【作者】 马海鹏；

【导师】 张华民；

【作者基本信息】 中国科学院研究生院（大连化学物理研究所） ， 化学工程， 2007， 博士

【摘要】 质子交换膜燃料电池(PEMFC)“水淹”问题严重影响了电池性能、稳定性及其耐久性。通过对流场水分布及其排水过程的研究将有助于理解电池排水机制,为改进流场和优化电池操作模式提供一定的理论指导,对促进PEMFC技术的发展和产业化具有十分重要的意义。设计单流道可视化PEM单池以研究液态水在流道内的传递行为。采用首次液态排水时间和平均液态排水间隔时间等参数对流道照片进一步处理以获取流道排水过程的相关量化信息。结合可视化技术与压降测量作为流道内液态水的检测手段,采用平均压降波动评价流道排水状况。发现流道存在特征流速,此时流道内液态水积累最严重。只有大于该流速值,提高流速才能缓解流道内的液态水积累。分析特征流速成因及流道尺寸、扩散层表面特性、电流密度和不同反应气体对其影响,给出流道特征流速的经验公式,计算值与实际电池运行结果符合良好。设计120 cm~2可视化PEM单池,研究了阴极直条流场内的液态水分布及其传递行为。通过测量不同位置流道压降,说明反应气体分配不均为流场水分布不均的主要成因。更多还原

【Abstract】 Water flooding has great influence on the performance, stability and durability of proton exchange membrane fuel cells (PEMFCs). The study of water distribution and removal would be helpful to the understanding of discharging mechanism in fuel cells and give theoretical guidance to the optimization of the flow field and operation style. Therefore, the issue is crucial for the development, application and industrialization of PEMFCs.A transparent PEM single cell with single straight channel in the cathode was designed to study water transportation in the cathode channel. To get the quantified information of the water removal, two parameters - time of the first liquid water discharging and mean interval time between adjacent water dischargings were introduced to further process the channel photos.The combination of visualization technique and pressure-drop monitor was used as the diagnostic tool to detect liquid water in the cathode channels of PEMFCs. The mean fluctuation of pressure-drop was introduced to evaluate the flow channel discharging. It was found that there was a characteristic gas velocity,at which liquid water accumulation in the flow channel was the most. And the amount of maintained water in the channel increased until gas velocity above the critical value. As well as the cause of the phenomena, effects of channel dimension, surface property of the gas diffusion layer, current density anddifferent gas on the characteristic velocity were studied. An empirical expression for the critical velocity was developed and the calculated results were in accord with the experiments.A transparent PEM single cell with 120 cm~2 active area was designed to study water behavior in the straight flow field. The pressure-drop values of different channels proved that uneven reactant distribution was the main cause of the uneven water distribution in the flow field.更多还原