Turbine turbines including CMC nozzles with load absorption and position adjustment

Abstract

A turbine is disclosed, comprising a housing and a turbine nozzle, the turbine nozzle comprising an outer metal shroud (9) fixed to the housing, an inner metal shroud, and a plurality of nozzle segments (20) made of CMC and forming a ring extending between the outer shroud (9) and the inner shroud. Each segment comprises a strut (6), an inner platform, an outer platform, and at least one blade having a hollow profile through which the strut (6) passes. For each blade (20), the outer platform (26) includes an axial stop (260) extending radially outward from the outer platform (26), and the outer metal shroud (9) includes a complementary axial stop (96) extending radially inward from the outer metal shroud (9), the axial stop (260) being upstream and axially supported by the complementary axial stop (96), and machined with a machining angle selected for adjusting the at least one blade in the segment relative to the axial direction (D). A ) orientation.

Description

Technical Field

[0001] The present invention relates to turbines, and more particularly to industrial turbines or aero-engine turbine nozzles comprising turbine nozzles made of ceramic matrix composites or having at least a partial ceramic matrix (hereinafter referred to as CMC material). Background Technology

[0002] The present invention is particularly applicable to gas turbine aircraft engines. However, the present invention can also be applied to other turbines, such as industrial turbines.

[0003] Improved turbine performance and reduced pollution emissions have led to the expectation of increasingly higher operating temperatures.

[0004] Therefore, for components in the hot parts of turbines, the use of ceramic matrix composites, hereinafter referred to as CMC, has been proposed.

[0005] CMC materials are typically formed from fiber reinforcements made of refractory fibers (such as carbon fibers or ceramic fibers), which are densified by a ceramic matrix or at least partially made of ceramic.

[0006] These materials possess remarkable thermostructural properties (i.e., the mechanical properties that enable them to form structural components) and the ability to retain these properties at high temperatures. Furthermore, CMC materials have a significantly lower mass per unit volume than metallic materials traditionally used for components in the hot sections of turbines.

[0007] Therefore, documents WO 2010 / 061140, WO 2010 / 116066, and WO 2011 / 080443 describe the production of turbine impeller blades made of CMC with built-in platforms and heels. In particular, documents WO 2010 / 146288, FR 2979 662, and EP 2 443 318 also provide information on the application of CMC material for turbine nozzles.

[0008] Traditional metal turbine nozzles are crown-shaped, consisting of several assembled segments. Each segment includes an inner platform, an outer platform, and multiple airfoils extending between and attached to the inner and outer platforms. The juxtaposed inner platforms form an inner shield, while the juxtaposed outer platforms form an outer shield. The inner and outer shields define the gas flow path within the nozzle.

[0009] Introducing nozzles made of CMC (e.g., high-pressure nozzles) allows for a higher maximum permissible temperature compared to metal nozzles, thereby reducing the amount of cooling air used. This enables improvements in turbine performance.

[0010] However, CMC is more sensitive to certain mechanical stresses due to its properties that differ from those of metals. Specifically, CMC has greater stiffness and lower expansion. It performs well under compression, but its allowable tensile stress is lower than that of metals.

[0011] Furthermore, due to the difference in thermal expansion between CMC and metal, CMC components are difficult to integrate into metallic environments. This is even more complicated in turbines, especially in the high-pressure sections, because the environment is hot, which exacerbates the difference in thermal expansion coefficients between materials, and the aerodynamic loads experienced by the high-pressure nozzles are also higher in this turbine region.

[0012] Nozzles made of CMC are known, such as turbine nozzles, which include an outer support shroud fixed to a housing, an inner support shroud, and multiple nozzle segments forming a crown extending between the outer and inner support shrouds, and are made of CMC. Each nozzle segment is supported on the inner and outer support shrouds and includes an inner platform, an outer platform, and at least one airfoil extending between and attached to them.

[0013] However, improvements are needed to the known solutions regarding the deterministic retention of CMC nozzle segments and inner shrouds (particularly in terms of axial retention of nozzle segments and absorption of aerodynamic loads).

[0014] Furthermore, a significant pressure differential is applied in both the radial and axial directions to the housing below the nozzle. This housing serves to form a seal between the rotor and stator. This pressure differential is a source of load that, given the allowable stress of the material, would result in a high load if applied to the CMC.

[0015] It is also known (particularly from documents FR 3 061 928 and FR 2 973 435) of a nozzle as described above, which further includes a reinforcing strut extending radially between the two platforms inside the blade, thereby allowing the nozzle to be held on the housing by the strut.

[0016] However, this solution absorbs the loads associated with the pressure differential below the nozzle and the aerodynamic loads on the CMC crown via the strut. Furthermore, due to the aforementioned reasons related to the different mechanical behaviors between the CMC and the metallic material, it is difficult to position the CMC component in a metallic environment by providing a flange.

[0017] During turbine operation, a significant radial clearance is generated between the strut and the airfoil it passes through. More specifically, because the strut expands more than the CMC airfoil, a radial clearance greater than 0.5 mm, or even greater than 1 mm, may occur between the strut and the airfoil it passes through. This radial clearance introduces uncertainty in the airfoil's position, and the aerodynamic downforce becomes random, moving upwards or downwards depending on the radial composite load of the aerodynamic loads.

[0018] In nozzles that are entirely metallic, the nozzle is typically cast and several airfoils form a single nozzle (usually in groups of two or three, i.e., each segment has two or three airfoils). In this case, the channel cross-section is controllable and reproducible due to the manufacturing process.

[0019] This is no longer the case when blades are made of CMC materials integrated into a metallic environment for several reasons. First, due to the lack of tolerance control on CMC components, because CMC material airfoils are not subjected to positional stresses to avoid damage, and because of the contact between CMC material airfoils and load-absorbing metal struts.

[0020] Therefore, it is necessary to improve the deterministic retention of the CMC nozzle in this solution. Summary of the Invention

[0021] The present invention aims to alleviate the above-mentioned disadvantages and overcome the above-mentioned difficulties by providing a turbine turbine comprising a turbine nozzle made at least partially of CMC, the installation of which is simplified and adapted to deterministically retain the nozzle segment while allowing its nozzle segment to deform independently of the metal interface component, while also ensuring a satisfactory seal.

[0022] Another objective of this invention is to allow for the axial positioning of the adjustable airfoil on the upper cover.

[0023] One aspect of the present invention provides a turbine turbine comprising: a housing; an outer support shroud made of metal, the outer support shroud being fixed to the housing and defining an axial and radial direction; an inner support shroud made of metal; and an annular turbine nozzle comprising a plurality of nozzle segments made of a ceramic matrix composite material, the plurality of nozzle segments forming a crown extending between the outer support shroud and the inner support shroud.

[0024] In addition, each segment includes an inner platform, an outer platform, and at least one airfoil extending radially between the inner and outer platforms and having a hollow profile that defines a radially extending inner shell. The turbine also includes at least one strut for each segment, which is fixed to a metal shield and passes radially through the segment via the shell of the airfoil.

[0025] According to the general features of the invention, for each segment, the outer platform includes a radially outer surface facing the outer metal shroud and an axial stop extending radially outward from the radially outer surface of the outer platform, and the outer metal shroud includes a radially inner surface facing the outer platform and a complementary axial stop extending radially outward from the radially inner surface of the outer metal shroud, the axial stop being supported against the complementary axial stop along the axial direction and located upstream of the complementary axial stop relative to the direction of the airflow to flow through the turbine, and the surface of the axial stop in contact with the complementary axial stop having a machined angle relative to a plane orthogonal to the axial direction, the machined angle being selected for adjusting the orientation of at least one blade of the segment relative to the axial direction.

[0026] Therefore, the present invention provides a solution for controlling the channel cross-section of flow through a flow path in a nozzle, comprising an assembly of a hollow CMC airfoil through which a metal strut passes but is held in a non-stressed position.

[0027] The planar support between the nozzle segment and the outer metal shield fixed to the support post—that is, between two planar surfaces—eliminates the rotational freedom of the nozzle ring support structure (particularly the support structure formed by the outer metal shield 9 and the housing) about the radial axis of the nozzle ring, and further eliminates the rotational freedom along the axial direction D. A —That is, the translational degree of freedom along the engine centerline. This allows for ensuring that the nozzle is kept in the proper position, and thereby controlling the nozzle's channel cross-section during operation, with a channel cross-section that can be replicated on an airfoil-by-airfoil basis, since the contact surface of the axial stop is machined to ensure this.

[0028] According to the first aspect of the turbine, the strut and the outer metal shield can be made into a single component.

[0029] The proposed structure allows for control of the channel cross-section of the hollow CMC material airfoil positioned on the metal strut, while keeping it in an unstressed position.

[0030] According to the second aspect of the turbine, the strut and the outer metal shield can be made into a single component.

[0031] This allows for the limitation of any potential leaks when segmented shields or struts are added to the outer shield.

[0032] According to the third aspect of the turbine, the outer metal shield may include an upstream end and a downstream end along the axial direction, with a complementary axial stop located on the downstream end.

[0033] According to the fourth aspect of the turbine, the strut can be hollow.

[0034] Therefore, the strut allows air to be delivered to the radially inner chamber of the inner shroud for pressurization, thereby preventing air circulating in the flow path extending between the inner and outer platforms of the nozzle segment from being redirected outside the flow path, which would reduce performance and increase the risk of component overheating.

[0035] Another subject of the invention is a turbine that includes the turbine turbine as defined above.

[0036] The present invention also provides a subject of an aircraft comprising at least one turbine as defined above.

[0037] The present invention also has the subject matter of a method for manufacturing a turbine as defined above, the method comprising a first step of forming a ring made of a ceramic matrix composite material, a second step of controlling the profile of the ring thus formed, a third step of determining the machining angle of the surface of an axial stop member in contact with a complementary axial stop member to adjust the orientation of the at least one blade relative to the axial direction, a fourth step of machining the surface of the axial stop member in contact with the complementary axial stop member at the determined angle, and a fifth step of assembling the turbine. Attached Figure Description

[0038] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view of a segment of a turbine according to one embodiment of the present invention.

[0039] [ Figure 2 ] Figure 2 yes Figure 1 A schematic three-dimensional top view of the turbine's components.

[0040] [ Figure 3 ] Figure 3 It shows Figure 1 A schematic, bottom-view perspective of the outer support shield of the turbine.

[0041] [ Figure 4 ] Figure 4 The diagram illustrates the angles formed by the airfoil before machining the support surface of the axial stop, for three different examples.

[0042] [ Figure 5 ] Figure 5 It shows: targeting Figure 4 The three structures, and the machining angle of the axial stop of the airfoil.

[0043] [ Figure 6 ] Figure 6 It is presented schematically: targeting Figure 4 The three constructions differ in the channel cross-section between the two airfoils. Detailed Implementation

[0044] Figure 1 A schematic cross-sectional view of a segment of a turbine according to an embodiment of the present invention is shown. Figure 1 As shown in the middle section, a high-pressure turbine 1 of a turbine (e.g., an aircraft turbojet engine) includes a plurality of fixed nozzles 2, which are aligned with the flow direction of the airflow F within the turbine 1 (in the direction of airflow F). Figure 1 (As indicated by the arrow) The upper phases alternate and are installed in the turbine housing.

[0045] Each impeller includes multiple blades with an inner shroud, and at least one airfoil extending from and connected to the inner shroud. On the inner side of the inner shroud, the blades extend at their roots, which engage within the housing of the disc. On the outer side, the tip of each blade faces an abrasive material carried by a ring to provide a seal at the blade tip.

[0046] Throughout the text, the terms “inner” or “internal” and “outer” or “external” refer to the axial direction D of turbine 1 relative to turbine 1. A It is used for the position or orientation of the axis of rotation.

[0047] The impeller blades can be conventional metal blades or blades made of CMC material, for example, as described in documents WO 2010 / 061140, WO 2010 / 116066 and WO 2011 / 080443.

[0048] At least one nozzle in the nozzle 2 of turbine 1 is formed by combining several annular nozzle segments 20 made of CMC material to form a complete ring. Arrow D A The arrow D indicates the axial direction of nozzle 2. R Indicates the radial direction of nozzle 2, and marks D. C Indicates the circumferential direction.

[0049] Each nozzle segment 20 of the nozzle 2 includes an inner platform 24, an outer platform 26, and an airfoil 28 extending between and attached to the inner platform 24 and the outer platform 26. In a variant, several airfoils may extend between the inner and outer platforms of the same nozzle segment. Once assembled with the housing of the turbine 1, the segment 20 forms a single crown of the nozzle 2, which has an inner shield formed by the juxtaposition of the inner platforms 24 of the segment 20 and an outer shield formed by the juxtaposition of the outer platforms 26 of the segment 20.

[0050] The inner and outer shields together form a fluid flow path 45, within which the airflow F flows during the operation of the turbine 1.

[0051] Throughout the text, the terms “upstream” and “downstream” are used with reference to the direction of airflow F in the path 45 indicated by the arrow.

[0052] Each inner platform 24 has an outer surface 24e intended to contact the airflow F and thus radially positioned to face the outer platform 26 forming the outer shroud. Furthermore, the inner platform 24 has an inner surface 24i positioned facing the axis of rotation of the turbine 1.

[0053] Each outer platform 26 has an outer surface 26e that is configured to face the radially external outer casing. In addition, the outer platform 26 has an inner surface 26i that is intended to contact the airflow F and is therefore radially configured to face the inner platform 24 that forms the inner shroud and to face the axis of rotation of the turbine 1.

[0054] The nozzle 2 is held between the inner metal shield 5 and the outer metal shield 9, and a crown formed by assembling the annular segment 20 of the nozzle 2 extends between the inner metal shield 5 and the outer metal shield 9. The outer metal shield 9 is fixed to the housing and extends radially along the direction D. R It has an inner surface 91 and an outer surface 92.

[0055] like Figure 1 And simultaneously, a schematic top-view perspective view of nozzle segment 20 is shown. Figure 2 As shown, each airfoil 28 has a hollow profile with an inner shell 280 extending over the entire height of the airfoil 28, i.e., between the inner platform 24 and the outer platform 26 of the annular segment 20. The inner platform 24 of each nozzle segment 20 includes an orifice 245, the shape of which corresponds to a cross-section of the inner shell 280 in the plane extending from the inner platform 24. Similarly, the outer platform 26 of each nozzle segment 20 includes an orifice 265, the shape of which corresponds to a cross-section of the inner shell 280 in the plane extending from the outer platform 26. The orifices 245 and 265 of the inner and outer platforms 24 and 26 are formed in the extension of the inner shell 280 of the airfoil 28.

[0056] The inner housing 280 of the airfoil 28 and the orifices 245 and 265 of the inner platform 24 and the outer platform 26 can be connected to a cooling system that delivers cooling airflow from the housing to the airfoil 28 and the inner platform 24 and the outer platform 26.

[0057] like Figure 1 And a schematic bottom-view perspective view showing the outer support cover 9. Figure 3 As shown, for each nozzle segment 20, the outer support shield 9 includes a radial direction D extending from the inner surface 91 of the outer metal shield 9. R Extended pillar 6.

[0058] As shown in the figure, the support column 6 includes a rod 62, which extends radially D internally. R Extending protrudingly from the head 61 and configured to pass through the outer metal shield 9, the inner shell 280 of the airfoil 28, and the openings 245 and 265 of the inner platform 24 and the outer platform 26 aligned with the inner shell 280 of the airfoil 28.

[0059] In other words, the support 6 includes a first end 6i that is radially inward and a second end 6e that is radially outward, and a portion of the support 6 between the first end 6i and the second end 6e that is substantially along the radial direction D. R The extended main body 62.

[0060] The support column 6 is hollow to deliver air into a chamber radially inward within the inner shroud for pressurization, thereby preventing air circulating in the flow path extending between the inner and outer platforms of the nozzle segment from being redirected out of that path, which would degrade performance and increase the risk of component overheating. The support column 6 therefore includes a radial direction D between its first end 6i and second end 6e. R Extended inner shell 60.

[0061] The outer metal shield 9 includes a metal shield along the axial direction D. A The outer metal shield 9 has an upstream end 94 and a downstream end 95. At its downstream end 95, the outer metal shield 9 includes a shoulder 96 that extends radially inward from the inner surface 91 of the outer metal shield 9 over the entire circumference of the outer metal shield 9 and along the axial direction D. A Forming a support surface 960, the support surface 960 of the outer metal shield is along the axial direction D A The directional flow is directed to face the flow of the current F—in other words, it faces upstream.

[0062] The outer platform 26 includes an axial stop 260 extending radially outward from its outer surface 26e. The axial stop 260 has an axial support surface 262 that extends axially along the flow direction F in the axial direction D. A Orientation, i.e., facing downstream. Therefore, the axial support surface 262 of the axial stop 260 faces and even contacts the support surface 960 of the shoulder 96 of the outer metal shield 9.

[0063] To ensure that each segment 20 of the annular nozzle 2 has the same channel cross-section between these airfoils 28, the airfoils are adjusted relative to the axial direction D by machining the axial support surface 262 of the axial stop 260 during the assembly of the turbine 1 before the assembly of the nozzle 2 with the outer metal shield 9 is completed. A Orientation.

[0064] like Figure 4As shown, during the formation of CMC material segment 20, segments 20 can be slightly different from each other, and in the radial direction D R In the orthogonal plane, the angle α formed between the axial support surface 262 of the axial stop 260 and the direction of the airfoil 28 (particularly the direction of the trailing edge 282 of the airfoil 28) differs slightly. Figure 4 In this process, three distinct angles α1, α, and α2 are observed, specifically exhibiting the dimensional relationship α1 < α < α2. Figure 4 In the diagram, the direction of the reference airfoil 28 forming angle α is shown as a dashed line each time, while for two airfoils with angles α1 and α2, the direction of the actual airfoil 28 is shown as a dotted line. The difference between the actual angles (α1 and α2) and the reference angle α forms the variation angles denoted as β1 and β2, respectively.

[0065] like Figure 5 As shown, the change in the direction of the airfoil 28 causes a change in the distance L between the airfoils 28, and thus a change in the channel cross section. Figure 5 Three pairs of segments are shown, wherein the top airfoil always has the same trailing edge direction, in this case, forming a reference angle α with the axial support surface 262 of the axial stop 260 of the outer platform 26, while the bottom airfoil has a direction that first forms an angle α1, then the same reference angle α, and then an angle α2. This results in three different lengths L, L1, and L2 among the airfoils of the three pairs of airfoils, and thus three different channel sections.

[0066] To counteract any such changes and to adjust the orientation of segment 20 and thus the orientation of airfoil 28, the axial support surface 262 of the axial stop 260 of the outer platform 26 is machined to have an angle corresponding to the changing angle β1 or β2, for example, as shown in the top view of three different axial stops 260. Figure 6 As shown.

[0067] Furthermore, the inner support shield 5 includes an aperture configured to receive the strut 6. The strut 6 provides a means for attaching the CMC nozzle segment 20 from the top while minimizing bending moment, such that the bending length is reduced by approximately half due to the strut 6 passing through the nozzle segment. Therefore, each nozzle segment 20 is deterministically held, i.e., held in a manner that prevents the nozzle segment 20 from initiating vibration and controls its position, while also allowing the nozzle segment 20 to deform under the influence of temperature and pressure, particularly independently of the metal interface components.

[0068] If each nozzle segment is to include multiple airfoils, the turbine will include a maximum of the corresponding number of struts for each nozzle segment.

[0069] The turbine according to the invention includes a turbine nozzle at least partially made of CMC, the installation of which is simplified and adapted to deterministically retain nozzle segments while allowing these segments to deform independently of the metal interface components, and simultaneously improving the seal between the strut and the outer metal shield.

Claims

1. A method of manufacturing a turbine wheel of a turbomachine, wherein, The turbine includes: a housing; an outer support shield made of metal, the outer support shield being fixed to the housing and defining an axial and radial direction; an inner support shield made of metal; and an annular turbine nozzle comprising a plurality of nozzle segments made of a ceramic matrix composite material, the segments forming a crown extending between the outer support shield and the inner support shield. Each segment includes an inner platform, an outer platform, and at least one airfoil extending radially between the inner platform and the outer platform, the airfoil having a hollow profile defining a radially extending inner shell. The turbine also includes at least one strut for each segment, the strut being fixed to the outer support shield and passing radially through the segment via the inner shell of the airfoil; For each segment, the outer platform includes a radially outer surface facing the outer support shroud and an axial stop extending radially projecting from the radially outer surface of the outer platform. The outer support shroud includes a radially inner surface facing the outer platform and a complementary axial stop extending radially projecting from the radially inner surface of the outer support shroud. The axial stop abuts against the complementary axial stop in the axial direction and is located upstream of the complementary axial stop relative to the direction of the airflow to be passed over the turbine. The surface of the axial stop that contacts the complementary axial stop has a machined angle relative to a plane orthogonal to the axial direction. This machined angle is selected to adjust the orientation of at least one blade of the segment relative to the axial direction. In the first step, a nozzle is formed from a ceramic matrix composite material; then in the second step, the orientation of its blade profile is controlled; then in the third step, the machining angle of the surface of the axial stop in contact with the complementary axial stop is determined to adjust the orientation of the at least one blade relative to the outer support shroud; in the fourth step, the surface of the axial stop in contact with the complementary axial stop is machined; and in the fifth step, the nozzle is assembled on the outer support shroud, the inner support shroud, and the turbine housing.

2. The method of claim 1, wherein, The support column and the outer support cover are manufactured as a single component.

3. The method of claim 1, wherein, The outer support cover includes an upstream end and a downstream end along the axial direction, and the complementary axial stop is located on the downstream end.

4. The method of claim 1, wherein, The support pillar is hollow.

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