液相进料直接甲醇燃料电池性能的实验研究

利用美国Arbin公司燃料电池测试装置，对液相进料直接甲醇燃料电池的性能进行了实验研究。通过电流．电压曲线，研究了燃料电池工作温度和压力、阴阳极差压、甲醇和氧气流量、甲醇浓度等参数对电池性能的影响。实验结果表明：较高的电池温度可以提高电池的性能；阴阳极差压提高，电池性能降低；在甲醇浓度较低时，燃料电池工作压力、工质流量和浓度的增加均使燃料电池性能有不同程度的提高。图8参7     

燃料电池发展现状与应用前景

介绍了各种类型燃料电池（碱性燃料电池,熔融碳酸盐燃料电池,固体氧化物燃料电池,磷酸燃料电池及质子交换膜燃料电池）的技术进展,电池性能及其特点。其中着重介绍了当今国际上应用较广泛,技术较为成熟的磷酸燃料电池和质子交换膜燃料电池。对燃料电池的应用前景进行探讨,并对我国的燃料电池研究提出了一些建议。     

氢能发电技术的研究(Ⅰ)--铂碳复合电极材料对离子交换膜燃料电池放电性能的影响

离子交换膜燃料电池是氢能应用开发的重要研究领域.研究了离子交换膜燃料电池用的铂碳复合电极制备工艺和碳材料的选择对燃料电池电化学性能的影响.研究结果表明,铂碳复合电极的制备工艺对燃料电池放电性能有重要影响,采用刷涂法和物化法制备的铂碳复合电极所组装的燃料电池具有较好的电化学性能.研究结果还发现,复合电极中碳材料的微观结构也是影响燃料电池电化学性能的重要因素,碳材料的比表面积越大,燃料电池的放电性能就越好.     

PEM燃料电池气体扩散层液滴运动的可视化实验研究

扩散层作为质子交换膜燃料电池的一个重要组成部分,对电池性能有着极大的影响.将碳纸扩散层从电池单体中独立出来,针对液态水在碳纸多孔介质中的传输进行了可视化的实验研究,同时将三种流场板对排水性能的影响进行了比较.实验结果表明:碳纸的平均孔径对液态水穿透有着重要影响;蛇型流道更有利于液态水从电池中排出.     

氢能发电技术的研究（Ⅰ）——铂碳复合电极材料对离子交换膜燃料电 …

离子交换膜燃料电池是氢能应用开发的重要研究领域。研究了离子交换膜燃料电池用的铂碳复合电极制备工艺和碳材料的选择对燃料电化学性能的影响。研究结果表明,铂碳复合电极的制备工艺对燃料电池放电性能有重要影响,采用刷涂法和物化法制备的铂碳复合电极所组装的燃料电池具有较好的电化学性能。研究结果还发现,复合电极中碳材料的微观结构也是影响燃料电池化学性能的重要因素,碳材料的比表面积越大,燃料电池的放电性能就越好。     

重力对PEM燃料电池性能的影响

水对质子交换膜(PEM)燃料电池的性能有极其重要的影响,良好的水管理是PEM燃料电池保持高性能的必要条件.通过试验,观察了在重力作用下液态水对PEM燃料电池性能及其内部传质的影响,分析了PEM燃料电池单体电极的不同摆放位置对其性能的影响.试验结果发现:在电流密度较小时,重力对PEM燃料电池性能的影响不明显,电流密度较大时,重力对PEM燃料电池性能的影响比较明显.试验结果对优化PEM燃料电池的结构和水管理有一定的参考价值.     

扩散层孔隙率对PEMFC性能影响的模拟研究

为了研究扩散层孔隙率对质子交换膜燃料电池(PEMFC)性能的影响,采用COMSOL软件,通过数值模拟得出气体扩散层不同孔隙率(0.2,0.4,0.6和0.8)时,单直通道和具有楔形肋片(长1 mm,高1.5 mm,宽2 mm)的PEMFC性能曲线、阴极氧气质量分数分布和水质量分数分布。结果表明:扩散层孔隙率对燃料电池性能具有较大影响,随着扩散层孔隙率从0.2增大到0.8,PEMFC的电流密度逐渐增加,最大可达847 mA/cm~2;相对于单直通道,增加孔隙率比添加楔形肋片更利于提升电池性能;在孔隙率为0.6和0.8时,氧气更易扩散到反应区,排水效果更好。     

基于肋片强化散热的相变光伏电池性能研究

光伏电池的光电转化效率随着自身温度的升高而降低。采用相变材料冷却光伏电池是一种提高光电转化效率的有效手段。文章设计了一种基于肋片的相变光伏电池模型,并通过数值模拟分析了相变材料、肋片对光伏电池的冷却效果,肋片对相变光伏电池发电性能的影响,相变材料的用量对光伏电池温度的影响,以及当相变材料用量一定时,肋片的间距、厚度以及基板的厚度对光伏电池温度的影响。研究结果表明,相变材料和肋片的使用,均能够降低光伏电池的温度并提高光伏电池的发电性能。     

磁检测与磁效应在质子交换膜燃料电池中的应用研究

质子交换膜燃料电池(Proton exchange membrane fuel cell)是目前热门的清洁能源之一。通过磁检测和磁效应对电池反应的影响,提升电池性能及保持电池的稳定性以延长电池的使用寿命。对质子交换膜燃料电池的组成、工作原理进行阐述;对磁检测在质子交换膜燃料电池中的应用、磁效应在质子交换膜燃料电池中应用的机理及实际应用进行综述,对研究结果进行总结。     

均匀磁场对质子交换膜燃料电池工作性能影响研究

通过在质子交换膜燃料电池加载不同方向、不同强度的均匀磁场,研究均匀磁场对质子交换膜燃料电池工作性能的影响。研究发现,在燃料电池两侧加载不同方向、不同强度的均匀磁场,可以不同程度提升质子交换膜燃料电池的工作性能。文章对比了磁场方向与质子交换膜燃料电池双极板两侧平行及垂直时的工作性能,垂直磁场下的电池输出功率和工作电流提升幅度最大。当质子交换膜燃料电池分别置于不同强度(270,440,530 m T)的均匀磁场时,磁场下的电池输出功率与不加载磁场时有所增大,并且随着外加均匀磁场的增大,电池的输出功率也随之提高。     

Three-dimensional numerical study on cell performance and transport phenomena of PEM fuel cells with conventional flow fields

In this paper, a three-dimensional numerical model of the proton exchange membrane fuel cells (PEMFCs) with conventional flow field designs (parallel flow field, Z-type flow field, and serpentine flow field) has been established to investigate the performance and transport phenomena in the PEMFCs. The influences of the flow field designs on the fuel utilization, the water removal, and the cell performance of the PEMFC are studied. The distributions of velocity, oxygen mass fraction, current density, liquid water, and pressure with the convention flow fields are presented. For the conventional flow fields, the cell performance can be enhanced by adding the corner number, increasing the flow channel length, and decreasing the flow channel number. The cell performance of the serpentine flow field is the best, followed by the Z-type flow field and then the parallel flow field.     

Numerical investigation of PEM electrolysis cell with the new interdigitated-jet hole flow field

The flow field structure has important influences on the mass and heat transfer and the distribution uniformity in the proton exchange membrane electrolysis cell (PEMEC). In this paper, the application and operation modes and the structural parameters of the new interdigitated-jet hole flow field (JHFF) are explored, to guide the processing of the JHFF and provide references for experimental testing. A three-dimensional and two-phase model is established to simulate the effect of JHFF on the performance of PEMEC. The results demonstrate that compared with the application of JHFF only on the anode side, the application of JHFF on both sides of the anode and cathode can increase the temperature distribution uniformity and polarization performance by 41.78% and 16.25%, respectively. By increasing the number of inlet flow channels and using the counter-flow water supply mode, the temperature distribution can be more uniform. The lower the height of jet holes, the better the normal mass transfer and polarization performance, while the worse the temperature distribution uniformity. Reducing the diameter of the inlet jet holes can improve the normal mass transfer performance in the porous electrode. Synthetically, the hole height of 0.2 mm and the hole diameter of 0.4 mm are recommended. The findings provide theoretical guidance for the practical application of JHFF in PEMEC so that the positive role of JHFF in improving electrolysis performance can be fully realized.     

Unsteady three-dimensional numerical study of mass transfer in PEM fuel cell with spiral flow field

Bipolar plate design and its flow field shape have an important effect on the fuel cell performance. In this work, a FORTRAN program has been developed to investigate the effects of the channel width, the number of turns of the spiral channel and the flow direction on the reactants consumption in a proton exchange membrane fuel cell (PEMFC) with a spiral flow field design. The governing equations are discretized using the finite volume method in cylindrical coordinates. The results show that the channel-rib width ratio influences the cell performance; the higher ratio, the more important contact area between the channel and the GDL, the more reactants quantity seeped to the GDL and more uniform reactants distribution is. The increasing the spiral channel turns number improves the reactants distribution uniformity. The channel spiral shape engenders a centrifugal force which enhances the cell performances in the case when the reactants are injected from the external side of the spiral channel and ejected from its internal one.     

Influence of sloping baffle plates on the mass transport and performance of PEMFC

Sloping baffle plates are installed numerically in the flow channel of proton exchange membrane fuel cell (PEMFC) to promote the mass transport in the porous electrode and the fuel cell performance. The sloping angle of baffle plate on the mass transport and performance of PEMFC are investigated and optimized. The numerical results show that the sloping angle of baffle plate influences the velocity distribution, flow resistance in the flow channel, and the intensity of mass transport between the channel and porous electrode. Larger sloping angle increases the velocity in the vertical direction which brings stronger squeeze effect between the channel and porous electrode, but it also reduces the squeeze area and increases the flow resistance. An optimization for the sloping angle of baffle plate is carried out. The baffle plate with the sloping angle of 45° shows the best performance in PEMFC net power considering the pumping power caused by the pressure loss. The effect of the baffle plate number is also investigated and optimized. The fuel cell current density increases with the baffle plate number, but the increment rate is decreased. The pumping power increases almost linearly with the baffle plate number. The PEMFC with six sloping baffle plates installed in the channel is found to be optimal in terms of the net power.     

Influence of secondary hole injection angle on enhancement of film cooling effectiveness with horn-shaped or cylindrical primary holes

Abstract

Film cooling with primary and secondary hole injection is numerically investigated. Effects of primary hole shape and secondary hole injection angle are documented. Each primary hole, either cylindrical or laterally diffused, has two secondary, cylindrical holes located symmetrically about it. Adding secondary holes improves cooling performance. Five cases of different secondary hole injection configuration are analyzed. With a cylindrical primary hole, increasing secondary hole inclination angle provides better cooling; outwardly inclining the secondary holes shows continued improvement. With horn-shaped primary holes, smaller secondary hole inclination angles provide higher cooling at lower blowing ratios; larger secondary hole inclination angles provide higher cooling at higher blowing ratios, and compound-angle secondary hole injection shows no improvement over parallel hole injection.     

不同型式流场的PEMFC内部传质分析

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。     

Three-dimensional multi-phase numerical study for the effect of coolant flow field designs on water and thermal management for the large-scale PEMFCs

The multi-phase numerical study is performed for the large-scale proton exchange membrane fuel cells (PEMFCs) regarding coolant flow field design. In this study, three coolant flow fields were designed to explore the effect of different temperature distributions on the water management of the PEMFCs. The numerical results show that increasing the temperature gradient along the gas flow direction and improving the temperature uniformity perpendicular to the gas flow direction enhances PEMFC performance and makes the liquid water distribution in the gas diffusion layers more reasonable. The co-flow for the cathode gas stream and the coolant flow is beneficial to raise the temperature along the cathode gas flow direction and reduce the risk of flooding near the cathode outlet. Then, it is noted that the coolant flow field design is not necessary to keep the temperature absolutely uniform for the PEMFCs. Although increasing the coolant volume flow rate will reduce the IUT, it dramatically increases the risk of flooding near the cathode outlet. Therefore, the moderate volume flow rate is preferred. Finally, the effect of the coolant manifold on the volume flow rate uniformity in the coolant channels is investigated, and it is found that reducing the number of coolant channels is the best strategy to improve volume flow rate uniformity and thermal management performance.     

Influence of shaped injection holes on turbine blade leading edge film cooling

To improve the film cooling performance by shaped injection holes for the turbine blade leading edge region, we have investigated the flow characteristics of the turbine blade leading edge film cooling using five different cylindrical body models with various injection holes, which are a baseline cylindrical hole, two laidback (spanwise-diffused) holes, and two tear-drop shaped (spanwise- and streamwise-diffused) holes, respectively. Mainstream Reynolds number based on the cylinder diameter was 7.1 × 10⁴ and the mainstream turbulence intensities were about 0.2%. The effect of injectant flow rates was studied for various blowing ratios of 0.7, 1.0, 1.3 and 1.7, respectively. The density ratio in the present study is nominally equal to one. Detailed temperature distributions of the cylindrical body surfaces are visualized by means of an infrared thermography (IRT). Results show that the conventional cylindrical holes have poor film cooling performance compared to the shaped holes. Particularly, it can be concluded that the laidback hole (Shape D) provides better film cooling performance than the other holes and the broader region of high effectiveness is formed with fairly uniform distribution.     

Experimental investigation on the leading edge film cooling of cylindrical and laid-back holes with different hole pitches

Experimental investigation has been performed to study the film cooling performances of cylindrical holes and laid-back holes on the turbine blade leading edge. Four test models are measured for four blowing ratios to investigate the influences of film hole shape and hole pitch on the film cooling performances Film cooling effectiveness and heat transfer coefficient have been obtained using a transient heat transfer measurement technique with double thermochromic liquid crystals. As the blowing ratio increases, the trajectory of jets deviates to the spanwise direction and lifts off gradually. However, more area can benefit from the film protection under large blowing ratio, while the is also higher. The basic distribution features of heat transfer coefficients are similar for all the four models. Heat transfer coefficient in the region where the jet core flows through is relatively lower, while in the jet edge region is relatively higher. For the models with small hole pitch, the laid-back holes only give better film coverage performance than the cylindrical holes under large blowing ratio. For the models with large hole pitch, the advantage of laid-back holes in film cooling effectiveness is more obvious in the upstream region relative to the cylindrical holes. For the cylindrical hole model and the laid-back hole model with the same hole pitch, heat transfer coefficients are nearly the same with each other under the same blowing ratios. Compared with the models with large hole pitch, the laterally averaged film cooling effectiveness and heat transfer coefficient are larger for the models with small hole pitch because of larger proportion of film covering area and strong heat transfer region.     

Hydrophobic PTFE-coated serpentine flow fields with ladder-structure for fuel cell application

A proton exchange membrane's conductivity increases with increasing water content. However, water on the electrode surface inhibits the inlet of oxidant/fuel, resulting in lower performance of the proton exchange membrane fuel cell (PEMFC). Therefore, water management is a critical issue that needs to be addressed in low-temperature PEMFCs. Two strategies used to manage water are the embedding of hydrophobic materials in the electrode (catalyst or gas diffusion layer), and controlling the fuel/oxidant flow rate. In this study, ladder-structure flow fields were manufactured with hydrophobic PTFE materials coated on different ladders. These were used to investigate the effect of oxidant flow rate and oxidant humidity on PEMFC performance and dynamic variation. We have found that using a flow field with hydrophobic PTFE coated on the second ladder (from the GDL) results in the greatest improvement in performance and durability.