Patent Application
20130034445
The subject matter disclosed herein relates to a turbine bucket and related turbines. Specifically, the subject matter disclosed herein relates to a turbine bucket base (or, shank) including a semi-elliptical channel configured to provide axial fluid flow of a cooling fluid through a turbine.
Some power plant systems, for example certain nuclear, simple cycle and combined cycle power plant systems, employ turbines to drive generators and generate electricity. Some of these turbines (e.g., steam turbines) are driven by a flow of high temperature steam which is directed through sets of stationary nozzles (or, vanes) and across the face of turbine blades, forcing rotation of those blades along with the turbine rotor. This high temperature steam can negatively affect certain components in the turbine, such as a drum rotor. Prolonged exposure of the drum rotor to high-temperature steam may result in inefficient operation, corrosion, system damage, and a need for rotor repairs and/or rotor replacement.
Some systems attempt to counteract the aforementioned affects caused by high-temperature steam by forming the turbine rotor of more resilient materials. However, introducing these more resilient materials into the turbine rotor formation may increase overall costs. Additionally, these materials may add complexity to the turbine design and manufacturing process.
A turbine bucket and corresponding turbines are disclosed herein. In one aspect, the turbine bucket includes: a blade member; and a base member affixed to the blade member, the base member configured to attach to a turbine rotor radially inward of the blade member, wherein the base member includes a first semi-elliptical groove spanning substantially an axial length of the base member.
A first aspect of the invention includes a turbine bucket having: a blade member; and a base member affixed to the blade member, the base member configured to attach to a turbine rotor radially inward of the blade member, wherein the base member includes a first semi-elliptical groove spanning substantially an axial length of the base member.
A second aspect of the invention includes a turbine having: a stator; a diaphragm at least partially housed within the stator; and a rotor substantially surrounded by the diaphragm, the rotor including: a turbine bucket having: a blade member; and a base member affixed to the blade member, the base member attached to the rotor radially inward of the blade member, wherein the base member includes a first semi-elliptical groove spanning substantially an axial length of the base member.
A third aspect of the invention includes a turbine having: a stator including a cooling path extending therethrough; and a rotor substantially surrounded by the stator and fluidly connected with the cooling path, the rotor including: a plurality of turbine buckets, each of the plurality of turbine buckets having: a blade member; and a base member affixed to the blade member, the base member attached to the rotor radially inward of the blade member, wherein the base member includes a pressure-side semi-elliptical groove spanning substantially an axial length of the base member, the pressure-side semi-elliptical groove interacting with a suction-side semi-elliptical groove in an adjacent one of the plurality of turbine buckets to form a fluid conduit extending axially along the blade member.
These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
It is noted that the drawings of the invention are not necessarily to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
Aspects of the invention provide for a turbine bucket. Specifically, aspects of the invention disclosed herein relate to a turbine bucket base (or, shank) having a semi-elliptical channel configured to provide axial fluid flow of a cooling fluid through a turbine.
As noted herein, some turbine designers have attempted to counteract the detrimental affects caused by high-temperature steam on turbine rotor components by forming the turbine rotor of more resilient materials. However, introducing these more resilient materials into the turbine rotor formation may increase overall costs. Additionally, these materials may add complexity to the turbine design and manufacturing process.
In contrast to conventional approaches, aspects of the invention involve introducing a cooling circuit including an axial fluid flow passage in a turbine to allow for cooling of turbine components (e.g., rotor components). In particular, aspects of the invention include a turbine bucket having a semi-elliptical groove configured to allow for axial fluid flow of a cooling fluid through portions of a turbine rotor in order to cool the rotor (e.g., the drum).
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In an alternative embodiment, a groove may be formed in the base member 6 of a distinct shape from the semi-elliptical design shown. For example, designs employing angles (e.g., partial hexagonal, octagonal, diamond-shaped, etc.) may also be used to form a portion of an axially-extending channel as described herein. It is understood that these alternative embodiments will likely involve increased stress forces proximate the grooves, as the ellipse configuration is designed to bear greater stress. In any case, the design of base member 6 may be configured to interact with a complementary base member 6 having a groove structure configured to at least partially form an axially extending cooling channel.
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In some embodiment, the first semi-elliptical groove 10 (and in some cases, the second semi-elliptical groove 14) may be formed of a substantially identical composition as the remainder of the base member 6. For example, in some cases, both the base member 6 and the grooves 10, 14 may be formed substantially of steel, e.g., martensitic stainless steel. It is understood that some aspects of the invention may allow for the use of relatively lower-cost materials when compared with conventional rotor base members, as the base members (e.g., base member 6) shown and described herein experience increased cooling due to their grooved design, when compared with conventional rotor base members. In some embodiments, the base member 6 and grooves 10, 14 may be integrally fabricated. In one case, the base member 6 and the grooves 10, 14 may be integrally cast or forged. In another case, the base member 6 and the grooves 10, 14 may be machined (e.g., cut) from one or more adjoined pieces of material (e.g., steel). It is understood that additional embodiments are also possible in view of the various aspects of the invention described herein, and that in some cases portions of the grooves 10, 14 (e.g., segment 12 and a corresponding segment on groove 14) may be formed separately from the base member 6 and later adjoined (e.g., via welding, brazing, etc.).
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The cooling path 36 may extend from an inlet 38 in the turbine 20, to a portion of the rotor 32, whereby it passes radially inward of the blade members 4. The cooling path 36 may be partially defined in part by members (indicated by letters “E” and “F”) extending axially from axially facing sides of the base member 6 and/or nozzle stages 26 (at a diaphragm ring segment). The cooling path 36 may be further defined, according to aspects of the invention, by the semi-elliptical grooves 10 spanning an axial length of the base members 6. This portion of the cooling path 36 is indicated in areas by the letter “G”, which corresponds to portions of the cooling path 36 extending between openings in circumferentially adjacent base members 6 (arranged in stages 30). As described herein, use of these semi-elliptical grooves 10 may substantially fluidly seal the blade members 4 from the cooling circuit 36. That is, the semi-elliptical grooves 10 may substantially fluidly isolate working portions of the turbine (e.g., those areas where the working fluid flows therethrough) from the cooling path 36. These semi-elliptical grooves 10 may aid in providing an effective cooling path 36, thereby maintaining a desired temperature of the rotor 32. In some cases, the cooling fluid (e.g., steam) passing through the cooling path 36 may have a temperature of at least approximately 200 degrees Fahrenheit less than the temperature of the working fluid. It is understood that as the cooling fluid travels axially through the turbine, its temperature will increase, and may approach the temperature of the working fluid.
It is understood that aspects of the invention provide for configurations of a portion of a cooling circuit through a turbine rotor (e.g., a rotor drum). The teachings described herein may be combined with other teachings (e.g., the use of axially extending members from axially facing portions of base member 6) to complete an effective cooling path 36 which isolates the working fluid of the turbine from the cooling fluid. As noted, in some embodiments, the “grooves” described herein may be formed of a variety of shapes sufficient to substantially fluidly isolate portions of the cooling path (e.g., cooling path 36) from the blade members (e.g., blade member 4). Use of the cooling path(s) described herein may allow for construction of a turbine (e.g., turbine 20) using less heat-resistant materials, when compared with some conventional turbines.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
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 have 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.
