气体扩散层侵入流道对燃料电池水管理影响研究

Investigation on impact of gas diffusion layer intrusion into channel on water management in fuel cell

质子交换膜燃料电池在装配过程中,气体扩散层(GDL)会因为装配压力产生形变而侵入流道。基于流体体积法建立截面形状分别为矩形、梯形和正方形的流道在GDL不同侵入程度下的数值模型,并对其进行气-液两相流行为研究,得到了液体滞留、排水效果、GDL面传质面积等方面规律。GDL侵入流道时,液体在排出过程中破碎程度减小,液体更容易积聚在一起,影响液体滞留效果。矩形截面流道排液时间更长,梯形和正方形截面流道液体排出时刻滞后。GDL侵入流道时,进气流速的增加使得较为聚集的液体排出速度稳定,并未大幅减小。GDL侵入流道程度较大时,矩形截面流道更多液滴黏附在流道侧壁与GDL面使得GDL面覆盖率较大,梯形截面流道顶部会形成稳定的薄膜流,排液速度大且GDL面覆盖率小。

During the assembly process of proton exchange membrane fuel cell(PEMFC)stacks,the gas diffusion layer(GDL)will deform due to the assembly pressure and invade the flow channel.Utilizing the volume of fluid(VOF)method,numerical models were established for flow channel with rectangular,trapezoidal,and square cross sections to investigate the two-phase gas-liquid flow behavior under varying degrees of GDL intrusion.The insights into liquid retention,drainage effectiveness,and GDL surface mass transfer area were analyzed.In instances of GDL intrusion into flow channel,the fragmentation of liquid during the discharge process decreases,facilitating the accumulation of liquid into larger droplets or film formation.The intrusion of GDL into the flow channel affects the liquid retention during the internal drainage process,with rectangular cross-section channel exhibiting longer drainage time,and trapezoidal and square cross-section channel experiencing delayed liquid discharge moments.In the presence of GDL intrusion into flow channel,the reduction in channel cross-sectional area results in an increased inlet gas velocity,maintaining a stable discharge velocity for relatively clustered liquid droplets without a substantial decrease.For cases of substantial GDL intrusion,the rectangular cross-section channel shows a higher incidence of liquid droplets adhering to the channel sidewalls and GDL surface,resulting in a larger GDL surface coverage.Additionally,in channels with significant GDL intrusion,the trapezoidal cross-section channel exhibits the formation of a stable film flow at the top,with higher drainage velocity and smaller GDL surface coverage.