【作者】 刘伟；

【导师】 张竹茜；

【作者基本信息】 北京交通大学 ， 热能工程， 2018， 硕士

【摘要】 质子交换膜燃料电池(PEMFC)具有发电效率高、比功率大、工作温度低、无污染等特点,正在成为世界各国的研究热点。目前关于PEMFC的研究始终围绕性能、寿命和成本三大方向,其中燃料电池内部气液两相流动是影响电池性能的重要因素。本文首先建立质子交换膜燃料电池单体单通道多相、多维、多物理场的数学物理模型,重点涉及燃料电池内部流体的流动、多孔电极微结构内组分的扩散、电化学反应以及产物水相变的传输机理。分析归纳了操作参数对燃料电池性能的影响规律,并通过改变流场板流道几何形状对燃料电池进行了优化分析;其次探究了不同环境温度下质子交换膜燃料电池内部水的存在形态,对低温环境下质子交换膜燃料电池运行停机后残留液态水进行吹扫模拟;最后通过理论计算和数值模拟给出了低温环境下质子交换膜燃料电池辅助启动预热分析。具体研究结果如下:(1)对三维质子交换膜燃料电池进行数值仿真,分析了反应气体湿度、运行压力、运行温度等参数对燃料电池性能的影响,数值模拟结果表明:增大阳极反应湿度可以减小质子传递阻力;当运行温度低于临界温度时,升高运行温度增加催化剂活性并降低阴极侧的液态水饱和度;增大运行压力改善反应气体的速率和减少水蒸气相变。(2)质子交换膜燃料电池在低温环境下运行停机后,需要对内部残留的液态水进行吹扫,避免残留液态水结冰导致燃料电池结构损坏或导致下次启动失败。采用干燥的氮气对燃料电池进行吹扫,保证燃料电池质子交换膜内含水量在3-5之间是保证下次成功启动的前提条件。(3)当质子交换膜燃料电池在低温环境下冷启动时,为了避免启动失败对燃料电池部件造成损坏,采用液态水和氮气预热辅助冷启动可以显著减少启动预热时间。当燃料电池处于-30℃时,预热流体温度为30℃,阴阳极预热流体采用逆流方式,预热时间为8.55s。更多还原

【Abstract】 Proton exchange membrane fuel cell(PEMFC)with the characteristics of high power generation efficiency,large specific power,low working temperature and no pollution has gradually been a focus field worldwide.Research on PEMFC has always related to its performance,life expectancy and costs currently.The gas-liquid two-phase flow inside the fuel cell serves an important factor that affects the performance of the fuel cell.The mathematical model of multiphase,multi-dimensional and multi-physics of PEMFC single channel is developed to study the flow of the fluid in the fuel cell,the diffusion of the species in the microstructure of the porous electrode,the electrochemical reaction and the transmission mechanism of water phase change.The effect of operating parameters on the performance of fuel cell was analyzed and changing the geometry of flow field plate could optimize the fuel cell.Secondly,the existing forms of water in the PEMFC under different environments were explored.The removal of residual liquid water was discussed after the shutdown of the proton exchange membrane fuel cell at low temperature.Finally,theoretical analysis and numerical simulation is provided to assist cold start of the PEMFC in low temperature environment.The specific research results are as follows:(1)The numerical simulation of three-dimensional PEMFC is provided to analyze the effect of the humidity of reaction gas,operating pressure,operating temperature and other parameters on the performance of the fuel cell.The results of numerical simulation show that:Increasing the anode gas relative humidity can decrease the proton transfer resistance;When the operating temperature is lower than the critical temperature,increasing the operating temperature increases the catalyst activity and decreases the liquid water saturation in the cathode side Increasing the operating pressure can improve the rate of diffusion of reactant gases.Meanwhile,it can reduce the phase change of the water vapor.(2)The internal residual water needs to be purged after shutdown in low temperature for PEMFC to prevent residual liquid water phase change ice doing harm to the fuel cell structure or the next start failed.The fuel cell is purged by dry nitrogen for that the water content in PEMFC is between 3 and 5.It is the prerequisite for the successful start in the next time.(3)The use of liquid water and nitrogen circulation assisted pre-heating cold start can significantly decrease preheating time of fuel cell in order to avoid that the starting failure can do damage to the components of fuel cell when the PEMFC is started in low temperature.The preheating time of the fuel cell is 8.55 seconds whose cathode and anode adopts a countercurrent mode when the temperature of the fuel cell and the preheating fluid is at-30℃ and 30℃,respectively.更多还原