Patent Application
20170159494
The subject matter disclosed herein relates to steam turbines. Specifically, the subject matter disclosed herein relates to nozzle segments in steam turbines. Steam turbines include static nozzle assemblies that direct flow of a working fluid into turbine buckets connected to a rotating rotor. The nozzle construction (including a plurality of nozzles, or “airfoils”) is sometimes referred to as a “diaphragm” or “nozzle assembly stage.” Steam turbine diaphragms include two halves, which are assembled around the rotor, creating horizontal joints between these two halves. Each turbine diaphragm stage is vertically supported by support bars, support lugs or support screws on each side of the diaphragm at the respective horizontal joints. The horizontal joints of the diaphragm also correspond to horizontal joints of the turbine casing, which surrounds the steam turbine diaphragm.
Current approaches for welding airfoils to nozzle rings (or, sidewalls) have shortcomings. Specifically, large stage diaphragms, such as those found in the low pressure section of a steam turbine (with airfoil lengths typically greater than ˜45 centimeters (˜18 inches)) pose welding issues. For example, these welds are prone to cracking, and can be labor intensive to form. Additionally, conventional welding approaches often involve a post-weld heat treatment. Even further, welding causes distortion in the steam flow path, which can negatively impact performance. Approaches to work around the weld configurations (e.g., integrated sidewall-airfoil designs) have been lacking in that they require additional components and fabrication in order to effectively cover the forward flow path.
Various embodiments include a steam turbine diaphragm nozzle segment, related assembly and steam turbine. Particular embodiments include a steam turbine diaphragm nozzle segment having: an airfoil having a contact surface for directing a flow of working fluid through a flow path; and a sidewall coupled with the airfoil and at least partially radially outboard of the airfoil, the sidewall having: a body contacting the airfoil; an axially upstream-extending hook extending axially from the body; a first notch adjacent the axially upstream-extending hook; an axially downstream-extending hook extending axially from the body; and a second notch adjacent the axially downstream-extending hook.
A first aspect of the disclosure includes a steam turbine diaphragm nozzle segment having: an airfoil having a contact surface for directing a flow of working fluid through a flow path; and a sidewall coupled with the airfoil and at least partially radially outboard of the airfoil, the sidewall having: a body contacting the airfoil; an axially upstream-extending hook extending axially from the body; a first notch adjacent the axially upstream-extending hook; an axially downstream-extending hook extending axially from the body; and a second notch adjacent the axially downstream-extending hook.
A second aspect of the disclosure includes a steam turbine diaphragm segment having: an outer ring; an inner ring within the outer ring; and at least one diaphragm nozzle segment coupled to the inner ring and the outer ring, the at least one diaphragm nozzle segment having: an airfoil with a contact surface for directing a flow of working fluid through a flow path; a first sidewall coupled with the airfoil and at least partially radially outboard of the airfoil, the first sidewall coupled with the outer ring, wherein the first sidewall includes: a body contacting the airfoil; an axially upstream-extending hook extending axially from the body; a first notch adjacent the axially upstream-extending hook; an axially downstream-extending hook extending axially from the body; and a second notch adjacent the axially downstream-extending hook; and a second sidewall coupling the airfoil with the inner ring.
A third aspect of the disclosure includes a steam turbine having: a rotor; a turbine casing at least partially surrounding the rotor; and a diaphragm segment between the turbine casing and the rotor, the diaphragm segment having: an outer ring; an inner ring within the outer ring; and at least one diaphragm nozzle segment coupled to the inner ring and the outer ring, the at least one diaphragm nozzle segment having: an airfoil with a contact surface for directing a flow of working fluid through a flow path; a first sidewall coupled with the airfoil and at least partially radially outboard of the airfoil, the first sidewall coupled with the outer ring, wherein the first sidewall includes: a body contacting the airfoil; an axially upstream-extending hook extending axially from the body; a first notch adjacent the axially upstream-extending hook; an axially downstream-extending hook extending axially from the body; and a second notch adjacent the axially downstream-extending hook; and a second sidewall coupling the airfoil with the inner ring.
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 disclosure, 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.
The subject matter disclosed herein relates to steam turbines. Specifically, the subject matter disclosed herein relates to nozzle segments in steam turbines.
According to various embodiments of the disclosure, a steam turbine nozzle segment includes an airfoil and a sidewall coupled (e.g., integral in some cases) with the airfoil, where the sidewall includes an axially upstream-extending (forward) hook and a first notch (also referred to as a first groove) adjacent the axially forward-extending hook, as well as an axially downstream-extending (aft) hook and a second notch adjacent the axially downstream-extending hook. The forward hook is sized to engage a first slot in a nozzle cover, and the aft hook is sized to engage a second slot in the turbine's diaphragm ring. In various embodiments, the nozzle cover is a separate component connected to the outer ring, which can be coupled and decoupled with the outer ring, e.g., to enhance the ability to access the nozzle segment. However, in other cases, the nozzle cover is an integral component with the outer ring (e.g., they are formed of a piece of common material such as low carbon or alloy steel). In various embodiments, the sidewall further includes an axially upstream-extending (forward) flange extending substantially an entirety of the axial length of the forward flow path (between airfoil and next stage nozzle). Some embodiments include a lug member coupling the nozzle segment to the turbine diaphragm ring, e.g., to prevent rotation of the nozzle segment relative to that ring.
As denoted in these Figures, the “A” axis represents axial orientation (along the axis of the turbine rotor, omitted for clarity). As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially parallel with the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference (c) which surrounds axis A but does not intersect the axis A at any location. Identically labeled elements in the Figures depict substantially similar (e.g., identical) components.
Turning to
In various embodiments, as shown in the schematic depiction in
In some other embodiments, as shown in the diaphragm segment 90 of
In another embodiment, as shown in the diaphragm segment 100 of
In yet further embodiments, as shown in the diaphragm segment 110 of
As noted herein, when compared with conventional diaphragm segments, assemblies and steam turbines, various aspects of the disclosure can provide for improved manufacturability, maintenance and replacement of parts. In some cases, the nozzle segments (e.g., nozzle segments 20, 50, etc.) disclosed herein can allow for relatively shorter turn-around time in replacing nozzle components (e.g., nozzle segments 20, 50, etc.), as conventional weld joints are replaced by complementary hook mechanisms. Further, the addition of forward flange 52 shown and described herein can provide enhanced performance when compared with conventional assemblies, as forward flange 52 can help to seal the flow path 26 and reduce steam leakage (and prevent unwanted steam flow disruption). The embodiments disclosed herein can reduce time spent in installation, maintenance and/or replacement of parts, which further reduces costs and enhances the efficiency of steam turbines employing these embodiments.
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.
