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针对质子交换膜燃料电池(PEMFC)水管理开展了研究,建立了一维非等温两相流解析模型,研究了不同电流密度、微孔层接触角和不同加湿方案对电池内部水分布和温度分布的影响,提出了更好的进气加湿方案。结果表明:电流密度增大会导致阳极拖干、阴极水淹加剧,导致电池各部分温度上升。因各层材料亲水性不同,在交界面处能观察到液态水阶跃现象。增大微孔层接触角促进阴极液态水反扩散到阳极,一定程度上缓解阳极变干,但过大的接触角可能导致阴极水淹加剧。通过采取"阳极充分加湿、阴极低加湿"的进气加湿方案可以有效提高电池性能,并且能在一定程度改善电池内部受热,提高电池使用寿命。 相似文献
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为了同时解决燃料电池水管理中的干涸(dehydration)和水淹(flooding)问题,提出了一种主副流道分流式的阴极进气加湿方式,并用数值模拟分析了主副流道合流节点位置变化对燃料电池性能的影响,同时与应用非分流式进气加湿方式的燃料电池性能进行了对比。结果表明,分流式阴极进气方式可以同时降低流道内的干涸和水淹程度,从而提高电池性能;当入口处空气摩尔流量固定时,随着阴极流道上主副流道合流节点沿气体流动方向移动,电池输出电压先上升,达到最大值后,逐渐下降。 相似文献
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通过对阴极和阳极气体扩散电极(GDE)采用不同厚度的碳纸、不同PEFE载量等方法研究了非对称气体扩散电极对空冷自增湿燃料电池性能的影响。通过实验得出:增大阳极扩散层厚度、减小阴极扩散层厚度均能提高电池性能,而且通过提高阳极疏水性,降低阴极疏水性,能够保证促进阳极保水和阴极排水,提高电池性能。得到的阳极PTFE含量60%,阴极PTFE含量20%的非对称型GDE组装的电池性能比PTFE含量40%的对称疏水GDE制备的PEMFC性能高5%,比商业的SIGRACET~(?)高9.16%。电池在50℃自增湿条件下工作的最大功率达到643.2mW·cm~(-2)。 相似文献
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《可再生能源》2016,(6)
为研究温度对质子交换膜燃料电池性能的影响,运用多物理场直接耦合分析软件COMSOL Multiphysics,对不同电池温度的四流道蛇形流场质子交换膜燃料电池进行了数值模拟。模拟得到了不同电池温度下垂直膜电极平面以及电池中心处从阳极流道到膜,再到到阴极流道的温度变化情况;还得到了电池温度为353K时,电池入口处、中心处和出口处从阳极流道到阴极流道相应位置点的温差变化。对模拟结果进行分析和比较后发现:电池内部温度的升高与电池本身的原始温度存在线性变化关系;电池入口处、中心处和出口处的温度变化趋势存在差异,且电池入口处温升最大,中心处次之,出口处温升最小;随着电池温度的升高,电池因内部反应所产生的热量减少。模拟结果对质子交换膜燃料电池的性能优化有重要意义。 相似文献
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以城市垃圾渗滤液为阳极液基质,比较以MnO_2和TiO_2为阴极催化剂时,对MFC电池性能以及渗滤液中有机污染物去除率的影响。结果表明,MnO_2和TiO_2作为阴极催化剂,可催化氧化阴极最终电子受体(O_2)、提高电子传递速率,最终提高电池性能。阴极负载MnO_2后,电池性能显著提高,稳定输出电压和最大功率密度分别增大到0.43 V和0.89 W/m~3。与未负载阴极催化剂的MFC相比,经MFC运行7 d后,渗滤液中的生物需氧量(BOD)和NH_4~+-N去除率分别提高8.1%和5.0%,达72.9%和91.6%。但由于缺少光照,阴极负载TiO_2后电池性能无明显改善,稳定输出电压仅为0.23 V,最大功率密度仅0.12 W/m~3,且渗滤液中有机污染物的BOD和NH_4~+-N去除率比负载MnO_2催化剂的MFC低8.8%和5.7%。 相似文献
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对采用不同型式流场的PEMFC进行建模,并用控制容积法对控制方程进行离散,求解得到PEMFC内部各物理量的分布以及综合水拖带系数、质子交换膜平均电导率等。分析了采用交趾型流场和常规流场时PEMFC的内部传质以及阴极性能、电池性能和膜性能,结果认为采用交趾型流场时,PEMFC阴极性能高于采用常规流场的PEMFC阴极性能,但质子交换膜的平均电导率低于采用常规流场时。在没有液态水产生时常规流场PEMFC性能高于交趾型流场PEMFC。 相似文献
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Vilasinee ThitakamolApichai Therdthianwong Supaporn Therdthianwong 《International Journal of Hydrogen Energy》2011,36(5):3614-3622
A new design of an interdigitated flow field, called as a mid-baffle interdigitated flow field, was built and tested for its effect on the performance of proton exchange membrane (PEM) fuel cells. The results were compared to the conventional interdigitated flow field. Their performances at different oxidant gas flow rates and operating pressures were also examined and compared by using both O2 and air as the cathode fuel reactants. The experimental results showed that when air was used as the cathode reactant, the cell with the mid-baffle interdigitated flow field outperformed the conventional one, giving a power output approximately 1.2-1.3 times higher depending on the air flow rates. The polarization curves of the mid-baffle interdigitated flow field showed larger limiting current densities at every air flow rate tested in this work. However, the performances of both flow fields were almost the same when the cathode reactant gas was O2. The test also demonstrated that the flow field performance could be enhanced by increasing the oxidant gas flow rate and cell operating pressure. 相似文献
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Novel water management strategies are important to the development of next generation polymer electrolyte membrane fuel cell systems (PEMFCs). Parallel and interdigitated flow fields are two common types of PEMFC designs that have benefits and draw backs depending upon operating conditions. Parallel flow fields rely predominately on diffusion to deliver reactants and remove byproduct water. Interdigitated flow fields induce convective transport, known as cross flow, through the porous gas diffusion layer (GDL) and therefore are superior at water removal beneath land areas which can lead to higher cell performance. Unfortunately, forcing flow through the GDL results in higher pumping losses as the inlet pressure for interdigitated flow fields can be up to an order of magnitude greater than that for a parallel flow field. In this study a flow field capable of switching between parallel and interdigitated configurations was designed and tested. Results show, taking into account pumping losses, that using constant stoichiometry the parallel flow field results in a higher system power under low current density operation compared to the interdigitated configuration. The interdigitated flow-field configuration was observed to have lower overvoltage at elevated current densities resulting in a higher maximum power and a higher limiting current density. An optimal system power curve was produced by switching from parallel to interdigitated configuration based on which produces a higher system power at a given current density. This design method can be easily implemented with current PEMFC technology and requires minimal hardware. Some of the consequences this design has on system components are discussed. 相似文献
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Current distributions in a proton exchange membrane fuel cell (PEMFC) with interdigitated and serpentine flow fields under various operating conditions are measured and compared. The measurement results show that current distributions in PEMFC with interdigitated flow fields are more uniform than those observed in PEMFC with serpentine flow fields at low reactant gas flow rates. Current distributions in PEMFC with interdigitated flow fields are rather uniform under any operating conditions, even with very low gas flow rates, dry gas feeding or over-humidification of reactant gases. Measurement results also show that current distributions for both interdigitated and serpentine flow fields are significantly affected by reactant gas humidification, but their characteristics are different under various humidification conditions, and the results show that interdigitated flow fields have stronger water removal capability than serpentine flow fields. The optimum reactant gas humidification temperature for interdigitated flow fields is higher than that for serpentine flow fields. The performance for interdigitated flow fields is better with over-humidification of reactant gases but it is lower when air is dry or insufficiently humidified than that for serpentine flow fields. 相似文献
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Anh Dinh Le 《Journal of power sources》2009,193(2):665-683
A new approach to numerical simulation of liquid water distribution in channels and porous media including gas diffusion layers (GDLs), catalyst layers, and the membrane of a proton exchange membrane fuel cell (PEMFC) was introduced in this study. The three-dimensional, PEMFC model with detailed thermo-electrochemistry, multi-species, and two-phase interactions. Explicit gas-liquid interface tracking was performed by using Computational Fluid Dynamics (CFD) software package FLUENT® v6.2, with its User-Defined Functions (UDF) combined with volume-of-fluid (VOF) algorithm. The liquid water transport on a PEMFC with interdigitated design was investigated. The behavior of liquid water was understood by presenting the motion of liquid water droplet in the channels and the porous media at different time instants. The numerical results show that removal of liquid water strongly depends on the magnitude of the flow field. Due to the blockage of liquid water, the gas flow is unevenly distributed, the high pressure regions takes place at the locations where water liquid appears. In addition, mass transport of the species and the current density distribution is significantly degraded by the presence of liquid water. 相似文献
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《Journal of power sources》2006,162(2):1157-1164
In this work, the influences of various operating conditions including cathode inlet gas flow rate, cathode inlet humidification temperature, cell temperature, etc. on the performance of proton exchange membrane (PEM) fuel cells with conventional flow field and interdigitated flow field are experimentally studied. Experimental results show that the cell performance is enhanced with increases in cathode inlet gas flow rate, cathode humidification temperature and cell temperature. However, as cell temperature is higher than or equal to anode humidification temperature, the cell performance is deteriorated due to failure in humidification of the cell. Comparison between interdigitated flow field and conventional flow field shows that the former provides higher cell performance and remarkably reduces fuel consumption for efficient diffusion of the fuel gas to the diffuser layer. As air is used as the cathode inlet gas, PEM fuel cell with interdigitated flow field can obtain preferable limiting current density, and the optimal power is about 1.4 times as that of the cells with conventional flow field. Rib and shoulder areas are more advantageous to electrochemical reaction in interdigitated flow field; hence a large flow field area ratio degrades the better performance area and thus the cell performance. But too small flow field area ratio also deteriorates the cell performance due to the decrease in effective reaction area. Theoretically, the flow field area has an optimum value, i.e., 50.75% in this work, providing higher performance than 66.67%. 相似文献
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《Energy Conversion and Management》2004,45(11-12):1883-1916
The internal transport mechanisms, which were acquired from the modeling results in Part I of this series, are discussed and compared for PEM fuel cells with a conventional flow field and an interdigitated flow field. The modeling results show that the oxygen concentration fraction in an interdigitated flow field is higher than that in a conventional flow field to increase the reaction rate, and the liquid water saturation in the former flow field is much less than that in the latter one at the cathode side to reduce the concentration overpotential largely. However, if the cathode inlet air in a PEM fuel cell with interdigitated flow field is not humidified, the performance of this fuel cell is inferior to that of a PEM fuel cell with conventional flow field because of a larger ohmic overpotential. As a result, the humidification is important for an interdigitated flow field to acquire a much better performance than a conventional flow field. 相似文献
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The transient response of a proton exchange membrane fuel cell (PEMFC) was measured for various cathode gas compositions and gas utilisations (fraction of supplied reactant gas which is consumed in the fuel cell reaction). For a PEMFC operated on pure hydrogen and oxygen, the cell voltage response to current steps was fast, with response times in the range 0.01–1 s, depending on the applied current. For a PEMFC supplied with air as cathode gas, an additional relaxation process related to oxygen transport caused a slower response (approximately 0.1–2 s depending on the applied current). Response curves up to approximately 0.01 s were apparently unaffected by gas composition and utilisation and were most likely dominated by capacitive discharge of the double layer and reaction with surplus oxygen residing in the cathode. The utilisation of hydrogen had only a minor effect on the response curves, while the utilisation of air severely influenced the PEMFC dynamics. Results suggested that air flow rates should be high to obtain rapid PEMFC response. 相似文献
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《Journal of power sources》2006,162(2):1130-1136
Water transport through the membrane of a PEMFC was investigated by measurement of the net drag under various feed gas humidity. Measured data were compared with computed results obtained using a two-dimensional cell model. Considering the change in the gas content related to the flow configuration, the humidity of the supply gas, reaction rates, and the mass balance of each gas species were derived at five sections along the flow channels. By solving these mass balance equations, the water transport rates and current density distribution were obtained along the flow channels for various feed gas humidity. The results for net drag computed from the model show a similar tendency, but are slightly higher than the measured values. This suggests that there is a certain resistance related to water transport at the cathode membrane interface in association with water production. The cause of this water transport resistance is discussed. 相似文献