STRESS MITIGATING ARRANGEMENT FOR WORKING FLUID DAM

IN TURBINE SYSTEM

BACKGROUND

[0001] The disclosure relates generally to turbine systems, and more particularly, to a stress mitigating arrangement for a working fluid dam in a turbine system.

[0002] Turbine systems are used widely to generate power. One common form of turbine system is a steam turbine system. Many steam turbine (ST) systems include a number of sequential turbines that handle different pressure steam, e.g., a high pressure (HP) turbine, an intermediate pressure (IP) turbine and a low pressure (LP) turbine. In one approach the HP-IP steam turbines are arranged in a casing with an opposed flow configuration because it is most cost efficient compared to a system including separate HP and IP steam turbine casings. The HP steam turbine and the IP steam turbine can be provided together in a casing that includes two, coupled casing half-shells. Steam may be delivered to such a system using ‘close coupled’ or casing mounted valves, which are more cost-efficient because they eliminate expensive connecting piping. In this setting, valves are directly mounted to the outer casing such that steam is directed tangentially into the casing from opposed sides of the casing. A steam dam is provided between the inlets in the casing in the HP or IP steam turbine to direct the steam axially into the HP or IP steam turbine and prevent flow oscillations. Typically, the steam dam is cast into the casing. One challenge with this approach is that the added material can create a high local stress that requires additional maintenance, and thus can reduce the availability of the steam turbines.

BRIEF DESCRIPTION

[0003] A first aspect of the disclosure provides a casing half shell for a turbine system, the casing half shell comprising: a body having an open interior for enclosing parts of the turbine system; a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction; a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction; and a working fluid dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path, the working fluid dam including a stress-mitigating slot extending radially therein.

[0004] A second aspect of the disclosure provides a steam turbine (ST) system, the ST system comprising: at least one of a high pressure (HP) turbine and an intermediate pressure (IP) turbine; a casing including a body having an open interior for enclosing the at least one of the HP steam turbine and the IP steam turbine; a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction; a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction; and a steam dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path to redirect the first and second working fluid flows to the at least one of the HP steam turbine and the IP steam turbine, the steam dam including a stress-mitigating slot extending radially therein; and a fill member mounted in the stress-mitigating slot.

[0005] A third aspect of the disclosure provides a method, comprising: providing a casing half shell for a turbine system, the casing half shell including a body having open interior, a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction, a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction, and a working fluid dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path; forming a stress-mitigating slot extending

radially in the working fluid dam; and fixedly coupling a fill member in the stress-mitigating slot.

[0006] The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:

[0008] FIG. 1 shows a schematic cross-sectional view of an illustrative turbine system in the form of a high pressure-intermediate pressure (HP-IP) steam turbine (ST) system.

[0009] FIG. 2 shows a perspective view of an illustrative casing for the HP-IP ST system of FIG. 1.

[0010] FIG. 3 A shows a perspective view of an illustrative lower casing half-shell according to embodiments of the disclosure.

[0011] FIG. 3B shows a perspective view of an illustrative upper casing half-shell according to embodiments of the disclosure.

[0012] FIG. 4 shows a cross-sectional view of a conventional working fluid dam.

[0013] FIG. 5 shows a cross-sectional perspective view of a working fluid dam with a stress-mitigating slot and an optional fill member therein, according to embodiments of the disclosure.

[0014] FIG. 6 shows a cross-sectional perspective view of a working fluid dam including a stress-mitigating slot therein, according to embodiments of the disclosure.

[0015] FIG. 7 shows an enlarged cross-sectional perspective view of the working fluid dam and optional fill member of FIG. 5, according to embodiments of the disclosure.

[0016] FIG. 8 shows a cross-sectional perspective view of a working fluid dam including an axially angled stress-mitigating slot therein, according to embodiments of the disclosure.

[0017] FIG. 9 shows a cross-sectional perspective view of a working fluid dam including a stress-mitigating slot therein, according to embodiments of the disclosure.

[0018] FIG. 10 shows a schematic cross-sectional view of a working fluid dam including a stress-mitigating slot therein, according to other embodiments of the disclosure.

[0019] FIG. 11 shows a schematic cross-sectional view of a working fluid dam including a stress-mitigating slot therein, according to yet other embodiments of the disclosure.

[0020] FIG. 12 shows a schematic cross-sectional view of a working fluid dam including a stress-mitigating slot therein, according to additional embodiments of the disclosure.

[0021] It is noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

[0022] As an initial matter, in order to clearly describe the current disclosure it will become necessary to select certain terminology when referring to and describing relevant machine components within a turbine system. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning.

Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.

[0023] In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. These terms and their definitions, unless stated otherwise, are as follows. As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of a fluid, such as the working fluid through the turbine system or, for example, the flow of air through the combustor or coolant through one of the turbine's component systems. The term “downstream” corresponds to the direction of flow of the fluid, and the term “upstream” refers to the direction opposite to the flow. It is recognized that in an opposed flow configuration, upstream and downstream directions may change depending on where one is in the turbine system. The terms “forward” and “aft,” without any further specificity, refer to directions, with “forward” referring to the front end of the turbine system, and “aft” referring to the rearward of the turbine system. It is often required to describe parts that are at differing radial positions with regard to a center axis. The term “radial” refers to movement or position perpendicular to an axis. In cases such as this, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is “radially inward” or “inboard” of the second component. If, on the other hand, 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. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. It will be appreciated that such terms may be applied in relation to the center axis of the turbine system, e.g., an axis of a rotor thereof.

[0024] In addition, several descriptive terms may be used regularly herein, as described below. The terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual

components.

[0025] 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. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0026] Where an element or layer is referred to as being “on,” “engaged to,” “disengaged from,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[0027] As indicated above, the disclosure provides a casing half shell for a turbine system such as a steam turbine (ST) system, and a related method. The ST system may include, for example, at least one of a high pressure (HP) steam turbine and an intermediate pressure (IP) steam turbine. For purposes of description only, the ST system is illustrated as a high pressure-intermediate pressure (HP -IP) steam turbine (ST) system. The casing half shell can be used in, for example, an HP ST system, an IP ST system, and/or an HP-IP ST system. In any event, the casing half shell includes a body having an open interior for enclosing parts of the turbine system. Where the casing half shell is, for example, a lower half shell casing, it may also include a first inlet in the body for delivering a first working fluid flow into the open interior in a first direction; and a second inlet in the body for delivering a second working fluid flow into the open interior in a second direction that is opposed to the first direction. Alternatively, when the casing half shell is an upper casing half shell, it may be devoid of the inlets. In any event, a working fluid dam extends radially and axially in the body at a location where tangentially opposing working fluid flow paths meet. In a lower casing half shell, the location may be between the first inlet and the second inlet. In contrast to conventional working fluid dams, the working fluid dam includes a stress-mitigating slot extending radially therein. The slot reduces stress in a high stress-prone area that may form in the dam and forces stresses radially outward in the casing half shell to either maintain current stress or relieve the high stress from the working fluid dam. A fill member may be mounted in the stress-mitigating slot to otherwise provide full functioning of the working fluid dam.

[0028] FIG. 1 shows a cross-sectional schematic view of an illustrative turbine system 100 in the form of a high pressure and intermediate pressure (HP-IP) steam turbine (ST) system 102. While the disclosure will be described as applied to HP-IP ST system 102, the teachings of the disclosure may be applicable to other forms of ST systems such as an HP steam turbine system or an IP steam turbine system. The teachings of the disclosure are also applicable to turbine systems 100 in which a working fluid other than steam reacts in the casing in opposing tangential directions, e.g., gas turbines, jet engines, low pressure steam turbines, compressors, etc. The example shows a double casing half-shell, opposed flow configuration. In this setting, HP-IP ST system 102 may include a high pressure (HP) steam turbine 106 and an intermediate pressure (IP) steam turbine 104. HP-IP system 102 also includes a casing 110 having an open

interior 114 for enclosing HP steam turbine 106 and IP steam turbine 104. More particularly, casing 110 may include a pair of casing half shells 120, 122 that are coupled together to collectively form open interior 114. A lower casing half shell 122 may include body 112, and upper casing half shell 120 may include body 113. Here, body 112, 113 may have a generally semi-circular shape. Casing half shells 120, 122 are fastened together using any now known or later developed system, e.g., bolts. A seam between casing half shells 120, 122 is hidden behind rotor 124 in FIG. 1, but is shown in the perspective view of FIG. 2. Casing half shell 122 (and 120) for a turbine system, e.g., HP-IP ST system 100, may be provided in any now known or later developed fashion, e.g., via casting and related finishing processes.

[0029] A variety of thrust bearings and journal bearings 126 may support rotor 124. Rotor 124 has an axis A. Each turbine 104, 106 includes a plurality of axially spaced rotor wheels 128 to which a plurality of rotating blades 130 are mechanically coupled. More specifically, blades 130 are arranged in rows that extend circumferentially around each rotor wheel 128. A plurality of stationary vanes (not shown for clarity) extend circumferentially around rotor 124, and the vanes are axially positioned between adjacent rows of blades 130. The stationary vanes cooperate with blades 130 to form a stage and to define a portion of a steam flow path through each turbine 104, 106. HP steam turbine 106 may have smaller blades than IP steam turbine 104. It is recognized that where HP and IP systems are separate, separate casings 110 may be used.

[0030] Embodiments of the disclosure will be described and illustrated mainly relative to an IP steam turbine 104 section of HP-IP ST system 102. It is emphasized that the teachings of the disclosure equally applicable to HP steam turbine 106 section of HP-IP ST system 102, and to upper or lower casing half shell portions thereof.

[0031] FIG. 2 shows a bottom perspective view of casing 110; FIG. 3 A shows a top, perspective view of lower casing half shell 122 (with upper casing half shell 120 (FIGS. 1-2) removed); and FIG. 3B shows a top, perspective view of upper casing half shell 120 (flipped over with lower casing half shell 122 (FIGS. 1-2) removed). FIGS. 3A-B show a portion of open interior 114 including a space 134 for IP steam turbine 104 (FIG. 1) and a space 136 for HP steam turbine 106 (FIGS. 1-2). Spaces 134, 136 are separated by a packing head (not shown) mounted to a packing head main fit 138. A casing flow guide 137 may extend axially from packing head main fit 138. Spaces 134, 136 may include any form of diaphragm mounting elements 139 for receiving diaphragms (not shown) that extend about outer ends of rotating blades 130 (FIG. 1). Each casing half shell 120, 122 includes similar, mating diaphragm mounting elements 139.

[0032] With reference to FIGS. 2, 3A and 3B, relative to, for example, space 134 for IP steam turbine 104 (FIGS. 1-2), each casing half shell 122, 120 includes a first working fluid flow path 140 in body 112, 113 for directing a first working fluid flow 142, e.g., steam, in open interior 114 in a first direction FD, and a second working fluid flow path 144 in body 112, 113 for directing a second working fluid flow 146, e.g., steam, in open interior 114 in a second direction SD. Relative to lower casing half shell 122, first working fluid flow path 140 may be created, in part, by a first inlet 147 (FIG. 2) in body 112 for delivering first working fluid flow 142, e.g., steam, into open interior 114 in first direction FD, and second working fluid flow path 144 may be created, in part, by a second inlet 149 (FIGS. 2 and 3 A) in body 112 for delivering second working fluid flow 146, e.g., steam, into open interior 114 in second direction SD. First working fluid flow path 140 and second working fluid flow path 146 in lower casing half shell 122 may also be created, in part, by a circumferentially-extending channel 143 that runs parallel to diaphragm mounting elements 139 and is in fluid communication with inlets 147, 149 (FIG.

3 A).

CLAIMS

What is claimed is:

1. A casing half shell for a turbine system, the casing half shell comprising:

a body having an open interior for enclosing parts of the turbine system;

a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction;

a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction; and

a working fluid dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path, the working fluid dam including a stress-mitigating slot extending radially therein.

2. The casing half shell of claim 1, further comprising a fill member mounted in the stress-mitigating slot.

3. The casing half shell of claim 2, wherein the body further includes a packing head main fit upstream of the working fluid dam and a diaphragm mounting element downstream of the working fluid dam.

4. The casing half shell of claim 3, wherein the stress-mitigating slot extends adjacent an axially facing surface of the packing head main fit, and the fill member is fixedly coupled to the packing head main fit.

5. The casing half shell of claim 3, wherein the casing includes an opening therein, and wherein the fill member is at least partially positioned in the opening.

6 The casing half shell of claim 3, wherein the diaphragm mounting element includes an opening therein, and wherein the fill member is at least partially positioned in the opening.

7. The casing half shell of claim 2, wherein the fill member has a shape selected from the group comprising: a planar plate, an L-shape, and a T-shape.

8. The casing half shell of claim 2, wherein the fill member is fixedly coupled to the working fluid dam.

9. The casing half shell of claim 2, wherein stress-mitigating slot has a radial outer end including a curved shape, and the fill member has a complementary curved shape.

10. A steam turbine (ST) system, the ST system comprising:

at least one of a high pressure (HP) turbine and an intermediate pressure (IP) turbine; a casing including a body having an open interior for enclosing the at least one of the HP steam turbine and the IP steam turbine;

a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction;

a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction; and

a steam dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path to redirect the first and second working fluid flows to the at least one of the HP steam turbine and the IP steam turbine, the steam dam including a stress-mitigating slot extending radially therein; and

a fill member mounted in the stress-mitigating slot.

11. The ST system of claim 10, further comprising a packing head main fit upstream of the steam dam and a diaphragm mounting element downstream of the steam dam.

12. The ST system of claim 11, wherein the stress-mitigating slot extends adjacent an axially facing surface of the packing head main fit, and the fill member is fixedly coupled to the packing head main fit.

13. The ST system of claim 11, wherein the casing includes an opening therein, and wherein the fill member is at least partially positioned in the opening.

14. The ST system of claim 11, wherein the diaphragm mounting element includes an opening therein, and wherein the fill member is at least partially positioned in the opening.

15. The ST system of claim 10, wherein the fill member has a shape selected from the group comprising: a planar plate, an L-shape and a T-shape.

16. The ST system of claim 10, wherein the fill member is fixedly coupled to the steam dam.

17. The ST system of claim 10, wherein the stress-mitigating slot has a radial outer end including a curved shape, and the fill member has a complementary curved shape.

18. A method, compri sing :

providing a casing half shell for a turbine system, the casing half shell including a body having open interior, a first working fluid flow path in the body for directing a first working fluid flow in the open interior in a first direction, a second working fluid flow path in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction, and a working fluid dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path;

forming a stress-mitigating slot extending radially in the working fluid dam; and fixedly coupling a fill member in the stress-mitigating slot.

19. The method of claim 18, further comprising positioning a packing head main fit upstream of the steam dam with a casing flow guide extending therefrom and a diaphragm mounting element downstream of the steam dam, and wherein forming the stress-mitigating slot includes forming an opening into one of the casing flow guide and the diaphragm mounting element, and wherein fixedly coupling the fill member includes positioning the fill member in the stress-mitigating slot and the opening.

20. The method of claim 19, wherein fixedly coupling the fill member includes fixedly coupling the fill member to at least one of the working fluid dam, the packing head main fit and the diaphragm mounting element.