Modeling and Experimental Study of PEM Fuel Cell Transient Response for Automotive Applications

This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane (PEM) fuel cell stack to step changes in load, which are characteristic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and experiment are based on a low pressure 5 kW proton exchange membrane fuel cell (PEMFC) stack, which is similar to those used in several of Tsinghua's fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008.     

三维聚合物电解质膜燃料电池中水的输运模拟

针对新型螺旋形加压聚合物电解质膜燃料电池,提出了一种液态水生成和输运效应的数值模型.该数值模型基于燃料电池的物理机理、流体流动、传热导、多孔介质中的传质、电化学反应、含相变的多相流动、电流输运、多孔介质和固体导电区域中的位势场以及穿过聚合物膜的水的输运设计优化过程.在分析中还使用了燃料电池模型.例如,电化学模型--用于预测局部电流密度和电压分布;位势场模型--用于预测多孔介质以及固体导电区中的电流和电压;多相混合物模型--用于预测在多孔扩散层中的液态水和气体流;薄膜多相模型--用于研究气体流道中的液态水流.最后给出了聚合物电解质膜燃料电池液态水生成和输运的理论模型的数值结果,包括催化层和膜中的H2,O2和H2O的质量和克分子数的等值线图.     

Analysis of Water Management in Proton Exchange Membrane Fuel Cells

Introduction Fuel cells provide an environmentally friendly high- efficiency power source that is not limited by the Carot efficiency. The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising can- didate for electric vehicles …     

质子交换膜燃料电池性能影响因素的数值分析

为研究交指流场质子交换膜燃料电池的输出性能,分析影响其性能的因素,寻找改善其性能的可行措施,探讨了使用交指流场流道的必要性和优越性,建立了包括质子交换膜燃料电池阴极/阳极侧流道、扩散层和催化层以及质子交换膜在内的完整的稳态、三维、两相数学模型.基于计算流体力学方法,用该模型对交指流场质子交换膜燃料电池的全流场进行了统一的数值计算以模拟其输出性能,分析了流场流型、氧化剂种类、反应气体进气速度、质子交换膜厚度和双极板筋宽对质子交换膜燃料电池输出性能的影响,确定了提高质子交换膜燃料电池输出性能的一些方法.将理论模型的模拟计算结果与实验结果进行比较,两者较为吻合.     

Applications of M/N/C analogue catalysts in PEM fuel cells and metal-air/oxygen batteries: Status quo,challenges and perspectives

To meet the sharp increase in demand for clean and renewable energy, it is necessary to develop new energy-conversion and storage technologies, such as proton exchange membrane fuel cells (PEMFCs) and metal-air/oxygen batteries (MABs). Due to the sluggish reaction kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in the cathodes of PEMFCs and MABs, significant amounts of precious metal catalysts need to be used, driving up the cost of fuel cells and MABs and thereby hindering their commercialization on a large scale. Transition metal and nitrogen co-doped carbonaceous catalysts (M/N/C) have high catalytic activity towards the ORR and OER once the catalysts are modified with certain promoters/additives. In addition, M/N/C catalysts can be prepared from abundant, inexpensive materials, making their cost negligible compared with precious metal catalysts, a development that would efficiently decrease the cost of PEMFCs and MABs. In last decade, numerous researchers have attempted to realize these applications of M/N/C catalysts, and some exciting results have been achieved, making these promising replacements for precious metal catalysts. However, some serious problems and significant challenges remain. In this paper, we review the research on the application of M/N/C analogue catalysts in PEMFCs and MABs in the last 10 years, indicate the remaining challenges, and suggest the future research directions.     

关于对电子邮件安全增强（PEM）机制评述的商榷

本文扼要介绍了电子邮件安全增强机制，分析了Ｓ．Ｔ．Ｋｅｎｔ的“Ｉｎｔｅｒｎｅｔ Ｐｒｉｆａｃｙ Ｅｎｈａｎｃｅｄ Ｍａｉｌ”一文中一例报文各字段的功能，进一步给出了源发证书字段的编码值；在此基础上对Ｊ．Ｐ．Ａｎｄｅｒｓｏｎ在Ｃｏｍｐｕｔｉｎｇ Ｒｅｖｉｅｗｓ“的评述提出了异议，肯定了ＰＥＭ机制的前景。     

PEM钻井液体系性能评价与应用

北黄海海域LHIV地区油藏为低孔、低渗砂岩储层,油层易受到钻井液伤害.为保护油气层,优选了适用于该油层的低伤害PEM钻井液体系,室内试验表明PEM钻井液体系具有滤失量低、流变性、热稳定性好、具有一定抗污染能力,抑制性好等特点.PEM钻井液体系成功地应用于LHIV18-3-1井钻进,未出现明显井塌、井漏事故,取得了良好的效果.     

SOFC PEM联合发电系统的不确定性分析

以固体氧化物燃料电池与质子交换燃料电池(SOFC PEM)联合发电系统为研究对象,以系统操作参数作为不确定参数,采用基于拉丁超立方体抽样法的不确定分析方法,即包括以适宜的概率分布函数来表述和量化不确定因素并将不确定性传播到确定性模型来建立输出结果的概率分布规律,进而分析系统操作变量的不确定性对系统净电功率的影响。不同于传统的灵敏度分析方法,考虑参数的概率结构,评价多个参数的相对重要性。结果表明：高SOFC电堆操作温度、低燃料流量和低SOFC燃料利用率有利于减少系统净电功率因不确定因素引起的偏差和波动,但同时以减少系统净电功率为代价。不确定性分析可为在不确定条件下设计参数的优化提供依据。     

中频反应磁控溅射制备具有光致亲水性TiO2薄膜

采用中频反应磁控溅射方法在玻璃表面制备了TiO2薄膜,为使薄膜获得理想的化学配比和较高的沉积速率,使用了等离子体发射光谱监控法(Plasma Emission Monitor,PEM)对溅射过程进行控制。对部分样品进行了退火处理。利用台阶仪测膜厚,X射线衍射(XRD)对薄膜的沉积速率及结构进行测试分析,并对部分沉积态和经过热处理的薄膜样品进行了透光性测试和光照实验。研究了温度,PEM工作点等不同工艺条件对薄膜光致亲水性等性能的影响。部分薄膜经过1h左右的紫外光照射,得到了很好的亲水性效果,其表面的水接触角达到了小于1°的水平。     

商业可行的质子交换膜制氢催化剂制备和评价

通过构建高活性和高稳定性的电催化剂来降低贵金属成本,是近期大规模开发质子交换膜(proton exchange membrane, PEM)电解水制氢技术的必然路径。采用简便、高效且易于放大(公斤级)的方法制备了纳米级IrO₂和Ir_xRu_1-xO₂催化材料,并对合成条件进行了优化。利用三电极体系进行析氧活性测试,结果表明,在10 mA/cm²下IrO₂和Ir_xRu_1-xO₂过电位分别达到274 mV和230 mV,比商业IrO₂分别降低39 mV和83 mV。在基于Nafion~?117质子交换膜的电解槽中对这些催化剂进行了评价,在60℃和2 A/cm²电流密度下电解电压低至2 V,且可稳定运行200 h以上。这些结果揭示了高活性的铱基氧化物在PEM电解水中大规模应用的可行性。