阴极挡板排列对PEMFC反应物输运和性能的影响

为了改善质子交换膜燃料电池(PEMFC)的性能,采用流道内使用挡板堵塞的方法,以增强反应气体向催化层的传质。建立了一个三维、两相、稳态的PEMFC数值模型,研究了凸字排布、顺排和逆排这3种不同阴极流道挡板的排布方式对PEMFC性能的影响,并与无挡板常规流场进行对比,然后在最佳排布方式的基础上研究了挡板形状(矩形、梯形和半圆形)对PEMFC性能的影响。结果表明：PEMFC阴极流道挡板顺排性能最好,相较于无挡板常规流道,净功率提升了14.3%;使用梯形挡板的PEMFC性能最好,相较于无挡板常规流道,净功率提高了16.4%。     

钙离子对质子交换膜燃料电池性能衰减机理研究

采用试验方法,通过向质子交换膜燃料电池(PEMFC)的电极(阳极和阴极)注入2种浓度(200和500 mg/L)的Ca~(2+)溶液,研究Ca~(2+)对PEMFC电化学性能的影响;通过扫描电镜(SEM),能量散射谱仪(EDS)和电子探针(EPMA)对经Ca~(2+)污染20 h后的电池性能的衰减机理进行研究。实验结果表明,经200和500 mg/L Ca~(2+)污染PEMFC阳极20 h后,电池的电化学性能衰减明显,随着Ca~(2+)浓度的增加,电池电化学性能衰减程度增大;SEM和EDS实验结果表明,经500 mg/L Ca~(2+)污染PEMFC阳极20 h后,阴、阳两极的气体扩散层分别与阴、阳两极的催化层剥离,在质子交换膜、阳极催化层、阳极气体扩散层以及阴极气体扩散层均发现Ca元素,在质子交换膜上Ca元素含量高于其他部件上;EPMA实验结果表明,Ca~(2+)污染PEMFC阳极后,Ca元素主要存在于质子交换膜上;研究结果表明,PEMFC电化学性能衰减的机理主要是由于Ca~(2+)与质子交换膜中的质子发生离子交换反应并取代质子交换膜中的磺酸根基团上的质子形成新的磺酸盐结构所致。     

考虑环境温湿度的空冷PEMFC最佳工作温度研究与控制

空冷型质子交换膜燃料电池(PEMFC)属于阴极开放式燃料电池,无外部增湿装置,因此空冷型PEMFC阴极入口处空气的温度和湿度必然对燃料电池工作性能有着不可忽视的影响。通过实验研究空冷型PEMFC最佳工作温度与环境温湿度及输出电流之间的关系,分析不同环境温湿度和输出电流对空冷型PEMFC最佳工作温度的影响。最后设计空冷型PEMFC控制系统,根据得到的不同环境温湿度下的空冷型PEMFC最佳工作温度曲线,采用PID控制方法实现不同温湿度环境条件下的最佳工作温度控制。     

不同流道质子交换膜燃料电池内传质过程的数值模拟

对采用交指型流场的质子交换膜燃料电池阴极建立了二维数学模型,利用计算流体力学的方法,模拟和研究了质子交换膜燃料电池阴极内的流动和传质过程.分别探讨了采用交指型流场和平行流场时气体在阴极扩散层中的传递机制及各组分浓度分布的特性,为燃料电池流场的设计与分析提供了参考依据.     

具有泡沫金属流场的燃料电池研究进展

泡沫金属是一种具有高孔隙率、高电导率、良好传热性和重量较轻等优点的新型多功能材料,在质子交换膜燃料电池（PEMFC）中嵌入泡沫金属作为流场的应用受到越来越多的关注。重点综述PEMFC流场的研究进展,探讨泡沫金属结构参数、流场设计和环境因素等对功率密度、气体分布、压降和水热管理等性能的影响。进一步讨论泡沫金属流场在PEMFC应用中所面临的腐蚀和水淹问题,以及具备耐腐蚀涂层泡沫金属的研究进展,为PEMFC泡沫金属流场的发展和优化提供有益的启示,以期推进泡沫金属在PEMFC中的应用。     

四流道蛇形结构质子交换膜燃料电池温度分布数值模拟

为研究温度对质子交换膜燃料电池性能的影响,运用多物理场直接耦合分析软件COMSOL Multiphysics,对不同电池温度的四流道蛇形流场质子交换膜燃料电池进行了数值模拟。模拟得到了不同电池温度下垂直膜电极平面以及电池中心处从阳极流道到膜,再到到阴极流道的温度变化情况;还得到了电池温度为353K时,电池入口处、中心处和出口处从阳极流道到阴极流道相应位置点的温差变化。对模拟结果进行分析和比较后发现:电池内部温度的升高与电池本身的原始温度存在线性变化关系;电池入口处、中心处和出口处的温度变化趋势存在差异,且电池入口处温升最大,中心处次之,出口处温升最小;随着电池温度的升高,电池因内部反应所产生的热量减少。模拟结果对质子交换膜燃料电池的性能优化有重要意义。     

PEMFC温度的自动控制

本文分析了工作温度对质子交换膜燃料电池(PEMFC)运行性能的影响,研究采用Nafion膜作为温度传感器来检测质子交换膜燃料电池的工作温度,运用闭环负反馈调节方案实现了质子交换膜燃料电池温度的自动控制,并对温度调节过渡过程的性能指标进行了分析和验证。     

不同流场结构对PEMFC性能影响的模拟研究

该文模拟常规矩形平行流场、正六边形平行流场和正六边形蜂窝状仿生学流场对质子交换膜燃料电池（PEMFC）性能的影响。通过对极化曲线、氧气和水分布、膜电流密度以及压降和寄生功率密度进行分析，结果表明：正六边形流场表现出良好的输出性能，且正六边形蜂窝状流场的电流密度比常规矩形平行流场和正六边形平行流场分别提升11.28%和4.95%。此外，常规矩形平行流场、正六边形平行流场和正六边形蜂窝状流场的氧气不均匀度分别为0.64、0.53和0.41，正六边形蜂窝状流场展现出更好的水和膜电流密度分布能力，进一步说明正六边形流场缓解了氧气、水和膜电流密度分布不均匀的问题。正六边形蜂窝状流场压降虽比常规矩形平行流场和正六边形平行流场分别增加40.0%和27.7%，有较高的寄生功率密度，但仍获得了最大的净输出功率密度。     

质子交换膜燃料电池内部传热传质三维模拟

针对常规流场质子交换膜燃料电池提出了三维非等温数学模型。模型考虑了电化学反应动力学以及反应气体在流道和多孔介质内的流动和传递过程,详细研究了水在质子膜内的电渗和扩散作用。计算结果表明,反应气体传质的限制和质子膜内的水含量直接决定了电极局部电流密度的分布和电池输出性能;在电流密度大于0.3~0.4A/cm2时开始出现水从阳极到阴极侧的净迁移;高电流密度时膜厚度方向存在很大的温度梯度,这对膜内传递过程有较大影响。     

基于BP神经网络的燃料电池电特性建模

采用基于改进粒子群算法的BP神经网（Improved—PSOBPNN）,建立质子交换膜燃料电池（PEMFC）电特性模型。PEMFC系统仿真结果表明该方法简单、有效、精度高,与采用传统BP神经网络的模型相比具有明显的优越性,为PEMFC系统建模,电池性能优化以及控制系统设计提供了新的思路。     

Three dimensional,two phase flow mathematical model for PEM fuel cell: Part II. Analysis and discussion of the internal transport mechanisms

The internal transport mechanisms, which were acquired from the modeling results in Part I of this series, are discussed and compared for PEM fuel cells with a conventional flow field and an interdigitated flow field. The modeling results show that the oxygen concentration fraction in an interdigitated flow field is higher than that in a conventional flow field to increase the reaction rate, and the liquid water saturation in the former flow field is much less than that in the latter one at the cathode side to reduce the concentration overpotential largely. However, if the cathode inlet air in a PEM fuel cell with interdigitated flow field is not humidified, the performance of this fuel cell is inferior to that of a PEM fuel cell with conventional flow field because of a larger ohmic overpotential. As a result, the humidification is important for an interdigitated flow field to acquire a much better performance than a conventional flow field.     

Effects of operating conditions on cell performance of PEM fuel cells with conventional or interdigitated flow field

In this work, the influences of various operating conditions including cathode inlet gas flow rate, cathode inlet humidification temperature, cell temperature, etc. on the performance of proton exchange membrane (PEM) fuel cells with conventional flow field and interdigitated flow field are experimentally studied. Experimental results show that the cell performance is enhanced with increases in cathode inlet gas flow rate, cathode humidification temperature and cell temperature. However, as cell temperature is higher than or equal to anode humidification temperature, the cell performance is deteriorated due to failure in humidification of the cell. Comparison between interdigitated flow field and conventional flow field shows that the former provides higher cell performance and remarkably reduces fuel consumption for efficient diffusion of the fuel gas to the diffuser layer. As air is used as the cathode inlet gas, PEM fuel cell with interdigitated flow field can obtain preferable limiting current density, and the optimal power is about 1.4 times as that of the cells with conventional flow field. Rib and shoulder areas are more advantageous to electrochemical reaction in interdigitated flow field; hence a large flow field area ratio degrades the better performance area and thus the cell performance. But too small flow field area ratio also deteriorates the cell performance due to the decrease in effective reaction area. Theoretically, the flow field area has an optimum value, i.e., 50.75% in this work, providing higher performance than 66.67%.     

质子交换膜燃料电池阴极传质过程的数值模拟

利用CFD方法对采用交指型流道质子交换膜燃料电池阴极的传质过程进行数值模拟,得到了阴极扩散层内氧气和水蒸汽质量浓度的分布特性,探讨了电池结构参数和操作条件对电池性能的影响。     

Experimental study on the performance of PEM fuel cells with interdigitated flow channels

In this work, the effects of interdigitated flow channel design on the cell performance of proton exchange membrane fuel cells (PEMFCs) are investigated experimentally. To compare the effectiveness of the interdigitated flow field, the performance of the PEM fuel cells with traditional flow channel design is also tested. Besides, the effects of the flow area ratio and the baffle-blocked position of the interdigitated flow field are examined in details. The experimental results indicate that the cell performance can be enhanced with an increase in the inlet flow rate and cathode humidification temperature. Either with oxygen or air as the cathode fuel, the cells with interdigitated flow fields have better performance than conventional ones. With air as the cathode fuel, the measurements show that the interdigitated flow field results in a larger limiting current density, and the power output is about 1.4 times that with the conventional flow field. The results also show that the cell performance of the interdigitated flow field with flow area ratio of 40.23% or 50.75% is better than that with 66.75%.     

Mid-baffle interdigitated flow fields for proton exchange membrane fuel cells

A new design of an interdigitated flow field, called as a mid-baffle interdigitated flow field, was built and tested for its effect on the performance of proton exchange membrane (PEM) fuel cells. The results were compared to the conventional interdigitated flow field. Their performances at different oxidant gas flow rates and operating pressures were also examined and compared by using both O₂ and air as the cathode fuel reactants. The experimental results showed that when air was used as the cathode reactant, the cell with the mid-baffle interdigitated flow field outperformed the conventional one, giving a power output approximately 1.2-1.3 times higher depending on the air flow rates. The polarization curves of the mid-baffle interdigitated flow field showed larger limiting current densities at every air flow rate tested in this work. However, the performances of both flow fields were almost the same when the cathode reactant gas was O₂. The test also demonstrated that the flow field performance could be enhanced by increasing the oxidant gas flow rate and cell operating pressure.     

Assisted water management in a PEMFC with a modified flow field and its effect on performance

This work designed and tested innovative flow channels in order to improve water management in a polymer electrolyte membrane fuel cell (PEMFC). The design employed slanted channels with an angle of 20° in a flow plate to collect the liquid water that permeated from the gas diffusion layers. The effects of orientations of the slanted channels in up-slanted and down-slanted directions and relative humidity levels on the cell performance were investigated. The experimental results showed that modifying the anode flow field using down-slanted channels provided higher cell performance. Water concentration at the gas diffusion layer is reduced resulting in more back diffusion of water from the cathode to anode, thus inducing membrane hydration and improving the conductivity. Promotion of water removal by applying down-slanted channels in the cathode side did not improve the performance. This work has demonstrated that channel cross-section design alone could improve the PEM fuel cell performance. The anode down-slanted cell indeed improved the performances at extremely wet condition and the power was equally good as that without modified flow channel at less wet condition.     

Influences of gas relative humidity on the temperature of membrane in PEMFC with interdigitated flow field

A fundamental understanding of the water balance of a fuel cell during operation is crucial for improving the cell performance and durability. The humidification in the anode or cathode has an important effect on the flow characteristics and cell efficiency. Three-dimensional steady mathematical model based on the electrochemical, current distribution, fluid motion continuity equation, momentum and energy equation, boundary layer theory has been developed to simulate PEMFC with interdigitated flow field using the computational fluid dynamics (CFD). Effects on the current density and temperature differences have been simulated and analyzed respectively, when the humidification in the anode or cathode is from 0% to 100% respectively. The numerical results show that the humidification strongly influences the current density and temperature difference so as to affect the cell efficiency. Under the same operation conditions and low humidification conditions, anode humidification can better enhance the performance of the battery and improve the extent of PEM humidification.     

Design,manufacturing, assembling and testing of a transparent PEM fuel cell for investigation of water management and contact resistance at dead-end mode

PEM fuel cell can operate at two different modes. At first mode the outlet of gas flow field is open and at the second mode the outlet of flow field is closed. The second mode is known as dead-end PEMFC. Proton exchange membrane fuel cells (PEMFCs) with dead-ended anode and cathode can obtain high hydrogen and oxygen utilization by a comparatively simple system. Nevertheless, the accumulation of the water in anode and cathode channels can lead to a local fuel starvation degrading the performance and durability of PEMFCs. There are different methods for investigation of water management such as: neutron radiography, gas chromatography, capturing by use of X-ray and capturing by use of infrared ray. Due to high cost and many hazards these methods at most cases cannot be used. According to the above mentioned problem we recommend a transparent PEMFC as a simplest, cheapest and the most suitable method for investigation of water management. Designing and manufacturing this type of PEMFC require special techniques. In this paper at first an optimal flow field is numerically designed and according to numerical results a transparent PEMFC is designed, manufactured and tested. Furthermore the performance of PEMFC at dead-end mode and open-end mode is studied. The applied design with a higher efficiency could have a same polarization curve as open-end mode. The results showed that by setting the purge interval time on 5 s and then opening purge valve for 1 s, there isn't any degradation on PEMFC performance but for purge interval of 10 s gradual performance degradation is recorded.     

In situ comparison of water content and dynamics in parallel, single-serpentine, and interdigitated flow fields of polymer electrolyte membrane fuel cells

Water content and dynamics were characterized and compared in situ by simultaneous neutron and optical imaging for three PEM fuel cell flow fields: parallel, serpentine, and interdigitated. Two independent sets of images were obtained simultaneously: liquid water dynamics in the flow field (channels and manifolds) were recorded by a digital camera through an optical window, while the through-thickness integrated water content was measured across the cell area by neutron imaging. Complementary data from the concurrent images allowed distinguishing between the water dynamics on the cathode and the anode side. The transient water content within the cell measured using neutron imaging is correlated with optical data as well as with temporal variations in the cell output and pressure differentials across the flow fields. Water dynamics on both the cathode and anode side were visualized and discussed.The serpentine cell showed stable output across the current range and the highest limiting current. Parallel and interdigitated cells exhibited substantially higher water contents and lower pressure differentials than the serpentine. Anode flooding significantly impeded their performance at high current. At moderate current, cell output correlated with the changes in water distribution in the cathode flow field rather than with the variations in the overall water content. Performance of the interdigitated cell was similar to the serpentine one in spite of the vastly different water contents.The cell's water-content response to a step-change in current revealed three distinct stages of water accumulation. Flow field configuration greatly affected both the amount of water accumulated in the cell and the duration of each stage.