共查询到19条相似文献,搜索用时 140 毫秒
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含湿量对甲烷湿空气自热重整积碳特性的影响 总被引:1,自引:0,他引:1
微动力装置中碳氢燃料催化燃烧被认为是有效的方法,但燃烧室内燃料催化重整普遍存在由积碳导致的催化剂失活等问题.本文采用数值方法研究了微细腔中甲烷湿空气在镍基催化剂上的自热重整反应,重点分析含湿量对甲烷自热重整反应及积碳特性的影响.结果表明:含湿量将增强甲烷重整反应;自热反应散热量和表面积碳浓度均随含湿量增加而降低.混合物... 相似文献
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本文采用与实验I-V曲线高度吻合的多物理场全耦合数值模型来模拟低水甲烷燃料SOFC的运行过程. 基于抗积碳电流密度实验数据推导出的动力学积碳活性判据,利用多场耦合数值模型系统研究了电池工作参数和阳极扩散阻碍层厚度对阳极积碳倾向的影响. 仿真模拟揭示了燃料利用率、电流密度、扩散阻碍层厚度和电池工作电压的相互关系. 结果表明,在阳极添加400 um厚的扩散阻碍层是实现SOFC高功率密度和不积碳运行的最优设计. 这种阳极结构设计对实现高效率低成本的SOFC技术具有重要意义. 相似文献
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提出了一个基于磁动力学方程的宏观唯象理论模型,对纳米级赝自旋阀结构的电流感应磁化翻转效应给出了明晰的物理解释:流入自由层的净自旋流和自由层内的自旋弛豫过程的共同作用,导致自由层总磁矩随时间的改变,甚至产生磁化方向的翻转.模型将“铁磁/非铁磁”界面的自旋相关散射,以及铁磁层中的自旋积累和弛豫过程,统一于宏观的磁动力学方程中.通过求解该方程的解析解,给出了赝自旋阀在电流激励下的磁化翻转条件和临界电流密度的表达式.对该效应的定性解释和数值模拟结果都和实验报道良好符合.根据模型分析了影响临界电流密度的诸因素,并指出提高器件性能的途径.
关键词:
电流感应磁化翻转
磁动力学方程
自旋电子学 相似文献
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用电催化重整方法和NiCuZn-Al2O3催化剂进行生物油模型化合物苯甲醚的水蒸气重整制氢研究,结果表明,在700 oC和4 A条件下,获得的最高碳转化率和氢产率分别为98.3%和88.7%,电催化重整过程中发现的电流促进效应主要归结于重整反应床中温度分布的改变和电阻丝发射的热电子影响. 利用X射线衍射方法分析了反应前后的NiCuZn-Al2O3催化剂结构变化. 实验导出的苯甲醚重整反应表观活化能为99.54 kJ/mol,明显高于乙醇、乙酸和生物油轻质组分的重整反应表观活化能. 相似文献
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Methane steam reforming has been studied over a range of nickel/ceria-gadolinia cermet anodes, over the temperature range
500–700 °C appropriate for intermediate temperature ceriagadolinia based SOFCs. The influence of operating temperature and
methane/steam ratio on the reforming characteristics, methane conversion and product selectivity, and the carbon deposition
on the anode during reforming, has been determined for each anode.
Nickel/ceria powders made from gas atomised intermetallic precursors have been studied as potential anode materials for intermediate
temperature ceria-gadolinia based SOFCs running on natural gas. The powders have been characterised structurally and evaluated
for their methane reforming characteristics and their resistance to carbon deposition during internal reforming, especially
at low steam/methane ratios, over the relevant operating temperature ranges of ceriagadolinia based SOFCs. Their performance
has been compared to conventionally prepared anodes and anodes generated from cast alloys, with very favourable results.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
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J.R. Rostrup-Nielsen J.B. Hansen S. Helveg N. Christiansen A.-K. Jannasch 《Applied Physics A: Materials Science & Processing》2006,85(4):427-430
Fuel cells represent a challenging overlap of catalysis and electrochemistry. This is illustrated by anode reactions in a solid oxide fuel cell. The sites for catalytic conversion of methane and electrochemical conversion of hydrogen on an SOFC anode appear not to be the same. The fuel (methane, hydrogen, etc.) is activated by chemisorption on the nickel surface of the anode. This is linked to the electrochemical reaction at the interface of the electrolyte and the nickel crystals converting oxygen ions into electrons and water by reactions with adsorbed hydrogen atoms resulting from the activation of the fuel. The sites for these reactions appear not to be the same. This is reflected by different sensitivities of the two steps to sulphur poisoning. The role of different sites on the nickel surface for the steam reforming reaction is well understood in terms of impact on activity for methane activation, carbon formation and sintering. The study is supplemented by an analysis of anodes having been exposed to 13000 of operation using a number of characterisation methods. PACS 82.47.Ed; 82.45.-h; 82.65.-s 相似文献
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Yu. D. Varlamov M. P. Predtechenskii S. N. Ulyankin 《Journal of Engineering Thermophysics》2012,21(1):16-27
The object to be investigated is a fuel cell with a free molten carbonate electrolyte, which ensures direct electrochemical
oxidation of solid hydrocarbons. The polarization characteristics of anode and cathode fuel cell assemblies, and also composition
and gas release rate of gaseous products of anode reactions are studied. It is shown that the maximum voltages in the open
cell circuit are obtained when the oxygen-carbon dioxide ratio in the cathode gas mixture corresponds to stoichiometric reaction
coefficients that ensure replenishment of ions in electrolyte. However, the maximum current density values were obtained with
a low carbon dioxide content. It is found that at high current values, anode potential fluctuations are observed. It is shown
that carbon monoxide is the product of anode processes, along with carbon dioxide. The carbon monoxide content grows with
temperature. The carbon dioxide content grows with increasing current in the fuel cell and with growing carbon dioxide content
in cathode gases. The release rate of carbon oxidation products nonlinearly depends on the current value in the fuel cell.
It is concluded that there is interrelation between the mass-exchange processes in the fuel cell, which is determined by the
balance between cathode gas incoming into the reaction zone, the number of molecules generated during fuel oxidation, molecule
dissolution and diffusion into the cathode region, and also the amount of gas released in the form of bubbles. 相似文献
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Polymer electrolyte membrane (PEM) fuel cells are considered to have the highest power density of all the fuel cells. They operate on hydrogen fuel, which is generally produced by reforming of hydrocarbons, and may contain large amounts of impurities such as carbon dioxide, nitrogen, and trace amounts of carbon monoxide. We studied the effect of dilution of hydrogen gas with carbon dioxide on PEM fuel cells by polarization studies. The polarization curves were different when hydrogen gas was diluted with same quantities of carbon dioxide and with nitrogen. It may be due to carbon monoxide formation by reverse shift reaction and poisoning of anode platinum catalyst. Use of Pt–Ru alloy catalyst was found to suppress the poisoning. The effects of hydrogen gas composition, temperature, current density, and anode catalyst on fuel cell performances were examined in this study. 相似文献
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Samaria-doped Ceria Modified Ni/YSZ Anode for Direct Methane Fuel in Tubular Solid Oxide Fuel Cells by Impregnation Method 下载免费PDF全文
以NiO和8%(摩尔分数)氧化钇稳定的氧化锆为原料,采用注凝成型工艺制备了管状固体氧化物燃料电池阳极支撑体.用离子浸渍法对阳极支撑体进行表面修饰.用电化学工作站测单电池交流阻抗和输出性能并且用化学气相色谱仪对电池尾气进行分析.测试结果表明修饰后的阳极在通甲烷的情况下出现了一定程度的积炭,但是积炭现象在一定的测试时间内达到平衡,没有对电池造成破坏,并且显著地提高了电池阳极的电化学性能.单电池在通入氢气和甲烷的情况下最大输出功率密度分别达到了225和400 mW/cm2. 相似文献
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《Solid State Ionics》2006,177(37-38):3323-3331
A performance of an anode-supported tubular Ni–8YSZ/Ni–ScSZ/ScSZ/GDC/LSC cell was investigated at 650–750 °C by feeding model kerosene reformate gas (H2, H2O, CO, CO2, and CH4) to a Ni–8YSZ/Ni–ScSZ anode. Variations of gas composition were observed not only between inlet and outlet of anode to estimate the degree of internal reforming, but also during current input by online quadrupole mass spectrometry and Fourier-transform infrared spectrometry.The electrochemical performance of the cell was independent of reforming temperature of kerosene, i.e. gas composition (in particular CH4 concentration) at moderate anode gas flow rates. At open-circuit states, 10% or less methane in the kerosene-reformed gas was readily converted by steam or CO2 over the Ni–8YSZ/Ni–ScSZ electrode so that gas compositions could almost follow the thermodynamic equilibrium at 650–750 °C. This suggests that the internal reforming should proceed almost completely over the Ni anode. Consumption of H2 and CO and production of CO2 were observed during current input. I–V characteristics remained constant at 650 °C as long as anodic W/F was more than 0.2 kg mmol− 1 s. It was demonstrated that a catalytic activity of an anode electrode for hydrocarbons will be important for SOFCs with liquid fuels such as kerosene in order not to deteriorate cell performance. 相似文献
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天然气发动机缸内热化学重整技术对于开发新型的满足更严格排放法规的天然气发动机有着重要意义,为了探究不同醇类对缸内热化学重整影响的化学反应动力学机理,本文选取甲醇、乙醇与乙二醇三种小分子醇作为加浓燃料,通过流动反应器实验和CHEMKIN模拟,对三者掺混时重整气的生成量以及甲烷的消耗量进行了对比,并对反应路径进行了分析以判断不同燃料掺混产生差异的原因,通过分组对比探讨了醇类燃料碳链长度与羟基数目对重整效果的影响.通过研究发现,小分子醇的碳链长度相同时,羟基数目增加有利于促进重整过程;羟基数目相同时,碳链长度缩短有利于促进重整过程。 相似文献