Dynamic behaviour of liquid water emerging from a GDL pore into a PEMFC gas flow channel
Dynamic behaviour of liquid water emerging from a GDL pore into a PEMFC gas flow channel
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DOI：
10.1016/j.jpowsour.2007.07.024
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发表时间：
2007-10
影响因子：
9.2
通讯作者：
Xun Zhu;P. Sui;N. Djilali
中科院分区：
文献类型：
--
作者：
Xun Zhu;P. Sui;N. Djilali
对液态水通过GDL孔进入聚合物电解质膜燃料电池（PEMFC）通道的动力学行为进行了数值研究。采用流体体积（VOF）方法进行二维瞬态模拟，以明确跟踪液-气界面，并获得对水滴在气体通道中的大部分气流的动力学的理解。模拟区域由一个直通道组成，空气从一侧流动，水从通道底壁的孔隙进入该区域。通道尺寸、流动条件和表面性质被选择为代表PEMFC中的典型条件。一系列的参数研究，包括通道的大小，孔径的影响，和液滴的聚结进行了特别关注的几何结构的效果。模拟结果和流型随时间的演化分析表明，通道高度和孔隙宽度对水滴的变形和脱落有显著影响。对从两个具有相同尺寸的孔进入通道的液滴进行的模拟表明，两个水滴的聚结可以加速微通道中的液滴的变形速率和运动。考虑到液滴与孔的初始连接，发现产生用于液滴脱离的临界空气入口速度，这与先前的研究显著不同，先前的研究认为最初停滞的液滴位于表面上。预测的临界空气速度被发现是敏感的孔的几何形状，与更高的值时得到的曲率与GDL纤维被考虑在内。临界速度也被发现，随着液滴尺寸的增加和GDL孔径的减小而减小。
A numerical investigation of the dynamic behaviour of liquid water entering a polymer electrolyte membrane fuel cell (PEMFC) channel through a GDL pore is reported. Two-dimensional, transient simulations employing the volume of fluid (VOF) method are performed to explicitly track the liquid–gas interface, and to gain understanding into the dynamics of a water droplet subjected to air flow in the bulk of the gas channel. The modeled domain consists of a straight channel with air flowing from one side and water entering the domain from a pore at the bottom wall of the channel. The channel dimensions, flow conditions and surface properties are chosen to be representative of typical conditions in a PEMFC. A series of parametric studies, including the effects of channel size, pore size, and the coalescence of droplets are performed with a particular focus on the effect of geometrical structure. The simulation results and analysis of the time evolution of flow patterns show that the height of the channel as well as the width of the pore have significant impacts on the deformation and detachment of the water droplet. Simulations performed for droplets emerging from two pores with the same size into the channel show that coalescence of two water droplets can accelerate the deformation rate and motion of the droplets in the microchannel. Accounting for the initial connection of a droplet to a pore was found to yield critical air inlet velocities for droplet detachment that are significantly different from previous studies that considered an initially stagnant droplet sitting on the surface. The predicted critical air velocity is found to be sensitive to the geometry of the pore, with higher values obtained when the curvature associated with the GDL fibres is taken into account. The critical velocity is also found to decrease with increasing droplet size and decreasing GDL pore diameter.