Patent Publication Number: US-2012027573-A1

Title: Seal teeth for seal assembly

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a seal assembly, and more particularly to a seal assembly including seal teeth having protrusions to reduce swirl and leakage in rotary machines. 
     Ideally, a rotary machine, such as a turbine, consists of a rotating component positioned within a stationary component. The fluid path inside the rotary machine consists of a primary fluid path and a secondary fluid path. Fluid leakage, either into the primary fluid path from the secondary fluid path or out of the primary fluid path into the secondary fluid path, may adversely affect the operating efficiency of the turbine. In order to minimize leakage, seal assemblies, such as labyrinth seals, typically including arcuate packing rings, are placed between the stationary component and the rotary components of the turbine. 
     These labyrinth seals conventionally include a plurality of axially spaced, circumferentially extending seal teeth that are used to reduce leakage in the rotary machine. 
     In operation, with high rotor rotational velocity, fluid axially entering the fluid path of a rotary machine can acquire a significant tangential velocity component (also called “steam swirl”). For example, as the fluid moves through the labyrinth seal, the fluid may flow between the axially spaced seal teeth and circumferentially around the rotating component. This causes the fluid to acquire the significant tangential velocity component, which can induce rotor instabilities in turbomachines. The magnitude of this rotor instability is a function of the circumferential flow component of fluid within the labyrinth seal. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A first aspect of the invention provides a seal assembly for a rotating element, the seal assembly comprising: a plurality of arcuate packing rings configured to form an annulus proximately surrounding the rotating element; and a plurality of radially and circumferentially extending seal teeth coupled to each of the plurality of arcuate packing rings, wherein at least one of the plurality of seal teeth includes a plurality of axially extending protrusions. 
     A second aspect of the invention provides a turbomachine comprising: a rotating element; a stationary component substantially surrounding the rotating element; and a seal assembly coupled to the stationary component, the seal assembly including: a plurality of arcuate packing rings configured to form an annulus proximately surrounding the rotating element; and a plurality of radially and circumferentially extending seal teeth coupled to each of the plurality of arcuate packing rings, wherein at least one of the plurality of seal teeth includes a plurality of axially extending protrusions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  shows a partial cross-sectional view of machine according to an embodiment of the invention. 
         FIG. 2  shows a partial perspective view of a seal assembly according to an embodiment of the invention. 
         FIG. 3  shows a partial cross-sectional view of a seal assembly according to an embodiment of the invention. 
         FIG. 4  shows a partial perspective view of a seal assembly according to an embodiment of the invention. 
         FIG. 5  shows a partial perspective view of a seal assembly according to an embodiment of the invention. 
         FIG. 6  shows a partial perspective view of a seal assembly according to an embodiment of the invention. 
     
    
    
     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. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning to  FIG. 1 , a partial cross-sectional view of a machine  100  according to an embodiment of the invention is shown. Although  FIGS. 1-6  are shown with respect to a steam turbine, it is understood that the teachings of the various embodiments of the invention may be similarly applied to other turbomachines and that a steam turbine is merely used as an example of one type of turbomachine to describe the aspects of the invention. 
     Machine  100  may include a rotating element  120  and a stationary component  130 . Stationary component  130  may substantially surround rotating element  120 . Machine  100  may also include a seal assembly  150  coupled to stationary component  130 . As shown, seal assembly  150  may be coupled to stationary component  130  by fitting a mounting portion  151  of an arcuate packing ring  152  within a groove  132  of stationary component  130 . 
     Referring now to  FIG. 2 , partial perspective view of a seal assembly  150  according to an embodiment of the invention is shown. Seal assembly  150  may include a plurality of arcuate packing rings  152  (only one shown). Arcuate packing rings  152  may be configured to form an annulus that proximately surrounds rotating element  120  ( FIG. 1 ). Seal assembly  150  may include a plurality of seal teeth  154  coupled to each arcuate packing ring  152 . Plurality of seal teeth  154  may be coupled to each arcuate packing ring  152  according to any now known or later developed manner, such as, but not limited to, embedded, caulked, or machined. Plurality of seal teeth  154  may extend in a radial direction towards rotating element  120  ( FIG. 1 ) and also in a circumferential direction around rotating element  120  ( FIG. 1 ), such that plurality of seal teeth  154  may seal against flow leakage that may be present along machine  100  ( FIG. 1 ). At least one seal tooth  155  of plurality of seal teeth  154  may include a plurality of protrusions  156  that extend along seal tooth  155  in the axial direction of rotating element  120  ( FIG. 1 ) in order to reduce the rotor induced swirl and leakage between each of the plurality of seal teeth  154 , circumferentially around rotating element  120  ( FIG. 1 ), such that at least one seal tooth  155  is profiled. 
     Referring now to  FIG. 3 , a cross-sectional view of seal assembly  150  according to an embodiment of the invention is shown. Each seal tooth of plurality of seal teeth  154  may extend to either a first radial height (R 1 ) or a second radial height (R 2 ) in the radial direction towards rotating element  120 . First radial height (R 1 ) may be greater than second radial height (R 2 ), such that plurality of seal teeth  154  form a hi/lo seal teeth configuration. Alternatively, R 1  and R 2  may be of the same radial height. At least one seal tooth  155  of plurality of seal teeth  154  may include a plurality of protrusions  156  that extend along seal tooth  155  in the axial direction of rotating element  120  in order to reduce the rotor induced swirl and leakage between each of the plurality of seal teeth  154 , circumferentially around rotating element  120 . At least one seal tooth  155  that includes plurality of protrusions  156  may include first radial height (R 1 ). As shown in  FIG. 3 , each seal teeth  154  that includes first radial height (R 1 ) may include plurality of axially extending protrusions  156 . 
     Although plurality of protrusions  156  are shown to extend in one axial direction of rotating element  120  (towards the right in  FIG. 3 ), it is understood that plurality of protrusions  156  may extend in the opposite axial direction of rotating element  120  (towards the left in  FIG. 3 ). Alternatively, plurality of protrusions  156  may extend in both axial directions of rotating element  120  (towards the right and the left in  FIG. 3 ) in an alternating pattern. 
     Plurality of axially extending protrusions  156  may be configured to be any shape that prevents fluid from circumferentially flowing, between each of the plurality of seal teeth  154 , around rotating element  120 . As shown in  FIGS. 2-3 , plurality of axially extending protrusions  156  may be a substantially square shape. However, plurality of axially extending protrusions  156  may also be substantially semi-circular shape ( FIG. 4 ) or a substantially triangular shape ( FIG. 5 ). Further, plurality of axially extending protrusions  156  may form a substantially continuous sinusoidal surface ( FIG. 6 ), such as a waveform. Although plurality of axially extending protrusions  156  are shown as substantially continuous, it is understood that the sinusoidal surface may be intermittent. Alternatively, plurality of axially extending protrusions  156  may include a combination of different shapes. 
     As mentioned above, seal assembly  150  may be configured to form an annulus that proximately surrounds rotating element  120 . Referring back to  FIG. 1 , seal assembly  150  may proximately surround any portion of rotating element  120  that requires leakage prevention and swirl reduction. For example, seal assembly  150  may proximately surround rotor  120 . Alternatively, seal assembly  150  may proximately surround bucket assembly  124  to reduce bucket tip leakage and swirl. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. 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 various embodiments of the present 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 various embodiments of the present 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.