微型直接甲醇燃料电池阳极传质及应用基础研究

发布时间：2018-04-01 11:07

本文选题：微型直接甲醇燃料电池　切入点：阳极传质　出处：《哈尔滨工业大学》2014年博士论文

【摘要】：微型直接甲醇燃料电池（Micro Direct Methanol Fuel Cell，μDMFC）是一种能够将液体甲醇的化学能直接转换为电能的装置。由于μDMFC具有能量密度高、燃料容易储存以及系统结构简单等优点，使其成为应用在便携式微小型设备上最有前景的能源之一。然而，μDMFC还存在甲醇渗透、阳极传质效率低、电池组的集成和稳定性不高等问题，导致电池放电性能较低，难于满足便携式应用。本文首先针对主动式的μDMFC建立了两相传质模型，优化设计了主动式阳极流场结构；其次，针对被动式μDMFC阳极传质，建立了被动式μDMFC阳极两相传质模型；最后，提出了一种“4-cell”被动式μDMFC单元电池组结构，对便携式应用开发具有重要的实际意义。针对传统主动式平行流场传质效率低的问题，本文提出了多进多出型平行流场并进行优化。利用建立的μDMFC阳极传质模型描述了优化的阳极流场压力以及流速分布情况，并利用MEMS工艺在硅极板上实现了相应的流场结构。仿真和实验结果一致表明，利用方形凸起优化的流场结构改进效果最佳，较传统的平行流场性能提高一倍。其次，针对传统主动式μDMFC甲醇供给浓度较低的问题，提出了一种复合型主动式阳极流场结构。利用建立的μDMFC阳极传质模型描述了阳极扩散层及催化层内甲醇浓度的分布情况，并利用端板和极板的结合实现了复合流场结构。仿真和实验结果表明，相比于传统平行结构流场，复合型流场结构具有更大的甲醇传质阻力，能够有效地提高甲醇供给浓度。针对被动式μDMFC阳极自然对流现象，本文建立了被动式μDMFC二维、稳态、非绝热模型。模型考虑了被动式μDMFC阳极储液腔内自然对流效应的影响，并且耦合了热和物质传输。整个耦合模型利用有限元方法求解并通过实验验证。仿真结果表明：在竖直放置的条件下，由于阳极自然对流的影响，电池内部的温度从底部到顶部逐渐升高。随着甲醇浓度的增加，电池的温度升高，导致储液腔中的阳极自然对流效应增强，在电池内部形成更大的温度分布扭曲及温差。甲醇渗透率随着甲醇供给浓度的增加而增大。随着电流密度的增加，甲醇渗透现象在较低的供给浓度下逐渐增大，，而在较高的供给浓度下显示出逐渐减小的趋势。以上研究结果更加准确的分析了被动式μDMFC内部的传质过程。为了验证被动式阳极自然对流现象，设计制作了被动式μDMFC单体电池。并在单体电池基础上设计并制作了一种面向应用的“4-cell”被动式μDMFC单元电池组，并利用自设计的电联方法实现单元电池组之间的串联，从而实现μDMFC的多节串联。这种结构可以大大提高电池组的稳定性。通过对电池组稳态及动态性能的全面测试与分析，得到如下结论：在室温的环境下，“4-cell”被动式μDMFC单元电池组的最佳甲醇浓度为5mol/L。单元电池组达到的最大功率为545mW，最大功率密度为29.62mW/cm2；电池组在不同负载模式下体现出良好的动态响应特性和可重复性，并成功应用于驱动电动机以及给手机充电。
[Abstract]:Micro direct methanol fuel cell (Micro Direct Methanol Fuel Cell, DMFC) is a kind of chemical liquid methanol can be directly converted to electrical energy device. Because the DMFC has high energy density, easy storage and fuel system has the advantages of simple structure and other advantages, make it become one of the most promising applications in portable miniature the device's energy. However, there are still DMFC methanol permeability, mass transfer efficiency of anode is low, the integration and stability of the battery group is not high, resulting in discharge performance of the battery is low, it is difficult to meet portable applications. Firstly, the main dynamic DMFC type a two-phase mass transfer model, the optimization design of the active anode flow field structure secondly, according to the DMFC; passive anode mass transfer, a passive DMFC two-phase mass transfer model; finally, proposed a "4-cell" passive DMFC cell group structure of portable The application and development of the type is of great practical significance.
In view of the traditional active mass transfer parallel flow field the problem of low efficiency, this paper proposed a MIMO type parallel flow field and optimized. Using DMFC anode mass transfer model is established to describe the optimization of anode flow field pressure and velocity distribution, flow structure and the corresponding realization of the silicon plate using the MEMS process. Simulation and experiment the results showed that the best improvement using the flow structure of square protrusion optimization, compared with the traditional parallel flow field performance doubled. Secondly, in view of the traditional active DMFC low concentration methanol supply problems, puts forward a composite type active anode flow field structure. Using DMFC anode mass transfer model is established to describe the distribution of anode diffusion layer and the catalyst layer in the methanol concentration, and the combination of the end plate and the plate realizes the composite flow structure. The simulation and experimental results show that compared to the traditional flat With the structure flow field, the compound flow field structure has greater methanol mass transfer resistance and can effectively improve the methanol supply concentration.
For passive DMFC anode natural convection phenomenon, this paper established the passive DMFC two-dimensional, steady-state, non adiabatic model. The model considers the effect of passive DMFC anode liquid storage cavity effect of natural convection, and coupled heat and mass transfer. The coupling model using finite element method and verified by experiments. The simulation results show that: vertical conditions, due to the influence of natural convection inside the battery anode, the temperature gradually increased from the bottom to the top. With the increase of methanol concentration, the cell temperature increased, resulting in enhanced liquid storage cavity in the anode effect of natural convection, the temperature distribution and thermal distortion is formed larger inside the battery and methanol permeability. With the increase of methanol supply concentration. With the increase of current density, methanol permeation phenomenon gradually increased in supply under low concentration and high concentration in supply The trend of gradual decrease is shown. The above results are more accurate to analyze the mass transfer process in the passive muon DMFC.
In order to verify the natural convection of passive anode phenomena, design of passive DMFC single battery. And in the single cell was designed and fabricated for application "4-cell" passive DMFC cell group, and the use of self designed electrical contact method between the unit batteries in series, so as to realize the series. DMFC multi section. This structure can greatly improve the stability of battery. Through comprehensive test and analysis of the static and dynamic performance of the battery, we get the following conclusions: at room temperature, the maximum power optimal methanol concentration 4-cell DMFC unit passive battery pack for 5mol/L. cell group reached 545mW and the maximum power density was 29.62mW/cm2; the battery shows a good dynamic response characteristic and repeatability in the model under different load, and successfully applied to the drive motor and the mobile phone Charge.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM911.4

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