Higher load current of PEMFC

质子交换膜燃料电池的性能在很大程度上取决于其水管理。由于气体扩散层和催化剂层分为微孔介质和基于碳的不透明材料，因此，气体扩散层和催化层中出现的液泛现象很难测量和/或观察。另一方面，质子交换膜燃料电池内气液两相流动的数值模拟也是最近发展起来的。在这一模拟过程中，MM模型是处理GDL等多孔介质中两相现象的数学模型之一，它似乎成功地模拟了单元操作过程中的水淹。然而，对仿真的评价还不够充分。只有通过比较仿真和实验的IV特性，才能对其进行评价。在本研究中，我们用间接法测量了气液两相中的含水饱和度，并比较了它们的Res…与模拟得到的结果相比有更大的误差。我们制作了一个简单的交叉槽，整个流体在GDL中强制流动，并测量了GDL的压差，根据压差估算了含水饱和度比。在数值模拟中，我们建立了基于MM模型的全守恒方程，并考虑了交叉型胞体的边界条件。在仿真中，我们还进行了负载电流阶跃变化的暂态计算，在测量中，电池电位在0.5A/cm2负载电流以上显著降低。我们成功地解释说，这种下降是由于浓度超过电位伴随着估计的含水饱和度造成的。含水饱和度随负载电流、增湿温度和气体利用率的增大而增大。这些操作条件被认为是控制气液相渗漏的关键参数。模拟的IV特性成功地重现了测量结果。但它们并不能说明在大电流区域出现了浓度过电位。模拟得到的压差与实测值在15%以内有较好的一致性。在暂态计算中，电池电势变化比较复杂。我们可以用几个时间常数来解释这一点，这些时间常数对应于细胞中正在进行的输运现象。较少

The performance of PEMFC largely depends on its water management. The flooding appeared in gas diffusion layer (GDL) and catalyst layer, which are main target to be managed, is difficult to measure and/or observe, because these layers are categorized as micro-porous media and opaque material based on carbon. On the other hand, the gas-liquid two-phase flow numerical simulation in PEMFC is developed recently. In this progress of simulation, the MM model, which is one of mathematical model to treat two-phase phenomena in porous media such as GDL, seems to successfully simulate the flooding during cell operation. However the evaluation of the simulation is not enough. Only the evaluation is based on the comparison of IV characteristic between simulation and experiment. The simulated two-phase phenomena, such as the water saturation ratio in GDL, have not been evaluated with experimental result.In this study, we measured the water saturation in GDL with indirect method and compared its res … More ult with that obtained from simulation. We fabricated a simple interdigitated cell where the whole fluid flows forcedly in GDL, and measured the differential pressure through GDL, and estimated the water saturation ratio from its differential pressure. In numerical simulation, we formulated the full conservation equations based on MM model, and executed with the boundary condition considering the interdigitated cell. In simulation we also executed the transient calculation in which the load current changed step-wisely.In measurement, the cell potential decreased significantly over 0.5A/cm2 load current. We successfully explained that this drop was caused by the concentration over potential accompanied with the water saturation estimated. The water saturation ratio increased with higher load current, humidification temperature, and gas utilization ratio. These operation conditions are noted as the key parameter to control the flooding in GDL. The simulated IV characteristics succeeded to reproduce the measured. But they could not show the concentration overpotential appeared in high current region. The differential pressure obtained from the simulation qualitatively agreed with the measured data within 15%. In transient calculation, the cell potential changed complexly. We could explain this with several time constant corresponding to the transport phenomena being progressed in cell. Less