Patent Description:
Gas turbine engines include compressor and turbine sections in which rows of blades are axially stacked in stages. Each stage typically includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central turbine axis or shaft. In operation, generally, the compressor rotor blades are rotated about the shaft, and, acting in concert with the stator blades, compress a flow of air. This supply of compressed air then is used within a combustor to combust a supply of fuel. The resulting flow of hot expanding combustion gases, which is often referred to as working fluid, is then expanded through the turbine section of the engine. Within the turbine, the working fluid is redirected by the stator blades onto the rotor blades so to power rotation. Stationary shrouds may be constructed about the rotor blades to define a boundary of the hot gas path. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft, and, in this manner, the energy of the fuel is converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, so to produce the supply of compressed air needed for combustion, as well as, rotate the coils of a generator so to generate electrical power. During operation, because of the high temperatures, velocity of the working fluid, and rotational velocity of the engine, many of the components within the hot gas path become highly stressed by extreme mechanical and thermal loads.

Many industrial applications, such as those involving power generation and aviation, still rely heavily on gas turbine engines, and because of this, the design of more efficient engines is an ongoing objective. Even incremental advances in machine performance, efficiency, or cost-effectiveness are meaningful in the competitive markets that have evolved around this technology. While there are several known strategies for improving the efficiency of gas turbines-for example, increasing the size of the engine, firing temperatures, or rotational velocities-each generally places additional strain on hot gas path components that are already highly stressed. As a result, there remains a general need for improved apparatus, methods or systems for alleviating such stresses or, alternatively, enhancing the durability of such components so they may better withstand them. For example, the extreme temperatures of the hot gas path stress the stationary shrouds formed about the rows of rotor blades, causing degradation and shortening the useful life of the component. Novel shroud designs are needed that optimize coolant and sealing efficiency, while also being cost-effective to construct, durable, and flexible in application. Prior art designs aimed at this purpose are known from <CIT>, <CIT> and <CIT>.

The present application describes a turbine having a stationary shroud ring formed about rotor blades according to the appended claim <NUM>.

These and other features of this disclosure will be more completely understood and appreciated by careful study of the following more detailed description of exemplary embodiments of the disclosure taken in conjunction with the accompanying drawings, in which:.

The present disclosure is directed to systems and methods for configuring and cooling components of a turbine, specifically, an inner shroud segment, disposed along a hot gas path. As will be seen, the inner shroud segment of the present invention includes an internal cooling configuration (or "cooling configuration") in which particular channels are formed within the interior of the inner shroud segment.

As used herein, "downstream" and "upstream" are terms that indicate a flow direction of a fluid through a channel or passage. Thus, for example, relative to the flow of working fluid through the turbine, the term "downstream" refers to a direction that generally corresponds to the direction of the flow, and the term "upstream" generally refers to the direction that is opposite of the direction of flow. The term "radial" or "radial direction" refers to movement or position perpendicular to a center line or axis. In relation to this, it may be necessary to describe components that reside at differing radial positions with regard to an axis. As used herein, a first component may be described as being "above" or "raised" or "elevated" in relation to a second component if the first component's radial position is further from the axis than the second component's. Alternatively, if the first component resides further from the axis than the second component, it may be stated herein that the first component is "radially outward" or "outboard" of the second component. If, on the other hand, the first component resides closer to the axis than the second component, it may be stated herein that the first component is "radially inward" or "inboard" of the second component. The term "axial" refers to movement or position parallel to an axis. Finally, the term "circumferential" refers to movement or position around an axis. As provided below, such terms may be used relative to axial direction <NUM>, radial direction <NUM>, and circumferential direction <NUM> defined in relation to the center axis of a turbine engine or turbine.

Turning to the drawings, <FIG> is a block diagram of a gas turbine system or engine (or "gas turbine") <NUM>. As described more below, gas turbine <NUM> may include shroud segments having cooling channels that reduce stress modes in hot gas path components and improve the overall efficiency of the engine. Gas turbine <NUM> may use liquid or gas fuel, such as natural gas and/or a hydrogen rich synthetic gas. As depicted, fuel nozzles <NUM> intake a fuel supply <NUM>, mix the fuel with an oxidant, such as air, oxygen, oxygen-enriched air, oxygen reduced air, or any combination thereof. Once the fuel and air have been mixed, the fuel nozzles <NUM> distribute the fuel-air mixture into a combustor <NUM> in a suitable ratio for optimal combustion, emissions, fuel consumption, and power output.

Gas turbine <NUM> may include one or more fuel nozzles <NUM> located inside one or more combustors <NUM>. The fuel-air mixture combusts in a chamber within combustor <NUM>, thereby creating hot pressurized exhaust gases. Combustor <NUM> directs the exhaust gases (e.g., hot pressurized gas) through a transition piece into alternating rows of stationary stator blades and rotating rotor blades, which causes rotation of a turbine section or turbine <NUM> within a turbine casing. The exhaust gases expand through turbine <NUM> and flow toward an exhaust outlet <NUM>. As the exhaust gases pass through turbine <NUM>, the gases force the rotor blades to rotate a shaft <NUM>. Shaft <NUM> operably connects turbine <NUM> to a compressor <NUM>. Shaft <NUM> defines a center axis of gas turbine <NUM>, including the turbine <NUM> and compressor <NUM> thereof. Shaft <NUM> also is connected to a load <NUM>, e.g., a vehicle or a stationary load, such as an electrical generator in a power plant. Relative to the center axis defined by shaft <NUM>, an axial direction <NUM> is defined, which represents movement along the center axis, a radial direction <NUM> is defined, which represents movement toward or away from the center axis, and a circumferential direction <NUM> is defined, which represents movement around the center axis. Compressor <NUM> also includes blades coupled to shaft <NUM>. As shaft <NUM> rotates, the blades within compressor <NUM> also rotate, thereby compressing air ingested via an air intake <NUM> as the air moves through compressor <NUM> and into fuel nozzles <NUM> and/or combustor <NUM>.

A portion of the compressed air from compressor <NUM> may be diverted to turbine <NUM> without passing through combustor <NUM> to be utilized as a coolant for hot gas path components, such as shrouds and nozzles on the stator, along with rotor blades, disks, and spacers on the rotor. Turbine <NUM> may include one or more shroud segments (e.g., inner shroud segments) having an internal cooling configuration (or "cooling configuration") that includes cooling passages for circulating such coolant to control temperature during operation. As will be seen, cooling configurations of the present disclosure may be used within inner shroud segments more improving coolant efficiency as well as achieving other benefits related to structure and constructability. In this way, cooling configurations of the present disclosure may reduce stress modes, extend component service life, reduce component costs and maintenance costs, and improve engine efficiency.

<FIG> shows an exemplary axial section of a hot gas path <NUM> as would be included within the turbine section of a gas turbine engine. As shown, hot gas path <NUM> may include a rotor blade <NUM> that is part of a row of rotor blades, which is disposed in serial flow relationship axially aft or downstream of a row of stationary turbine stator blades (not shown). Hot gas path <NUM> also may include a stationary shroud segment <NUM>, which is circumferentially disposed about and radially outward or outboard of rotor blade <NUM>. As illustrated, shroud segment <NUM> may include an inner shroud segment <NUM> that resides radially inward or inboard of an outer shroud segment <NUM>. Multiple shroud segments <NUM> may be circumferentially stacked to form a shroud ring disposed just outboard of the row of rotor blades, with each of the shroud segments <NUM> having one or more inner shroud segments <NUM> coupled to one or more outer shroud segments <NUM>. Between the assembly of inner and outer shroud segments <NUM>, <NUM>, a cavity <NUM> may be formed. For example, inner shroud segment <NUM> may be connected to outer shroud segment <NUM> via any conventional process, such as welding, brazing, interference or mechanical fit, so to form and seal cavity <NUM> for the functionality described herein. Inner shroud segment <NUM> and outer shroud segment <NUM> also may be formed as a single piece. During operation, a supply of pressurized cooling air or coolant may be delivered to cavity <NUM> via one or more coolant supply channels <NUM>, which may be formed through outer shroud segment <NUM>. As will be seen, coolant supplied to cavity <NUM> may then be directed into cooling passages or channels formed through the interior of inner shroud segment <NUM>.

In regard to its general configuration and orientation within the turbine section, inner shroud segment <NUM> may be described as follows. As indicated in <FIG> and <FIG>, inner shroud segments <NUM> includes an upstream or leading edge <NUM> that opposes a downstream or trailing edge <NUM>. Inner shroud segment <NUM> includes a first circumferential edge <NUM> that opposes a second circumferential edge <NUM>, with the first and second circumferential edges <NUM>, <NUM> extending between the leading edge <NUM> and the trailing edge <NUM>. Further, inner shroud segment <NUM> is formed by a pair of opposed lateral sides or faces <NUM>, <NUM> that extend between leading and trailing edges <NUM>, <NUM> and first and second circumferential edges <NUM>, <NUM>. As used herein, opposed lateral faces <NUM>, <NUM> include an outboard face <NUM> and inboard face <NUM>. Outboard face <NUM> is directed toward outer shroud segment <NUM> and/or cavity <NUM>, while inboard face <NUM> is directed toward the hot gas path <NUM> and defines a boundary thereof. As will be appreciated, inboard face <NUM> may be substantially planar between leading and trailing edges <NUM>, <NUM>, while having a gradual arcuate shape between first and second circumferential edges <NUM>, <NUM>.

Positioned as it is about the central axis of turbine <NUM>, the shape and dimensions of inner shroud segment <NUM> may further be described relative to axial, radial and circumferential directions <NUM>, <NUM>, <NUM> of turbine <NUM>. Thus, opposed leading and trailing edges <NUM>, <NUM> are offset in the axial direction <NUM>. As used herein, the distance of this offset in the axial direction <NUM> is defined as the width dimension (or "width") of inner shroud segment <NUM>. Additionally, opposed first and second circumferential edges <NUM>, <NUM> of inner shroud segment <NUM> are offset in the circumferential direction <NUM>. As used herein, the distance of this offset in the circumferential direction <NUM> is defined as the length dimension (or "length") of inner shroud segment <NUM>. Finally, the opposed inner and outboard faces <NUM>, <NUM> of inner shroud segment <NUM> are offset in the radial direction <NUM>. As used herein, the distance of this offset in the radial direction <NUM> is defined as the height dimension (or "height") of inner shroud segment <NUM>.

With reference now to <FIG>, a cross-sectional side view is provided of adjacent first and second inner shroud segments 35a, 35b in accordance with an exemplary hot gas path configuration. As indicated, adjacent inner shroud segments 35a, 35b abut one another along an interface <NUM> formed between first circumferential edge <NUM> of first inner shroud segment 35a and second circumferential edge <NUM> of second inner shroud segments 35b. As part of interface <NUM>, a seal <NUM> is provided. Seal <NUM> includes slots <NUM> formed within each of the abutting circumferential edges <NUM>, <NUM> for receiving a corresponding sealing member <NUM>. In each case, slots <NUM> may extend along respective circumferential edges <NUM>, <NUM> from leading edge <NUM> to trailing edge <NUM> of respective inner shroud segments 35a, 35b. A sealing member <NUM> is positioned within slots <NUM>. Sealing member <NUM> may also extend from leading edge <NUM> to trailing edge <NUM> of inner shroud segments 35a, 35b. It will be appreciated that once inner shroud segments 35a, 35b are assembled to form interface <NUM>, slots <NUM> cooperate or align to form a seal chamber that spans across interface <NUM>. Sealing member <NUM> is correspondingly shaped to the seal chamber so that, once installed, it spans across interface <NUM> and thereby prevents or limits exhaust gases from leaking or escaping from hot gas path <NUM> therethrough.

With reference now to <FIG>, an exemplary inner shroud segment <NUM> is shown that includes several aspects and features of the present disclosure. As inner shroud segment <NUM> of <FIG> includes the same general configuration and components as introduced above in relation to <FIG> and <FIG>, it has been labeled using like reference numerals. As will be described more below, present inner shroud segment <NUM> may additionally include several other novel internal and external configurations and features. For example, inner shroud segments <NUM> of the present disclosure may include cooling configurations having one or more of specifically configured cooling channels for receiving and directing coolant through interior regions. Further, inner shroud segments <NUM> of the present disclosure may include one or more specific exterior or surface configurations or features and/or interior or structural configurations or features, each of which provides benefits related to constructability, durable structure and/or material or weight reduction. As will be seen, aspects of the exterior and/or interior configurations may be enabled by or an enabler of aspects of the interior cooling configuration, where such combinations may enhance functionality, performance, and/or constructability of the component. Thus, alternative embodiments include combining any of the features or embodiments described herein with any of the other features or embodiments described herein. However, unless expressly limited, it should be assumed that the several features and embodiments presented herein also may be used separately without such combination.

As further indicated in <FIG>, inner shroud segment <NUM> may include rails formed on outboard face <NUM> that surround and define an outboard cavity <NUM>. In general, such rails <NUM>, <NUM> represent areas of increased radial height or ridge formed adjacent to and extending along the edges of inner shroud segment <NUM>. For descriptive purposes, the rails may be referred to as circumferential rails <NUM>, which extend adjacent to circumferential edges <NUM>, <NUM>, and axial rails <NUM>, which extend adjacent to leading and trailing edges <NUM>, <NUM>. The central area of inner shroud segment <NUM> surrounded by rails <NUM>, <NUM> may be referred to as a floor <NUM> of outboard cavity <NUM>. Further, the inward facing side of each of rails <NUM>, <NUM> may be referred to as inward side <NUM>. As will be appreciated, outboard cavity <NUM> forms a portion of cavity <NUM>, as shown in <FIG>.

With reference now to <FIG>, an inner shroud segment <NUM> having one or more crossflow cooling channels (or "crossflow channels") <NUM> is introduced in accordance with exemplary embodiments of the present disclosure. For convenience, components and elements that correspond to those already identified in the preceding figures are identified with similar reference numerals, but only particularly discussed as necessary for an understanding of the present embodiments. It should be appreciated that, while much of the following discussion describes characteristics of crossflow channels <NUM> with reference to a single, exemplary crossflow channel <NUM>, cooling configurations of the present disclosure may include any number of such crossflow channels <NUM>, e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc. <FIG> provides a simplified cross-sectional view showing the basic orientation and position of an exemplary crossflow channel <NUM>. <FIG> provides a schematic top view of an exemplary crossflow channel <NUM>, which will be used to discuss particular characteristics. Finally, <FIG> provides a transparent, perspective view of an inner shroud segment <NUM> in which an exemplary arrangement having multiple crossflow channels <NUM> is shown.

As shown in <FIG>, crossflow channels <NUM> of the present invention extend lengthwise between a first or upstream end <NUM> and a second or downstream end <NUM>. Between upstream end <NUM> and downstream end <NUM>, crossflow channel <NUM> are described in accordance with a junction point <NUM> that, for the purposes of description, divides crossflow channel <NUM> lengthwise into connected sections, in which a first or upstream section <NUM> connects to a second or downstream section <NUM>. Upstream section <NUM> extends between upstream end <NUM> and junction point <NUM>, while downstream section <NUM> extends between junction point <NUM> and downstream end <NUM>.

As shown in <FIG> and <FIG>, crossflow channels <NUM> of the present invention are configured having a variable cross-sectional flow area, i.e., one that varies lengthwise between upstream and downstream ends <NUM>, <NUM>. According to the present invention the cross-sectional flow area varies such that: the cross-sectional flow area of upstream section <NUM> decreases between upstream end <NUM> and junction point <NUM> (i.e., as upstream section <NUM> extends from upstream end <NUM> to junction point <NUM>); and the cross-sectional flow area of downstream section <NUM> increases between junction point <NUM> and downstream end <NUM> (i.e., as downstream section <NUM> extends from junction point <NUM> to downstream end <NUM>). Thus, crossflow channels <NUM> have a cross-sectional flow area that is similar to that of an hour-glass. That is, the cross-sectional flow area of crossflow channel <NUM> narrows to junction point <NUM>, which represents the "neck" of an hour-glass, and then widens from there. As used herein, junction point <NUM> or neck is the location at which crossflow channel <NUM> comprises a minimum cross-sectional flow area.

The decreasing of the cross-sectional flow area through upstream section <NUM> may be a smooth gradual decrease. The increasing of the cross-sectional flow area through downstream section <NUM> may be a smooth gradual increase. The manner by which the cross-sectional flow area of crossflow channel <NUM> decreases or increases may include a narrowing or widening, respectively, of the crossflow channel <NUM> in one or more dimensional directions <NUM>, <NUM>, <NUM>. According to exemplary embodiments, as shown most clearly in <FIG>, the decreasing of the cross-sectional flow area of upstream section <NUM> is accomplished by a smooth and gradual narrowing in the axial direction <NUM>, while the increasing of the cross-sectional flow area of downstream section <NUM> is accomplished by a smooth gradual widening in the axial direction <NUM>. Though other configurations are possible, according to exemplary embodiments, the decreasing of the cross-sectional flow area of upstream section <NUM> results in the cross-sectional flow area at junction point <NUM> being less than <NUM>% of the cross-sectional flow area at upstream end <NUM>. The increasing of the cross-sectional flow area of downstream section <NUM> similarly may result in the cross-sectional flow area at junction point <NUM> being less than <NUM>% of the cross-sectional flow area at downstream end <NUM>. According to other exemplary embodiments, the decreasing of the cross-sectional flow area of upstream section <NUM> results in the cross-sectional flow area at junction point <NUM> being less than <NUM>% of the cross-sectional flow area at upstream end <NUM>, and the increasing of the cross-sectional flow area of downstream section <NUM> results in the cross-sectional flow area at junction point <NUM> being less than <NUM>% of the cross-sectional flow area at downstream end <NUM>.

Though other configurations are possible, crossflow channel <NUM> of the present disclosure may extend lengthwise along a substantially linear path that is oriented in the circumferential direction <NUM>. That is, the longitudinal axis of crossflow channel <NUM> approximately aligns with or is parallel to the circumferential direction <NUM> of the turbine. Thus, according to exemplary embodiments, crossflow channel <NUM> is oriented within inner shroud segment <NUM> to extend approximately in the circumferential direction <NUM>, for example, forming an angle between crossflow channel <NUM> and the circumferential direction <NUM> that is less than <NUM>°. According to other embodiments, crossflow channel <NUM> is oriented such that an angle formed between crossflow channel <NUM> and the circumferential direction <NUM> is less than <NUM>°. According to exemplary embodiments, crossflow channels <NUM> within the shroud cooling configuration may have a parallel arrangement, i.e., be arranged parallel with respect to each other. Further, as shown in <FIG>, such crossflow channels <NUM> may be configured according to an alternating counterflow arrangement in which adjacent ones of crossflow channels <NUM> have oppositely oriented flow directions, i.e., oriented so that coolant flows in the opposite directions.

Crossflow channel <NUM> may extend across a majority of the length of inner shroud segment <NUM>. For example, according to exemplary embodiments, crossflow channel <NUM> extends across at least <NUM>% of the length of inner shroud segment <NUM>. According to other embodiments, crossflow channel <NUM> extends across at least <NUM>% of the length of inner shroud segment <NUM>. Oriented in this manner shown, the length of crossflow channel <NUM> is defined as the distance in the circumferential direction <NUM> between upstream end <NUM> and downstream end <NUM>. The height of crossflow channel <NUM> is defined as the distance in the radial direction <NUM> between an inner radial floor and an outer radial ceiling of crossflow channel <NUM>. As shown in <FIG>, according to exemplary embodiments, the height of crossflow channel <NUM> may be substantially constant between upstream and downstream ends <NUM>, <NUM>. As previously stated, crossflow channel <NUM> may be disposed near and inner radial face <NUM>. According to preferred embodiments, as shown in <FIG>, crossflow channel <NUM> may maintain a substantially constant distance or offset from inboard face <NUM>. As shown in <FIG>, the width of crossflow channel <NUM> is defined herein as a distance in the axial direction <NUM> between a first side and a second side of crossflow channel <NUM>. According to exemplary embodiments, the decreasing of the cross-sectional flow area of upstream section <NUM> is achieved via a gradual tapering of the width of crossflow channel <NUM>. Similarly, the increasing of the cross-sectional flow area of downstream section <NUM> is achieved via a gradual enlarging or widening of the width of crossflow channel <NUM>.

According to exemplary embodiments, upstream end <NUM> of crossflow channel <NUM> is disposed near first circumferential edge <NUM>. For example, upstream end <NUM> of crossflow channel <NUM> is disposed no further from first circumferential edge <NUM> than a distance equal to <NUM>% of the length of inner shroud segment <NUM>. Similarly, downstream end <NUM> of crossflow channel <NUM> may be disposed near second circumferential edge <NUM>. For example, downstream end <NUM> of crossflow channel <NUM> may be disposed no further from second circumferential edge <NUM> than a distance equal to <NUM>% of the length of inner shroud segment <NUM>.

According to exemplary embodiments, junction point <NUM> is located near the middle portion of crossflow channel <NUM>. For example, according to exemplary embodiments, junction point <NUM> is located within a range of <NUM>% to <NUM>% of the length of crossflow channel <NUM>. According to other embodiments, junction point <NUM> is located within a range of <NUM>% to <NUM>% of the length of crossflow channel <NUM>. Junction point <NUM> also may be located at the midpoint of the length of crossflow channel <NUM>.

According to exemplary embodiments, as indicated most clearly in <FIG>, crossflow channel <NUM> may be supplied coolant via a feed channel <NUM>. Crossflow channel <NUM> also may connect to an outlet channel <NUM> for expelling the coolant passing through it. As will be discussed more below, feed channel <NUM> may extend between an inlet <NUM> formed on an exterior surface of inner shroud segment <NUM> and upstream end <NUM> of crossflow channel <NUM>, while outlet channel <NUM> may extend between downstream end <NUM> of crossflow channel <NUM> and an outlet <NUM> formed on an exterior surface of inner shroud segment <NUM>. For example, inlet <NUM> may be formed within outboard cavity <NUM> of inner shroud segment <NUM> and be in fluid communication with cavity <NUM>. More specifically, inlet <NUM> may be formed on inward side <NUM> of circumferential rails <NUM>. Outlet <NUM> may be formed on the first or second circumferential edges <NUM>, <NUM>. Given this arrangement, it should be appreciated that coolant supplied to cavity <NUM> may be ingested by crossflow channel <NUM> via inlet <NUM>. The coolant then may be directed via feed channel <NUM> to crossflow channel <NUM> for circulation therethrough in order to cool inboard face <NUM> of inner shroud segment <NUM>. Once the coolant has passed through crossflow channel <NUM>, it may be directed by outlet channel <NUM> to outlet <NUM> where it is expelled from inner shroud segment <NUM>.

As further depicted, feed channel <NUM> may be disposed within one of the circumferential rails <NUM> while the corresponding outlet channel <NUM> is disposed within the opposing circumferential rail <NUM>. As will be discussed more below, feed channel <NUM> may slant in an inboard direction from inlet <NUM> toward a connection with upstream end <NUM> of crossflow channel <NUM>. That connection may be near inboard face <NUM>. Feed channel <NUM> may include a curving path that turns the flow direction of the coolant approximately <NUM>° relative to the circumferential direction <NUM>. Outlet channel <NUM> may slant in an outboard direction from the connection it makes with downstream end <NUM> of crossflow channel <NUM> toward outlet <NUM>.

<FIG> provides an exemplary embodiment of an inner shroud segment <NUM> having multiple crossflow channels <NUM>. As depicted, such crossflow channels <NUM> may be oppositely oriented according to an alternating arrangement, which will be referred to herein as an alternating counterflow arrangement. Thus, a first set of crossflow channels <NUM> may be oriented to direct coolant to outlets <NUM> formed on first circumferential edge <NUM>, while a second set of crossflow channels <NUM>, which alternate in placement with ones of the first set, direct coolant to outlets <NUM> formed on second circumferential edge <NUM>. Given this arrangement, the first set of crossflow channels <NUM>, thus, has inlets <NUM> formed on inward side <NUM> of circumferential rail <NUM> of second circumferential edge <NUM>, while the second set of crossflow channels <NUM> has inlets <NUM> formed on inward side <NUM> of circumferential rail <NUM> of first circumferential edge <NUM>. In this way, the present cooling configuration provides coolant evenly to the various interior regions of inner shroud segment <NUM> and, once substantially exhausted, the coolant can be released within interface <NUM> in order to provide cooling and sealing benefits therein. The alternating parallel arrangement of crossflow channels <NUM> allows outlets <NUM> to be spaced evenly and at regular intervals across circumferential edges <NUM>, <NUM>.

The disclosed crossflow channels have been found to cool hot gas components, such as stationary shrouds, using less coolant than conventional cooling configurations, resulting in reduced costs associated with cooling and greater engine efficiency. For example, the crossflow channels of the present disclosure maximize the use of the coolant's heat capacity in a way that maintains a more uniform temperature within the inner shroud segment and, particularly, the region near the inboard face. Because the mass flow rate of the coolant through the crossflow channel remains substantially constant, the decreasing cross-sectional flow area through the upstream section results in an increase in coolant velocity. That is, as the coolant moves from the upstream end to the junction point or neck, the decreasing cross-sectional flow area increases coolant velocity. Since duct flow heat transfer coefficients (HTC) are directly dependent on fluid velocity, the increase in coolant velocity increases HTC as the coolant travels through the upstream section of the crossflow channel. Of course, as any coolant moves through a heated duct, it absorbs heat from the surrounding walls and increases in temperature, making the coolant less effective. According to the present application, however, this increase in temperature/decrease in coolant effectiveness is offset by the increasing heat transfer coefficients resulting from the increasing coolant velocity. In this way, the coolant maintains a relatively constant heat transfer rate as it moves through the upstream section of the crossflow channel. The junction point or neck may be positioned along the length of the crossflow channel. For example, the junction point may be position so that once the coolant moving through the crossflow channel has absorbed substantially all the heat it is capable of absorbing, the cross-sectional flow area widens so that the spent coolant is efficiently directed toward an outlet. According to preferred embodiments, to promote cooling that is uniform through the inner shroud segment, the cooling configuration may have an alternating counterflow arrangement, i.e., neighboring crossflow channels have opposite coolant flow directions. This arrangement results in greater cooling uniformity, as each downstream section of the crossflow channels is compensated by adjacent and flanking upstream sections of the neighboring crossflow channels.

With reference now to <FIG>, according to the present invention, inner shroud segment <NUM> includes elongated furrows or troughs <NUM>, which may be formed within outboard face <NUM> or, more specifically, within floor <NUM> of outboard cavity <NUM> of inner shroud segment <NUM>. Each trough <NUM> may extend lengthwise between ends <NUM> positioned near the opposing circumferential rails <NUM> of inner shroud segment <NUM>. Along this length, each trough <NUM> may have a variable depth and width. As used herein, the depth of trough <NUM> is defined as the distance in the radial direction <NUM> between the surrounding surface of floor <NUM> and the lowest point within trough <NUM>. The width of trough <NUM> is defined as the distance in the axial direction <NUM> between opposing sides <NUM> of trough <NUM>. The variable depth and width may include trough <NUM> being shallower and narrower, respectively, at ends <NUM> and then deeper and wider, respectively, as trough <NUM> extends toward a central area or midline, which is defined via dividing line <NUM>. Thus, trough <NUM> may widen and deepen as it extends inwardly from ends <NUM> toward dividing line <NUM>. As illustrated, dividing line <NUM> may be a reference location designating the point along the length of trough <NUM> having the greatest width and depth.

The widening of trough <NUM> from each of ends <NUM> may be smooth and gradual. As indicated in <FIG>, the widening of trough <NUM> from each of end <NUM> may be linear and, thus, describable in accordance with an angle <NUM> formed between sides <NUM>. Though other configurations are possible, angle <NUM> may be between <NUM>° and <NUM>°. According to preferred embodiments, as shown in <FIG>, the widening of trough <NUM> may correspond to the narrowing of the pair of crossflow channels <NUM> that are formed to each side of the trough <NUM>. The narrowing of adjacent crossflow channels <NUM> toward their respective necks or junction points <NUM>, as described above, may make available the room for trough <NUM> to widen and deepen, while also maintaining a close side-by-side relationship between trough <NUM> and neighboring crossflow channels <NUM>. The widening and deepening of each of the troughs <NUM> may be configured such that a substantially constant distance is maintained between the sides of the trough <NUM> and the sides of the pair of crossflow channels <NUM> that flank the trough <NUM>. Further, dividing line <NUM> of trough <NUM> may align circumferentially with junction points <NUM> of the adjacent crossflow channels <NUM>. According to exemplary embodiments, dividing line <NUM> is located within a range of <NUM>% to <NUM>% of the length of trough <NUM>. According to other embodiments, dividing line <NUM> is located within a range of <NUM>% to <NUM>% of the length of trough <NUM>.

The deepening of trough <NUM> from each of ends <NUM> may be smooth and gradual. As shown in <FIG>, trough <NUM> may deepen from each of end <NUM> according to a relatively shallow first angle <NUM>. For example, though other configurations are also possible, first angle <NUM> may be between <NUM>° and <NUM>°. As shown in <FIG>, trough <NUM> may deepen from each side <NUM> according to a second angle <NUM>, which is generally steeper than first angle <NUM>. Though other configurations are also possible, second angle <NUM> (or "angle of descent") may be between <NUM>° and <NUM>°.

Though other configurations are possible, trough <NUM> of the present disclosure may be substantially linear and oriented in the circumferential direction <NUM>. That is, the longitudinal axis of trough <NUM> may approximately align with or be parallel to the circumferential direction <NUM> of the turbine. Thus, according to exemplary embodiments, trough <NUM> may be oriented within inner shroud segment <NUM> to extend approximately in the circumferential direction <NUM>, and is arranged parallel to any of the embodiments of crossflow channels <NUM> discussed above. Each of troughs <NUM> is positioned between and extend lengthwise in parallel to the pair of the crossflow channels <NUM> that flank it. Trough <NUM> may extend in this way across a majority of the length of inner shroud segment <NUM>. For example, according to exemplary embodiments, trough <NUM> extends across more than <NUM>% of the length of inner shroud segment <NUM>. According to other embodiments, trough <NUM> extends across at least <NUM>% of the length of inner shroud segment <NUM>. Multiple, parallel troughs <NUM> may be provided, as illustrated.

The inclusion of the troughs embodiments described herein may provide several advantages to inner shroud segments. First, the troughs provide a way to remove material from inner shroud segments, making the components more economical to produce as well as advantageously reducing overall weight of the engine. Second, configured as they are, the troughs may together form a corrugated truss-like structure between the leading and trailing edges of the inner shroud segment that remains rigid so that the removal of material does not negatively impact structural robustness. Third, the troughs increase the surface area of the outboard face of the inner shroud segment. As the outboard face is exposed to cooler temperatures, this benefits the temperature profile through the component during operation. Fourth, the manner in which the troughs correspond to the variable shape of the crossflow channels results in increased surface area of the outboard face residing near the crossflow channels, which is reduces coolant temperature therein and enhances its effectiveness.

With reference now to <FIG>, further embodiments of interior cooling configurations of the present disclosure will be presented. For convenience, components and elements that correspond to those already identified in the preceding figures-particularly those related to crossflow channel <NUM> of <FIG>-are identified with similar reference numerals, but only particularly discussed as necessary for an understanding of present embodiments. As will be seen, embodiments of <FIG> include additional characteristics and embodiments related primarily to feed channel <NUM> and outlet channel <NUM>. These characteristics will be discussed in relation to both: <NUM>) a single cooling channel having feed channel <NUM> as an upstream section, a middle section (e.g., crossflow channel <NUM>), and outlet channel <NUM> as a downstream section; and <NUM>) a feed and outlet channel configuration <NUM> that includes adjacent feed and outlet channels <NUM>, <NUM> that attach to adjacent counterflowing cooling channels, such as a pair of adjacent crossflow channels <NUM>. In regard to the latter, the discussion of feed and outlet channel configuration <NUM> focuses on the manner in which neighboring feed and outlet channels <NUM>, <NUM> are configured in relation to each other for improved cooling performance, spatial efficiency, and structural robustness.

For example, feed and outlet channel configurations <NUM> may be disposed near an edge of inner shroud segment <NUM>-as depicted, first or second circumferential edges <NUM>, <NUM>-and function to supply/remove coolant to/from a pair of adjacent counterflowing crossflow channels <NUM> (also "paired counterflowing crossflow channels <NUM>"). As will be seen, embodiments of feed and outlet channel configuration <NUM> provide an efficient way by which paired counterflowing crossflow channels <NUM> may have coolant delivered thereto and removed therefrom, while also providing enhanced cooling performance. <FIG> present transparent outer and inner radial views, respectively, of feed and outlet channel configuration <NUM> in accordance with the present disclosure. <FIG> shows a transparent perspective view with cross-section taken along one of the feed channels <NUM> within an exemplary feed and outlet channel configuration <NUM>, while <FIG> shows a transparent perspective view with cross-section taken along one of the outlet channels <NUM> within an exemplary feed and outlet channel configuration <NUM>. Finally, <FIG> shows a perspective view with cross-section taken transverse to both feed channel <NUM> and outlet channel <NUM> in accordance with the present disclosure.

According to an exemplary embodiment, each crossflow channel <NUM> may connect to a feed channel <NUM> at an upstream end <NUM> and an outlet channel <NUM> at a downstream end <NUM>, wherein feed channel <NUM> and outlet channel <NUM> may include any of the characteristics of the embodiments disclosed herein. According to exemplary operation, cooling channels configured in this manner may generally function as follows. The cooling channel may ingest coolant via inlet <NUM>, and then deliver that coolant to crossflow channel <NUM> via feed channel <NUM>. Coolant then may pass through crossflow channel <NUM> and, thereby, cool inboard face <NUM> of inner shroud segment <NUM>. Once it has passed through crossflow channel <NUM>, then coolant may be directed via outlet channel <NUM> to outlet <NUM>, whereupon it is expelled from inner shroud segment <NUM>.

In regard to embodiments of feed and outlet channel configurations <NUM>, specific characteristics will now be presented with reference to the illustrated configurations. For example, feed and outlet channel configuration <NUM> may connect to a pair of adjacent counterflowing crossflow channels <NUM>, which, as already described, may extend side-by-side across inner shroud segment <NUM>. According to preferred embodiments, feed and outlet channel configuration <NUM> is disposed at each opposing end of such a pair of adjacent counterflowing crossflow channels <NUM>. More generally, feed and outlet channel configuration <NUM> may be repeated as necessary within inner shroud segment <NUM> so that it is used with each such pair of counterflowing adjacent crossflow channels <NUM>. For purposes of describing an exemplary feed and outlet channel configuration <NUM>, the pair of corresponding adjacent counterflowing crossflow channels <NUM> will be referenced as including a first crossflow channel <NUM>, which connects to feed channel <NUM>, and a second crossflow channel <NUM>, which connects to outlet channel <NUM>.

Feed and outlet channel configuration <NUM> generally includes a feed channel <NUM> and an adjacent or neighboring outlet channel <NUM>. Both may be disposed near an edge of inner shroud segment <NUM>, for example, first and second circumferential edges <NUM>, <NUM>. Feed channel <NUM> may extend between an inlet <NUM> formed on an exterior surface of inner shroud segment <NUM> and a connection made with the first crossflow channel <NUM> of the paired crossflow channels <NUM>. According to preferred embodiments, inlet <NUM> may be formed through outboard face <NUM> of inner shroud segment <NUM> so that inlet <NUM> fluidly communicates with cavity <NUM> and/or outboard cavity <NUM> of inner shroud segment <NUM>. For example, inlet <NUM> may be formed on inward side <NUM> of circumferential rail <NUM> of first circumferential edge <NUM>. As another example, when feed and outlet channel configuration <NUM> occurs on the opposite side of inner shroud segment <NUM>, inlet <NUM> may be formed on inward side <NUM> of circumferential rail <NUM> of second circumferential edge <NUM>. In regard to outlet channel <NUM>, it may extend between a connection made with the second crossflow channel <NUM> of paired crossflow channels and an outlet <NUM> formed on an exterior surface of inner shroud segment <NUM>. For example, outlet <NUM> may be formed on first circumferential edge <NUM>. When feed and outlet channel configuration <NUM> occurs on the opposite side of inner shroud segment <NUM>, outlet <NUM> may be formed on second circumferential edge <NUM>.

In accordance with example embodiments, certain configurational attributes of feed and outlet channel configuration <NUM> will now be described. For purposes of description, the shape of feed and outlet channels <NUM>, <NUM> within such embodiments will be described primarily in two ways. With the first of these, an outer radially or "outboard perspective" will be referenced. As used herein, an "outboard perspective" is intended as a view looking in an inboard direction from a position directly outboard of the feature being described. This perspective will be useful in describing how the paths of feed channel <NUM> and outlet channels <NUM> are shaped in the axial and circumferential directions <NUM>, <NUM>. The second way to describe the configuration will be with reference to relative changes in radial position.

With that in mind, according to preferred embodiments, feed channel <NUM> initially slants in an inboard direction from a radially elevated initial position at inlet <NUM> to the approximate radial level of floor <NUM> or crossflow channels <NUM>, which may be near inboard face <NUM>. From the outboard perspective, this first slanting section may be substantially linear and aligned with the circumferential direction <NUM>. From the outboard perspective, feed channel <NUM> may continue via a curving or looping second section that turns the flow of coolant approximately <NUM>° before feed channel <NUM> connects with upstream end <NUM> of first crossflow channel <NUM>. Thus, while the initial flow direction in feed channel <NUM> is directed toward first circumferential edge <NUM>, at the connection that feed channel <NUM> makes with first crossflow channel <NUM>, the flow direction is circumferentially reversed so that the flow of coolant is now being directed toward second circumferential edge <NUM>. From the outboard perspective, in making this <NUM>° turn, the curvature of feed channel <NUM> bows outward toward outlet channel <NUM>. From the outboard perspective, this second or bowed section <NUM> is configured to undercut a section of outlet channel <NUM>. More specifically, again, from the outboard perspective, bowed section <NUM> of feed channel <NUM> axially and circumferentially overlaps a section of outlet channel <NUM>, while being radially offset therefrom in the inboard direction.

From the outboard perspective, upstream end <NUM> of first crossflow channel <NUM> may be positioned to overlap axially with inlet <NUM>, while being radially offset therefrom in the inboard direction. Thus, from the outboard perspective, as shown most clearly in <FIG>, feed channel <NUM> may continue to loop around-almost completing an entire circle-before reversing its curvature and straightening out so to connect with upstream end <NUM> at a position that axially overlaps with inlet <NUM>.

According to preferred embodiments, a first section of outlet channel <NUM> may slant in an outboard direction from the connection outlet channel <NUM> makes with downstream end <NUM> of crossflow channel <NUM>. More specifically, as shown most clearly in <FIG>, outlet channel <NUM> may include a first or outboard slanting section <NUM> that carries coolant from an initial radial position that is near inboard face <NUM> to a raised outboard position that is outboard of the radial midpoint of circumferential rail <NUM>. After outboard slanting section <NUM>, a second section of outlet channel <NUM> may then flatten out radially and extend toward outlet <NUM>, which may be disposed on first circumferential edge <NUM>. As will be appreciated, outboard slanting section <NUM> provides the inner radially space necessary for the bowed section <NUM> of feed channel <NUM> to undercut outlet channel <NUM>. From the outboard perspective, as shown most clearly in <FIG>, outlet channel <NUM> may maintain a linear path between downstream end <NUM> and outlet <NUM>. This linear path may be aligned approximately with the circumferential direction and/or provide a continuation of the linear path defined by second crossflow channel <NUM>.

As a further feature, inward side <NUM> of circumferential rail <NUM> may include a corrugated configuration <NUM> with alternating ridges <NUM> and valleys <NUM>, which, as will be seen, may be configured to correspond to the placement of feed and outlet channels <NUM>, <NUM> with feed and outlet channel configurations <NUM>. Generally, ridges <NUM> and valleys <NUM> may extend in the circumferential direction and slant in the outboard direction along a contour of inward side <NUM> of circumferential rail <NUM>. As shown most clearly in <FIG>, a circumferentially extending ridge <NUM> may be formed about each of the outboard slanting sections <NUM> of outlet channels <NUM>. Specifically, each ridge <NUM> may be configured to correspond to the shape of outboard slanting section <NUM> of one of the outlet channels <NUM>, generally wrapping around the outer radial half of this section. Between each of the neighboring ridges <NUM>, a circumferentially extending depression or valley <NUM> may be formed, within which inlet <NUM> for feed channel <NUM> may be located. As indicated in the several figures, corrugated configuration <NUM> may be repeated along inward side <NUM> for each of the circumferential rails <NUM> so that it corresponds with the repetition of feed and outlet channel configuration <NUM>. For descriptive purposes, it will be appreciated that within the corrugated configuration <NUM>, the "ridge" portion is a feature that juts in an outboard direction, while the "valley" portion is a cut away portion or depression made in the inboard direction.

The advantages of corrugated configuration <NUM> include the removal of excess material while maintaining the structural robustness of the component. Further, corrugated configuration <NUM> provides benefits related to enabling or enhancing aspects of feed and outlet channel configuration <NUM>. For example, ridge <NUM> enables outboard slanting section <NUM> of outlet channels <NUM> to extend circumferentially at a steeper angle, which produces the space to the inboard side of it for feed channel <NUM> to curl under it in the manner discussed above. As another example, valleys <NUM> enable the positioning of inlet <NUM> at a lower radial height, which also facilitates feed channel <NUM> curling under outlet channel <NUM> in the desired manner. Further, the lower radial height of inlet <NUM> results in a shorter length of feed channel <NUM>, which decreases aerodynamic losses.

With reference now to <FIG> and <FIG>, structural configurations will be disclosed that, for example, may be used within to support leading or trailing axial rails <NUM>. <FIG> is a transparent view of an exemplary structural configuration of axial rails <NUM>, i.e., the rails that are formed along either leading or trailing edges <NUM>, <NUM>, while <FIG> provides an enhanced view of particular aspects of that structural configuration. According to exemplary embodiments, the structural configuration may include a truss-like arrangement or structure (or "truss structure") <NUM> that is formed within the interior of axial rail <NUM> for structural support. As illustrated, truss structure <NUM> may include a repeating arrangement of members <NUM> having a triangular shape, which allows for the removal of material to form a repeating triangular hollow portion <NUM> from axial rail <NUM>. The triangular shape may extend between an outboard edge of the axial rail and an inboard edge of the axial rail. The members <NUM> may include a slanting member that slants between the outboard edge and the inboard edge of axial rail <NUM>. The angle <NUM> that the slanting member makes with each edge of the truss structure <NUM> may be <NUM>° or less. According to preferred embodiments, the angle <NUM> that the slanting member makes with each edge of the truss structure <NUM> may be <NUM>° or less.

It has been found that truss structure <NUM> at axial rail <NUM> allows for the removal of significant material, i.e., the triangular hollow portions, which result in weight and cost savings, while also maintaining acceptable structural rigidity and support. Further, as discussed more below, truss structure <NUM> is configured such that it may be produced efficiently by additive manufacturing processes in accordance with necessary requirements and without the limitations of a minimum wall thickness, as would be required for casting.

The above-described surface and interior configurations and cooling channel embodiments for hot gas path components, e.g., inner shroud segments, may be formed or constructed via any conventional manufacturing technique, including electrical discharge machining, drilling, casting, additive manufacturing, a combination thereof, or any other technique. As will now be discussed, certain aspects the above-disclosed embodiments are particularly configured to provide constructability advantages for expedited and cost-effective manufacture via additive manufacturing processes.

For example, with certain additive manufacturing process, such as selective deposition additive manufacturing, material is deposited on previously formed or deposited portions of the component, to progressively build a component along a build direction (which may be substantially vertical) in a self-supporting manner. In selective deposition additive manufacture, material can be deposited so that newly-deposited material overhangs the supporting material by a limited extent. Such newly-deposited material is said to overhang by an "overhang angle", typically measured from the vertical. It has been found that, in order to reliably and accurately manufacture a self-supporting structure in selective deposition additive manufacturing, an overhang angle of an overhanging part should be no more than <NUM>° from the vertical axis. The surface finish of the component may be affected by the overhang angle of the component, such that a smaller overhang angle, such as less than <NUM>° from the vertical axis, generally results in a better surface finish. Surface finish may affect the life of a hot gas component like an inner shroud segment, therefore this is an important consideration. Specifically, for a component which will endure high stresses of the hot gas path, a smaller angle from the vertical axis may be required in order for it to have an acceptable surface finish and therefore an acceptable component life.

Embodiments of inner shroud segment <NUM> disclosed herein are configured so that typical build directions result in maximum overhang angles of approximately <NUM>° or, according to other alternatives, maximum overhang angles of approximately <NUM>°. For example, assuming that the lengthwise axis of the inner shroud segment is aligned with a vertical build direction, the implied overhang angles for constructing trough <NUM> given the ranges provided herein for first and second angles <NUM>, <NUM> would result in a shallow overhang angles of less than less <NUM>° and/or <NUM>°. This is also true if the widthwise axis of the inner shroud segment is instead the axis chosen for alignment with a vertical build direction. As another example, assuming that the lengthwise axis of the inner shroud segment is aligned with a vertical build direction, the implied overhang angles for constructing the angled members <NUM> of truss structure <NUM> given the ranges provided herein for angle <NUM> would result in a shallow overhang angles of less than less <NUM>° and/or less than <NUM>°.

Claim 1:
A turbine (<NUM>) of a gas turbine engine (<NUM>), the turbine (<NUM>) comprising a stationary shroud ring having an inner shroud segment (<NUM>), the inner shroud segment (<NUM>) comprising a cooling configuration in which crossflow channels (<NUM>) are configured to receive and direct a coolant through an interior of the inner shroud segment (<NUM>), characterised in that the crossflow channels (<NUM>) are disposed between troughs (<NUM>) extending lengthwise in parallel to the crossflow channels (<NUM>);
wherein each crossflow channel (<NUM>):
has a length defined as a distance in a circumferential direction (<NUM>) between an upstream end (<NUM>) and a downstream end (<NUM>) of the crossflow channel (<NUM>);
has a width defined as a distance in an axial direction (<NUM>) between opposing sides of the crossflow channel (<NUM>);
has a height defined as a distance in a radial direction (<NUM>) between a floor and a ceiling of the crossflow channel (<NUM>);
comprises a junction point (<NUM>) at which the crossflow channel (<NUM>) has a minimum cross-sectional flow area, the junction point (<NUM>) located between the upstream and downstream ends (<NUM>, <NUM>) and dividing the crossflow channel (<NUM>) lengthwise into upstream and downstream sections (<NUM>, <NUM>), the upstream section (<NUM>) extending between the upstream end (<NUM>) and the junction point (<NUM>) and the downstream section (<NUM>) extending between the junction point (<NUM>) and the downstream end (<NUM>); and
comprises a cross-sectional flow area that varies lengthwise such that a cross-sectional flow area of the upstream section (<NUM>) continuously decreases between the upstream end (<NUM>) and the junction point (<NUM>), and a cross-sectional flow area of the downstream section (<NUM>) continuously increases between the junction point (<NUM>) and the downstream end (<NUM>);
wherein each trough (<NUM>):
elongates between ends (<NUM>) that define a length of the trough (<NUM>) in the circumferential direction (<NUM>);
has a width defined as a distance in the axial direction (<NUM>) between opposing sides (<NUM>) of the trough (<NUM>);
has a depth defined as a distance in the radial direction (<NUM>) between a surrounding surface of a floor (<NUM>) of an outboard face (<NUM>) of the inner shroud segment (<NUM>) and a lowest point within the trough (<NUM>); and
wherein each of the troughs (<NUM>) comprise a width and depth that varies along the length of the trough (<NUM>).