Abstract:
A solid oxide fuel cell module includes a manifold member comprising a plurality of openings. The solid oxide fuel cell module further includes a plurality of fuel cell tube units. The solid oxide fuel cell module further includes a fuel cell tube unit to manifold interconnect member providing a fluid flow channel between the manifold member and the plurality of tubes, wherein the fuel cell tube unit to manifold interconnect member comprises a polymer material.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Application No. 61/206,483, which is hereby incorporated by reference herein in its entirety. 
     
    
     GOVERNMENT INTERESTS 
       [0002]    This invention was made with government support under contract number W909MY-08-C-0025, awarded by the Department of Defense. The government has certain rights in this invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The invention relates to fuel cells and with more particularity to manifolds for fuel cell systems. 
       BACKGROUND OF THE INVENTION 
       [0004]    Manifolds are used to route and distribute air and fuel into various components of a fuel cell system. Current fuel cell systems utilize manifolds that are rigidly coupled to the fuel cell tubes. Therefore, current manifold designs are not adapted for portable applications in that current manifold designs are undesirably large, are not designed for mass manufacturability, and are not robust, shock, vibration, and thermal transitions. 
         [0005]    For example, current manifolds do not allow fuel cell components to flex or comply to allow for variations in the position of fuel cell tubes relative to each other or relative to other fuel cell components. Further, rigid manifold connections do not allow for variations in fuel cell components for example structural variations, shape, straightness, or other toleranced dimensions that can vary during manufacturing. Rigid manifolds can restrict the packaging design and manufacturing options and can undesirably increase the overall size of portable fuel cells. Still further, current manifolds are not adapted for portability and current manifolds are not configured to manage thermal expansion differences between component materials. Therefore, there is a need for a fuel cell manifold that is compliant and that allows variations in the position of fuel cell tubes relative to each other and relative to other fuel cell components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a plan view of one embodiment of a fuel cell system including a manifold member in accordance with an exemplary embodiment of the present disclosure; 
           [0007]      FIG. 2  is a side view and 
           [0008]      FIG. 3  is a sectional view of the manifold member coupled to a plurality of fuel cell tubes of the fuel cell system of  FIG. 1 ; 
           [0009]      FIG. 4  is a perspective view of a fuel cell system including a manifold member in accordance with another embodiment of the present disclosure; 
           [0010]      FIG. 5  is a plan view of the manifold of  FIG. 4  with a lid removed detailing the plurality of outlets; 
           [0011]      FIG. 6  is a plan view of the lid of  FIG. 5 ; 
           [0012]      FIG. 7  is a side view of a interconnecting member including a backpressure control member of the fuel cell system of  FIG. 4 ; 
           [0013]      FIG. 8  is a partial view of an end of a fuel cell system having a plurality of fuel cell tubes; 
           [0014]      FIG. 9  is a partial perspective view of the manifold member connected to the plurality of fuel cell tubes of  FIG. 4 ; 
           [0015]      FIG. 10  is a partial sectional view showing one embodiment of a manifold member coupled to a fuel cell tubes; 
           [0016]      FIG. 11  is a partial sectional view showing one embodiment of a compliant manifold coupled to a fuel cell tube; 
           [0017]      FIG. 12  is a partial sectional view showing one embodiment of a compliant manifold having steps that engage and locate the reactor and fuel cell tube; and 
           [0018]      FIG. 13  is a prospective view of a fuel cell tube. 
       
    
    
     SUMMARY 
       [0019]    A solid oxide fuel cell module includes a manifold member comprising a plurality of openings. The solid oxide fuel cell module further includes a plurality of fuel cell tube units. The solid oxide fuel cell module further includes a fuel cell tube unit to manifold interconnect member providing a fluid flow channel between the manifold member and the plurality of tubes, wherein the fuel cell tube unit to manifold interconnect member comprises a polymer material. 
       DETAILED DESCRIPTION 
       [0020]    Fuel cell systems in accordance with exemplary embodiments are described herein. In one embodiment, a manifold member distributes gas to multiple fuel cell tubes of the fuel cell system. The manifold member is connected to each of the fuel cell tubes such that a substantially gas-tight seal is maintained between an inner chamber of each fuel cell tube and an inner chamber of the manifold member. In one embodiment, a resilient interconnecting member couples the manifold to the fuel cell tubes. The resilient member allows for movement of the plurality of fuel cell tubes connected to the manifold member relative to other fuel cell components. The resilient member can dampen oscillations and reduce mechanical stresses on components of the fuel cell system due to movement of fuel cell components relative to each other. Movement of fuel cell components relative to each other can be caused by external forces on the fuel cell system (for example, vibrational movement), by thermal expansion mismatch between fuel cell system components and by fluid flow within the fuel cell system. Further, the resilient member can adapt to manufacturing variations in, for example, tube size and tube position and the resilient member can facilitate simplified manifold-to-tube assembly. 
         [0021]      FIGS. 1-13  generally depict a fuel cell system  15 . Referring to  FIGS. 3 and 13 , the fuel cell system  15  includes a fuel feed tube  20  and a fuel cell tube  18 . The fuel cell tubes extend in thermally insulated walls  11 . The fuel cell tube  18  and the fuel feed tube  20  together are a fuel cell tube unit  21 . The fuel feed tube  20  is disposed within an inlet portion  17  of the fuel cell tube  18 . Unreformed fuel enters an inlet portion  19  of the fuel feed tube  20 . The unreformed fuel is routed through the fuel feed tube  20  to an internal fuel reformer  52  where the fuel is reformed and the resulting reformed fuel is heated during the exothermic reformation reactions (for an exemplary fuel cell system having an internal fuel reformer, see U.S. Pat. No. 7,547,484 entitled SOLID OXIDE FUEL CELL WITH INTERNAL FUEL PROCESSING which is hereby incorporated by reference in its entirety. The fuel reformation reaction occurs downstream from the inlet portion  19  of the fuel cell tube  18 . 
         [0022]    The fuel cell tubes  18  each comprises an anode layer, an electrolyte layer, and a cathode layer at an active portion  50  that generates electromotive force at the active portion  50  at operating temperatures in the range of 600 to 950 degrees Celsius. However, only the active portion  50  of the fuel cell tube  18  contains the anode layer, the electrolyte layer, and the cathode layer, and therefore, only a portion of the fuel cell tube  18  requires high operating temperatures for generating electromotive force. Therefore, the operating temperatures proximate the inlet portion  19  of the fuel cell tube  20  is less than 250 degrees Celsius, and in an exemplary embodiment, the operating temperature proximate the inlet portion  19  of the fuel cell tube  20  is between about 100 degrees Celsius and 250 degrees Celsius. Thus, low-temperature materials such as the flexible materials described for the interconnect member  30  be utilized to couple the fuel cell tubes  18  to the manifold member  10 . 
         [0023]    The exemplary fuel cell tube  18  is a solid oxide fuel cell that is advantageously relatively lightweight and that can operate providing high power to mass ratio. As an example, the tube can be 1 mm-30 mm in diameter and can be heated rapidly. An example of a suitable fuel cell is disclosed in U.S. Pat. No. 6,749,799 to Crumm et al, entitled METHOD FOR PREPARATION OF SOLID STATE ELECTROCHEMICAL DEVICE which is hereby incorporated by reference in its entirety. Other material combinations for the anode layer, the cathode layer, and the electrolyte layer as well as other cross-section geometries (triangular, square, polygonal, etc.) will be readily apparent to those skilled in the art given the benefit of the disclosure. 
         [0024]    The manifold member  10  can input fuel in one or more inlet openings and substantially evenly distribute fuel among multiple fuel cell tubes  18  of the fuel cell system  15 . The manifold member  10  can distribute fuel substantially evenly utilizing backpressure control members. Referring to  FIG. 7 , in one embodiment, the backpressure control member  26  is disposed at a fuel inlet end of an interconnecting member  30  and has an orifice with a selected cross-sectional area to create a predetermined amount of backpressure to substantially evenly distribute fuel to each of the fuel cell tubes  18 . In one embodiment, backpressure control members are disposed within the plurality of fuel cell tubes. The cross-sectional area can be calibrated to create a selected amount of backpressure to regulate fuel flow from the manifold member  10  into each of the fuel cell tubes  18  of the fuel cell system  15 . The amount of backpressure desired for a specific backpressure control member can vary based on, for example, the travel path of fuel within the fuel cell system, the number of fuel cell tubes, and the width and length of the fuel cell tubes. 
         [0025]    In one embodiment, the backpressure control member can provide functionality in addition to providing a calibrated cross-sectional area for creating a selected amount of backpressure. For example, in one embodiment, a current collector (not shown) disposed within the fuel cell tube  18  can have a calibrated cross-sectional area providing pneumatic resistance to create a selected amount of backpressure. Additionally, in another aspect, the backpressure control members may be integral with the fuel cell tubes  18 , that is, the fuel cell tubes  18  may have a calibrated cross-sectional area to provide a selected amount of pneumatic resistance. 
         [0026]    The back pressure control member can reduce variability due to downstream pneumatic pressure thereby providing substantially uniforms fuel flow through each of the fuel cell tubes. For example, a fuel cell stack can operate at a nominal operating pressure of 2+/−0.5 inches (or a 25% variance range) without a back pressure control member. Back pressure control members tolerance to provide a 5+/−0.05 inches of back pressure can be added to the fuel cell stack with the nominal operating pressure of 2+/−0.5 inches thereby providing a fuel cell with a back pressure of 7+/−0.55 inches (or a 7.9% variance range). 
         [0027]    In one embodiment, the fuel reforming reactor  52  disposed within the fuel cell tube  18  can have a calibrated cross-sectional area to create a selected amount of backpressure. In one embodiment, the backpressure control member can comprise multiple components within the fuel cell tube. For example, a fuel reforming reactor disposed within a fuel feed tube and a current collector can each have calibrated cross sectional areas to create a selected amount of backpressure such that the fuel is substantially evenly distributed among the fuel cell tubes. 
         [0028]    Referring to  FIGS. 1-3 , the manifold member  10  includes a manifold head  12  having an inlet  14  and a plurality of outlets  16 . The manifold member  10  comprises interconnecting members  30  to maintain gas-tights seals between an inner chamber of the manifold member  10  and an inner chamber each of the fuel cell tubes  18 . In one embodiment, the manifold member  10  may be utilized for coupling a plurality of fuel cell tubes  18  of the fuel cell system  15  to a fuel source such that the input of fuel into each of the plurality of fuel cell tubes  18  is substantially balanced. As shown in  FIG. 3 , the plurality of fuel cell tubes  18  are received in and sealed relative to the plurality of outlets  16  of the manifold head  12 . In this manner, fuel introduced into the manifold member  10  passes to the plurality of fuel cell tubes  18  without escaping into an ambient portion of the fuel cell system  15 . In one aspect, and as shown in  FIG. 3 , the plurality of fuel cell tubes  18  may be connected with the plurality of fuel feed tubes  20  that are inserted into and gas-tight coupled with the plurality of fuel cell tubes  18 . By integrating steps into the region of the manifold that is associated with the fuel cell tube, the fuel feed tubes and/or similar structures, the manifold member is further able to provide a support and provide a substantially gas tight fit between the manifold and each of the tubes to avoid leaking. 
         [0029]    In one embodiment, the interconnecting members  30  comprise a flexible silicone-base polymer configured maintain a gas tight seal with the end of the fuel cell tube at temperatures above 100 degrees Celsius and more specifically temperatures of about 200 degrees Celsius to about 250 degrees Celsius. Other exemplary materials for interconnect members are described below: 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Young&#39;s Elasticity Modulus 
               
             
          
           
               
                   
                 Material 
                 Gpa 
               
               
                   
                   
               
               
                   
                 Rubber 
                 0.01-0.1 
               
               
                   
                 LD Polyethylene 
                 0.2 
               
               
                   
                 HD Polyethylene 
                 0.8 
               
               
                   
                 Polystyrene 
                 1.5-2  
               
               
                   
                 Nylon 
                 3   
               
               
                   
                 Graphite 
                 1.5 
               
               
                   
                 Cork 
                  0.03 
               
               
                   
                 Polycarbonate 
                 0.7 
               
               
                   
                 Polyurathane Elastomer 
                  0.25 
               
               
                   
                 Silicone Polymer 
                 0.01-0.1 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    Table 1 includes exemplary interconnecting member  30  material and associated Young&#39;s Elasticity Moduli for each material including rubber, low density (‘LD’) polyethylene, high density (“HD”) polyethylene, nylone, graphite, cork, polycarbonate, polyurethane elastomer, and silicone polymers. Other exemplary materials can further include other elastomers, natural rubber and synthetic rubber (e.g., nytrol), natural latex and synthetic latex (vinyl acetate, styrene-butadiene, and acrylates). The exemplary interconnect members can comprise a modulus of elasticity that is less than or equal to one tenth a modulus of elasticity of a portion of the fuel cell tube unit  21  contacting the manifold member. In one embodiment, the polymer material comprises an elastic modulus of less than 3 GPA, and more specifically less than 0.8 GPA. In one embodiment, the interconnect member comprises material having and elastic modulus of less than 0.1 GPA, for example silicone-based polymers, rubber and like materials. 
         [0031]    The fuel cell manifold member  10  may have various shapes including, for example, a ring shape or a disc shape as shown in the figures. For example, the fuel cell tubes  18  may be positioned in any of a number of configuration including tube rays, tube bundles, and individual tubes. Further, it should be realized that various shapes and positions of the outlets  16  may be utilized. For example, the outlets  16  may be arranged in various patterns and formations to direct fuel to fuel cell tubes  18  configured in various positions. 
         [0032]    Referring to  FIG. 4 , in another aspect, a lid  22  may be removably connected to a top of the manifold head  12  to allow access into an interior of the manifold member  10  to simplify manufacturing through coupling of the manifold member  10  to a fuel cell as well as allow for replacement of various components of the fuel cell system. The manifold member  10  may also include an external circuit board (not shown) that may be attached to a top of the manifold head  12 . 
         [0033]    The manifold member  10  may also include an active cooling mechanism associated with the manifold to regulate a temperature of the manifold. Various active cooling mechanisms including fans and blowers may be utilized to maintain a temperature range of the manifold  10 . 
         [0034]    Referring to  FIGS. 4-9 , there is shown a second embodiment of a manifold member  10 . The second embodiment of the manifold member  10  may include a plurality of interconnecting members  30  coupled in each of the plurality of outlets  16  and connected with the plurality of fuel cell tubes  18 . The plurality of interconnecting members  30  are flexible or “mechanically compliant” The term “mechanically compliant” as used herein, refers to the ability of the manifold member  10  to move relative to the plurality of fuel cell tubes  18  such that shocks and movements associated with the manifold member  10  may be absorbed by the interconnecting members  30 . As with the previously described embodiment, the manifold member  10  may include backpressure control members  28 , shown in  FIG. 7  associated with each of the interconnecting members  30  for balancing the fuel flow into the plurality of fuel cell tubes  18 . The backpressure control members  28  may include a precision orifice or a precision orifice packaged in a cartridge, as well as a flow restrictor that is a capillary tube. 
         [0035]    Referring to  FIGS. 10-11  there are shown various structures of the plurality of interconnecting members  30 . In the depicted embodiment of  FIG. 10 , the interconnecting member  30  is connected to the outlet member  16  and to the fuel feed tube  20 . In the embodiment depicted in  FIG. 12 , the interconnecting member  30  is connected to the outlet member  16  and to the fuel cell tube  18 . A backpressure control member  28 , such as a precision orifice, may also be positioned within the interconnecting member  30 . In the embodiment depicted in  FIG. 12 , the interconnecting member  30  includes stepped portions  31  to locate the fuel cell tube  18  and fuel feed tube  20 . In this manner the fuel feed tube  20  may be positioned longitudinally and radially with respect to the fuel cell tube  18 . It should be realized that the interconnecting member  30  may include various numbers of stepped portions  31 . For example, one of the steps shown in  FIG. 11  may be removed such that either the fuel cell tube  18  or fuel feed tube  20  is positioned longitudinally with respect to the outlet member  16 . Alternatively, the step portions may allow the fuel cell tube or similar structure can to be integrated directly into the manifold member. Although the exemplary tube is shown in which both external and internal diameters are stepped in alternate embodiment, the tube can have an a continuously decreasing internal diameter, a stepped in diameter with a constant outer diameter, a lip or shoulder or other features to facilitate substantially gas tight connections with the fuel cell tubes and the fuel feed tubes. 
         [0036]    The manifold member  10  as described above has a compact shape and design that allows for positioning of a manifold member  10  closely to the fuel cell tubes  18  and allows for the mounting of circuit boards  24  outside of a hot zone of the fuel cell system  15 . Additionally, the fuel cell system  15  provides passive fuel distribution and flow control such that a substantially similar amount of fuel is routed to each of the fuel cell tubes  18 . 
         [0037]    Further, the manifold member  10  also provides a mechanically compliant manifold member  10  allowing variations in the position of the manifold member  10  relative to the fuel cell tubes  18 . The fuel cell system  15  includes internal reformers  52  that heat fuel inside the fuel cell tubes  18 , thereby allowing a low-temperature seal between the fuel cell tubes and the manifold member  10 . 
         [0038]    The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description, rather than limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.