Summary
Fuel cell vehicles face complicated road conditions, which may impact on the output performance of fuel cell stacks. In the present study, the water transport in the gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC) under vibration conditions are investigated. A stochastic method is employed to reconstruct the 3‐D GDL with experimentally validated varying porosities. The volume of fluid (VOF) method is adopted to investigate the two‐phase problems. Sinusoidal vibration source terms are superposed, which can vary with required amplitudes and directions. Over time, the water transport process takes three steps: water intrusion, water accumulation, and water removal. The water intrusion tends to start from the sides of the GDL, then spreads into the central area. Compared with the no‐vibration case, the water saturations are higher in both the vertical and horizontal vibration cases. The vibration will enhance the water transport through GDL layers. As such, the higher the vibration amplitude and frequency, the larger the water saturation. Accordingly, the water saturation of the GDL vary sinusoidally over time. The water breakthrough paths are identified and compared during the water removal processes. Vibration in the horizontal direction is much easier to promote the water transport inside a layer compared with vibration in the vertical direction. More substantial water saturation in the GDL layers will restrict the gas transfer paths. Consequently, less oxygen will participate in the reaction, which will further impact on the fuel cell performance.
Water management in porous electrodes bears significance due to its strong potential in determining the performance of proton exchange membrane fuel cell. In terms of porous electrodes, internal water distribution and removal process have extensively attracted attention in both experimental and numerical studies. However, the structural difference among the catalyst layer (CL), microporous layer (MPL), and gas diffusion layer (GDL) leads to significant challenges in studying the two-phase flow behavior. Given the different porosities and pore scales of the CL, MPL, and GDL, the model scales in simulating each component are inconsistent. This review emphasizes the numerical simulation related to porous electrodes in the water transport process and evaluates the effectiveness and weakness of the conventional methods used during the investigation. The limitations of existing models include the following: (i) The reconstruction of geometric models is difficult to achieve when using the real characteristics of the components; (ii) the computational domain size is limited due to massive computational loads in three-dimensional (3D) simulations; (iii) numerical associations among 3D models are lacking because of the separate studies for each component; (iv) the effects of vapor condensation and heat transfer on the two-phase flow are disregarded; (v) compressive deformation during assembly and vibration in road conditions should be considered in two-phase flow studies given the real operating conditions. Therefore, this review is aimed at critical research gaps which need further investigation. Insightful potential research directions are also suggested for future improvements.
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