WO2019240754A2

WO2019240754A2 - Composite ceramic and metallic vane for combustion turbine engine

Info

Publication number: WO2019240754A2
Application number: PCT/US2018/036881
Authority: WO
Inventors: Yevgeniy P. Shteyman; David Gamblin; Robert S. ANGEL
Original assignee: Siemens Aktiengesellschaft; Siemens Energy, Inc.
Priority date: 2018-06-11
Filing date: 2018-06-11
Publication date: 2019-12-19
Also published as: WO2019240754A3

Abstract

A vane assembly (50) includes a ceramic-matrix-composite airfoil (52), having an integral tenon (68, 70) on at least one airfoil tip (64, 66). A corresponding metallic, outer (80) or inner (120) diameter platform has a platform cavity (84, 124), defined by a cavity wall (86, 126), which receives and circumscribes the tenon. The cavity wall is pre-tensioned about its corresponding tenon circumference (72, 78) to maintain compression of the tenon transverse the central axis (54) of the airfoil when the vane assembly is at a maximum operating temperature within a combustion turbine engine (20). In some embodiments, the platform incorporates one or more clamping jaws (92, 94, 132, 134), for maintaining tenon compression. In other embodiments, the clamping jaw incorporates an expansion joint (96, 98, 100, 136, 138, 140) for accommodating relative radial expansion of an inner diameter and/or an outer diameter platform and the airfoil during engine operation.

Description

COMPOSITE CERAMIC AND METALLIC VANE FOR COMBUSTION

TURBINE ENGINE

TECHNICAL FIELD

[0001] The invention relates to vanes for combustion turbine engines, having ceramic airfoils that are secured to inner and outer diameter, metallic platforms. More particularly, the invention relates to composite vanes, which accommodate disparate thermal expansion rates of the metallic platforms and the ceramic airfoil.

BACKGROUND [0002] Ceramic matrix composite (“CMC”) structures are being incorporated into gas turbine engine components as insulation layers and/or structural elements of such components, such as insulating sleeves, ring segments, vanes, and turbine blades. These CMC structures provide better oxidation resistance, and higher temperature capability, in the range of approximately 1150 degrees Celsius (“C”) for oxide/oxide (“Ox/Ox”) based ceramic matrix composites, and up to around 1350 degrees C for

Silicon Carbide fiber-Silicon Carbide core (“SiC-SiC”) based ceramic matrix composites; whereas nickel- or cobalt- or iron-based (“Ni-Co-Fe”) superalloys are generally limited to approximately 950 to 1000 degrees Celsius under similar operating conditions within engines. While 1150 degrees C (1350 degrees C for SiC- SiC based CMCs) operating capability is an improvement over traditional Ni-Co-Fe- based superalloy temperature limits, mechanical strength (e.g., load bearing capacity) of CMCs is also limited by grain growth and reaction processes with the matrix and/or the environment at 1150 /1350 degrees C and higher. Therefore, some combustion- turbine engine components, such as blades and ring segments, utilized hybrid combinations of CMC and superalloy or other metals structures, which include the benefits higher temperature resistance of the CMC material and mechanical strength of the metals. However, inclusion of mating CMC and superalloy substrates in combustion turbine engines presents new and different thermal expansion mismatch challenges. During gas turbine engine operation, superalloy and CMC materials have different thermal expansion properties. Superalloy material expands more than the CMC material, which in extreme cases leads to crack formation and/or delamination in the CMC material. In some cases expansion rates between the CMC material and the superalloy or other metallic material are affected by the local ambient temperatures of the respective components.

SUMMARY OF INVENTION

[0003] Exemplary vane assembly embodiments described herein include a ceramic- matrix-composite airfoil, having an integral tenon on at least one airfoil tip. A corresponding metallic, inner diameter (ID) or outer diameter (OD) platform has a platform cavity, defined by a cavity wall, which receives and circumscribes the tenon. The cavity wall is pre-tensioned about its corresponding tenon circumference to maintain compression of the tenon transverse the central axis of the airfoil when the vane assembly is at a maximum operating temperature within a combustion turbine engine. Pre-tensioning of the cavity wall about the tenon circumference compensates for the greater relative thermal expansion rate of the metallic platform compared to that of the ceramic tenon. Without pre-tensioning the platform cavity wall, it may expand circumferentially relative to the tenon circumference during engine heating: in turn allowing airfoil movement relative to the ID and OD platforms. Such unrestrained airfoil movement could increase vibration during engine operation and decrease airflow efficiency in the combustion gas path. In some embodiments, the platform incorporates one or more clamping jaws, for maintaining tenon compression. In other embodiments, the clamping jaw(s) incorporate(s) an expansion joint for accommodating relative radial expansion of an inner diameter and/or an outer diameter platform and the airfoil during engine operation. In some embodiments, a CMC ceramic platform covers the metallic ID and/or OD platform, providing additional thermal protection to the metallic platform. In some embodiments, the ceramic airfoil, and/or the ceramic platform are a replaceable element, so that the metallic platforms can be refurbished for reuse. [0004] Exemplary embodiments of the invention feature a vane assembly for a combustion turbine engine. The vane assembly includes a ceramic-matrix-composite airfoil, having a radially aligned central axis, with opposed concave and convex surfaces that extend along the central axis, and that are conjoined at a leading edge and a trailing edge. The airfoil also has an inner diameter airfoil tip, and an outer diameter airfoil tip. The vane assembly also includes a metallic, inner diameter (“ID”) platform rigidly coupled to the inner diameter airfoil tip, with an ID platform surface facing the airfoil. The vane assembly also includes a metallic, outer diameter platform rigidly coupled to the outer diameter airfoil tip, with an OD platform surface facing the airfoil. A tenon is integrally formed in the airfoil; it projects outwardly from the inner and/or outer diameter tip of the airfoil. Each respective tenon has a distal tenon tip and a tenon circumferential surface between its corresponding distal tenon tip and its corresponding inner or outer diameter airfoil tip. A platform cavity, defined by a cavity wall, is formed the inner and/or the outer diameter platform. Each platform cavity respectively receives and circumscribes a corresponding tenon circumferential surface of the airfoil therein. Each corresponding cavity wall is pre- tensioned about its corresponding tenon circumference, in order to maintain compression of the tenon transverse the central axis of the airfoil when the vane assembly is at a maximum operating temperature within a combustion turbine engine.

[0005] The respective features of the exemplary embodiments of the invention that are described herein may be applied jointly or severally in any combination or sub- combination.

BRIEF DESCRIPTION OF DRAWINGS

[0006] The exemplary embodiments of the invention are further described in the following detailed description in conjunction with the accompanying drawings, in which:

[0007] FIG. 1 is a partial axial, cross sectional view of a gas or combustion turbine engine, incorporating one or more rows of vane assemblies, with composite CMC airfoil and metallic ID/OD platforms, which are constructed in accordance with exemplary embodiments that are further described herein;

[0008] FIG. 2 is an outer diameter, perspective view of a vane assembly, which is constructed in accordance with exemplary embodiments that are further described herein;

[0009] FIG. 3 is an inner diameter, perspective view of the vane assembly of FIG. 2;

[0010] FIG. 4 is a radial cross-section, of the outer diameter platform and airfoil tenon interface, taken along 4-4 of FIG. 2;

[0011] FIG. 5 is a radial cross-section, of the inner diameter platform and airfoil tenon interface, taken along 5-5 of FIG. 3;

[0012] FIG. 6 is a radial cross-section of an interface connection of first and second portions of the OD platform, taken along 6-6 of FIG. 2;

[0013] FIG. 7 is a fragmentary, perspective view of the airfoil of FIG. 2, showing its inner and outer diameter tenons, along with its internal cooling passages;

[0014] FIG. 8 is an outer diameter, perspective view of an OD platform and airfoil of a vane assembly, which is constructed in accordance with an alternate embodiment that is further described herein;

[0015] FIG. 9 is an outer diameter, perspective view of an OD platform and airfoil of a vane assembly, which is constructed in accordance with another alternate embodiment further described herein; and

[0016] FIG. 10 is a fragmentary, plan view of another embodiment of an OD platform cavity and airfoil tenon, pre-tensioned interface. [0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale.

DESCRIPTION OF EMBODIMENTS

[0018] Exemplary embodiments of the invention are utilized in a vane assembly for a combustion turbine engine. Embodiments of the vane assembly include a ceramic- matrix-composite airfoil, having an integral tenon on at least one airfoil tip. In some embodiments, the airfoil has an integral tenon on both the inner and outer diameter airfoil tips. In these embodiments, a corresponding metallic, inner- or outer-diameter platform has a platform cavity, defined by a cavity wall, which receives and circumscribes a circumference of the tenon. The cavity wall is pre-tensioned about its corresponding tenon circumference to maintain compression of the tenon transverse the generally radially aligned, central axis of the airfoil when the vane assembly is at a maximum operating temperature within a combustion turbine engine. In some embodiments, the platform incorporates one or more clamping jaws, for maintaining tenon compression. In some embodiments, the ID and/or OD metallic platform is a split platform. In some embodiments, two parts of the split platform respectively incorporate opposed clamping jaws. In other embodiments, one or more of the clamping jaws incorporates an expansion joint for accommodating relative radial expansion of an inner diameter and/or an outer diameter platform and the airfoil during engine operation. In some embodiments, the airfoil defines cooling channels that are in communication with corresponding cooling passages of the ID and/or OD platforms of the vane assembly. In some embodiments, the ID and/or OD metallic platform has an overlaying CMC platform, facing the combustion-gas flow path, which thermally insulates the metallic platform.

[0019] FIG. 1 shows a gas turbine engine 20, having an engine casing 22, a multi stage compressor section 24, a combustion section 26, a multi-stage turbine section 28 and a rotor 30. One of a plurality of basket-type combustors 32 is coupled to a downstream transition 34 that directs combustion gasses from the combustor to the turbine section 28. Atmospheric pressure intake air is drawn into the compressor section 24 generally in the direction of the flow arrows F along the axial length of the turbine engine 20. The intake air is progressively pressurized in the compressor section 24 by rows of rotating compressor blades 36 and directed by mating rows of compressor vanes 38 to the combustion section 26, where it is mixed with fuel and ignited. The ignited fuel/air mixture, now under greater pressure and velocity than the original intake air, is directed through a transition 34 to the sequential rows of vanes 40 and blades 42 in the turbine section 28. The engine’s rotor 30 and associated shaft retains the plurality of rows of turbine blades 42. The vane row 40 includes an inner diameter ring segment 46, an outer diameter ring segment 48, and a row of circumferentially spaced, vane airfoils 49 that span radially the respective ring segments 46, 48. The vane row 40 comprises a plurality of circumferentially abutting, vane assemblies.

[0020] An exemplary embodiment of a vane assembly 50 is shown in FIGs. 2-7. Referring to FIGs. 2 and 7, the vane assembly 50 includes a replaceable, ceramic- matrix-composite airfoil 52, having a radially aligned central axis 54, with opposed concave 56 and convex 58 surfaces that extend along the central axis, and that are conjoined at a leading edge 60 and a trailing edge 62. The airfoil has an inner- diameter airfoil tip 64, and an outer-diameter airfoil tip 66. An inner diameter (ID) tenon 68 is integrally formed in the airfoil 52, and projects outwardly from the ID airfoil tip 64. The ID tenon 68 has an ID tenon tip 70 and an ID-tenon, circumferential surface 72 that is formed between its corresponding tenon tip and the ID airfoil tip 64. Similarly, an outer diameter (OD) tenon 74 is integrally formed in the airfoil 52, and projects outwardly from the OD airfoil tip 66. The OD tenon 74 has an OD tenon tip 76 and an OD-tenon, circumferential surface 78 that is formed between its corresponding tenon tip and the OD airfoil tip 66.

[0021] Referring to FIGs. 2-7, the vane assembly 50 has a metallic, outer diameter (OD) platform 80. An OD platform surface 82 faces the airfoil 52, and the OD airfoil tip 66. The OD platform 80 defines an OD platform cavity 84, defined by an OD platform cavity wall or walls 86, that receives the airfoil 52 along the latter’s circumferential surface 78 of the OD tenon 74. The OD platform 80 has a split- platform construction, comprising a first OD-platform portion 88 that is proximate the leading edge 60 of the airfoil 52, and a second OD-platform portion 90 that is proximate the trailing edge 62 of the airfoil. In this split-platform construction embodiment, the first 88 and second 90 OD-platform portions are biased against each other, functionally forming a clamping mechanism for clamping the circumferential surface 78 of the OD tenon 74 there between, and maintaining compression of the tenon transverse the central axis 54 of the airfoil 52. The first OD-platform portion 88 forms a first clamping jaw 92 that comprises a portion of the OD platform cavity wall 86. The second OD-platform portion 90 forms a second clamping jaw 94 that comprises a portion of the OD platform cavity wall 86.

[0022] A threaded, shoulder-rod fastener 96, along with captured sliding plates 98 and mating threaded nuts 100 clamp the first 92 and second 94 jaws relative to each other, compressing/pre-tensioning the OD tenon 74. Other types of compressive fasteners, including shoulder bolts, are substituted for the shoulder-rod fastener 96 in other embodiments. The shoulder-rod fastener 96 is received in apertures formed in the OD tenon 74, the first 92 and second 94 jaws of the first 88 and second 90 OD- platform portions and the sliding plates 98. Apertures formed in the first 92 and second 94 jaws of the aforementioned platform portions are of larger diameter than the corresponding outer diameter portions of the shoulder-rod fastener 96, allowing freedom of movement, along, or parallel to the central axis 54 of the airfoil 52. A long axis of elongated apertures formed in the sliding plates 98 also allow relative freedom of movement of the shoulder-rod fastener 96, along or parallel to the central axis 54, but they restrain relative circumferential movement. In this manner, the sliding plate 98, and shoulder-rod fastener 96 interface functions as a thermal expansion joint during engine operation, allowing for differential expansion rates between the airfoil 52 and the OD platform 88 along the central axis 54, but maintaining relative transverse alignment of those structures relative to the central axis. Thus, the expansion joint function of the shoulder-rod fastener 96 and sliding plates 98 interface compensate for more rapid thermal expansion of the respective, metallic, ID 120 and OD 80 platforms growth in the central axis 54 orientation of the vane assembly 50, without compressing the ceramic airfoil 52 that is interposed between and bridges those platforms. Expansion joint maintenance of relative transverse alignment of the airfoil 52 and its OD platform 88 reduces likelihood of transient engine vibration or reduction of the engine’s aerodynamic efficiency during transient heating of the engine.

[0023] The first 88 OD-platform portion defines a first flange portion 102 that is coupled to a mating second flange portion 104 of the second 90 OD-platform portion, by shoulder bolts 106, threaded nuts 108, and washers 110. A CMC material, ceramic OD platform 112 covers the OD platform surface 82, and abuts and/or circumscribes the ceramic airfoil 52. In some embodiments, the ceramic OD platform 112 incorporates an aperture that slidably receives and abuts against the concave 56 and the convex 58 airfoil outer surfaces. In other embodiments, the ceramic OD platform is sandwiched between the OD airfoil tip 66 and the OD platform surface 82. Lips 114 formed in the ceramic OD platform 112 engage with corresponding OD hooks 116 formed in the respective first 88 and second 90 OD platform portions. Clearances between the lips 114 and the hooks 116 are sufficient to accommodate different rates of thermal expansion of the CMC, OD platform 112 and the corresponding metallic platform portions 88, 90. The ceramic OD platform 112 is a replaceable component that provides thermal insulation for the metallic first 88 and second 90 OD platform portions, and all of the aforementioned, metallic fastening hardware that is below the OD platform surface 82. In this way, none of the fastening hardware, including by way of example the shoulder-rod fastener 96, captured sliding plates 98, nuts 100, shoulder bolts 106, nuts 108, or washers 110 is directly exposed to combustion gas.

[0024] Referring to FIGs. 2, 3, 5 and 7, the vane assembly 50 also has a metallic, inner diameter (ID) platform 120. General structure and function of components in the ID platform 120 structure are similar to those previously described for the OD platform 80. An ID platform surface 122 faces the airfoil 52, and the ID airfoil tip 64. The ID platform 120 defines an ID platform cavity 124, defined by an ID platform cavity wall or walls 126, that receives the airfoil 52 along the latter’s circumferential surface 72 of the ID tenon 68. The ID platform 120 has a split-platform construction, comprising a first ID-platform portion 128 that is proximate the leading edge 60 of the airfoil 52, and a second ID-platform portion 130 that is proximate the trailing edge 62 of the airfoil. In this split-platform construction embodiment, the first 128 and second 130 ID-platform portions are biased against each other, functionally forming a clamping mechanism for clamping the circumferential surface 72 of the ID tenon 68 there between, and maintaining compression of the tenon transverse the central axis 54 of the airfoil 52. The first ID-platform portion 128 forms a first clamping jaw 132 that comprises a portion of the ID platform cavity wall 126. The second ID-platform portion 130 forms a second clamping jaw 134 that is a portion of the ID platform cavity wall 126.

[0025] A threaded, shoulder-rod fastener 136 captured sliding plates 138 and mating threaded nuts 140 clamp the first 132 and second 134 jaws relative to each other, compressing/pre-tensioning the ID tenon 68. Other types of compressive fasteners, including shoulder bolts, are substituted for the shoulder-rod fastener 136 in other embodiments. The shoulder-rod fastener 136 is received in apertures formed in the ID tenon 68, the first 132 and second 134 jaws of the first 128 and second 130 ID- platform portions and the sliding plates 138. Apertures formed in the first 132 and second 134 jaws of the aforementioned platform portions are of larger diameter than the corresponding outer diameter portions of the shoulder-rod fastener 136, allowing freedom of movement, along, or parallel to the central axis 54 of the airfoil 52. A long axis of elongated apertures formed in the sliding plates 138 also allow relative freedom of movement of the shoulder-rod fastener 136, along or parallel to the central axis 54, but they restrain relative circumferential movement. In this manner, the sliding plate 138, and shoulder-rod fastener 136 interface functions as a thermal expansion joint during engine operation, allowing for differential expansion rates between the airfoil 52 and the ID platform 120 along the central axis 54, but maintaining relative transverse alignment of those structures relative to the central axis. Thus, the expansion joint function of the shoulder-rod fastener 136 and sliding plates 138 interface compensate for more rapid thermal expansion of the respective, metallic, ID 120 and OD 88 platforms growth in the central axis 54 orientation of the vane assembly 50, without compressing the ceramic airfoil 52 that is interposed between and bridges those platforms. Expansion joint maintenance of relative transverse alignment of the airfoil 52 and its ID platform 120 reduces likelihood of transient engine vibration or reduction of the engine’s aerodynamic efficiency during transient heating of the engine.

[0026] The first 128 ID-platform portion defines a first flange portion 142 that is coupled to a mating second flange portion 144 of the second 130 ID-platform portion, by shoulder bolts 106, threaded nuts 108, and washers 110. A CMC material, ceramic ID platform 148 covers the ID platform surface 122, and abuts and/or circumscribes the ceramic airfoil 52. In some embodiments, the ceramic ID platform 148 incorporates an aperture that slidably receives and abuts against the concave 56 and the convex 58 airfoil outer surfaces. In other embodiments, the ceramic ID platform is sandwiched between the ID airfoil tip 64 and the ID platform surface 122. Lips 150 formed in the ceramic ID platform 148 engage with corresponding ID hooks 152 formed in the respective first 128 and second 130 ID platform portions. Clearances between the lips 150 and the hooks 152 are sufficient to accommodate different rates of thermal expansion of the CMC platform 148 and the corresponding metallic platform portions 128, 130. The ceramic ID platform 148 is a replaceable component that provides thermal insulation for the metallic first 128 and second 130 ID platform portions, and all of the aforementioned, metallic fastening hardware that is below the ID platform surface 122. In this way, none of the fastening hardware, including by way of example the shoulder bolts 106, nuts 108, washers 110, shoulder-rod fastener 136, captured sliding plates 138, or nuts 140, is directly exposed to combustion gas.

[0027] In the vane assembly 50 of the embodiment of FIGs. 2-7 provides for internal cooling of the airfoil 52, OD platform 80 and ID platform 120 structures, by providing cooling passages that are in communication with each other. In vane assembly 50 embodiments their cooling passages are compatible with existing engine cooling architecture, wherein coolant fluid (typically compressed air) supplied by the engine enters the OD platform 80, flows through the airfoil 52 and exhausts from the ID platform 120. Specifically, cooling air enters the OD platform cavity 84 in open channels between the first 92 and second 94 clamping jaws and the circumferential surface 78 of the OD tenon 74, and flows through cooling passages 79 formed within the OD airfoil tip 66 of the ceramic airfoil 52. In some embodiments, the cooling passages 79 are mechanically drilled, eroded, or ablated between the ID airfoil tip 64 and the OD airfoil tip 66. Cooling air exits the cooling passages 79 formed in the ID airfoil tip 64 and enters the ID platform cavity 124; between the first 132 and second 134 ID clamping jaws and the circumferential surface 72 of the ID tenon 68. A sealing plate 146 isolates the ID platform cavity 124 from the engine interior, which causes cooling air to exhaust out of the ID platform cooling passages 156.

[0028] FIG. 8 is an alternative embodiment of a split OD platform 170, with first 172 and second 174 platform portions. The first platform portion 172 has a first jaw 176 while the second platform portion has a second jaw 178. The respective jaws 176 and 178 are biased against each other with a jaw fastener 180. In this embodiment, the sliding plates 182 at each end of the jaw fastener provide for thermal expansion along a central axis of the airfoil 52, while restraining relative transverse movement of the airfoil and the OD platform 170 along the central axis, as was previously described for the vane assembly 50 embodiment of FIGs. 2-7. The first platform portion 172 defines a first flange 184 that is fastened to a corresponding second flange 186 of the second platform portion 174 with bolts and nuts 188. While the embodiment of FIG. 8 is an OD platform structure, in other embodiments, a corresponding inner diameter platform is constructed with the same airfoil clamping, thermal expansion, and split- platform structural features and advantages.

[0029] FIG. 9 is a “doublet” vane assembly 200 embodiment, with two circumferentially spaced airfoils 52 retained within a split OD platform comprising a first 202 and second 204 portion. The“doublet” configuration provides for increased torsional stiffness than a comparable single airfoil vane, yet is dimensioned to replace a pair of existing airfoil vane assemblies. The respective OD tenons 74 of the pair of airfoils 52 are clamped and compressed by corresponding, pre-tensioned pairs of first 206 and second 208 clamping jaws and corresponding jaw fasteners 210. In this embodiment, the sliding plates 212 at each end of the pair of jaw fasteners 210 provide for thermal expansion along a central axis of each of the airfoils 52, while restraining relative transverse movement of each airfoil and the assembled OD first 202 and second 204 platform portions along the central axis, as was previously described for the vane assembly 50 embodiment of FIGs. 2-7. Assembly of the unitary first 202 and second 204 platform portions is by mating first 214 and second 216 respective flanges, retained by bolts and nuts 218. While the embodiment of FIG. 9 is an OD platform structure, in other embodiments, a corresponding inner diameter platform is constructed with the same airfoil clamping, thermal expansion, and split- platform structural features and advantages.

[0030] While the vane assembly embodiment 50 pre-tensions corresponding pairs of OD, first 92 and second 94 clamping jaws and/or corresponding pairs of ID, first 132 and second 134 clamping jaws against corresponding circumferential surfaces 78 and 72 of the OD 74 and ID 68 tenons, there are other embodiments of OD and/or ID platforms that pre-tension their respective cavity walls against the corresponding outer circumferential surface of the corresponding tenon that is received within the platform cavity. Other embodiments include the aforementioned vane assemblies 170 and 200.

[0031] In the embodiment of FIG. 10, a unitary OD platform 230 has a cavity 232, which receives the tenon 74 of an airfoil. The cavity 232 is defined by a cavity wall 234, which abuts against the outer circumferential surface 78 of the airfoil tenon 74. One or more shims 236 are driven between the cavity wall 234 and the outer circumferential surface 78 of the airfoil tenon 74, which pre-tensions their respective abutting surfaces against each other, and maintains compression of the tenon transverse the central axis of the airfoil. Pre-tension force is sufficient to maintain tenon compression, and thus vane/platform interface relative alignment, when the vane assembly is at a maximum operating temperature within a combustion turbine engine. In other embodiments, not shown, the OD or ID platform is of unitary construction, with at least one of the first and second clamping jaws of the clamping mechanism biasable toward each other, in order to clamp and pre-tension an outer circumference of a corresponding airfoil tenon there between. [0032] Embodiments of vane assemblies described herein are dimensioned for direct substitution in newly manufactured engines or replacement of vanes in existing service fleets. Embodiments of the composite vanes described herein incorporate existing engine vane-cooling architecture and cooling systems. Composite structure of these vane embodiments, with CMC ceramic airfoils and metallic ID/OD platforms allow higher engine operating temperatures, due to the heat resistant properties of the ceramic materials, while maintaining structural strength advantages of metallic platform and fastener materials (typically constructed of Ni-Co-Fe-Cr-Al “superalloys”, such as INCONEL^® brand alloys). In some embodiments, the metallic platforms are insulated with overlying CMC ceramic platforms, so that no metal in the vane assembly is directly exposed to hot combustion gasses.

[0033] In composite vane assemblies described herein, differing relative rates of thermal expansion of the ceramic airfoil and platform structural elements versus the metallic platforms and related metallic fasteners are accommodated by expansion joints, which allow relative movement of the platforms and the airfoil structures along a central axis of the airfoil, but that restrain relative movements transverse to the central axis. In this way, the vane assembly avoids compression of the airfoil along its central axis, where layers of its CMC matrix rovings are most susceptible to trans- ply separation. The pre-tensioned clamping mechanism of the metallic vane platforms, e.g. biased, opposed clamping jaws of mating first and second platform portions, compresses plies of the CMC matrix rovings about the airfoil tenon’s outer circumferential surface, enhancing strength and structural integrity of the airfoil/platform interface. Clamping pre-tensioning of the platform jaws maintains compression force on the airfoil tenon’s outer circumference, despite relatively greater expansion of the jaws during engine heating, so that relative alignment of the airfoil and the ID/OD platforms is maintained during engine operation. Apertures formed in the CMC airfoil tenons, for receipt of jaw clamping fasteners, are transverse the airfoil central axis, which causes less structural weakening than apertures that are aligned with the airfoil’s central axis. [0034] In some embodiments, both the CMC airfoils and the CMC ceramic platforms are replaceable, allowing for refurbishment of the metallic platform portions. In some applications, split platform embodiments also facilitate easy field replacement of individual CMC airfoils and the CMC platforms, by unfastening the first and second metallic platform portions from each other, swapping out the worn or damaged CMC airfoil and CMC platforms, then re-fastening the metal platform portions. All metallic fastening hardware in the vane assembly is isolated and shielded from the combustion gas pathway by at least the metallic platform surface. Isolation of fastening hardware prevents risk of loose or damaged hardware migration into the combustion gas pathway. In some embodiments, the metallic fastening hardware is also thermally shielded by the covering, replaceable CMC platform.

[0035] Although various embodiments that incorporate the invention have been shown and described in detail herein, others can readily devise many other varied embodiments that still incorporate the claimed invention. The invention is not limited in its application to the exemplary embodiment details of constaiction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms“mounted”,“connected”,“supported”, and“coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further,“connected” and“coupled” are not restricted to physical, mechanical, or electrical connections or couplings.

Claims

CLAIMS What is claimed is:

Claim 1. A vane assembly (50) for a combustion turbine engine (20), comprising:

a ceramic-matrix-composite airfoil (52) having: a radially aligned central axis (54), with opposed concave (56) and convex (58) surfaces that extend along the central axis, and that are conjoined at a leading edge (60) and a trailing edge (62), an inner diameter airfoil tip (64), and an outer diameter airfoil tip (66);

a metallic, inner diameter platform (120) rigidly coupled to the inner diameter airfoil tip, having an ID platform surface (122) facing the airfoil;

a metallic, outer diameter platform (80) rigidly coupled to the outer diameter airfoil tip, having an OD platform surface (82) facing the airfoil;

a tenon (68, 74) integrally formed in the airfoil, projecting outwardly from the inner and/or outer diameter tip thereof, each respective tenon having a distal tenon tip (70, 76) and a tenon circumferential surface (72, 78) between its corresponding distal tenon tip and its corresponding inner or outer diameter airfoil tip; and

a platform cavity (84, 124), defined by a cavity wall (86, 126) formed the inner and/or the outer diameter platform; respectively receiving and circumscribing a corresponding tenon circumferential surface of the airfoil therein; each corresponding cavity wall pre-tensioned about its corresponding tenon circumference to maintain compression of the tenon transverse the central axis of the airfoil when the vane assembly is at a maximum operating temperature within a combustion turbine engine.

Claim 2. The vane assembly of claim 1, further comprising a shim (236) interposed between each cavity wall (234) of the inner and/or outer diameter platform (230) and its corresponding tenon circumferential surface (78), for pre-tensioning the respective cavity wall and maintaining compression of the tenon (74).

Claim 3. The vane assembly of claim 1, further comprising a clamping mechanism coupled to the inner (120) or outer (80) diameter platform behind its respective ID (122) or OD (82) platform surface, for maintaining compression of its corresponding tenon (68, 74), the clamping mechanism having a clamping jaw (92, 94, 132, 134) that forms at least a portion of the corresponding cavity wall (86, 126).

Claim 4. The vane assembly of claim 3, further comprising the clamping mechanism having: a pair of opposed first (92, 132) and second (94, 134) clamping jaws circumscribing the tenon circumferential surface (72, 78); and a threaded, jaw fastener (96, 136) passing through respective apertures formed in the opposed first and second clamping jaws and the tenon; the jaw fastener oriented transverse the central axis (54) of the airfoil (52).

Claim 5. The vane assembly of claim 4, further comprising an expansion joint coupled to the first (92, 132) and second (94, 134) clamping jaws and the tenon (68, 74), for accommodating relative expansion of an inner diameter (120) and/or an outer diameter (80) platform and the airfoil (52) along the radially aligned, central axis (54) during combustion turbine-engine (20) operation.

Claim 6. The vane assembly of claim 5, the expansion joint further comprising apertures formed in the first (92, 132) and second (94, 134) jaws having a larger diameter than outer diameter of a corresponding portion of the jaw fastener (96, 136) that passes therethrough; and first (98) and second (138) sliding plates, receiving the jaw fastener through respective first and second sliding plate apertures, each respective sliding plate abutted against its corresponding, respective first or second clamping jaw; with the respective first and second sliding plates slidable relative to its corresponding first or second clamping jaw along the radially aligned, central axis (54) of the airfoil (52).

Claim 7. The vane assembly of claim 6, the jaw fastener comprising: a shoulder rod (96, 136) having opposite first and second threaded ends respectively passing through the respective first and second clamping jaw apertures and the respective sliding-plate apertures of the first (98), and second (138) sliding plates; and first and second mating nuts (100, 140) engaging the respective first and second threaded ends, and selectively pre-tensioning the first (92, 132) and second (94, 134) jaws, by tightening the first and/or the second mating nuts, to maintain circumferential compression of the respective airfoil tenon (68, 74).

Claim 8. The vane assembly of claim 1, further comprising a split inner diameter platform (120) or a split outer diameter platform (80) respectively having: a first platform portion (88, 128) proximate the leading edge (60) of the airfoil (52) and a second platform portion (90, 130), each of the respective first and second platform portions having co-planar platform surfaces (82, 122) facing the airfoil and in combination forming a clamping mechanism having: a pair of opposed first (92, 132) and second (94, 134) clamping jaws circumscribing the tenon circumferential surface (72, 78), the first jaw formed in the first platform portion and the second jaw formed in the second platform portion; and a threaded, jaw fastener (96, 136) passing through respective apertures formed in the opposed first and second clamping jaws and the tenon; the jaw fastener oriented transverse the central axis (54) of the airfoil.

Claim 9. The vane assembly of claim 8, further comprising the respective first (88, 128) and second (90, 130) platform portions coupled to each other along mating, abutting first (102, 142) and second (104, 144) flanges that project radially away from the respective first (82), and second (122) platform surfaces.

Claim 10. The vane assembly of claim 8, further comprising an expansion joint (98, 138) coupled to the first (92, 132) and second (94, 134) clamping jaws and the tenon (68, 74), for accommodating relative expansion of an inner diameter (120) and/or an outer diameter platform (80) and the airfoil (52) along the radially aligned, central axis (54) during combustion turbine-engine (20) operation.

Claim 11. The vane assembly of claim 10, the expansion joint further comprising apertures formed in the first (92, 132) and second (94, 134) jaws having a larger diameter than outer diameter of a corresponding portion of the jaw fastener (96, 136) that passes therethrough; and first (98) and second (138) sliding plates, receiving the jaw fastener through respective first and second sliding plate apertures, each respective sliding plate abutted against its corresponding, respective first or second clamping jaw; with the respective first and second sliding plates slidable relative to its corresponding first or second clamping jaw along the radially aligned, central axis (54) of the airfoil (52).

Claim 12. The vane assembly of claim 11, the jaw fastener comprising: a shoulder rod (96, 136) having opposite first and second threaded ends respectively passing through the respective first and second clamping jaw apertures and the respective sliding-plate apertures of the first (98), and second (138) sliding plates; and first and second mating nuts (100, 140) engaging the respective first and second threaded ends, and selectively pre-tensioning the first (92, 132) and second (94, 134) jaws, by tightening the first and/or the second mating nuts, to maintain circumferential compression of the respective airfoil tenon (68, 74).

Claim 13. The vane assembly of claim 8, further comprising a ceramic insulation plate (112, 148) coupled to the respective platform surfaces (82, 122) of the respective first (88, 128) and second (90, 130) platform portions, and circumscribing the convex (58) and concave (56) surfaces of the airfoil (52);

the ceramic insulation plate coupled to the respective platform surfaces by hooks (116, 152) formed in the first and second platform portions.

Claim 14. The vane assembly of claim 8, further comprising vane-cooling passages (79, 156) formed in the airfoil (52) and the respective inner (120) and outer (80) platforms, in communication with each other; cooling passages (79) formed in the airfoil passing through the inner (70) and outer (76) diameter tips thereof, and having a cylindrical profile.

Claim 15. The vane assembly of claim 1, further comprising a ceramic insulation plate (112, 148) coupled to the respective platform surfaces (82, 122) of the respective first (88, 128) and second (90, 130) platform portions, and circumscribing the convex (58) and concave (56) surfaces of the airfoil (52);

Claim 16. The vane assembly of claim 1, further comprising vane-cooling passages (79, 156) formed in the airfoil (52) and the respective inner (120) and outer (80) platforms, in communication with each other; cooling passages (79) formed in the airfoil passing through the inner (70) and outer (76) diameter tips thereof, and having a cylindrical profile.