Modeling of the electrolyte distribution in representative volumes

代表性体积中电解质分布的建模

• 批准号: 316993420
• 负责人: Professor Dr.-Ing. Ulrich Nieken
• 金额: --
• 依托单位: Institut für Chemische Verfahrenstechnik (ICVT)
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/316993420?language=en
• 关键词: Modeling; electrolyte; distribution; representative; volumes

In the first project phase we could show that it is possible to simulate the penetration of an electrolyte into a gas diffusion electrode on the pore scale. A particular difficulty is the description of the mixed wetting behavior. While the silver phase is wetted by the electrolyte, the PTFE part is strongly hydrophobic and prevents the penetration of the electrolyte. The phase boundary may get in contact with both, electrolyte and PTFE. The numerical effort is very high, therefore only small volumens of the real structure could be considered. Simulation results suggest that the electrolyte exhibits fingering behaviour and forms strongly fractal structures.The goal for the second funding period is to simulate the electrolyte distribution in volumes that can be considered representative. For this purpose, a hybrid calculation method is proposed. The vicinity of the free phase boundaries will be rigorously calculated, while the flow of the electrolyte through filled pores is simplified and modelled as flow resistances. A speed up of the calculation shall be achieved by a fully implicit time integration for the SPH simulation on the one hand, and by parallel calculations of the moving phase boundaries on the other hand.From preliminary measurements it is known that an electric potential leads to a better wetting of the silver phase by the electrolyte. This behaviour, known as "electrowetting", will be considered in the second funding period for the simulation of the electrolyte distribution.In order to validate the model, capillary pressure saturation measurements on GDE’s will be carried out, whereby the electric potential is varied. This allows the comparison of the integral electrolyte holdup with the simulated holdup. Spatially resolved measurements of the electrolyte distribution by the AK Manke allows a detailed validation on the pore scale.

在第一个项目阶段，我们可以证明，它是可能的，以模拟渗透的电解质进入气体扩散电极上的孔隙规模。一个特殊的困难是混合润湿行为的描述。当银相被电解质润湿时，PTFE部分是强疏水性的并且防止电解质的渗透。相界可以与电解质和PTFE两者接触。数值工作量非常大，因此只能考虑真实的结构的小体积。模拟结果表明，电解质表现出指状行为，并形成强烈的分形结构。第二个资助期的目标是模拟电解质的体积分布，可以被认为是有代表性的。为此，提出了一种混合计算方法。自由相边界的附近将被严格计算，而通过填充的孔隙的电解质的流动被简化和建模为流动阻力。一方面，通过SPH模拟的全隐式时间积分，另一方面，通过移动相边界的并行计算，应实现计算的加速。从初步测量可知，电势导致电解质更好地润湿银相。在第二个供资期间，将考虑这种称为“电润湿”的行为，以模拟电解质分布，为了验证模型，将对GDE进行毛细管压力饱和度测量，从而改变电势。这允许比较整体电解质持液率与模拟持液率。通过AK Manke对电解质分布进行空间分辨测量，可以对孔隙尺度进行详细验证。