GAS TURBINE SHROUD COOLING

Abstract

A shroud segment for a casing of gas turbine includes a body configured for attachment to the casing proximate a localized critical process location within the casing. The body has a leading edge, a trailing edge, and two side edges. The critical process location is located between the leading edge and the trailing edge when the body is attached to the casing. A cooling passage is defined in the body along one of the side edges with one of an inlet or an outlet proximate the critical process location. The cooling passage is configured large enough to cool the one side edge adjacent the cooling passage to a desired level during operation of the gas turbine. The critical process locations may be related to temperatures, pressures or other measurable features of the gas turbine environment when in use.

Description

FIELD OF THE INVENTION

The present invention generally involves cooling a turbine shroud element that may be located in a hot gas path of the turbine.

BACKGROUND OF THE INVENTION

Turbines are widely used in a variety of aviation, industrial, and power generation applications to perform work. Each turbine generally includes alternating stages of peripherally mounted stator vanes and rotating blades. The stator vanes may be attached to a stationary component such as a casing that surrounds the turbine, and the rotating blades may be attached to a rotor located along an axial centerline of the turbine. A compressed working fluid, such as steam, combustion gases, or air, flows along a gas path through the turbine to produce work. The stator vanes accelerate and direct the compressed working fluid onto the subsequent stage of rotating blades to impart motion to the rotating blades, thus turning the rotor and performing work. If any compressed working fluid moves radially outside of the desired flow path, the efficiency of the turbine may be reduces. As a result, the casing surrounding the turbine often includes a radially inner shell of shrouds, often formed in segments. The shrouds surround and define the outer perimeter of the hot gas path and may be located around both stator vanes and rotating blades.

The turbine shrouds are typically cooled in some fashion to remove heat transferred by the hot gas path. U.S. Pat. No. 7,284,954 describes a turbine shroud segment that includes many small cooling fluid passages machined throughout the turbine shroud. A fluid such as compressed air from an upstream compressor may be supplied through the fluid passages to cool the turbine shroud. Other shroud segments utilize a single larger “core” flow path cast in place rather than multiple small machined passages as above. The core extends along an entire side of the shroud segment from an axially upstream end to an axially downstream end.

While both types of shroud segment cooling passages work well, continued improvements in systems to cool turbine shrouds would be welcome, particularly systems that improve the amount of cooling provided by a given flow and/or that allow selective targeting of cooling at desired locations axially along the shroud segments.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

According to certain aspects of the present disclosure, a shroud segment for a casing of gas turbine may include a body configured for attachment to the casing proximate a localized critical process location within the casing. The body has a leading edge, a trailing edge, and two side edges, as well as a first surface for facing the casing and a second surface opposite the first surface for facing a hot gas path. The critical process location is located between the leading edge and the trailing edge when the body is attached to the casing. At least two cooling passages are defined in the body along one of the side edges. A first of the cooling passages has an inlet and extends to an outlet, one of the inlet or outlet being adjacent the critical process location. A second of the cooling passages has an inlet and extends to an outlet, one of the inlet or the outlet being adjacent the critical process location. The first and second cooling passages are configured large enough to cool the one side edge to a desired level during operation of the gas turbine. Various options and modifications are possible.

According to certain other aspects of the present disclosure, a gas turbine may include a compressor section, a combustion section downstream from the compressor section, and a turbine section downstream from the combustion section. The turbine section includes a casing defining a localized critical process location and a plurality of shroud segments circumferentially attached to the casing. Each shroud segment includes a body configured for attachment to the casing. At least one of the bodies has a leading edge, a trailing edge, and two side edges, as well as a first surface facing the casing and a second surface opposite the first surface facing a hot gas path. The critical process location is located between the leading edge and the trailing edge when the body is attached to the casing. At least two cooling passages are defined in the body along one of the side edges. A first of the cooling passages has an inlet and extends to an outlet, one of the inlet or outlet being adjacent the critical process location. A second of the cooling passages has an inlet and extends to an outlet, one of the inlet or the outlet being adjacent the critical process location. The first and second cooling passages are configured large enough to cool the one side edge to a desired level during operation of the gas turbine. As above, various options and modifications are possible.

Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a schematic view of an exemplary gas turbine incorporating aspects of the present disclosure;

FIG. 2 is a simplified cross-section view of a portion of the gas turbine of FIG. 1 showing a shroud segment;

FIG. 3 is a top view of a shroud segment as in FIG. 2;

FIG. 4 is a side view of the shroud segment of FIG. 3;

FIG. 5 is a sectional view of the shroud segment taken along line 5-5 in FIG. 3;

FIG. 6 is an isometric view of the shroud segment of FIG. 3;

FIG. 7 is a top view of a first alternate shroud segment;

FIG. 8 is a top view of a second alternate shroud segment; and

FIG. 9 is a top view of a third alternate shroud segment.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. In addition, the terms “upstream” and “downstream” refer to the relative location of components in a fluid pathway. For example, component A is upstream from component B if a fluid flows from component A to component B. Conversely, component B is downstream from component A if component B receives a fluid flow from component A.

Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 is a schematic view of an exemplary gas turbine that can incorporate a shroud element according to the present disclosure. As illustrated, gas turbine 110 includes an inlet section 111, a compressor section 112, a combustion section 114, a turbine section 116, and an exhaust section 117. A shaft (rotor) 122 may be common to compressor section 112 and turbine section 116, and may further connect to a generator 105 for generating electricity.

The compressor section 112 may include an axial flow compressor in which a working fluid 100, such as ambient air, enters the compressor from the inlet section 111 and passes through alternating stages 113 of stationary vanes and rotating blades (shown schematically in FIG. 1). Compressor casing 118 contains the working fluid 100 as the stationary vanes and rotating blades accelerate and redirect the working fluid to produce a continuous flow of compressed working fluid. The majority of the compressed working fluid flows downstream through the combustion section 114 and then the turbine section 116.

The combustion section 114 may include any type of combustor known in the art. A combustor casing 115 may circumferentially surround some or all of the combustion section 114 to direct the compressed working fluid 100 from the compressor section 112 to a combustion chamber 119. Fuel 101 is also supplied to the combustion chamber 119. Possible fuels include, for example, one or more of blast furnace gas, coke oven gas, natural gas, vaporized liquefied natural gas (LNG), hydrogen, and propane. The compressed working fluid 100 mixes with fuel 101 in the combustion chamber 119 where it ignites to generate combustion gases having a high temperature and pressure. The combustion gases then enter the turbine section 116.

As shown in FIGS. 1 and 2, within turbine section 116, alternating stages of rotating blades (buckets) 124 and stationary blades (nozzles) 126 are attached to rotor 122 and turbine casing 120, respectively. Working fluid 100, such as steam, combustion gases, or air, flows along a hot gas path through gas turbine 110 from left to right as shown in FIG. 2. The first stage of stationary nozzles 126 accelerates and directs the working fluid 100 onto the first stage of rotating blades 124, causing the first stage of rotating blades 124 and rotor 122 to rotate. Working fluid 100 then flows across the second stage of stationary nozzles 126 which accelerates and redirects the working fluid to the next stage of rotating blades (see FIG. 1), and the process repeats for each subsequent stage.

As shown schematically in FIG. 1, the radially inward portion of turbine casing 120 may include a series of shrouds 128. Shrouds 128 in FIG. 1 are formed around blades 124. FIG. 2 shows shrouds 128 formed around both blades 124 and nozzles 126. Shrouds 128 may be formed in segments, such as segment 130 of FIGS. 2-6. It should be understood that, although an example of a shroud segment related to a blade 124 is shown, the present disclosure incorporates shroud segments formed around nozzles 124 as well. Therefore, no limitation as to location of shrouds within casing 120 should be made.

As shown in FIG. 3, each shroud segment 130 may generally comprise a body having a plurality of sides. Specifically, each segment 130 has a leading edge 132, a trailing edge 134, and two side edges 136 and 138. A first surface 140 faces (radially outwardly) toward casing 120 and a second surface 142 opposite the first surface faces (radially inwardly) toward the hot gas path where the working fluid 100 flows.

A critical process location (defined below) 144 is located between leading edge 132 and the trailing edge 134, generally in alignment with rotating blades 124. The critical process location 144 could be, for example, a maximum or other critical temperature location along the segment during gas turbine use, a maximum or other critical pressure location along the segment during gas turbine use, a maximum or other critical gas side heat transfer coefficient location, or a maximum or other critical stress location. The critical process location 144 could be a location where cooling gases can enter or exit the segment after travelling through a passageway allowing for sufficient cooling of the segment, while still respecting back flow margin limitations.

Also, the critical process location need not be an absolute maximum, it could be any desired value that can be used to determine optimal flow and heat transfer characteristics within the gas turbine or within the segment itself. Much depends on the desired characteristics of the gas turbine, flow at the location of segment 130, etc. The critical process location along segment 130 could vary at different stages within a gas turbine. Further, two or more of such critical process locations could exist along a single segment 130.

At least two cooling passages 146,148 are defined in segment 130 along one of side edges 136. First cooling passage 146 has an inlet 150 that may be (as shown) on first surface 140 near leading edge 132. First cooling passage 146 also has an outlet 152 adjacent critical process location 144. Second cooling passage 148 has an inlet 154 that may be (as shown) on first surface 140 adjacent critical process location 144. Second cooling passage 148 has at least one outlet 156 that may be (as shown) near trailing edge 134.

It should be understood that flow through either or both of passages 146,148 could be reverse of that which is shown. For example, flow in first passage 146 could be counter (directed upstream) to that through second passage 148. In other words, flow could run from opening 152 to opening 150 (reversing inlet/outlet functions), if desired. Flow through second passage 148 could also be similarly reversed.

First and second cooling passages 146,148 may be formed by casting rather than machining. For example, as is known a mold may be used in which a fill substance is provided matching the path of first and second cooling passages 146,148, the fill substance being burned off and/or chemically removed afterward leaving the passages. Such manufacture using casting of at least some portion of the passages may be more cost effective than machining the passages or multiple smaller passages. Even if the passages are formed substantially by casting, inlets and outlets to the passages or other features may be machined as part of the manufacture.

First and second cooling passages 146,148 may be configured large enough to cool side edge 136 and/or a related area to a desired level during operation of the gas turbine. The passage sizes are configured to allow sufficient flow that back flow margins are respected, and heat transfer is sufficient to cool segment 130 to a desired temperature. If desired, in one example of a gas turbine, a segment 130 with a length of about 6.5 inch, a width of about 3.0 inch, and general thickness of about 0.25 inch, passages 146, 148 may be of a cross-section of about 0.025 square inch. Accordingly, numerous small passages spread along the locations of cooling passages 146,148 are not required to cool segment 130.

As shown, an additional set of cooling passages 158,160 can be provided on other side edge 138. Passages 158,160 may if desired but not necessarily be substantially symmetrical to passages 146,148 along a central axis running between leading edge 132 and trailing edge 134. As above first cooling passage 158 has an inlet 162 which may be (as shown) on first surface 140 near leading edge 132. First cooling passage 158 also has an outlet 164 adjacent critical process location 144. Second cooling passage 160 has an inlet 166 which may be (as shown) on first surface 140 adjacent critical process location 144. Second cooling passage 160 has at least one outlet 168 which may be (as shown) near trailing edge 134. As shown, inlet 150 and inlet 162 are a common, single inlet. However, as discussed below, the inlets 150,162 may be separate.

Various options and modifications are possible. For example, as shown in FIG. 3, both second passages 148,160 may have multiple outlets 156,168, which may be along trailing edge 134. Such multiple exits may be machined or cast, and may be employed to cool trailing edge 134 if spaced sufficiently from second passages 148,160 to require additional cooling. Some or all of such multiple outlets could instead or also exit segment 130 at locations other than trailing edge 134 if desired.

Alternatively, as shown in FIG. 7, modified segment 130′ has first passages 146′,158′ each with their own individual inlets 150,162 with first portions 170,172 and second portions 174,176 leading to outlets 152,164. As shown in FIG. 3, first portions 170,172 are in communication with each other; as shown. If desired, some or all of the inlets in segment 130 or 130′ could also be located elsewhere other than first surface 140.

As another alternative, as shown in FIG. 8, modified segment 130″ has second passages 148′,160′ each with individual inlets 154,166 leading to first portions 178,180 and second portions 182,184 and then outlet(s) 156,168, as above. However, second portions 182,184 in FIG. 8 are in communication with each other. Therefore, instead of the construction shown in FIG. 3, having one first passage upstream of location 144 and two second passages downstream of location 144, a shroud segment could be made as shown in FIG. 8 with one upstream passage and one downstream passage split along the side edges 136,138 at location 144.

Alternatively, as shown in FIG. 9, splits could be provided at two or more critical process locations along the shroud segment. Along one side of segment 130′″, a first passageway 146 extends from inlet 150 to outlet 152, a second passageway 148′ extends from inlet 154 to outlet 153 and a third passageway 179 extends from inlet 155 to outlets 156. Similarly, along the other side, a first passageway 158 extends from inlet 162 to outlet 164, a second passageway 160′ extends from inlet 166 to outlet 165 and a third passageway 181 extends from inlet 167 to outlets 168. Accordingly, FIG. 9 illustrates that more than one split can be made between leading edge 132 and trailing edge 134 at critical process locations, as desired. It should also be understood that splits need not be symmetrical or even along a given side of the segments or between sides of the segments.

The segments above can be mounted to turbine casings in various known ways, via hooks, impingement plates, clips, etc. The present invention is not limited to any such mounting arrangement, cooling mode, or any particular fluid used to cool the shroud segment. For example, such mounting may or may not provide that the cooling fluid first impacts the segments to provide impingement cooling to the bulk of the segment before some fluid flows through the disclosed passageways. Also, the segments may include mounting structures, cooling passage openings, etc., for receiving, contacting or cooling nozzles 126 if the segments are located along a row of nozzles as opposed to a row of blades 124.

It is anticipated that the various embodiments of the shroud segments shown above may be manufactured at lower costs than previous designs. Specifically, the segments may be cast or forged, with reduced machining required for inlets and outlets and the larger passages being formed by casting. In this manner, the shroud may be readily manufactured to include the desired fluid passages that provide cooling to the sides of the segments. By splitting the passages at critical process location(s) 144 where maximum temperature, pressure or other measurable parameters (maximums or not), cooling can be beneficially located at a desired point while providing a more efficient flow, with less leakage. The segments can thus be tuned in various ways to improve thermal and flow performance.

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 other examples are intended to be within the scope of the claims if they include 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.

Claims

1. A shroud segment for a casing of gas turbine comprising:

a body configured for attachment to the casing proximate a localized critical process location within the casing, the body having a leading edge, a trailing edge, and two side edges, the body having a first surface for facing the casing and a second surface opposite the first surface for facing a hot gas path, the critical process location being located between the leading edge and the trailing edge when the body is attached to the casing; and

at least two cooling passages defined in the body related to one of the side edges, a first of the cooling passages having an inlet and extending to an outlet, one of the inlet or the outlet being adjacent the critical process location, a second of the cooling passages having an inlet and extending to an outlet, one of the inlet or the outlet being adjacent the critical process location, the first and second cooling passages being configured large enough to cool the one side edge to a desired level during operation of the gas turbine.

2. The shroud segment of claim 1, wherein the first cooling passage has a first portion along the leading edge and a second portion along the one side edge.

3. The shroud segment of claim 2, wherein the second cooling passage has a first portion along the one side edge and a second portion along the trailing edge.

4. The shroud segment of claim 1, further including at least two additional cooling passages along the other of the side edges, the two additional cooling passages being substantially symmetrical to the at least two cooling passages with reference to a central plane of the body extending between the leading edge and the trailing edge.

5. The shroud segment of claim 1, wherein the first cooling passage has a second outlet adjacent the critical process location along the other side edge.

6. The shroud segment of claim 5, wherein the first cooling passage includes a first portion along the leading edge and a second portion along the one side edge, a third portion along the leading edge, and a fourth portion along the other side edge.

7. The shroud segment of claim 1, wherein the second cooling passage has a second inlet adjacent the critical process location along the other side edge.

8. The shroud segment of claim 1, wherein the second cooling passage includes a first portion along the one side edge and a second portion along the trailing edge, a third portion along the other side edge, and a fourth portion along the trailing edge.

9. The shroud segment of claim 1, wherein the second cooling passage includes multiple outlets.

10. The shroud segment of claim 1, wherein the body and first and second cooling passages are configured of a cast metal.

11. A gas turbine comprising:

a compressor section;

a combustion section downstream from the compressor section; and

a turbine section downstream from the combustion section, wherein the turbine section includes a casing defining a localized critical process location and a plurality of shroud segments circumferentially attached to the casing, each shroud segment including:

a body configured for attachment to the casing, at least one of the bodies having a leading edge, a trailing edge, and two side edges, the body having a first surface facing the casing and a second surface opposite the first surface facing a hot gas path, the critical process location being located between the leading edge and the trailing edge when the body is attached to the casing; and

at least two cooling passages defined in the body related to one of the side edges, a first of the cooling passages have an inlet and extending to an outlet, one of the inlet or the outlet being adjacent the critical process location, a second of the cooling passages having an inlet and extending to an outlet, one of the inlet or the outlet being adjacent the critical process location, the first and second cooling passages being configured large enough to cool the one side edge to a desired level during operation of the gas turbine.

12. The gas turbine of claim 11, wherein the first cooling passage has a first portion along the leading edge and a second portion along the one side edge.

13. The gas turbine of claim 12, wherein the second cooling passage has a first portion along the one side edge and a second portion along the trailing edge.

14. The gas turbine of claim 11, further including at least two additional cooling passages along the other of the side edges, the two additional cooling passages being substantially symmetrical to the at least two cooling passages with reference to a central plane of the body extending between the leading edge and the trailing edge.

15. The gas turbine of claim 11, wherein the first cooling passage has a second outlet adjacent the critical process location along the other side edge.

16. The gas turbine of claim 15, wherein the first cooling passage includes a first portion along the leading edge and a second portion along the one side edge, a third portion along the leading edge, and a fourth portion along the other side edge.

17. The gas turbine of claim 11, wherein the second cooling passage has a second inlet adjacent the critical process location along the other side edge.

18. The gas turbine of claim 11, wherein the second cooling passage includes a first portion along the one side edge and a second portion along the trailing edge, a third portion along the other side edge, and a fourth portion along the trailing edge.

19. The gas turbine of claim 11, wherein the second cooling passage includes multiple outlets.

20. The gas turbine of claim 11, wherein the body and first and second cooling passages are configured of a cast metal.