Abstract:
A brush seal assembly for sealing a gap between a first component and a second component, comprising: a body; bristles extending from the body; and an extension from the body, the extension having an elongated slot therein. The slot, when the brush seal assembly mounts between the first and second components, allows the brush seal assembly to float within the gap. An axial brush seal assembly, comprising: a body; bristles extending from the body; and means for allowing movement of the brush seal assembly in an axial direction within the gap. An apparatus, comprising: a first component; a second component spaced from the first component in an axial direction; and an axial brush seal assembly movably mounted between the first and second components. The brush seal assembly can move in said axial direction.

Description:
BACKGROUND OF INVENTION 
   This invention relates to floating brush seal assemblies. Specifically, this invention relates to axial brush seal assemblies that can float in the axial direction within a gap between two components. 
   Gas turbine engines that exhibit high axial and radial growth transients between adjacent components during operation typically use a labyrinth seal between the components to control leakage. A labyrinth seal comprises a plurality of teeth extending from a disk on one of the components and a honeycomb pad on the other component. The teeth and the pad cooperate to form a serpentine leakage path between the components. The serpentine path inhibits fluid flow between the components. 
   However, labyrinth seals have several drawbacks. First, the rigid teeth of the labyrinth seal cannot accommodate a “zero clearance” condition without incurring permanent wear or damage to the teeth. This wear increases the leakage rate of the seal. Second, the leakage rate of the labyrinth seals increases with the increased clearance between the teeth and the pad. 
   SUMMARY OF INVENTION 
   It is an object of the present invention to provide an improved seal. 
   It is a further object of the present invention to use a brush seal to control leakage between adjacent components that exhibit high axial and radial growth transients during operation. 
   It is a further object of the present invention to provide a seal that can accommodate tight “zero clearance” conditions without permanent wear or damage. 
   It is a further object of the present invention to provide a compliant seal that can accommodate a wide range of clearances. 
   It is a further object of the present invention to provide a seal that maintains a relatively constant leakage flow rate even as the clearance between the components increases. 
   These and other objects of the present invention are achieved in one aspect by a brush seal assembly for sealing a gap between a first component and a second component. The assembly comprises: a body; bristles extending from the body; and an extension from the body, the extension having an elongated slot therein. The slot, when the brush seal assembly mounts between the first and second components, allows the brush seal assembly to float within the gap. 
   These and other objects of the present invention are achieved in another aspect by an axial brush seal assembly for sealing a gap between a first component and a second component. The brush seal assembly comprises: a body; bristles extending from said body; and means for allowing movement of the brush seal assembly in an axial direction within the gap. 
   These and other objects of the present invention are achieved in another aspect by an apparatus, comprising: a first component; a second component spaced from the first component in an axial direction; and an axial brush seal assembly movably mounted between the first and second components. The brush seal assembly can move in the axial direction. 
   These and other objects of the present invention are achieved in another aspect by a method of sealing a gap between a first component and a second component. The method comprises the steps of: placing an axial brush seal assembly between the first and second components; and allowing the brush seal assembly to float in the gap. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which: 
       FIG. 1  is a perspective view, in cross-section, of one embodiment of a brush seal assembly of the present invention; 
       FIG. 2  is a perspective view, in cross-section, of another embodiment of a brush seal assembly of the present invention; 
       FIG. 3  is a cross-sectional view of another embodiment of a brush seal assembly of the present invention; and 
       FIG. 4  is a perspective view, in cross-section, of another embodiment of a brush seal assembly of the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  displays one alternative embodiment of the present invention. The figure provides a brush seal assembly  10  that inhibits fluid flow through a gap  11  between a first component  13  and a second component  15  of an apparatus such as a gas turbine engine. The components  13 ,  15  could be stationary or rotating components. The figure shows the first component  13  as a rotating component (such as a turbine disc). The component  13  could include a ring  17  that acts as a land surface for the brush seal assembly  10 . 
   The figures also show the second component  15  as a stationary component (such as a turbine nozzle). Since the component  15  remains stationary, no need exists for a ring to provide a land surface like the rotating first component  13  may require. As seen in the figures, multiple elements could form the stationary component  15 . Alternatively, both components could be stationary components such as adjacent sections of the engine case, compressor stators and the engine case, or turbine nozzles and the engine case. 
   During operation of the gas turbine engine, the components  13 ,  15  exhibit high axial growth transients. In other words, the components  13 ,  15  move substantially in the axial direction during operation. Although a secondary consideration, the present invention can also accommodate radial growth transients. 
   The brush seal assembly  10  serves to inhibit flow through the gap  11  between the components  13 ,  15  despite the growth transients. Generally speaking, the present invention allows movement of the brush seal assembly  10  to ensure an adequate seal despite substantial growth transients. For example, a substantial growth transient could reduce or increase the gap  11  by up to approximately 15% in the axial direction. 
   The brush seal assembly  10  is preferably an axial brush seal assembly. The brush seal assembly  10  could use a separate brush seal for each component  13 ,  15  as seen in  FIGS. 1 and 2 . Alternatively, the brush seal assembly  10  could be a single brush seal that engages both components  13 ,  15  such as that shown in FIG.  3 . The brush seal preferably has a conventional arrangement, with a bristle pack  19  secured to a backing plate  21  and a side plate  23  such as by welding the metallic pieces together. 
   An extension  25  bridges between the backing plates  21 . The annular extension  25  has a suitable number of circumferentially located slots  27  therein. The slots  27  are elongated in the axial direction of the engine. Preferably, the slots are not elongated in the circumferential direction to prevent rotation of the brush seal. The slots  27  could receive bushings  29  made from, for example, a suitable low friction material. 
   The second component  15  includes threaded blind holes that correspond to the slots  27  in the extension  25 . To secure the brush seal assembly  10  to the second component  15 , suitable fasteners, such as set screws  31 , extend through the slots  27  in the extension  25  and into the blind holes of the second component  15 . The head of the screw  31  is preferably larger than the slot  27 . 
   A spring  33  could surround the shaft of each of the screws  31 . The springs  33  help center the brush seal assembly  10  within the engine. 
   During axial growth transients, the second component  15  can move relative to the first component  13  without affecting the performance of the brush seal assembly  10 . The elongation of the slots  27  in the extension  25  allows movement of the screws  31  from the second component  15  therein. 
   Although a secondary consideration, the second component  15  should also be able to move relative to the first component  13  during radial growth transients without affecting the performance of the brush seal assembly  10 . The gap between the extension  25  and the second component  15  allows for such movement. The slots  27  allow the screws  31  to move therein. In essence, the present invention allows the brush seal assembly  10  to float between the components  13 ,  15 . 
   The present invention self centers within the gap  11 . As transients increase, the bristles of the brush seal assembly  10  comply and increase their lay angle. Similarly, as transients decrease, the bristles of the brush seal assembly  10  relax and decrease their lay angle. Throughout this range of bristle movement, the brush seal assembly  10  maintains a relatively constant leakage flow rate through the gap  11  between the components  13 ,  15 . 
   Since the screw  31  does not occlude the entire slot  27  (the slot  27  being elongated), this arrangement may produce an undesired leakage flow rate. To reduce leakage through the slots  27 , the brush seal assembly  10  could include an annular ring  35  that bridges between the side plates  23 . The ring  35  could secure to the side plates  23  using any suitable technique such as press-fitting or welding (obviously after the screws  31  have been properly secured in the blind holes). The ring  35  prevents fluid flow through the slots  27 . Other alternative techniques, however, could be used. For example, a large washer (not shown) could be placed between the inner diameter of the extension  25  and the head of the screw  31 . The washer is sized to occlude the enlarged slots  27  at any position of the screw  31  within the slot  27 . 
     FIG. 2  displays another alternative embodiment of the present invention. The figure displays a brush seal assembly  100  that inhibits fluid flow through a gap between a first component  101  and a second component  103  of an apparatus such as a gas turbine engine. Similar to the aforementioned embodiment, the first component  101  is preferably a rotating component and the second component  103  is preferably a stationary component. 
   The brush seal assembly  100  includes a bristle pack  105  sandwiched between backing plates  107  and side plates  109 . Similar to the aforementioned brush seal assembly  10 , the brush seal assembly  100  includes an extension  111  that bridges between the backing plates  107 . 
   Differently than the aforementioned brush seal assembly, the annular extension  111  has a suitable number of threaded holes therein. The holes receive a suitable fastener such as a plunger assembly  113 . The plunger assembly  113  includes a set screw  115  with a plunger  117  extending from the distal end. A spring (not shown) within the screw  115  biases the plunger away from the head of the screw  115 . The spring within the screw  115  also helps center the brush seal assembly  100  within the engine. 
   To secure the brush seal assembly  100  to the second component  103 , the operator urges the brush seal assembly  100  towards a shoulder  119  of the second component  103 . As the brush seal assembly  100  approaches the second component  103 , the plunger  117  will eventually abut a chamfer  121  on the second component  103 . Continued urging of the brush seal assembly  100  towards the shoulder causes the chamfer  121  to depress the plunger  117 . Eventually, the brush seal assembly  100  arrives adjacent the shoulder  119 . The plunger  117  will encounter one of a plurality of elongated slots  123  in the second component  103 . The spring biases the plunger  117  into the elongated slot  123 . The brush seal assembly  100  is now fully secured to the second component  103 . To remove the brush seal assembly  100 , the plunger assemblies  113  could be unscrewed from the extension  111 . Alternatively, the brush seal assembly  100  may be removed from the second component  103  by disengaging the plunger  117  from the slot  123 . Conventional techniques to disengage the plunger  117  include providing the proximal end (the end opposite plunger  117 ) of the plunger assembly  113  with pull levers, knobs or rings (none shown). The operator can actuate these pull levers, knobs or rings to withdraw the plunger  117  from the slot  123 . 
   During axial growth transients, the second component  103  can move relative to the first component  101  without affecting the performance of the brush seal assembly  100 . The elongation of the slots  123  in the second component  103  allows movement of the plunger assemblies  113  therein. 
   Note that the plunger assemblies  113  completely occlude the holes in the extension  111 . As a result, no leakage paths exist in the extension  111 . Therefore, the brush seal assembly  100  does not require the annular ring  35  used by the aforementioned brush seal assembly  10 . 
     FIG. 3  displays another alternative embodiment of the present invention. The figure displays a brush seal assembly  200  that inhibits fluid flow through a gap between a first component  201  and a second component  203  of an apparatus such as a gas turbine engine. Differently than with the earlier embodiments, both components  201 ,  203  are preferably stationary components. 
   The brush seal assembly  200  is preferably a single axial brush seal. However, the brush seal assembly  200  could use separate brush seals for each component  201 ,  203  as seen in  FIGS. 1 and 2 . The brush seal assembly  200  includes a bristle pack  205  secured to a backing plate  207  and a side plate  209  (with an integral windage cover) such as by welding the metallic pieces together. 
   The brush seal assembly  200  can reside within an annular slot  211  in the first component  201 . Preferably, the slot  211  is sized to allow the brush seal assembly  200  to move axially (i.e. parallel to centerline L of the engine) within the engine to accommodate axial growth transients. In addition, the slot  211  is sized to generally limit radial movement of the brush seal assembly  200  in the engine. 
   As necessary, the slot  211  could have a plurality of circumferentially spaced keyways  213  in communication therewith. The keyways  213  accept splines  215  radially extending from the backing plate  207 . This arrangement prevents the brush seal assembly  200  from rotating. 
     FIG. 4  displays another alternative embodiment of the present invention. The figure shows a brush seal assembly  300  that inhibits fluid flow through a gap between a first component  301  and a second component  303  of an apparatus such as a gas turbine engine. The first component  301  is preferably a rotating component and the second component  303  is preferably a stationary component. 
   Similar to the aforementioned brush seal assembly  200 , the brush seal assembly  300  is preferably a single axial brush seal. The brush seal assembly  300  could, however, use separate brush seals for each component  301 ,  303 . The brush seal assembly  300  includes a bristle pack  305  secured to a backing plate  307  and a side plate  309  (with an integral windage cover) such as by welding the metallic pieces together. 
   An extension  311  projects from the backing plate  307 . The annular extension  311  has a plurality of elongated slots  313  therein. The slots  313  extend in the axial direction of the engine. Preferably, the slots  313  are not elongated in the circumferential direction to prevent rotation of the brush seal. A boss  315  surrounds each slot  313 . The boss  315 /slot  313  could have a low-friction coating thereon, or a bushing (not shown) made from a low friction material could be placed in the slot  313 . 
   Suitable fasteners, such as set screws  317 , extend through the slots  313  to mount the brush seal assembly  300  to the second component  303 . A coil spring  319  surrounds the fastener  317 . The spring  319  serves to bias the extension  311  away from the head of the fastener  317  and towards the second component  303 . 
   The fastener  317  sufficiently compresses the spring  319  to urge the extension  311  against the second component  303 . However, the spring  319  should also permit movement of the second component  303  relative to the brush seal assembly  300  by allowing the fastener  317  to move with the elongated slot  313 . The spring rates of the bristles of the bristle pack  305  keep the brush seal assembly  300  centered within the gap between the components  301 ,  303 . This centering capability also allows the fasteners  317  will move within the slots  313 . 
   This arrangement allows movement of the second component  303  relative to the first component  301  without affecting the performance of the brush seal assembly  300 . The elongation of the slots  313  in the extension  311  allows movement of the fasteners  317  therein. In other words, the present invention allows the brush seal assembly  300  to float between the components  301 ,  303  in the axial direction. 
   The present invention has been described in connection with the preferred embodiments of the various figures. It is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.