.

6. The impeller (20) according to claim 1, characterized in that: The calibration cavity is a single calibration cavity.

7. The impeller (20) according to claim 1, characterized in that: Each calibration conduit (34) includes arc portions, the arc portions are opposite to each other and symmetrical with respect to the second intermediate plane (P2) passing through the central axis, each arc portion is connected to the first straight portion and the second straight portion, and each arc portion includes at least a first radius R1 and a second radius R2, and the second radius R2 is smaller than the first radius R1.

8. A turbine engine turbine comprising at least one blade (20) according to any one of claims 1 to 7.

9. A turbine engine (1) comprising at least one turbine engine turbine according to claim 8.

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