不同流场下进气对质子交换膜燃料电池性能的影响

流场的结构对于质子交换膜燃料电池(PEMFC)的水管理和气体的传递具有十分重要的影响,相关研究一直是燃料电池的研究热点与重点。本文以纯氧气和空气作为阴极氧化剂,通过电池的性能测试、极化曲线和电化学阻抗分析等原位实验,分析了气体的流动与传输、不同流场下的电流密度、入口反应气体浓度等条件对电池性能的影响。实验结果表明,提高氧气浓度可以获得更好的质子交换膜燃料电池性能和最小化活化损失,纯氧气、波状流场的使用效果随进气量的变化而有明显的变化。     

流道结构和几何尺寸对燃料电池性能影响的实验研究

流场板是质子交换膜燃料电池重要部件之一。本文对以氢气和氧气作为反应气体的质子交换膜电池的极化曲线进行了实验测定,研究了不同流场板结构、流场板深度和宽度对电池性能的影响．研究发现采用组合流道的电池性能最佳．     

Fabrication of porous metal fiber sintered sheet as a flow field for proton exchange membrane fuel cell

To improve the diffusion performance of reactive gas, a porous copper fiber sintered sheet (PCFSS) was fabricated and used as the flow field for proton exchange membrane fuel cell (PEMFC). The pressure and flow velocity distribution of the reaction gas in the PCFSS was firstly compared with the serpentine flow field by using the Fluent simulation software. Our results showed that the superiority of PCFSS in the uniformity of gas diffusion was observed. The total resistance of PEMFC with PCFSS in different porosities was obtained. And the advantages of PCFSS in electronic transmission were found by comparing with the serpentine flow field. Besides, the influences of different operating conditions and different porosities of porous flow fields on the performance of PEMFC were experimentally investigated. With the cell temperature of 70 °C as well as the humidification temperature of 60 °C, a PEMFC with PCFSS of 70% porosity exhibited better performance.     

不同进气湿度PEMFC动态响应分析

质子交换膜燃料电池(PEMFC)工作参数的影响最终要体现在对电池内传质过程的影响上。实验得到了在不同进气加湿程度下电池性能在启动工况中的变化,基于非稳态数学模型计算了不同阴极入口湿度下电池在负载渐变工况下膜内含水量和电流密度的瞬态响应,并与相应的实验工况进行了对比。     

EXPERIMENTAL INVESTIGATION OF THE PERFORMANCE OF A SINGLE PROTON EXCHANGE MEMBRANE FUEL CELL USING DRY FUEL

Recently, the requirements for cellular phones, portable computers, and digital cameras have increased dramatically. A portable electric power supply with long duration and high performance is needed for these products. A proton exchange membrane fuel cell (PEMFC) can meet these requirements and becomes one of the best candidates for a portable power source. It is impossible to install an extra humidifier into small-scale portable electric products for PEMFC water management. This article presents a series of experiments to investigate the performance of a single PEMFC. The effects of different operating conditions on cell performance, including the temperature, pressure, and inlet fuel/oxidant flow rate, are discussed. The test results confirm the positive effect of these parameters on cell performance and power output. The interaction effect of temperature--flow rate is related to the cell humidity, and is important for cell performance. The dry-out problem for a PEMFC is also significantly revealed in the experiments for higher cell temperature and flow rate. Current experimental results can provide useful information for investigating the cell performance and its operating effects under dry fuel/oxidant flow conditions and as a benchmark for simulation work in future studies.     

质子交换膜燃料电池低化学计量比的性能研究

以质子交换膜燃料电池实际应用为背景,研究了在反应物低化学计量比下,质子交换膜燃料电池不同温度、压力下的性能。得到了电池温度,压力对反应物化学计量比的影响。实验结果表明,反应物化学计量比1.0的电池性能低于足量反应气体工况下的电池性能;化学计量比为1.3时,电池能够在预期电流强度下稳定运行;反应气体的传质过程影响反应所需的化学计量比;当提升压力至0.13 MPa,化学计量比1.0的电池性能与足量反应气体工况下的性能相当。     

Electrostatic spraying of membrane electrode for proton exchange membrane fuel cell

In order to improve the performance of proton exchange membrane fuel cell (PEMFC), the optimization of electrostatic spraying of membrane electrode was conducted. The influence of the spraying voltage on morphology, elemental composition of catalyst layer, and performance of the PEMFC were investigated. The results show that increasing spraying voltage could reduce agglomeration of the carbon-supported platinum particles, leading to more uniform pore distribution. High voltage did not accelerate oxidation of platinum catalyst. A high electrochemical active surface area of 26.18 m²/g_pt was obtained when the platinum-carbon catalyst layer was deposited in cone jet mode. With further increasing spraying voltage, the total ohmic resistance and catalytic activity were changed slightly, whereas the charge transfer resistance was increased. Using the optimized electrostatic spraying parameters (injection rate = 100 μL min⁻¹, spraying voltage = 8.5 kV, and working distance = 12 mm), a peak power density of 1.408 W cm⁻² was obtained with an output voltage of 0.451 V.     

Effect of gas diffusion layer and membrane properties in an annular proton exchange membrane fuel cell

A complete three-dimensional and single phase computational dynamics model for annular proton exchange membrane (PEM) fuel cell is used to investigate the effect of changing gas diffusion layer and membrane properties on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the two-dimensional mass, momentum and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC that cannot be investigated experimentally. The results show that by increasing the thickness and decreasing the porosity of GDL the performance of the cell enhances that it is different with planner PEM fuel cell. Also the results show that by decreasing the thickness of the membrane the performance of the cell increases.     

PEMFCs的膜及阴极催化层数值模拟

本文提出了一个质子交换膜燃料电池的膜和阴极催化层的一维非稳态数学模型,模型考虑了电化学反应及反应中的传质过程。本文结合算例分析了燃料电池膜及阴极催化层的性能,结果能验证燃料电池内阻理论。论文结果表明:(1)随着输出电流密度的增大,氧浓度分布不均匀性增大; (2)阴极催化层厚度减小,可提高电池输出电压; (3)电池进口处氧气摩尔浓度增大,可增加电池的输出电压。     

Breakthrough/drainage pressures and X-ray water visualization in gas diffusion layer of PEMFC

The primary role of the gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFC) is to maintain the delicate balance between water retention and removal in GDLs. Water management in the fuel cell is related to the breakthrough pressure at which water starts to pass through GDL, and the drainage pressure, which is maintained after the breakthrough. These pressures are both related to water management in fuel cells. Here we measured these pressures for two different GDLs and used X-ray tomography to visualize the water distributions within them. We then relate the variations in liquid pressures to the visualization and discuss water management in PEMFC.