质子交换膜燃料电池阳极内流动与传质特性模拟

针对直流道质子交换膜燃料电池阳极，建立二维稳态的数学模型研究流道和电极内的流动和传质特性。模型采用通用Darcy定律来描述多孔介质与非多孔介质区域的流体流动，可以模拟沿流动方向上的物质变化情况，并探讨进口速度、进口氢气质量分数和催化层厚度对质量传输的影响。结果表明：增大进口速度、增加进口氢气质量分数、降低催化层厚度有利于氢气的质量传递。     

PEMFC翅脉流道传质及输出性能分析

为研究流道结构对质子交换膜燃料电池（PEMFC）反应气体质量传输及输出性能的影响,建立翅脉流道、叶脉流道及蛇形流道的三维PEMFC几何模型,并对比3种流道的反应气体浓度分布、压力分布及电流密度分布,最后对翅脉流道结构参数进行优化。结果表明,与蛇形流道、叶脉流道相比,翅脉流道能明显改善流道和扩散层内反应气体浓度分布的均匀性,有利于强化反应气体向催化层的质量传递;翅脉流道能减小气体压力分布梯度,使反应气体扩散更加充分;翅脉流道的平均膜电流密度更大,有利于促进电化学反应稳定进行;翅脉流道能改善PEMFC的输出性能,翅脉流道峰值功率密度比蛇形流道、叶脉流道分别提高7.72%和6.25%;减小翅脉流道的直流道长度或圆弧流道圆心角,可提升翅脉流道输出性能。     

温度、压力和湿度对质子交换膜燃料电池性能的影响

以Nafion质子交换膜燃料电池(PEMFC)为对象,通过测量电池的电流—电压、电流—功率和电压—时间曲线,研究了温度、压力和湿度等条件对电池性能的影响,同时也考察了电池的能量转换效率及短期运行时的稳定性,得出了电池较佳的工作条件。实验和计算结果表明：在反应温度为72℃、H2和02压力分别为0．2MPa、进气湿度饱和时,电池最大输出功率可达0．7W．cm^-2;在0．3W.cm^-2～0．7W．cm^-2范围内电池能量转换效率为62％—34％;在大电流密度下电池仍能稳定工作。     

质子交换膜燃料电池自增湿研究进展

概述了质子交换膜燃料电池自增湿研究状况，指出自增湿的出发点是有效利用电池阴极过程生成水。综述了薄电解质膜、新型自增湿膜、自增湿流场结构三种方法的研究进展及适用空间。对自增湿技术发展前景进行了探讨。     

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。     

质子交换膜燃料电池的多尺度传热传质

介绍了目前质子交换膜燃料电池(PEMFC)在膜、电极、单电池、电堆或系统等四个结构尺度上的传热传质过程研究;主要讨论了PEMFC内的多组分传输、膜内水管理和多孔电极内的传热、传质过程;认为建立在孔尺度水平的研究方法是深入探讨电池内多孔材料微结构传热传质的有效途径;多维、多尺度模型的建立及其模拟计算能准确反映PEMFC内部的传递过程机理,为进一步优化电池结构和操作条件提供有价值的参考。     

A numerical study of baffle height and location effects on mass transfer of proton exchange membrane fuel cells with orientated-type flow channels

Reactants and products distribute unevenly in flow channels of proton exchange membrane fuel cells, therefore, the baffle heights and locations in flow channels exhibit effects on species transportation. In this study, a two-dimensional, two-phase, non-isothermal, and steady state model is developed to study the baffle heights and locations effects on mass transportation and performance of the fuel cells with orientated-type channels. Simulation results show that: uniformly distributing baffles in a flow channel can both enhance the reactants transportation and help expel more liquid water, resulting in higher net powers; although using a big baffle at the upstream segment of a channel enhances the performance more, while the water accumulating is also increased more. Reducing the baffle heights accounts for weaker reactants transfer enhancements and worse liquid water expelling; moving the baffles backwardly also causes the decrease in reactant transportation, while the liquid water expelling process is increased.     

Improving two-phase mass transportation under Non-Darcy flow effect in orientated-type flow channels of proton exchange membrane fuel cells

Orientated-type flow channels of proton exchange membrane fuel cells cause non-Darcy effect occurring in flow regions. Therefore, the species transportation is affected by inertial effect. However, how the inertial force affects convection and diffusion of different species has not been discussed before. Thus, a modified two-dimensional, non-isothermal, two-phase and steady state model considering non-Darcy effect is employed in this study, and reactants and products transportations through diffusion and convection under inertial effects are quantitatively analyzed for the first time. Simulation results reveal that the convective transportation of reactants increases more under the influence of inertial force; water vapor transportation through convection increases the water content in porous regions. At the same time, liquid water expels more rapidly from gas diffusion layers under baffle regions, and enlarging baffle volumes increases the regions where the liquid water is rapidly removed under the inertial effect.     

Forchheimer's inertial effect on liquid water removal in proton exchange membrane fuel cells with baffled flow channels

In this study, a two-dimensional, two-phase, non-isothermal and steady-state modified model of proton exchange membrane fuel cells is developed. The Forchheimer's effect (Non-Darcy effect) is coupled in the model, and its impact on liquid water removing process in flow channels with baffles having different shapes is discussed. Simulation results show that the liquid water is able to be removed more at the regions around baffles. At the same time, the baffle shapes reform the liquid water distribution. When using the baffles having larger dimensions (e.g. using rectangular baffles or trapezoidal baffles), the flow spaces around baffles decrease more and the liquid water is removed more because of the increase in local flow velocity. As a result, the concentration polarization is weakened and cell performance is improved more. Moreover, a streamline baffled flow channel that is designed for the purpose of both increasing the cell performance and avoiding excessive increase in pressure drops is discussed. Simulation results show that this flow channel design can both avoid too much increase in pressure drop and facilitate the liquid water removing out from the fuel cell.     

PEMFC系统引射器设计及仿真研究

针对燃料电池汽车的运行特点,对氢气循环引射器进行了结构设计,利用Fluent软件对所设计的引射器进行了全工况模拟,确定了对引射器效率影响较大的变量。通过改变工作流体流量,并经过多次模拟后发现,为了使氢气引射器在怠速工况下不失效,引射器前端工作流体压力p_p要≥1.05 MPa。分析了工作流体质量流量G_p、喷嘴喉部直径d_(p*)和工作流体压力p_p对引射性能的影响,发现G_p对引射器的引射性能影响最大,并给出了G_p的取值范围。研究建议引射器设计时G_p在0.21~0.23 g·s~(-1)范围内最佳。     

基于鹦鹉螺仿生结构的流道对PEMFC性能提升研究

提出一种基于鹦鹉螺旋转结构的仿生流道并建立三维单相、等温的CFD数值模型进行多物理场模拟研究,该流道进气口位于中心位置,反应气体从流场中心进入,向周围环形流道依次流动。将传统蛇形流道与鹦鹉螺仿生流道进行数值模拟分析,发现鹦鹉螺仿生流道具有反应气体分布更加均匀、除水效果更好、浓差极化损失较小、输出性能更好等优势,相比蛇形流道的峰值电流密度提升46.77%、峰值功率密度提升21.53%。     

车用质子交换膜燃料电池发动机系统控制技术现状研究

质子交换膜燃料电池(PEMFC)以其高能量密度、工作温度低、无污染排放、结构紧凑等优点被公认为发展前景最好的汽车动力源之一,对车用(PEMFC)发动机系统的氢气/空气供给系统、水/热管理系统、安全系统、压力,温湿度控制系统的技术现状进行了系统分析,对PEMFC发动机的控制理论,如模糊控制、预测控制与应用技术发展方向进行了研究。     

An inverse geometry design problem in optimizing the shape of the gas channel for a proton exchange membrane fuel cell

The inverse design problem technique presented in this paper is intended for optimizing the shape of the gas channel at the cathode side in a proton exchange membrane fuel cell (PEMFC). The technique uses the desired current densities located on a carbon plate near the outlet of the channel at the cathode side as a starting point. The desired current density distributions can be obtained by modifying the current density distributions of the existing PEMFC with rectangular gas channels. The geometry of the redesigned gas channel is generated using a B-spline curve method, which enables the shape of the fuel channel to be completely specified using only a small number of control points, thus applying the technique of parameter estimation for the inverse design problem. Results show that by utilizing the redesigned optimal gas channel, the total current of the PEMFC can be increased, and at the same time the phenomenon of saturated water accumulation in the channel can be greatly reduced.     

千瓦级质子交换膜燃料电池电堆的实验研究

空泡率是汽液两相流动的基本参数之一,而已有过冷沸腾空泡率计算方法研究以高质量流速为主。且大量文献报道现有空泡率模型难以适用于低流速过冷沸腾工况。该文基于低流速过冷沸腾净蒸汽产生点(NVG)理论模型,进一步建立了计算过冷沸腾空泡率的分布拟合模型。在较宽广的压力、质量流速、热流密度和流道尺寸范围内将模型计算结果与现有空泡率实验数据进行了比较,低流速工况下该模型与实验数据符合良好,表明该模型可适用于低流速过冷沸腾工况。