| 摘要 |
<p>A PEM fuel cell (12) operating on substantially pure hydrogen (32) and air (26) has an exhaust flow control valve (37) at the exit of the anode fuel reactant flow field, said valve being normally closed during steady state low or medium power operation, so that the concentration of nitrogen in the fuel reactant flow fields, by diffusion across the membrane from the cathode, will approach the average concentration of nitrogen in the oxidant, thereby limiting the concentration of hydrogen to a corresponding low complementary amount, which reduces the diffusion of hydrogen across the membrane for consumption at the cathode, thereby increasing the efficiency of operation of the fuel cell. A current sensor (40) allows a controller (46) to open an exhaust flow control valve (37), thereby drawing much higher amounts of hydrogen into the fuel reactant flow field of the anode to support generation of power at high current densities without hydrogen starvation.</p> |
