直接甲醇液流燃料电池的模拟与仿真

发布时间：2018-03-15 04:36

本文选题：直接甲醇液流燃料电池　切入点：二维模型　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：直接甲醇燃料电池（DMFC）的阴极水淹问题，甲醇渗透问题，以及贵金属催化剂的成本问题，是DMFC商业化的主要障碍。直接甲醇液流燃料电池（DMRFC）是采用液流电池阴极替代传统直接甲醇燃料电池（DMFC）阴极的一种新型燃料电池。由于DMRFC阴极使用Fe3+/Fe2+氧化还原电对，不使用贵金属催化剂，降低了电池成本，阳极和阴极都为液体进料，避免了阴极水淹和甲醇渗透氧化等问题。目前通过实验手段来获得DMRFC内部的物理化学过程，如工作温度分布、压强分布、物质浓度分布、电流密度分布等比较困难，，而且代价昂贵，实验周期较长。采用模拟仿真方法成本低，时间短，可以依据不同的实际需要改变运行条件，来获得完整的模拟数据。通过对DMRFC的模拟，可以加深对燃料电池内部工作机理的认识，从而根据实际的需求来优化电池的结构和确定电池的最佳工作条件,具有重要的指导意义。本文以DMRFC单电池为研究对象，依据有限元方法，使用COMSOL模拟仿真软件，分别建立了DMRFC的二维单相模型和二维两相模型。模型考虑了流体流动，物质传输，电荷传输和电化学反应等过程，模拟区域包括阳极流道，阳极扩散层，阳极催化层，质子交换膜和阴极电极。 DMRFC二维单相模型中，忽略阳极产生二氧化碳气体的影响，考虑甲醇和水通过质子交换膜的渗透，通过耦合电荷守恒方程，质量守恒方程，物种守恒方程和动量守恒方程，研究了不同操作条件和结构参数对电池性能的影响。研究结果表明电池运行温度，甲醇和Fe3+浓度，阴极电极厚度对电池性能影响很大。随着阴极电极厚度的减小，电池运行温度的升高，电池的性能将显著增加；当甲醇浓度从2M升高到16.7M时，电池性能不断提高，当甲醇浓度继续提高时，电池性能开始降低；提高阳极流量不影响电池性能；提高阴极流量和Fe3+浓度将有利于提高电池性能。在DMRFC二维单相模型基础上，通过考虑阳极产生二氧化碳气体的影响，建立了DMRFC二维两相模型，研究了二氧化碳气体浓度和压强在电池内部的分布。研究结果表明二氧化碳浓度沿阳极流道方向不断增加；二氧化碳气体压强沿阳极催化层到阳极流道方向不断降低；减少阳极扩散层的厚度、增加阳极催化层的厚度，增大阳极扩散层和催化层的孔隙率，提高阳极和阴极流量，有利于提高电池的性能，当阴极Fe3+浓度低于1.41M时，提高Fe3+浓度能显著提高电池性能，当阴极Fe3+浓度高于1.41M时，Fe3+浓度对电池性能影响不大。
[Abstract]:The cathodic flooding, methanol permeation, and the cost of noble metal catalysts for DMFCs, Direct methanol liquid flow fuel cell is a new type of fuel cell which uses liquid flow cell cathode instead of traditional direct methanol fuel cell cathode. Because DMRFC cathode uses Fe3 / Fe 2 redox electric pair, direct methanol liquid flow fuel cell is a new type of fuel cell. Without noble metal catalyst, the cell cost is reduced, the anode and cathode are liquid feed, and the problems of cathodic flooding and methanol permeation oxidation are avoided. At present, it is difficult to obtain physical and chemical processes in DMRFC by experimental means, such as working temperature distribution, pressure distribution, material concentration distribution, current density distribution, and so on. The experiment period is long. The simulation method is of low cost and short time. The simulation data can be obtained by changing the operating conditions according to different actual needs. It can deepen the understanding of the internal working mechanism of the fuel cell, thus optimize the structure of the battery and determine the optimal working conditions of the battery according to the actual demand, which has important guiding significance. Based on the finite element method and COMSOL simulation software, the two-dimensional single-phase model and two-dimensional two-phase model of DMRFC single cell are established in this paper. The model takes into account the fluid flow and mass transfer. The simulated regions include anodic channel, anodic diffusion layer, anodic catalytic layer, proton exchange membrane and cathode electrode. In the DMRFC two-dimensional single-phase model, the influence of anode producing carbon dioxide gas is ignored, and the permeation of methanol and water through the proton exchange membrane is considered, and the coupling charge conservation equation, mass conservation equation, species conservation equation and momentum conservation equation are considered. The effects of different operating conditions and structure parameters on the performance of the battery are studied. The results show that the operating temperature, concentration of methanol and Fe3, and the thickness of cathode electrode have great influence on the performance of the battery. With the increase of the operating temperature of the battery, the performance of the battery will increase significantly, when the concentration of methanol increases from 2m to 16.7 M, the performance of the battery will continue to improve, and when the concentration of methanol continues to increase, the performance of the battery will begin to decrease, and the increase of the anode flow rate will not affect the performance of the battery. Increasing cathode flow rate and Fe3 concentration will help to improve the performance of the cell. Based on the DMRFC two-dimensional single-phase model, a two-dimensional DMRFC two-phase model is established by considering the effect of anode generation of carbon dioxide gas. The distribution of carbon dioxide concentration and pressure in the cell is studied. The results show that the concentration of carbon dioxide increases along the anodic channel direction, and the pressure of carbon dioxide gas decreases from the anode catalytic layer to the anode channel. Reducing the thickness of anode diffusion layer, increasing the thickness of anode catalytic layer, increasing the porosity of anode diffusion layer and catalytic layer, and increasing anode and cathode flow rate are beneficial to improve the performance of the battery. When the concentration of cathode Fe3 is lower than 1.41 M, Increasing the concentration of Fe3 can significantly improve the performance of the battery. When the concentration of cathode Fe3 is higher than 1.41m, the concentration of Fe3 has little effect on the performance of the battery.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM911.4

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