Patent Application
20190368378
The subject matter disclosed herein relates to hot gas path components within the turbine of a gas turbine engine, and, more specifically, but not by way of limitation, to the interior structure and cooling configuration of stationary shrouds formed about turbine rotor blades.
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.
The present application describes a turbine of a gas turbine engine that includes a stationary shroud ring having an inner shroud segment. The inner shroud segment may include a cooling configuration in which channels are configured to receive and direct a coolant through an interior of the inner shroud segment. The cooling configuration may include a pair of counterflowing crossflow channels in which a first crossflow channel extends side-by-side with a neighboring second crossflow channel; and a feed and outlet channel configuration comprising neighboring feed and outlet channels. The feed channel may connect at a first connection to an upstream end of the first crossflow channel and the outlet channel may connect at a second connection to a downstream end of the second crossflow channel. The feed channel may extend in an inner radial direction from an inlet formed through an exterior surface of the inner shroud segment to the first connection. The outlet channel may extend in an outer radial direction from the second connection to an outlet formed through an exterior surface of the inner shroud segment. The feed channel may include a section that undercuts the outlet channel.
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 30, radial direction 31, and circumferential direction 32 defined in relation to the center axis of a turbine engine or turbine.
Turning to the drawings,
Gas turbine 10 may include one or more fuel nozzles 12 located inside one or more combustors 16. The fuel-air mixture combusts in a chamber within combustor 16, thereby creating hot pressurized exhaust gases. Combustor 16 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 18 within a turbine casing. The exhaust gases expand through turbine 18 and flow toward an exhaust outlet 20. As the exhaust gases pass through turbine 18, the gases force the rotor blades to rotate a shaft 22. Shaft 22 operably connects turbine 18 to a compressor 24. Shaft 22 defines a center axis of gas turbine 10, including the turbine 18 and compressor 24 thereof. Shaft 22 also is connected to a load 28, 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 22, an axial direction 30 is defined, which represents movement along the center axis, a radial direction 31 is defined, which represents movement toward or away from the center axis, and a circumferential direction 32 is defined, which represents movement around the center axis. Compressor 24 also includes blades coupled to shaft 22. As shaft 22 rotates, the blades within compressor 24 also rotate, thereby compressing air ingested via an air intake 26 as the air moves through compressor 24 and into fuel nozzles 12 and/or combustor 16.
A portion of the compressed air from compressor 24 may be diverted to turbine 18 without passing through combustor 16 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 18 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.
In regard to its general configuration and orientation within the turbine section, inner shroud segment 35 may be described as follows. As indicated in
Positioned as it is about the central axis of turbine 18, the shape and dimensions of inner shroud segment 35 may further be described relative to axial, radial and circumferential directions 30, 31, 32 of turbine 18. Thus, opposed leading and trailing edges 44, 46 are offset in the axial direction 30. As used herein, the distance of this offset in the axial direction 30 is defined as the width dimension (or “width”) of inner shroud segment 35. Additionally, opposed first and second circumferential edges 48, 50 of inner shroud segment 35 are offset in the circumferential direction 32. As used herein, the distance of this offset in the circumferential direction 32 is defined as the length dimension (or “length”) of inner shroud segment 35. Finally, the opposed inner and outboard faces 52, 54 of inner shroud segment 35 are offset in the radial direction 31. As used herein, the distance of this offset in the radial direction 31 is defined as the height dimension (or “height”) of inner shroud segment 35.
With reference now to
With reference now to
As further indicated in
With reference now to
As shown in
As shown in
The decreasing of the cross-sectional flow area through upstream section 66 may be a smooth gradual decrease. The increasing of the cross-sectional flow area through downstream section 67 may be a smooth gradual increase. The manner by which the cross-sectional flow area of crossflow channel 60 decreases or increases may include a narrowing or widening, respectively, of the crossflow channel 60 in one or more dimensional directions 30, 31, 32. According to exemplary embodiments, as shown most clearly in
Though other configurations are possible, crossflow channel 60 of the present disclosure may extend lengthwise along a substantially linear path that is oriented in the circumferential direction 32. That is, the longitudinal axis of crossflow channel 60 approximately aligns with or is parallel to the circumferential direction 32 of the turbine. Thus, according to exemplary embodiments, crossflow channel 60 is oriented within inner shroud segment 35 to extend approximately in the circumferential direction 32, for example, forming an angle between crossflow channel 60 and the circumferential direction 32 that is less than 15°. According to other embodiments, crossflow channel 60 is oriented such that an angle formed between crossflow channel 60 and the circumferential direction 32 is less than 5°. According to exemplary embodiments, crossflow channels 60 within the shroud cooling configuration may have a parallel arrangement, i.e., be arranged parallel with respect to each other. Further, as shown in
Crossflow channel 60 may extend across a majority of the length of inner shroud segment 35. For example, according to exemplary embodiments, crossflow channel 60 extends across at least 60% of the length of inner shroud segment 35. According to other embodiments, crossflow channel 60 extends across at least 75% of the length of inner shroud segment 35. Oriented in this manner shown, the length of crossflow channel 60 is defined as the distance in the circumferential direction 32 between upstream end 61 and downstream end 62. The height of crossflow channel 60 is defined as the distance in the radial direction 31 between an inner radial floor and an outer radial ceiling of crossflow channel 60. As shown in
According to exemplary embodiments, upstream end 61 of crossflow channel 60 is disposed near first circumferential edge 48. For example, upstream end 61 of crossflow channel 60 is disposed no further from first circumferential edge 48 than a distance equal to 20% of the length of inner shroud segment 35. Similarly, downstream end 62 of crossflow channel 60 may be disposed near second circumferential edge 50. For example, downstream end 62 of crossflow channel 60 may be disposed no further from second circumferential edge 50 than a distance equal to 20% of the length of inner shroud segment 35.
According to exemplary embodiments, junction point 65 is located near the middle portion of crossflow channel 60. For example, according to exemplary embodiments, junction point 65 is located within a range of 35% to 65% of the length of crossflow channel 60. According to other embodiments, junction point 65 is located within a range of 45% to 55% of the length of crossflow channel 60. Junction point 65 also may be located at the midpoint of the length of crossflow channel 60.
According to exemplary embodiments, as indicated most clearly in
As further depicted, feed channel 81 may be disposed within one of the circumferential rails 72 while the corresponding outlet channel 82 is disposed within the opposing circumferential rail 72. As will be discussed more below, feed channel 81 may slant in an inboard direction from inlet 91 toward a connection with upstream end 61 of crossflow channel 60. That connection may be near inboard face 54. Feed channel 81 may include a curving path that turns the flow direction of the coolant approximately 180° relative to the circumferential direction 32. Outlet channel 82 may slant in an outboard direction from the connection it makes with downstream end 62 of crossflow channel 60 toward outlet 92.
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
The widening of trough 101 from each of ends 103 may be smooth and gradual. As indicated in
The deepening of trough 101 from each of ends 103 may be smooth and gradual. As shown in
Though other configurations are possible, trough 101 of the present disclosure may be substantially linear and oriented in the circumferential direction 32. That is, the longitudinal axis of trough 101 may approximately align with or be parallel to the circumferential direction 32 of the turbine. Thus, according to exemplary embodiments, trough 101 may be oriented within inner shroud segment 35 to extend approximately in the circumferential direction 32, and, for example, may be arranged parallel to any of the embodiments of crossflow channels 60 discussed above. Each of troughs 101 may be positioned between and extend lengthwise in parallel to the pair of the crossflow channels 60 that flank it. Trough 101 may extend in this way across a majority of the length of inner shroud segment 35. For example, according to exemplary embodiments, trough 101 extends across more than 50% of the length of inner shroud segment 35. According to other embodiments, trough 101 extends across at least 65% of the length of inner shroud segment 35. Multiple, parallel troughs 101 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
For example, feed and outlet channel configurations 121 may be disposed near an edge of inner shroud segment 35—as depicted, first or second circumferential edges 48, 50—and function to supply/remove coolant to/from a pair of adjacent counterflowing crossflow channels 60 (also “paired counterflowing crossflow channels 60”). As will be seen, embodiments of feed and outlet channel configuration 121 provide an efficient way by which paired counterflowing crossflow channels 60 may have coolant delivered thereto and removed therefrom, while also providing enhanced cooling performance.
According to an exemplary embodiment, each crossflow channel 60 may connect to a feed channel 81 at an upstream end 61 and an outlet channel 82 at a downstream end 62, wherein feed channel 81 and outlet channel 82 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 91, and then deliver that coolant to crossflow channel 60 via feed channel 81. Coolant then may pass through crossflow channel 60 and, thereby, cool inboard face 54 of inner shroud segment 35. Once it has passed through crossflow channel 60, then coolant may be directed via outlet channel 82 to outlet 92, whereupon it is expelled from inner shroud segment 35.
In regard to embodiments of feed and outlet channel configurations 121, specific characteristics will now be presented with reference to the illustrated configurations. For example, feed and outlet channel configuration 121 may connect to a pair of adjacent counterflowing crossflow channels 60, which, as already described, may extend side-by-side across inner shroud segment 35. According to preferred embodiments, feed and outlet channel configuration 121 is disposed at each opposing end of such a pair of adjacent counterflowing crossflow channels 60. More generally, feed and outlet channel configuration 121 may be repeated as necessary within inner shroud segment 35 so that it is used with each such pair of counterflowing adjacent crossflow channels 60. For purposes of describing an exemplary feed and outlet channel configuration 121, the pair of corresponding adjacent counterflowing crossflow channels 60 will be referenced as including a first crossflow channel 60, which connects to feed channel 81, and a second crossflow channel 60, which connects to outlet channel 82.
Feed and outlet channel configuration 121 generally includes a feed channel 81 and an adjacent or neighboring outlet channel 82. Both may be disposed near an edge of inner shroud segment 35, for example, first and second circumferential edges 48, 50. Feed channel 81 may extend between an inlet 91 formed on an exterior surface of inner shroud segment 35 and a connection made with the first crossflow channel 60 of the paired crossflow channels 60. According to preferred embodiments, inlet 91 may be formed through outboard face 52 of inner shroud segment 35 so that inlet 91 fluidly communicates with cavity 37 and/or outboard cavity 71 of inner shroud segment 35. For example, inlet 91 may be formed on inward side 75 of circumferential rail 72 of first circumferential edge 48. As another example, when feed and outlet channel configuration 121 occurs on the opposite side of inner shroud segment 35, inlet 91 may be formed on inward side 75 of circumferential rail 72 of second circumferential edge 50. In regard to outlet channel 82, it may extend between a connection made with the second crossflow channel 60 of paired crossflow channels and an outlet 92 formed on an exterior surface of inner shroud segment 35. For example, outlet 92 may be formed on first circumferential edge 48. When feed and outlet channel configuration 121 occurs on the opposite side of inner shroud segment 35, outlet 92 may be formed on second circumferential edge 50.
In accordance with example embodiments, certain configurational attributes of feed and outlet channel configuration 121 will now be described. For purposes of description, the shape of feed and outlet channels 81, 82 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 81 and outlet channels 82 are shaped in the axial and circumferential directions 30, 32. 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 81 initially slants in an inboard direction from a radially elevated initial position at inlet 91 to the approximate radial level of floor 74 or crossflow channels 60, which may be near inboard face 54. From the outboard perspective, this first slanting section may be substantially linear and aligned with the circumferential direction 32. From the outboard perspective, feed channel 81 may continue via a curving or looping second section that turns the flow of coolant approximately 180° before feed channel 81 connects with upstream end 61 of first crossflow channel 60. Thus, while the initial flow direction in feed channel 81 is directed toward first circumferential edge 48, at the connection that feed channel 81 makes with first crossflow channel 60, the flow direction is circumferentially reversed so that the flow of coolant is now being directed toward second circumferential edge 50. From the outboard perspective, in making this 180° turn, the curvature of feed channel 81 bows outward toward outlet channel 82. From the outboard perspective, this second or bowed section 123 is configured to undercut a section of outlet channel 82. More specifically, again, from the outboard perspective, bowed section 123 of feed channel 81 axially and circumferentially overlaps a section of outlet channel 82, while being radially offset therefrom in the inboard direction.
From the outboard perspective, upstream end 61 of first crossflow channel 60 may be positioned to overlap axially with inlet 91, while being radially offset therefrom in the inboard direction. Thus, from the outboard perspective, as shown most clearly in
According to preferred embodiments, a first section of outlet channel 82 may slant in an outboard direction from the connection outlet channel 82 makes with downstream end 62 of crossflow channel 60. More specifically, as shown most clearly in
As a further feature, inward side 75 of circumferential rail 72 may include a corrugated configuration 130 with alternating ridges 131 and valleys 133, which, as will be seen, may be configured to correspond to the placement of feed and outlet channels 81, 82 with feed and outlet channel configurations 121. Generally, ridges 131 and valleys 133 may extend in the circumferential direction and slant in the outboard direction along a contour of inward side 75 of circumferential rail 72. As shown most clearly in
The advantages of corrugated configuration 130 include the removal of excess material while maintaining the structural robustness of the component. Further, corrugated configuration 130 provides benefits related to enabling or enhancing aspects of feed and outlet channel configuration 121. For example, ridge 131 enables outboard slanting section 125 of outlet channels 82 to extend circumferentially at a steeper angle, which produces the space to the inboard side of it for feed channel 81 to curl under it in the manner discussed above. As another example, valleys 133 enable the positioning of inlet 91 at a lower radial height, which also facilitates feed channel 81 curling under outlet channel 82 in the desired manner. Further, the lower radial height of inlet 91 results in a shorter length of feed channel 81, which decreases aerodynamic losses.
With reference now to
It has been found that truss structure 151 at axial rail 73 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 151 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 60° 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 45° 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 35 disclosed herein are configured so that typical build directions result in maximum overhang angles of approximately 60° or, according to other alternatives, maximum overhang angles of approximately 45°. 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 101 given the ranges provided herein for first and second angles 108, 109 would result in a shallow overhang angles of less than less 60° and/or 45°. 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 153 of truss structure 151 given the ranges provided herein for angle 157 would result in a shallow overhang angles of less than less 60° and/or less than 45°.
As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present disclosure. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, each of the possible iterations is not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.
