【作者】 杨磊；

【导师】 靳遵龙；

【作者基本信息】 郑州大学 ， 动力工程（专业学位）， 2022， 硕士

【摘要】 固体氧化物燃料电池(Solid Oxide Fuel Cell,SOFC)可以直接将燃料的化学能转化为电能,其转换过程不受限于卡诺循环,并且具有高效环保,燃料灵活性强等优点,对解决能源紧缺和环境污染等问题有着重要意义。作为SOFC的一种构型,瓦楞式SOFC由于阳极-电解质-阴极(Positive-Electrolyte-Negative,PEN)设计为波纹状,电化学反应面积较大,性能较为优越,具有较好的研究前景。本文利用COMSOL软件建立了瓦楞式SOFC数值模型,并基于有限元方法进行求解,系统地考察了结构参数、操作条件和材料参数对瓦楞式SOFC性能的影响规律。本文主要研究内容如下:(1)研究了肋宽、电极厚度、电解质厚度和流道高度等结构参数对瓦楞式SOFC性能曲线、组分分布、温度分布以及过电势性能的影响。结果表明减小肋宽可以有效降低浓差极化,提升电池的输出性能。肋宽从1.9 mm减小到1 mm时,电池最大输出功率密度提升了14.12%;阴极厚度越大,电池的平均温度和温度梯度越高,输出性能越优;阳极厚度的增加使阳极内气体扩散阻力增大,导致浓差极化提高,气体分布均匀性下降;减小电解质厚度可以显著降低SOFC的欧姆极化,提高电池的性能及燃料利用率;保持电池的宽度恒定时,电子电流密度随着流道高度的增加而增大。(2)研究了入口燃料组分、阳极入口流速和阴极入口流速等操作条件对瓦楞式SOFC性能的影响。结果表明入口氢气摩尔分数和阳极入口流速越高,电池输出性能越好,而燃料利用率越低。提高入口氢气摩尔分数会使电池的平均温度和温度梯度增大。阴极入口流速较低时浓差极化现象较为显著,而随着阴极入口流速的增大,电池的浓差极化和温度均不断降低。当阴极入口流速达到3 m/s时,再提升阴极入口流速对瓦楞式SOFC性能影响很小。(3)建立了六种不同气体流动模式的多通道瓦楞式SOFC模型,考察了流动模式对电池性能的影响。结果表明通过改变气体流动方式,电池的峰值温度降低了38.9 K,在燃料和空气流动方向相反的基础上,电池堆栈上下两层流动方向也相反的流动方式性能较为优越。(4)考察了连接体热导率和接触电阻对瓦楞式SOFC温度分布、极化损失和电性能等的影响。结果表明提高连接体热导率可以改善SOFC的散热性能,但会导致活化极化和欧姆极化增大;接触电阻越大,电池温度越低,接触电阻从0.01Ω·cm~2增大到0.04Ω·cm~2,峰值温度降低了4.9 K。电池的平均电流密度随着接触电阻的增大近似线性下降。更多还原

【Abstract】 Solid oxide fuel cells(SOFC)can directly convert the chemical energy of the fuel into electrical energy,the conversion process is not limited to the Carnot cycle,and it has the advantages of high efficiency and environmental protection,great fuel flexibility,etc.,which is important to solve the problems of energy shortage and environmental pollution.As a configuration of SOFC,the MOLB-type SOFC has a promising prospect due to its corrugated anode-electrolyte-cathode(Positive-Electrolyte-Negative,PEN)design,which provides a large electrochemical reaction area and superior performance.A numerical model of MOLB-type SOFC was established with COMSOL software in this paper,and the solution is based on the finite element method,the influence law of structural parameters,operation conditions and material parameters on the performance of MOLB-type SOFC is systematically investigated.The main research contents of this paper are as follows.(1)The effects of rib width,electrode thickness,electrolyte thickness and flow channel height on the performance curves,composition distribution,temperature distribution and overpotential changes of MOLB-type SOFC were studied.The results show that the decrease of rib width can significantly reduce the concentration polarization and improve the output performance of cell.The maximum output power density of the cell is increased by 14.12%when the rib width is reduced from 1.9 mm to 1 mm.The thicker cathode electrode,the higher average temperature and temperature gradient of the cell,and the better output performance.The increase of anode thickness increases the gas diffusion resistance in anode,resulting in higher concentration polarization and lower gas distribution uniformity.The reduction of electrolyte thickness can significantly reduce the ohmic polarization and improve the performance and fuel utilization of cell.When keeping the width of the cell is a constant,the electron current density increases with the increase of the flow channel height.(2)The effects of the inlet fuel fraction,anode inlet flow rate and cathode inlet flow rate on the performance of MOLB-type SOFC were investigated.The results show that the higher inlet hydrogen molar fraction and anode inlet flow rate,the better output performance of the cell,while the lower the fuel utilization.The average temperature and temperature gradient of the cell increase with the increase of inlet hydrogen molar fraction.The concentration polarization is significant under low cathode inlet flow rate,while the concentration polarization and temperature of the cell decrease with the increase of the cathode inlet flow rate.When the cathode inlet flow rate reaches 3 m/s,the effect of further increasing the cathode inlet flow rate on the performance of MOLB-type SOFC is little.(3)Six models of multi-channel MOLB-type SOFC under different gas flow patterns were developed,the effect of the flow pattern on the performance of the cell was studied.The results show that the peak temperature of the cell is reduced by 38.9K by changing the gas flow pattern,the best performance is obtained when the fuel and air flow are in contrary direction,and at the same time the gas flow direction of the upper and lower layers of cell stack is also opposite.(4)The effects of thermal conductivity of the interconnector and contact resistance on the temperature distribution,polarization loss and electrical performance of MOLB-type SOFC were investigated.The results show that the thermal performance of SOFC can be improved by increasing the thermal conductivity of the connector,but causes an increase of activation polarization and ohmic polarization.The higher contact resistance,the lower temperature of the cell.The peak temperature decreases by 4.9 K when the contact resistance increases from 0.01Ω·cm~2 to 0.04Ω·cm~2.The average current density of the cell decreases approximately linearly with the increase of the contact resistance.更多还原