System for mounting a turbine diffuser

Abstract

System comprising: a circumferential overlap connection (42) between a downstream end (104) of an outer wall (106) of a turbine outlet (20) and an upstream end (102) of an outer tube (50) of a diffuser section (38), wherein the circumferential overlap connection (42) is configured to support axial movement of the outer tube (50) relative to the outer wall (106), wherein an upstream lip (96) of the outer tube (50) is arranged radially inside a downstream lip (128) of the outer wall (106), and both the turbine outlet (20) and the diffuser section (38) are configured to receive an exhaust gas (36);a primary flow path (130) extending from the turbine outlet (20) to a diffuser outlet of the diffuser section (38) through an inner region (134), wherein the inner region (134) is located radially inside the outer wall (106) and the outer tube (50), and the diffuser outlet is configured to direct exhaust gas flow to an outlet plenum (60) downstream of the diffuser section (38); a secondary flow path (136) extending from the outlet plenum (60) to the inner region (134) between the downstream lip (128) of the outer wall (106) and the upstream lip (96) of the outer tube (50), wherein the secondary flow path (136) extends through the circumferential overlap connection (42); a cooling channel extending radially outside the outer wall (106) is arranged along the downstream end (104) of the outer wall (106);and a first circumferential seal (92) coupled to the outer wall (106) and arranged at a downstream end of the cooling channel near the circumferential overlap connection (42), wherein the first circumferential seal (92) is configured to isolate the cooling channel from the secondary flow path (136).

Description

BACKGROUNDThe subject matter disclosed herein relates to gas turbines, such as an improved diffuser section.Gas turbine systems generally include a compressor, a combustor, and a turbine. The compressor compresses air from an air inlet and then directs the compressed air to the combustor. The combustor burns a mixture of compressed air and fuel to generate hot combustion gases that are directed to the turbine to perform work to drive, for example, an electric generator.Conventional diffuser sections of the turbine are subjected to high loads due to the structure of the diffuser section and high temperatures associated with the exhaust gases. Accordingly, conventional diffuser sections experience high loads, thereby increasing wear on the diffuser section.US 2014 / 0 026 999 A1 discloses a system with a flange connection between a downstream end of an outer wall of a turbine outlet and an upstream end of an outer tube of a diffuser section, wherein the turbine outlet and the diffuser section are configured to receive an exhaust gas.From JP 2002-161 713 A, DE 42 37 886 A1 and DE 41 09 100 A1 flexible circumferential overlapping connections of flow channels are known in each case, in which a lip of a downstream component is arranged radially in the interior of a sleeve part of an upstream component.US 5 603 605 A discloses a diffuser section of a gas turbine connected to an outer wall of a turbine outlet and having a diffuser shell with an inner tube and an outer tube. A connecting plenum is disposed radially outward of the outer tube and configured to receive a portion of the exhaust gases from the diffuser outlet and re-introduce them into the diffuser passage through injection slots formed in the upstream end portion of the outer tube.BRIEF DESCRIPTIONIn one aspect, a system includes a circumferential lap joint between a downstream end of an outer wall of a turbine outlet and an upstream end of an outer tube of a diffuser portion, the circumferential lap joint assisting axial movement of the outer tube relative to the outer wall. An upstream lip of the outer tube is radially disposed within a downstream lip of the outer wall, and both the turbine outlet and the diffuser portion are configured to receive an exhaust gas. The system further includes a primary flow path extending from the turbine outlet to a diffuser outlet of the diffuser portion through an inner region, the inner region being radially inside the outer wall and the outer tube, and the diffuser outlet being configured to direct an exhaust flow to an outlet plenum downstream of the diffuser portion, and a secondary flow path extending from the outlet plenum to the inner region between the downstream lip of the outer wall and the upstream lip of the outer tube, the secondary flow path extending through the circumferential lap joint. The system further includes a cooling passage disposed radially outward of the outer wall along the downstream end of the outer wall, and a first circumferential seal coupled to the outer wall and disposed at a downstream end of the cooling passage proximate the circumferential lap joint, the first circumferential seal configured to isolate the cooling passage from the secondary flow path.The aforementioned system may include a plurality of discrete brackets coupled to the outer tube and a frame assembly, wherein the plurality of discrete brackets may be configured to axially support the outer tube.Additionally, the plurality of discrete brackets may include a plurality of support brackets, wherein each support bracket of the plurality of support brackets may include a pin extending through a flange of the outer tube, and the pin may be configured to restrict circumferential movement of the outer tube relative to the respective support bracket.Preferably, the plurality of individual holders can be arranged in a rotationally symmetrical arrangement around the outer tube.Any of the aforementioned systems may include a plurality of airfoil elements disposed within the turbine outlet, wherein the circumferential lap joint may be disposed axially a weakening length downstream of the plurality of airfoil elements, and the weakening length may be less than 30.48 cm (12 inches).In some embodiments, any of the aforementioned systems may include an inner circumferential connection between a downstream end of an inner wall of the turbine outlet and an upstream end of an inner pipe of the diffuser portion, wherein the inner circumferential connection may include a plurality of individual inner brackets configured to couple the downstream end of the inner wall to the upstream end of the inner pipe.In addition, the plurality of individual inner brackets may be configured to axially support the inner pipe, and both the inner wall and the inner pipe may be disposed around a support portion of a gas turbine.Any system mentioned above may include a gas turbine engine connected to the turbine outlet, wherein the turbine outlet and the diffuser portion may be configured to receive an exhaust gas from the gas turbine engine during operation of the gas turbine engine.In another aspect, a system includes a turbine outlet including an outer wall and an inner wall, the turbine outlet configured to receive exhaust gas from a gas turbine between the outer wall and the inner wall, a diffuser portion coupled to the turbine outlet, the diffuser portion including an outer tube and an inner tube. The diffuser portion and the turbine outlet are disposed about a turbine axis. The system includes a plurality of discrete outer brackets coupled to the outer tube and a frame assembly, the plurality of discrete outer brackets configured to position the outer tube relative to the outer wall to form a circumferential lap joint between the outer wall of the turbine outlet and the outer tube of the diffuser portion. The plurality of outer individual brackets are circumferentially spaced about the turbine axis, and the plurality of outer individual brackets are configured to axially support the outer tube. A cooling passage is disposed radially outward of a downstream end of the outer wall, and a first circumferential seal is coupled to the outer wall, the first circumferential seal is disposed at a downstream end of the cooling passage and upstream of the circumferential lap joint, and the first circumferential seal is configured to isolate the cooling passage from the exhaust gas.The aforementioned system may include a plurality of individual inner mounts coupled to the inner tube and the inner wall, wherein the plurality of individual inner mounts may be spaced apart from one another along the circumference about the turbine axis, and the plurality of individual inner mounts may be configured to axially support the inner tube.BRIEF DESCRIPTION OF THE DRAWINGSThese and other features, aspects and advantages of the present invention will become more fully understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals represent like parts throughout the drawings, wherein: FIG. 1 is a block diagram of an embodiment of a turbine system including a turbine including a modified diffuser portion; FIG. 2 is a detailed diagram of the diffuser section of the turbine disposed within an exhaust plenum; FIG. 3 shows the modified upper portion of the diffuser; FIG. 4 is a cross-sectional view of the diffuser taken along line 4- 4 of FIG. 2 through the brackets; FIG. 5 is a perspective view of the lap joint and the single bracket taken along line 5--5 of FIG. 4; FIG. 6 is a perspective view of the lap joint and the single bracket taken along line 5--5 of FIG. 4; FIG. 7 is an axial cross-sectional view of the circumferential groove within the rear plate of the diffuser; FIG. 8 is a cross-sectional view of the inner tube rear plate taken along line 8--8 of the diffuser; FIG. 9 describes a method of forming the back plate according to an embodiment of the present disclosure; FIG. 10 is a perspective view of the outer tube of the diffuser portion; FIG. 11 is a perspective view of the inner pipe of the diffuser portion; FIG. 12 illustrates exemplary equipment used in machining the inner tube and the outer tube; and FIG. 13 shows a method for producing the inner tube and the outer tube by means of a pressing process.DETAILED DESCRIPTIONA system and method for improving conventional diffuser sections by using mechanical improvements to the diffuser section are described in detail below. The mechanical improvements to the diffuser section help improve the mechanical integrity of the diffuser by reducing stresses associated with conventional diffuser construction. As discussed in detail below, embodiments of the mechanical improvements include establishing a desired curvature of the diffuser portion, disposing a plurality of rods between a front plate and the rear plate of the diffuser, a circumferential groove disposed in the inner tube to receive the rear plate, a circumferential lap joint of the outer tube, a plurality of discrete brackets disposed along the inner tube and / or the outer tube of the diffuser and configured to couple the diffuser to the turbine outlet, or any combination thereof. The curvature of the diffuser portion is implemented by a machine process such as a press process. The pressing process includes forming a suitable material (e.g., stainless steel, metal) for the inner tube and the outer tube into a desired shape (e.g., curved) by placing the material over a mold. The material is then formed into the desired shape using a roller to press the material into the mold, thereby gradually forming the desired shape. To reduce any residual stresses that occur in the spin rolling process, the inner and outer tubes may be formed from different axial segments (e.g., a first number of axial segments, a second number of axial segments). The use of axial segments to create the inner tube and the outer tube may require less deformation of the material to remove the desired shape of the inner tube and the outer tube, thereby helping to reduce the amount of residual stresses that occur.Once the axial segments (e.g., first number of axial segments, second number of axial segments) of the inner tube and the outer tube are formed, the axial segments of each respective tube may be joined. The axial segments may be cut to ensure that the axial segments (e.g., the first number of axial segments, the second number of axial segments) comprise excess material so that the segments may be matingly connected together. The axial segments may be joined together by welding, brazing, fusion bonding, bolting, fastening, or any combination thereof.The rods are disposed between the inner tube and the outer tube, which in turn are disposed about the turbine axis. The rods serve to connect the downstream end of the rear plate to the downstream end of the front plate via the plurality of rods, and are spaced circumferentially about the turbine axis. In some embodiments, the rods have different rod diameters. The rod diameter depends in part on the circumferential position of the rod layer along the diffuser (e.g., the outer rear plate, the inner rear plate). For example, the diameter of the rods closest to an upper portion of the diffuser (e.g., the outer rear plate, the inner rear plate) may be larger in diameter than the rods closest to a lower portion of the diffuser. In some embodiments, the rod diameters are smaller due to their proximity to the flow of exhaust gases. Thus, smaller rod diameters may be advantageous in that they reduce blockage of the exhaust flow path due to the smaller diameters. The rods disposed within the upper portion of the diffuser portion may be configured to support the load (e.g., weight) of the diffuser portion during installation, for example. For example, the rods disposed within the upper portion of the diffuser portion may be used to raise the diffuser portion. In some embodiments, the rods disposed within the upper portion of the diffuser portion may be connected to a winch, elevator, crane, or other suitable machine hoist to transfer the diffuser portion to a suitable location (e.g., translation for installation, removal, maintenance, repair). The rods can reduce vibration between the inner tube and the outer tube. The arrangement of the rods depends in part on the diameters of the rods. The rods closest to the upper portion of the diffuser have larger diameters to bypass vortex shedding frequencies at which the velocity of the exhaust gases is more uniform.The circumferential groove is disposed at one end of the inner tube. The rear plate may be inserted into the circumferential groove such that the rear plate is connected to portions of the root of the circumferential groove. The circumferential groove may reduce tension by allowing the rear plate to move within the circumferential groove. The circumferential stresses can be reduced in the range by allowing a slight movement between the portions (e.g., the rear plate and the circumferential groove). The stress reduction through the implementation of the circumferential groove may reduce circumferential stresses by around half compared to a diffuser without the circumferential groove.The circumferential lap joint is disposed between the downstream end of the outer wall of the turbine outlet and the upstream end of the outer tube of the diffuser portion. The circumferential lap joint is configured to allow axial movement of the outer tube relative to the outer wall, thereby relieving tension in the outer tube. An upstream lip (e.g., outer lip) of the outer tube may be disposed radially inward of a downstream lip (e.g., lip) of the outer wall to facilitate axial mobility of the lap joint. The tension reduction by using the upstream lip and the downstream lip of the circumferential lap joint can be further increased by using single brackets. The discrete brackets may be coupled to the outer tube and a frame assembly (e.g., an outlet frame). The single brackets (e.g., outer tube single brackets) are configured to support the outer tube in the axial direction. A subset of the discrete mounts (e.g., internal discrete mounts) may be circumferentially disposed around the inner tube of the diffuser. The individual inner brackets (e.g., the support brackets of the inner tube) may hold the diffuser (e.g., the inner tube) in position and reduce movement in the axial direction. The movement of the diffuser (e.g., the inner tube and the outer tube) relative to the turbine outlet may be reduced and / or restricted depending on where the lap joint and the stand-alone brackets are disposed along the outer tube.Referring now to the drawings and first to FIG. 1, a block diagram of one embodiment of a gas turbine system 10 is shown. The diagram includes a fuel nozzle 12, a fuel 14, and a combustor 16. The combustor 16 ignites and burns the air-fuel mixture 34 and then directs pressurized hot exhaust 36 into a turbine 18. The exhaust gas 36 passes turbine buckets of a turbine rotor in the turbine 18, thereby rotationally driving the turbine 18 about the shaft 28. In one embodiment, a modified diffuser 38 is coupled to the turbine 18. The turbine 18 is coupled to a turbine outlet, where the turbine outlet and the diffuser 38 are configured to receive the exhaust gases 36 from the turbine 18 during operation. As described in detail below, embodiments of a turbine system 10 include certain structures and components within the diffuser 38 that improve reliability (e.g., through stress reduction) associated with the manufacture of the diffuser 38. Embodiments of the turbine system 10 may include certain structures and components of the diffuser 38 to improve the manufacturing time of the diffuser 38. The combustion process exhaust 36 may exit the turbine system 10 via the diffuser 38 and the exhaust outlet 20. In some embodiments, the diffuser 38 may include a circumferential groove 40, one or more lap joints 42, one or more discrete brackets 44, one or more rods 46 disposed between a rear plate 62 and a front plate 64 of the diffuser 38, or any combination thereof. The rotating blades of turbine 18 cause rotation of shaft 28 which is coupled to some other components (e.g., compressor 22, load 26) throughout turbine system 10.In one embodiment of turbine system 10, compressor vanes or blades are included as components of compressor 22. The rotor blades within the compressor 22 may be coupled to the shaft 28 by a compressor rotor and rotate when the shaft 28 is driven by the turbine 18. The compressor 22 may suck an oxidant (e.g., air) 30 to the turbine system 10 via an air inlet 24. Further, the shaft 28 may be coupled to the load 26 that is driven via rotation of the shaft 28. As will be appreciated, the load 26 may be any suitable device capable of generating power via the rotary output of the turbine system 10, such as a power generation plant or an external mechanical load. The load 26 may include, for example, an external mechanical load such as an electrical generator. The air inlet 24 draws the oxidant (e.g., air) 30 into the turbine system 10 via a suitable mechanism, such as a cooling air inlet, for subsequent mixing of the air 30 with the fuel 14 via the fuel nozzle 12. The oxidant (e.g., air) 30 received by the turbine system 10 may be fed and compressed to the compressed air 32 by rotation of the blades within the compressor 22. The compressed air 32 may then be fed into one or more fuel nozzles 12. The fuel nozzles 12 may then mix the compressed air 32 and the fuel 14 to produce an air-fuel mixture 34 suitable for combustion.FIG. 2 illustrates a detailed schematic illustration of a portion of the diffuser 38 of the turbine 18. As shown, the diffuser section 38 may include an upper section 52 and a lower section 54, which are illustrated as separated by a vented storage tunnel 56. The vented bearing tunnel 56 may provide cooling flow through the turbine outlet 20 and the diffuser section 38. It can be appreciated that the diffuser 38 has a substantially annular shape that encloses a portion of the storage tunnel 56. The upper portion 52 of the diffuser 38 is coupled to an exhaust frame 58 and is disposed radially inward of an outlet plenum 60. The exhaust gases 36 exit the outlet plenum 60 through the upper and lower portions 52, 54 of the diffuser 38. The rear plate 62 of the diffuser section 38 is also disposed in the plenum 60. The inner tube 48 may be cooler than the outer tube 50, particularly along portions of the inner tube 48 that are farther away from the turbine outlet 20, due in part to the insulation applied to the inner tube 48. Thus, the rear plate 62 can absorb heat more quickly than the inner tube 48, which contributes to a temperature gradient across the diffuser 38. This temperature gradient may cause stresses in the diffuser 38, thereby compromising the mechanical integrity of the diffuser 38.The mechanical integrity of the diffuser 38 may also be affected by stresses associated with the attenuation length of a airfoil member 82 disposed within the diffuser 38 and a vertical connection 74 of the exhaust frame 58. The flow path of the hot exhaust gases 36 may further reduce the mechanical integrity of the diffuser 38 due to the vibrational forces and temperature effects that may deteriorate the diffuser 38. Accordingly, modifications to the area of the diffuser 38, as described in further detail in the description of FIG. 3, may reduce these effects on the diffuser 38. Such modifications may include creating a desired curvature of the portion of the diffuser 38, disposing a plurality of rods 46 between the front plate 64 and the rear plate 62 of the diffuser 38, a circumferential groove 40 disposed in the inner tube 48 to receive the rear plate 62, one or more circumferential lap joints 42, a plurality of discrete brackets 44 disposed along the inner tube 48 and the outer tube 50 of the diffuser 38 and configured to connect the diffuser 38 to the exhaust frame 58, or any combination thereof. The circumferential lap joint 42 and the discrete brackets 44 are configured to reduce motion in certain directions (e.g., circumferential direction 66, axial 76, vertical 78, lateral 80) or facilitate motion (e.g., circumferential direction 66, axial 76, vertical 78, lateral 80, radial 84) depending on how the circumferential lap joints 42 and the discrete brackets 44 are arranged.FIG. 3 shows the modified upper portion 52 of the diffuser 38 according to the present disclosure. The portion of the diffuser 38 may be manufactured such that the diffuser 38 begins to curve along the inner tube 48 and the outer tube 50 of the diffuser 38 at the end closest to the turbine outlet 20. The curvature 88 of the diffuser 38 may provide structural advantages over other diffuser shapes (e.g., more linearly shaped diffusers). For example, the continuous curvature 88 of the diffuser 38 may reduce structural stresses by improving aerodynamic properties of the diffuser 38 as compared to approximating a desired curvature by linear plates. As discussed in detail below, the curvature of the diffuser 38 may be generated by a suitable method, such as a stamping process. In some embodiments, each of the inner tube 48 and the outer tube 50 of the diffuser 38 is formed from more than a single cone. The cone may be an annular blade formed of a suitable material as described with reference to FIG. 11. The inner tube 48 may include, for example, 2, 3 or a plurality of cone portions. The outer tube 50 may include 2, 3, 4, 5, or multiple cone portions. The cone parts may then be subjected to the pressing process such that the desired curvatures of the cone parts are formed. The respective cone portions are then integrally coupled together (e.g., by welding) to form an integral portion of the diffuser 38, as further described with reference to FIG. 11. The cone portions of both the inner tube 48 and the outer tube 50 may be formed by the pressing process. The inner tube 48 and the outer tube 50 may be separate parts that may be coupled together via the rods 46.Further turbine modifications are disposed downstream 104 of the curved portion of the diffuser 38. For example, the plurality of rods 46 may be disposed along the perimeter 66 between the front plate 64 and the rear plate 62 of the diffuser 38. The rods 46 may be coupled to the front plate 64 and the rear plate 62 by a plurality of gusset plates 68 to secure the rods 46 to the front plate 64 and the rear plate 62. The rods 46 are circumferentially 66 disposed between the front plate 64 and the rear plate 62. The rods 46 may serve to reduce the vibration behavior between the front plate 64 and the rear plate 62. The rods 46 may reduce the tendency to unwanted vibration by stiffening the front plate 64 and the rear plate 62, thereby reducing resonance during operation of the gas turbine 18. The rods 46 may have different diameters 70 to accommodate the flow of the exhaust gases 36. For example, the areas in the diffuser outlet closest to the lower end, the inner portion of the diffuser outlet, are equipped with rods 46 having smaller diameters 70 to minimize blockage of the exhaust gases 36.Downstream 104 of the curved portion of the diffuser 38 is further the circumferential groove 40. In some embodiments, the circumferential groove 40 may be disposed on the inner tube 48 to receive the rear plate 62. The circumferential groove 40 may reduce stresses (e.g., circumferential stresses) in the region that may arise due to large temperature changes. As described above, the rear plate 62 is disposed within the outlet plenum 60 such that the rear plate 62 is exposed to approximately the same operating temperatures as the front plate 64. The hub of the inner tube 48 may be insulated such that portions of the inner tube 48 are exposed to cooler operating temperatures than the rear plate 62, resulting in a large temperature gradient across the entire inner tube 48 and the rear plate 62. Thus, the resulting temperature gradient may create stresses in the region due to thermal expansion of the inner tube 48. The circumferential groove 40 may reduce tension by allowing a conical plate 72 of the rear plate 62 to move within the circumferential groove 40. By allowing a slight movement in the radial direction 84 between the regions (e.g., the conical plate 72 and the circumferential groove 40), circumferential stresses can be reduced in the region. As described in detail below, the stress reduction due to the implementation of the circumferential groove 40 may reduce circumferential stresses by around half of the stresses experienced by a conventional diffuser without the circumferential groove 40.The positioning of the lap joint 42 and the discrete brackets 44 may be partially defined by a weakening length 100. The attenuation length 100 is defined in part by a plurality of airfoil members 82 disposed within the turbine outlet 20. The airfoil member 82 is disposed between an outer wall 106 of the turbine outlet 20 and an inner wall 112 of the turbine outlet 20 proximate a downstream 104 end of the turbine outlet 20. A shorter attenuation length 100 from a profile element 82 to the vertical connection 74 may increase stresses in the vertical connection 74, compared to other configurations where the attenuation length 100 may be longer. The attenuation length 100 may help define the location at which the circumferential overlap joint 42 is located. The overlapping joint 42 may be arranged, for example, at a distance approximately equal to the attenuation length 100 downstream of the profile elements 82. In some embodiments, the attenuation length 100 is less than about 30.48 cm (12 inches). The discrete mounts 44 may reduce movement of the diffuser 38 such that movement in the axial 76, vertical 78, and lateral 80 directions is constrained depending on where the discrete mounts 44 are disposed on the diffuser 38. As described in detail below, the discrete brackets 44 disposed along the inner tube 48 and the outer tube 50 may be variously oriented to hold the rear plate 62 and the front plate 64 of the diffuser 38 in place.Returning to the inner tube 48, the upstream end 102 of the inner tube 48 of the portion of the diffuser 38 may be coupled to the downstream end 104 of an inner wall 112 of the turbine outlet 20 via an inner circumferential connection 114. The inner peripheral connection 114 may include the plurality of discrete brackets (e.g., brackets 47). The discrete brackets are configured to connect the downstream end 104 of the inner wall 112 of the turbine outlet 20 to the upstream end 102 of the inner tube 48. The individual inner brackets 47 are configured to axially support the inner tube 48.On the inner tube 48, a secondary flexible seal 101 (e.g., a second peripheral seal) may be disposed in an opening within a secondary flexible seal groove 102. The secondary flexible seal 101 may prevent hot exhaust gases 36 from entering the vented storage tunnel 56. The secondary flexible seal 101 may include one or more plate segments segmented in the circumferential direction to create a 360 degree structure that may be bolted to a first end 103. Similar to the flexible seal 92 of the outer tube 50, the secondary flexible seal 101 may be decoupled from the first end 103 such that the secondary flexible seal 101 may move more freely within the opening of the secondary flexible seal groove 102.FIG. 4 shows a cross-sectional view of the diffuser 38 cut through the brackets 44 along line 4- 4 of FIG. 2. The curvature of the diffuser 38 may begin after (e.g., downstream of) the portion of the diffuser 38 where the lap joint 42 and the discrete brackets 44 are disposed. As described above, the lap joint 42 and the discrete brackets 44 may be disposed along the perimeter 66 around the outer tube 50 of the diffuser 38. The discrete brackets 44 may be coupled to the outer tube 50 and a frame assembly (e.g., the exhaust frame 58). The discrete brackets 44 (e.g., discrete outer brackets 45) are configured to support the outer tube 50 in the axial 76 direction and the circumferential direction 66.Another set of the discrete mounts 44 may be disposed along the perimeter 66 within the inner tube 48 of the diffuser 38. For example, a subset of the individual brackets 44 may include multiple support brackets (e.g., inner individual brackets 47). The inner discrete brackets 47 may provide vertical 78 and / or lateral 80 support for the inner tube 48 with respect to the turbine outlet 20. Both the outer individual holders 45 and the inner individual holders 47 can be arranged in a rotationally symmetrical arrangement around the outer tube 50.The inner tube 48 is exposed to a cooling flow that passes through the vented bearing tunnel 56. The individual inner brackets 47 disposed within the inner tube 48 may be made of materials that maintain their yield strength at lower temperatures (e.g., as compared to a higher temperature of the outer tube 50). The discrete mounts 44 (e.g., the discrete inner mounts 47) may hold the diffuser (e.g., the inner tube 48) in position and reduce movement in the axial direction 76 and / or the lateral direction 80. The inner tube 48 may include a threaded connection at an end 49 to fix portions of the diffuser 38 (e.g., the diffuser rear plate 62 and the diffuser front plate 64) to the turbine outlet 20. The individual brackets 44 and supporting pairs of transferring blocks (see FIG. 6 ) allow thermal expansion in the radial direction 84.The individual brackets 44 may be coupled to the outer tube 50 and the inner tube 48 at various locations. In some embodiments, the discrete mounts 44 may be disposed at a 12 o'clock position 118, a 3 o'clock position 120, a 6 o'clock position 122, a 9 o'clock position 124, or any combination thereof. In some embodiments, the discrete mounts 44 may be disposed at other positions (e.g., 4 o'clock, 7 o'clock) such that the arrangement of the discrete mounts 44 remains separate (e.g., non-continuous). Moreover, the position of the individual brackets 44 may be arranged according to the desired constraint of the outer tube 50 and the inner tube 48. In other words, the plurality of outer individual brackets 45 and the plurality of inner individual brackets 47 may be spaced apart in the circumferential direction 66 about the turbine axis 76. The single outer brackets 45 are configured to position the outer tube 50 relative to the outer wall 106 of the turbine outlet 20 to form the circumferential lap joint 42 between the outer wall 106 of the turbine outlet 20 and the outer tube 50 of the diffuser portion 38. The circumferential lap joint 42 is continuous. The movement of the diffuser 38 (e.g., the inner tube 48 and the outer tube 50) relative to the turbine outlet 20 may be reduced and / or limited depending on where the lap joint 42 and the single bracket 44 are disposed along the outer tube 50. For example, when the individual brackets 44 are disposed at the 3 o'clock position 120 and / or the 9 o'clock position 124, the diffuser 38 (e.g., the inner tube 48 and the outer tube 50) is constrained in the axial direction 76 and the vertical direction 78. When the discrete brackets 44 are disposed at the 12 o'clock position 118 and / or the 6 o'clock position 122, the diffuser 38 (e.g., the inner tube 48 and the outer tube 50) is constrained in the axial direction 76 and the lateral direction 80. The individual brackets 44 may be supported by support components (e.g., a pin) as further described in FIG. 6. The support components may restrict movement in the circumferential direction 66.FIG. 5 shows a perspective view of the lap joint 42 and the discrete bracket 44 taken along line 5- 5 of FIG. 4 As described above, the discrete brackets 44 may be coupled to the outer tube 50 and the frame assembly 58 (e.g., the diffuser frame 116). The discrete brackets 44 are configured to support the outer tube 50 in the axial 76 direction, and at least some of the discrete brackets 44 support the outer tube in the circumferential direction 66.The circumferential lap joint 42 is disposed between the downstream end 104 of the outer wall 106 of the turbine outlet 20 and the upstream end 102 of the outer tube 50 of the portion of the diffuser 38. The circumferential lap joint 42 is configured to allow axial 76 movement of the outer tube 50 relative to the outer wall 106 of the turbine outlet 20, thereby relieving stress in the outer tube 50. An upstream lip (e.g., outer lip 96) of the outer tube 50 is radially 84 disposed within a downstream lip (e.g., lip 128) of the outer wall 106 to facilitate mobility of the lap joint 42. The tension reduction by using the upstream lip and the downstream lip is further increased by using individual brackets 44. The outer individual brackets 45 limit heat transfer from the exhaust frame 58 to the outer tube 50, thus thermal expansion and contraction is likely to occur at fewer locations than a continuous bracket interface, and thermal stress is controlled to occur primarily at the brackets 45. For example, the portion of the diffuser 38 may include the plurality of discrete brackets 44 disposed along the outer tube 50 of the diffuser 38 (e.g., the outer discrete brackets 45) to reduce stress in the vertical joint 74 of the exhaust frame 58.In some embodiments, a flexible seal 92 may be used in the assembly with the lap joint 42 and the single bracket 44. The flexible seal 92 may be disposed proximate the upstream lip 96 of the outer tube 50. The flexible seal 92 may be disposed between the insulation 126 disposed about the single mount 44 and a flexible seal groove 94 of the outer wall 106 of the turbine outlet 20. The flexible seal 92 may include one or more plate segments that are circumferentially segmented to form a 360 degree structure that may be bolted or secured to a first end 93. The flexible seal 92 may remain uncoupled (e.g., unscrewed) from the first end 93, such that the flexible seal 92 may freely move within the flexible seal groove 94 to seal a clearance 95 between the flexible seal 92 and an end opposite the screwed end (e.g., the first end 93 of the flexible seal 92). The flexible seal 92 may resist cooling flow along an outer surface of the turbine outlet 20 (e.g., for gap control) into the diffuser 38. A slot 98 between the outer wall 106 of the turbine outlet 20 and the outer lip 96 of the outer tube 50 may assist some axial 76 movement of the lap joint 42. The lip 96 may be radially 84 connected to the outer lip 128 of the lap joint 42.As described above, the hot exhaust gases 36 flowing through the turbine 18 and the diffuser 38 are received in the outlet plenum 60. The flexible seal 92 may isolate a cooling flow (e.g., in the exhaust frame) from the hot exhaust gases 36 downstream 104 from the flexible seal 92. A primary flow path 130 may extend from the turbine outlet 20 to a diffuser outlet of the portion of the diffuser 38 through an interior region 134 of the diffuser 38. The interior region 134 is located radially 84 within the outer wall 106 and the outer tube 50 between the outer tube 50 and the inner tube 48. A secondary flow path 136 may extend from the outlet plenum 60 to the interior region 134 through the slot 98 between the downstream lip 128 of the outer wall 106 and the upstream lip 96 of the outer tube 50. The secondary flow path 136 may extend through the circumferential lap joint 42. In some embodiments, the secondary flow path 136 may include a non-zero portion of the exhaust flow 36 of the interior region 134.FIG. 6 shows a perspective view of the lap joint 42 and the discrete bracket 44 taken along line 5- 5 of FIG. 4 ; in some embodiments, the discrete brackets 44 may be supported by a pin 86 extending axially 76 through a flange 116 of the outer tube 50, a flange 116, and a pair of transmitting blocks 90. The pin 86 may be disposed through the flange 116 and the transmitting blocks 90 to support the single bracket 44. The pin 86 is configured to allow movement (e.g., by sliding) of the outer tube 50 relative to the respective bracket 44 in the radial direction 84. As described above, the plurality of outer individual brackets 45 include the plurality of circumferential support brackets 44 (e.g., a subset of the plurality of individual brackets). Each support bracket 44 of the plurality of individual outer brackets 45 uses the pin 86 to allow movement of the outer tube 50 relative to the respective support bracket 45 in the radial direction 84. The transmitting blocks 90 and the support bracket 47 restrict movement in the circumferential direction 66.Similar to the outer stand-alone brackets 44, the plurality of inner stand-alone brackets 47 may include a plurality of inner circumferential support brackets, each using a respective pin 86 to extend axially 76 through respective flanges of the inner wall 112 and the inner tube 48. The pins 86 are configured to allow radial 84 movement of the inner tube 48 relative to the respective inner support bracket while restricting circumferential 66 movement.FIG. 7 shows an axial cross-sectional view of the circumferential groove 40 within the inner tube 48 of the diffuser 38 of FIGS. 2 and 3 The rear plate 62 couples to the inner tube 48 of the diffuser 38 at the circumferential groove 40. As described above, the inner tube 48 and the outer tube 50 are disposed about the turbine axis 76. The rear plate 62 is at least partially disposed within the outlet plenum 60 and is disposed downstream 104 of the inner tube 48.The circumferential groove 40 can reduce stresses (e.g. circumferential stresses) in the region, which can arise due to large temperature gradients. The rear plate 62 and the front plate 64 are at least partially disposed within the outlet plenum 60. The hub of the inner tube 48 is insulated such that the hub of the inner tube 48 is exposed to cooler operating temperatures than the rear plate 62, resulting in different temperatures at the rear plate 62 and the hub of the inner tube 48. The difference in temperatures between the rear plate 62 and the hub of the inner tube 48 results in a large temperature gradient across the hub of the inner tube 48 and the rear plate 62. The resulting temperature gradient creates stresses in the region due to thermal expansion / contraction. The circumferential groove 40 may reduce tension by allowing a conical plate 72 of the rear plate 62 to move within the circumferential groove 40. The circumferential stresses can be reduced in the region by allowing a slight movement (i.e., upstream movement, downstream movement) between the regions (e.g., the conical plate 72 and the circumferential groove 40). The stress reduction by the implementation of the circumferential groove 40 may reduce circumferential stresses by around half. The stresses in the region of the rear plate 62 can be reduced from, for example, approximately 413 MPa when the circumferential groove 40 is absent in the inner tube 48 to approximately 207 MPa when the circumferential groove 40 is present in the inner tube 48.A seal interface 140 disposed at a downstream 104 end of the inner tube 48 and the rear plate 62 includes the circumferential groove 40. In some embodiments, the seal interface 140 is mechanically coupled (e.g., welded, fusible-bonded, brazed, bolted, fastened) to the downstream 104 end of the inner tube 48. In some embodiments, the seal interface 140 is formed at the downstream end of the inner tube 48. The seal interface 140 may include a first circumferential groove 142 and a second circumferential groove 144. The first circumferential groove 142 is configured to receive the rear plate 62. Thus, the first circumferential groove 142 opens in a first direction 146 (e.g., downstream 104) away from the turbine axis 76. The second circumferential groove 144 is configured to receive the secondary flexible seal 101. The secondary flexible seal 101 is configured to isolate the outlet plenum 60 from the vented storage tunnel 56. The second circumferential groove 144 opens in a second direction 150 (e.g., upstream) toward the turbine axis 76.The first circumferential groove 142 and the second circumferential groove 144 allow some upstream and downstream movement of the inner tube 48 relative to the rear plate 62, resulting in reduced stresses in the region. In the illustrated embodiment, the rear plate 62 is configured to connect to a root 160 of the first circumferential groove 142 at the 12 o'clock position 118 of the seal interface 140. The seal interface 140 reduces a gap at the 12 o'clock position 118 and provides additional support for the outer tube 50. the seal interface 140 also contributes to stress reduction in the rods 70 by allowing the seal interface of the inner tube 48 to support a portion of the vertical load of the rear plate 62. The rear plate 62 may be offset from the root 160 of the first circumferential groove 142 at the 6 o'clock position 122 (e.g., relative to the 12 o'clock position 118) of the seal interface 140.The rear plate 62 may be constructed from a plurality of circumferential segments 152 (e.g., rear plate segments, the conical plate 72). As described with reference to FIGS. 8 and 9, one or more of the plurality of circumferential segments 152 may include a plurality of stress relief features 154 disposed along a plurality of connections 156 between the circumferential segments 152 of the rear plate 62. In some embodiments, the stress relief features 154 may be concentrated toward an end portion of the circumferential segments 152 (e.g., the rear plate segments) proximate the seal interface 140.FIG. 8 shows a cross-sectional view of the rear plate 62 of the inner tube 48 cut along line 8-8 of the diffuser 38. In the illustrated embodiment, the downstream end 104 of the rear plate 62 is coupled to the downstream end 104 of the front plate 64 via the plurality of rods 46. As described above, the inner tube 48 and the outer tube 50 are disposed about the turbine axis 76. The plurality of rods 46 may thus be spaced apart in the circumferential direction 66 about the turbine axis 76.As described above, the rear plate 62 may be constructed from the plurality of circumferential segments 152 (e.g., the rear plate segments, the conical plate 72). The plurality of circumferential segments 152 may include the plurality of stress relief features 154 disposed along the plurality of joints 156 between the circumferential segments 152 of the rear panel 62. The plurality of strain relief features 154 may be of any suitable shape to achieve strain relief, including circular, heart-shaped, bean-shaped, or any combination thereof.In some embodiments, the rods 46 have different rod diameters 70. The rod diameter 70 is based in part on the position along the perimeter 66 of the location of the rod 46 along the diffuser 38. Accordingly, a plurality of apertures 176 correspond to the plurality of rods 46 disposed within the diffuser 38. The apertures 176 may vary in part depending on the circumferential position 66 of the location of the apertures 176 to connect the outer rear plate 62 and the inner rear plate 63 via the plurality of rods.In the illustrated embodiment, a first set 178 (see FIG. 2 ) of rods 46 disposed at locations along the perimeter 66 within the bottom portion 174 of the portion of the diffuser 38 may have a non-uniform axial cross-section. The first set 178 of rods 46 may have, for example, an oval, elliptical, spherical, or other non-uniform portion of the axial cross-section. The non-uniform portions of the rods 46 may allow the rods 46 to have more resiliency (e.g., in the radial direction 84) than circular rods 46, which may reduce stresses in the lower portion 174. In some embodiments, the rod diameters 70 are smaller to reduce aerodynamic effects on the flow of the exhaust gases 36. Smaller rod diameters 70 may be advantageous in themselves by reducing blockage of the exhaust flow path 36.FIG. 9 describes a method of forming the back panels 62 according to an embodiment of the present disclosure. The rear panel 62 may be formed by a method 190. The method 190 may include inserting (block 192) the plurality of aft plate segments (e.g., the circumferential segments 152, the conical plate 72) in the radial direction 84 toward the turbine axis 76 into the first circumferential groove 142 of the first seal interface 162 on the inner pipe 48 of the portion of the diffuser 38 of the gas turbine 17. The method 190 may include coupling (block 194) the plurality of aft plates 62 to the root 160 of the first seal interface 162 at the 12 o'clock position 118 prior to connecting the aft plates 62. In some embodiments, the 6 o'clock position 122 of the rear plate 62 is offset from (e.g., radially spaced from) the root 160. The method 190 may include joining (block 196) (e.g., welding, fusion bonding, brazing, bolting, securing) the plurality of rear plate segments 62 together. The method 190 may further include inserting the flexible seal 158 into the second circumferential groove 144 of the second seal interface 164 (block 198).Returning now to FIG. 8, the rods 46 disposed within the upper portion 172 of the diffuser 38 may be configured to support the load (e.g., weight) of the diffuser 38. The rods 46 disposed within the upper portion 172 of the diffuser 38 may be used, for example, to raise the diffuser 38. In some embodiments, the rods 46 disposed within the upper portion 172 of the portion of the diffuser 38 may be coupled to a pulley block, winch, crane, or other suitable lifting device to move the assembled diffuser 38 with the rear panels 62 to a suitable location (e.g., to move for installation, removal, maintenance, repair).Each of the plurality of rods 46 includes a rod axis. In some embodiments, the plurality of rods 46 may be substantially parallel to a common rod axis (e.g., turbine axis 76). It should be appreciated that the plurality of rods 46 do not support a plurality of rotating blades. Additionally, in some embodiments, no rotating vanes are disposed in the diffuser 38. The rods are positioned at or near the downstream end of the diffuser 38 to reduce vibration and facilitate installation.FIGS. 10 and 11 show a side view of the inner tube 48 and the outer tube 50 of the diffuser 38. The curvature 88 of the inner tube 48 and the outer tube 50 begins downstream from the turbine region 18. portions of the inner tube 48 and the outer tube 50 are disposed within the outlet plenum 60. FIG. 10 shows a side view of an embodiment of the outer tube 50. the outer tube 50 includes a first number of axial segments 180 disposed downstream of the outer tube 50. In the illustrated embodiment, the outer tube 50 includes two segments (e.g., axial segments). Although two axial segments are shown, it will be appreciated that the outer tube may include three, four or more axial segments. The first number of outer tube segments 180 are connected to each other in the axial direction and form an outer tube interface 188 between all of the outer tube segments 180. As described above, the joining may include welding, brazing, fusion bonding, fastening, or any combination thereof. The first number of outer tube segments 180 include a first continuous curve 182 that curves away from the turbine axis 76 (e.g., from the upstream end of the outer tube 50 toward the outer rear plate 62).FIG. 11 shows a side view of the inner tube 48. in the illustrated embodiment, the inner tube 48 includes four segments (e.g., axial segments). The inner tube 48 includes a second number of axial segments 184 disposed between the upstream end of the inner tube 48 and the seal interface 140. Although four axial segments are shown, it will be appreciated that the inner tube 48 may include three, four, five, six, or more axial segments 184. The second number of axial segments 184 are connected to each other in the axial direction and form an inner pipe interface 208 between all the inner pipe segments 184. As described above, the joining may include welding, brazing, fusion bonding, fastening, or any combination thereof. The second number of axial segments 184 (e.g., the inner tube segments) includes a second continuous curve 186 that curves away from the turbine axis 76 (e.g., from the upstream end of the inner tube 48 to the seal interface 140). As will be appreciated, due to the arrangement of the inner tube 48 and the outer tube 50, the second number of axial segments 184 (e.g., the inner tube 48) is greater than the first number of axial segments of the outer tube 50. the curvature of both the inner tube 48 and the outer tube 50 may be further understood with reference to the description of the pressing process as described in FIG. 12.FIG. 12 illustrates exemplary equipment used in machining the inner tube 48 and the outer tube 50 to the desired continuous curvature as described in FIGS. 10-11. The first and second continuous curvatures 182, 186 (e.g., the outer tube, the inner tube) may be created using a suitable cold working process, such as a swaging process. The pressing process includes forming a suitable material 204 (e.g., stainless steel) for the inner tube 48 and the outer tube 50 into the desired shape by placing the material over a mold 206. The material 204 is then formed into the desired shape using a roller 202 to press the material into the mold, thereby gradually creating the desired shape.The above-described swaging process allows for the desired curvature of the diffuser 38 to provide the required turbine performance (e.g., through reduced stresses). To reduce the residual stresses occurring due to the pressing process, the inner and outer tubes 48, 50 may be formed from a plurality of axial segments (e.g., a plurality of first axial segments 180, a plurality of second axial segments 184). The use of multiple axial segments to create the inner tube 48 and the outer tube 50 may require less deformation of each segment to form the desired shape of the inner tube 48 and the outer tube 50, thereby reducing the amount of residual stresses remaining in the completed diffuser 38.Once the axial segments (e.g., the first number of axial segments 180, the second number of axial segments 184) are formed, the axial segments may be joined together. The axial segments may be cut from a suitable material to ensure that the axial segments (e.g., the first number of axial segments 180, the second number of axial segments 184) comprise excess material so that the segments may be matingly connected together. The axial segments may be joined together by welding, brazing, fusion bonding, bolting, fastening, or any combination thereof.FIG. 13 illustrates a method 300 for forming the inner tube 48 and the outer tube 50 by the pressing process. The pressing process as described herein may use a roller that rotates about an axis of a mold, or the mold may rotate about the axis below the roller. As described above, the method 300 includes forming (block 302) a first number of axial front plate segments of an outer tube 50 by pressing a suitable material onto the mold. As described above, the pressing process for each segment includes forming a suitable material (e.g., stainless steel, metal) to the desired shape by placing the material over a mold. The material is then formed into the desired shape using a roller to press the material into the mold to gradually form the desired shape. The method 300 further includes forming (block 304) a second number of axially rearward plate segments of an inner tube 48 by pressing a suitable material onto a mold. After the axial segments are formed, the method 300 includes joining (block 306) the first number of axial front plate segments together to form the outer tube 50, and joining (block 308) the second number of axial rear plate segments together to form the inner tube 48. Both the inner tube 48 and the outer tube 50 are coupled to the gas turbine 18. As described above with reference to FIG. 7, a circumferential groove may be machined into the inner tube 48.Technical effects of the invention include improving conventional diffusers by using mechanical improvements on the diffuser section. The mechanical improvements to the diffuser help improve the mechanical integrity of the diffuser by reducing stresses associated with conventional diffuser design. Embodiments of the mechanical improvements include establishing a desired curvature of the diffuser, disposing a plurality of rods between a front plate and the rear plate of the diffuser, a circumferential groove disposed in the inner tube to receive the rear plate, a circumferential lap joint, a plurality of individual brackets disposed along the inner tube and the outer tube of the diffuser, configured to couple the diffuser to the turbine outlet, or any combination thereof.This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such further examples are intended to be included within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.A system includes a circumferential lap joint between a downstream end, an outer wall of a turbine outlet, and an upstream end of an outer tube of a diffuser portion, the circumferential lap joint assisting axial movement of the outer tube relative to the outer wall, an upstream lip of the outer tube being disposed radially inward of a downstream lip of the outer wall, and both the turbine outlet and the diffuser portion being configured to receive an exhaust gas.

Claims

A system comprising: a circumferential lap joint (42) between a downstream end (104) of an outer wall (106) of a turbine outlet (20) and an upstream end (102) of an outer tube (50) of a diffuser portion (38), the circumferential lap joint (42) configured to assist axial movement of the outer tube (50) relative to the outer wall (106), wherein an upstream lip (96) of the outer tube (50) is radially disposed within a downstream lip (128) of the outer wall (106), and both the turbine outlet (20) and the diffuser portion (38) are configured to receive an exhaust gas (36); a primary flow path (130) extending from the turbine outlet (20) to a diffuser outlet of the diffuser portion (38) through an inner region (134), the inner region (134) being radially inside the outer wall (106) and the outer tube (50), the diffuser outlet configured to direct an exhaust flow to an outlet plenum (60) downstream of the diffuser portion (38); a secondary flow path (136) extending from the outlet plenum (60) to the inner region (134) between the downstream lip (128) of the outer wall (106) and the upstream lip (96) of the outer tube (50), the secondary flow path (136) extending through the circumferential lap joint (42); a cooling passage disposed radially outward of the outer wall (106) along the downstream end (104) of the outer wall (106); and a first circumferential seal (92) coupled to the outer wall (106) and disposed at a downstream end of the cooling passage proximate the circumferential lap joint (42), the first circumferential seal (92) configured to isolate the cooling passage from the secondary flow path (136).The system of claim 1, comprising a plurality of discrete brackets (44) coupled to the outer tube (50) and a frame assembly (58), the plurality of discrete brackets (44) configured to axially support the outer tube (50).The system of claim 2, wherein the plurality of discrete brackets (44) includes a plurality of support brackets (45), each support bracket (45) of the plurality of support brackets (45) including a pin (86) extending axially through a flange (116) of the outer tube (50), and the pin (86) configured to restrict circumferential movement of the outer tube (50) relative to the respective support bracket (45); preferably wherein the plurality of discrete brackets (44) are arranged in a rotationally symmetric arrangement about the outer tube (50).The system of any preceding claim, comprising a plurality of airfoil members (82) disposed within the turbine outlet (20), wherein the circumferential lap joint (42) is disposed axially on a weakening length (100) downstream of the plurality of airfoil members (82), and the weakening length (100) is less than 30.48 cm.The system of any preceding claim, comprising an inner circumferential connection (114) between a downstream end (104) of an inner wall (112) of the turbine outlet (20) and an upstream end (102) of an inner pipe (48) of the diffuser section (38), the inner circumferential connection (114) comprising a plurality of individual inner mounts (47) configured to couple the downstream end (104) of the inner wall (112) to the upstream end (102) of the inner pipe (48); preferably wherein the plurality of individual inner mounts (47) are configured to axially support the inner pipe (48), and preferably wherein both the inner wall (112) and the inner pipe (48) are disposed about a support section of a gas turbine.The system of any preceding claim, comprising a gas turbine connected to the turbine outlet, wherein the turbine outlet and the diffuser portion are configured to receive an exhaust gas from the gas turbine during operation of the gas turbine.A system comprising: a turbine outlet (20) having an outer wall (106) and an inner wall (112), wherein the turbine outlet (20) is configured to receive an exhaust gas (36) from a gas turbine between the outer wall (106) and the inner wall (112); a diffuser portion (38) coupled to the turbine outlet (20), wherein the diffuser portion (38) comprises an outer tube (50) and an inner tube (48), and wherein the diffuser portion (38) and the turbine outlet (20) are disposed about a turbine axis; a plurality of single outer brackets (45) coupled to the outer tube (50) and a frame assembly (58), the plurality of single outer brackets (45) configured to position the outer tube (50) relative to the outer wall (106) to form a circumferential lap joint (42) between the outer wall (106) of the turbine outlet (20) and the outer tube (50) of the diffuser portion (38), the plurality of single outer brackets (45) spaced circumferentially about the turbine axis, and the plurality of single outer brackets (45) configured to axially support the outer tube (50); a cooling passage disposed radially outward of a downstream end (104) of the outer wall (106); and a first peripheral seal (92) coupled to the outer wall (106), the first peripheral seal (92) being disposed at a downstream end of the cooling passage and upstream of the peripheral lap joint (42), and the first peripheral seal (92) being configured to isolate the cooling passage from the exhaust gas (36).The system of claim 7, comprising: a plurality of individual inner brackets (47) coupled to the inner tube (48) and the inner wall (112), the plurality of individual inner brackets (47) being circumferentially spaced about the turbine axis, and the plurality of individual inner brackets (47) being configured to axially support the inner tube (48).

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