1.  Field of the Inventions
The present inventions are related to fuel cells and fuel cell reactant supply systems. 
2.  Description of the Related Art
Fuel cells, which convert reactants (i.e. fuel and oxidant) into electricity and reaction products, are advantageous because they possess higher energy density and are not hampered by lengthy recharging cycles, as are rechargeable batteries, and are relatively small, lightweight and produce virtually no environmental emissions.  Nevertheless, the inventors herein have determined that conventional fuel cells are susceptible to improvement.  More specifically, the inventors herein have determined that it would be advantageous to provide improved systems for supplying reactants to the fuel cell electrodes. 
Conventional fuel cell reactant supply systems continuously pump a reactant stream past the fuel cell electrodes and the reactants react with the electrodes as they travel along the surface of the electrodes.  The inventors herein have determined that the reactant concentration at the inlet end of an electrode is much greater than the reactant concentration at the outlet end and, as a result, the reaction conditions vary along the length of the electrode surfaces.  Such variations make it difficult to efficiently utilize the entire reactive surface of the electrodes.  In addition, the reaction products from the fuel consumed at the inlet mix with the incoming fuel, further reducing the efficiency of the fuel cell.