Enhancement effects of variable gradient channel on output performance of fuel cells

Abstract

The gas channel design of proton exchange membrane fuel cell (PEMFC) has a significant impact on the transport of the oxygen and water, which indirectly affects the performance of the PEMFC. In this paper, the gradient gas channel is studied first, and based on the optimal structure, two different variable gradient design schemes are proposed. The results show that the output performance of PEMFC can be improved by adopting the gradient channel design only at the cathode. When the height of the cathode channel is gradually reduced from 1 mm to 0.1 mm, the net power density is 3.88 % higher than that of the traditional straight channel at 0.3 V. Only by moving the end position of height change to the inlet further improves the output performance. When the end position is 18 mm away from the inlet, the maximum peak net power density is 0.597 W/cm², which is 5.68 % higher than the traditional straight channel. By establishing the evaluation index of fluctuation, it is revealed that the performance improvement in the variable gradient channel can be attributed to the improvement of the oxygen concentration and the uniformity in latter part of the channel while keeping the water concentration in the cathode channel almost unchanged. Finally, the dimensionless correlation between net power density and outlet height, end position and voltage under low voltage is established to guide the design of cathode channel.