The subject matter disclosed herein relates to steam turbine engines and, more specifically, to an inner casing for the steam turbine engines.
In certain applications, steam turbines may include various sections designed to be assembled during installation. For example, each steam turbine may include an outer casing and an inner casing disposed within the outer casing. Also, the steam turbine may include a reaction drum that includes multiple reaction stages, wherein the reaction drum can be integrated or separated from the inner casing. The inner casing can be partial arc or full admission belt of steam to an impulse stage. The assembly of these numerous components is costly. In addition, the assembly of these numerous components may limit the effectiveness of seals throughout the steam turbine (e.g., limiting balancing drum seal and steam recovery drum seal diameters).
Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In accordance with a first embodiment, a system includes a steam turbine. The steam turbine includes an outer casing and an inner casing disposed within the outer casing. The inner casing is horizontally split in an axial direction into an upper inner casing portion and a lower inner casing portion. The steam turbine also includes an impulse stage disposed within the inner casing, wherein the inner casing is configured to provide full arc admission of a fluid to the impulse stage. The steam turbine further includes at least one reaction stage having multiple blades. The at least one reaction stage is integrated within the inner casing.
In accordance with a second embodiment, a system includes a steam turbine inner casing configured to be disposed within an outer casing of a steam turbine. The steam turbine inner casing is horizontally split in an axial direction into an upper inner casing having an upper flange portion and lower inner portion having a lower flange portion. The upper and lower flange portions form a horizontally split flange. The steam turbine inner casing is configured to be disposed about an impulse stage and to provide full arc admission of a fluid to the impulse stage. The steam turbine inner casing is also configured to be integrated with and disposed about at least one reaction stage having multiple blades.
In accordance with a third embodiment, a system includes a steam turbine. The steam turbine includes an outer casing and a horizontally split inner casing disposed within the outer casing. The horizontally split inner casing includes an upper inner casing portion having an upper flange portion and a lower inner casing portion having a lower flange portion. The upper and lower flange portions form a horizontally split flange. The horizontally split inner casing also includes multiple steam ducts that define a fluid flow path through the upper and lower inner casing portions. The fluid flow path is configured to provide full arc admission of a fluid to an impulse stage via the fluid flow path. At least one steam duct includes an upper steam duct portion disposed in the upper inner casing portion and a lower steam duct portion disposed in the lower inner casing portion. The upper and lower steam duct portions form a sealed interface between the upper and lower flange portions to block leakage of fluid through the sealed interface. The sealed interface includes an annular seal disposed between the upper and lower steam duct portions and an anti-rotation mechanism disposed through a portion of the annular seal to block rotation of the annular seal relative to the upper and lower steam duct portions.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
The present disclosure is directed towards steam turbines (e.g., high pressure steam turbines using live steam up to approximately 140 bars) having a horizontally split inner casing. The steam turbine includes an outer casing and an inner casing disposed within the outer casing. The inner casing is horizontally split in an axial direction (e.g., along a horizontally split flange) into an upper inner casing portion (e.g., having an upper flange portion) and a lower inner casing portion (e.g., having a lower flange portion). The horizontally split flange may reduce costs associated with the assembly of the steam turbine, while enabling greater balancing drum seal and steam recovery drum seal diameters. The inner casing includes one or more reaction stages integrated within the inner casing. The integrated reactions stages may limit the pressure exerted on the outer casing. The steam turbine includes an impulse stage (e.g., set of moving blades disposed behind a nozzle) disposed within the inner casing upstream of the one or more reactions stages (e.g., alternating rows of stationary blades). The steam turbine also includes a plurality of steam ducts that a define a fluid flow path (e.g., steam flow path) through the upper and inner casing portions to provide full arc admission (e.g., admission of the fluid completely around the rotor or approximately 360 degrees of admission) of the fluid (e.g., steam) to the impulse stage. The full arc admission on the impulse stage minimizes stress on the rotary blades of the impulse stage while keeping high steam mass flow. In certain embodiments, one or more of the steam ducts (e.g., steam passages) include an upper steam duct portion (e.g., structure with steam passage) disposed in the upper inner casing and a lower steam duct portion (e.g., structure with steam passage) disposed in the lower inner casing portion that form a sealed interface between the upper and lower flange portions to block leakage of fluid through the sealed interface. In certain embodiments, the sealed interface includes an annular seal and an anti-rotation mechanism disposed through a portion of the annular seal to block rotation of the annular seal relative the upper and lower steam duct portions. The sealed interface may help drive the fluid (e.g., steam) toward the lower steam duct portions. In some embodiments, the inner casing includes a retainer (e.g., axial thrust retainer) that interfaces with a portion (e.g. protrusion) of the outer casing. In particular, an upper retainer portion (e.g., including a groove) may partially extend circumferentially relative to a rotational axis of the steam turbine about an outer surface of the upper inner casing portion. Also, a lower retainer portion (e.g., including a groove) may partially extend circumferentially relative to the rotational axis of the steam turbine about an outer surface of the lower inner casing portion. The retainer may block movement of the inner casing relative to the outer casing in response to axial force generated during operation of the steam turbine. In addition, the retainer enables fluid passage (e.g., steam) between the chambers of the steam turbine, thus, enabling steam seal recovery and increased turbine efficiency.
Turning now to the drawings,
The steam turbine 10 includes an outer casing 22 and the inner casing 12 disposed within the outer casing 22. The inner casing 12 generally has a barrel shape or hollow annular shape. The inner casing 12 is horizontally split in the axial direction 16 into an upper inner casing portion 24 (e.g., half or semi-cylindrical portion) and a lower inner casing portion 26 (e.g., half or semi-cylindrical portion, see
The upstream portion 28 of the inner casing 12 is disposed about an impulse stage 40 (e.g., high pressure impulse stage) located upstream of a plurality of reaction stages 42 integrated within (i.e., part of) the downstream portion 30 of the inner casing 12. The impulse stage 40 includes one or more nozzles 44 and one or more rows of moving or rotary blades 46 coupled to a rotating component 47 (e.g. shaft or rotor) that rotates about the rotational axis 20. The inner casing 12 includes a plurality of steam ducts 48 (e.g., inner ducts) that define a fluid flow path 50 (e.g., steam flow path) through the upper and inner casing portions 24, 26 to provide full arc admission (e.g., approximately 360 degrees) of the fluid (e.g., steam) to the impulse stage 40. The full arc admission on the impulse stage 40 may minimize stress on the rotary blades 46. In certain embodiments, one or more the steam ducts 48 includes an upper steam duct portion 112, 114 disposed in the upper inner casing portion 24 and a lower steam duct portion 116, 118 disposed in the lower inner casing portion 26. The upper and lower inner steam duct portions 112, 114, 116, 118 may form a sealed interface 126 (e.g., where the flange 88 splits) to block leakage of steam through the sealed interface 126. As described in greater detail below, the sealed interface 126 may include an annular seal 128 and an anti-rotation mechanism 136 to block rotation of the annular seal 128 relative to the upper and lower duct portions 112, 114, 116, 118. The seal system on the horizontally split flange 88 may drive the fluid (e.g., steam) on the lower steam duct portions 116, 118.
As mentioned above, the plurality of reaction stages 42 are integrated within (i.e., part of) the downstream portion 30 of the inner casing 12. The downstream portion 30 of inner casing 12 is disposed circumferentially 18 (e.g., approximately 360 degrees) about the plurality of reaction stages 42 including a plurality of blades 52. Specifically, moving blades 54 are attached to the rotating element 47 and stationary blades 56 are attached to the inner casing 12. The moving blades 54 and the stationary blades 56 are arranged alternatively in the axial direction 16, wherein each row includes one or more of either the moving blades 54 or stationary blades 56. The integration of the plurality of reaction stages 42 within the inner casing 12 may limit the pressure exerted on the outer casing 22.
The inner casing 12 also includes a retainer 58 that interfaces with a portion 60 (e.g., protrusion) of the outer casing 22 that extends from the inner surface 34. The retainer 58 includes a groove 62 (e.g., u-shaped groove) that receives the protrusion 60 of the outer casing 22. The groove 62 interfaces with the protrusion 60 to block movement of the inner casing 12 relative to the outer casing 22 in response to an axial force generated during the operation of the steam turbine 10. In particular, the groove 62 partially surrounds the protrusion 60 to block movement of the inner casing 12 in the axial direction 16. In certain embodiments, the retainer 58 includes an upper retainer portion 64 (see
Additional components of the steam turbine 10 include a steam recovery drum 72 and a balancing drum 74. The upstream portion 28 of the inner casing 12 is circumferentially 18 disposed about the steam recovery drum 72. The balancing drum 74 is located axially 16 upstream of the inner casing 12. The balancing drum 74 maintains the balance of the rotating component 47 of the steam turbine 10 via regulation of pressure (e.g., back pressure). As mentioned above, the horizontally split inner casing 12 and its associated features may reduce the costs of assembly of the steam turbine 10, while increasing the efficiency of the steam turbine 10 by enhancing the balancing drum 74 and steam recovery drum 72 seals to block fluid (e.g., steam) leaks.
Fluid (e.g., high pressure steam) flows from the outer casing 22 to the inner casing 12 through passage 38 into the fluid flow path 50 defined by the steam ducts 48 within the inner casing 12. The pressurized fluid in the fluid flow path 50 is provided via full arc admission to the impulse stage 40, where the one or more nozzles 44 direct the fluid onto the moving blades 46. As the fluid travels through the nozzles 44 it loses pressure but increases in velocity. The motive force of the fluid from the nozzles 44 causes the moving blades to rotate about the rotating component 47 and the rotational axis 20. Overall the fluid increases in net velocity as it exits the impulse stage 40. The fluid travels from the impulse stage 40 to the plurality of reaction stages 42. The fluid alternately travels through the stationary and moving blades 54, 56 of the reaction stages 42. The stationary blades 54 direct the fluid flow towards the moving blades 56. The motive force from the directed flow results in the rotation of the moving blades circumferentially 18 about the rotating component 47 and the rotational axis 20. After passing through the plurality of reactions stages 42, the fluid exits the inner casing 12 of the steam turbine 10.
The upper and lower inner casing portions 24, 26 each include the upstream portion 28 and the downstream portion 30. The upstream portion 28 of each respective inner casing portion 24, 26 radially 14 extends outward from the respective outer surfaces 36, 92 of each respective inner casing portion 24, 26. The upstream portions 28 of the upper and lower inner casing portion 24, 26 house the plurality of steam ducts 48 (see
As mentioned above, the inner casing 12 also includes the retainer 58 that interfaces with the portion 60 (e.g., protrusion) of the outer casing 22 that extends from the inner surface 34. The retainer 58 includes the groove 62 (e.g., u-shaped groove) that receives the protrusion 60 of the outer casing 22. The groove 62 interfaces with the protrusion 60 to block movement of the inner casing 12 relative to the outer casing 22 in response to an axial force generated during the operation of the steam turbine 10. In particular, the groove 62 partially surrounds the protrusion 60 to block movement of the inner casing 12 in the axial direction 16. As depicted in
The respective upper steam duct portions 112, 114 and lower steam duct portions 116, 118 of steam ducts 100, 108 each form a sealed interface 126 (e.g., where the flange 88 splits) to block leakage of fluid through the sealed interface 126 (see also
Technical effects of the disclosed embodiments include providing the horizontally split inner casing 12 for a high pressure steam turbine 10. The inner casing 12 includes features to reduce the costs of assembly of the steam turbine 10, while increasing the efficiency of the steam turbine 10 by enhancing the balancing drum 74 and steam recovery drum 72 seals to block fluid (e.g., steam) leaks. For example, the inner casing 12 enables full arc admission to the impulse stage 40 to minimize stress on the rotary blades 46. The inner casing 12 also enables the integration of the plurality of reaction stages 42 within the inner casing 12 to limit pressure on the outer casing 22. In addition, the inner casing 12 includes a seal system on the horizontally split flange 88 to drive steam on the lower portions of the steam ducts 48.
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.
Number | Date | Country | Kind |
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CO2013A0001 | Jan 2013 | IT | national |
This application is a continuation of U.S. patent application Ser. No. 13/886,204, filed May 2, 2013, titled “INNER CASING FOR STEAM TURBINE ENGINE,” which claims priority to and benefit of Italian Patent Application No. CO2013A000001, entitled “INNER CASING FOR STEAM TURBINE ENGINE,” filed Jan. 23, 2013, which are hereby incorporated by reference herein in their entireties.
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Number | Date | Country | |
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20190040763 A1 | Feb 2019 | US |
Number | Date | Country | |
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Parent | 13886204 | May 2013 | US |
Child | 16154047 | US |