Patent Application
20140119879
The subject matter disclosed herein relates to power systems. More particularly, the subject matter relates to turbomachine-based power systems.
Conventional turbomachines, e.g., gas turbomachines extract energy from fluid flow (e.g., gas fluid flow). One interest in turbomachine design is to provide high efficiency for energy generation. A turbine typically experiences efficiency loss due to working fluid leakage through a clearance gap between a turbine blade and a nozzle diaphragm in a turbine stage. The gap between the turbine blade and the casing can allow the working fluid (primary flow) to mix with a cooling fluid path (secondary flow), and decrease the efficiency of the turbine.
Various embodiments of the invention include a turbomachine with a plasma seal system. In some cases, the turbomachine can include: a diaphragm section having: an axially facing diaphragm wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing bucket wall opposing the axially facing diaphragm wall; and a seal member extending from the axially facing bucket wall, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.
A first aspect of the invention includes a turbomachine having: a diaphragm section having: an axially facing diaphragm wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing bucket wall opposing the axially facing diaphragm wall; and a seal member extending from the axially facing bucket wall, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.
A second aspect of the invention includes a turbomachine having: a diaphragm section having: an axially facing diaphragm wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing bucket wall opposing the axially facing diaphragm wall; and a seal member extending from the axially facing bucket wall, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; a fluid channel extending between the axially facing diaphragm wall and the axially facing bucket wall, the fluid channel intersecting with the radial gap; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.
A third aspect of the invention includes a method including: providing a turbomachine having: a diaphragm section having: an axially facing diaphragm wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing bucket wall opposing the axially facing diaphragm wall; and a seal member extending from the axially facing bucket wall, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section; and actuating the plasma generator to generate a plasma which reduces the radial gap between the seal member and the discourager seal, wherein the plasma further reduces an axial gap between the discourager seal a radially extending portion of the seal 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.
As noted, the subject matter disclosed herein relates to power systems. More particularly, the subject matter relates to turbomachine-based power systems and fluid flow within those systems. In particular, aspects of the invention relate to gas turbomachines (also referred to as gas turbines).
As described herein, conventional turbomachines, e.g., gas turbomachines, extract energy from fluid flow (e.g., gas fluid flow). One interest in turbine design is to provide high efficiency for energy generation. A turbine typically experiences efficiency loss due to working fluid leakage through a clearance gap between a turbine blade and a nozzle diaphragm in a turbine stage. The gap between the turbine blade and the casing can allow the working fluid (primary flow) to mix with a cooling fluid path (secondary flow), and decrease the efficiency of the turbine.
In order to address these conventional concerns, various embodiments of the invention include turbomachine (e.g., gas turbine) plasma seal systems. The plasma seal systems disclosed according to various embodiments of the invention include a plasma generator operably connected (e.g., mounted) on a portion of the gas turbine diaphragm. In particular embodiments, the plasma generator is mounted on the discourager seal of the diaphragm to prevent mixing of the primary (working fluid) flow with the secondary (cooling fluid) flow in the turbomachine. The plasma generator creates a plasma seal between the “angel wing” seal of the rotor and the discourager seal (flow guide) of the turbomachine diaphragm. In particular, the plasma generator can be configured to generate a plasma (e.g., a plasma coating or layer) between the discourager seal and the angel wing seal to reduce the radial gap between these components. This helps to define the two distinct fluid flow paths (working fluid v. cooling fluid), thereby enhancing the mechanical work performed by the working fluid.
Various particular embodiments of the invention include a turbomachine having: a diaphragm section including: an axially facing wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing wall opposing the axially facing wall of the diaphragm section; and a seal member extending from the axially facing wall of the bucket, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.
Various additional embodiments of the invention include a turbomachine having: a diaphragm section having: an axially facing wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing wall opposing the axially facing wall of the diaphragm section; and a seal member extending from the axially facing wall of the bucket, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; a fluid channel extending between the axially facing wall of the diaphragm section and the axially facing wall of the bucket, the fluid channel intersecting with the radial gap; and a plasma generator coupled to the diaphragm section for generating a plasma which reduces the radial gap between the seal member and the discourager seal.
Various other embodiments of the invention include a method including: providing a turbomachine having: a diaphragm section having: an axially facing wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing wall opposing the axially facing wall of the diaphragm section; and a seal member extending from the axially facing wall of the bucket, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section; and actuating the plasma generator to generate a plasma which reduces the radial gap between the seal member and the discourager seal, wherein the plasma further reduces an axial gap between the discourager seal a radially extending portion of the seal member.
As will be described herein, generating plasma in the radial gap between the seal member (e.g., angel wing seal) and the discourager seal can help to reduce fluid flow losses in the working fluid section of the turbomachine. Additionally, the use of a plasma generator for this purpose allows for preservation of the clearance between the seal member and the discourager seal when the turbomachine is not operating (or when the plasma generator is not actuated). This clearance is conventionally referred to as the “cold” clearance, which implies that it exists when the turbomachine is not running. The plasma generator-based clearance management solution described according to embodiments of the invention allows for reduction of the “hot” (during operation) clearance between the seal member and discourager seal, without negatively affecting the cold clearance between these components.
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The rotor section 6 can include a bucket 14 (more than one shown) with an axially facing wall 16 opposing the axially facing wall 8 of the diaphragm section 4. These axially facing walls 8, 16 help to form a fluid channel 18 (also referred to as a non-linear fluid channel herein) which spans from a primary fluid (e.g., working fluid) section 20 of the turbomachine 2 to a secondary fluid (e.g., cooling fluid) section 22 of the turbomachine 2. The rotor section 6 can further include a seal member 24 extending from the axially facing wall 16 of the bucket 14. The seal member 24 can be formed as a conventional “angel-wing” seal member, which can include an axially extending portion 26 and a radially extending portion 28 connected with (e.g., continuous with) the axially extending portion 26 (only partially labeled in some circumstances for clarity of illustration). In various embodiments the seal member 24 is an integral component without discernible distinction between the axially extending portion 26 and the radially extending portion 28.
The seal member 24 axially overlaps (along axis A) a portion of the discourager seal 10, such that a line running parallel with the radial direction (r) (or, perpendicular to the axis A) can intersect a portion of the seal member 24 and the discourager seal 10. Between the seal member 24 and the discourager seal 10 is a radial gap 30. As described herein, various embodiments of the invention are directed toward partially closing or reducing the size of that radial gap 30.
The turbomachine 2 can further include a plasma generator (PG) 32 coupled to the diaphragm section 4. The plasma generator 32 can be coupled, e.g., physically affixed to, embedded within, housed within, etc., the diaphragm section 4 at any suitable location for performing the plasma generation functions described herein. In particular embodiments, the plasma generator 32 can be coupled (e.g., physically connected) to the discourager seal 10. The plasma generator 32 can be configured to generate a plasma (
As shown, the bucket 14 can further include a base section 36 and a blade 38 extending radially from the base section 36. The base section 36 can include the axially facing surface 16 of the bucket 14. The diaphragm section 4 can also include at least one nozzle 37, which interacts with the blade 38 to guide a working fluid (e.g., gas) over the face of the blade 38.
As noted herein, the plasma generator 32 includes the embedded electrode 42 and the exposed electrode 44, separated by the plasma dielectric 40. The plasma dielectric 40 is exposed to the secondary flow 22 as it flows through the turbomachine 2. The current (e.g., AC current) supply 46 is connected to the electrodes to supply a high voltage AC potential to the electrodes 42, 44.
When the AC amplitude is large enough, the secondary flow 22 ionizes in a region of largest electric potential forming the plasma 46. The plasma 46 generally begins at an edge 48 of the exposed electrode 44, which is exposed to the secondary flow 22 and spreads out over an area projected by the exposed electrode 44 which is covered by the plasma dielectric 30. The plasma 46 in the presence of an electric field gradient produces a force on the gas flow 22 located between the seal member 24 and the plasma 46, inducing a virtual aerodynamic shield which helps to prevent secondary flow 22 from entering the primary flow 20 of the turbomachine 2.
Various embodiments of the invention relate to a method of forming a plasma on a turbomachine (e.g., turbomachine 2) to at least partially seal a gap between components of the turbomachine.
Process P1: Providing a turbomachine having: a diaphragm section having: an axially facing wall; and a discourager seal protruding axially from the axially facing diaphragm wall; a rotor section having: a bucket having an axially facing wall opposing the axially facing wall of the diaphragm section; and a seal member extending from the axially facing wall of the bucket, wherein the seal member axially overlaps a portion of the discourager seal of the diaphragm section leaving a radial gap between the seal member and the discourager seal; and a plasma generator coupled to the diaphragm section; and
Process P2: Actuating the plasma generator to generate a plasma which reduces the radial gap between the seal member and the discourager seal. It is understood that the process of actuating the plasma generator includes initiating generation of the plasma, e.g., by increasing an AC current supplied to the electrodes 42, 44 via a dial, switch, or other mechanism. It is further understood that the plasma can also reduce the axial clearance between the discourager seal and the radially extending portion of the seal member, helping to prevent the secondary flow from entering the primary flow of the turbomachine.
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. It is further understood that the terms “front” and “back” are not intended to be limiting and are intended to be interchangeable where appropriate.
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.
