Patent Application
20110285090
The subject matter disclosed herein relates generally to seal assemblies between rotating and stationary components of machines and, more particularly, to seal teeth mating surfaces for receiving seal teeth in a turbine during different phases of turbine operation.
As used throughout this application, reference to machine is to include machines having rotating and stationary components, including, for example, a steam turbine, a gas turbine or a compressor.
In a machine, a seal assembly between rotating and stationary components is an important part of machine performance. A seal assembly may be comprised of a seal tooth and a mating surface. For example, in a steam turbine, it will be appreciated that the greater the number and magnitude of steam leakage paths, the greater the losses of efficiency of the steam turbine. In a main flow path of a steam turbine, a plurality of stages are used to efficiently extract energy from the high-pressure and high-temperature fluid flow to drive an electrical generator. In each stage, there is a row of stationary blades (nozzles) and a row of rotating blades (buckets). Clearances are needed between the nozzles and a rotor and between the buckets and a casing. Improving the seal assemblies and reducing steam leakage paths improves steam turbine efficiency.
For example, in a steam turbine, the thermal mass of rotor 102 is relatively small compared with that of casing 104. Prior to start up, the rotor 102 and casing 104 are in a cold assembly position. During a shut-down or temperature increasing of steam turbine, rotor 102 heats up and expands faster than casing 104. As a result, rotor 102 changes position relative to casing 104. For example, rotor 102 moves in an axial direction away 110 from thrust bearing 103 relative to casing 104. As casing 104 and rotor 102 approach a same temperature, rotor 102 returns to approximately its cold assembly position relative to casing 104 until the parts reach the same temperature, at which point steam turbine reaches a steady-state. In steady-state, relative position of rotor 102 to casing 104 remains substantially the same if the rotor and casing are made of the same materials or materials with similar thermal expansion rates. During a shut-down or temperature decreasing of steam turbine, rotor 102 cools faster than casing 104 and rotor 102 changes position relative to casing 104 in the opposite direction as during shut-down or temperature increasing. For example, rotor 102 moves in an axial direction towards 112 thrust bearing 103 relative to casing 104. In addition to axial movement, rotor 102 may move in a radial direction 114 due to vibration during shut-down or temperature increasing and shut-down or temperature decreasing or temperature decreasing. A person skilled in the art will readily recognize that in a machine 100 the relative movement of rotor 102 to casing 104 will depend upon the differing thermal properties. For example, if rotor 102 is relatively large in thermal mass compared to casing 104, rotor 102 would heat slower than casing 104 during shut-down or temperature increasing.
Seal teeth 116 may be placed on rotor 102, radially extending rotating components 106, casing 104, or radially extending stationary components 108.
Seal tooth 116 may include a brush seal. During shut-down or temperature increasing or shut-down or temperature decreasing, the tip of brush seal may have too much interference with seal tooth mating surface causing the brush seal tip to wear. Wearing of brush seal tip may cause more leakage particularly upon reaching steady-state operation.
A first aspect of the disclosure provides a seal assembly for sealing a stationary component and a rotating component, the seal assembly comprising: a seal tooth mating surface for mating with a seal tooth, the seal tooth mating surface including: a plateau portion for sealingly receiving the seal tooth during a steady-state operation of the seal assembly and a first concave portion adjacent to the plateau portion for receiving the seal tooth with a clearance during a first non-steady-state operation of the seal assembly, wherein the seal tooth is coupled to one of the stationary component and the rotating component and the seal tooth mating surface is coupled to the other of the stationary component and the rotating component.
A second aspect of the disclosure provides a turbine, comprising: a seal assembly for sealing a stationary component and a rotating component, the seal assembly comprising: a seal tooth mating surface for mating with a seal tooth, the seal tooth mating surface including: a plateau portion for sealingly receiving the seal tooth during a steady-state operation of the seal assembly and a first concave portion adjacent to the plateau portion for receiving the seal tooth with a clearance during a first non-steady-state operation of the seal assembly, and wherein the seal tooth is coupled to one of the stationary component and the rotating component and the seal tooth mating surface is coupled to the other of the stationary component and the rotating component.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.
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 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 indicated above aspects of the invention provide improved operation, performance and efficiency of a machine. As used throughout this application, reference to machine is to include machines having rotating and stationary components, including, for example, a steam turbine, a gas turbine or a compressor.
In an alternative embodiment, casing 304 may also include a first ancillary seal tooth mating surface 329 and a second ancillary seal tooth mating surface 332. Other embodiments may include a single ancillary seal tooth mating surface or more than two ancillary seal tooth mating surfaces. First ancillary seal tooth mating surface 329 may include a first ancillary concave portion 330 for receiving the first ancillary seal tooth 318 during the first non-steady-state operation, e.g., a shut-down or temperature increasing, of machine 300. Second ancillary seal tooth mating surface 332 may include a second ancillary concave portion 333 for receiving the second ancillary seal tooth 318 during the second non-steady-state operation, e.g., a shut-down or temperature decreasing, of machine 300. First ancillary concave portion 330 and second ancillary concave portion 333 may be concavely shaped relative to inner surface 320 of casing 304 and relative to respective ancillary seal teeth 318, 319. Either or both ancillary concave portions 330, 333 may also include any concave shape. First ancillary seal tooth mating surface 329 may include a first ancillary plateau portion 331 for receiving first ancillary seal tooth 318 during steady-state operation of machine 300. Similarly, second ancillary seal tooth mating surface 332 may include a second ancillary plateau portion 334 for receiving the second ancillary seal tooth 318 during steady-state operation of machine 300. Other embodiments may include more than two ancillary seal teeth. First ancillary seal tooth 318 may be adjacent to seal tooth 316 and second ancillary seal tooth 319 may be adjacent to seal tooth 316 and opposite first ancillary seal tooth 318.
Radially extending rotating component 306 with seal tooth 316 may include, for example, a bucket and a bucket cover. Seal tooth 316 and either or both ancillary seal teeth 318, 319 may include, for example, a caulked J-strip, a steel strip, a machined integral tooth, an inserted tooth seal, and a brush seal. Plateau portion 328 may include configuration for steady-state clearance between seal tooth mating surface 322 and a seal tooth 316. “Steady-state clearance” is sufficient clearance to substantially avoid rubbing between each seal tooth 316 and seal tooth mating surface 322 during steady-state operation of machine 300. For example, steady-state clearance as used herein and throughout the specification may range from approximately 0.127 cm to approximately 1.270 cm. First concave portion 324 of seal tooth mating surface 322 may have any profile that permits any clearance between seal tooth 316 and seal tooth mating surface 322 or may be configured for a non-steady-state clearance throughout first non-steady-state operation, e.g., a shut-down or temperature increasing, of machine 300. Second concave portion 326 of seal tooth mating surface 322 may have any profile that permits any clearance between seal tooth 316 and seal tooth mating surface 322 or may be configured for non-steady-state clearance throughout second non-steady-state operation, e.g., a shut-down or temperature decreasing, of machine 300. “Non-steady-state clearance” may include: sufficient clearance to substantially avoid rubbing between seal tooth 316 and first concave portion 324 during first non-steady-state operation, e.g., a shut-down or temperature increasing, of machine 300; and sufficient clearance to substantially avoid rubbing between seal tooth 316 and second concave portion 326 during second non-steady-state operation, e.g., a shut-down or temperature decreasing, of machine 300. For example, non-steady-state clearance as used herein and throughout the specification may range from approximately 0.381 cm to approximately 2.032 cm.
In an alternative embodiment, rotor 802 may include a first ancillary seal tooth mating surface 829 and a second ancillary seal tooth mating surface 832. Other embodiments may include a single ancillary seal tooth mating surface or more than two ancillary seal tooth mating surfaces. First ancillary seal tooth mating surface 829 include a first ancillary concave portion 830 for receiving first ancillary seal tooth 818 during first non-steady-state operation, e.g., a shut-down or temperature increasing, of machine 800. Second ancillary seal tooth mating surface 832 include a second ancillary concave portion 833 for receiving second ancillary seal tooth 819 during second non-steady-state operation, e.g., a shut-down or temperature decreasing, of machine 800. First ancillary concave portion 830 and second ancillary concave portion 833 may be concavely shaped relative to outer surface 831 of rotor 802 and relative to respective ancillary seal teeth 818, 819. Either or both ancillary concave portions 830, 833 may include any concave shape. First ancillary seal tooth mating surface 829 may also include a first ancillary plateau portion 831 for receiving the first ancillary seal tooth 818 during steady-state operation of machine 800. Second ancillary seal tooth mating surface 832 may include a second ancillary plateau portion 834 for receiving the second ancillary seal tooth 818 during steady-state operation of machine 800. Other embodiments may include more than two ancillary seal teeth. First ancillary seal tooth 818 may be adjacent to seal tooth 816. Second ancillary seal tooth 819 may be adjacent to seal tooth 816 and opposite first ancillary seal tooth 818.
Radially extending stationary component 808 with seal tooth 816 may include, for example, a nozzle, nozzle cover, and end packing ring. Each seal tooth 816 and first and second ancillary seal teeth 818, 819 may include, for example, a caulked J-strip, a steel strip, a machined integral tooth, an inserted tooth seal, and a brush seal. Plateau portion 828 of seal tooth mating surface 822 may include configuration for steady-state clearance between seal tooth mating surface 822 and at seal tooth 816. First concave portion 824 of seal tooth mating surface 822 may have any profile that permits any clearance between seal tooth 816 and seal tooth mating surface 822 or may be configured for non-steady-state clearance throughout first non-steady-state operation, e.g., a shut-down or temperature increasing, of machine 800. Second concave portion 826 of seal tooth mating surface 822 may have any profile that permits any clearance between seal tooth 816 and seal tooth mating surface 822 or may be configured for non-steady-state clearance throughout second non-steady-state operation, e.g., a shut-down or temperature decreasing, of machine 800.
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.
