Abstract:
An example seal assembly includes a first seal that is configured to be placed between a fuel cell manifold and a fuel cell stack. The first seal establishes a recessed area within a side of the first seal that faces the fuel cell stack. The fuel cell seal assembly further includes a second seal that is configured to be placed between the first seal and the fuel cell stack within the recessed area. An example method of sealing a fuel cell interface includes holding a first seal within a groove established within a manifold and holding a second seal within a recessed area established within the second seal. The method limits flow of a fuel cell fluid using a first seal and the second seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase of PCT/US2010/054621, filed Oct. 29, 2010. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to fuel cells. More particularly, this disclosure relates to a sealing arrangement for a fuel cell assembly. 
       DESCRIPTION OF RELATED ART 
       [0003]    Fuel cell stack assemblies (CSAs) are well known and typically include multiple individual fuel cells. The fuel cells include a polymer electrolyte membrane (PEM) positioned between porous carbon electrodes containing a platinum catalyst, which together establish a unitized electrode assembly. One of the electrodes operates as an anode while the other operates as a cathode. The individual fuel cells further include bipolar plates arranged adjacent each of the porous carbon electrodes. The fuel cells utilize fuel and oxidant, such as hydrogen and air, to generate electrical energy in a known manner. The fuel cells may also generate liquid and thermal byproducts. Manifolds are typically utilized to communicate fuel and oxidant to the fuel cells within the CSA. Other manifolds may be utilized to communicate byproducts away from the fuel cell. 
         [0004]    Seal arrangements are used to block flow through a manifold&#39;s interfaces with the CSA. As the interfaces may include irregular surfaces, silicone-based seals are typically used. The pliability of the silicone seals facilitates accommodating the irregular surfaces. 
       SUMMARY 
       [0005]    An example seal assembly includes a first seal that is configured to be placed between a fuel cell manifold and a fuel cell stack. The first seal establishes a recessed area within a side of the first seal that faces the fuel cell stack. The fuel cell seal assembly further includes a second seal that is configured to be placed between the first seal and the fuel cell stack within the recessed area. 
         [0006]    An example fuel cell stack assembly sealing arrangement includes a fuel cell stack having a plurality of outwardly facing surfaces. A manifold and one of the outwardly facing surfaces establish a portion of a fluid communication path. A nonsilicone seal arrangement is held between the outwardly facing surface and the manifold. The nonsilicone seal is configured to seal an interface between the outwardly facing surface and the manifold. 
         [0007]    An example method of sealing a fuel cell interface includes holding a first seal within a groove established within a manifold and holding a second seal within a recessed area established within the second seal. The method limits flow of a fuel cell fluid using a first seal and the second seal. 
         [0008]    These and other features of the disclosed examples can be best understood from the following specification and drawings. The following is a brief description of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a schematic view an example fuel cell assembly. 
           [0010]      FIG. 2  shows an end view of the  FIG. 1  fuel cell assembly. 
           [0011]      FIG. 3  shows a close up view of a manifold interface in the  FIG. 1  fuel cell assembly. 
           [0012]      FIG. 4  shows an exploded view of the manifold and seal assembly of the  FIG. 1  fuel cell assembly. 
           [0013]      FIG. 5  shows the flow of an example method of sealing an interface within the  FIG. 1  fuel cell assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIGS. 1 and 2 , an example proton exchange membrane fuel cell stack assembly  10  includes pressure plates  12  configured to hold together multiple individual fuel cells  14  arranged in a stack. Each of the fuel cells  14  includes an anode  18  and a cathode  22  on opposing sides of a unitized electrode assembly  26 . A flow field plate  30  is positioned near the anode  18 . Another flow field plate  34  is positioned near the cathode  22 . The unitized electrode assembly  26  includes a proton exchange membrane positioned between electrodes, as is known. 
         [0015]    In this example, a fluid source  36  supplies a fuel cell fluid, such as hydrogen, to a manifold  38 , which distributes the fluid to the fuel cell stack assembly  10  through the flow field plates  30  and  34 . 
         [0016]    The example manifold  38  is secured to an outwardly facing surface  42  of the fuel cell stack assembly  10 . Another manifold  38   a  is secured to an outwardly facing surface  42   a . Other examples include manifolds (not shown) on the outwardly facing surfaces  42   a  and  42   b . The manifolds  38  and  38   a  are held against the outwardly facing surfaces  42  and  42   a  respectively with a steel cable and turnbuckle system. Other examples hold the manifolds  38  and  38   a  with other types of cables, bolts, latches, straps, or tie rods. As is known, the manifolds  38  and  38   a  communicate fuel cell fluids, such as the hydrogen from the fluid source  36  or an oxidant, to the fuel cells  14  or away from the fuel cells  14 . 
         [0017]    Although the example embodiment is described as sealing an interface between the manifold  38  and a proton exchange membrane fuel cell stack assembly  10 , those skilled in the art and having the benefit of this disclosure will understand other types of fuel cells that would benefit from the disclosed embodiment. 
         [0018]    In this example, the manifold  38  extends from one of the pressure plates  12  to another pressure plate  12 . In another example, the manifold  38  extends across a smaller portion of the outwardly facing surface  42 , such as from one of the pressure plates  12  to one of the fuel cells  14 . More than one manifold  38  is arranged on the outwardly facing surface  42  in some examples. 
         [0019]    The positions of the fuel cells  14  and their respective components can vary relative to a longitudinal axis X of the fuel cell stack assembly  10 . As can be appreciated, these variances introduce irregularities in the outwardly facing surface  42  of the fuel cell stack assembly  10 . A seal assembly  46  facilitates accommodating these irregularities. 
         [0020]    Referring now to  FIGS. 3 and 4  with continuing reference to  FIG. 1 , the example seal assembly  46  includes a first seal  50  and a second seal  54  at an interface  56  between the manifold  38  and the fuel cell stack assembly  10 . The manifold  38  establishes a groove  58  that receives an extension  62  of the first seal  50 . The first seal  50  establishes a recessed area  66  that receives the second seal  54 . As can be appreciated, the seal assembly  46  has a picture frame type configuration. 
         [0021]    In this example, the first seal  50  includes a plurality of ridges  70  that extend away from the extension  62 . The plurality of ridges  70  establish the recessed area  66 . The plurality of ridges  70  are configured to contact the pressure plates  12  of the fuel cell stack assembly  10  when the manifold  38  is held against the outwardly facing surface  42 . As can be appreciated, the plurality of ridges  70  and the second seal  54  both contact a peripheral portion of the outwardly facing surface  42 . In another example, the plurality of ridges  70  and the second seal  54  contact other areas of the outwardly facing surface  42 , such as when the manifold  38  covers a smaller portion of the outwardly facing surface  42 . 
         [0022]    The extension  62  of the example first seal  50  has a length l 1  ranging from 5.7 mm and 6.2 mm. A main body portion of the example first seal  50  has a length l 2  of 9.1 mm. Each of the plurality of ridges  70  have a length l 3  of 1.1 mm, and the width w of the example first seal  50  is about 8 mm. 
         [0023]    The example first seal  50  is somewhat pliable, which facilitates an initial interference fit, or friction fit, between the first seal  50  and the manifold  38  before the manifold  38  is secured relative to the outwardly facing surface  42 . The example first seal  50  is thus considered a press-in-place seal. Other examples initially secure the first seal  50  relative to the manifold  38  using other techniques, such as an adhesive. 
         [0024]    In this example, both the first seal  50  and the second seal  54  are nonsilicone seals. Specifically, the example first seal  50  comprises an ethylene propylene diene Monomer (EPDM) rubber, and the example second seal  54  comprises a fluoroelastomer (FKM) material. Dyneon™ manufactures a material suitable for the second seal  54  in one example. 
         [0025]    The example second seal  54  is a sealant tape having a rectangular cross-section before the second seal  54  is heat cured. In another example, the second seal  54  is a dispensable sealant that is dispensed from a tube directly into the recessed area  66 . 
         [0026]    When the second seal  54  is initially secured against the outwardly facing surface  42 , the second seal  54  is pliable and conforms to the irregularities in the outwardly facing surface  42 . That is, the cross-section of the second seal  54  changes from having a consistent rectangular cross-section to having an irregular cross-section that accommodates the irregularities in the outwardly facing surface  42 . Pressure exerted by the manifold  38  helps conform the second seal  54  to irregularities in the outwardly facing surface  42 . Curing the second seal  54  then stabilizes the shape of the second seal  54  and enables the second seal  54  to seal a portion of the interface  56 . 
         [0027]    The plurality of ridges  70  limit movement or rolling of the second seal  54  during the curing process. Notably, the plurality of ridges  70  also conform somewhat to the irregularities in the outwardly facing surface  42 , but, due to the material characteristics of the first seal  50 , do not typically provide a consistently sealed interface. 
         [0028]    Referring to  FIG. 5  with continuing reference to  FIGS. 3 and 4 , an example method  100  of installing the seal assembly  46  includes inserting the extension  62  of the first seal  50  within the groove  58  at a step  110 . The step  110  secures the first seal  50  relative to the manifold  38 . 
         [0029]    Next, at a step  120 , the second seal  54  is positioned within the recessed area  66  of the first seal  50 . Adhesive is used to secure the second seal  54  within the recessed area  66 , for example. In another example, material properties of the first seal  50  and the second seal  54  are relied on to secure the second seal  54  within the recessed area  66 . 
         [0030]    The manifold  38  is then secured relative to the outwardly facing surface  42  at a step  130 . In one example, the manifold  38  is pressed against the outwardly facing surface  42  such that the second seal  54  is entombed within the recessed area  66  of the first seal  50 , and both the first seal  50  and the second seal  54  contact the outwardly facing surface  42 . 
         [0031]    At a step  140 , the fuel cell stack assembly  10  is hot soaked. The hot soak cures the second seal  54  to seal the interface  56 . In this example, the second seal  54  cures within four hours when the fuel cell stack assembly  10  is hot soaked at 80° C. 
         [0032]    Features of the disclosed example include a simplified sealing arrangement that conforms to irregularities in a fuel cell stack&#39;s outwardly facing surface. Another feature is reducing a tendency for seal rolling. 
         [0033]    The preceding description is exemplary rather than limiting in nature. A person of ordinary skill in this art may recognize certain variations and modifications to the disclosed examples that do not depart from the essence of this disclosure. For that reason, the following claims should be studied to determine the true scope of legal protection given to this disclosure.