Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Patent
1998-03-06
2000-03-28
Bell, Bruce F.
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
429 20, 429 24, 429 25, 429 26, 429 32, 429 34, 429 35, 429 38, 429 39, H01M 800
Patent
active
060429550
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fuel cell having a fuel cell structure including an anode electrode and a cathode electrode which sandwich an electrolyte membrane therebetween and separators which sandwich the fuel cell structure therebetween, and a method of controlling the fuel cell.
BACKGROUND ART
Solid polymer electrochemical fuel cells comprise a plurality of unit cells each comprising an electrolyte membrane in the form of an ion exchange membrane and a catalytic electrode and a porous carbon electrode which are disposed one on each side of the electrolyte membrane. Hydrogen supplied to the anode of the fuel cell is converted into hydrogen ions on the catalytic electrode, which move through the electrolyte membrane that has been humidified to an appropriate extent toward the cathode of the fuel cell which is made of porous carbon. An oxygen containing gas or air is supplied to the cathode electrode to generate water through a reaction between the hydrogen ions and the oxygen on the cathode electrode. Electrons which are generated at this time are led to an external circuit for use as electric energy as a direct current. Such a fuel cell is disclosed in Japanese laid-open patent publication No. 6-20713. In view of the fact that when the water is supplied to humidify the electrolyte membrane, the water may be collected as a drain on the surfaces of the separators depending on the conditions in which the fuel cell operates, the disclosed fuel cell has parallel grooves defined in the separators for supplying a fuel gas and an oxygen containing gas, respectively, the grooves being directed downwardly in the direction of gravity for draining the collected water in order to enable the solid polymer electrolyte membrane to generate electric energy at a sufficiently high level.
Specifically, since the operating temperature of fuel cells of the type described above is relatively low, water generated by a reaction between the fuel gas and the oxygen containing gas and also water added to the fuel gas or the oxygen containing gas to humidify the electrolyte membrane tend to be condensed in the gas passages in the separators, closing the gas passages thereby to lower the performance of the fuel cells.
As shown in FIG. 31 of the accompanying drawings, if a fuel cell 4 has a number of fuel cell cells 2 stacked along the direction of gravity, then water droplets are collected in regions (e.g., regions 6a or 6b) where the flow of a fuel gas or an oxygen containing gas that has been humidified, greatly lowering the performance of those fuel cells 2 which are positioned adjacent to the fuel cells 2 including the regions 6a or 6b as compared to the other fuel cells 2.
In the other fuel cells 2, since the fuel gas and the oxygen containing gas flow in directions perpendicular to the direction of gravity, condensed water is liable to be collected in portions of the fuel cells 2, so that voltages generated by the fuel cells 2 will vary from each other. Furthermore, because the water in the gas passages is temporarily discharged, it is not possible to prevent voltages generated by the fuel cells 2 from varying from each other.
The fuel cell disclosed in Japanese laid-open patent publication No. 6-20713 has such a structure that the fuel gas and the oxygen containing gas flow in directions perpendicular to the direction of gravity along the solid polymer electrolyte membrane, the anode electrode, and the cathode electrode, and cooling water flows perpendicularly to the fuel gas and the oxygen containing gas flow. While this structure is effective to alleviate shortcomings caused by unstable voltages that possibly occur due to generation and elimination of condensed water, it has been confirmed with the disclosed structure that the current density is temporarily increased owing to a temperature rise at the outlets of the fuel cells.
More specifically, it has been confirmed that, as shown in FIG. 32 of the accompanying drawings, when a fuel gas such as a hydrogen containing gas and an oxygen containing g
REFERENCES:
patent: 5736269 (1998-04-01), Okamoto et al.
Bell Bruce F.
Honda Giken Kogyo Kabushiki Kaisha
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