H_2/空气质子交换膜燃料电池气体扩散层表面水滴行为的VOF模拟研究

Dynamic Behaviors of Water Droplets on H_2/Air PEMFC Gas Diffusion Layer Surface: VOF Simulations

在研发和设计H_2/空气质子交换膜燃料电池时,如何促进扩散介质及气流通道内液态水的传输是需要考虑的主要问题之一。本文运用FLUENT软件流体体积(VOF)模块模拟了燃料电池气体扩散层表面液滴的形成、脱落及输运行为。液滴受气体剪切力、粘滞力和表面张力的共同影响,对不同的壁面浸润角和不同的气体剪切力,呈现出复杂的液滴动力学行为。考察了通道气体流速和扩散层表面浸润力对液滴行为的影响。结果表明,增大扩散层表面浸润角或入口气流速度均可以促进扩散层表面液滴的跃离,前者对液滴跃离的促进作用更大;扩散层表面的凹坑可以使液滴的跃离提前。此外,还发现阳极气流通道内液滴一旦形成,将更可能附着在扩散层表面而不易被气流带走。

How to enhance liquid water transport or removal in gas diffusion layers and gas flow channels is an important problem needs to be carefully considered in the research and design of advanced H2/Air PEMFC （proton exchange membrane fuel cell）. In the present work, the FLUENT volume of fluid （VOF） module is employed to simulate and study the dynamic behavior of liquid water droplet formation, detachment and transportation on or from the surface of gas diffusion layer. Water droplets show complex dynamic behavior, which is a result of the combined effect of shearing forces, viscous forces and surface tension. Water droplet detaches from the surface of gas diffusion layer more easily if the contact angle is larger or the gas flow velocity is higher. The effect of contact angle on water droplet dynamic behavior is greater than the gas velocity. A downstream notch on the surface of gas diffusion layer can facilitate the detachment of water droplet. In addition, water droplet dynamic behavior on the anode side is studied as well. It is found that once water droplet forms on the surface of gas diffusion layer, it more possibly sticks on the surface and is hard to be blown away by the H2 flow.