Patent Publication Number: US-2018045316-A1

Title: Hydrodynamic seal seat cooling features

Description:
BACKGROUND 
     The present disclosure relates to hydrodynamic seals and more particularly, to cooling features in a hydrodynamic seal seat. 
     Hydrodynamic seals are used in various applications, including for sealing a bearing cavity, in which cooling lubricant is present, from other components of a gas turbine engine. A hydrodynamic seal includes a nonrotating seal assembly, a rotating seal seat, and a fluid bearing surface that forms between the nonrotating seal assembly and rotating seal seat to provide a seal. The fluid bearing surface (also called an air film in some application) prevents other fluids, such as oil or another cooling lubricant, from flowing through the gap between the nonrotating seal assembly and the rotating seal seat while also reducing wear on the sealing surfaces of the nonrotating seal assembly and the seal seat. Occasionally, the rotating seal seat can overcome the fluid bearing surface and contact the nonrotating seal assembly. Due to friction, such contact causes heat to be generated within the seal seat and increases the temperature of the seal seat. While attempts have been made to mitigate the heat with the introduction of cooling lubricant at a side of the seal seat opposite the side in contact with the nonrotating seal assembly, the cooling lubricant only provides localized cooling relief on the noncontacting side of the seal seat. 
     SUMMARY 
     A seal seat includes a base having an annular shape, a neck having an annular shape and being radially outward from the base with the neck having an axial length that is less than an axial length of the base, and a head having an annular shape and being radially outward from the neck with the head having and outer end, a sealing surface, and an axial length that is greater than the axial length of the neck. The seal seat also includes a notch adjacent to the neck formed by the base, neck, and head and a plurality of cooling lubricant passages with each passage of the plurality of cooling lubricant passages extending from the notch to a point on the outer end of the head. The plurality of cooling lubricant passages are configured to allow cooling lubricant to flow from the notch to the outer end of the head. 
     A seal includes a nonrotatable seal assembly and a rotatable seal seat with the seal seat being annular and having a radially inner end, a radially outer end, a sealing surface on an axially first side adjacent to the seal assembly, a notch in an axially second side, and cooling lubricant channels extending from the notch to the radially outer end. 
     A hydrodynamic seal in a gas turbine engine includes a seal assembly that is nonrotatable and has a housing, a carrier, a resilient member between the housing and the carrier, and a seal block attached to the carrier. The hydrodynamic seal also includes a seal seat that is annular, rotatable, and configured to attach to a rotatable shaft with the seal seat having a first side and a second side. The seal seat includes a base, a neck connected to and radially outward from the base, a head connected to and radially outward from the neck with the head having a sealing surface on the first side that is adjacent to the seal block of the seal assembly, a first notch in the neck on the second side of the seal seat, and lubricant passages extending from the first notch to an outer end of the head with each of the lubricant passages extending to a point on the outer end of the head near the sealing surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional elevation view of a hydrodynamic seal. 
         FIG. 1B  is a perspective view of a seal seat. 
         FIG. 2  is a cross-sectional elevation view of a second embodiment of a hydrodynamic seal. 
         FIG. 3  is a plan view of an embodiment of a seal seat. 
         FIG. 4  is a plan view of another embodiment of the seal seat. 
         FIG. 5  is a cross-sectional elevation view of another embodiment of a hydrodynamic seal. 
     
    
    
     DETAILED DESCRIPTION 
     A hydrodynamic seal is disclosed herein that includes a seal seat with a plurality of cooling lubricant passages. The hydrodynamic seal can provide a seal to enclose a compartment, such as a bearing compartment, to prevent fluids within the compartment from escaping. The hydrodynamic seal includes a stationary seal assembly that has a seal housing, a carrier, a resilient member, and a seal block. The hydrodynamic seal also includes a rotatable seal seat configured to attach to a shaft, such as a main shaft in a gas turbine engine. The seal seat has a base, a head, and a neck between the base and the head. The neck includes a notch into which a nozzle dispenses cooling lubricant. During operation, a fluid bearing surface, such as an air film, is formed between the seal block and a sealing surface on the head, forming a seal that prevents the cooling lubricant or other fluids from flowing through while also limiting the amount of friction between the stationary seal assembly and the rotating seal seat. Occasionally, the seal seat can contact the seal block, causing heat in the seal seat due to friction between the rotating seal seat and the nonrotating seal block. To mitigate that heat, the seal seat includes a plurality of cooling lubricant passages that extend from the notch in the neck to an outer end of the head. The plurality of cooling lubricant passages allows cooling lubricant, such as oil, to flow from the notch (which is supplied with cooling lubricant by the nozzle), through the seal seat, and out corresponding openings in the head. Further, the seal seat can include a cooling lubricant dam extending radially inward from the head into the notch in the neck. The cooling lubricant dam helps prevent cooling lubricant, which can pool on a radially outer surface of the notch due to the rotation of the seal seat, from flowing out of the notch other than through the plurality of cooling lubricant passages, increasing the efficiency of the hydrodynamic seal by limiting the amount of cooling lubricant that is dispensed into the notch. 
     The seal seat with the plurality of cooling lubricant passages and the cooling lubricant dam has many advantages. The plurality of cooling lubricant passages allows cooling lubricant to flow through the seal seat, reducing the temperature and likelihood of damage to the seal seat. The number, orientation, and exit point of each passage of the plurality of cooling lubricant passages can be varied depending on the cooling needs of the seal seat, the material used to construct the seal seat, the manufacturing process utilized in constructing the seal seat, and other considerations. If greater cooling is needed, each passage of the plurality of cooling lubricant passages can have a longer flow length and/or the number of passages can be increased. As mentioned above, the cooling lubricant dam increases the efficiency of the hydrodynamic seal by limiting the amount of cooling lubricant that is dispensed into the notch to cool the seal seat. After reviewing the description and corresponding figures below, these and other benefits will be realized. 
       FIG. 1A  is a cross-sectional elevation view of a hydrodynamic seal, and  FIG. 1B  is a perspective view of a seal seat. Hydrodynamic seal  110  includes seal assembly  112 , seal seat  114 , and nozzle  116 . Seal assembly  112  includes housing  118 , resilient member  120 , carrier  122 , and seal block  124 . Seal seat  114 , which is rotatable about centerline C, includes base  126  at inner end  128 , neck  130  with first notch  132  and second notch  134 , head  136  at outer end  138 , and a plurality of cooling lubricant passages  140 . Head  136  has coating  142  on sealing surface  144  with sealing surface  144  being on a first axial side of seal seat  114  adjacent to seal block  124 . The plurality of cooling lubricant passages  140  have first portion  146  and second portion  148 . During operation, fluid bearing surface  150  is present between seal block  124  and sealing surface  144  of head  136 . 
     Hydrodynamic seal  110  has the same functionality as other hydrodynamic seals known in the art. Hydrodynamic seal  110  is substantially annular about centerline C, and can be centered about a rotating shaft, such as a main shaft of a gas turbine engine. 
     Seal assembly  112  of hydrodynamic seal  110  is stationary/nonrotating, annular, and centered about centerline C. Seal assembly  112  functions to ensure seal block  124  is adjacent to sealing surface  144  of head  136  (with fluid bearing surface  150  between seal block  124  and sealing surface  144  when hydrodynamic seal  110  is functioning properly). The configuration and functionality of seal assembly  112  is known to one of ordinary skill in the art, and the disclosed seal assembly  112  is only one exemplary embodiment. 
     Housing  118  of seal assembly  112  is a structural member to which resilient member  120  connects. Housing  118  is annular in shape having an outer substantially cylindrical portion  119 A and arm  119 B that extends inward to form a disk-like shape. Housing  118  provides a stationary and structural member to which the other components of seal assembly  112  can attach to remain stationary and nonrotating. Housing  118  can be made from a variety of materials, but should be constructed from a material that has sufficient strength and rigidity to support the other components of seal assembly  112 . While housing  118  is shown in  FIG. 1A  as having cylindrical portion  119 A and the disk-like arm  119 B, housing  118  can have other configurations to provide increased strength and/or allow resilient member  120  and other components to attach thereto. 
     Resilient member  120  is a spring or another resilient component that is between housing  118  and carrier  122 . Resilient member  120  can be annular in shape to extend completely around the annular seal assembly  112  or can be one or more individual components, such as multiple springs, that are arranged around seal assembly  112 . Resilient member  120  can elongate and shorten in an axial direction to ensure seal block  124  remains adjacent to the first axial side of seal seat  114  (with fluid bearing surface  150  between seal seat  114  and seal block  124 ). Resilient member  120  can be made from a variety of materials, including a resilient metal, rubber, or a composite material. 
     Carrier  122  is connected to resilient member  120  on one axial side and to seal block  124  on the other axial side. Carrier  122  is annular in shape with inner cylindrical portion  123 A, outer cylindrical portion  123 B axially rear of inner cylindrical portion  123 A, and disk-like arm  123 C extending between an axially rearmost end of inner cylindrical portion  123 A and an axially forwardmost end of outer cylindrical portion  123 B. Carrier  122  can have additional components that extend in a radial outward direction away from centerline C to provide a barrier between a bearing cavity (in which cooling lubricant is present) and other components of a system in which hydrodynamic seal  110  is present, such as a gas turbine engine. Carrier  122  can be made from a variety of materials, including carbon, metal, or a composite material, and can be one continuous and monolithic piece or constructed from a number of pieces fastened together. 
     Seal block  124  is connected to carrier  122  and provides a seal between seal assembly  112  and seal seat  114 . Seal block  124  is annular in shape and can have a square or rectangular cross-section or, as shown in  FIG. 1A , have a portion adjacent seal seat  114  (i.e., adjacent to sealing surface  144  on the first axial side of seal seat  114 ) that has less thickness in a radial direction than a portion adjacent carrier  122 . Seal block  124  can be made from a variety of materials, including carbon, metal, or a composite material, but should be constructed from a material that allows air or another fluid that forms fluid bearing surface  150  (and thus forms a seal between seal block  124  and seal seat  114 ) to establish a tight seal. A surface of seal block  124  adjacent fluid bearing surface  150  and seal seat  114  can be coated with a material and/or have a desired surface topography that allows for a sufficient sealing surface and promotes the air or other fluid that flows through a gap between seal block  124  and seal seat  114  to establish a tight seal. 
     Seal seat  114  is in an axially rearward direction from seal assembly  112  such that the first axial side of seal seat  114  is at least partially adjacent to seal block  124 . Seal seat  114  is annular in shape and rotatable about centerline C. Seal seat  114  can be connected at inner end  128  to a shaft that is centered about centerline C, and the shaft can be a main shaft of a gas turbine engine or another type of engine. Further, seal seat  114  can be connected to a rotating member through other configurations, such as on an axially forward side (i.e., a first axial side) and/or on an axially rearward side (i.e., a second axial side) of base  126  of seal seat  114 . While shown having base  126 , neck  130 , and head  136 , seal seat  114  can have other configurations that function to work along with seal assembly  112  to form a hydrodynamic seal. Seal seat  114  can be constructed from multiple pieces that are fastened together, or seal seat  114  can be one continuous and monolithic component. 
     Base  126  of seal seat  114  is at a radially inner end  128  and provides structural support to the other components of seal seat  114 . Base  126  can have a substantially rectangular cross section or another configuration, and can have features that allow base  126  to be connected to another component, such as a rotatable shaft radially inward from base  126 . Base  126  can be fastened to the rotatable shaft through a variety of means, including welding, bolts, or other means. Inner end  128  of base  126  (and of seal seat  114 ) is substantially parallel to centerline C, but other embodiments can have an inner end that is another configuration to allow for base  126  to be connected to a shaft or another rotating structure. 
     Neck  130  is radially outward from base  126  and connects base  126  to head  136 . Neck  130  is annular in shape and can have an axial width that is the same as base  126  and head  136  or less than an axial width of base  126  and head  136  (as shown in  FIGS. 1A and 1B ) to form first notch  132  and second notch  134 . Neck  130  provides structural support to head  136  and can have a substantially rectangular cross section with fillets in transition areas between base  126  and neck  130  and between neck  130  and head  136  (to provide first notch  132  and second notch  134  with rounded/curved cross-sectional shapes). In other configurations, neck  130  can have another cross-sectional shape formed by first notch  132  and second notch  134 . 
     First notch  132  is an annular aperture that extends into seal seat  114  from the second axial side towards neck  130 , and second notch  134  is an annular aperture that extends into seal seat  114  from the first axial side (on an opposite side from first notch  132 ) towards neck  130 . First notch  132  and second notch  134  reduce the mass of seal seat  114  and can be configured to balance seal seat  114  to limit vibration, coning, and other issues that can occur during rotation of seal seat  114 . First notch  132  can extend into seal seat  114  a distance that is greater than, less than, or equal to the distance second notch  134  extends into seal seat  114 . As shown in  FIG. 1A , first notch  132  extends into seal seat  114  farther than second notch  134 . Also, first notch  132  can have a radial height that is greater than, less than, or equal to a radial height of second notch  134 . As shown in  FIG. 1A , the radial height of first notch  132  is equal to the radial height of second notch  134 . Additionally, first notch  132  can have a different radial distance from inner end  128  than a radial distance that second notch  134  is from inner end  128  (as shown in  FIG. 1A ), or first notch  132  and second notch  134  can be the same radial distance from inner end  128 . As shown in  FIG. 1A , first notch  132  is radially farther from inner end  128  than second notch  134 . Other embodiments of seal seat  114  can include configurations that do not include first notch  132  and/or second notch  134 . 
     Head  136  of seal seat  114  is at a radially outer end  138  and provides sealing surface  144  on the first axial side (i.e., forward axial side) to form a seal with seal assembly  112 . Head  136  can have a substantially rectangular cross section or another configuration, and can have features that allow head  136  to more easily and completely form a seal with seal assembly  112 . Head  136  can have an axial width that is the same as base  126  and neck  130 , greater than base  126  and neck  130  (as shown in  FIGS. 1A and 1B ), or less than one or both of base  126  and neck  130 . Sealing surface  144  of head  136  is adjacent to seal block  124  of seal assembly  112  with fluid bearing surface  150  between seal block  124  and head  136  when hydrodynamic seal  110  is properly operating. Sealing surface  144  can have coating  142  to provide a surface that allows for sufficient sealing and promotes the air or other fluid that flows through the gap between seal block  124  and sealing surface  144  to establish a tight seal. Coating  142  can be a variety of materials, including a hard coating or another material designed to provide a surface for establishing a seal. Further, coating  142  and/or sealing surface  144  can have a surface topography that allows for sufficient sealing. Coating  142  can cover the entire surface of sealing surface  144  or, as shown in  FIG. 1A , can cover only a portion of sealing surface  144 . 
     The plurality of cooling lubricant passages (also referred to as channels)  140  extend substantially within head  136  and partially within neck  130  from first notch  132  to outer end  138 . Each passage of the plurality of cooling lubricant passages  140  include first portion  146  that extends in a substantially axial direction from first notch  132  partially into neck  130  to a transition point in head  136  and second portion  148  that extends from the transition point to a point on outer end  138  adjacent sealing surface  144  (i.e., a point near where outer end  138  intersects sealing surface  144 ). 
     First portion  146  extends from first notch  132  at a point in neck  130  that is closer to head  136  than to base  126 , but other configurations can have first portion  146  that extends from first notch  132  at a point in neck  130  that is equidistant from base  126  and head  136  or closer to base  126 . However, first portion  146  can extend from first notch  132  at a point near where neck  130  and head  136  intersect/connect to better promote the flow of cooling lubricant into the plurality of cooling lubricant passages  140  because cooling lubricant will be forced towards a radially outward side of first notch  132  due to the rotation of seal seat  114 . First portion  146  can extend entirely in an axial direction, angle radially outward while extending in an axial direction, or extend entirely in a radial direction. The angle that first portion  146  extends can be between zero degrees and ninety degrees, with first portion  146  shown in  FIG. 1A  at an angle between zero degrees and thirty degrees (when measured from a line that is parallel to inner end  28  and centerline C). 
     Second portion  148  extends from first portion  146  to a point on outer end  138  that is near sealing surface  144 , but other configurations can have second portion  148  that extends to a point that is closer to the second axial side of head  136  (i.e., the axial rearward side of head  136  opposite sealing surface  144 ). Second portion  148  can extend at an angle that is entirely radial from the transition point at an end of first portion  146  to outer end  138  (as shown in  FIG. 1A ), angled axially forward towards the first axial side (i.e., towards sealing surface  144 ), or angled axially rearward towards the second axial side (i.e., away from sealing surface  144 ). Second portion  148  can extend to outer end  138  from the transition point at the end of first portion  146  at an angle that is entirely radial (i.e., no circumferential angle), an angle that is towards a direction of rotation of seal seat  114  (i.e., having a positive circumferential angle), or an angle that is away from a direction of rotation of seal seat  114  (i.e., having a negative circumferential angle). These different configurations will be described in greater detail with regards to  FIGS. 3 and 4 . The angle that second portion  148  extends can be between zero degrees and ninety degrees (when measured from a line that extends in an entirely radial direction perpendicular to centerline C). 
     The plurality of cooling lubricant passages  140  can have any number of passages, including a configuration that includes fifty or more passages. Also, the cross-sectional flow area of each passage can have a variety of shapes, including a circular cross section, an oval cross section, a square or rectangular cross section, or another shape. The diameter of each passage of the plurality of cooling lubricant passages  140  can be a variety of sizes, including a passage that is greater than 0.152 centimeters (0.06 inches). Depending on the cooling needs of seal seat  114 , the number of passages, a length of each passage, and cross-sectional flow area can be varied to provide for more cooling lubricant to flow through the plurality of cooling lubricant passages  140  and to provide for a greater surface area for heat exchange between seal seat  114  and the cooling lubricant. The configuration of each passage can vary between each passage and adjacent passages, such as a passage having a different diameter or shape than adjacent passages. A circumferential distance between adjacent passages of the plurality of cooling lubricant passages  140  can be constant (i.e., passages are equidistant from adjacent passages in a circumferential direction) such that the plurality of cooling lubricant passages  140  are equally spaced around the entire circumference of seal seat  114 , or the circumferential distance between adjacent passages of the plurality of cooling lubricant passages  140  can be varied (i.e., adjacent passages are a different circumferential distance away) depending on design considerations. The plurality of cooling lubricant passages  140  can be formed through a variety of methods, including machining, additive manufacturing, electrical discharge machining, and/or electrochemical machining. 
     During normal operation of hydrodynamic seal  10 , air or another fluid is provided into the gap between seal block  124  and sealing surface  144  of head  136  to produce fluid bearing surface  150 , which seals the gap and prevent cooling lubricant and/or other fluids from flowing through the gap. However, often times during operation, seal seat  114  may temporarily move in an axial direction to contact seal block  124  (such that part of all of fluid bearing surface  150  is not present between seal block  124  and sealing surface  144  of head  136 ). The contact between seal block  124  and head  136  causes heat to be generated within seal block  124  and head  136  due to friction between the rotating seal seat  114  and the nonrotating seal assembly  112 . If not mitigated, the heat can cause damage to head  136  and other components of seal seat  114 . To prevent the buildup of heat within head  136 , cooling lubricant, which is dispensed into first notch  132  by nozzle  116 , is allowed to flow through the plurality of cooling lubricant passages  140  and out of seal seat  114  at outer end  138 . Heat is transferred between head  136  and the cooling lubricant that is flowing through the plurality of cooling lubricant passages  140 . After flowing out of the plurality of cooling lubricant passages  140 , the cooling lubricant can be collected and recycled. With heat transfer occurring around the plurality of cooling lubricant passages  140  within head  136 , the change in thermal gradient is smaller than if the plurality of cooling lubricant passages  140  were not present. The thermal gradient is smaller because a distance between sealing surface  144  where heat generation occurs and an area where heat transfer is taking place (around the plurality of cooling lubricant passages  140 ) is shorter than if heat transfer was only occurring around first notch  132  where cooling lubricant is dispensed from nozzle  116 . 
       FIG. 2  is a cross-sectional elevation view of a second embodiment of a hydrodynamic seal. Hydrodynamic seal  210  includes seal assembly  212 , seal seat  214 , and nozzle  216 . Seal assembly  212  includes housing  218 , resilient member  220 , carrier  222 , and seal block  224 . Seal seat  214 , which is rotatable about centerline C, includes base  226  at inner end  228 , neck  230  with first notch  232  and second notch  234 , head  236  at outer end  238 , a plurality of cooling lubricant passages  240 , and cooling lubricant dam  252 . Head  236  has coating  242  on sealing surface  244  with sealing surface  244  being on a first axial side of seal seat  214  adjacent to seal block  224 . The plurality of cooling lubricant passages  240  have first portion  246  and second portion  248 . During operation, fluid bearing surface  250  is present between seal block  224  and sealing surface  244  of head  236 . Hydrodynamic seal  210  of  FIG. 2  is similar in configuration and functionality to hydrodynamic seal  110  of  FIGS. 1A and 1B , except that hydrodynamic seal  210  includes first portion  246  of the plurality of cooling lubricant passages  240  that extends entirely in an axial direction towards the first axial side and hydrodynamic seal  210  includes cooling lubricant dam  252 . 
     First portion  246  of the plurality of cooling lubricant passages  240  extends entirely in an axially forward direction towards first axial side so that second portion  248  extends from a transition point that is closer to sealing surface  144  to promote heat transfer. Because the transition point where first portion  246  and second portion  248  meet is closer to sealing surface  244 , second portion  248  extends a longer distance adjacent to sealing surface  244  than that in  FIG. 1A and 1B . As with hydrodynamic seal  110  of  FIGS. 1A and 1B , first portion  246  and second portion  248  can have other configurations. 
     Seal seat  214  includes cooling lubricant dam  252 , which is annular in shape and extends radially inward from head  236  into first notch  232 . Cooling lubricant dam  252  can have a rectangular cross section (as shown in  FIG. 2 ) or another cross-sectional shape, such as triangular or semicircular. Cooling lubricant dam  252  can extend a distance into first notch that is as much as half a distance between base  226  and head  236 , or a distance that is less than half the distance between base  226  and head  236 , such as a distance that is approximately  0 . 10  centimeters ( 0 . 04  inches). Cooling lubricant dam  252  can be a spiral lock ring, one continuous and monolithic piece with head  236 , or another configuration. 
     Cooling lubricant dam  252  helps prevent cooling lubricant within first notch  232  from flowing out of first notch  232  through an opening along the second axial side. Cooling lubricant dam  252  encourages the cooling lubricant to flow through the plurality of cooling lubricant passages  240 . During operation, seal seat  214  rotates, causing the cooling lubricant to be pushed radially outward onto a radially outer surface of first notch  232  (adjacent head  236 ). Cooling lubricant dam  252  provides a wall for the cooling lubricant to prevent the cooling lubricant from flowing out of first notch  232  towards nozzle  216 , and instead the cooling lubricant on the outer surface of first notch  232  can only flow into the plurality of cooling lubricant passages  240 , decreasing the loss of cooling lubricant into areas other than the plurality of cooling lubricant passages  240  and increasing the efficiency of hydrodynamic seal  210  by increasing the proportion of cooling lubricant within first notch  232  that flows through the plurality of cooling lubricant passages  240 . 
       FIG. 3  is a plan view of an embodiment of a seal seat. Seal seat  314  includes base  326  at inner end  328 , neck  330  with first notch  332 , head  336  at outer end  338 , and a plurality of cooling lubricant passages  340  having first portion  346  and second portion  348 . Seal seat  314  can also include a second notch and a sealing surface with a coating (not shown). During operation, seal seat  314  rotates in a direction of rotation R. Line L is a line that extends in a radial direction perpendicular to centerline C, and θ 1  is an angle measured from line L to second portion  348 , with second portion  348  angled in a circumferential direction. 
     Seal seat  314  is similar to seal seat  114  in  FIGS. 1A and 1B  in configuration and functionality. However, seal seat  314  shows angle θ 1  that second portion  348  extends in the circumferential direction when measured from line L, which is a line that extends in the radial direction from centerline C. Seal seat  314  as shown in  FIG. 3  has a plurality of cooling lubricant passages  340  that includes at least fifty passages, but other embodiments can include a number of the plurality of cooling lubricant passages  340  that is less than fifty passages with the passages having a larger or smaller diameter depending on design considerations. 
     As shown in  FIG. 3 , first portion  346  extends slightly radially outward as first portion  346  extends in an axially forward direction (i.e., into the page), similar to first portion  146  in  FIGS. 1A and 1B . Other embodiments of seal seat  314  can include a first portion of each passage of the plurality of cooling lubricant passages  340  that does not extend slightly radially outward (extends only in an axial direction as shown in  FIG. 2 ) or extends radially outward at a greater angle than that shown in the disclosed embodiments. 
     Second portion  348  extends at angle θ 1  that is between zero degrees and ninety degrees in the circumferential direction when measured from line L that extends in the radial direction from centerline L, with angle θ 1  as shown in  FIG. 3  at approximately sixty degrees. Second portion  346  extends at angle θ 1  that is towards direction of rotation R of seal seat  314 . With second portion  346  extending at angle θ 1  towards direction of rotation R, the cooling lubricant flowing within each passage of the plurality of cooling lubricant passages  340  will have a longer dwell time (i.e., the cooling lubricant will remain within each passage longer) than other configurations of second portion  346  because the forces caused by the rotation of seal seat  314  will push against the flowing cooling lubricant. Having a dwell time that is longer may be desired in some applications, such as when the difference in temperature between the cooling lubricant and seal seat  314  is large and less cooling lubricant is required to flow through the plurality of cooling lubricant passages  340  to cool seal seat  314 . 
     Second portion  348  of each passage can have the same angle θ 1  as adjacent passages or can have a different angle θ 1 . Additionally, first portion  346  and/or second portion  348  do not need to extend in a straight line, but rather can have one or multiple curves, zig-zags, or other configurations depending on the cooling needs of seal seat  314 . Further, first portion  346  can be configured to extend at least partially in the circumferential direction, and second portion  348  can be configured to extend at least partially in the axial direction. Each passage of the plurality of cooling lubricant passages  340  can be approximately equidistant from adjacent passages in a circumferential direction, or the passages can vary in circumferential distance from one another. 
       FIG. 4  is a plan view of another embodiment of a seal seat. Seal seat  414  includes base  426  at inner end  428 , neck  430  with first notch  432 , head  436  at outer end  438 , a plurality of cooling lubricant passages  440  having first portion  446  and second portion  448 , and cooling lubrication dam  452 . Seal seat  414  can also include a second notch and a sealing surface with a coating (not shown). During operation, seal seat  414  rotates in a direction of rotation R. Line L is a line that extends in a radial direction perpendicular to centerline C, and θ 2  is an angle measured from line L to second portion  448 , with second portion  448  angled in a circumferential direction. 
     Seal seat  414  is similar to seal seat  114  in  FIGS. 1A and 1B  and seal seat  314  in  FIG. 3  in configuration and functionality. However, seal seat  414  shows angle θ 2  that second portion  448  extends in the circumferential direction when measured from line L, which is a line that extends in the radial direction from centerline C, and second portion  448  of each passage of the plurality of cooling lubricant passages  440  extends at angle θ 2  that is away from direction of rotation R of seal seat  414 . Seal seat  414  as shown in  FIG. 4  has a plurality of cooling lubricant passages  440  that includes approximately fifty passages, but other embodiments can include a number of the plurality of cooling lubricant passages  440  that is less than fifty passages with the passages having a larger or smaller diameter depending on design considerations, or a number of the plurality of cooling lubricant passages  440  that is greater than fifty passages, such as a configuration that includes sixty or more passages. 
     In  FIG. 4 , openings of the plurality of cooling lubricant passages  440  in first notch  432  are blocked from view (and are therefore dotted lines) by cooling lubricant dam  452 , which extends into first notch  432  to prevent the cooling lubricant from flowing out of first notch  432  except through the plurality of cooling lubricant passages  440 . Similar to first portion  346  of the plurality of cooling lubricant passages  340  in  FIG. 3 , first portion  446  extends slightly radially outward as first portion  446  extends in an axially forward direction (i.e., into the page). Other embodiments of seal seat  414  can include a first portion of each passage of the plurality of cooling lubricant passages  440  that does not extend slightly radially outward (extends only in an axial direction as shown in  FIG. 2 ) or extends radially outward at a greater angle than that shown in the disclosed embodiments. 
     Second portion  448  extends at angle θ 2  that is between zero degrees and ninety degrees in the circumferential direction when measured from line L that extends in the radial direction from centerline L, with angle θ 2  as shown in  FIG. 4  at approximately forty-five degrees. Second portion  446  extends at angle θ 2  that is away from direction of rotation R of seal seat  414 . With second portion  446  extending at angle θ 2  away from direction of rotation R, the cooling lubricant flowing within each passage of the plurality of cooling lubricant passages  440  will have a shorter dwell time (i.e., the cooling lubricant will remain within each passage for a shorter amount of time) than other configurations of second portion  446  because the forces caused by the rotation of seal seat  414  will pull the flowing cooling lubricant towards outer end  438 . Having a dwell time that is shorter may be desired in some applications, such as when the difference in temperature between the cooling lubricant and seal seat  414  is small and more cooling lubricant is required to flow through the plurality of cooling lubricant passages  440  to cool seal seat  414 . 
     As with seal seat  314  in  FIG. 3 , second portion  448  of each passage can have the same angle θ 2  as adjacent passages or can have a different angle θ 2 . Additionally, first portion  446  and/or second portion  448  do not need to extend in a straight line, but rather can have one or multiple curves, zig-zags, or other configurations depending on the cooling needs of seal seat  314 . Further, first portion  446  can be configured to extend at least partially in the circumferential direction, and second portion  448  can be configured to extend at least partially in the axial direction. Each passage of the plurality of cooling lubricant passages  440  can be approximately equidistant from adjacent passages in a circumferential direction, or the passages can vary in circumferential distance from one another. 
       FIG. 5  is a cross-sectional elevation view of another embodiment of a hydrodynamic seal. Similar to hydrodynamic seal  110  in  FIGS. 1A and 1B , hydrodynamic seal  510  includes seal assembly  512  and seal seat  514 . Seal assembly  512  includes housing  518  (with cylindrical portion  519 A and arm  519 B), resilient member  520 , carrier  122  (with inner cylindrical portion  523 A, outer cylindrical portion  523 B, and disk-like arm  523 C), and seal block  524 . Seal seat  514 , which is rotatable about centerline C, includes base  526  at inner end  528 , neck  530  with first notch  532  and second notch  534 , head  536  at outer end  538 , a plurality of cooling lubricant passages  540 , and base passages  552 . Head  536  has coating  542  on sealing surface  544  with sealing surface  544  being on a first axial side of seal seat  514  adjacent to seal block  524 . The plurality of cooling lubricant passages  540  have first portion  546  and second portion  548 . During operation, fluid bearing surface  550  is present between seal block  524  and sealing surface  544  of head  536 . 
     Hydrodynamic seal  510  of  FIG. 5  is similar in configuration and functionality to hydrodynamic seal  110  of  FIGS. 1A and 1B , except that hydrodynamic seal  510  is inverse in an axial direction to hydrodynamic seal  110  (i.e., seal seat  514  is axially forward from seal assembly  512 ) and seal seat  514  includes base passages  552  instead of a nozzle to convey cooling lubricant from an area radially inward from inner end  528  of base  526  to first notch  532  and to the plurality of cooling lubricant passages  540 . 
     Hydrodynamic seal  510  is configured such that seal seat  514  is axially forward from seal assembly  512 . However, hydrodynamic seal  510  functions similarly as hydrodynamic seal  110  of  FIGS. 1A and 1B  by providing a seal (i.e., fluid bearing surface  550 ) between sealing surface  544  on head  536  of seal seat  514  and seal block  524  of seal assembly  512 . 
     Seal seat  514  includes base  526  at inner end  528 , head  536  at outer end  538 , and neck  530  between base  526  and head  536 . The configuration and functionality of seal seat  514  is similar to seal seat  114  of hydrodynamic seal  110  of  FIGS. 1A and 1B , but base  526  includes base passages  552 . In some configurations, the area radially inward from inner end  528  of base  526  can contain cooling lubricant, and base passages  552  convey cooling lubricant from the area radially inward of base  526  to first notch  532  and the plurality of cooling passages  540 . Additionally, base passage  552  can provide cooling to base  526  by allowing heat transfer between base  526  and the cooling lubricant flowing through base passages  552 . 
     Base passages  552  extend from inner end  528  to first notch  532 , and can extend entirely in the radial direction or can angle axially forward or rearward and/or circumferentially towards or away from a direction of rotation of seal seat  514 . Base passages  552  can have the same number as that of the plurality of cooling lubricant passages  540 , or base passages  552  can have more or less passages than that of the plurality of cooling lubricant passages  540 . Similarly, the cross-sectional flow area shape and diameter of base passages  552  can be the same or different than that of the plurality of cooling lubricant passages  540 . Depending on design considerations and the amount of cooling lubricant needed, the number of passages, a length of each passage, and the cross-sectional flow area shape and diameter of base passages  552  can be sized to convey more or less cooling lubricant to first notch  532  and the plurality of cooling lubricant passages  540 . The configuration of each passage of base passages  552  can vary between each passage and adjacent passages, such as a passage having a different diameter or shape than adjacent passages. A circumferential distance between adjacent passages of base passages  540  can be equal (i.e., passages are equidistant from adjacent passages in a circumferential direction) such that base passages  540  are equally spaced around the entire circumference of base  526  seal seat  114 , or the circumferential distance between adjacent passages of base passages  540  can be varied (i.e., adjacent passages are a different circumferential distance away) depending on design considerations. Further, base passages  552  can have curves, zig-zags, or another configuration. Base passages  552  can be formed through a variety of methods, including machining, additive manufacturing, electrical discharge machining, and/or electrochemical machining. 
     Hydrodynamic seal  110 / 210 / 510  is disclosed herein that includes seal seat  114 / 214 / 314 / 414 / 514  with a plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540 . Hydrodynamic seal  110 / 210 / 510  can provide a seal to enclose a compartment, such as a bearing compartment, to prevent fluids within the compartment from escaping. Hydrodynamic seal  110 / 210 / 510  includes a stationary seal assembly  112 / 212 / 512  that has housing  118 / 218 / 518 , resilient member  120 / 220 / 520 , carrier  122 / 222 / 522 , and seal block  124 / 224 / 524 . Hydrodynamic seal  110 / 210 / 510  also includes a rotatable seal seat  114 / 214 / 314 / 414 / 514  configured to attach to a shaft, such as a main shaft in a gas turbine engine. Seal seat  114 / 214 / 314 / 414 / 514  has base  126 / 226 / 326 / 426 / 526 , head  136 / 236 / 336 / 436 / 536 , and neck  130 / 230 / 330 / 430 / 530  between base  126 / 226 / 326 / 426 / 526  and head  136 / 236 / 336 / 436 / 536 . Neck  130 / 230 / 330 / 430 / 530  includes first notch  132 / 232 / 332 / 432 / 532  on the second axial side of seal seat  114 / 214 / 314 / 414 / 514  into which nozzle  116 / 216  dispenses cooling lubricant. Neck  130 / 230 / 330 / 430 / 530  can also include second notch  134 / 234 / 534  on the second axial side that helps balance seal seat  114 / 214 / 314 / 414 / 514 . During operation, a fluid bearing surface  150 / 250 / 550 , such as an air film, is formed between seal block  124 / 224 / 524  and sealing surface  144 / 244 / 544  on head  136 / 236 / 336 / 436 / 536 , forming a seal that prevents the cooling lubricant or other fluids from flowing through while also limiting the amount of friction between the stationary seal assembly  112 / 212 / 512  and the rotating seal seat  114 / 214 / 314 / 414 / 514 . Occasionally, seal seat  114 / 214 / 314 / 414 / 514  can contact seal block  124 / 224 / 524 , causing heat and an increase in temperature in seal seat  114 / 214 / 314 / 414 / 514  due to friction between the rotating seal seat  114 / 214 / 314 / 414 / 514  and the stationary seal block  124 / 224 / 524 . To mitigate that heat, seal seat  114 / 214 / 314 / 414 / 514  includes the plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  that extend from first notch  132 / 232 / 332 / 432 / 532  in neck  130 / 230 / 330 / 430 / 530  to outer end  138 / 238 / 338 / 438 / 538  of head  136 / 236 / 336 / 436 / 536 . The plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  allows cooling lubricant, such as oil, to flow from first notch  132 / 232 / 332 / 432 / 532  (which is supplied with cooling lubricant by nozzle  116 / 216 ), through seal seat  114 / 214 / 314 / 414 / 514 , and out of head  136 / 236 / 336 / 436 / 536 . Further, seal seat  114 / 214 / 314 / 414 / 514  can include cooling lubricant dam  252 / 452  extending radially inward from head  136 / 236 / 336 / 436 / 536  into first notch  132 / 232 / 332 / 432 / 532  in neck  130 / 230 / 330 / 430 / 530 . Cooling lubricant dam  252 / 452  helps prevent cooling lubricant, which can pool on the radially outer surface of first notch  132 / 232 / 332 / 432 / 532  (i.e., a surface adjacent head  136 / 236 / 336 / 436 / 536 ) due to the rotation of seal seat  114 / 214 / 314 / 414 / 514 , from flowing out of first notch  132 / 232 / 332 / 432 / 532  other than through the plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540 . Cooling lubricant dam  252 / 452  increases the efficiency of hydrodynamic seal  110 / 210 / 510  by limiting the amount of cooling lubricant that is dispensed into first notch  132 / 232 / 332 / 432 / 532 . 
     Seal seat  114 / 214 / 314 / 414 / 514  with the plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  and cooling lubricant dam  252 / 452  has many advantages. The plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  allows cooling lubricant to flow through seal seat  114 / 214 / 314 / 414 / 514 , reducing the temperature and likelihood of damage to seal seat  114 / 214 / 314 / 414 / 514 . The number, orientation, and exit point of each passages of the plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  can be varied depending on the cooling needs of seal seat  114 / 214 / 314 / 414 / 514 , the material used to construct seal seat  114 / 214 / 314 / 414 / 514 , the manufacturing process utilized in constructing seal seat  114 / 214 / 314 / 414 / 514 , and other considerations. If greater cooling is needed, each passage of the plurality of cooling lubricant passages  140 / 240 / 340 / 440 / 540  can have a longer flow length and/or the number of passages can be increased. As mentioned above, cooling lubricant dam  252 / 452  increases the efficiency of hydrodynamic seal  110 / 210 / 510  by limiting the amount of cooling lubricant that is dispensed into first notch  132 / 232 / 332 / 432 / 532  to cool seal seat  114 / 214 / 314 / 414 / 514 . 
     Discussion of Possible Embodiments 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A seal seat includes a base having an annular shape, a neck having an annular shape and being radially outward from the base with the neck having an axial length that is less than an axial length of the base, and a head having an annular shape and being radially outward from the neck with the head having and outer end, a sealing surface, and an axial length that is greater than the axial length of the neck. The seal seat also includes a notch adjacent to the neck formed by the base, neck, and head and a plurality of cooling lubricant passages with each passage of the plurality of cooling lubricant passages extending from the notch to a point on the outer end of the head. The plurality of cooling lubricant passages configured to allow cooling lubricant to flow from the notch to the outer end of the head. 
     The seal seat of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     Each passage of the plurality of cooling lubricant passages further includes a first portion that extends from the notch to a transition point within the head, and a second portion that extends from the transition point within the head to the point on the outer end of the head. 
     The first portion extends at an angle that is between zero degrees and thirty degrees in an axial direction when measured from a line that is parallel to an inner end of the base. 
     The second portion extends at an angle that is between zero degrees and ninety degrees in the circumferential direction when measured from a line that extends in a radial direction. 
     The seal seat is rotatable about a centerline and the second portion of each passage of the plurality of cooling lubricant passages extends at an angle that is towards a direction of rotation of the seal seat. 
     The seal seat is rotatable about a centerline and the second portion of each passage of the plurality of cooling lubricant passages extends at an angle that is away from a direction of rotation of the seal seat. 
     The plurality of cooling lubricant passages includes at least two passages. 
     Each passage of the plurality of cooling lubricant passages is approximately equidistant from adjacent cooling lubricant passages in a circumferential direction. 
     A cooling lubricant dam that extends radially inward from the head into the notch, the cooling lubricant dam configured to prevent cooling lubricant within the notch from flowing out of in the notch. 
     Base passages extending through the base from an inner end of the base to the notch, the base passages configured to allow cooling lubricant to flow through the base to the notch. 
     A seal includes a nonrotatable seal assembly and a rotatable seal seat with the seal seat being annular and having a radially inner end, a radially outer end, a sealing surface on an axially first side adjacent to the seal assembly, a notch in an axially second side, and cooling lubricant channels extending from the notch to the radially outer end. 
     The seal of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     A nozzle configured to convey cooling lubricant to the notch and the cooling lubricant channels. 
     Base passages extending from the radially inner end of the rotatable seal seat to the notch, the base passages configured to convey cooling lubricant to the notch and the cooling lubricant channels. 
     Each of the cooling lubricant channels extends from the notch to a point on the radially outer end that is adjacent to the sealing surface. 
     Each of the cooling lubricant channels has a first portion extending from the notch substantially towards the axial first side and a second portion extending from the first portion to the radially outer end. 
     The second portion of each of the cooling lubricant channels extends at an angle that is between zero degrees and ninety degrees in a circumferential direction when measured from a line that extends in a radial direction. 
     A hydrodynamic seal in a gas turbine engine includes a seal assembly that is nonrotatable and has a seal housing, a carrier, a resilient member between the seal housing and the carrier, and a seal block attached to the carrier and a seal seat that is annular, rotatable, and configured to attach to a rotatable shaft, the seal seat having a first side and a second side. The seal seat includes a base, a neck connected to and radially outward from the base, a head connected to and radially outward from the neck with the head having a sealing surface on the first side that is adjacent to the seal block of the seal assembly, a first notch in the neck on the second side of the seal seat, and lubricant passages extending from the first notch to an outer end of the head with each of the lubricant passages extending to a point on the outer end of the head near the sealing surface. 
     The hydrodynamic seal of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     A lubricant dam that is annular in shape and extends radially inward from the head into the first notch. 
     A second notch in the neck on the first side of the seal seat. 
     Each of the lubricant passages extends in at least two directions between the first notch and the outer end of the head. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.