Fuel Cell Flow Channels and Flow Fields

Abstract

A fuel cell anode flow field includes at least one flow channel with a cross-sectional area that varies along at least a portion of its length. In some embodiments, the channel width decreases along at least a portion of the channel length according to a natural exponential function. This type of anode flow field can improve performance, reduce fuel consumption and/or reduce detrimental effects such as carbon corrosion and catalyst degradation, thereby improving fuel cell longevity and durability. When operating the fuel cell on either a substantially pure or a dilute fuel stream, this type of anode flow field can provide more uniform current density. These flow channels can be incorporated into reactant flow field plates, fuel cells and fuel cell stacks.

What is claimed is: 
     
         1 . A fuel cell reactant flow field plate comprising:
 (a) a reactant inlet;   (b) a reactant outlet; and   (c) an at least one channel formed in a major surface of said fuel cell reactant flow field plate, said at least one channel having a floor and a pair of side walls extending between said floor and said major surface, said at least one channel having a channel length that fluidly interconnects said reactant inlet and said reactant outlet, said side walls separated by a channel width, said floor and said major surface separated by a channel depth,   wherein said at least one channel has a cross-sectional area that is substantially constant along a first portion of said channel length and that decreases along a second portion of said channel length.   
     
     
         2 . The fuel cell reactant flow field plate of  claim 1 , wherein said channel depth is substantially constant and said channel width decreases along said second portion of said channel length. 
     
     
         3 . The fuel cell reactant flow field plate of  claim 1 , wherein said channel depth is substantially constant and said channel width decreases monotonically along said second portion of said channel length. 
     
     
         4 . The fuel cell reactant flow field plate of  claim 1 , wherein said channel depth is substantially constant and said channel width decreases continuously along said second portion of said channel length. 
     
     
         5 . The fuel cell reactant flow field plate of  claim 1 , wherein said channel portion having a decreasing cross sectional area is proximal said reactant inlet and said channel portion having a substantially constant cross-sectional area is proximal said reactant outlet. 
     
     
         6 . The fuel cell reactant flow field plate of  claim 1 , wherein said channel portion having a substantially constant cross-sectional area is proximal said reactant inlet and said channel portion having a decreasing cross-sectional area is proximal said reactant outlet. 
     
     
         7 . The fuel cell reactant flow field plate of  claim 1 , wherein said cross-sectional area decreases exponentially along said second portion of said channel length. 
     
     
         8 . The fuel cell reactant flow field plate of  claim 7 , wherein said channel depth is substantially constant and said channel width decreases exponentially along said second portion of said channel length. 
     
     
         9 . The fuel cell reactant flow field plate of  claim 7 , wherein said channel portion having an exponentially decreasing cross-sectional area is proximal said reactant inlet and said channel portion having a substantially constant cross-sectional area is proximal said reactant outlet. 
     
     
         10 . The reactant flow field plate of  claim 7 , wherein said channel portion having a substantially constant cross-sectional area is proximal said reactant inlet and said channel portion having an exponentially decreasing cross-sectional area is proximal said reactant outlet. 
     
     
         11 . The reactant flow field plate of  claim 10 , wherein said plate has a substantially circular major planar surface, said reactant outlet is centrally disposed on said plate, and said reactant inlet is disposed at the circumferential edge of said plate. 
     
     
         12 . The fuel cell reactant flow field plate of  claim 10 , wherein said fuel cell reactant flow field plate has a substantially trapezoidal major planar surface. 
     
     
         13 . The fuel cell reactant flow field plate of  claim 7 , wherein said at least one channel is a plurality of channels. 
     
     
         14 . The fuel cell reactant flow field plate of  claim 1 , wherein said at least one channel is a plurality of channels. 
     
     
         15 . The fuel cell reactant flow field plate of  claim 14 , wherein said plurality of channels defines a flow field area. 
     
     
         16 . The fuel cell reactant flow field plate of  claim 14 , wherein said plurality of channels is arranged in a nested configuration. 
     
     
         17 . The fuel cell reactant flow field plate of  claim 1 , wherein said at least one channel extends in a meandering path between said reactant inlet and said reactant outlet. 
     
     
         18 . The fuel cell reactant flow field plate of  claim 16 , wherein said at least one channel extends in a serpentine path along at least a portion of said channel length. 
     
     
         19 . The fuel cell reactant flow field plate of  claim 16 , wherein said at least one channel extends in a sinusoidal path along at least a portion of said channel length. 
     
     
         20 . The fuel cell reactant flow field plate of  claim 17 , wherein said at least one channel is a plurality of channels.