Patent Application
20130115060
The subject matter disclosed herein relates generally to turbine systems, and more specifically to bucket assemblies for turbine systems.
Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor, a combustor, and a turbine. During operation of the gas turbine system, various components in the system are subjected to high temperature flows, which can cause the components to fail. Since higher temperature flows generally result in increased performance, efficiency, and power output of the gas turbine system, the components that are subjected to high temperature flows must be cooled to allow the gas turbine system to operate at increased temperatures.
Various strategies are known in the art for cooling various gas turbine system components. For example, a cooling medium may be routed from the compressor and provided to various components. In the compressor and turbine sections of the system, the cooling medium may be utilized to cool various compressor and turbine components.
Buckets are one example of a hot gas path component that must be cooled. For example, various parts of the bucket, such as the airfoil, the platform, the shank, and the dovetail, are disposed in a hot gas path and exposed to relatively high temperatures, and thus require cooling. Various cooling passages and cooling circuits may be defined in the various parts of the bucket, and cooling medium may be flowed through the various cooling passages and cooling circuits to cool the bucket.
One specific component of a bucket that requires cooling is the platform. Thus, a platform cooling circuit is provided in many know buckets. A typical platform cooling circuit includes an inlet portion that extends from the platform to the shank of the bucket in a curvilinear fashion. Specifically, a curvilinear portion of the inlet portion is typically located near an exterior intersection between the platform and shank. Thus, during operation of the bucket, when the platform and shank are subjected to differing temperatures, this temperature differential may create significant bending stresses at the curvilinear portion of the inlet portion. These stresses can lead to a low thermal fatigue life, and thus require frequent repair or replacement of buckets.
Accordingly, an improved bucket assembly for a turbine system is desired in the art. Specifically, a bucket assembly with an improved platform cooling circuit would be advantageous.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, a bucket assembly for a turbine system is disclosed. The bucket assembly includes a main body having an exterior surface and defining a main cooling circuit, and a platform surrounding the main body and at least partially defining a platform cooling circuit. The platform includes a forward portion and an aft portion each extending between a pressure side slash face and a suction side slash face and further includes a forward face, an aft face, and a top face. The platform cooling circuit includes an upper surface and a lower surface. The bucket assembly further includes a passage extending between and providing fluid communication between the main cooling circuit and the platform cooling circuit. An end opening of the passage is defined in the lower surface of the platform cooling circuit.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. 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 various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with 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.
The turbine 16 may include a plurality of turbine stages. For example, in one embodiment, the turbine 16 may have three stages. A first stage of the turbine 16 may include a plurality of circumferentially spaced nozzles and buckets. The nozzles may be disposed and fixed circumferentially about the shaft 18. The buckets may be disposed circumferentially about the shaft and coupled to the shaft 18. A second stage of the turbine 16 may include a plurality of circumferentially spaced nozzles and buckets. The nozzles may be disposed and fixed circumferentially about the shaft 18. The buckets may be disposed circumferentially about the shaft 18 and coupled to the shaft 18. A third stage of the turbine 16 may include a plurality of circumferentially spaced nozzles and buckets. The nozzles may be disposed and fixed circumferentially about the shaft 18. The buckets may be disposed circumferentially about the shaft 18 and coupled to the shaft 18. The various stages of the turbine 16 may be at least partially disposed in the turbine 16 in, and may at least partially define, a hot gas path (not shown). It should be understood that the turbine 16 is not limited to three stages, but rather that any number of stages are within the scope and spirit of the present disclosure.
Similarly, the compressor 12 may include a plurality of compressor stages (not shown). Each of the compressor 12 stages may include a plurality of circumferentially spaced nozzles and buckets.
One or more of the buckets in the turbine 16 and/or the compressor 12 may comprise a bucket assembly 30, as shown in
In general, the main body 32 has an exterior surface. In embodiments wherein the main body 32 includes an airfoil 36 and shank 38, for example, the portion of the exterior surface defining the airfoil 36 may have a generally aerodynamic contour. For example, the airfoil 32 may have an exterior surface defining a pressure side 42 and suction side 44 each extending between a leading edge 46 and a trailing edge 48. Further, the portion of the exterior surface of the shank 38 may include a pressure side face 52, a suction side face 54, a leading edge face 56, and a trailing edge face 58.
The platform 34 may generally surround the main body 32, as shown. A typical platform may be positioned at an intersection or transition between the airfoil 36 and shank 38 of the main body 32, and extend outwardly in the generally axial and tangential directions. It should be understood, however, that a platform according to the present disclosure may have any suitable position relative to the main body 32 of the bucket assembly 30.
A platform 34 according to the present disclosure may include a forward portion 62 and an aft portion 64. The forward portion 62 is that portion of the platform 34 positioned proximate the leading edge 46 of the airfoil 36 and the leading edge face 56 of the shank 38, while the aft portion 64 is that portion of the platform 34 positioned proximate the trailing edge 48 of the airfoil 36 and the trailing edge 58 of the shank 36. The forward portion 62 and the aft portion 64 may further define a top face 66 of the platform 34, which may generally surround the airfoil 36 as shown. Further, a peripheral edge may surround the forward portion 62, aft portion 64, and top face 66. The peripheral edge may include a pressure side slash face 72 and suction side slash face 74, which each of the forward portion 62 and the aft portion 64 may extend between. The peripheral edge may further include a forward face 76, which may define a peripheral edge of the forward portion 62, and an aft face 78, which may define a peripheral edge of the aft portion 64.
As shown in
As further shown in
In many bucket assemblies 30, a platform cooling circuit 90 is in fluid communication with a main cooling circuit, such that cooling medium is flowed from a main cooling circuit into the platform cooling circuit 90 and/or is flowed from a platform cooling circuit 90 to a main cooling circuit. For example, in the embodiment shown in
A platform cooling circuit 90, or any portion thereof, may have any suitable path through the platform 34. For example, the platform cooling circuit 90 or any portion thereof may be generally linear or generally curvilinear. In some exemplary embodiments, the platform cooling circuit 90, such as the intermediate portion 94 thereof, may have a generally serpentine path, as shown. Such serpentine path may include alternating generally linear and generally curvilinear portions, such that cooling medium may flow back and forth through such portions as it flows through the platform cooling circuit 90. It should be understood, however, that a platform cooling circuit 90 according to the present disclosure may have any suitable path through the platform 34.
A platform cooling circuit 90 according to the present disclosure may further include an upper surface 102 and a lower surface 104. In some embodiments, such as wherein the platform cooling circuit 90, or any portion thereof, has a oval or circular cross-section, the upper surface 102 and lower surface 104 may be generally curvilinear, and may meet to fully define the platform cooling circuit 90. In other embodiments, a platform cooling circuit 90 may further include one or more sidewalls (not shown). Each sidewall may extend between an upper surface 102 and a lower surface 104. Upper surfaces 102 and lower surfaces 104 according to the present disclosure may have any suitable shape and size. For example, an upper surface 102 and/or lower surface may be planer, may be curvilinear as discussed, or may include suitable bends or other disruptions. An upper surface 102 and lower surface 104, along with optional sidewalls, may define any suitable cross-sectional profile for a platform cooling circuit, such as rectangular, oval, triangular, or any other suitable polygonal shape.
A bucket assembly 30 according to the present disclosure may further advantageously include one or more passages 110, as shown in
As shown, a passage 110 according to the present disclosure further includes end openings 112. The end openings 112 act as the inlet and outlet for the passage 110 for flow to and from the main cooling circuit and platform cooling circuit 90. Advantageously, an end opening 112 of the passage 110, such as the end opening 112 for flowing cooling medium between the passage 110 and platform cooling circuit 90, is defined in the lower surface 104 of the platform cooling circuit 90. In exemplary embodiments as shown, such end opening 112 is an outlet, such that cooling medium flows through the end opening 112 into the platform cooling circuit 90 from the passage 110. Such design of the passage 110 and platform cooling circuit 90 may advantageously reduce stresses at the intersection between the platform cooling circuit 90 and passage 110. For example, by designing the passage 110 and platform cooling circuit 90 such that an end opening 112 of the passage 110 is defined in the lower surface 104 of the platform cooling circuit 90, the intersection between the passage 110 and platform cooling circuit 90 may be spaced from the exterior intersection between the platform 34 and shank 38. Thus, during operation of the turbine system 10 when the platform 34 and shank 38 are subjected to different temperatures, resulting bending stresses at the intersection of the passage 110 and platform cooling circuit 90 may be reduced or eliminated.
In some embodiments, as shown, at least a portion of a passage 110 may extend in a generally radial direction. The radial direction is the direction between the root 40 and airfoil 36 of the bucket assembly, and may be shown as a vertical direction in
As discussed above and shown in
The arrows shown in
In some embodiments as shown, a bucket assembly 30 according to the present disclosure may further include one or more exhaust passages 120. Each exhaust passage 120 may be defined in the platform 34, such as in the aft portion 64 of the platform 34 and/or in the forward portion 62 of the platform 34, and may be in fluid communication with the platform cooling circuit 90. For example, an exhaust passage 120 may be in fluid communication with a forward portion 92, intermediate portion 94, outlet portion 96, and/or any other suitable portion of a platform cooling circuit 90. Thus, cooling medium flowing through the platform cooling circuit 90 may flow from the platform cooling circuit 90 into an exhaust passage 120.
Each exhaust passage 120 may further include an outlet 122. The outlet 122 may be defined in any suitable location on the platform 34, such as on the aft portion 64 and/or forward portion 62 of the platform 34. For example, an outlet 122 may be defined in the top face 66 as shown, or in the suction side slash face 74, or in the pressure side slash face 72 as shown, or in the forward face 76, aft face 78, or any other suitable location on the platform 34, such as on the aft portion 64 and/or forward portion 62 of the platform 34. Cooling medium flowed through an exhaust passage 120 may thus be exhausted through the outlet 122 of that exhaust passage 120. Additionally, in some embodiments, such exhausted cooling medium may further advantageously act as a cooling film to cool the exterior of the platform 34.
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.
