Numerical and Experimental Analysis of Current Density Distribution and Transient Response for Polymer Electrolyte Membrane Fuel Cell

聚合物电解质膜燃料电池（PEFC）具有能源效率高、环境负荷小的特点，有望应用于电动汽车电源和分布式电源。由于聚合物电解质膜（PEM）的离子电导率和电渗透系数取决于其吸水性和温度，因此控制其吸水性和温度以使其均匀发电，了解其温度分布和水分子行为具有重要意义。掌握电池电势对负荷和反应物流量变化的瞬态响应也很重要。首先，为了分析发电的稳态特性，我们开发了考虑质量、电荷和能量平衡的PEFC数值代码，并分析了其与实验条件（如电池温度、利用率等）相对应的特性。其中，激活过电位为1 × 1，与测量的电流-电位特性一致。从数值结果可以理解，电流分布的变化是由于PEM的吸水量变化引起的，而这是由加湿器温度控制的。为了验证这种数值电流分布的变化，我们使用分段电极实际测量了它。电流分布的实验结果与分析结果一致。接下来，我们实验和数值研究了电池电位的瞬态响应，快速改变负载电流和反应物气体流速。当H_22/O_2流速一定时，电池电位对负载电流变化的响应可以用双电层电容和反应电阻的代表时间来描述。当模拟转化气/空气流量一定时，由于扩散阻力较大，响应时间较长。在负载电流恒定的情况下，由于PEM中水分子的重新分布，电池电位对气体流速变化的响应约为10秒。少

Polymer Electrolyte Membrane Fuel Cell (PEFC), which can achieve high energy efficiency and small load on environment, is expected to apply to power sources for electric vehicles and distributed power sources. Because the ionic conductivity and electro-osmosis coefficient of the polymer electrolyte membrane (PEM) are depend on its water uptake and temperature, it is important to control the water uptake and the temperature so that FC can generate electricity uniformly, understanding the temperature distribution and water molecule behavior in PEFC.And it is also important to grasp the transient response of cell potential to load and reactant flow gas change.First, to analyze the steady state characteristics of the power generation, we developed numerical code of PEFC considering the mass, charge and energy balance, and analyzed its characteristics corresponding the experimental condition, such as cell temperature, utilization ratio, etc. Where the activation overpotential was given so a … More s to agree with the measured current-potential characteristics. As the numerical result, it was understood that the current distribution changed due to the water uptake change in PEM, which was controlled by the humidifier temperature. To verify this numerical current distribution change, we actually measured it by use of segmented electrode. The experimental result of current distribution agreed with the analytical.Next, we experimentally and numerically investigated the transient response of cell potential, quickly changing the load current and reactant gas flow rate. In case of constant H_22/O_2 flow rate, the cell potential response to the load current change was describable by the representative time of electric double layer capacitance and reaction resistance. In case of constant simulated reformed gas/air flow rate, the response time was longer because of the larger diffusive resistance. In case of constant load current, the cell potential response to the gas flow rate change was about 10 seconds due to the re-distribution of water molecule in PEM. Less