Liquid phase emission behavior of gas diffusion layer surface in fuel cells

LIU Shuai; YAO Xiaohang; ZHANG Libin; WANG Zhong; PEI Hao

doi:10.13226/j.issn.1006-6772.23060702

Abstract：The two-phase distribution characteristics within the fuel cell flow channel are crucial for enhancing the fuel cell water manage-ment capability,and investigating the flow behavior of multiple liquid droplets on the surface of the flow channel can help to optimize the structure and operating conditions.The dynamic process of liquid water emergence from the gas diffusion layer(GDL)into the flow chan-nel was simulated using the volume of fluid(VOF)method,and the effects of the gas flow rate inside the flow channel,the contact angle on the surface of the GDL,and the pore spacing on the water emergence process and flow behavior were investigated.The results show that the droplets undergo the processes of growth,separation,transport and collisional condensation within the GDL surface.The gas flow rate significantly affects the pressure drop and droplet separation period,with the increase of gas flow rate,the pressure drop increases,the droplet separation period decreases from 14.7 to 4.7 ms,and the water removal ability is significantly enhanced,and the high gas flow rate causes the unstable droplet morphology and flow condition.The wettability of the GDL surface modifies the surface tension,which in turn affects the droplet morphology and flow,and significantly influences the water coverage,and the average water coverage of the GDL surface is significantly affected by the increasing contact angle.The average water coverage on the GDL surface decreases from 20.03%to 9.01%;the water orifice spacing has a greater impact on the droplet collision cycle,small water orifice spacing when the droplets are growing in the process of condensation and large droplet splashing caused by a decrease in airflow velocity in the flow channel,the pressure drop and the water coverage on the GDL surface generates large fluctuations;large water orifice spacing,the velocity field in the flow channel is significantly affected by the previous droplet to obtain a larger velocity after collision is more likely to cause droplet splas-hing.At large water orifice spacing,the velocity field in the flow channel is significantly affected,and the previous droplet obtains a larger velocity,which is more likely to cause droplet splashing due to collision,resulting in a decrease in water coverage at the maximum water orifice spacing,from 16.84%(D=0.8 cm)to 14.69%(D=1.2 cm).The results provide theoretical guidance and technical reference for the optimization of flow channel surface contact angle,GDL pore distribution,air inlet conditions,etc.,which can improve the water transport capacity and efficiency of PEMFC.