Dynamics and Control of Liquid Water Movement in PEM Fuel Cells

PEM 燃料电池中液态水运动的动力学和控制

• 批准号: 0754715
• 负责人: Jay Benziger
• 金额: --
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-01 至 2011-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0754715&HistoricalAwards=false
• 关键词: Dynamics; Control; Liquid; Water; Movement

CBET-0754715BenzigerModel Polymer Electrolyte Membrane (PEM) fuel cell reactors are employed to elucidate the key physics of water transport to develop improved dynamic models and control systems. Previous models of PEM fuel cells have missed essential physics of the necessary hydraulic pressure to drive water transport through the gas diffusion layer (GDL), which results in water slugs blocking the gas flow channels and exhaust manifolds. Simplified model PEM fuel cells have helped identify the essential physics that govern the water transport dynamics in PEM fuel cells. New experiments are planned employing simplified model reactors to quantify the effects of surface tension, gravity, and viscosity for water transport in the GDL, the gas flow channels and the exhaust manifold. Flow visualization coupled with local current density measurements to identify better control systems to improve fuel utilization with minimal fuel recycle. The use of simplified model reactors can vastly improve our understanding of reaction and transport in fuel cells, assisting in their improved design, operation and control. Intellectual Merit: A new methodology for analyzing fuel cell operation, focusing on the fuel cell as a chemical reactor will be used. The PI's previous studies of the dynamics of a one-dimensional Stirred Tank Reactor (STR) PEM fuel cell unearthed complex behavior not previously recognized in fuel cell operation. The dynamic response of the STR PEM fuel cell showed that the positive feedback between water produced and proton conductivity in the membrane resulted in current ignition/extinction and steady state multiplicity. Past studies were with a model 2-dimensional segmented anode parallel channel fuel cell that demonstrated current ignition coupled with diffusive water flow in the polymer membrane resulted in current density fronts propagating along the flow channel. The results with the SAPC fuel cell demonstrate flooding in PEM fuel cells occurs due to water slug formation in the gas flow channels which blocks reactant supplies. This work shows how slug motion in the gas flow channels is correlated with local current density fluctuations. By improving knowledge of the basic physics in fuel cells it is possible to develop the channel-less self-draining PEM fuel cell that operates with dry feeds to temperatures of 130ºC with current densities 1 A/cm2. The self-draining fuel cell design has also led to the development of a variable area fuel cell that follows power demands with 100% fuel utilization and is insensitive to temperature. This project is to show the importance that GDL pore size, gravity, and gas velocity have in liquid droplet motion in fuel cell operation, and how that alters the current and power output. Experiments with model micro-fluidic systems to elucidate the dynamics of liquid motion in 2-phase micro-fluidic systems that can identify the necessary feed control to match variable power loads for PEM fuel cells will be done. The approach of employing model reactor systems to identify the essential physics of PEM fuel cell operation is unique. The complex reactor configurations employed in fuel cell development and research has provided integrated responses where the key physics is obscured. Only by the careful design of experimental systems to can isolate the essential physics of reaction and transport on a system scale will it be possible to design PEM fuel cells that optimize performance. Broader Impact: Fuel cells have been identified as an essential element of the hydrogen economy to reduce demand for fossil fuels and improve the environment. Water management in PEM fuel cells is a major stumbling block to robust and simplified operation that is essential for consumer acceptance. The fundamentals of fuel cell dynamics and control addressed here are critical to the engineering design of efficient fuel cells. The data and models developed from this work will serve as a basis for systems engineering of PEM fuel cell systems to make them an economically viable technology. These fundamental studies have also provided an outstanding forum for educational outreach. Past work engaged more than ten undergraduates and three high school teachers in this research. Experiments and teaching modules have been put in place for grades 9-12 in three local high schools and these will be expanded to introduce energy technology to new students

CBET-0754715采用Benziger模型聚合物电解质膜（PEM）燃料电池反应器来阐明水传输的关键物理过程，以开发改进的动态模型和控制系统。PEM燃料电池的先前模型已经错过了驱动水通过气体扩散层（GDL）的必要液压的基本物理特性，这导致水栓阻塞气体流动通道和排气歧管。简化模型PEM燃料电池有助于确定控制PEM燃料电池中水传输动力学的基本物理特性。新的实验计划采用简化的模型反应器，以量化的表面张力，重力和粘度的影响，在GDL，气体流动通道和排气歧管中的水运输。流场可视化与局部电流密度测量相结合，以确定更好的控制系统，从而提高燃料利用率，同时最大限度地减少燃料循环。使用简化的模型反应器可以大大提高我们对燃料电池中反应和传输的理解，有助于改进设计，操作和控制。智力优点：将使用一种新的方法来分析燃料电池的运行，重点是燃料电池作为一个化学反应器。PI以前对一维搅拌槽反应器（STR）PEM燃料电池的动力学研究发现了以前在燃料电池操作中没有认识到的复杂行为。STR质子交换膜燃料电池的动态响应表明，产生的水和质子导电性之间的正反馈导致电流点火/熄灭和稳态多重性。过去的研究是用模型2维分段阳极平行通道燃料电池，其证明了电流点火与聚合物膜中的扩散水流耦合导致电流密度前沿沿流动通道沿着传播。SAPC燃料电池的结果表明，PEM燃料电池中的溢流是由于在气体流动通道中形成水栓而发生的，水栓阻塞了反应物的供应。这项工作显示了如何在气体流动通道的段塞运动与局部电流密度波动。通过提高对燃料电池基本物理学的认识，有可能开发出无通道自排液PEM燃料电池，该电池在130ºC的温度下以干进料运行，电流密度为1 A/cm 2。自排放燃料电池设计还导致了可变面积燃料电池的发展，该可变面积燃料电池以100%的燃料利用率满足功率需求并且对温度不敏感。这个项目是为了显示GDL孔径，重力和气体速度在燃料电池操作中的液滴运动中的重要性，以及如何改变电流和功率输出。将进行与模型微流体系统的实验，以阐明两相微流体系统中的液体运动的动力学，该两相微流体系统可以确定必要的进料控制以匹配PEM燃料电池的可变功率负载。 采用模型反应器系统来识别PEM燃料电池操作的基本物理的方法是独特的。燃料电池开发和研究中采用的复杂反应堆配置提供了综合的反应，其中关键的物理学是模糊的。只有通过仔细设计实验系统，才能在系统规模上隔离反应和传输的基本物理过程，才有可能设计出性能最佳的PEM燃料电池。更广泛的影响：燃料电池已被确定为氢经济的基本要素，以减少对化石燃料的需求并改善环境。PEM燃料电池中的水管理是稳定和简化操作的主要障碍，这对消费者的接受至关重要。燃料电池动力学和控制的基本原理在这里解决的工程设计的高效燃料电池的关键。从这项工作中开发的数据和模型将作为PEM燃料电池系统的系统工程的基础，使它们成为经济上可行的技术。 这些基础研究也为教育推广提供了一个出色的论坛。过去的工作中，有十多名大学生和三名高中教师参与了本研究。在三所当地高中的9-12年级进行了实验和教学模块，并将扩大这些实验和教学模块，向新生介绍能源技术