Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to fuel cell assemblies and, more particularly, to the oxidation and fuel distribution to fuel cells, such as solid oxide fuel cells.  
         [0002]     A fuel cell is an energy conversion device that produces electricity by electrochemically combining a fuel and an oxidant across an ionic conducting layer. One typical construction of a high temperature fuel cell bundle is an array of axially elongated tubular shaped connected fuel cells and associated fuel and air distribution equipment. Other fuel cell constructions include planar fuel cells comprising flat single members. Exemplary planar fuel cells include counter-flow, cross-flow and parallel flow varieties. The members of a typical planar fuel cell comprise tri-layer anode/electrolyte/cathode components that conduct current from cell to cell and provide channels for gas flow into a cubic structure or stack.  
         [0003]     Fuel cell stacks, such as solid oxide fuel cell stacks, have demonstrated a potential for high efficiency and low pollution in power generation. In a solid oxide fuel cell, upon electrochemically combining a fuel and an oxidant across an ionic conducting layer, an oxygen ion (0 2− ) transported across the electrolyte produces a flow of electrons to an external load.  
         [0004]     Oxidant, generally air, performs two main functions in the fuel cell stack. As discussed above, the oxidant electrochemically reacts with fuel to generate electric power. In addition, the oxidant is utilized to remove excess heat away from the cell. The waste heat generated in a solid oxide fuel cell at its operating temperature of about 600° C. to about 1300° C. is typically removed via the oxidant to maintain a desired temperature level of the fuel cell components, such as the anode, cathode and electrolyte.  
         [0005]     For the stack to operate at maximum efficiency, all of the cells in the stack should operating at substantially the same operating temperature and have substantially the same reaction rate. In order to achieve this maximum efficiency, each cell requires about an equal amount of oxidant and fuel to be delivered.  
         [0006]     Accordingly there is a need in the art to have an improved oxidant and fuel distribution system that can consistently deliver oxidant and fuel to the entire cell.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     An oxidant distribution system for a fuel cell assembly includes a fuel cell having at least one oxidant inlet and at least one oxidant outlet, a housing surrounding the fuel cell and an insulation layer positioned between the housing and the fuel cell. The insulation layer defines a cavity adjacent to the oxidant inlet for channeling oxidant flow to the oxidant inlet. A fuel distribution system for a fuel cell assembly including similar features is also disclosed.  
         [0008]     These and other aspects, advantages, and salient features of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic illustration of an oxidant distribution system in accordance with one embodiment of the invention;  
         [0010]      FIG. 2  is a schematic illustration of a side view of an oxidant distribution system of  FIG. 1 , in accordance with one embodiment of the invention;  
         [0011]      FIG. 3  is a schematic illustration of an oxidant distribution system in accordance with another embodiment of the invention;  
         [0012]      FIG. 4  is a isometric view of a fuel cell;  
         [0013]      FIG. 5  is a schematic illustration of a side view of an oxidant distribution system of  FIG. 3 , in accordance with one embodiment of the invention; and  
         [0014]      FIG. 6  is a schematic illustration of a fuel distribution system in accordance with one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     An oxidant distribution system  10  for a fuel cell assembly comprises a fuel cell  12 , such as a solid oxide fuel cell, having at least one oxidant inlet  14  and at least one oxidant outlet  16 , as shown in  FIG. 1  and  FIG. 2 . A housing  18  surrounds the fuel cell  12  and bounds an insulation layer  20  that is positioned between the housing  18  and the fuel cell  12 . Typically, insulation layer  20  comprises a rigid refractory material, such as a ceramic.  
         [0016]     The insulation layer  20  defines at least a first cavity  22  adjacent to the at least one oxidant inlet  14  for channeling oxidant flow to the at least one oxidant inlet  14  from an oxidant supply feed  24 .  
         [0017]     In one embodiment, first cavity  22  is shaped such that a portion of first cavity  22  adjacent to the oxidant supply feed  24  substantially mates with said supply feed  24  and a second portion of first cavity  22  adjacent to the oxidant inlet  14  substantially mates with the oxidant inlet  14 . Accordingly, the insulation layer  20  abuts or comes up adjacent to the oxidant supply feed  24  and abuts or comes up adjacent to the oxidant inlet  14 , thereby defining first cavity  22 . Typically, the cross-section of first cavity  22  at the oxidant inlet  14  is greater than the cross-sectional size of the first cavity  22  at the oxidant supply feed  24  thereby creating a diffuser effect that distributes oxidant more uniformly to the oxidant inlet  14  of the fuel cell  12 . In one embodiment of the invention, an internal surface  26  of first cavity  22  is roughened  28  to enhance turbulent flow therethrough.  
         [0018]     Oxidant distribution system  10  further comprises a second cavity  30  defined by insulation layer  20  adjacent to the at least one oxidant outlet  16  for channeling oxidant flow from the oxidant outlet  16  to an oxidant exit port  32 . The second cavity  30  is shaped such that a first portion of the second cavity  30  adjacent to the oxidant exit port  32  substantially mates with said exit port  32  and a second portion of said second cavity  30  adjacent to the oxidant outlet  16  substantially mates with the oxidant outlet  16  so as to channel oxidant flow from said fuel cell  12 . In one embodiment, the cross-sectional size of said first portion of the second cavity  30  is greater than the cross-sectional size of the second portion thereby creating a reducer effect as the oxidant exits the oxidant outlet  16  of said fuel cell  12 .  
         [0019]     The advantages of this oxidant distribution system  10  are numerous. By using the insulation layer  20  as the oxidant distributor, the system has an overall reduction in the number of parts required. Additionally, by eliminating an additional air distributor, more insulation can be packed into a given housing  18  improving the overall efficiency of the system. Moreover, the use of the insulating layer  20  as the oxidant supply flow path also allows the oxidant leaving the first cavity  22  to retain more of its heat and creates efficiency advantages in certain system configurations.  
         [0020]     Another embodiment of an oxidant distribution system  100  for a fuel cell assembly comprises a fuel cell  112 , such as a solid oxide fuel cell, having an array of oxidant inlets  114  and at least one oxidant outlet  116 , as shown in  FIGS. 3, 4  and  5 .  
         [0021]     A housing  118  surrounds the fuel cell  112  and bounds an insulation layer  120  that is positioned between the housing  118  and the fuel cell  112 . Typically, insulation layer  120  comprises a rigid refractory material, such as a ceramic.  
         [0022]     The insulation layer  120  defines an array of channels  122 . A respective channel  122  within the array is matingly positioned adjacent to at least one respective inlet  114  for channeling oxidant flow to that respective inlet  114  from an oxidant supply feed  124 . The typical arrangement comprises a respective channel  122  positioned adjacent to a respective inlet  114 , however, this is not a limitation of this invention. In fact, other configurations contemplated by this invention include a single channel  122  channeling oxidant flow to multiple inlets  114  and multiple channels  122  channeling oxidant flow to a single inlet  114 .  
         [0023]     In another embodiment of the invention, a fuel distribution system  210  for a fuel cell assembly comprises a fuel cell  212 , such as a solid oxide fuel cell, having at least one fuel inlet  214  and at least one fuel outlet  216 , as shown in  FIG. 6 . A housing  218  surrounds the fuel cell  212  and bounds an insulation layer  220  that is positioned between the housing  218  and the fuel cell  212 . Typically, insulation layer  220  comprises a rigid refractory material, such as a ceramic.  
         [0024]     The insulation layer  220  defines at least a first cavity  222  adjacent to the at least one fuel inlet  214  for channeling fuel flow to the at least one fuel inlet  214  from a fuel supply feed  224 .  
         [0025]     While typical embodiments have been set forth for the purpose of illustration, the foregoing description should not be deemed to be a limitation on the scope of the invention. For example, while hybrid systems are depicted, simple systems are also encompassed within this invention. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention.

Technology Category: h