质子交换膜内水传递模拟研究

发布时间：2018-05-13 13:12

本文选题：质子交换膜燃料电池 + 质子交换膜　；参考：《沈阳建筑大学》2015年硕士论文

【摘要】：燃料电池因其发电效率高,可长时间连续工作,无污染,无噪声,被认为是21世纪首选的清洁高效的发电技术。其中质子交换膜燃料电池(PEMFC)是发展最快、应用最广和最有前途的燃料电池,受到了各国政府及企业的高度重视。质子交换膜是PEMFC的关键技术材料,它既是一种致密的选择性透过膜,又是电解质(传递质子)和电极活性物质(电催化剂)的基底,是整个电池的心脏。膜中水的含量越高则离子传导能力越强,其内部水的传递与分布对质子传导能力以及氧气在膜中的溶解扩散有很大影响,这将直接影响到PEMFC的性能。因此,保持膜中水含量的均衡对于PEMFC的性能十分重要。由于质子交换膜非常薄,只有几十至上百微米,所以对于膜中水含量的测定非常困难,尤其是采用实验的方法进行直接的研究,所以目前只能采用软件模拟的方式。故本文采用建模模拟的方法,对质子交换膜中水浓度的分布进行理论研究。叙述了质子交换膜内水传递的机理模型,及影响膜内水传递的因素。在Springer的膜内扩散模型的基础上进行了适当的改进,建立了新的数学模型,并应用软件建立了 PEMFC的三维模型进行模拟。再根据浓度梯度的定义公式及模拟结果中的水浓度梯度与膜阴极/阳极表面水浓度的分布图,进一步推算出质子交换膜内部水浓度的分布。研究结果表明:在膜的同一表面上浓度梯度方向不均一,在进气口处,靠近膜阳极侧的浓度梯度值较大;在出气口处,靠近膜阴极侧的浓度梯度值较大。膜阴极和阳极表面水浓度变化的大体趋势是相同的,水浓度沿气流方向都是呈抛物线趋势递增的,但在数值上阴极侧的水浓度要明显高于阳极侧水浓度;沿膜厚度方向水浓度的变化率在进气口处最小,中间部分次之,出气口处最大;从膜的阳极表面到阴极表面,进气口处的水浓度是逐渐递增的,出气口处虽然在1/2膜厚度的附近有一小段下降的趋势,但其各处的水浓度都是最大的,中央位置处沿厚度方向靠近阳极侧的水浓度是整个膜各处最低的,甚至低于进口处很多,更容易发生缺水现象。
[Abstract]:Fuel cell is considered as the preferred clean and efficient power generation technology in the 21st century because of its high power generation efficiency, long time continuous operation, no pollution, no noise. Proton exchange membrane fuel cell (PEMFC) is the most widely used and promising fuel cell, which has been paid great attention to by governments and enterprises all over the world. Proton exchange membrane is the key material of PEMFC. It is not only a dense selective permeation membrane, but also the substrate of electrolyte (transfer proton) and electrode active material (electrocatalyst), which is the heart of the whole battery. The higher the water content in the membrane, the stronger the ionic conductivity. The transport and distribution of water in the membrane have a great influence on the proton conductivity and the dissolved diffusion of oxygen in the membrane, which will directly affect the properties of PEMFC. Therefore, it is very important for the performance of PEMFC to maintain the equilibrium of water content in the film. Because the proton exchange membrane is very thin, it is only tens to hundreds of microns, so it is very difficult to determine the water content in the membrane, especially the direct research by the experimental method, so the software simulation method can only be used at present. Therefore, the distribution of water concentration in proton exchange membrane is studied theoretically by modeling and simulation. The mechanism model of water transport in proton exchange membranes and the factors affecting water transport in membranes are described. On the basis of Springer's intramembrane diffusion model, a new mathematical model is established, and the 3D model of PEMFC is established by software. According to the definition formula of the concentration gradient and the distribution diagram of the water concentration gradient and the surface water concentration on the cathode / anode surface of the membrane, the distribution of water concentration in the proton exchange membrane was further calculated. The results show that the concentration gradient on the same surface of the membrane is not uniform, the concentration gradient near the anode side of the membrane is larger at the inlet, and the concentration gradient near the cathode side of the membrane is larger at the outlet. The variation trend of water concentration on the surface of the film cathode and anode is the same, and the water concentration increases along the flow direction, but the water concentration on the cathode side is obviously higher than the water concentration on the anode side. The change rate of water concentration along the film thickness direction is the smallest at the inlet, the second at the middle part, and the largest at the outlet, and the water concentration in the inlet increases gradually from the anode surface of the film to the cathode surface. Although there is a small downward trend at the outlet near the thickness of 1 / 2 of the film, the water concentration everywhere is the largest, and the water concentration in the central position near the anode side in the direction of thickness is the lowest in the whole film, and even much lower than that in the inlet. Water shortages are more likely to occur.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.4

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