管式固体氧化物燃料电池跨尺度多物理场耦合数值分析优化

发布时间：2018-04-23 14:55

本文选题：固体氧化物燃料电池 + 数值模型　；参考：《江苏大学》2017年博士论文

【摘要】：随着全球经济总量的不断提高,传统的燃烧化石燃料提供动力的方式给环境造成了巨大的压力,而固体氧化物燃料电池(SOFC)是一种可以避开燃烧过程、不受卡诺循环限制而直接把燃料内的化学能转化为电能的设备,具有高效率和低排放的优势,属于与环境兼容的新能源技术。研究以管式SOFC为对象,在电池单元尺度层面上,建立了一个多物理场耦合模型来研究电池构型对其性能的影响。模型中考虑了集流件与电极间的接触电阻,耦合了电子导电过程、离了导电过程、气体输运过程以及电化学反应过程。计算结果表明:通过适当提高运行温度和电极电导率,同时降低电极孔隙率、接触电阻和输出电压有利于SOFC性能的提升;特别当温度较低、阴极电导率较小、阴极孔隙率较大、输出电压较低时,阴极支撑型管式SOFC性能优于阳极支撑型管式SOFC,这也是传统主流采用阴极支撑型设计的原因。然而,一方面,阴极支撑型实际应用中会面临一些限制其性能进一步提升的不利因素,另一方面,阳极支撑型在浓差损失和燃料利用率等方面相对阴极支撑型占优,加之近年来SOFC出现了有利于阳极支撑的新集流件设计,都为阳极支撑型的发展带来了可能。阳极支撑型设计需要合理的管道外侧空气分配方案与之配套,故在电池堆大尺度层面,区别于传统的以阴极支撑型为主的电堆设计,针对阳极支撑型建立了电堆内空气流场模型。计算分析多种设计方案,综合考虑各结构参数对空气流场影响,包括进出口管直径、进出口管数、进出口管布置位置、流通截面、单电池间距等,对多种方案的堆内空气流场各区域进行整体分析和优化设计,在此基础上提出了一种阳极支撑型电堆的新型的空气分配设计方案。新型空气分配器特点如下:(1)沿SOFC单元管长度方向在空气入口平均布置了3根管,从下侧面输送空气。对应的入口空气流量分入3个歧管,歧管内流速降为原来1/3,从而有利于提高SOFC单元间的空气分配均匀性;(2)分配器顶部相对于底部,入口侧相对于出口侧,均采用了截面缩窄的设计。通过增加流动路径流动阻力的方式,降低分配器左侧和顶部区域附近的空气静压强,避免过多的空气通过分配器的左侧和顶部绕过电池单元排列区未经反应直接流出,使更多的气流受迫进入电池单元区域,从而改善空气在电池单元间的空气分配质量;(3)沿SOFC单元管长度方向在电堆右侧空气出口布置了两排尾气收集管,每排的3根管,从上到下管径由小到大变化,具有阻力减小的特性,使得分配器右侧的尾部收集区压力从上到下压力增加的问题得到缓解;(4)入口主管道系列歧管和出口尾气收集系列歧管,两者排列方向呈相互垂直特性,使空气在电堆中的流动兼顾了纵向和横向的均匀性,从而改善了空气在电池单元间及SOFC单元表面的空气分配质量;(5)空气分配器除入口处那个角,其余3个角用圆弧设计。圆弧设计减少了空气流动在分配器直角处的局部压力损失,使空气从入口到出口流动更连续,非电池排列区的空气更多参与电池排列区的反应,提高了空气利用率,减少了空气泵入功;(6)通过调整分配器左窄右宽,上窄下宽,尾气收集管径大小比例,调整空气路径各段流动阻力,达到入口空气各歧管的均匀输入和出口尾气各收集歧管均匀输出。对电池堆的计算结果显示,最终优化方案相比目前的一进一出空气分配方案,各主截面内速度标准偏差从4.0401降为0.9915,无量纲的质量流量比从0.5以上占38.1%提升到0.5以上占87.2%,实现了电堆中空气较均匀分配。与现有技术相比,此空气分配器可为阳极支撑型管式电堆提供可靠的空气分配质量,解决了其实用化面临的技术难题之一,为研发高性能管式SOFC电堆提供了重要的技术支持。
[Abstract]:With the increase of the global economy, the traditional way of burning fossil fuel to supply power has caused great pressure to the environment, and the solid oxide fuel cell (SOFC) is a kind of equipment which can avoid the combustion process and convert the chemical energy of the fuel into the electric energy directly without the restriction of the Kano cycle. The advantage of it is a new energy technology compatible with the environment. A multi physical field coupling model is established to study the effect of the battery configuration on its performance at the cell scale level. In the model, the contact resistance between the collector parts and the electrodes is considered, and the electrical conduction process is coupled with the electrical conduction process in the model. The results show that the contact resistance and the output voltage are beneficial to the improvement of SOFC performance by increasing the operating temperature and electrode conductivity and reducing the electrode porosity, especially when the temperature is low, the cathodic conductivity is smaller, the cathode porosity is larger, and the output voltage is low, the cathode support is low. The performance of the tube type SOFC is better than that of the anode supported tube type SOFC, which is also the reason for the traditional mainstream design of the cathodic support type. On the one hand, the practical application of the cathode support will face some unfavorable factors that limit its performance further. On the other hand, the anode support is relative to the concentration loss and fuel utilization ratio. The support type is dominant. In addition, in recent years, the design of new collection flow parts for anode support has appeared in SOFC. It is possible for the development of anodic support type. The design of anodic support needs a reasonable scheme of air distribution outside the pipe. So, in the large scale level of the battery stack, the area is different from the traditional cathodic support type. The air flow field model in the reactor is established for the anode support type. Various design schemes are calculated and analyzed. The influence of various structural parameters on the air flow field is considered, including the diameter of the inlet and outlet pipe, the number of import and export tube, the arrangement position of the inlet and outlet pipe, the flow section, the single battery space and so on, and the whole area of the air flow field in a variety of schemes is carried out as a whole On the basis of the analysis and optimization design, a new air distribution design scheme for anodic support type electric reactor is proposed. The characteristics of the new air distributor are as follows: (1) 3 pipes are arranged on the air inlet along the length direction of the SOFC unit tube and the air is transported from the lower side. The corresponding inlet air flow is divided into 3 manifold and the flow velocity inside the manifold. It is reduced to the original 1/3, which helps to improve the air distribution uniformity between the SOFC units; (2) the design of cross section narrowing is adopted at the top of the distributor relative to the bottom and the inlet side relative to the outlet side. By increasing the flow resistance of the flow path, the air static pressure near the left and top areas of the distributor is reduced to avoid excessive air. The air distribution quality between the cell units is improved by the direct flow of the cell permutation at the left and top of the distributor through the cell permutation, so that more air flow is forced into the cell area, and the air distribution quality between the cell units is improved. (3) a two row exhaust collection tube is arranged in the right air outlet of the SOFC unit tube, 3 pipes per row, The upper and lower pipe diameter changes from small to large and has the characteristic of decreasing resistance, which makes the problem of increasing pressure from upper to bottom in the right side of the distributor is relieved; (4) the series manifold of the main inlet pipe and the outlet tail gas collects a series of manifold, and the direction of the two arrangement is perpendicular to each other, so that the flow of air in the electric reactor is taken into account. The longitudinal and transverse uniformity improves air distribution quality on the surface of the cell and SOFC unit. (5) the air distributor is designed with a circular arc at the corner of the entrance and the other 3 angles. The arc design reduces the local pressure loss of air flow at the right angle of the distributor, making the air flow more continuous from the entrance to the exit. The air in the battery permutation area is more involved in the reaction of the battery permutation area, which improves the air utilization rate and reduces the power of the air pump. (6) by adjusting the width of the left narrow right, the width of the upper and narrow and the width, the tail gas collects the diameter ratio of the pipe, and adjusts the flow resistance of each section of the air path to achieve the uniform input of the inlet air manifold and the various collection disambiguation of the outlet tail gas. The calculation results of the battery stack show that the final optimization scheme has reduced the standard deviation from 4.0401 to 0.9915 in the main section of the main section compared with the current one out and out air distribution scheme, and the dimensionless mass flow rate is increased to more than 0.5 from 38.1% to more than 0.5, and the air distribution in the reactor is more evenly distributed. In comparison, the air distributor can provide reliable air distribution quality for anodic supported tubular electric reactor and solve one of the technical difficulties faced by the practical application. It provides important technical support for the research and development of high performance tubular SOFC electric reactor.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM911.4

【参考文献】