WO2018102047A1

WO2018102047A1 - Compact gas turbine exhaust system

Info

Publication number: WO2018102047A1
Application number: PCT/US2017/057822
Authority: WO
Inventors: William C. Maier
Original assignee: Dresser-Rand Company
Priority date: 2016-11-30
Filing date: 2017-10-23
Publication date: 2018-06-07

Abstract

An exhaust system (102) for a gas turbine (100) may include a housing (120a-c), a first diffuser section (110), a second diffuser section (112), and a plurality of turning vanes (138). The first diffuser section (110) may include an annular exhaust system inlet (130). The second diffuser section (112) may be fluidly coupled to the first diffuser section (110) and may include an exhaust system outlet (136) and a longitudinal axis (114) disposed perpendicular to a longitudinal axis (116) of the first diffuser section (110). An exhaust flow passage (134a-c) may extend through the housing (120a-c) from the annular exhaust system inlet (130) to the exhaust system outlet (136). The plurality of turning vanes (138) may be disposed in a cascading arrangement and extend into the exhaust flow passage (134c) from the housing (120a-c).

Description

Compact Gas Turbine Exhaust System

Background

[0001] Gas turbines are commonly used to drive generators for power generation and/or to drive process equipment such as compressors or pumps. To drive the process equipment and/or the generators, gas turbines may receive and compress motive gas in a compressor, combust the compressed motive gas with fuel in a combustor, and expand the combusted motive gas through a power turbine. The exhaust from the gas turbine may be directed through an exhaust system to diffuse and, in some cases, turn the motive gas after exiting the power turbine of the gas turbine.

[0002] Typically, there is a great emphasis on limiting the spatial footprint of gas turbines, especially when installed in an offshore environment, such as on an offshore rig or marine vessel. As the exhaust system has a significant impact on the overall size of the gas turbine, there is a continuing effort to reduce the overall dimensions of the exhaust system without unduly penalizing gas turbine performance via a lack of pressure recovery or excessive total pressure loss. Accordingly, conventional approaches have provided exhaust systems having compact dimensions with respect to axial extents, vertical extents, or horizontal extents; however, such approaches have resulted in the reduction of at least one extent at the sake of other extent(s). For example, one conventional exhaust system combining axial and radial diffuser sections provides a reduced axial extent but undesirable vertical and horizontal extents. Other examples of conventional exhaust systems provide a reduced horizontal extent but undesirable axial and vertical extents to limit excessive flow turning losses.

[0003] What is needed, then, is a compact exhaust system for a gas turbine having a compact exhaust shape in all dimensions with little or no compromise with respect to gas turbine performance.

Summary

[0004] Embodiments of the disclosure may provide an exhaust system for a gas turbine. The exhaust system may include an axially extending portion defining an exhaust system inlet. The axially extending portion may include an outer wall and an inner wall disposed radially inward from the outer wall and defining a first portion of an exhaust flow passage therebetween. The exhaust system may also include a vertically extending portion fluidly coupled with and disposed downstream from the axially extending portion. The vertically extending portion may define an exhaust system outlet and include an outer wall defining a second portion of the exhaust flow passage and a portion of a rotary component opening extending vertically along a portion of a vertical extent of the vertically extending portion. The exhaust system may further include a vane section including an outer wall having an inner surface and a plurality of vanes extending radially inward from the inner surface into a third portion of the exhaust flow passage defined by the inner surface. A cross section of the first portion of the flow passage, a cross section of the second portion of the flow passage, and a cross section of the third portion of the flow passage may differ from one another in at least shape.

[0005] Embodiments of the disclosure may further provide an exhaust system for a gas turbine. The exhaust system may include a housing, a first diffuser section, and a second diffuser section. The first diffuser section may include a longitudinal axis, an outer wall forming a first portion of the housing, and an annular exhaust system inlet defined in part by the outer wall of the first diffuser section. The second diffuser section may be fluidly coupled to the first diffuser section and may include a longitudinal axis disposed perpendicular to the longitudinal axis of the first diffuser section, an outer wall forming a second portion of the housing, and an exhaust system outlet defined by the outer wall of the second diffuser section. The exhaust system may also include a plurality of turning vanes extending radially inward from the housing. The plurality of turning vanes may be disposed in a cascading arrangement. An exhaust flow passage may be defined at least in part by the outer walls of the first diffuser section and the second diffuser section and may extend from the annular exhaust system inlet to the exhaust system outlet.

[0006] Embodiments of the disclosure may further provide a gas turbine. The gas turbine may include a compressor configured to fluidly couple with a motive gas source and to compress a motive gas received from the motive gas source. The gas turbine may also include a combustor fluidly coupled to the compressor and a fuel source, the combustor configured to combust a compressed motive gas with fuel received from the fuel source. The gas turbine may further include a power turbine having a longitudinal axis and configured to expand a combusted motive gas and generate mechanical power. The gas turbine may also include an exhaust system fluidly coupled with the power turbine and configured to receive an expanded motive gas. The exhaust system may include a housing, a first diffuser section, and a second diffuser section. The first diffuser section may include a longitudinal axis coaxial with the longitudinal axis of the power turbine, an outer wall forming a first portion of the housing, and an annular exhaust system inlet defined in part by the outer wall of the first diffuser section and fluidly coupled to a power turbine outlet of the power turbine. The second diffuser section may be fluidly coupled to the first diffuser section and may include a longitudinal axis disposed substantially perpendicular to the longitudinal axis of the first diffuser section, an outer wall forming a second portion of the housing, and an exhaust system outlet defined by the outer wall of the second diffuser section. The exhaust system may also include a plurality of turning vanes extending radially inward from the housing. The plurality of turning vanes may be disposed in a cascading arrangement. An exhaust flow passage may be defined at least in part by the outer walls of the first diffuser section and the second diffuser section and may extend from the annular exhaust system inlet to the exhaust system outlet.

Brief Description of the Drawings

[0007] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0008] Figure 1 illustrates a rear perspective view of a gas turbine including an exhaust system, according to one or more embodiments of the disclosure. [0009] Figure 2A illustrates a top view of a portion of the gas turbine of Figure 1 , where the portion includes a power turbine and the exhaust system, according to one or more embodiments of the disclosure.

[0010] Figure 2B illustrates a cross-sectional view of the portion of the gas turbine including the power turbine and the exhaust system taken along line 2B of Figure 2A, according to one or more embodiments of the disclosure.

[0011] Figure 2C illustrates an enlarged view of the portion of the exhaust system indicated by the box labeled 2C of Figure 2B, according to one or more embodiments of the disclosure.

[0012] Figure 3 illustrates a transparent perspective view of a portion of the exhaust system detailing cross sections of an exhaust flow passage at various locations thereof within the exhaust system, according to one or more embodiments of the disclosure.

[0013] Figure 4 is a graph depicting a meridional cross section area of the exhaust flow passage area at the various locations indicated in Figure 3 as a percentage of an area of the gas turbine at the exhaust system inlet, according to one or more embodiments of the disclosure.

Detailed Description

[0014] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0015] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0016] Figure 1 illustrates a rear perspective view of a gas turbine 100 including an exhaust system 102, according to one or more embodiments of the disclosure. The gas turbine 100 may be configured for land-based operations, such as a refinery or liquefied natural gas (LNG) plant; however, the gas turbine 100 is not limited thereto and may be configured for marine or offshore operations including, for example, drilling rigs, drilling vessels, FPSO units, and production platforms. The gas turbine 100 may be configured to drive a generator (not shown) for power generation and/or to drive other process equipment (not shown), such as compressors or pumps. To drive the process equipment and/or the generators, the gas turbine 100 may receive and compress motive gas in a compressor 104, combust the compressed motive gas with fuel in a combustor 106, and expand the combusted motive gas through a power turbine 108. The expansion of the combusted motive gas in the power turbine 108 generates mechanical power, which may be translated via a drive shaft 109, or common shaft in some embodiments, to drive the process equipment and/or the generators. In an exemplary embodiment, the motive gas may be or include air provided from an air source (not shown), such as the atmosphere surrounding the gas turbine 100. In another embodiment, the motive gas may be or include air provided from another air source, such as a tank or cylinder of compressed or non-compressed air. Generally, all references to "upstream" and "downstream" are associated with the primary flow direction of the motive gas, unless specified otherwise.

[0017] As illustrated, the exhaust system 102 may be coupled directly, or in other embodiments coupled indirectly, to the power turbine 108. The coupling of the exhaust system 102 and the power turbine 108 may permit fluid communication therebetween, such that the expanded motive gas discharged by the power turbine 108 is fed to and received by the exhaust system 102. As will be discussed in further detail below, the exhaust system 102 may be configured to receive the expanded motive gas from the power turbine 108, diffuse and turn the expanded motive gas, and to discharge the expanded motive gas without negatively impacting the performance of the gas turbine 100 in terms of pressure loss, while retaining a compact configuration in terms of axial, vertical, and horizontal extents. As used herein, the terms "axial", "vertical", and "horizontal" are defined in terms of the axes illustrated in Figure 1 . Namely, the term "axial" references the x-axis, the term "vertical" references the y-axis, and the term "horizontal" references the z-axis as illustrated in Figure 1 .

[0018] Referring now to Figures 2A and 2B with continued reference to Figure 1 , Figures 2A and 2B illustrate respective top and cross-sectional views of a portion of the gas turbine 100 of Figure 1 , where the portion includes the power turbine 108 and the exhaust system 102, according to one or more embodiments of the disclosure. In an exemplary embodiment, the exhaust system 102 may include an axially extending diffuser section, referred to herein as an axial diffuser section 1 10, and a vertically extending diffuser section, referred to herein as a vertical diffuser section 1 12, fluidly coupled to and disposed downstream from the axial diffuser section 1 10. As most clearly seen in Figure 2B, as oriented the axial diffuser section 1 10 may have a longitudinal axis 1 14 extending along an axial extent thereof, and the vertical diffuser section 1 12 may have a longitudinal axis 1 16 extending along a vertical extent thereof. In an exemplary embodiment, the longitudinal axis 1 14 of the axial diffuser section 1 10 may be coaxial with a longitudinal axis 1 18 of the power turbine 108.

[0019] The axial diffuser section 1 10 may have an outer wall 120a forming part of a diffuser housing 120a-c and spaced radially outward from an inner wall 122 of the axial diffuser section 1 10. The inner wall 122 of the axial diffuser section 1 10 may include an annular portion 124 and a tapered portion 126 and may define an internal passage 128 through which the drive shaft 109 and associated bearings of the power turbine 108 may extend or be housed. As arranged, the outer wall 120a and inner wall 122 of the axial diffuser section 1 10 may define an exhaust system inlet 130 directly or indirectly coupled to the power turbine 108 and fluidly coupled to a power turbine outlet 132 via any means known in the art. For example, the exhaust system inlet 130 may be directly coupled to the power turbine 108 via one or more fasteners (not shown). Exemplary fasteners include, but are not limited to, bolts, clamps, or the like. The outer wall 120a and inner wall 122 of the axial diffuser section 1 10 may further define a portion 134a of a flow passage 134a-c through which the expanded motive gas flows within the exhaust system 102 after entering the exhaust system inlet 130. In an exemplary embodiment, the portion 134a of the flow passage 134a-c defined by the axial diffuser section 1 10 may be generally annular at the exhaust system inlet 130.

[0020] The vertical diffuser section 1 12 may have an outer wall 120b forming another part of the diffuser housing 120a-c and defining an exhaust system outlet 136 at end of the vertical extent of the vertical diffuser section 1 12. The exhaust system outlet 136 may form a generally rectangular shape. In an exemplary embodiment, one or more corners of the generally rectangular exhaust system outlet 136 may be curved or rounded. The outer wall 120b of the vertical diffuser section 1 12 may further define another portion 134b of the flow passage 134a-c through which the expanded motive gas flows within the exhaust system 102 after entering the exhaust system inlet 130. Accordingly, the portion 134b of the flow passage 134a-c defined by the vertical diffuser section 1 12 may fluidly communicate with the portion 134a of the flow passage 134a-c defined by the axial diffuser section 1 10 such that the expanded motive gas entering the exhaust system inlet 130 may flow through the exhaust system 102 and may be discharged from the exhaust system 102 via the exhaust system outlet 136.

[0021] Referring now to Figure 2C with continued reference to Figures 1 , 2A, and 2B, Figure 2C illustrates an enlarged view of the portion of the exhaust system 102 indicated by the box labeled 2C of Figure 2B, according to one or more embodiments of the disclosure. The exhaust system 102 may further include a plurality of vanes 138 disposed in a portion 134c of the flow passage 134a-c fluidly coupling the other portions 134a, 134b of the flow passage 134a-c. The plurality of vanes 138 may be configured to condition the expanded motive gas flowing therethrough. In an embodiment, the plurality of vanes 138 may be disposed in the portion 134c of the flow passage 134a-c to condition the motive gas to achieve predetermined or desired fluid properties and/or fluid flow attributes. For example, the plurality of vanes 138 may be configured to control or regulate the velocity, flow rate, pressure, and/or any other suitable fluid properties and/or fluid flow attributes of the expanded motive gas flowing through the flow passage 134a-c. In another example, the plurality of vanes 138 may be configured to minimize or reduce pressure losses and/or maintain uniform or substantially uniform flow distribution of the expanded motive gas through the flow passage 134a-c.

[0022] As most clearly illustrated in Figures 1 and 2B, the plurality of vanes 138 may be arranged in a cascading configuration in the exhaust system 102 at a junction of the axial diffuser section 1 10 and the vertical diffuser section 1 12. The junction may be disposed at an elbow 140, or bend, of the exhaust system 102. In an embodiment, the exhaust system 102 may include a vane section 142 disposed between and coupled to the axial diffuser section 1 10 and the vertical diffuser section 1 12. The vane section 142 may have an outer wall 120c and an inner surface 143 thereof defining the portion 134c of the flow passage 134a-c through which the expanded motive gas flows within the exhaust system 102 after entering the exhaust system inlet 130. The plurality of vanes 138 may extend radially inward into the portion 134c of the flow passage 134a-c defined by the inner surface 143 of the vane section 142. The vane section 142 may be disposed at the elbow 140, or bend, of the exhaust system 102. Accordingly, the plurality of vanes 138 may be disposed in the elbow 140 of the exhaust system 102 and may be configured to at least partially turn the expanded motive gas flowing generally axially in the axial diffuser section 1 10 toward the vertical diffuser section 1 12, such that the expanded motive gas flows more vertically. In another embodiment, the plurality of vanes 138 may extend radially inward from the outer wall 120a of the axial diffuser section 1 10, the outer wall 120b of the vertical diffuser section 1 12, or both, into the flow passage 134a-c.

[0023] As discussed, the plurality of vanes 138 may be configured to at least partially condition the expanded motive gas flowing through the flow passage 134a-c. For example, the plurality of vanes 138 may be airfoil shaped, streamline shaped, or shaped otherwise to at least partially condition the expanded motive gas flowing through the flow passage 134a-c. In an exemplary embodiment, the plurality of vanes 138 are airfoil shaped. For example, the airfoil shapes of the plurality of vanes 138 may be based on or substantially similar to the inverse design airfoil shape as arranged and disclosed in the NASA Technical Paper 2570, published April 1 , 1986, the contents of which are incorporated herein by reference. As further illustrated in Figure 2C, respective mean camber lines 144 of the plurality of vanes 138 may be arcuate or curved to facilitate the turning of the expanded motive gas toward the exhaust system outlet 136 of the exhaust system 102. While Figure 2C illustrates the plurality of vanes 138 as having arcuate mean camber lines 144, it should be appreciated that the respective camber lines 144 may also be straight. In at least one embodiment, a chord length and/or a pitch to chord ratio of each of the vanes 138 may be varied (i.e. , increased or decreased) to control or regulate the pressure flow through the flow passage 134a-c.

[0024] In at least one embodiment, an orientation and/or arrangement of the plurality of vanes 138 may also be varied and/or controlled to at least partially condition the expanded motive gas flowing through the flow passage 134a-c. For example, the plurality of vanes 138 may be tilted, pitched, cambered, or otherwise angled relative to the longitudinal axis 1 16 of the vertical diffuser section 1 12 or a component thereof. For example, as illustrated in Figure 2C, the plurality of vanes 138 may be angled relative to the longitudinal axis 1 16 of the vertical diffuser section 1 12 to turn the expanded motive gas toward the exhaust system outlet 136 of the exhaust system 102. As illustrated in Figures 2B and 2C, the plurality of vanes 138 may be aligned with one another in a single, cascading row. In another embodiment, the plurality of vanes 138 may be arranged as a plurality of rows, where the vanes 138 in one of the rows may be staggered or offset with respect to the vanes 138 in an adjacent row. In yet another embodiment, the plurality of vanes 138 may be arranged as a plurality of rows, where the vanes 138 in one of the rows may be aligned with the vanes 138 in an adjacent row. The plurality of vanes 138 may be spaced from one another at substantially equal intervals or at varying intervals.

[0025] Referring now to Figure 3 with continued reference to Figures 1 and 2A-2C, Figure 3 illustrates a perspective view of a portion of the exhaust system 102 detailing cross sections of the flow passage 134a-c at various locations thereof within the exhaust system 102, according to one or more embodiments of the disclosure. The portion of the exhaust system 102 illustrated in Figure 3 is symmetric about vertical plane 146, also shown in Figure 1 , which extends along the vertical extent of the exhaust system 102. Accordingly, those of ordinary skill in the art will appreciate that the portion of the exhaust system 102 on the opposing side of the vertical plane 146 may mirror the portion of the exhaust system 102 illustrated in Figure 3.

[0026] As discussed, respective portions 134b and 134a of the flow passage 134a-c may be defined by the outer wall 120b of the vertical diffuser section 1 12 and the inner wall 122 and the outer wall 120a of the axial diffuser section 1 10. In some embodiments, the flow passage 134a-c may further be defined by the outer wall 120c of the vane section 142. The flow passage 134a-c may extend from the exhaust system inlet 130 to the exhaust system outlet 136 and may turn, or bend at the elbow 140 of the exhaust system 102, at which the plurality of vanes 138 may extend radially inward into the flow passage 134a-c. A cross section of the flow passage 134a-c may be taken at any location along a length thereof, and in an exemplary embodiment, one or more cross sections taken at respective locations along the length of the flow passage 134a-c may differ in shape and/or size from a cross section taken at a location adjacent the exhaust system inlet 130 or the exhaust system outlet 136. In an exemplary embodiment, a respective outer perimeter of one or more cross sections taken at respective locations along the length of the flow passage 134a-c may differ from an outer perimeter of a cross section taken at a location adjacent the exhaust system inlet 130 or the exhaust system outlet 136.

[0027] Accordingly, the shape or contour of the flow passage 134a-c extending from the exhaust system inlet 130 to the exhaust system outlet 136 may best be described with reference to the example cross sections taken at the locations indicated in Figure 3. At location 300, a cross section 302 of the flow passage 134a-c is taken adjacent the exhaust system inlet 130, whereby the cross section 302 of the flow passage 134a-c is defined by the inner wall 122 and the outer wall 120a of the axial diffuser section 1 10. At location 300, an outer contour 304 of the cross section 302 defined by the outer wall 120a is substantially circular, or arc-shaped, and an inner contour 306 of the cross section defined by the inner wall 122 is substantially circular, or arc-shaped, and concentric with the outer contour 304. Thus, the cross section 302 of the flow passage 134a-c at location 300 is substantially annular in shape and substantially similar in dimension to an exit annulus (not shown) of the power turbine 108.

[0028] The flow passage 134a-c may extend from the cross section 302 of the flow passage 134a-c taken at location 300 along the axial extent of the axial diffuser section 1 10. As the flow passage 134a-c extends along the axial extent of the axial diffuser section 1 10, the inner wall 122 tapers along the tapered portion 126 thereof such that a cross section of the internal passage 128 defined by the inner wall 122 is correspondingly reduced. In addition, a bottom portion 148 of the outer wall 120a opposing the exhaust system outlet 136 tapers along the axial extent of the axial diffuser section 1 10. At location 310 downstream from location 300 and substantially midway between the exhaust system inlet 130 and the elbow 140 of the exhaust system 102, another cross section 312 of the flow passage 134a-c is taken, whereby the inner wall 122 and the bottom portion 148 of the outer wall 120a of the axial diffuser section 1 10 have tapered along the axial extent of the axial diffuser section 1 10. An inner contour 314 of the cross section 312 at location 310 defined by the inner wall 122 has a reduced curvature due to the tapering of the inner wall 122 as compared to the inner contour 306 of the cross section 302 at location 300. Accordingly, the inner contour 314 is oblong at location 310. Corresponding, an outer contour 316 of the cross section 310 defined by the outer wall 120a has a reduced curvature due to the tapering of the bottom portion 302 at location 300. Accordingly, the outer contour 316 is oblong at location 310.

[0029] The flow passage 134a-c may extend from the cross section 312 of the flow passage 134a-c taken at location 310 along the axial extent of the axial diffuser section 1 10. As the flow passage 134a-c extends along the axial extent of the axial diffuser section 1 10, the inner wall 122 further tapers at the tapered portion 126 thereof and terminates at or within a rotary component opening 150 (see Figure 1 ) defined in part by the bottom portion 148 of the outer wall 120a at the end of the axial extent of the axial diffuser section 1 10. The rotary component opening 150 may be configured to provide proper clearance for the drive shaft 109 and associated bearings of the power turbine 108. The rotary component opening 150 may be further defined in part by the outer wall 120c of the vane section 142 fluidly coupled to the axial diffuser section 1 10.

[0030] At location 320 downstream from location 310 and substantially at the vane section 142 located at the elbow 140 of the exhaust system 102, another cross section 322 of the flow passage 134a-c is taken, whereby the outer wall 120c of the vane section 142 defines an inner contour 324a, 324b and an outer contour 326a, 326b of the cross section 322 at location 320. The inner contour 324a, 324b of the cross section 322 is defined by the portion of the outer wall 120c of the vane section 142 defining the rotary component opening 150 and has a further reduced curvature as compared to the inner contour 314 of the cross section 312 at location 310, and in an exemplary embodiment, includes two substantially planar portions 324a, 324b horizontally offset from one another. The outer contour 326a, 326b of the cross section 322 defined by the outer wall 120c of the vane section 142 includes a substantially planar portion 326a and an arcuate portion 326b. In an exemplary embodiment, the contour of the exhaust flow passage 134a-c transition from the cross section 302 at location 300 to the cross section 322 at location 320 is straight line faired between these sections producing simple wall shapes composed of various portions with only two dimensional curvature.

[0031] At location 320, the plurality of vanes 138 may be disposed in a cascading arrangement. The cascading vanes 138 may be configured to turn the expanded motive gas from an axially flowing direction to a vertically flowing direction and toward the exhaust system outlet 136 defined by the vertical diffuser section 1 12. The flow passage 134a-c may extend from the cross section 322 of the flow passage 134a-c at location 320 along the vertical extent of the vertical diffuser section 1 12. As the flow passage 134a-c extends along the vertical extent of the axial diffuser section 1 10, the outer wall 120b of the vertical diffuser section 1 12 further defines a portion of the rotary component opening 150 (see Figure 1 ). As the flow passage 134a-c extends along the vertical extent of the vertical diffuser section 1 12, the portion of the outer wall 120b of the vertical diffuser section 1 12 defining a portion of the rotary component opening 150 tapers radially inward.

[0032] At location 330 downstream from location 320 and substantially midway between the elbow 140 of the exhaust system 102 and the exhaust system outlet 136, another cross section 332 of the flow passage 134a-c is taken. An inner contour 334a, 334b of the cross section 332 at location 330 defined by the portion of the outer wall 120b of the vertical diffuser section 1 12 defining the rotary component opening 150 includes two substantially planar portions 334a, 334b having a reduced horizontal offset from one another as compared to inner contour 324a, 324b of cross section 320 at location 320 the due to the tapering of the outer wall 120b of the vertical diffuser section 1 12 radially inward.

[0033] The flow passage 134a-c may extend from the cross section 332 of the flow passage 134a-c at location 330 along the vertical extent of the vertical diffuser section 1 12. As the flow passage 134a-c extends along the vertical extent of the axial diffuser section 1 10, the outer wall 120b of the vertical diffuser section 1 12 defining a portion of the rotary component opening 150 tapers further. At location 340 downstream from location 330 and substantially midway between the location 330 and the exhaust system outlet 136, another cross section 342 of the flow passage 134a-c is taken, whereby an inner contour 344a, 344b of the cross section 342 at location 340 defined by the portion of the outer wall 120b of the vertical diffuser section 1 12 defining the rotary component opening 150 includes two substantially planar portions 344a, 344b having a further reduced horizontal offset from one another due to the further tapering of the outer wall 120b of the vertical diffuser section 1 12 as compared to the inner contour 334a, 334b of the cross section 332 at location 330. The flow passage 134a-c transition from the cross section 322 at location 320 to the cross section 342 at location 340 is straight line faired between these sections producing simple wall shapes composed of various portions with only two dimensional curvature.

[0034] The flow passage 134a-c may extend from the cross section 342 of the flow passage 134a-c at location 340 along the vertical extent of the vertical diffuser section 1 12. As the flow passage 134a-c extends along the vertical extent of the vertical diffuser section 1 12, the rotary component opening 150 defined by the outer wall 120b of the vertical diffuser section 1 12 terminates, such that the flow passage 134a-c is substantially similar in shape and size to the exhaust system outlet 136. At location 350 downstream from the location 340 and substantially adjacent the exhaust system outlet 136, another cross section 352 of the flow passage 134a-c is taken, whereby the inner contour 354 of the cross section 352 is substantially planar such that the cross section 352 is substantially rectangular in shape.

[0035] Figure 4 is a graph depicting a meridional cross section area of the area of the exhaust flow passage 134a-c at the various locations 300, 310, 320, 330, 340, 350 indicated in Figure 3 as a percentage of an area of the gas turbine 100 at the exhaust system inlet 130, according to one or more embodiments of the disclosure. The meridional cross sectional area of the exhaust flow passage 134a-c is monotonically increased in a roughly linear manner through the exhaust flow passage 134a-c as shown in the graph of Figure 4. A reasonable trade-off between successful static pressure recovery and minimum total pressure loss is achieved with the approximate 80% increase in area.

[0036] According to one embodiment, all or part of the housing 120a-c formed from the outer walls 120a, 120b, and 120c (as well as other members) may be cast as a single unit. One or more of the above components (or their subcomponents) may be made from stainless steel and/or durable, high temperature materials known as "superalloys"; however, other types of materials are fully contemplated herein. A superalloy, or high- performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys may include, but are not limited to, materials such as HASTELLOY, INCONEL, WASPALOY, RENE alloys, HAYNES alloys, INCOLOY, MP98T, TMS alloys, and CMSX single crystal alloys. [0037] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

Claims I claim:

1. An exhaust system for a gas turbine, comprising:

an axially extending portion defining an exhaust system inlet, the axially extending portion comprising an outer wall and an inner wall disposed radially inward from the outer wall and defining a first portion of an exhaust flow passage therebetween; a vertically extending portion fluidly coupled with and disposed downstream from the axially extending portion, the vertically extending portion defining an exhaust system outlet and comprising an outer wall defining a second portion of the exhaust flow passage and a portion of a rotary component opening extending vertically along a portion of a vertical extent of the vertically extending portion; and

a vane section comprising an outer wall having an inner surface and a plurality of vanes extending radially inward from the inner surface into a third portion of the exhaust flow passage defined by the inner surface,

wherein a cross section of the first portion of the flow passage, a cross section of the second portion of the flow passage, and a cross section of the third portion of the flow passage differ from one another in at least shape.

2. The exhaust system of claim 1 , wherein the plurality of vanes are configured to turn a flow of expanded motive gas flowing axially into the exhaust system inlet to a flow of expanded motive gas flowing vertically from the exhaust system outlet.

3. The exhaust system of claim 2, wherein the plurality of vanes are disposed in a cascading arrangement within the third portion of the exhaust flow passage defined by the inner surface of the outer wall of the vane section.

4. The exhaust system of claim 1 , wherein the inner wall of the axially extending portion comprises an annular portion and a tapered portion, such that the inner wall tapers as the first portion of the flow passage extends from the exhaust system inlet to the vane section.

5. The exhaust system of claim 1 , wherein the cross section of the first portion of the flow passage is substantially annular and is adjacent the exhaust system inlet.

6. The exhaust system of claim 1 , wherein the cross section of the second portion of the flow passage is substantially rectangular and is adjacent the exhaust system outlet.

7. The exhaust system of claim 1 , wherein the cross section of the third portion of the flow passage comprises an arcuate section and a planar section and is adjacent a plurality of vanes configured to turn a flow of expanded motive gas flowing axially into the exhaust system inlet to a flow of expanded motive gas flowing vertically from the exhaust system outlet.

8. The exhaust system of claim 1 , wherein:

the cross section of the first portion of the flow passage is substantially annular and is adjacent the exhaust system inlet;

the cross section of the second portion of the flow passage is substantially rectangular and is adjacent the exhaust system outlet; and

the cross section of the third portion of the flow passage comprises an arcuate section and a planar section and is adjacent a plurality of vanes configured to turn a flow of expanded motive gas flowing axially into the exhaust system inlet to a flow of expanded motive gas flowing vertically from the exhaust system outlet.

9. The exhaust system of claim 1 , wherein the outer wall of the vertically extending portion defining a portion of the rotary component opening tapers radially inward such that the rotary component opening terminates at a location along the vertical extent of the vertically extending portion.

10. The exhaust system of claim 9, wherein the rotary component opening is configured to provide clearance for a drive shaft of the gas turbine.

1 1. An exhaust system for a gas turbine, comprising:

a housing; a first diffuser section comprising

a longitudinal axis;

an outer wall forming a first portion of the housing; and

an annular exhaust system inlet defined in part by the outer wall of the first diffuser section;

a second diffuser section fluidly coupled to the first diffuser section and comprising

a longitudinal axis disposed perpendicular to the longitudinal axis of the first diffuser section;

an outer wall forming a second portion of the housing; and

an exhaust system outlet defined by the outer wall of the second diffuser section;

a plurality of turning vanes extending radially inward from the housing, the plurality of turning vanes disposed in a cascading arrangement,

wherein an exhaust flow passage is defined at least in part by the outer walls of the first diffuser section and the second diffuser section and extends from the annular exhaust system inlet to the exhaust system outlet.

12. The exhaust system of claim 1 1 , further comprising an elbow section fluidly coupling the first diffuser section and the second diffuser section, the elbow section defining a portion of the exhaust flow passage and comprising an outer wall forming a third portion of the housing, the plurality of turning vanes extending radially inward from the outer wall of the elbow section and into the exhaust flow passage.

13. The exhaust system of claim 12, wherein the plurality of turning vanes are configured to turn an expanded motive gas flowing through the first diffuser section in a first direction to flow in a second direction through the second diffuser section, the second direction approximately oriented ninety degrees from the first direction.

14. The exhaust system of claim 1 1 , wherein:

a cross section of the exhaust flow passage at the exhaust system outlet is substantially rectangular in shape; and a cross section of the exhaust flow passage at a location in the first diffuser section substantially midway between the annular exhaust system inlet and the elbow section is substantially oblong in shape.

15. The exhaust system of claim 1 1 , wherein the outer walls of the first diffuser section and the second diffuser section define at least in part a rotary component opening configured to provide clearance for a drive shaft of the gas turbine.

16. The exhaust system of claim 15, wherein the outer wall of the second diffuser section defining in part the rotary component opening tapers radially inward as the outer wall of the second diffuser section extends along the longitudinal axis thereof.

17. A gas turbine comprising:

a compressor configured to fluidly couple with a motive gas source and to compress a motive gas received from the motive gas source;

a combustor fluidly coupled to the compressor and a fuel source, the combustor configured to combust a compressed motive gas with fuel received from the fuel source; a power turbine having a longitudinal axis and configured to expand a combusted motive gas and generate mechanical power; and

an exhaust system fluidly coupled with the power turbine and configured to receive an expanded motive gas, the exhaust system comprising

a housing;

a first diffuser section comprising

a longitudinal axis coaxial with the longitudinal axis of the power turbine;

an outer wall forming a first portion of the housing; and

an annular exhaust system inlet defined in part by the outer wall of the first diffuser section and fluidly coupled to a power turbine outlet of the power turbine;

a second diffuser section fluidly coupled to the first diffuser section and comprising a longitudinal axis disposed substantially perpendicular to the longitudinal axis of the first diffuser section;

an outer wall forming a second portion of the housing; and an exhaust system outlet defined by the outer wall of the second diffuser section;

18. The gas turbine of claim 17, further comprising an elbow section fluidly coupling the first diffuser section and the second diffuser section, the elbow section defining a portion of the exhaust flow passage and comprising an outer wall forming a third portion of the housing, the plurality of turning vanes extending radially inward from the outer wall of the elbow section and into the exhaust flow passage.

19. The gas turbine of claim 18, wherein the plurality of turning vanes are configured to turn the expanded motive gas flowing through the first diffuser section in an axial direction to flow in a vertical direction through the second diffuser section.

20. The gas turbine of claim 18, wherein:

a cross section of the exhaust flow passage at the exhaust system outlet is substantially rectangular in shape;

a cross section of the exhaust flow passage at a location in the first diffuser section substantially midway between the annular exhaust system inlet and the elbow section is substantially oblong in shape;

the outer walls of the first diffuser section and the second diffuser section define at least in part a rotary component opening configured to provide clearance for a rotary shaft of the gas turbine; and the outer wall of the second diffuser section defining in part the rotary component opening tapers radially inward as the outer wall of the second diffuser section extends along the longitudinal axis thereof.