Patent Application
20160097303
Embodiments of the invention relate to shrouds for a gas turbine engines. More particularly, but not by way of limitation, present embodiments relate to ceramic matrix composite shroud support systems utilized in gas turbine engines.
A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is located at a forward end of the engine. Moving toward the aft end, in order, the intake is followed by a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the engine, such as, for example, low-pressure and high-pressure compressors, and low-pressure and high-pressure turbines. This, however, is not an exhaustive list. An engine also typically has an internal shaft axially disposed along a center longitudinal axis of the engine. The internal shaft is connected to both the turbine and the air compressor, such that the turbine provides a rotational input to the air compressor to drive the compressor blades.
In operation, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine first receives the hot combustion gases from the combustor and includes a stator nozzle assembly directing the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a supporting rotor disk. In a two stage turbine, a second stage stator nozzle assembly is positioned downstream of the first stage blades followed in turn by a row of second stage rotor blades extending radially outwardly from a second supporting rotor disk. The turbine converts the combustion gas energy to mechanical energy.
Each of the turbines may include one or more stages of rotor blades which extend radially outward from rotor discs. A shroud assembly circumscribes the turbine rotor and defines an outer boundary for combustion gases flowing through the turbine. The turbine shroud may be a single unitary structure or may be formed of a plurality of segments. Some known shroud assemblies include a shroud hanger that is coupled to an outer casing of the engine to provide support to a plurality of shrouds positioned adjacent to, and radially outward of, the tips of the turbine blades. The shrouds may be coupled by way of a single bolted connection to the shroud hanger. However, should a crack or bolt failure occur, the shroud may become disconnected from the shroud hanger.
The shroud must be capable of meeting the design life requirements for use in the turbine engine operating temperature and pressure environment. To enable current materials to operate effectively in such strenuous temperature and pressure conditions, it has been practiced to utilize composite and, in particular, ceramic matrix composite (CMC) materials for use in the shroud segments because they have higher temperature capability than metallic type parts. However, such ceramic matrix composite (CMC) materials have mechanical properties that must be considered during the design and application of the CMC use as a shroud segment or component. CMC materials have relatively low tensile ductility or low strain to failure when compared to metallic materials. Also, CMC materials have a coefficient of thermal expansion which differs significantly from metal alloys used as restraining supports or hangers for shrouds of CMC type materials. Therefore, if a CMC shroud segment is restrained and cooled on one surface during operation, stress concentrations can develop leading to failure of the segment.
As may be seen by the foregoing, it would be desirable to overcome these and other deficiencies with gas turbine engine components. Moreover, it would be desirable to improve the reliability of a CMC shroud support system.
According to embodiments of the invention, a shroud support system with load spreading comprises a shroud hanger which extends in at least a circumferential direction, the shroud hanger having a first wall and a second wall spaced apart in an axial direction by a retainer support wall, a ceramic matrix composite shroud disposed in the shroud hanger between the first and second walls and the retainer support wall, a retainer having circumferentially spaced first and second bolt holes, the retainer passing through the shroud, and first and second bolts passing through the shroud hanger and engaging the first and second bolt holes of the retainer. In another embodiment of the shroud support system, the shroud hanger has first and second bolt holes, the first and second bolt holes being spaced circumferentially. In another embodiment of the shroud support system, the first and second bolt holes of the shroud hanger extending one of parallel or at an angle relative to each other through the shroud hanger. In another embodiment, the shroud support system further comprises plural bosses depending from the retainer support wall. In another embodiment, the shroud support system further comprises a shroud hanger bolt hole in each boss. In another embodiment of the shroud support system, the shroud is disposed between first and second bosses. In another embodiment, the shroud support system further comprises air diffuser cavity holes in the shroud hanger. In another embodiment of the shroud support system, one of the first and second walls function as a spring. In another embodiment of the shroud support system, the retainer has a plurality of protrusions to engage the shroud. In another embodiment, the shroud support system further comprises a baffle disposed below the retainer and within the shroud hanger.
All of the above outlined features are to be understood as exemplary only and many more features and objectives of the embodiments of the present invention may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith.
The above-mentioned and other features and advantages of these exemplary embodiments, and the manner of attaining them, will become more apparent and the shroud support system will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein:
Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus, it is intended that the embodiments of the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
As used herein, the terms “axial” or “axially” refer to a dimension along a longitudinal axis of an engine. The term “forward” used in conjunction with “axial” or “axially” refers to moving in a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term “aft” used in conjunction with “axial” or “axially” refers to moving in a direction toward the engine nozzle, or a component being relatively closer to the engine nozzle as compared to another component.
As used herein, the terms “radial” or “radially” refer to a dimension extending between a center longitudinal axis of the engine and an outer engine circumference. The use of the terms “proximal” or “proximally,” either by themselves or in conjunction with the terms “radial” or “radially,” refers to moving in a direction toward the center longitudinal axis, or a component being relatively closer to the center longitudinal axis as compared to another component. The use of the terms “distal” or “distally,” either by themselves or in conjunction with the terms “radial” or “radially,” refers to moving in a direction toward the outer engine circumference, or a component being relatively closer to the outer engine circumference as compared to another component.
As used herein, the terms “lateral” or “laterally” refer to a dimension that is perpendicular to both the axial and radial dimensions.
All directional references (e.g., radial, axial, proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are only used for identification purposes to aid the reader's understanding of the embodiments of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the embodiments of the present invention. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto may vary.
Referring initially to
In operation, air enters through the air inlet end 12 of the engine 10 and moves through at least one stage of compression where the air pressure is increased and directed to the combustor 16. The compressed air is mixed with fuel and burned providing the hot combustion gas which exits the combustor 16 toward the high pressure turbine 20. At the high pressure turbine 20, energy is extracted from the hot combustion gas causing rotation of turbine blades which in turn cause rotation of the shaft 24. The shaft 24 passes toward the front of the engine to continue rotation of the one or more compressor stages 14, a turbofan 18 or inlet fan blades, depending on the turbine design. The turbofan 18 is connected by the shaft 28 to a low pressure turbine 21 and creates thrust for the turbine engine 10. The low pressure turbine 21 may also be utilized to extract further energy and power additional compressor stages. The low pressure air may be used to aid in cooling components of the engine as well.
Referring now to
The system 30 includes a hanger 70, a shroud 40 comprised of a plurality of shroud segments 41 and a retainer 80. A baffle 90 may optionally be used within the shroud segment 41 and beneath the retainer 80. The system 30 includes a shroud hanger 70 which is connected to an engine casing 35 and extends circumferentially about a portion of the engine, for example the turbine. The engine casing 35 extends circumferentially about the engine axis 26 (
The shroud hanger 70 is defined by a plurality of segments which in combination, extend about the central axis 26 of the engine. The shroud hanger 70 includes a first wall 72 a second wall 74, each of which extend in a radial direction and in a circumferential direction. A hanger gusset 76 extends between the first wall 72 and the second wall 74 and may extend axially or may extend at an angle to the central axis 26 as depicted. According to instant embodiment, the gusset 76 is tapered from a lower radial height at the first wall 72 to a higher radial height at the second wall 74. The shroud hanger 70 includes tabs or hooks 73, 75 which may be utilized to engage the engine casing. The gusset 76 may alternatively be flat or tapered in the opposite direction. These hooks 73, 75 may take various forms in order to provide a mounting assembly or structure.
As depicted, the shroud hanger 70 has a space between the first wall 72 and the second wall 74 wherein the shroud segment 41 may be positioned. The lower most surface of the shroud segment 41 defines an outer surface of an air flow path within the gas turbine engine, for example a compressor or turbine. The segments 41 may further comprise an abradable material 43 on the lowermost surface. Radially inward from the shroud segment is an airfoil blade 23 which rotates during operation of the gas turbine engine 10 with a rotor disk.
A bolt 79 is positioned within the shroud hanger 70 and extends downwardly through a hanger boss 77. The bolt 79 is connected to the retainer 80 which extends in a circumferential direction through the shroud segment 41. The retainer 80 captures the shroud segment 41 within the shroud hanger 70 inhibiting the segment 41 from being removed from the shroud hanger 70. Each shroud hanger 70 includes two bosses 77 which are spaced apart circumferentially and are disposed near circumferential ends of the shroud segment 41. With the retainer 80 extending through the shroud segment 41, the shroud segment 41 is captured between the first and second walls 72, 74 and within the open space of the shroud hanger 70. Beneath the retainer 80 is a baffle 90 which aids with cooling of the shroud segments 41.
Referring now to
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Adjacent to the bolt holes 71 are air diffuser cavities 89. These holes provide shroud cooling air from a known source through the retainer baffle 90.
The second wall 74 of the shroud hanger 70 functions as a spring structure. When the shroud segment 41 (
Referring now to
The radially inner wall 42 extends beyond the forward wall 46 and aft wall 48 to define forward and aft overhangs 54, 56. When a plurality of shroud segments 40 are positioned together, a substantially continuous flow surface 60 is defined along the radially inner side of wall 42. This is best seen in a forward looking aft view of
The shroud segments 41 include end faces 68 which are commonly referred to as “slash faces.” The slash faces 68 may lie in plane parallel to the center line axis of the engine 10, referred to as a “radial plane”, or they may be slightly offset from the radial plane, or otherwise oriented so that they are at an acute angle to such radial plane. Along the slash faces 68 are relief sections 62, 64, which in combination with adjacent relief sections of adjacent segments 41 form apertures. When a plurality of segments 41 are positioned to form a shroud or shroud assembly 40, the shroud 40 has a plurality of circumferentially spaced apertures formed by adjacent relief sections 62, 64 located at the slash faces 68. The shroud 40 is supported from the hanger 70 and retainer 80 at these locations.
When the segments 41 are assembled into a complete ring, end gaps may be present between the faces 68 at the adjacent shroud segments 41. One or more seals may be provided at the end faces 68. These seals are generally known as “spline” seals formed of thin strips of metal or other suitable materials which are inserted in slots in the end faces to span the gaps between adjacent segments 41.
The shroud segments 41 may be constructed of various low ductility and low coefficient of thermal expansion materials including but not limited to a ceramic matrix composite (CMC). Generally, CMC materials include a ceramic fiber, for example a silicon carbide (SiC), forms of which are coated with a compliant material such as boron nitride (BN). The fibers are coated in a ceramic type matrix, one form of which is silicon carbide (SiC). In an embodiment, the shroud segment 41 can also be constructed of other low-ductility, high-temperature-capable materials. CMC materials generally have room temperature tensile ductility of less than or equal to about 1% which is used herein to define a low tensile ductility material. Generally, CMC materials have a room temperature tensile ductility in the range of about 0.4% to about 0.7%.
CMC materials have a characteristic wherein the materials tensile strength in the direction parallel to the length of the fibers (the “fiber direction”) is stronger than the tensile strength in the direction perpendicular. This perpendicular direction may include matrix, interlaminar, secondary or tertiary fiber directions. Various physical properties may also differ between the fiber and the matrix directions.
The shroud segment 41 may incorporate a layer of environmental barrier coating 43, which may be an abradable material, and/or a rub-tolerant material of a known type suitable for use with CMC materials. This layer is sometimes referred to as a “rub coat” 43. As used herein, the term “abradable” implies that the rub coat 43 is capable of being abraded, ground, or eroded away during contact with the tips of the turbine blades 23 as they turn inside the shroud segments 41 at high speed, with little or no resulting damage to the turbine blade tips. This abradable property may be a result of the material composition of the rub coat 43, by its physical configuration or by some combination thereof. The rub coat 43 may comprise a ceramic layer such as yttria stabilized zirconia or barium strontium aluminosilicate. Exemplary compositions and methods suitable for making the rub 43 are described in U.S. Pat. No. 7,749,565 (Johnson, et al.), which is incorporated herein by reference.
Referring now to
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The foregoing description of structures and methods has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the structures and methods to the precise forms and/or steps disclosed, and obviously many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. It is understood that while certain forms of composite structures have been illustrated and described, it is not limited thereto and instead will only be limited by the claims, appended hereto.
While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.
This application is a national stage application under 35 U.S.C. §371(c) of prior filed, co-pending PCT application serial number PCT/US2014/035089, filed on Apr. 23, 2014, which claims priority to U.S. Patent Application Ser. No. 61/824,491, titled “CMC Shroud Support System” filed May 17, 2013. The above-listed applications are herein incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US14/35089 | 4/23/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61824491 | May 2013 | US |
