US20120076642A1

US20120076642A1 - Sealing assembly for use in turbomachines and method of assembling same

Info

Publication number: US20120076642A1
Application number: US12/888,490
Authority: US
Inventors: Ya-Tien CHIU; James Royce Howes
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2010-09-23
Filing date: 2010-09-23
Publication date: 2012-03-29
Also published as: CH703883A2; CN102410050A; DE102011053532A1; JP2012067747A

Abstract

A method of assembling a sealing assembly for a turbomachine is provided. The method includes positioning at least one sealing element that includes a substantially tortuous flow path defined therein within at least one channel defined in a rotatable element of the turbomachine. The sealing element is extended circumferentially about the rotatable element such that the sealing element extends into a cavity defined between the rotatable element and a stationary element. This facilitates substantially reducing flow leakage from an upstream region of the cavity to a downstream region of the cavity.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to turbomachines and, more particularly, to a sealing assembly for use in turbomachines.
Known turbomachines include a defined flow path. For example, at least some known steam turbine engines include a defined steam path extending therethrough. Steam leakage can occur either into or from the steam path, and from areas of higher pressure to areas of lower pressure. Such leakage may adversely affect the operating affiance of the turbine. For instance, steam-path leakage that occurs in the turbine between a rotating rotor shaft of the turbine and a surrounding turbine casing may reduce the overall efficiency of the turbine. Similarly, steam-path leakage between a shell and a portion of the casing extending between adjacent turbines may also reduce the overall efficiency of the steam turbine. Over time, reductions in the operating efficiency of the steam turbine may result in increased fuel costs.
To reduce the amount of flowpath leakage, at least some known turbomachines use flow restraining devices, such as seals and flow discouragers. Such flow restraining devices generally reduce an overall size of the area that flow can leak through, and thus reduce the amount of leakage. For example, knife-edge seals may be used in the cavity space between rotatable and stationary components to minimize flow leakage. Known knife-edge seals are formed with a simple two-dimensional shape, such as a trapezoid or a rectangle. Such knife-edge seals extend generally planar along an axis of rotation. To reduce flow leakage, a clearance between a top of a seal tooth and an opposing surface is substantially reduced. However, within known turbomachinery, because the flow has a high tangential velocity, the flow may “skid” along a surface or wall as the flow moves toward a downstream clearance region. Such “skidding” may inhibit the effectiveness of the known knife edge seals such that flow leakage may not be substantially reduced in these areas.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a method of assembling a sealing assembly for use in a turbomachine is provided. The method includes positioning at least one sealing element that includes a substantially tortuous flow path defined therein within at least one channel defined in a rotatable element of the turbomachine. The sealing element is extended circumferentially about the rotatable element such that the sealing element extends into a cavity defined between the rotatable element and a stationary element. This facilitates substantially reducing flow leakage from an upstream region of the cavity to a downstream region of the cavity.
In another embodiment, a sealing assembly for use in a turbomachine is provided. The sealing assembly includes at least one sealing element that includes a substantially tortuous flow path defined therein. The sealing element is sized and shaped to be positioned within at least one channel defined in a rotatable element of the turbomachine. Moreover, the sealing element substantially circumscribes the rotatable element such that the sealing element extends into a cavity defined between the rotatable element and a stationary element. This facilitates substantially reducing flow leakage from an upstream region of the cavity to a downstream region of the cavity.
In a further embodiment, a turbomachine is provided. The turbomachine includes a rotatable element having at least one channel defined circumferentially therein. The tubomachine includes a stationary element that at least partially circumscribes the rotatable element such that the stationary element and the rotatable element at least partially define a cavity between them. Moreover, at least one sealing element that includes a substantially tortuous flow path defined therein is included. The sealing element is sized and shaped to be positioned within the channel. Further, the sealing element substantially circumscribes the rotatable element to facilitate substantially reducing flow leakage from an upstream region of the cavity to a downstream region of the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of a known exemplary opposed-flow steam turbine engine;

FIG. 2 is a cross-sectional schematic view of a portion of an exemplary high pressure (HP) section that may be used with the turbine engine shown in FIG. 1;

FIG. 3 is a perspective partially exploded view of a portion of a sealing assembly that may be used with the HP section shown in FIG. 2 and taken along line 3-3; and

FIG. 4 is a flow chart illustrating an exemplary method of assembling the sealing assembly shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The exemplary methods, apparatus, and systems described herein overcome disadvantages associated with known turbomachines that may operate with fluid leakage within the tubomachine itself and/or its associated hardware components. The embodiments described herein provide a sealing assembly for use in a turbomachine that substantially reduces fluid leakage within the machine, which in turn, improves turbine performance. More specifically, the sealing assembly described herein includes at least one sealing element that includes a substantially tortuous flow path defined therein and the sealing element is located on a rotatable element of a turbomachine, such as the rotatable element found in a compressor of a gas turbine engine or on a rotor shaft of a steam turbine engine.
FIG. 1 illustrates a cross-sectional schematic view of an exemplary opposed-flow steam turbine engine 100 including a high pressure (HP) section 102 and an intermediate pressure (IP) section 104. While FIG. 1 describes an exemplary steam turbine engine, it should be noted that the sealing assembly and method described herein is not limited to any one particular turbine engine. One of ordinary skill in the art should appreciate that the current invention may be used with any turbomachine in any suitable configuration that enables such an apparatus and method.
In the exemplary embodiment, an HP shell or casing 106 is divided axially into respective upper and lower half sections 108 and 110. Similarly, an IP shell 112 is divided axially into respective upper and lower half sections 114 and 116. In the exemplary embodiment, shells 106 and 108 are inner casings. Alternatively, shells 106 and 108 can be outer casings. A central section 118 positioned between HP section 102 and IP section 104 includes a high pressure steam inlet 120 and an intermediate pressure steam inlet 122. Within casings 106 and 112, HP section 102 and IP section 104, respectively, are arranged in a single bearing span that is supported by journal bearings 126 and 128. Steam seal assemblies 130 and 132 are coupled inboard of each journal bearing 126 and 128, respectively.
An annular section divider 134 extends radially inwardly from central section 118 towards a rotatable element 140. In the exemplary embodiment, rotatable element 140 is a rotor shaft. Rotatable element 140 extends between HP section 102 and IP section 104. More specifically, divider 134 circumscribes a portion of rotatable element 140 between a first HP section inlet nozzle 136 and a first IP section inlet nozzle 138. Divider 134 is at least partially inserted in a channel 142 defined in a packing casing 144. More specifically, in the exemplary embodiment, channel 142 is a C-shaped channel 142 that extends radially into packing casing 144 and around an outer circumference of packing casing 144 such that a center opening (not shown in FIG. 1) of channel 142 faces radially outwardly.
During operation, high pressure steam inlet 120 receives high pressure and high temperature steam from a steam source, such as a power boiler (not shown in FIG. 1). Steam is channeled through HP section 102 from inlet nozzle 136, wherein work from the steam induces rotation of element 140. In the exemplary embodiment, the steam strikes a plurality of turbine blades or buckets (not shown in FIG. 1) that are coupled to rotatable element 140. In the exemplary embodiment, each set of buckets are located near a sealing assembly (not shown in FIG. 1) that facilitates channeling steam to the associated buckets. The steam exits HP section 102 and is returned to the boiler wherein it is reheated. Reheated steam is then routed to IP steam inlet 122 and returned to IP section 104 at a lower pressure than steam entering HP section 102, but at a temperature that is approximately equal to the temperature of steam entering HP section 102. Work is extracted from the steam in IP section 104 in a manner substantially similar to that used for HP section 102. Accordingly, an operating pressure within HP section 102 is higher than an operating pressure within IP section 104, such that steam within HP section 102 tends to flow towards IP section 104 through leakage paths defined between HP section 102 and IP section 104. One such leakage path may be defined extending axially along rotatable element 140 through packing casing 144.
In the exemplary embodiment, steam turbine 100 is an opposed-flow HP and IP steam turbine engine. Alternatively, steam turbine 100 may be used with any other turbine including, but not being limited to low pressure turbines. In addition, the present invention is not limited to being used with opposed-flow steam turbines, but rather may be used with any steam turbine configuration including, but not limited to, single-flow and double-flow steam turbine engines. Moreover, as discussed above, the present invention is not limited to only being used in steam turbine engines and can be used in other turbine system, such as gas turbine engines.
FIG. 2 is a cross-sectional schematic view of a portion of an exemplary HP section 143 that may be used with steam turbine engine 100 (shown in FIG. 1). In the exemplary embodiment, HP section 143 includes an upper half casing (not shown in FIG. 2) that is bolted to a lower half casing (not shown in FIG. 2) when section 102 is fully assembled. A nozzle carrier top half 150 mates to the upper half casing such that carrier top half 150 functions as a radial inward extension of the casing. HP section 143 also includes rotatable element 140, a sealing assembly 152, an annular groove 153, and a stationary element 155. Nozzle carrier top half 150 provides support for nozzle 138 (shown in FIG. 1) as well as for a stationary element 155 via grooves 153. A nozzle carrier bottom half (not shown in FIG. 2) is coupled to the lower half casing and receives the nozzle 138 and rotatable element 140 in a manner similar as nozzle carrier top half 150. HP section 143 also includes a rotatable turbine blade or bucket assembly (not shown in FIG. 2) that is fixedly coupled to rotatable element 140.
In the exemplary embodiment, rotatable element 140 has at least one channel 163 defined circumferentially therein. Rotatable element 140 also includes a surface 166. In the exemplary embodiment, rotatable element 140 includes four channels defined circumferentially therein. Alternatively, rotatable element 140 may include any number of channels 163 that would enable rotatable element 140 to function as described herein.
Stationary element 155 has a radially outer portion 156, a nozzle portion 158, and a radially inner portion 160. Stationary element 155 at least partially circumscribes rotatable element 140 such that stationary element 155 and rotatable element 140 at least partially define a cavity 162 between them.
Sealing assembly 152 includes at least one sealing element 164 that substantially circumscribes the rotatable element 140. Moreover, sealing element 164 is at least partially inserted within channel 163. Alternatively, sealing element 164 can be formed integrally with rotatable element 140 such that sealing element 164 is formed integrally within channel 163. In the exemplary embodiment, sealing element 164 is sized and shaped to be positioned in channel 163 such that sealing element 164 extends radially outward a distance 167 from channel 163 into cavity 162. Moreover, in the exemplary embodiment, each sealing element 164 defines a substantially tortuous flow path defined therein.
In the exemplary embodiment, sealing assembly 152 includes four sealing elements 164 that are each at least partially inserted within separate channels 163. Alternatively, sealing assembly 152 may include any number of sealing elements 163 that would enable assembly 152 to function as described herein.
During operation, steam enters section 143 via HP section steam inlet 120 (shown in FIG. 1) and is channeled through section 102 as illustrated by the arrows 180. Inlet nozzle 136 (shown in FIG. 1) and the associated bucket assembly (not shown in FIG. 2) define a first stage of engine 100. Inlet nozzle 136 and nozzle 158 facilitate channeling steam toward the bucket assembly. More specifically, steam flows across nozzle portion 158 as illustrated by the associated arrows 176 from an upstream region 177 to a downstream region 179. Steam also flows across cavity 162 as illustrated by the associated arrows 180 from an upstream region 190 of cavity 162 to a downstream region 192 of cavity 162.
When steam flow is channeled through the cavity 162, the flow comes into contact with sealing element 164. Sealing element 164 includes a substantially tortuous flow path defined therein that facilitates mitigating the flow through cavity 162. More specifically, sealing element 164 disrupts the ability for flow to “skid” along the surface 166, which substantially reduces flow leakage from the upstream region 190 of cavity 162 to the downstream region 192 of cavity. Steam flow is then diverted across nozzle portion 158.
FIG. 3 illustrates a perspective partially exploded view of a portion of sealing assembly 152 taken along line 3-3 (shown in FIG. 2). Sealing element 164 is positioned within channel 163. More specifically, in the exemplary embodiment, three sealing elements 164 are each positioned within separate channels 163. Moreover, in the exemplary embodiment, one sealing element 190 is shown positioned a distance from channel 163 to enable sealing element 164 to be described herein.
Each channel 163 is formed with a centerline 203 or an axis of symmetry that extends therethrough. Moreover, each channel 163 is formed with an upstream portion 204 and a downstream portion 206 that each extend axially a distance 207 from centerline. Upstream channel portion 204 and downstream channel portion 206 each extend axially from centerline 203. In the exemplary embodiment, downstream channel portion 206 is aligned substantially symmetrical with upstream channel portion 204 and with respect to centerline 203.
Sealing element 164 has a centerline 208 or an axis of symmetry defined thereon. Centerline 208 is substantially collinear with channel centerline 203. More specifically, each sealing element 164 is substantially centered within channel 163.
Moreover, in the exemplary embodiment, sealing element 164 is formed with an upstream portion 210 and a downstream portion 212 that each extends axially from channel centerline 203 such that downstream portion 212 is aligned substantially with upstream portion 210 and with respect to centerline 203. Alternatively, downstream portion 212 and/or upstream portion 210 may be aligned in a skewed manner and/or may not be substantially symmetrical with respect to centerline 203.
In the exemplary embodiment, each sealing element 164 has a substantially three-dimensional shape and a substantially tortuous flow path defined therein. Moreover, each sealing element 164 includes a first portion 214 that extends axially a distance 215 from channel centerline 203 in a first direction and a second portion 216 that extends axially a distance 217 from channel centerline 203 in a second direction, and the second direction is different from the first direction. For example, as shown in FIG. 4, second portion 216 extends in an opposite direction than first portion 214, such that sealing element 164 is formed with a generally sinusoidal shape.
FIG. 4 is a flow chart illustrating an exemplary method 300 of assembling a sealing assembly, such as sealing assembly 152 (shown in FIGS. 2 and 3). The method 300 includes positioning 302 at least one sealing element 164 (shown in FIGS. 2 and 3) that includes a substantially tortuous flow path defined therein within at least one channel 163 (shown in FIGS. 2 and 3) defined in a rotatable element 140 (shown in FIGS. 1, 2 and 3).
The sealing element 164 is extended 304 about the rotatable element 140 such that the sealing element 164 extends into a cavity 162 (shown in FIG. 2) defined between rotatable element 140 and a stationary element 155 (shown in FIG. 2) to facilitate substantially reducing flow leakage from an upstream region 190 (shown in FIG. 2) of cavity 162 to a downstream region 192 (shown in FIG. 2) of cavity 162.
The sealing element 164 is inserted 306 at least partially within channel 163 such that sealing element 164 extends radially outward from the channel 163. Alternatively, sealing element 164 may be formed 308 integrally with the rotatable element 140.
Moreover, when sealing element 164 is positioned 302 within channel 163, sealing element 164 is positioned 310 such that sealing element 164 is substantially centered within channel 163.
Further, an upstream portion 210 (shown in FIG. 3) of sealing element 164 and a downstream portion 212 (shown in FIG. 3) of sealing element 164 are each positioned 312 to extend axially from a centerline 203 (shown in FIG. 3) of the channel 163. Moreover, a first portion 214 (shown in FIG. 3) of sealing element 164 is extended 314 axially from the channel centerline 203 in a first direction and a second portion 216 (shown in FIG. 3) of sealing element is extended axially from the channel centerline 203 in an opposite direction from the first portion 214. Moreover, when at least one sealing element 164 is positioned 302 within channel 163, at least one sealing element 164 having a substantially sinusoidal shape is positioned 316 within channel 163.
The methods and apparatus for a sealing assembly described herein facilitates enhancing the operation of turbomachines and provides a more robust turbomachine seal configuration as compared to known seals and flow discourages currently used. More specifically, the embodiments described above provide a sealing assembly for use in a turbomachine that substantially reduces fluid leakage within the machine. The sealing assembly utilizes a sealing element located on a rotatable element of a turbomachine. The sealing element has a substantially three dimensional shape and defines a substantially tortuous flow path. Sealing element disrupts the ability for flow to skid along a surface of the rotatable element, which then substantially reduces flow leakage. Such seal configuration facilitates efficiency, reliability, and reduced maintenance costs for turbomachines.
Exemplary embodiments of sealing assemblies as associated with turbomahcines are described above in detail. The methods, apparatus, and systems are not limited to the specific embodiments described herein nor to the specific illustrated sealing assembly. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. Moreover, references to “one embodiment” in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
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.

Claims

1. A method of assembling a sealing assembly for use in a turbomachine, said method comprising:

positioning at least one sealing element that includes a substantially tortuous flow path defined therein within at least one channel defined in a rotatable element of the turbomachine; and

extending the at least one sealing element circumferentially about the rotatable element such that the at least one sealing element extends into a cavity defined between the rotatable element and a stationary element to facilitate substantially reducing flow leakage from an upstream region of the cavity to a downstream region of the cavity.

2. A method in accordance with claim 1 further comprising inserting the at least one sealing element at least partially within the at least one channel such that said sealing element extends radially outward from the at least one channel.

3. A method in accordance with claim 1 further comprising forming the at least one sealing element integrally with the rotatable element.

4. A method in accordance with claim 1, wherein said positioning at least one sealing element further comprises positioning at least one sealing element substantially centered within the at least one channel.

5. A method in accordance with claim 1 further comprising:

positioning an upstream portion of the at least one sealing element to extend axially from a centerline of the at least one channel; and

positioning a downstream portion of the at least one sealing element to extend axially from the channel centerline.

6. A method in accordance with claim 5 further comprising extending a first portion of the at least one sealing element axially from the channel centerline in a first direction; and

extending a second portion of the at least one sealing element axially from the channel centerline in an opposite direction than first portion.

7. A method in accordance with claim 1, wherein said positioning at least one sealing element further comprises positioning at least one sealing element having a substantially sinusoidal shape within the at least one channel.

8. A sealing assembly for use in a turbomachine, said sealing assembly comprising at least one sealing element that comprises a substantially tortuous flow path defined therein, wherein said at least one sealing element is sized and shaped to be positioned within at least one channel defined in a rotatable element of said turbomachine, said at least one sealing element substantially circumscribes said rotatable element such that said at least one sealing element extends into a cavity defined between the rotatable element and a stationary element to facilitate substantially reducing flow leakage from an upstream region of said cavity to a downstream region of said cavity.

9. A sealing assembly in accordance with claim 8, wherein said at least one sealing element is sized and shaped to be positioned within said channel such that said at least one sealing element extends radially outward from said at least one channel.

10. A sealing assembly in accordance with claim 8, wherein said at least one sealing element is at least partially inserted within said at least one channel.

11. A sealing assembly in accordance with claim 8, wherein said at least one sealing element is integrally formed with said rotatable element.

12. A sealing assembly in accordance with claim 8, wherein said at least one sealing element is substantially centered within said at least one channel.

13. A sealing assembly in accordance with claim 8, wherein said at least one sealing element comprises an upstream portion extending axially from a centerline of said at least one channel and a downstream portion extending axially from said channel centerline.

14. A sealing assembly in accordance with claim 13, wherein said at least one sealing element further comprises:

a first portion extending axially from said channel centerline in a first direction; and

a second portion extending axially from said channel centerline in an opposite direction than said first portion.

15. A sealing assembly in accordance with claim 8, wherein said at least one sealing element has a substantially sinusoidal shape.

16. A turbomachine comprising:

a rotatable element having at least one channel defined circumferentially therein;

a stationary element that at least partially circumscribes said rotatable element such that said stationary element and said rotatable element at least partially define a cavity therebetween; and

at least one sealing element comprising a substantially tortuous flow path defined therein, wherein said at least one sealing element is sized and shaped to be positioned within said at least one channel, said at least one sealing element substantially circumscribes said rotatable element to facilitate substantially reducing flow leakage from an upstream region of said cavity to a downstream region of said cavity.

17. A turbomachine in accordance with claim 16, wherein said at least one sealing element is substantially centered within said at least one channel.

18. A turbomachine in accordance with claim 16, wherein said at least one sealing element comprises an upstream portion extending axially from a centerline of said at least one channel and a downstream portion extending axially from said channel centerline.

19. A turbomachine in accordance with claim 18, wherein said at least one sealing element further comprises:

20. A turbomachine in accordance with claim 16, wherein said at least one sealing element has a substantially sinusoidal shape.