Patent Publication Number: US-11391377-B2

Title: Hydraulic seal

Description:
RELATED APPLICATION 
     This application claims priority to India Patent Application Serial Number 201911046563, filed on Nov. 15, 2019, the entirety of which is incorporated by reference herein. 
     BACKGROUND 
     Segmented carbon radial or circumferential seals are known. Such seals are commonly used to provide a fluid seal between a rotating component, such as a shaft, and a non-rotating component. Many aircraft and industrial gas turbines apply circumferential segmented seals in severe environment applications requiring high reliability and long life. Segmented carbon seals are also used as barrier seals in industrial compressors. Such seals are ideal in applications where long axial movements are anticipated due to thermal or mechanical phenomena usually found in today&#39;s rotor-machinery systems. In some implementations, hydrodynamic arrangements are machined into the carbon element of the seal. However, as the carbon element is the wear element in the seal assembly, the hydrodynamic arrangements begin to disappear which can have a negative effect on hydrodynamic performance. 
     SUMMARY 
     A segment of a seal assembly for sealing against a rotating member is disclosed. The segment can include a main body extending between first and second sides and defining a radial outer surface and a radial inner surface for sealing against the rotating member and can include a first transverse groove defined in the main body, the first transverse groove being for maintaining a pressure around portions of the segment. The segment can further include a hydrodynamic arrangement including a primary pad defining a portion of the main body radial inner surface and being located at or in proximity to the first transverse groove, and can further include a secondary pad defined within the main body, at least a portion of which being located radially between the primary pad and the radial outer surface. 
     In some examples, when the segment radial inner surface is in an initial unworn state, the secondary pad is concealed radially behind a plateau surface of the radial inner surface. 
     In some examples, when the segment radial inner surface is in a subsequent worn state, a portion of the plateau surface is worn away to expose at least a portion of the secondary pad such that the secondary pad defines a portion of the radial inner surface. 
     In some examples, the secondary pad extends through the main body first side. 
     In some examples, the secondary pad extends from a first end to a second end, wherein the first end is close to the radial inner surface in comparison to the second end. 
     In some examples, the segment can include a second transverse groove defined in the main body, wherein the second pad is located between the first and second transverse grooves. 
     In some examples, the primary pad includes a ramped portion. 
     In some examples, the primary pad includes a scooping groove between the ramped portion and the transverse groove. 
     In some examples, the at least one hydrodynamic feature includes a plurality of hydrodynamic features. 
     A segment of a seal assembly for sealing against a rotating member can include a main body extending between first and second sides and defining a radial outer surface and a radial inner surface for sealing against the rotating member, a plateau surface defining a portion of the radial inner surface, and a first transverse groove defined in the main body, the first transverse groove defining a portion of the radial inner surface and being for maintaining a pressure around portions of the segment. The segment can further include a hydrodynamic arrangement including a primary pad defining a portion of the main body radial inner surface and being located at or in proximity to the first transverse groove, and can further include a secondary pad defined within the main body and located between the plateau surface and the radial outer surface, the secondary pad being radially concealed behind the plateau surface. 
     In some examples, the segment radial inner surface is in a subsequent worn state, a portion of the plateau surface is worn away to expose at least a portion of the secondary pad such that the secondary pad defines a portion of the radial inner surface. 
     In some examples, the secondary pad extends through the main body first side. 
     In some examples, the secondary pad extends from a first end to a second end, wherein the first end is close to the radial inner surface in comparison to the second end. 
     In some examples, the segment further includes a second transverse groove defined in the main body, wherein the second pad is located between the first and second transverse grooves. 
     In some examples, the primary pad includes a ramped portion. 
     In some examples, the primary pad includes a scooping groove between the ramped portion and the transverse groove. 
     In some examples, the at least one hydrodynamic feature includes a plurality of hydrodynamic features. 
     A seal assembly can include, optionally, a flange assembly defining an annulus for receiving a rotating component and a plurality of segment received into the flange to define an annulus for receiving and forming a seal with a rotating component. Each of the segments can include a main body extending between first and second sides and defining a radial outer surface and a radial inner surface for sealing against the rotating member, a plateau surface defining a portion of the radial inner surface, and a first transverse groove defined in the main body, the first transverse groove defining a portion of the radial inner surface and being for maintaining a pressure around portions of the segment. The segment can further include a hydrodynamic arrangement including a primary pad defining a portion of the main body radial inner surface and being located at or in proximity to the first transverse groove, and can further include a secondary pad defined within the main body and located between the plateau surface and the radial outer surface, the secondary pad being radially concealed behind the plateau surface. 
     In some examples, for each segment, when the segment radial inner surface is in a subsequent worn state, a portion of the plateau surface is worn away to expose at least a portion of the secondary pad such that the secondary pad defines a portion of the radial inner surface. 
     In some examples, for each segment, the secondary pad extends through the main body first side. 
     In some examples, for each segment, the secondary pad extends from a first end to a second end, wherein the first end is close to the radial inner surface in comparison to the second end. 
     In some examples, for each segment, a second transverse groove is defined in the main body, wherein the second pad is located between the first and second transverse grooves. 
     In some examples, wherein, for each segment, the primary pad includes a ramped portion. 
     In some examples, wherein, for each segment, the primary pad includes a scooping groove between the ramped portion and the transverse groove. 
     In some examples, the at least one hydrodynamic feature includes a plurality of hydrodynamic features. 
     A variety of additional aspects will be set forth in the description that follows. The aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the examples disclosed herein are based. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the description, illustrate several aspects of the present disclosure. A brief description of the drawings is as follows: 
         FIG. 1  is a perspective view of a schematic representation of a hydrodynamic seal segment in accordance with the present disclosure, wherein the hydrodynamic seal is in an unworn state. 
         FIG. 2  is a perspective view of the hydrodynamic seal segment shown in  FIG. 1 , wherein the hydrodynamic seal is in a worn state. 
         FIG. 3  is a side view of the hydrodynamic seal segment shown in  FIG. 1 , wherein the hydrodynamic seal is in an unworn worn state. 
         FIG. 4  is a side view of the hydrodynamic seal segment shown in  FIG. 3 , wherein the hydrodynamic seal is in a worn state. 
         FIG. 5  is a top view of the hydrodynamic seal segment shown in  FIG. 1 , wherein the hydrodynamic seal is in an unworn worn state. 
         FIG. 6  is a top view of the hydrodynamic seal segment shown in  FIG. 3 , wherein the hydrodynamic seal is in a worn state. 
         FIG. 7  is an enlarged side view of a portion of the hydrodynamic seal segment shown in  FIG. 1 . 
         FIG. 8  is an enlarged side view of a portion of the hydrodynamic seal segment shown in  FIG. 1 . 
         FIG. 9  is a cross-sectional perspective view of the hydrodynamic seal segment shown in  FIG. 1 . 
         FIG. 10  is a schematic representation of a circumferential segmented seal assembly within which multiples of the hydrodynamic seal segment of  FIG. 1  may be used. 
         FIG. 11  is a schematic representation of a plurality of seal segments of the assembly shown in  FIG. 10 . 
         FIG. 12  is a schematic cross sectional view of the seal assembly shown in  FIG. 3  in an installed application with a rotating shaft. 
     
    
    
     DETAILED DESCRIPTION 
     Various examples will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various examples does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible examples for the appended claims. Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures. 
     Referring to  FIGS. 1 to 9 , a segment  100  of a seal assembly  10  for sealing against a rotating member is disclosed. The segment  100  may be used in a seal assembly of the type shown and described in U.S. Pat. No. 7,770,895, the entirety of which is incorporated by reference herein. The segment  100  may be used in a circumferential segmented seal assembly  10 , as shown at  FIGS. 10 to 12 . In one aspect, the circumferential seal assembly  10  is shown as including a plurality of adjacently arranged segments  100  supported by a flange assembly  12 . With continued reference to  FIGS. 10 to 12 , it can be seen that the seal assembly  10  defines an annulus  10   a  through which a shaft  14  can extend such that the segments  100  are oriented about the shaft  14  to provide a seal. 
     In one aspect, the segment  100  includes an arc-shaped main body  102  extending between first and second sides  102   a ,  102   b  and extending between a first and second ends  102   c ,  102   d . In one example, the main body  102  is formed from a material including carbon. The first and second ends  102   c ,  102   d  are oriented at an angle to each other such that multiple segments can be combined to form a ring. Accordingly, the angular range defined between the first and second ends  102   c ,  102   d  will typically be a multiple of 360°, such as 72°, 90°, 120°, or 180°. In the example shown at  FIGS. 10 and 11 , three segments  100  are provided that each form a 120° (θ 1 , θ 2 , θ 3 =120° segment of a seal ring. Additionally, the segments  100  may include cooperating features  112 ,  114  intended to overlap or interconnect with an adjacent segment, as is depicted at  FIG. 11 . The main body  102  is further shown as defining a radial or circumferential outer surface  102   e  and a radial or circumferential inner surface  102   f.    
     In one aspect, the radial inner surface  102   f  of each segment  100  is defined by one or more hydrodynamic arrangements  105  for facilitating sealing by controlling hydrodynamic fluid flow. For example, and schematically as shown at  FIGS. 10 and 11 , each of the segments  100  is provided with four such hydrodynamic arrangements  105 , for a total of twelve hydrodynamic arrangements  105 . It is noted that the segment  100  shown at  FIGS. 1 to 9  shows only a single hydrodynamic arrangement  105  for the purpose of clarity. A segment  100  can be provided with a single hydrodynamic arrangement  105  or any number of desired arrangements  105 . 
     In one aspect, each hydrodynamic arrangement  105  includes lift augmentation devices or primary pads  106  provided between a pair of transverse grooves  104 . Each segment  100  is also shown as including peripheral grooves or flow channels  102   g  extending from the radial inner surface  102   f  towards the radial outer surface  102   e  between the first and second ends  102   c ,  102   d . In the example shown, the grooves or flow channels  102   g  form a continuous, ring-shaped annular channel once the segments  100  are joined to form a ring. As shown, the transverse grooves  104 , which are spaced apart from each other, are generally semi-circular shaped and extend between the main body first side  102   a  to the flow channel  102   g . In one aspect, the length of the transverse grooves  104  is orthogonal or transverse to the first and second sides  102   a ,  102   b.    
     In one aspect, the primary pad  106  extends between the transverse grooves  104 , the first side  102   a , and the flow channel  102   g . As shown, the primary pad  106  can include a scooping groove  106   a  adjacent one of the transverse grooves  104 , a ramped portion  106   b  extending towards the scooping groove  106   a , and a transition portion  106   c  connecting the scooping groove  106   a  and the ramped portion  106   b . In one aspect, the ramped portion  106   b  defines a channel or groove in the radial inner surface  102   f  that deepens as the ramped portion  106   b  progresses towards the scooping groove  106   a  and the proximate transverse groove  104 . At the transition portion  106   c , the scooping groove  106   a  begins and deepens at a greater rate than the ramped portion  106   b  as the scooping groove  106   a  eventually intersects with the proximate transverse groove  104 . The remaining surface portions of the radial inner surface  102   f  not defining the transverse grooves  104 , flow channel  102   g , and the primary pad  106  can be characterized as a plateau surface  108  that generally defines a surface with a curvature generally matching that of the rotating component to be sealed by the segment  100 . In one aspect, the plateau surface  108  corresponds to a bore side of the segment  100  and provides a sealing surface against a rotating member, such as a shaft or runner. As such, the plateau surface  108  can be characterized as defining a sector of a hollow cylinder with the plateau surface  108  defining the inner radial surface of the sector. The plateau surface  108  can be therefore characterized as a concave surface, an inner circumferential surface, and/or an inner radial surface. In one aspect, the plateau surface  108  has a first portion  108   a  extending along a first side of the flow channel  102   g  and a second portion  108   b  extending along a second side of the flow channel  102   g . Each of the first and second portions  108   a ,  108   b  has a matching radial surface curvature. 
     In operation, the radial inner surface  102   f  of the segment  100  will eventually wear such that the ramped portion  106   b  of the primary pad  106  will become shallower and therefore shorten over time.  FIG. 1  shows an unworn pad wherein the ramped portion  106   b  has an initial length  106 -L 1 , as measured from the adjacent transverse groove  104 .  FIG. 2  shows a worn pad, wherein the ramped portion has a length  106 -L 2 , also measured from the adjacent groove  104 , that is significantly shorter than the initial length  106 -L 2 . While the pad  106  is designed to account for some wear, performance of the pad is decreased over time due to such wear. To offset or mitigate this decrease in performance, the segment  100  is additionally provided with a secondary pad  110  that is initially concealed behind the plateau surface  108  and only becomes active or exposed once the plateau surface  108  has worn to a predetermined degree. 
     Referring back to  FIG. 1 , the secondary pad  110  is shown as extending from a first end  110   a  to a second end  110   b , generally located between the transverse grooves  104 . In one aspect, the secondary pad  110  has a radial outer wall surface  110   c  and a spaced apart radial inner wall surface  110   d  that extends from the segment main body first side  102   a  towards the second side  102   b  to a depth generally matching that of the ramped portion  106 . In an unworn state, the secondary pad  110  is spaced from and concealed behind the plateau surface  108  such that a portion of the secondary pad  110  is located between the plateau surface  108  and the radial outer surface  102   e  and such that a portion of the secondary pad  110  is located between the primary pad  106  and the radial outer surface  102   e . Accordingly, the secondary pad  110  can be characterized as being concealed, dormant, or hibernating when the segment  100  is in an unworn state. In examples, the surfaces  110   c  and/or  110   d  of the secondary pad  110  are oriented in a non-parallel or oblique angle to the plateau surface  108 . In examples, the angle between the plateau surface  108  and the secondary pad  110 , is an acute angle. In examples, the angle between the plateau surface  108  and the secondary pad  110  is less than 10 degrees. In examples, the surfaces  110   c  and/or  110   d  of the secondary pad  110  are oriented such that the first end  110   a  is closer to the plateau surface in comparison to the second end  110   b . Accordingly, as the plateau surface  108  wears, the first end  110   a  of the secondary pad  110  will be initially exposed such that the radial inner wall surface  110   d  is worn away to expose the radial exterior wall surface  110   d  to the radial inner surface  102   f . As wear continues, an increasing length of the secondary pad  110  being exposed towards the second end  110   b . In examples, a portion of the secondary pad  110  is located between the primary pad  106 , in an unworn state, and the circumferential outer surface  102   e  of the seal segment  100 . In examples, a majority of the overall length of the secondary pad  110  is located between the primary pad  106 , in an unworn state, and the circumferential outer surface  102   e  of the seal segment  100 . 
     Referring to  FIG. 2 , sufficient wear through the plateau surface  108  has occurred such that a length  110 -L 1  of the secondary pad  110  is exposed. This length  110 -L 1  is able to replace at least a portion of the primary pad length  106 -L 1  that has been lost due to the same wear. Accordingly, once exposed, the secondary pad  110  is able to regain some of the hydrodynamic performance losses due to the wear of the primary pad  106 . As most easily viewed at  FIG. 7 , the radial inner wall  110   d  can include a first segment  110   e  extending from the first end  110   a  and can include an adjoining second segment  110   f  extending at a non-zero angle from the first segment  110   e  to the second end  110   b . In the example shown, the segment  110   e  is generally parallel to the plateau surface  108  while the segment  110   f  is generally parallel to the outer radial outer wall surface  110   c . Accordingly, when the plateau portion  108  wears sufficiently, the segment  110   e  will erode away such that the secondary pad  110  is exposed with a predetermined initial length. In the example shown, the predetermined length is defined by the length of the segment  110   e , which is shown as being equal to length  110 -L 1 . As the plateau surface  108  wears further, the length of the secondary pad  110  will continue to increase from the predetermined length as the primary pad length continues to decrease. In examples, half or more of the radial inner wall surface  110   d  is parallel to the radial outer wall surface  110   c . In some examples, the entire length of the radial inner wall surface  110   d  is parallel to the radial outer wall surface  110   c . In some examples, the length  110 -L 1  is less than half the length  106 -L 1 . In some examples, the length  110 -L 1  is about one quarter of the length  106 -L 1 . In examples, the overall length of the secondary pad  110  is a half or more the overall length of the primary pad  106 . In examples, the overall length of the secondary pad  110  is about the same as the overall length of the primary pad  106 . 
     In operation, a seal assembly  10  of the general type shown schematically at  FIG. 11 , with a plurality of hydrodynamic arrangements  5 , will provide a suitable hydrodynamic performance level when the primary pads  106  are in a completely unworn state. This performance level drops as the carbon of the primary pads wear  106 . As the secondary pads  110  are completely hidden beneath the plateau surface  108  in the unworn state, the primary pads  106  operate as normal with no performance losses being caused by the secondary pads  110 . As the carbon of the segments  100  wear to expose the secondary pads  110 , the secondary pads  110  become active and begin to provide extra hydrodynamic performance to regain losses from the continually wearing primary pads  106 . Accordingly, the disclosure provides for an advantageous approach in which a performance level of a seal assembly  10  is maintained at a higher level over a greater period of time, as compared to prior art designs not including a secondary pad of the type disclosed herein. 
     From the forgoing detailed description, it will be evident that modifications and variations can be made in the aspects of the disclosure without departing from the spirit or scope of the aspects. While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.