A mathematical model of a tubular solid oxide fuel cell with specified combustion zone

A numerical model has been developed to simulate the effect of combustion zone geometry on the steady state and transient performance of a tubular solid oxide fuel cell (SOFC). The model consists of an electrochemical submodel and a thermal submodel. In the electrochemical model, a network circuit of a tubular SOFC was adopted to model the dynamics of Nernst potential, ohmic polarization, activation polarization, and concentration polarization. The thermal submodel simulated heat transfers by conduction, convention, and radiation between the cell and the air feed tube. The developed model was applied to simulate the performance of a tubular solid oxide fuel cell at various operating parameters, including distributions of circuits, temperature, and gas concentrations inside the fuel cell. The simulations predicted that increasing the length of the combustion zone would lead to an increase of the overall cell tube temperature and a shorter response time for transient performance. Enlarging the combustion zone, however, makes only a negligible contribution to electricity output properties, such as output voltage and power. These numerical results show that the developed model can reasonably simulate the performance properties of a tubular SOFC and is applicable to cell stack design.     

利用生物活性炭提高微生物燃料电池产电性能

通过比较三组微生物燃料电池（MFC）的产电性能,考察使用生物活性炭（BAC）对提高MFC产电性能所起的作用。它们分别是：在阳极室内未投加活性炭的、投加了柱状活性炭的和投加了小颗粒活性炭的3种MFC。投加时机是在电池启动阶段,此时微生物在活性炭上驯化出生物膜,即形成生物活性炭,目的是辅助阳极富集更多微生物。结果表明,投加了小颗粒活性炭的MFC在产电性能和污水处理上具有优势。该电池最大容积功率密度达到1540 mW/m³ ,COD去除率达到了88%。     

A droplet size dependent multiphase mixture model for two phase flow in PEMFCs

A droplet size dependent multiphase mixture model is developed in this paper, and the droplet size in the gas channel can be considered as a parameter in this multiphase mixture model, which includes the effect of gas diffusion layer (GDL) properties and the gas drag function and cannot be considered in the commonly used multiphase mixture model in the references. The three-dimensional two phase and non-isothermal simulation of the PEMFCs with a straight flow field is performed. The effect of droplet size on the liquid remove, the effect of liquid water on the heat transfer and the effect of gas flow pattern on the heat and mass transfer are mainly investigated. The simulation results show that the large droplet is hard to be dragged by the gas, so it produces large water saturation. The results of the heat transfer show that the liquid water hinders the heat transfer in the GDL and catalyst layer, so it produces the large relative high temperature area, and there are large temperature difference and water saturation in the PEMFCs operated with coflow pattern compared with counter flow pattern.     

质子交换膜燃料电池内部传热传质三维模拟

针对常规流场质子交换膜燃料电池提出了三维非等温数学模型。模型考虑了电化学反应动力学以及反应气体在流道和多孔介质内的流动和传递过程,详细研究了水在质子膜内的电渗和扩散作用。计算结果表明,反应气体传质的限制和质子膜内的水含量直接决定了电极局部电流密度的分布和电池输出性能;在电流密度大于0.3~0.4A/cm2时开始出现水从阳极到阴极侧的净迁移;高电流密度时膜厚度方向存在很大的温度梯度,这对膜内传递过程有较大影响。     

Pt/MoC的制备及其在电解水析氢反应中的性能

以钼酸铵和氯铂酸为原料,通过原位程序升温碳化过程,合成制备了负载量不同的Pt/MoC催化剂并考察了其在电解水析氢反应（HER）中的催化性能。用XRD、BET、SEM、TEM、XPS对催化剂的微观结构及物理化学性质进行了表征。结果表明,Pt的负载改变了碳化过程碳化钼形成的拓扑结构,Pt负载后的样品更容易形成α-Mo2C相。Pt的负载量对碳化钼催化剂在HER反应中具有显著的影响,1.6Pt/MoC催化剂表现出最优催化效果（过电势ηonset= 108 mV,塔菲尔斜率b = 74 mV/dec）及较低的阻抗（18.77 Ω）,可以与商业Pt/C催化剂相媲美。     

平板形障碍物对气云爆炸强度影响的实验研究

以乙炔 -空气为介质实验研究了平板形障碍物对可燃气云爆燃强度的影响 ,运用曲线拟合方法获得了弱点火条件下气云爆燃时平板形障碍物上的压力分布与气云初始半径、平板离开爆源中心的距离之间的关系式 ,为气云爆炸的缩放研究提供了基础 .讨论了平板形障碍物对气云爆燃强度的影响 .     

SOFC中干甲烷流量对Ni-YSZ阳极上反应的影响

为为探讨SOFC中干甲烷流量对反应的影响,采用色谱在线检测阳极尾气,总结阳极尾气的变化规律,在此基础上,分析干甲烷在固体氧化物燃料电池Ni-YSZ阳极上的反应,寻找干甲烷流量与电流对电池阳极反应影响的数学关系。依据甲烷基元反应的活化能分析反应的途径,结果表明,随电流密度以及氧离子流量的增加,干甲烷与不同电流密度下的氧离子依次发生电化学反应。这些电化学反应分别是甲烷部分氧化反应生成CO、H2并产生电子,或生成CO、H2O、H2和产生电子的反应,或产生CO、H2O和产生电子的反应,或甲烷完全氧化的电化学反应。高流量甲烷只发生消耗氧离子最少的部分氧化反应,中流量甲烷发生前两个或前三个反应。依据法拉第第一定律及反应物之间的关系,确定甲烷的低、中、高流量的判定依据分别为:v(CH4)小于等于I/(4F),v(CH4)大于等于I/(4F)以及小于等于I/(2F),v(CH4)大于等于I/(2F)。     

Reactions of low and middle concentration dry methane over Ni/YSZ anode of solid oxide fuel cell

Directly using methane in solid oxide fuel cells (SOFC) requires the knowledge of the reaction of methane over the anode. The reactions of low and middle concentration dry methane were studied over the anode of solid oxide fuel cell with Ni/yttria-stabilized zirconia (YSZ) anode and YSZ electrolyte. The production rates of different types of gas at anode outlet were measured at different current density. Mass balance and relationships between production rates and reaction rates were used to analyze the chemical and electrochemical reactions that took place in parallel. When dry methane is in low concentration, methane decomposition and deposited carbon oxidation occurs at low current density with the overall reaction being partial oxidation of methane (POM). With increased current density, hydrogen oxidation and carbon monoxide oxidizing to carbon dioxide take place simultaneously, and the overall reaction becomes the direct oxidation of methane (DOM). When DOM occurs, a portion of methane participates the POM. However, the rate of POM decreases with increased current density. At medium methane concentration, only partial oxidation of methane takes place. Carbon deposition was found in all the tests across the concentration range investigated.     

二维流动模型的喷射器性能分析研究

采用二维轴对称流动模型，计算分析了吸入通道内回流现象、喷射器“恒能力”现象与静压力在轴线上分布情况之间的关系；探讨了工作压力对喷射器性能的影响。结果表明：持续降低出口压力会在混合室内形成激波，喷射因数保持不变；工作压力过高会在混合室内产生壅塞，反而降低喷射因数；吸入压力过低会在喷射器吸入通道内产生回流现象，影响喷射式制冷系统运行的安全性。     

Low-temperature steam reforming of methanol to produce hydrogen over various metal-doped molybdenum carbide catalysts

Various transition metals (M = Pt, Fe, Co, and Ni) were selected to support on molybdenum carbides by in-situ carburization metal-doped molybdenum oxide (M-MoO_x) via temperature-programmed reaction (TPR) with a final temperature of 700 °C in a reaction gas mixture of 20% CH₄/H₂. XRD analysis results indicated that β-Mo₂C phase was formed in the case of Fe, Co, or Ni doping while α-Mo₂C phase was appeared with the β-MoC_1−x phase in the case of Pt doping. With the increase in Pt doping amount, more α-MoC_1−x phase was produced. As-prepared metal doped molybdenum carbides were investigated as alternative catalysts for the steam reforming of methanol. Comparing with the undoped molybdenum carbide such as β-Mo₂C, metal-doped one showed higher methanol conversion and hydrogen yield. It is found that Pt doped molybdenum carbide had the highest catalytic activity and selectivity among the prepared catalysts and methanol conversion reached 100% even at a temperature as low as 200 °C, and remained a long-time stability with a stable methanol conversion.