RHOMBOID BODY FOR A GAS TURBINE ENGINE

BACKGROUND

[0003] The present invention relates generally to the field of turbomachinery, and, more particularly, to ring seals as may be used in a turbine section of a turbomachine, such as a gas turbine engine, and, even more particularly, to ring seals such as may be formed by a ceramic-based rhomboid body.

[0004] 2 Description of the Related Art

[0005] A gas turbine engine typically has a compressor section, a combustion section having a num ber of combustors, and a turbine section. Ambient air is compressed in the compressor section and conveyed to the combustors in the combustion section. The combustors combine the compressed air with a fuel and ignite the mixture creating combustion products. The combustion products flow in a turbulent manner and at a high velocity. The combustion products are routed to the turbine section via transition ducts. Within the turbine section are rows of vane assemblies. Rotating blade assemblies are coupled to a turbine rotor. As the combustion product expands through the turbine section, the combustion product causes the blade assemblies and turbine rotor to rotate. The turbine rotor may be linked to an electric generator and used to generate electricity.

[0005] Within the gas turbine engine located between the rows of vanes there

generally are ring seals, such as may be made up of a plurality of ring seal segments. These ring seal segments are exposed to severe pressure boundaries and extreme temperatures. The severe pressure boundaries may create relatively large loads that the ring seals mus handle. Therefore, ring seals used in gas turbine engines should be designed to handle these environmental conditions. For one example of ring seals used in a gas turbine engine, see International Patent Application number: PCT/US2018/033594.

1000 1 BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a fragmentary cross-sectional view of a gas turbine engine.

[0008] FIG. 2 is an isometric view of a disclosed ring seal segment, such as may be formed with a ceramic-based rhomboid body, as may be supported by an interfit structure defined by a casing of the gas turbine engine.

[0009] FIG 3 is an axial section view of the disclosed ring seal segment.

[0010] FIG. 4 is a circumferential view of adjoining ring seal segments forming a ship lap joint in the circumferential direction.

[0011] FIG. 5 is an isometric view i llustrating certain non-limiting structural details of the disclosed ring seal segment.

DETAILED DESCRIPTION

[0012] Disclosed embodiments are directed to ring seals, such as may be formed by a closed ceramic-based rhomboid body, and may be used in a combustion turbine engine (e.g., a gas turbine engine). Without limitation, disclosed embodiments are effective to reliably and cost-effectively make use of CMC and other high-temperature materials, such as MAX phase materials, in the high pressure, high environment of the gas turbine engine. Disclosed embodiments are designed to accommodate thermal growl h differences that may develop between the body of the ring seal and a metal casing on which the ring seal is disposed, as well as take advantage of the stiffness gain of the enclosed shape, and finally the redundant isolation of various regions of the assembly in terms of temperature exposure. 3] In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. Ho wever, those skilled in the art will understand that disclosed embodiments may be practiced without these specific details that the aspects of the present invention are not limited to the disclosed embodiments, and that aspects of the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would he well- understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.

[0014] Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase“in one embodiment/’ does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art. depending on the needs of a given application.

100151 FIG. 1 show's a gas turbine engine 10 including a compressor section 12, a combustor section 14 and a turbine section 16. Working gases flow _' from combustor section 14 toward turbine section 16 where there are alternating rows of stationary' vanes 18 and rotating blades 20. Each row' of rotating blades 20 is formed by a plurality of rotating blades 20 attached to a disc 22 secured on a rotor 24. The illustrated rotating blades 20 extend radially outward from the discs 22 and terminate in a region known as a blade tip 26. Each row of stationary vanes 18 is formed by attaching a plurality of stationary vanes 18 to a vane carrier 28. The illustrated stationary vanes 18 extend radially inward from the inner peripheral surface 30 of the vane carrier 28 The vane carrier 28 is attached to an outer casing 32, w _' hich encloses the turbine section 16 of the engine 10. [0016] Between the rows of stationary vanes 18, a disclosed ring seal assembly

34 may be disposed. As will be appreciated by those skilled in the an, ring seal assembly 34 is a stationary component that functions as a hot gas path guide between the rows of vanes 18 at the locations of the rotating blades 20. Ring seal assembly 84 may be formed by a plurality of ring segments 50 described in greater detail below. Each ring segment 50 extends over a respective are segment and the plurality of ring segments is circumferentially interconnected to form ring seal assembly 34 During engine operation, high temperature, high velocity gases flow through the rows of vanes 18 and blades 20 in the turbine section 16. Ring seal assembly 34 is exposed to this flow of high temperature gases as well.

[0017 Certain prior art ring seal assemblies have been made from metallic

superalloys that often involve active cooling systems and thermal barrier coatings so that the ring seal assembly can withstand the extreme temperatures to which it is exposed. As an alternative, some prior an ring seal assemblies may involve ceramic matrix composite (CMC) materials, which have higher temperature capabilities than metal alloys. By utilizing such CMC materials, cooling air can be reduced, which has a positive impact on engine

performance, emissions control and operating economics.

[0018] However, despite favorable thermal properties of CMC material components, the CMC material components present certain challenges. For example, CMC material components may have an allowable stress, which may be

approximately an order of magnitude lower than when the component is formed from a metal alloy. Additionally, the CMC material components may have a relatively high degree of stiffness, and a substantially lower thermal expansion rate than metallic components, which, for example, can lead to suboptima! load distribution at transfer points. [0019] In view of the foregoing challenges, CMC material components cannot merely be substituted for equivalent metal alloy components of identical geometric structures and be subjected to the same pressure loading without potentially exceeding the allowable stresses of the CMC material. Disclosed embodiments of a ring seal involve structures and mounting techniques, which allow for cost-effective and reliable use of CMC and other high-temperature materials, such as MAX phase materials, in the high pressure, high temperature environment encountered by ring seals in gas turbine applications.

[0020] FIG. 2 is an isometric view of a disclosed ring seal segment 50 as may be

supported by an interfit structure 52, such as a groove-and-tongue interfit structure, defined by easing 32 of gas turbine engine 10. In one non-limiting embodiment, ring seal segment 50 may comprise a ceramic-based rhomboid body 54 (e.g., forming a dosed body along its cross-section) defining a cavity 56 withi ceramic-based rhomboid bodv 54.

[0021] In this embodiment, a metal compression plate 58 may be disposed in cavity 56 against an inward surface 59 of a side 64 of ceramic-based rhomboid body 54 radially spaced apart and opposite to a hot side 66 of the ring seal assembly. That is, subject to a higher temperature than side 64 of ceramic-based rhomboid body 54. Metal compression plate 58 may be arranged to apply radially-outward compression against inward surface 59 of side 64 of ceramic- based rhomboid body 54 opposite to hot side 66 of the ring seal assembly.

This structural arrangement avoids the possibility of structural buckling of ceramic-based rhomboid body 54 in the presence of a high-pressure load. Also the location of metal compression plate 58 away from hot side 66 of the ring seal assembly is desirable for improving thermo-mechanical performance of the ring assembly. For example, if metal compression plate 58 was located at the hot side 66 of the ring seal assembly, this would likely involve a higher consumption of cooling air. [0022] Cerarnie-based rhomboid body 54 of disclosed ring seal segment 50, without limitation, may comprise a CMC material. In certain alternative non-limiting embodiments, ceramic-based rhomboid body 54 may comprise a ternary ceramic, referred to in the art as a MAX phase. For readers desirous of background information in connection with the foregoing ternary ceramic, reference is made to article authored by M. Radovic and M. W. Barsoum, titled‘"MAX phases: Bridging the gap between metals and ceramics”, American Ceramic Society Bulletin, Vol. 92, Nr. 3, p. 20-27 (April 2013), which is incorporated herein by reference.

[0023] A biasing assembly 70 (FIG. 3), such comprising one or more leaf springs, may be disposed outside cavity 56 against an outward surface 72 of the side 64 of the rhomboid body opposite to the hot side 66 of the ring seal assembly. Biasing assembly 70 may be arranged to apply a pre-load biasing force to metal compression plate 58. FIG. 3 illustrates a bolt 74 having opposite ends that may connected to a radial!y-outer nut 76i supported on casing 32 and a ra ially-inner nut 76 _? supported against compression plate 58. By way of example, radial I y-outer nut 76i may be appropriately torqued to compress biasing assembly 70 and apply a desired pre-load biasing force to metal compression plate 58, which in turn would apply a desired radially-outward compression against inward surface 59 of side 64 of ceramic-based rhomboid body 54 opposite to hot side 66 of the ring seal assembly.

[0024] FIG. 4 is a circumferential view of adjoining ring seal segments 501, 50 _?. forming a ship lap joint 80, which, depending on the needs of a given application, may be arranged to improve sealing performance between circumferentially adjacent pairs of arcuate ring seal segments. FIG. 5 is an isometric view illustrating certain non-limiting structural details of the disclosed ring seal segment. In one non-limiting embodiment, ceramic- based rhomboid body 54 may comprise a fiber alignment extending along the periphery of the rhomboid body, as may be appreciated in the fragmentary cutaway portion shown in the figure. That is, the reinforcement fibers may extend transverse to the arc segment spanned by the ceramic-based rhomboid body. It will be appreciated that the fiber alignment in alternative

embodiments, depending on the needs of a given application, may comprise two-dimensional or three-dimensional woven and/or unwoven layers of reinforcing fibers, (or combinations of such arrangements of reinforcing fibers) to provide a desired performance in a given application.

[0026] From the foregoing disclosure, it should be appreciated that disclosed

embodiments provided ring seals, such as may be formed by a ceramic-based rhomboid body. Without limitation, disclosed embodiments are effective to reliably and cost-effectively make use of CMC and other high-temperature materials, such as MAX phase materials, in the high pressure, high

environment of the gas turbine engine. Disclosed embodiments are designed to accommodate thermal growth differences that may develop between the body of the ring seal and a metal casing on which the body of the ring seal is disposed.

[0027] While embodiments of the present disclosure have been disclosed in

exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the scope of the invention and its equivalents, as set forth in the following claims.