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首页> 外文会议>11th fuel cell science, engineering, and technology conference 2013 >EFFECT OF GRAVITY ON DROPLET GROWTH AND DETACHMENT INSIDE A SIMULATED PEM FUEL CELL AIR FLOW CHANNEL WITH HYDROPHOBIC WALLS
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EFFECT OF GRAVITY ON DROPLET GROWTH AND DETACHMENT INSIDE A SIMULATED PEM FUEL CELL AIR FLOW CHANNEL WITH HYDROPHOBIC WALLS

机译：重力对带有疏水壁的模拟PEM燃料电池气流通道内的液滴生长和分离的影响

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摘要

Water management still remains a challenge for proton exchange membrane fuel cells. Byproduct water formed in the cathode side of the membrane is wicked to the air supply channel through the gas diffusion layer. Water emerges into the air supply channel as droplets, which are then removed by the air stream. When the rate of water production is higher than the rate of water removal, droplets start to accumulate and coalesce with each other forming slugs consequently clogging the channels and causing poor fuel cell performance. It has been shown in previous experiments that rendering the channels hydrophobic or super-hydrophobic cause water droplets to be removed faster, not allowing time to coalesce, and therefore making channels less prone to flooding. In this numerical study we analyze water droplet growth and detachment from a simulated hydrophobic air supply channel inside a proton exchange membrane (PEM) fuel cell. In these numerical simulations the Navier-Stokes equations are solved using the SIMPLER method coupled with the level set technique in order to track the liquid-vapor interface. The effect of the gravity field acting in the -y, -x, and +x directions was examined for an array of water flow rates and air flow rates. Detachment times and diameters were computed. The results showed no significant effect of the gravity field acting in the three different directions as expected since the Bond and Capillary numbers are relatively small. The maximum variations in detachment time and diameter were found to be 8.8 and 4.2 percent, respectively, between the horizontal channel and the vertical channel with gravity acting in the negative x direction, against the air flow. Droplet detachment was more significantly affected by the air and water flow rates.
机译：对于质子交换膜燃料电池，水管理仍然是一个挑战。在膜的阴极侧形成的副产物水通过气体扩散层被芯吸到空气供应通道。水以小滴的形式出现在空气供应通道中，然后被气流清除。当产水率高于除水率时，液滴开始聚集并彼此聚结，形成团块，从而堵塞通道并导致不良的燃料电池性能。在先前的实验中已经表明，使通道疏水或超疏水导致水滴被更快地去除，不允许时间聚结，因此使得通道更不容易泛洪。在此数值研究中，我们分析了质子交换膜（PEM）燃料电池内部模拟疏水空气供应通道中的水滴生长和脱离。在这些数值模拟中，使用SIMPLER方法结合水平集技术来求解Navier-Stokes方程，以便跟踪液-气界面。对于一系列水流量和空气流量，检查了重力场在-y，-x和+ x方向上的作用。计算分离时间和直径。结果表明，由于键数和毛细管数相对较小，重力场在三个不同方向上的作用均无明显影响。发现水平通道和垂直通道之间的分离时间和直径的最大变化分别为8.8％和4.2％，其中重力沿负x方向作用于气流。空气和水的流速对液滴分离的影响更大。

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