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Fig.4 Measured hydrogen concentration at the fuel outlet with various temperature distribution of cooling plate. The average current density is 300mA/cm-, the hydrogen and oxygen utilization are 80% and 50%, respectively, and hydrogen concentration is ¿5% at the inlet.

Fig.4 Measured hydrogen concentration at the fuel outlet with various temperature distribution of cooling plate. The average current density is 300mA/cm-, the hydrogen and oxygen utilization are 80% and 50%, respectively, and hydrogen concentration is ¿5% at the inlet.

density.

Fig.5 sliows the characteristics of hydrogen concentration deviation at the fuel outlet under various oxygen utilization in the easel. The hydrogen concentrations near the air inlet area decrease as oxygen utilization increasing.- It suggests that deviation of oxygen concentration in the reaction area becomes larger with higher utilization of oxygen, then current density increase at the area where the oxygen concentration is relatively high. Fig.6 shows the characteristics of oxygen concentration deviation at the air outlet under various hydrogen utilization. The oxygen concentration slightly changes as hydrogen utilization changing.

0.2 0.4 0.6 0.8 Distance from Air inlet

Fig.5 Measured hydrogen concentration at the fuel outlet under various oxygen utilization. The average current density is 300mA/cm2, the hydrogen and oxygen utilization are 80% and 40-80%, respectively, and hydrogen concentration is 65% at the inlet.

0.2 0.4 0.6 0.8 Distance from Air inlet

0.2 0.4 0.6 0.8 Distance from Fuel inlet

Fig.6 Measured oxygen concentration at the air outlet under various hydrogen utilization. The average current density is 300mA/cm2, the hydrogen and oxygen utilization are 70-85% and 50%, respectively, and hydrogen concentration is 65% at the inlet.

0.2 0.4 0.6 0.8 Distance from Fuel inlet

Fig.5 Measured hydrogen concentration at the fuel outlet under various oxygen utilization. The average current density is 300mA/cm2, the hydrogen and oxygen utilization are 80% and 40-80%, respectively, and hydrogen concentration is 65% at the inlet.

Fig.6 Measured oxygen concentration at the air outlet under various hydrogen utilization. The average current density is 300mA/cm2, the hydrogen and oxygen utilization are 70-85% and 50%, respectively, and hydrogen concentration is 65% at the inlet.

Simulation

Calculated results of hydrogen concentration deviation at the fuel outlet compare with measured value under oxygen utilization of 50 and 70% in Fig.7. The calculated results almost correspond with the measured one. Fig.8 shows the contour plots of the distributions of current density over the middle (No.3 and 4) cells of the 6-cell-stack, which were calculated under oxygen utilization of 50 and 70%, hydrogen utilization of 80%, average current density of 300mA/cm2, and hydrogen concentration of 65% at the inlet. The current density varies in the range of 250-360mA/cm2 over the electrode under oxygen utilization of 50%. Under oxygen utilization of 70%, the range of the current density expands into 230-380mA/cm2.

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