Abstract:
A brush seal adapted to restrict a fluid flow through a gap between a first component and a second component, comprising: a body; a brush pack secured to said body; and a passage through said body for introducing a cooling flow to said gap. The passage has a first end that is exposed to the gap and a second end that is not exposed to the gap. The passage discharges a cooling flow to said brush seal, the cooling flow being discrete from the fluid flow.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to brush seals. Specifically, this invention relates to cooling arrangements for brush seals.  
           [0002]    New gas turbine engine designs typically increase efficiency by operating at higher temperatures. These higher operating temperatures affect, among other components, the brush seals used in these designs. As the operating temperatures increase, these higher operating temperatures may approach, or even surpass, the recommended temperature limits for the materials comprising the brush seal.  
           [0003]    A related concern in brush seal design is the temperature of bristle tips. As the land surface of the runner rotates against the brush seal bristles, the friction therebetween creates heat. Excessive temperatures at the bristle tips caused by this friction can deteriorate the bristle tips and the land surface. Excessive bristle tip temperatures can also cause duck-footing or smearing of the bristles. Finally, excessive bristle tip temperatures can cause the bristles to fuse to the runner. These conditions can rapidly decrease the performance of the brush seal.  
         SUMMARY OF INVENTION  
         [0004]    It is an object of the present invention to provide an improved brush seal.  
           [0005]    It is a further object of the present invention to provide a brush seal that can operate at increased operating temperatures.  
           [0006]    It is a further object of the present invention to provide a brush seal that limits bristle tip temperatures.  
           [0007]    It is a further object of the present invention to provide a brush seal with a cooling arrangement.  
           [0008]    These and other objects of the present invention are achieved in one aspect by a brush seal. The brush seal is adapted to restrict a fluid flow through a gap between a first component and a second component, and comprises: a body; a brush pack secured to said body; and a passage through said body for introducing a cooling flow to said gap. The passage has a first end that is exposed to said gap and a second end that is not exposed to said gap.  
           [0009]    These and other objects of the present invention are achieved in another aspect by an apparatus, comprising: a first component; a second component; a brush seal mounted on said first component and contacting said second component, wherein said brush seal inhibits a fluid flow from passing between said first component and said second component; and an opening for discharging a cooling flow to said brush seal, said cooling flow discrete from said fluid flow.  
           [0010]    These and other objects of the present invention are achieved in another aspect by a method of cooling a brush seal. The method comprises the steps of: providing a brush seal, first component and second component; placing said brush seal between said first component and said second component to inhibit a fluid flow from passing therebetween; and supplying a cooling flow to said brush seal. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    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:  
         [0012]    [0012]FIG. 1 is a cross-sectional view of a gas turbofan engine;  
         [0013]    [0013]FIG. 2 is a partial cross-sectional view of one alternative embodiment of a brush seal cooling arrangement of the present invention;  
         [0014]    [0014]FIG. 3 is a perspective view, in partial cross-sectional, of another alternative embodiment of a brush seal cooling arrangement of the present invention; and  
         [0015]    [0015]FIG. 4 is a cross-sectional view of another alternative embodiment of a brush seal cooling arrangement of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]    [0016]FIG. 1 displays a conventional gas turbofan engine  10 . Starting at the upstream end, or inlet  11 , the major components of the engine  10  include a fan section  13 , a low pressure axial compressor  15 , a high pressure axial compressor  17 , a burner section  19 , a high pressure turbine  21 , a low pressure turbine  23 , and a nozzle  25 . Generally speaking, the engine  10  operates as follows. Air enters the engine  10  through the inlet  11 , travels past the fan section  13  (which can be considered part of the compressor), becomes compressed by the compressors  15 ,  17 , mixes with fuel, and combusts in the burner section  19 . The gases from the burner section  19  drive the turbines  21 ,  23 , then exit the engine  10  through the nozzle  25 .  
         [0017]    As designed, the engine  10  inducts more air than is necessary for complete combustion. This surplus allows for the use of a portion of the air to perform other functions. For example, the surplus air can drive accessories (not shown) such as air conditioning units, hydraulic pumps and thrust reverser actuators. In addition, removing surplus air can help avoid compressor surge. However, the main purpose of extracting air is for cooling the engine  10 .  
         [0018]    Cooling can occur by extracting surplus air from a cooler section of the engine  10  and delivering the extracted air to a hotter section of the engine  10 . For example, the extraction could occur from the fan section  13  or the compressor sections  15 ,  17  to supply cooling air to the turbine sections  21 ,  23 .  
         [0019]    The extraction of surplus air can occur in two ways. First, the extracted air can travel internally through the engine  10 . Second, the extracted air can travel externally from the engine  10 . FIG. 1 shows both possibilities.  
         [0020]    The internal cooling air path in FIG. 1 relies on a hollow shaft  27  connecting the low pressure compressor  15  and low pressure turbine  23 . Air bleeds from the low pressure compressor  15 , enters the shaft  27  through openings therein, exits the shaft  27  and arrives at the blades of the low pressure turbine  23 .  
         [0021]    The external cooling air path of FIG. 1 relies on a duct  29  adjacent the engine  10 . Air bleeds from the high pressure compressor  15 , enters the duct  29 , travels through the duct  29  and arrives at the vanes of the high pressure turbine  21  The present invention utilizes one or both of these cooling paths to cool a brush seal. The cooling arrangement of the present invention allows the engine  10  to operate at elevated temperatures. FIGS. 2 and 3 each display a possible brush seal arrangement.  
         [0022]    [0022]FIG. 2 displays a brush seal  51  mounted to a first component  53  of the engine  10 . The brush seal  51  could mount to first component  53  using conventional techniques, for example with a removable flange (not shown). With the flange removed from the first component  53 , the brush seal  51  could mount to a groove (not shown) in the first component  53 . The flange is then fastened to the first component  53  to sandwich the brush seal  51  therebetween. The first component  53  is typically a stationary component of the engine  10 , such as a diffuser case.  
         [0023]    The brush seal  51  has a body, typically comprising a backing plate  55  and a side plate  57 . The side plate  57  could include a windage cover  59 . Alternatively, the windage cover  59  could comprise a separate piece from the side plate  57 .  
         [0024]    A brush pack  61  resides between the backing plate  55  and the side plate  57 . A plurality of fine wire bristles comprise the brush pack  61 . The brush pack  61  and the plates  55 ,  57  secure together using known techniques, such as by welding. Although the figures show the bristles extending radially within the engine  10 , brush seals are also used to close gaps between upstream and downstream components. In this arrangement, the bristles preferably extend axially (not shown) within the engine.  
         [0025]    The brush pack  61  engages a second component  63  of the engine  10 . Depending upon the application (e.g. dynamic or static), the second component  63  could be a rotating component of the engine  10  (a dynamic application) or another stationary component of the engine  10  (a static application). Typically, the second component  63  is a rotating component, such as a turbine shaft.  
         [0026]    Regardless of the brush seal  51  having a static or dynamic application, the purpose of the brush seal  51  is to restrict a fluid flow (e.g. air) through a gap  65  between the first component  53  and the second component  63 .  
         [0027]    The friction created by the metallic brush pack  61  engaging the metallic rotating component  63  of the engine  10  produces localized heating in dynamic applications. Excessive heat build-up in this area can deteriorate the bristle tips and the runner land surface. In addition, a high ambient temperature within the gap  65  between the first and second components  53 ,  63  can also deteriorate the brush pack  61  in both static and dynamic applications. The present invention can help control heat build-up at the bristle tips and help lessen the effects of high ambient temperature in the gap  65 .  
         [0028]    The body of the brush seal  51  can have a passageway  67  extending therethrough. The passageway can extend through any suitable part of the body of the brush seal  51 . For the single stage brush seal shown in FIG. 2, the passageway  67  preferably extends through the side plate  57 . The passageway  67  has an inlet at the front face of the side plate  57  and an outlet at the rear face of the side plate  57  adjacent the brush pack  61 . If the side plate  57  includes a windage cover  59  (such as seen in FIG. 1), the passageway  67  could extend through the windage cover  59 . The passageway  67  allows cooling air C to enter the gap  65  and to impinge upon the brush pack  61 . The cooling air C helps reduce the heat build-up at the interface between the brush seal  51  and the second component  63  or reduce the high ambient temperature within the gap  65 .  
         [0029]    Preferably, the cooling air C originates from another location within the engine. In other words, the cooling air C is discrete from the fluid flow within the gap  65  between the first and second components  53 ,  63  of the engine  10 . The cooling air C preferably should also exhibit a lower temperature than the fluid within the gap  65  to help reduce the aforementioned heat build-up.  
         [0030]    The first component  53  helps the cooling air C arrive at the brush seal  51 . The first component  53  has a passageway  69  therethrough. The passageway  69  is located so as to communicate with the passageway  67  of the brush seal  51 . The cooling air, bled from another section of the engine  10  (such as the compressor  13 ,  15 ,  17 ), travels through the passageways  67 ,  69  and enters the gap  65 . Using the arrangement shown in FIG. 1, the external duct  29  of the engine  10  could supply the cooling air C to the passageway  69 . The external duct  29  bleeds air from the high pressure compressor  15 . Other methods and sources of cooling air, however, could be used to supply the passageways  67 ,  69 . Since the first component  53  surrounds the inlet of the passageway  67  and the passageway  69  communicates with the passageway  67 , the inlet of the passageway  67  is not exposed to the gap  65  between the first and second components  53 ,  63  of the engine  10 .  
         [0031]    The passageways  67 ,  69  could have any suitable size that provides a sufficient amount of cooling air C to the brush seal  51 . The passageways  67 ,  69  could also have shapes different than those shown in FIG. 2 in order to allow the cooling air C to impinge upon a desired location of the brush seal  51 .  
         [0032]    [0032]FIG. 3 displays a cooling arrangement for a multiple stage brush seal  151 . The brush seal  151  operates in the same manner as the aforementioned brush seal  51 . In other words, the brush seal  151  inhibits fluid flow through a gap  165  between a first component  153  and a second component  163 .  
         [0033]    Each stage of the brush seal  151  includes a backing plate  155 , side plate  157  and brush pack  161 . The backing plate  155  of each upstream stage serves as the windage cover for the next downstream stage of the brush seal  151 .  
         [0034]    Each stage of the brush seal  151  also includes a passageway  167  to introduce cooling air C to the brush packs  161 . Although shown as extending radially through the side plates  157 , the passageways  167  could travel through any area of the brush seal body and could follow any desired path through the brush seal body.  
         [0035]    The passageways  167  communicate with passageways  169  in the first component  153 . A common header  171  in the first component  153  could supply the cooling air C to the passageways  169 . A supply passageway  173  allows the cooling air C to enter the first component  153 . Any other cooling air supply arrangement, however, could be used (such as individual supplies for each passageway  167 ).  
         [0036]    [0036]FIG. 4 provides another embodiment of a brush seal arrangement. Similar to the aforementioned brush seals, brush seal  251  mounts to a first component  253  of the engine. The brush seal  251  extends from the first component  253  to engage a second component  263  of the engine  10 . The brush seal  251  serves to restrict a fluid flow (e.g. air) through a gap  265  between the first component  253  and the second component  263 .  
         [0037]    Differently than the earlier embodiments, the second component  263  supplies the cooling air C to the brush seal  251 . If, as seen in FIG. 4, the second component  263  is a turbine shaft, the shaft comprises a hollow interior  275  with passageways  277  extending through an outer wall  279  in a circumferential arrangement around the shaft.  
         [0038]    The passageways  277  are located adjacent the interface between the brush seal  251  and the second component  263 . Preferably, the passageways  277  are located upstream of such interface as seen in FIG. 4. Other arrangements, however, are possible (e.g. between stages of a multiple stage brush seal).  
         [0039]    The passageways  277  could have any suitable size to provide a sufficient amount of the cooling air C to the interface between the brush seal  251  and the second component  263 . Although shown as linear and a constant diameter, the passageways  277  could have any suitable shape or taper that allows the cooling air C to impinge upon a desired location of the brush seal  251 .  
         [0040]    Using the arrangement shown in FIG. 1, the cooling air C could bleed from another section of the engine  10  such as the compressor  13 ,  15 ,  17 . The cooling air C would depart the compressor  13 ,  15 ,  17 , travel through the turbine shaft, exit the passageways  277 , and enter the gap  265  between the first and second components  253 ,  263  of the engine  10 . Other methods and sources of cooling air, however, could be used to supply the passageways  277 .  
         [0041]    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.