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1.
    
In proton exchange membrane fuel cells, baffled flow channels can enhance the reactant transfer and improve the cell performance. Many different baffled flow channels have been numerically studied in previous published papers. However, what kind of baffled flow channels can improve the cell performance most is still unknown. In this simulation work, a two‐dimensional, two‐phase, nonisothermal, and steady‐state model of proton exchange membrane fuel cells is developed. The mass transfer and cell performance of PEMFCs with different baffled flow channels have been numerically compared. Simulation results show that the rectangular baffle can enhance the reactant transfer most and improve the cell performance most; however, the power loss in rectangular baffled flow channel is also the highest. To inherit the advantages and overcome the shortages of the rectangular baffled flow channel, an optimized baffled flow channel is developed. In this newly developed baffled flow channel, the windward side is designed as the streamline shape and the leeward side is designed as the sloped shape. Results of the simulation also show that the optimized baffled flow channel can reduce the power loss accounted by the pumping power in reactant delivering process and the cell performance can be further improved.  相似文献   

2.
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。  相似文献   

3.
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。  相似文献   

4.
温度、压力和湿度对质子交换膜燃料电池性能的影响   总被引:16,自引:0,他引:16  
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。  相似文献   

5.
质子交换膜燃料电池自增湿研究进展   总被引:3,自引:0,他引:3  
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。  相似文献   

6.
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。  相似文献   

7.
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。  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
    
Installing blocks in cathode flow field can effectively enhance the transfer of oxygen from channel to the reaction sites of catalyst layer, thus boosting the performance of the fuel cell. In this work, an optimization methodology combined with genetic algorithm and three-dimensional fuel cell modeling is developed to optimize the design of partially blocked channel for a proton exchange membrane fuel cell (PEMFC) with parallel flow field. In the optimization, the heights of the blocks are assumed to be linearly increased and two parameters (i.e., height of the first block and the height increase between adjacent blocks) are considered. The impact of the optimized design of the blocked channel on cell performance is analyzed, and the effects of the optimized blocked channel designs with increasing-height and uniform-height block height distributions were also compared in detail. With this optimization methodology, the optimal height distribution of the blocks in the channel can be obtained for various block numbers. With varying the block numbers, the cell voltage and net cell power are firstly improved until the maximal values reached and then lowered. The maximal net cell power is reached for the block number of 16. As compared with the flow channel without adding blocks, the net power of the PEMFC can be enhanced by about 10.9%. For pressure drop behavior, with the optimized block height distribution, the total pressure drop in cathode flow field can be maintained in similar level with varying block numbers from 4 to 20. Considering both the net power and pressure drop, the optimized blocked channels with adding 8 to 16 blocks are recommended in this study. Besides, it is indicated that the performance of the optimized block design with increasing-height is higher than that of the optimized block design with uniform-height.  相似文献   

11.
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.  相似文献   

12.
    
Orientated-type flow channels having porous blocks enhance the reactant transfer into gas diffusion layers of proton exchange membrane fuel cells. However, because of the blockages accounted by baffles and porous blocks in channel regions, pumping power increases. In this study, with the aim of further reducing the pumping power in flow channels with porous-blocked baffles, an orientated-type flow channel with streamline baffles having porous blocks is proposed. By employing an improved two-fluid model, cell performance, liquid water distribution and pumping power in a single flow channel are numerically studied. The simulation results show that the baffles with porous blocks increase the cell performance, and the streamline baffles with larger volumes further increase the performance; the produced water in porous regions is ejected more under inertial effect, especially at the regions near to baffles in gas diffusion layers and inside porous blocks. In addition, by using the streamline baffles, the excessive increase in power loss is further reduced. Moreover, the location and porosity effects of baffles with porous blocks are analyzed. Simulation results show that the location exhibits obscure effects on reactant transfer and cell performance, while the liquid water can be removed more when the porous blocked baffles are concentrated at downstream. The net power is enhanced more when using three porous blocks with the porosity of 0.00.  相似文献   

13.
    
Proton exchange membrane fuel cell (PEMFC) performance degrades when carbon monoxide (CO) is present in the fuel gas; this is referred to as CO poisoning. This paper investigates CO poisoning of PEMFCs by reviewing work on the electrochemistry of CO and hydrogen, the experimental performance of PEMFCs exhibiting CO poisoning, methods to mitigate CO poisoning and theoretical models of CO poisoning. It is found that CO poisons the anode reaction through preferentially adsorbing to the platinum surface and blocking active sites, and that the CO poisoning effect is slow and reversible. There exist three methods to mitigate the effect of CO poisoning: (i) the use of a platinum alloy catalyst, (ii) higher cell operating temperature and (iii) introduction of oxygen into the fuel gas flow. Of these three methods, the third is the most practical. There are several models available in the literature for the effect of CO poisoning on a PEMFC and from the modeling efforts, it is clear that small CO oxidation rates can result in much increased performance of the anode. However, none of the existing models have considered the effect of transport phenomena in a cell, nor the effect of oxygen crossover from the cathode, which may be a significant contributor to CO tolerance in a PEMFC. In addition, there is a lack of data for CO oxidation and adsorption at low temperatures, which is needed for detailed modeling of CO poisoning in PEMFCs. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

14.
PEMFC系统引射器设计及仿真研究   总被引:1,自引:0,他引:1  
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。  相似文献   

15.
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%。  相似文献   

16.
车用质子交换膜燃料电池发动机系统控制技术现状研究   总被引:5,自引:0,他引:5  
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。  相似文献   

17.
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.  相似文献   

18.
    
With the occurrence of reversible electrochemical reactions, mode switching considerably affects the electric performance of unitized regenerative fuel cells (URFCs) owing to the complicated mass and heat transfer. Although limited researches have been done, no such studies on mass and heat transfer through a three‐dimensional view are envisioned during mode switching. A three‐dimensional full‐cell model was developed and validated to study the dynamic characteristics of a proton exchange membrane‐based URFC during mode switching. Mode switching was performed by changing operation voltage from 0.60 to 1.65 V. Results showed that species and heat transfer affect the electric performance of the cell during mode switching, especially through the third dimensional. Local water starvation occurs on oxygen side catalyst layer and thus results in slight reduction on current density and hydrogen generation. Restricted to heat transfer capacity through ribs, heat transfer process adds total response time in URFCs. Heat flux and surface heat transfer coefficient are forecasted on the hydrogen and oxygen sides. A total time of 4 seconds is essential for URFC reaching a new relative balanced state.  相似文献   

19.
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。  相似文献   

20.
质子交换膜燃料电池(PEMFC)引射器设计通常需经过结构参数计算、计算域建模、网格划分和数值模拟等步骤,并经过多轮迭代得到一个性能较优的设计方案,所需时间成本较高。针对PEMFC引射器,通过Python编程语言将以上功能进行集成,自动计算引射器结构参数,并调用OpenFOAM软件中的blockMesh工具进行计算域建模、网格划分,以及rhoSimpleFoam求解器进行数值仿真验证,形成一套参数化的自动仿真设计工具。研究表明,该工具可显著提高PEMFC引射器设计开发的速度,从而促进汽车工业的发展。  相似文献   

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