FUEL CELL SYSTEM AND METHOD OF MONITORING HYDROGEN CONCENTRATION IN THE ANODE AND PURGING THE ANODE WITH HYDROGEN-RICH GAS

摘要

A fuel cell stack includes: a first cell having a first fuel gas flow pat h; and a second cell having a second fuel gas flow path constructed to have a specific flow path structure having a higher potential for a decrease in c oncentration of a fuel gas than that of the first fuel gas flow path during power generation. A sensor is located on the second cell to detect a decreas e in concentration of the fuel gas during power generation. In one exemplifi ed structure, a groove formed on an anode separator of the second cell as th e second fuel gas flow path has a restriction element to narrow the sectiona l area of flow passage. A hydrogen concentration sensor is located in a non- narrowed area in the downstream of the restriction element having a lower pr essure level. Impurity gas discharge control discharges an anode off gas out of the fuel cell stack, in response to detection of a decrease in hydrogen concentration to or below a preset reference level by the hydrogen concentra tion sensor. This arrangement of the invention enables the effective use of the fuel gas and prevents deterioration of membrane electrode assemblies of the fuel cell stack by carbon oxidation in an anode dead end-type fuel cell system.