2005 PEM fuel cell performance and its two-phase mass transport

PEM燃料电池阴极加湿对浓差极化的影响薛坤1肖金生1,2（1武汉理工大学材料复合新技术国家重点实验室，2汽车工程学院，湖北430070）摘要：运用FLUENT的PEM模块对质子交换膜燃料电池不同的加湿程度进行研究。

分析了不同的加湿程度对燃料电池性能的影响，尤其讨论了在高电流密度情况下，浓差极化对燃料电池性能的影响。

对80℃阴极气体分为100%加湿和50%加湿进行对比，结果表明,低电流密度100%加湿性能更好，在高电流密度时50%加湿性能更好。

另外分析了浓差极化区燃料电池内部液态水、氧气浓度、电流密度以及电极电势分布，表明浓差极化仅在燃料电池的部分区域发生。

采取有效的排水措施可以使100%饱和加湿获得更高的性能。

关键词：燃料电池电池性能阴极加湿浓差极化1引言质子交换膜燃料电池（PEMFC）作为一种新型的能源处理方式，具有工作温度低、无污染、无腐蚀、比功率大、启动迅速等优点, 已经成为能源领域研究的热点之一[1]。

在燃料电池内部，H+的迁移必须有液态水存在的情况下迁移，因此膜必须保持润湿，才能减小膜电阻。

上海交通大学的马捷等[2]对质子交换膜燃料电池膜内水迁移特性做了研究和同时对水管理和加湿方法做了探讨。

Chen J, Matsuura T, Hori M [3]等研究了一种在扩散层和催化层之间增加了水管理层（WML）的新型气体扩散层结构。

并对优化的气体扩散层进行模拟，预测了电极中水的分布图。

Choi K H, Park D J, Rho Y W[4]等对质子交换膜燃料电池膜内水迁移特性做了研究和同时对水管理和加湿方法做了探讨。

有效的水管理可以通过膜电极和电池结构的优化设计来实现，当不足以获得足够的含水率时，只能采用加湿技术。

质子交换膜燃料电池阴极增湿对于燃料电池性能的影响比较复杂。

阴极反应生成水，如果不能及时排出去，容易导致阴极水淹，影响氧气扩散，甚至导致反极。

本文通过建立一个双流道模型，对阳极饱和加湿，研究阴极不同的加湿程度对于燃料电池性能的影响，重点分析在大电流密度情况下，阴极加湿对于浓差极化的影响。

^jm 11】汽车工程师Automotive EngineerFOCUS 技术聚焦Automotiiv E ngineer^摘要：质子交换膜燃料电池低温冷启动被认为是影响燃料电池汽车商业化的主要因素之一。

文章根据某款燃料电池车型开发目标需求，对匹配的120 kW 大功率燃料电池在-30。

"低温启动热平衡初步分析，基于电堆外加热控制策略，经初步 匹配计算，在理想情况下需要13 min 才能启动，为拟开发目标设定提供了依据。

文章对开发大功率燃料电池乘用车具有 参考意义。

关键词:大功率燃料电池；低温冷启动；计算分析Analysis of Cold Starting Performance of High Power PEMFC used for VehicleAbstract ： Low temperature cold start of PEMFC is considered to be one of the main factors affecting the commercialization offuel cell vehicle. In this paper,according to the development target demand of a fuel cell vehicle, the preliminary analysis of the heat balance of the matched 120kw high-power fuel cell at 一30°C is conducted. Based on the heating control strategy outsidethe stack, the preliminary matching calculation shows that it takes 13 minutes to start under ideal conditions, which provides the basis for the target setting of the proposed development. This paper has reference significance for the development of high-power fuel cell passenger vehicle.Key words : High power PEMFC; Start-up at low temperature; Analysis质子交换膜燃料电池(PEMFC )相比传统内燃机, 拥有其特有优势h ,PEMFC 的高效率、高比功率、零排 放及响应快速等特性使其成为未来汽车领域最有潜力的动力源45;、车用PEMFC 在商业化进程中，冷启动困 难或启动时间过长是主要制约因素之一6目前，国内 外车型对燃料电池发动机冷启动能力进行了大量实验,国外相关车型已量产且技术相对成熟3w,国内大多从实际运行情况来看，在低温启动方面的技术称不上很好，如表1所示。

外文原文：Fuel Cells and Their ProspectsA fuel cell is an electrochemical conversion device. It produces electricity fromfuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.Fuel cells are different from electrochemical cell batteries in that they consume reactant from an external source, which must be replenished--a thermodynamically open system. By contrast batteries store electrical energy chemically and hence represent a thermodynamically closed system.Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include chlorine and chlorine dioxide.Fuel cell designA fuel cell works by catalysis, separating the component electrons and protonsof the reactant fuel, and forcing the electrons to travel though a circuit, hence converting them to electrical power. The catalyst typically comprises a platinum group metal or alloy. Another catalytic process takes the electrons back in, combining them with the protons and oxidant to form waste products (typically simple compounds like water and carbon dioxide).A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load.Voltage decreases as current increases, due to several factors:•Activation loss•Ohmic loss (voltage drop due to resistance of the cell components and interconnects)•Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage)To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn. Such a design is called a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.Proton exchange fuel cellsIn the archetypal hydrogen–oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that "polymer electrolyte membrane" and "proton exchange mechanism" result in the same acronym.)On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what is commonly referred to as multi-facilitated proton membranes (MFPM). The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water — in this example, the only waste product, either liquid or vapor.In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.The materials used in fuel cells differ by type. In a typical membrane electrode assembly (MEA), the electrode–bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.Oxygen ion exchange fuel cellsIn a solid oxide fuel cell design, the anode and cathode are separated by an electrolyte that is conductive to oxygen ions but non-conductive to electrons. The electrolyte is typically made from zirconia doped with yttria.On the cathode side, oxygen catalytically reacts with a supply of electrons to become oxygen ions, which diffuse through the electrolyte to the anode side. On the anode side, the oxygen ions react with hydrogen to form water and free electrons. A load connected externally between the anode and cathode completes the electrical circuit.Fuel cell design issuesCostsIn 2002, typical cells had a catalyst content of US$1000 per-kilowatt of electric power output. In 2008 UTC Power has 400kw Fuel cells for $1,000,000 per 400kW installed costs. The goal is to reduce the cost in order to compete with current market technologies including gasoline internal combustion engines. Many companies are working on techniques to reduce cost in a variety of ways including reducing the amount of platinum needed in each individual cell. Ballard Power Systems have experiments with a catalyst enhanced with carbon silk which allows a 30% reduction (1 mg/cm2 to 0.7 mg/cm2) in platinum usage without reduction in performance.The production costs of the PEM (proton exchange membrane). The Nafion membrane currently costs €400/m². In 2005 Ballard Power Systems announced that its fuel cells will use Solupor, a porous polyethylene film patented by DSM.Water and air management (in PEMFC). In this type of fuel cell, the membrane must be hydrated, requiring water to be evaporated at precisely the same rate that it is produced. If water is evaporated too quickly, the membrane dries, resistance across it increases, and eventually it will crack, creating a gas "short circuit" where hydrogen and oxygen combine directly, generating heat that will damage the fuel cell. If the water is evaporated too slowly, the electrodes will flood, preventing the reactants from reaching the catalyst and stopping the reaction. Methods to manage water in cells are being developed like electroosmotic pumps focusing on flow control. Just as in a combustion engine, a steady ratio between the reactant and oxygen is necessary to keep the fuel cell operating efficiently.Temperature managementThe same temperature must be maintained throughout the cell in order to prevent destruction of the cell through thermal loading. This is particularly challenging as the 2H2 + O2 =2H2O reaction is highly exothermic, so a large quantity of heat is generated within the fuel cell.Durability, service life, and special requirements for some type of cells Stationary fuel cell applications typically require more than 40,000 hours of reliable operation at a temperature of -35°C to40°C, while automotive fuel cells require a 5,000 hour lifespan (the equivalent of 150,000 miles) under extreme temperatures. Automotive engines must also be able to start reliably at -30 °C and have a high power to volume ratio (typically 2.5 kW per liter).HistoryThe principle of the fuel cell was discovered by German scientist Christian Friedrich Schönbein in 1838 and published in one of the scientific magazines of thetime. Based on this work, the first fuel cell was demonstrated by Welsh scientist Sir William Robert Grove in the February 1839 edition of the Philosophical Magazine and Journal of Science, and later sketched, in 1842, in the same journal. The fuel cell he made used similar materials to today's phosphoric-acid fuel cell.In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the“Grubb-Niedrach fuel cell”. GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. This was the first commercial use of a fuel cell. It wasn't until 1959 that British engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers which was demonstrated across the US at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants. Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering a welding machine. In the 1960s, Pratt and Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks).United Technologies Corporation's UTC Power subsidiary was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings. UTC Power continues to market this fuel cell as the PureCell 200, a 200 kW system (although soon to be replaced by a 400 kW version, expected for sale in late 2009). UTC Power continues to be the sole supplier of fuel cells to NASA for use in space vehicles, having supplied the Apollo missions, and currently the Space Shuttle program, and is developing fuel cells for automobiles, buses, and cell phone towers; the company has demonstrated the first fuel cell capable of starting under freezing conditions with its proton exchange membrane automotive fuel cell.Fuel cell efficiencyThe efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current, which increases the losses in the fuel cell. As a general rule, the more power (current) drawn, the lower the efficiency.Most losses manifest themselves as a voltage drop in the cell, so the efficiency of a cell is almost proportional to its voltage. For this reason, it is common to show graphs of voltage versus current (so-called polarization curves) for fuel cells. A typical cell running at 0.7 V has an efficiency of about 50%, meaning that 50% of the energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. (Depending on the fuel cell system design, some fuel might leave the system unreacted, constituting an additional loss.)For a hydrogen cell operating at standard conditions with no reactant leaks, the efficiency is equal to the cell voltage divided by 1.48 V, based on the enthalpy, or heating value, of the reaction. For the same cell, the second law efficiency is equal to cell voltage divided by 1.23 V. (This voltage varies with fuel used, and quality and temperature of the cell.) The difference between these numbers represents the difference between the reaction's enthalpy and Gibbs free energy. This difference always appears as heat, along with any losses in electrical conversion efficiency.Fuel cells do not operate on a thermal cycle. As such, they are not constrained, as combustion engines are, in the same way by thermodynamic limits, such as Carnot cycle efficiency. At times this is misrepresented by saying that fuel cells are exempt from the laws of thermodynamics, because most people think of thermodynamics in terms of combustion processes (enthalpy of formation). The laws of thermodynamics also hold for chemical processes (Gibbs free energy) like fuel cells, but the maximum theoretical efficiency is higher (83% efficient at 298K) than the Otto cycle thermal efficiency (60% for compression ratio of 10 and specific heat ratio of 1.4). Comparing limits imposed by thermodynamics is not a good predictor of practically achievable efficiencies. Also, if propulsion is the goal, electrical output of the fuel cell has to still be converted into mechanical power with the corresponding inefficiency. In reference to the exemption claim, the correct claim is that the "limitations imposed by the second law of thermodynamics on the operation of fuel cells are much less severe than the limitations imposed on conventional energy conversion systems". Consequently, they can have very high efficiencies in converting chemical energy to electrical energy, especially when they are operated at low power density, and using pure hydrogen and oxygen as reactants.In practice, for a fuel cell operating on air (rather than bottled oxygen), losses due to the air supply system must also be taken into account. This refers to the pressurization of the air and dehumidifying it. This reduces the efficiency significantlyand brings it near to that of a compression ignition engine. Furthermore fuel cell efficiency decreases as load increases.The tank-to-wheel efficiency of a fuel cell vehicle is about 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC (New European Driving Cycle) is used as test procedure. The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a car with fuel stack claiming a 60% tank-to-wheel efficiency.Fuel cells cannot store energy like a battery, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power, they are combined with electrolyzers and storage systems to form an energy storage system. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency) is between 30 and 50%, depending on conditions. While a much cheaper lead-acid battery might return about 90%, the electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore better suited for long-term storage.中文译文：燃料电池及其发展前景燃料电池是一种电化学转换装置。

帮助| 搜索| 注册| 登陆| 排行榜| 发帖统计»傲雪论坛»『Fluent专版』打印话题寄给朋友作者我的FLUENT里面怎么没有ADDON选项呢. [精华]ggbaby版主发帖: 843 积分: 11 雪币: 286于2005-06-24 11:38实在是用的同一个东西.别人的有,在DEFINE->MODELS->ADDON. 我的就是没有....chenstar盼望2008发帖: 3128积分: 2雪币: 949来自:温暖的雪地于2005-06-24 12:05搞不清楚，按说addon都必须有特别的license。

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ddydai发帖: 306积分: 1雪币: 72于2005-06-24 13:54是这些吗：/define/models/acoustics//define/models> addFLUENT Addon Modules:1. MHD Model2. Fiber Model3. PEM Fuel Cell Model4. SOFC Fuel Cell ModelEnter Module Number: [1] 4Fast-loading "C:\Fluent.Inc\addons\sofc1.1\lib\addon.bin" Done.Opening library "C:\Fluent.Inc\addons\sofc1.1"...Library "C:\Fluent.Inc\addons\sofc1.1\ntx86\2d\libudf.dll" opened sourceadjust_functiondiffusivityE_ConductivityWARNING!C:\Fluent.Inc\addons\sofc1.1tx86\2d\libudf.dll contains UDFUtilityFunctions.Only one set of UDFUtilityFunctions is supported.This is already in use by mhd2.0.The following UDFUtilityFunctions functions will be ignored:fl_uds_solid_solve_pfl_uds_compute_coeffsfl_uds_post_solve_updateDone.Addon Module: sofc1.1...loaded!ddydai发帖: 306 积分: 1 雪币: 72于2005-06-24 13:57来个图：有啊：此主题相关图片如下：pvxd发帖: 52积分: 1雪币: 51于2005-06-24 18:32楼上的有license吗？addon调进去以后能算吗？feizao发帖: 29 积分: 0 雪币: 29于2005-06-24 21:42晕，俺的也没有yuhuiphd海纳百川有容乃大发帖: 339积分: 1雪币: 147于2005-06-25 00:06用console命令就可以了。

专利名称：Fuel cell and fuel cell 发明人：西原 雅人,松上 和人申请号：JP2003405710申请日：20031204公开号：JP4412985B2公开日：20100210专利内容由知识产权出版社提供摘要：PROBLEM TO BE SOLVED: To provide a fuel battery cell and a fuel battery in which power generating performance can be exerted sufficiently.SOLUTION: This is the fuel battery cell 30 in which on one side main face of a conductive support substrate 13, a fuel side electrode 7, a solid electrolyte 9, and an oxygen side electrode 11 are sequentially installed, in which an interconnector 12 is installed at the other side, and which has a fuel gas passage 15 in the interior. When the length of the gas passage forming direction of one side main face of the conductive support substrate 13 is made to be a (mm), the width of the direction perpendicular to it is made to be b (mm), the value of a×b satisfies 3,000 to 5,250.COPYRIGHT: (C)2005,JPO&NCIPI申请人：京セラ株式会社地址：京都府京都市伏見区竹田鳥羽殿町６番地国籍：JP更多信息请下载全文后查看。

资料范本本资料为word版本，可以直接编辑和打印，感谢您的下载质子交换膜燃料电池论文地点：__________________时间：__________________说明：本资料适用于约定双方经过谈判，协商而共同承认，共同遵守的责任与义务，仅供参考，文档可直接下载或修改，不需要的部分可直接删除，使用时请详细阅读内容质子交换膜燃料电池摘要能源和环境是全人类面临的重要课题，考虑可持续发展的要求，在电池领域质子交换膜燃料电池（PEMFC）技术正引起能源工作者的极大关注。

本论文简单介绍了一下质子交换膜燃料电池的组成、特点及其工作原理。

详细的从质子交换膜燃料电池的质子交换膜的材料、电催化剂的种类、双极板材料及其贮氢技术的困难方面论述了质子交换膜燃料电池的关键技术；同时从质子交换膜燃料电池的研发现状及其在电动车动力源、家庭电源、分散站和军事领域的应用做以介绍。

关键词：质子交换膜燃料电池；质子交换膜；双极板；电催化剂ABSTRACTEnergy and environment is the mankind faces an important subject，considering the requirements of sustainable development，the Proton Exchange Membrane Fuel Cell（PEMFC）technology is attracting the attention of energy workers. In this thesis，the introduction of proton exchange membrane fuel cell composition，working principle，domestic and international situation and its application prospects. In this thesis，a brief proton exchange membrane fuel cell composition，characteristics，and how it works and its Problems and prospects in the industrial development are outlined. Detail from the proton exchange membrane fuel cell proton exchange membrane materials，the type of electro-catalyst，the bipolar plate materials and the difficulties of hydrogen storage technologies discussed proton exchange membrane fuel cell，the key technologies； At the same time，from the proton exchange membrane fuel cell R & D Status and its power source in electric vehicles，household power，decentralized stations and military fields，the application to introduce.Key Words：Proton exchange membrane fuel cell;Proton exchange membrane; Bipolarplate; Electro catalyst引言能源是人类赖以生存发展的重要物质基础，也是国民经济发展的重要命脉，因而对人类及人类社会发展具有十分重要的意义。

化工进展Chemical Industry and Engineering Progress2024 年第 43 卷第 4 期具有烷基磺酸侧链的凝胶型聚苯并咪唑质子交换膜的制备与表征朱泰忠1，张良1，黄泽权1，罗伶萍1，黄菲1，薛立新1，2（1 浙江工业大学化工学院膜分离与水科学技术中心，浙江 杭州 310014；2温州大学化学与材料工程学院，浙江 温州 325035）摘要：磷酸（PA ）掺杂聚苯并咪唑（PBI ）以其优异的热化学稳定性和高玻璃化转变温度成为高温质子交换膜燃料电池（HT-PEMFCs ）的首选材料。

然而，由于低温下磷酸较弱的解离度和传递速率，导致膜的质子传导性能不佳，电池冷启动困难。

因此，研发可在宽温湿度范围内高效运行的高温质子交换膜成为当前挑战。

特别是拓宽其低温运行窗口、实现冷启动对这类质子交换膜燃料电池在新能源汽车领域的实际应用具有重要意义。

本文通过多聚磷酸溶胶凝胶工艺与内酯开环反应设计并合成了一系列磷酸掺杂的具有柔性烷基磺酸侧链的凝胶型聚苯并咪唑质子交换膜。

重点探究了烷基磺酸的引入以及侧链长度对磷酸掺杂水平、不同温湿度下的质子传导率及稳定性的影响规律。

研究结果表明，所制备的质子交换膜具有凝胶型自组装片层堆叠的多孔结构，有利于吸收大量磷酸并提供质子快速传输通道。

其中，PA/PS-PBI 展现出了在宽温域范围内均优于目前所报道的其他工作的质子传导性能。

特别是常温下，其质子传导率从原膜的0.0286S/cm 提升至0.0694S/cm 。

80℃下，其质子传导率从原膜的0.1117S/cm 提升至0.1619S/cm 。

200℃下，其质子传导率从原膜的0.2609S/cm 提升至0.3578S/cm 。

此外，该膜在80℃和0%相对湿度（RH ）条件下仍可具有与Nafion 膜在100%RH 时相当的质子传导率，为打破质子交换膜经典定义、实现宽温域（25~240℃）运行提供新的方案。

M-N-C阴极催化剂的制备及其在微生物燃料电池中的应用白立俊;王许云;何海波;郭庆杰【摘要】以聚苯胺和硝酸盐为前驱体,采用热处理法制备了M-N-C (M=Fe,Co)材料,并将其作为厌氧流化床微生物燃料电池(AFBMFC)阴极催化剂.通过X射线衍射(XRD)、红外光谱(FTIR)、扫描电子显微镜(SEM)对催化剂进行晶型结构和表面形貌的表征.采用循环伏安法(Cv)对催化剂的电化学性能进行考察,并应用于AFBMFC,考察了其对电池产电性能的影响.结果表明,使用Fe-N-C催化剂的微生物燃料电池稳定运行时,开路电压达到636.0 mV,功率密度达到166.82 mW ·m-2,比使用Pt/C 催化剂的微生物燃料电池的功率密度提高10％.表明Fe-N-C催化剂用做微生物燃料电池阴极催化剂具有潜在的应用前景.【期刊名称】《化工学报》【年(卷),期】2014(065)004【总页数】6页(P1267-1272)【关键词】燃料电池;空气阴极;催化剂;产电特性;功率密度;制备【作者】白立俊;王许云;何海波;郭庆杰【作者单位】青岛科技大学化工学院,清洁化工过程山东省高校重点实验室,山东青岛266042;青岛科技大学化工学院,清洁化工过程山东省高校重点实验室,山东青岛266042;青岛科技大学化工学院,清洁化工过程山东省高校重点实验室,山东青岛266042;青岛科技大学化工学院,清洁化工过程山东省高校重点实验室,山东青岛266042【正文语种】中文【中图分类】O646;X382;X703微生物燃料电池（MFC）是以微生物为催化剂，将化学能转化为电能的绿色能源技术。

该技术在降解废水有机质的同时产生电能，具有原料广泛、生物相容性好的特点[1]。

对于单室微生物燃料电池阴极氧的还原，铂碳催化剂[2]和基于铂的合金催化剂[3-4]一直被认为是良好的电催化剂。

然而贵金属铂价格昂贵不可再生，并且 Pt/C催化剂极易中毒，限制了其规模化应用。

内容摘要矮子交换黢燃瓣堍遗蹙翁毫效、嵩栽餐密囊、零撵敖、低温囊蕊等特点在阉定电站和移动电源等方颇具诲广泛的废用。

质子交换膜憋燃料电池的熬键部件之一，爨有传递凄予耪分褰勰强瓣摄气舔靛双霪翡襞。

鏊蔻，只寿垒氟袋羧覆子交歉羧应１鬻于燃瓣电漶，僵荬滚本占濑辩电注套缀袋罄静之蓄，建季率懿蒺予交涣貘潦辩魄滟商品化的主要因素之～。

本工作的隧的怒研究全氟质予交换臌（Ｎａｔｉｏｎ，Ａｃｉｐｌｅｘ，Ｆｉｅｍｉｏｎ窝上海簇）戆缝稳秘桎笺，并搛污结拣与瞧戆粒密秘关系，对改避甏蠢帮秘裁囊兹豢徐袋子交欹貘瑟帮指导褴意义。

主要磅究缨聚壤撬熬下１．研究发现在相对离的电流密度范围，较厚的质子交换膜燃料电池出现的物质传递控裁主簧是安予质予糨黯长疑簿扩激簧递投匏引筵熬。

纠正了文献审试兔戴气传递控利鼹蕊煮。

２，在质子交换膝的化学组成、离予交换密量和厚度相同的情况下。

膜性能与不同垒产厂“蒙瓣媵裁蚕工艺足乎无关。

３．Ｎａｔｉｏｎ葶鲢上海矮子交歉貘燃料魄波鹣氯还嚣发艨瓣Ｔａｆｅｔ瓣攀髓着壤浮发蹬鸯羹而逐渐增加，而Ａｃｉｐｌｅｘ和Ｆｌｅｍｉｏｎ威予交换膜的Ｔａｆｅｌ斜率璺觋相反得变化趟势，显示薅氧还骧规躺鹣差雾。

４＋氯气嚣懑激辩驳醛磷究＜等漫吸憋黪线嚣巍径努露）证实了全鬣臻酸矮子交搽膜的离子簇网络模型结构，与文献中小角ｘ射线衍射结果相一数。

并且首次利爱遮耱方法获褥凄予交羧膜戆孑Ｌ经大枣分毒。

５．发瑰较游瓣Ｎａｔｉｏｎ１１２藤兵鸯不潮予弱一系戴鞍簿懿Ｎａｔｉｏｎ｛１７貘熬镞我分布，这是由于薄膜的袭顽效应引起内部微结构的变化。

这也是膜中质子传遴撩裁裁一拿主要缀毽。

哭键词：隧ｉ疯抉膜，！壹蛰仨璺氧鼍璺垦璺，质警篓！些制，ｊ蛉夺ＡｂｓｔｒａｃｔＰｒｏｔｏｎｅｘｃｈａｎｇｅｍｅｍｂｒａｎｅｆｕｅｌｃｅｌｌｓ（ＰＥＭＦＣｓ）ａｔｔｒａｃｔｍｕｃｈａｔｔｅｎｔｉｏｎｄｕｅｔｏｔｈｅｉｒｈｉｇｈｅｆｆｉｃｉｅｎｃｙ，ｈｉｇｈｐｏｗｅｒｄｅｎｓｉｔｙ，ｚｅｒｏｅｍｉｓｓｉｏｎ．１０ｗｔｅｍｐｅｒａｔｕｒｅｓｔａｒｔ—ｕｐａｓｐｏｗｅｒｓｏｕｒｃｅｓｓｕｉｔａｂｌｅｆｏｒｂｏｔｈｓｔａｔｉｏｎａｒｙａｎｄｍｏｂｉｌｅａｐｐｌｉｃａｔｉｏｎｓ．ＰｒｏｔｏｎｅｘｃｈａｎｇｅｍｅｍｂｒａｎｅｉｓｏｎｅｏｆｋｅｙｃｏｍｐｏｎｅｎｔｓｏｆＰＥＭＦＣａｎｄｈａｓｄｕａｌｆｕｎｃｔｉｏｎｏｆｐｒｏｔｏｎｃｏｎｄｕｃｔｉｏｎａｎｄｓｅｐａｒａｔｉｏｎｏｆａｎｏｄｅｃｈａｍｂｅｒｆｒｏｍｃａｔｈｏｄｅｏｎｅ．Ｓｏｆａｒ，ｏｎｌｙｐｅｒｆｌｕｏｒｉｎａｔｅｄｓｕｌｐｈｏｎｉｃａｃｉｄｉｏｎｏｍｅｒｍｅｍｂｒａｎｅｓｈａｖｅｂｅｅｎｕｓｅｄｉｎｆｕｅｌｃｅｌｌｓａｎｄｔｈｅｉｒｃｏｓｔｃｏｖｅｒｓｔｈｅｌａｒｇｅｓｔｐｒｏｐｏｒｔｉｏｎｉｎｔｈｅｖａｒｉｏｕｓｃｏｍｐｏｎｅｎｔｓｏｆｆｕｅｌｃｅｌｌｓ．Ｔｈｅｃｏｓｔｏｆｐｅｒｆｌｕｏｒｉｎａｔｅｄｍｅｍｂｒａｎｅｓｉｓｏｎｅｏｆ氇ｅｍｏｓｔｉｍｐｏｒｔａｎｔＮｃｍｒｓｆｏｒｒｅｔａｒｄｉｎｇｔｈｅｃｏｍｍｅｒｃｉａｌｉｚａｔｉｏｎｏｆＰＥＭｆｕｅｌｃｅｌｌｓＴｈｅａｉｍｏｆｔｈｉｓｗｏｒｋｉｓｔｏｉｎｖｅｓｔｉｇａｔｅｔｈｅｓｔｒｕｃｔｕｒｅａｎｄｐｅｒｆｏｒｍａｎｃｅｏｆｐｅｒｆｌｕｏｒｉｎａｔｅｄｐｒｏｔｏｎｅｘｃｈａｎｇｅｍｅｍｂｒａｎｅｓ（Ｎａｔｉｏｎ，Ａｃｉｐｌｅｘ，Ｆｌｅｍｉｏｎ，ａｎｄＳｈａｎｇｈａｉ）ａｎｄｔｏｇｉｖｅａｎｉｎｓｉｇｈｔｉｎｔｏｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｔｈｅｍｆｏｒｔｈｅｍｏｄｉｆｉｃａｔｉｏｎｏｆｐｒｅｓｅｎｔｍｅｍｂｒａｎｅｓａｎｄｔｈｅＲ＆Ｄｏｆｎｅｗｍｅｍｂｒａｎｅｓｓｕｉｔａ鞠ｅｆｏｒＰＥＭＦＣＳ．Ｓｏｍｅｏｆｏｒｉｇｉｎａｌｒｅｓｅａｒｃｈｒｅｓｕｌｔｓａｒｅｓｕｍｍａｒｉｚｅｄｉｎｔｈｅｆｏｌｌｏｗｉｎｇ１，Ｉｔｉｓｆｏｕｎｄｔｈａｔｆｏｒｔｈｉｃｋｐｒｏｔｏｎｅｘｃｈａｎｇｅｍｅｍｂｒａｎｅｓｍａｓｓ谨ａｎｓｐｏｒｔｌｉｍｉｔａｔｉｏｎｉｎｔｈｅｈｉｇｈｃｕｒｒｅｎｔｄｅｎｓｉｔｙｒａｎｇｅｉｓｍａｉｎｌｙｏｒｉｇｉｎａｔｅｄｆｒｏｍｔｈｅｌｉｍｉｔａｔｉｏｎｏｆｐｒｏｔｏｎｔｒａｎｓｐｏｒｔｄｕｅｔｏａｌｏｎｇ－ｄｉｓｔａｎｃｅｄｉｆｆｕｓｉｏｎ．２．Ｇｉｖｅｎｔｈｅｓａｌｎｅｃｈｅｍｉｃａｌｃｏｍｐｏｓｉｔｉｏｎ，ｅｑｕｉｖａｌｅｎｔｗｅｉｇｈｔ，ａｎｄｔｈｉｃｋｎｅｓｓｏｆｐｒｏｔｏｎｅｘｃｈａｎｇｅｍｅｍｂｒａｎｅｓ，ｍｅｍｂｒａｎｅｐｒｅｐａｒａｔｉｏｎｔｅｃｈｎｏｌｏｇｙｉｓｎｅａｒｌｙｉｎｄｅｐｅｎｄｅｎｔｏｆｍｅｍｂｒａｎｅｐｅｒｆｏｒｍａｎｃｅ．３＋ＴｈｅＴａｆｅｌｓｌｏｐｅｏｆＮａｔｉｏｎａｎｄＳｈａｎｇｈａｉｆａｍｉｌｙｏｆｍｅｍｂｒａｎｅｓｉｎｃｒｅａｓｅｓｗｉｔｈｉｎｃｒｅａｓｉｎｇｍｅｍｂｒａｎｅｔｈｉｃｋｎｅｓｓ，ｗｈｉｌｅｔｈｅＴａｆｅｌｓｌｏｐｅｓｏｆＡｃｉｐｌｅｘａｎｄＦｌｅｍｉｏｎｆａｍｉｌｉｅｓｏｆｍｅｍｂｍｎｅｓｔａｋｅ张ｏｐｐｏｓｉｔｅｃｈａｎｇｅ．Ｔｈｉｓｉｎｄｉｃａｔｅｓｔｈａｔｔｈｅｒｅｉｓａｄｉｆｆｅｒｅｎｃｅｉｎｏｘｙｇｅｎｒｅｄｕｃｔｉｏｎｍｅｃｈａｎｉｓｍ，４．Ｎｉｔｒｏｇｅｎａｄｓｏｒｐｔｉｏｎ—ｄｅｓｏｒｐｔｉｏｎｓｔｕｄｉｅｓｏｆｔｈｅｓｅｐｅｒｆｌｕｏｒｉｎａｔｅｄｉｏｎｏｍｅｒｍｅｍｂｒａｎｅｓｐｒｏｖｅｔｈｅｐｏｓｓｉｂｉｌｉｔｙｏｆｃｌｕｓｔｅｒ－ｎｅｔｗｏｒｋｍｏｄｅｌｏｆｐｅｒｆｌｕｏｒｉｎａｔｅｄｍｅｍｂｒａｎｅｓ，ａｎｄｔｈｅｐｏｒｅｓｉｚｅｄｉｓｔｒｉｂｕｔｉｏｎｏｆｔｈｅｍｅｍｂｒａｎｅｓｉｓｆｉｒｓｔｏｂｔａｉｎｅｄｂｙｔｈｉｓｍｅｔｈｏｄ。

FLUENT软件的多重网格并行算法及其性能余江洪1，朱宗柏1,2，肖金生1,3(1武汉理工大学材料复合新技术国家重点实验室，2现代教育技术中心，3汽车工程学院，湖北430070)摘要：FLUENT软件是目前国际上比较流行的通用CFD软件包，用于模拟从不可压缩到高度可压缩范围内的复杂流动，对大规模问题可用并行多重网格方法进行求解。

为了找出FLUENT软件的最佳解题规模和并行粒度，以期最大限度地发挥软件和硬件的效能，对FLUENT软件采用的多重网格方法和区域分裂法进行了理论分析，通过反复实验，重点讨论了在并行求解过程中，采用不同的多重网格循环方法、区域网格分裂方法、解题的规模和计算节点数对并行性能的影响。

FLUENT软件有良好的并行性能，PEM Fuel Cell模块可以进一步优化，HPCC还有很大的升级空间。

关键词：燃料电池；多重网格；区域分裂；并行计算；FLUENTFLUENT软件是一种CFD（Computational Fluid Dynamics）求解器，它可以求解各种复杂流动，包括不可压缩流动（低亚音速）、弱可压流动（跨音速）和强压缩性问题（超音速）。

1由于FLUENT软件有多种求解方法的选择，并且提供了多重网格方法来加快收敛速度，同时可以进行并行计算，因此它可以为速度范围很广的流动问题提供高效准确的最优求解方案。

本文介绍了FLUENT软件的多重网格及并行算法，并测试、分析了其并行性能。

1 FLUENT软件中的多重网格方法多重网格方法(MGM:MultiGrid Method)是一种高效的串行数值计算方法。

其基本思想是，利用粗网格上的残差校正特性消除迭代误差的低频分量（长波分量，即光滑误差），同时利用细网格上的松驰光滑特性消除迭代误差的高频部分（短波分量，即振荡误差），套迭代技术负责通过限制和插值算子连接所有网格层共同求解同一问题[1][2][3][4]。

多重网格循环可以定义为在每一个网格层面通过网格层次时在网格层面内应用的递归程序，该程序通过在当前层面完成单一网格循环来扩展到下一个粗糙网格层面。

化学计量比对PEMFC超调的影响张永生1,2詹志刚11武汉理工大学材料复合新技术国家重点实验室，武汉(430070)2 武汉理工大学能源与动力工程学院，武汉(430063)E-mail：zhang-262519@摘要：文章建立了一个三维蛇形流场燃料电池模型，计算了不同化学计量比的情况下质子交换膜燃料电池的动态特性，对超调现象从机理上进行了分析。

结果表明：在反应气体的相对湿度较高，过量系数大于1时，电流密度的超调主要受氧气浓度的影响，而氧气的浓度又受水浓度的影响；在氢气过量系数小于等于1时，电流密度的超调主要受氢气浓度的影响。

关键字：质子交换膜；燃料电池；化学计量比；超调；动态中图分类号：TK911．引言质子交换膜燃料电池运行时，操作参数的改变常常会引起电流密度的超调，国内外很多学者对超调现象进行了研究。

G.L. Hu et al.[1]利用Fluent软件模拟了蛇形流道单电池的瞬态响应，观察到了在电压变化时电流密度会出现超调现象，但并没有对引起超调现象的原因从机理上进行解释。

J. Hamelin et al.[2]通过实验测试了35个232cm2的单电池组成的10kW的PEMFC电堆系统的瞬态响应，观察到了电流、电压的超调现象，但没有对其进行解释。

P.R. Pathapati et al.[3]运用Simulink进行了仿真，发现在电流密度改变时电压会出现超调现象，认为这种现象是由阴极催化层中质子浓度的变化引起的。

Y. Wang et al.[4]还研究了电流密度改变时电压的超调现象，结果表明，这种超调现象是因为阳极催化层中水含量的动态分布引起的，阳极催化层中水含量在电流密度增加时先降低后增加，在0.3s达到最小值，与电压达到最小值的时间一致。

Y. Wang et al.[5]模拟了进气加湿的改变对电流密度的影响，观察到PEMFC在电压突然改变时电流密度会出现超调现象，认为电流密度超调的原因是膜的润湿过程滞后于阴极氧气传输。

ReviewReview and analysis of PEM fuel cell design and manufacturingViral Mehta,Joyce Smith Cooper *Department of Mechanical Engineering,University of Washington,Seattle,WA 98195,USAReceived 9September 2002;accepted 23September 2002AbstractDesign and manufacturing alternatives for Proton Exchange Membrane (PEM)fuel cells are described and analysed within the context of vehicle applications.Speci®cally,following a review of many alternatives,16polymer electrolyte membranes,2types of gas diffusion layers (GDL),8types of anode catalysts,4types of cathode catalysts and over 100bipolar plate designs are recommended for further study.This work not only reviews membrane electrode assembly manufacturing options and synthesis processes for many of the membranes and for the gas diffusion layers,but also adds to the bipolar plate fabrication options described in literature.This work is intended to facilitate material and process selection through the consideration of the variety of design and manufacturing alternatives prior to capital investment for wide-scale production.#2002Elsevier Science B.V .All rights reserved.Keywords:PEM fuel cells;Membrane electrode assembly;Bipolar plate1.IntroductionOn 9January 2002,the US Secretary of Energy Spencer Abraham and executives of Ford Motor Company,General Motor Corporation,and DaimlerChrysler announced a new cooperative automotive research partnership between the US Department of Energy and the US Council for Automotive Research (USCAR)called FreedomCAR .The partnership,which replaces the partnership for a New Generation of Vehicles program,focuses on the development of fuel cell vehicle technologies.Fuel cell vehicle technologies are those that enable mass production of affordable hydro-gen-powered fuel cell vehicles and the hydrogen-supply infrastructure to support them.Among the vehicle technol-ogy options,proton exchange membrane (PEM)fuel cells,also referred to as solid polymer fuel cells,are favored for use in automobiles ([1,2],and many others).This preference is due to the high power density,relatively quick start-up,rapid response to varying loads,and low operating tempera-tures provided by PEM fuel cells.Fig.1depicts the key components of PEM fuel cells in which the oxidative and reductive half reactions are kept separate (i.e.in which the bipolar plates to be impervious to the reactants).As shown,a single PEM cell is comprised of three types of components:a membrane±electrode assembly (MEA),two bipolar (a.k.a.¯ow ®eld or separator)plates,and two seals.In its simplest form,the MEA consists of a membrane,two dispersed catalyst layers,and two gas diffusion layers (GDL).The membrane separates the half reactions allowing protons to pass through to complete the overall reaction.The electron created on the anode side is forced to ¯ow through an external circuit thereby creating current.The GDL allows direct and uniform access of the fuel and oxidant to the catalyst layer,which stimulates each half reaction.In a fuel cell stack,each bipolar plate supports two adjacent cells.The bipolar plates typically have four functions:(1)to distribute the fuel and oxidant within the cell,(2)to facilitate water management within the cell,(3)to separate the individual cells in the stack,and (4)to carry current away from the cell.In the absence of dedicated cooling plates,the bipolar plates also facilitate heat manage-ment.Individual cells are combined into a fuel cell stack of the desired power.End plates and other hardware (bolts,springs,intake/exhaust pipes and ®ttings,etc.not shown in Fig.1)are needed to complete the stack.Previous works summarizing PEM fuel cell design alter-natives are provided by Larminie and Dicks [3],EG&G Services [2],and Gottesfeld and Zawodzinski [1].Speci®-cally,Larminie and Dicks and EG&G Services provide textbooks on emerging fuel cell technologies.Their discus-sions of PEM fuel cell design include very general descrip-tions of materials use and con®gurations,the advantages and disadvantages of each design,stack performance relation-ships related to thermodynamics,water management,oper-ating temperatures and pressures,and fuel andoxidantJournal of Power Sources 114(2003)32±53*Corresponding author.Tel.: 1-206-543-5040.E-mail address:cooperjs@ (J.S.Cooper).0378-7753/02/$±see front matter #2002Elsevier Science B.V .All rights reserved.PII:S 0378-7753(02)00542-6composition,and potential applications issues.Gottesfeld and Zawodzinski [1]provide a more research-oriented,electrochemistry-based discussion of fuel cell design when compared to these textbooks.More speci®c discussions of materials and topologies for design alternatives can be found for speci®c components,typically accompanying related research or an analysis of that component.In particular,summaries of membrane materials have been published by Glipa and Hogarth from Johnson Matthey Technology Center,UK [4]and Rikukawa and Sanui from Sophia University,Japan [5].Also,analysis of some bipolar plate materials is presented by Borup and Vanderborgh [6].Similarly,PEM fuel cell manufacturing information can be found for speci®c components,especially for novel designs.Unlike PEM fuel cell design,current literature does not include summaries of manufacturing alternatives.Also,little analysis of fabrication options for more typical designs is available.This paper,based on [7],reviews and extends existing PEM fuel cell design and manufacturing literature within the context of vehicle propulsion.We provide a comprehensive review of design and manufacturing alternatives described in literature for MEAs and bipolar plates.We also critique and broaden this set of alternatives based on a functional analysis of design,the application of process selection techniques with respect to component design features,and analyses of process inputs and outputs.2.Review and analysis of membrane electrode assembly design and manufacturingFigs.2and 3provide classi®cations of MEA material and manufacturing alternatives,described as follows.2.1.MEA designAgain,an MEA consists of a membrane,a dispersed catalyst layer,and a GDL.The membrane separates the reduction and oxidation half reactions.It allows the protons to pass through to complete the overall reaction while forcing the electrons to pass through an external circuit.The catalyst layer stimulates each half reaction.The GDL further improves the ef®ciency of the system by allowing direct and uniform access of the fuel and oxidant to the catalyst layer.Design and manufacturing alternatives for each of these three components are reviewed and analyzed as follows.2.1.1.Membrane designGottesfeld and Zawodzinski [1]suggest that per¯uoro-sulfonic acid (PFSA)is the most commonly used membrane material for PEM fuel cells.PFSA consists of three regions:(1)a polytetra¯uoroethylene (PTFE, a.k.a.DuPont's Te¯on TM )-like backbone,(2)side chains of ±O±CF 2±CF±O±CF 2±CF 2±which connect the molecular backbone to the third region,and (3)ion clusters consisting of sulfonic acid ions [8].When the membrane becomes hydrated,the hydro-gen ions in the third region become mobile by bonding to the water molecules and moving between sulfonic acid sites.There are two advantages to the use of PFSA membranes in PEM fuel cells.First,because the structure is based on PTFE backbone,PFSA membranes are relatively strong and stable in both oxidative and reductive environments.In fact,durability of 60,000h has been reported [4].Second,the protonic conductivities achieved in a well-humidi®ed PFSA membrane can be as high as 0.2S/cm at PEM fuel cell operating temperatures.This translates to a cell resistance as low as 0.05O cm 2for a 100m thick membrane with voltage loss of only 50mV at 1A/cm 2[1].Fig.1.PEM fuel cell stack hardware.V .Mehta,J.S.Cooper /Journal of Power Sources 114(2003)32±5333Given these advantages,there are several disadvantages to the use of PFSA membranes in PEM fuel cells.In addition to the membrane material being expensive (currently aver-aging US$25kW À1[4]),disadvantages can be categorized as those related to safety,supporting equipment require-ments,and temperature-related limitations.First,safety concerns arise from toxic and corrosive gases liberated at temperatures above 1508C [4,9].Decomposition products could be a concern during manufacturing emergencies or vehicle accidents and could limit fuel cell recyclingoptions.Fig.2.Classification of MEAmaterials.Fig.3.Classification of MEA manufacturing alternatives.34V .Mehta,J.S.Cooper /Journal of Power Sources 114(2003)32±53Second,extensive supporting equipment requirements for use with PFSA membranes are described by Glipa and Hogarth[4]and Crawford[10].Among the equipment needed,the hydration system adds considerable cost and complexity to the vehicle powertrain.Third,at elevated temperatures PFSA membrane properties degrade.For example,the conductivity at808C is diminished by more than10times relative to that at608C[5].Also,phenomena like membrane dehydration,reduction of ionic conductivity, decreased af®nity for water,loss of mechanical strength via softening of the polymer backbone and increased parasitic losses through high fuel permeation are observed at tem-perature above808C[4].Making the temperature problems seem worse,Rikukawa and Sanui[5]note that operation of PEM fuel cells improves at elevated temperatures.Speci®-cally,operation at elevated temperatures increases the rates of reaction,reduces problems related to catalyst poisoning by absorbed carbon monoxide in the150±2008C range, reduces the use of expensive catalysts,and minimizes problems due to electrode¯ooding.Because PFSA mem-branes must be kept hydrated to retain proton conductivity, the operating temperature must be kept below the boiling point of water.Some increase in operating temperature,up to 1208C,may be possible at the expense of operation under pressurized steam.This alternative will however shorten the life of the cell.Because of the disadvantages of PFSA membranes,an extensive literature review was done to identify alternatives. Much of the literature is summarized by Glipa and Hogarth from Johnson Matthey Technology Center,UK[4]and Rikukawa and Sanui from Sophia University,Japan[5]. Particularly,Rikukawa and Sanui suggest the foremost challenge is to produce materials that are cheaper than PFSA.They note that some sacri®ce in material lifetime and mechanical properties may be acceptable,providing the cost factors are commercially realistic.Among the different alternatives,Rikukawa and Sanui suggest the use of hydrocarbon polymers even though they had been previously abandoned due to low thermal and chemical stability.Hydrocarbon membranes provide some de®nite advantages over PFSA membranes.First,they are less expensive.Second,many types are commercially avail-able.Third,polar groups can be formed to have high water uptakes over a wide temperature range with the absorbed water restricted to the polar groups of polymer chains.Forth, decomposition of hydrocarbon polymers can be depressed to some extent by proper molecular design.Finally,it is possible membranes made from hydrocarbon polymers will be recyclable by conventional methods.Glipa and Hogarth[4]extend upon Rikukawa and Sanui's list of alternatives.Their®nal taxonomy includes®ve categories of membranes:(1)per¯uorinated,(2)partially ¯uorinated,(3)non-¯uorinated(including hydrocarbon), (4)non-¯uorinated(including hydrocarbon)composite, and(5)others.These authors also note the wide range of material properties among and between membranes in each category.Speci®cally,they cite membranes with degrada-tion temperatures ranging from250to5008C,water uptake from2.5to27.5H2O/SO3H,and conductance from10À5to 10À2S/cm.Together,Glipa and Hogarth and Rikukawa and Sanui identify over60alternatives to PFSA membranes.Among these,we identi®ed46membranes with characteristics that make them ill-suited for use as automotive PEM fuel cells based on the recommendations of and personal communica-tions with Glipa[11]Rikukawa[12]and with DesMarteau [13].Table1lists these46membranes,rejected on the basis of13reasons shown as column headings.After removing the 46`ill-suited'membranes,16membranes remain for further study.Table2provides design information for these16 acceptable membranes.2.1.2.Catalyst layer designIn PEM fuel cells,the type of fuel used dictates the appropriate type of catalyst needed.Within this context, tolerance to carbon monoxide(CO)is an important issue, particularly when hydrogen is formed from methanol by steam reforming.Methanol reformate contains as much as 25%carbon dioxide(CO2)along with a small amount(1%) of carbon monoxide(CO).It has been proven that PEM fuel cell performance drops with a CO concentration of only several parts per million.This is due to the strong chemi-sorption force of CO onto the catalyst[25].There are two techniques to counter the problem of CO poisoning:fuel reforming or catalyst alloying.First,the fuel can be reformed to reduce the CO level in fuel.If using on-board fuel reforming,it has been determined that the PEM fuel cell must be capable of tolerating a CO concentration of at least100ppm in order to reduce the size of the reformer unit.Reforming techniques include[2,26]:Selective oxidation:Selective oxidation is usually the pre-ferred method for CO removal because of the parasitic system loads and energy required by the other methods.In selective oxidation,the reformed fuel is mixed with air or oxygen either before the fuel is fed into the cell or within the stack itself.Another approach involves the use of a selective oxidation catalyst that is placed between the fuel stream inlet and the anode catalyst.Current selective oxidation technologies can reduce CO levels to<10ppm,but this is difficult to maintain under actual operating conditions. Catalysis:Ballard Power Systems has demonstrated that the CO level in fuel cell can be significantly reduced(to 100ppm)by passing reformed methanol and small amount of oxygen over a Pt on aluminum catalyst.Hydrogen peroxide bleeding:The use of hydrogen per-oxide(H2O2)in an anode humidifier successfully miti-gated100ppm CO in an H2rich feed[27].It was reported that mitigation appears to be provided by an unintended O2bleed produced by the decomposition of H2O2in the humidifier rather than by H2O2vapors transported from the humidifier to the anode.V.Mehta,J.S.Cooper/Journal of Power Sources114(2003)32±5335Table 2Possible alternatives to PFSA membranes Membrane no.Membrane type (category)Design information1a ,b ,b -Trifluorostyrene grafted membrane (partially fluorinated)This membrane is based on grafting of a ,b ,b -trifluorostyrene and PTFE/ethylene copolymers [1]2Acid-doped polybenzimidazoles [PBI]membrane (non-fluorinated composite)This membrane is based on polybenzimidazole (PBI)and acids like phosphoric acid.Polybenzimidazole (PBI)is a basic polymer (p K a 5.5)which can readily be complexed with strong acids.The immersion of a PBI film in aqueous phosphoric acid leads to a membrane which has high conductivity and thermal stability [14]3BAM3G membrane (Ballard Advance Material of Third Generation Membrane)(non-fluorinated)This membrane is based on polymerization of a ,b ,b -trifluorostyrene and includes monomer(s)selected from a group of substituted a ,b ,b -trifluorostyrene.The polymers possess favorable properties,such as high heat stability,chemical resistance and favorable mechanical properties,such as tensile strength,compared to the homopolymeric material formed from a ,b ,b -trifluorostyrene (TFS)alone [15]4Base-doped S -polybenzimidazolesmembrane (non-fluorinated composite)This membrane is based on the introduction of organic or inorganic Bronsted bases to sulfonated PBI [4]5Bis (perfluoroalkylsulfonyl)imide membrane (perfluorinated)Bis (perfluoroalkylsulfonyl)imide is based on the copolymerization of sodium 3,6-dioxa-D 7-4-trifluoromethyl perfluorooctyl trifluoromethyl with tetrafluoroethylene (TFE).This membrane is thermally stable to nearly 4008C in the acid form.It has excellent conductivity and its water uptake is typically 40%by weight [13]6Crosslinked or noncrosslinked sulfonated polyetheretherketone membrane (non-fluorinated)This membrane is based on polyetheretherketone.Direct sulfonation of polyetheretherketone results in materials with wide range of equivalent weights.The initial results obtained with the crosslinked and non-crosslinked S -PEEK membranes show very good thermal stability,proton conductance and water uptake compared to PFSA at even elevated temperature [16]7Gore-Select TM membrane (perfluorinated)This is an ultra-thin integral composite membrane,which includes a base material and an ion exchange material or ion exchange resin with 0.025mm thickness.The preferred base material is an expanded-polytetrafluoroethylene (e-PTFE)membrane with thickness of less than 0.025mm and a porous microstructure.The ion exchange resin substantially impregnates the membrane.Suitable ion exchange materials include perfluorinated sulfonic acid resin,perfluorinated carboxylic acid resin,polyvinyl alcohol,divinyl benzene,styrene-based polymers and metal salts with or without a polymer.A surfactant is preferably employed with the ion exchange material to ensure impregnation of the interior volume of the base material.Alternatively,the composite membrane may be reinforced with a woven or non-woven material bonded to one side of the base material.Suitable woven materials may include,scrims made of woven fibers of expanded porous polytetrafluoroethylene;webs made of extruded or oriented polypropylene or polypropylene netting [17]8Imidazole doped sulfonated polyetherketone [S -PEK]membrane (non-fluorinated)Sulfonated poly(arylether ketone)membranes and in particular sulfonated polyetherketone (S -PEK)exhibit high proton conductivities when in their hydrated forms.S -PEK can be complexed with imidazole to give membranes with high proton conductivities around 2Â10À2S/cm at a high temperature of 2008C [4,18]9Methylbenzensulfonated polybenzimidazoles membrane (non-fluorinated)These alkylsulfonated aromatic polymer electrolyte posses very good thermal stability even above 808C.Water uptake and proton conductivity are also reported to be higher than PFSA membranes above 808C [5]10Methylbenzensulfonate poly(p -phenylene terephthalamide)membrane (non-fluorinated)These alkylsulfonated aromatic polymer electrolyte posses very good thermal stability even above 808C.Water uptake and proton conductivity are also reported to be higher than PFSA membranes above 808C [5]11Perfluorocarboxylic acid membrane (perfluorinated)Perfluorocarboxylic acid is based on a copolymer of tetrafluoroethylene and perfluorovinyl ether having a carboxylated group instead of a sulfonated group.The molar ratio of functional perfluorovinyl ether to tetrafluoroethylene in the copolymer is directly related to ion exchange capacity of resulting polymeric acid.Copolymerization of tetrafluoroethylene and functional perfluorovinyl ether is carried out by using a radical initiator [19]12Poly(2-acrylamido-2-methylpropanesulfonic acid [poly-AMPS]membrane (Other)This membrane is made from polymerization of AMPS 1monomer.AMPS 1monomer is made from acrylonitrile,isobutylene and sulfuric acid [20]13Styrene grafted and sulfonatedpoly(vinylidene fluoride)membranes [PVDF-G -PSSA](partially fluorinated)This membrane is based on the pre-irradiation grafting of styrene onto a matrix of poly(vinylidene fluoride)(PVDF)after electron beam irradiation.It can be cross-linked with divinylbenzene (DVB)or bis (vinylphenyl)ethane (BVPE).The proton conductivity of membrane is influenced by degree of cross linking [21]14Sulfonated naphthalenic polyimide (non-fluorinated)This membrane is based on sulfonated aromatic diamines and diahydrides.It gives a performance very similar to PFSA membranes [4]15Sulfonated poly(4-phenoxybenzoyl-1,4-phenylene)(S -PPBP)(non-fluorinated)This membrane is based on poly(4-phenoxybenzoyl-1,4-phenylene).This material is a poly(p -phenylene)derivative and is structurally similar to PEEK.The direct sulfonation of PPBP is reported to give a membrane that gives water absorption and proton conductance better than S -PEEK membranes [23]16Supported composite membrane (other)Composite membrane is made of ion conducting polymer (ICP)and poly-p -phenylene benzobisoxazole (PBO)substrates [24]V .Mehta,J.S.Cooper /Journal of Power Sources 114(2003)32±5337When alloying the catalyst to counter the problem of CO, one(a binary catalyst)or sometimes two elements(a ternary catalyst)are added to the base catalyst.Table3lists26anode catalyst alloys.As shown,binary and ternary anode catalysts are typically,but not always,Pt-based and supported on carbon(or``/C'').It can be summarized that for hydrogen contaminated with CO there are at least seven Pt-based catalysts that give performance equal or similar to that given by Pt/C with pure hydrogen cell:Pt-Ru/C,Pt-Mo/C,Pt-W/C, Pt-Ru-Mo/C,Pt-Ru-W/C,Pt-Ru-Al4,and Pt-Re-(MgH2). Table3lists13binary catalysts.Speci®cally,Iwase and Kawatsu[25]investigated10of these catalysts:Pt-Ru/C,Pt-Ir/C,Pt-V/C,Pt-Rh/C,Pt-Cr/C,Pt-Co/C,Pt-Ni/C,Pt-Fe/C, Pt-Mn/C,and Pt-Pd/C.Each catalyst was made of a20-wt.% alloy on carbon with a Pt loading rate of0.4mg/cm2in a5-wt.%PFSA solution.They found that only the Pt-Ru catalyst showed cell performance equivalent to that of pure hydrogen cell with a single metal Pt/C catalyst when exposed to reformate gas with100ppm of CO.Also,they found that Ru in the binary catalyst absorbs water and facilitates the oxidation of CO.Although adequate CO tolerance can be obtained over a Ru-range of15±85%,the optimum ratio of Pt/Ru was determined by Iwase and Kawatsu to be50:50. Other researchers add Pt-Mo/C and a non-Pt-based alloy Au-Pd/C to the list of possible binary catalysts.Speci®cally, Bauman et al.[28]found Pt-Mo/C to achieve high tolerance to low levels(10±20ppm)of CO in reformate without the need of an air bleed.However,at CO levels above20ppm,the bene®t of this catalyst is lessened.Although Pinheiro et al.[35]also found Pt-Ru/C to outperform Pt-Mo/C, Bauman et al.[28]found better performance with Pt-Mo/ C as compared to Pt-Ru/C catalyst.Finally,Lawrence Berkeley researchers[33]have developed a non-platinum-based binary catalyst.They reported a three-fold improve-ment in electro-oxidation of CO/H2with their Au-Pd cat-alyst as compared to a Pt-Ru catalyst.Tertiary catalysts are typically based on a Pt-Ru alloy.The largest number of tertiary catalysts along with some binary catalyst has been investigated by scientists at ECI Labora-tories[29]and performances were compared to pure Pt/C catalyst performance.They investigated Pt-Ru alloys with Ni,Pd,Co,Rh,Ir,Mn,Cr,W,Zr,and Nb.They found that out of all the catalyst investigated,in the presence of CO,the binary catalysts Pt0.53-Ru0.47and Pt0.82-W0.18were far superior to pure platinum.Of the two,Pt-Ru was better in the low potential region while Pt-W proved superior in the plateau region except at very high current densities.But the performance of ternary Pt0.53-Ru0.32-W0.15alloy exceeded both binaries in the low potential and potential plateau regions.Similarly,Pinheiro et al.[35]analyzed the perfor-mance of Pt-Ru,Pt-Mo,and Pt-Ru-Mo/C and found the tertiary catalyst to have the best performance.In another ternary catalyst development,Denis et al.[30] investigated the ternary electrocatalyst of Pt-Ru-Al4with no carbon support.Their results show that an unsupported Pt-Ru-Al4catalyst produced by high-energy ball milling gives equal performance to Pt-Ru/C when exposed to reformate gas with100ppm of ing similar kind of ball milling technique,Dodelet et al.[31]produced a ternary catalyst Pt-Re-(MgH2)without carbon support that performed better than Pt-Ru/C when exposed to reformate gas with100ppm of CO.Little information was found on cathode catalysts for PEM fuel cells,which do not have to be CO tolerant. Notably,in addition to the use of Pt/C,Ross et al.[33]at Lawrence Berkeley National Laboratory report the use of Pt-Ni/C and Pt-Co/C as cathode catalyst.Also,Faubert et al.[34]produced a special,non-platinum based cathode cata-lyst.The catalyst is produced by pyrolysis of iron acetate adsorbed on perylenetetracarboxylic dianhydride in Ar:H2: NH3under ambient conditions.Also,at the National Renew-able Energy Laboratory[32],a`rapid throughput'system has been developed to identify catalysts for oxygen reduc-tion.This study investigates1200bimetallic complexes. Approximately20complexes were found suitable for fuel cells although detailed information about what these com-plexes was not included in the report.2.1.3.Gas diffusion layer designThe GDLs,one next to the anode and the other next to the cathode,are usually made of a porous carbon paper or carbon cloth,typically100±300m thick.The porous nature of the GDL material ensures effective diffusion of each reactant gas to the catalyst on the membrane/electrodeTable3Anode catalyst materials[22,25,28±34]Single metal catalyst BinarycatalystTertiarycatalystPt/C XPt-Co/C XPt-Cr/C XPt-Fe/C XPt-Ir/C XPt-Mn/C XPt-Mo/C XPt-Ni/C XPt-Pd/C XPt-Rh/C XPt-Ru/C XPt-V/C XAu-Pd/C XPt-Ru-Al4XPt-Ru-Mo/C XPt-Ru-Cr/C XPt-Ru-Ir/C XPt-Ru-Mn/C XPt-Ru-Co XPt-Ru-Nb/C XPt-Ru-Ni/C XPt-Ru-Pd/C XPt-Ru-Rh/C XPt-Ru-W/C XPt-Ru-Zr/C XPt-Re-(MgH2)X38V.Mehta,J.S.Cooper/Journal of Power Sources114(2003)32±53assembly.The structure allows the gas to spread out as it diffuses so that the gas will be in contact with the entire surface area of the catalyzed membrane[8,36].The GDL also assists in water management during the operation of the fuel cell.A GDL that allows the appropriate amount of water vapor to reach the membrane/electrode assembly keeps the membrane humidi®ed and improves the ef®ciency of the cell.The GDL allows the liquid water produced at the cathode to leave the cell so it does not¯ood. The GDL is typically wet-proofed to ensure that at least some,and hopefully most,of the pores in the carbon cloth or paper do not become clogged with water,which would prevent the rapid gas diffusion necessary for a good rate of reaction to occur at the electrodes[8,36].PTFE is the wet-proo®ng agent used for carbon-based PEM GDLs by several research groups[1,37,38].A literature review did not reveal any research group who has studied both carbon paper and carbon cloth with the speci®c objective of identifying the most favorable among these two in a PEM fuel cell.In a study of water manage-ment,Ralph et al.[39]found that carbon cloth offered a distinct advantage at high current densities in Ballard Mark V cells.In fact,the slope of the pseudolinear region of the cell potential versus current density plot was lowered from 0.27to0.21O cm2and the limiting current was substantially raised by the use of the carbon cloth.Also,the cloth was found to enhance mass transport properties at the cathode derived from improved water management and enhanced oxygen diffusion rates.Finally,the surface porosity and hydrophobicity of the cloth substrate are more favorable for the movement of the liquid water.2.2.MEA manufacturing2.2.1.Membrane andGDL fabricationWhereas the catalyst layer is typically prepared and applied during MEA assembly,the membrane and GDL are fabricated prior to assembly.Considering membranes ®rst,a variety of polymerization processes are used in the fabrication of PFSA membranes and the alternatives listed in Table2.Table4presents the processing steps and the primary inputs and outputs for many of these membranes. Notably,the processing steps include many chemical pro-cesses and a number of energy intensive heating and drying steps.Process¯ow diagrams and additional synthesis infor-mation is available in[7].Like the membrane,the GDL is fabricated prior to assembly.Carbon paper is fabricated in four steps:pre-pregging(continuous strands are aligned with spools and a surface treatment is followed by a resin bath and formation of a layered structure),molding,carbonization,and graphi-tization[24].Carbon cloth is also fabricated in four steps: carbonaceous®ber production(made from mesophase pitch spun by melt spinning,centrifugal spinning,blow spinning, etc.),®ber oxidation,cloth formation by weaving or knitting, and graphitization[42].Finally,the carbon cloth or paper is wet-proofed,typically using PTFE.Speci®cally,Bevers et al.[37]describe their wet-proo®ng process in which a carbon/ PTFE suspension is applied to both sides of the carbon cloth or paper substrate.Application of the carbon/PTFE mixture ¯attens out any roughness of the cloth or paper and improves the gas and water transport properties.2.2.2.MEA assemblyAs shown in Fig.4,there are two modes of MEA assembly:(1)application of the catalyst layer to the GDL followed by membrane addition or(2)application of the catalyst layer to the membrane followed by GDL addition. No matter the mode of assembly,the catalyst layer can be prepared and applied in two separate steps(catalyst pre-paration and application)or using a single sputtering pro-cess.As described later,several manufacturing options exist within these two modes of MEA manufacturing.For either mode,early catalyst preparation methods were based on the use of platinum ter,Raistrick[43] used10%carbon-supported platinum(Pt/C,2nm size par-ticles)and a100m thick catalyst layer instead of platinum black.The obvious advantage was a higher degree of platinum dispersion.Raistrick impregnated the Pt/C//PTFE catalyst layer on carbon cloth with a solution of PFSA,in order to®ll it,or at least a signi®cant part of it,with recast ionomer prior to hot pressing the impregnated electrode onto the membrane.This process overcame cell performance problems related to the lack of protonic access to the majority of catalyst sites not in intimate contact with mem-brane.Ticianelli et al.[44]further improved cell perfor-mance by optimizing the percentage of PFSA impregnant. They replaced a10%Pt/C-100m catalyst layer with a20% Pt/C-50m catalyst layer.Although this work was considered a major breakthrough by Gottesfeld and Zawodzinski[1], not all methods use ionomer impregnation,as follows.As described later,spreading method,spraying method and catalyst powder deposition method do not use ionomer impregnation.For mode1,we identi®ed®ve methods for catalyst pre-paration and application to prepare a GDL/catalyst assembly. Spreading:The spreading method described by Sriniva-san et al.[45]consists of preparing a catalyzed carbon and PTFE dough by mechanical mixing and spreading it on a wet-proofed carbon cloth using a heavy stainless steel cylinder on a flat surface.This operation leads to a thin and uniform active layer on the GDL/catalyst assembly for which the Pt loading is directly related to the thick-ness.Spraying:In the spraying method described by Srinivasan et al.[45],the electrolyte is suspended in a mixture of water,alcohol,and colloidal PTFE.This mixture is then repeatedly sprayed onto wet-proofed carbon cloth. Between each spraying,the electrode is sintered in order to prevent the components from re-dissolving in the next layer.The last step is rolling of the electrode.ThisV.Mehta,J.S.Cooper/Journal of Power Sources114(2003)32±5339。

AUTO PARTS | 汽车零部件车用质子交换膜燃料电池电堆耐久性问题研究综述谢晓荷上海燃料电池动力系统有限公司 上海市 201804摘 要： 近年来，在国内外研究人员的不懈努力下，燃料电池技术取得了长足的进步。

但是，耐久性差和可靠性不足，仍然是阻碍其大规模商业化的重要因素。

现阶段针对燃料电池性能衰减问题的研究，从关键组件到核心材料，有很多新的观点、规律和机理，已经得到大家的认可。

然而，燃料电池内部微观层面的复杂的结构蠕变和粒子传输特性衰变，依然模糊不清。

本文主要介绍了燃料电池的基本原理，以及在典型车载燃料电池工况包括启-停工况、怠速工况、动态负荷工况、额定功率工况和过载工况下的衰减过程机理。

这些研究成果的综述，对质子交换膜燃料电池堆耐久性机理研究及耐久工况的设计实施具有重要意义。

关键词：质子交换膜燃料电池　耐久性1　背景介绍人类社会飞速的发展消耗了大量的化石能源，随之而来的环境污染和气候变化的问题已经成为全球关注的焦点。

同时，石油危机和能源安全问题成为了各国可持续发展的主要矛盾，全球的汽车产业面临着巨大的挑战。

燃料电池汽车（FCV）以其零污染、长续航里程、氢气来源广泛和加注时间短的优势称为能源转型的突破口，将逐步拓展至交通运输、工业生产、家庭生活等领域，人类社会将逐步跨入氢经济时代[1]。

在过去的几十年里，人们一直致力于研发性能优异、价格低廉的质子交换膜燃料电池。

特别是近年来，美国、加拿大、韩国、日本、中国、欧盟等国家和地区不断加大对燃料电池示范应用和基础设施的投入。

例如，在2014年发布第一代Mirai后，丰田将于2020年12月发布并全球销售第二代Mirai，其峰值功率为128kw，体积比功率高达4.4kw/L。

中国国家能源局也于2020年9月出台政策，对燃料电池汽车关键核心技术的研究和示范应用给予奖励。

尽管近年来取得了许多成绩，但成本和耐久性仍然是阻碍质子交换膜燃料电池大规模商业化的主要原因[2]。

质子交换膜燃料电池大电流密度下运行工况优化研究张洪凯;詹志刚;何晓波;帅露;隋邦杰;潘牧【摘要】利用计算流体动力学软件,针对在大电流密度、阴极无加湿、阳极加湿,阴阳极有背压等操作特点下运行的PEM电池进行数值模拟,综合考虑电池性能和电流密度分布的均匀性,寻求最优工况点.结果表明,对于给定的操作压力,存在一个最佳性能温度,压力增加,最佳温度随之增加,在压力为100,200,300 kPa时,最佳性能温度分别为75,60,50 ℃;由于阴极不加湿,在最佳性能温度点膜含水量分布及电流密度分布不均匀;在较低温度下运行时电流密度分布均匀性随着压力的增加逐渐提高,但在较高温度下运行时则相反.%Considering the performance and uniformity of the current density distribution, CFD software is used in this paper to simulate the PEM cells, which operate at large current density, no cathode humidification but full anode humidification, and backpressure, to seek for the optimized operating point.The main conclusions are as follows: for a given operating pressure, there is an optimal temperature which makes the fuel cell have the best performance, and the optimal temperature increases with the pressure;the best temperatures for 100,200 and 300 kPa are 75,60 and 50 ℃, respectively.Since the cathode is not humidified, the membrane water content distribution and current density distribution are not uniform at the optimum performance temperature point;the current density distribution uniformity increases with pressure at lower temperatures, but it has the opposite trend at higher temperatures.【期刊名称】《武汉理工大学学报（交通科学与工程版）》【年(卷),期】2017(041)003【总页数】5页(P523-527)【关键词】质子交换膜燃料电池;电流密度;水传输;运行工况;优化【作者】张洪凯;詹志刚;何晓波;帅露;隋邦杰;潘牧【作者单位】武汉理工大学材料复合新技术国家重点实验室武汉 430070;武汉理工大学能源与动力工程学院武汉 430063;武汉理工大学材料复合新技术国家重点实验室武汉 430070;武汉理工大学能源与动力工程学院武汉 430063;武汉理工大学材料复合新技术国家重点实验室武汉 430070;武汉理工大学能源与动力工程学院武汉 430063;武汉理工大学能源与动力工程学院武汉 430063;武汉理工大学汽车工程学院武汉 430070;加拿大维多利亚大学机械系集成能源系统实验室维多利亚市 V8W 2Y2;武汉理工大学材料复合新技术国家重点实验室武汉 430070【正文语种】中文【中图分类】TM911.4在化石能源面临枯竭和环境污染日益严重的今天，寻找一种高效、无污染的新型能源成为了亟待解决的问题，质子交换膜(PEM)燃料电池因其高效率、高功率密度、低污染等优点广泛受到人们的关注.PEM燃料电池可以应用于汽车、航天、移动充电设备等领域，被认为市场潜力十分巨大[1].由于市场应用的需求，PEM电池体积不断减小而功率密度不断增加，日本丰田汽车公司于2014年推出了MIRAI 燃料电池汽车，其电堆的质量功率密度和体积功率密度达到2.0 kW/kg和3.1kW/L[2].电池堆在大功率下运行，电流密度往往也较高，可能高达1.5～2.5A/cm2，因此，一般需要增加背压，以提高反应气体浓度；同时电池生成水较多，合理利用生成水，可以简化或去掉加湿系统.因此研究膜电极内部水、气传输及分布规律，寻找最优工况点，对电池高效、稳定、持久运行，具有重要意义.Su等[3-4]通过模拟方法探索了温度、湿度、压力、气体过量系数等操作参数对电池性能的影响.Kim等[5]分析了反应气体加湿度对燃料电池性能的影响，认为阳极充分加湿而阴极不加湿的条件下质子交换膜仍能被充分润湿.Amirinejad等[6]研究操作条件对电池性能的影响发现，在操作压力较高的条件下提高温度会使得电池性能提高.Santarelli等[7]通过实验发现，只有阳极加湿的燃料电池性能会随着操作压力的提高而明显提高，同时还能够提高电池稳定性.Jang等[8]通过研究发现，阳极加湿温度提高会使得电池性能提高.文中针对在大电流密度、阴极无加湿、阳极加湿，阴阳极有背压等操作特点下运行的PEM电池，利用计算流体动力学软件，进行数值模拟，寻找电池最佳工况点.获得的结论对于PEM电池的设计和操作具有参考意义.1.1 几何模型根据实际金属板电池结构，建立三维单流道电池模型，因其结构对称，为减少计算量，选取1/2流道区域建模，见图1.外围尺寸为50 mm×1.1 mm×1.435 mm，活性面积为55 mm2，气体和冷却水流道宽度与深度为0.5 mm×0.4 mm，集流板厚度0.1 mm，气体扩散层厚度0.2 mm，催化层厚度0.01 mm，膜厚度0.015 mm.在进行网格灵敏性验证后，确定总网格总数为89 000个.1.2 控制方程质子交换膜燃料电池是一个多相、多尺度的复杂系统.其内部流道及多孔介质内气体的扩散、水的相变及流动，催化层内部的电化学反应、水在质子交换膜内的传递都同时发生并且相互耦合.描述上述现象及过程的主要控制方程包括如下的质量守恒方程、动量守恒方程、组份守恒方程、能量守恒方程、电荷守恒方程等. +·(ερu)=Sm+·(ερuu)=-εp+·(εμu)+Su+·(ερcpu θ)=·(keffθ)+SQ(ερck)+·(ερuck)=ck)+Sk(σeleΦele)+Sele=0(σionΦion)+Sion=0式中：ρ为组分的密度；ε为孔隙率；t为时间；Sm为质量源项；为速度；p为压力；μ为粘度；Su为动量源项；cp为比定压热容；θ为温度；keff为有效导热系数；SQ为能量源项；ck为组分浓度；Deffk为组分有效扩散系数;Sk为组分源项；σele和σion为电子电导率、质子电导率；Φele和Φion为固相电势、膜相电势；Sele和Sion为电子电流源项、质子电流源项.1.3 操作条件文中主要研究阳极和阴极加湿度分别为100%，0%条件下大电流运行时电池最优性能.阴阳极过量系数分别为1.5和2.5，出口背压50，100，150，200 kPa，操作温度和反应气体的温度为50，60，70，80，90 ℃.主要电化学参数及反应气体物性见表1[9-10]，电池主要部件材料物性见表2[11-12].图2为模拟与实验测试伏安曲线对比，由图2可知,模拟值与实测值基本一致，同时也验证了该模型可靠性.图3为1.5 A/cm2时不同操作条件下电池的电压.随着操作压力的增加，因为反应气体浓度增加，电池性能也逐渐增加.在相同压力下，存在一个最佳性能的操作温度.例如，在压力为300 kPa时，随着温度从50 ℃开始增加，电池性能渐渐增加，在75 ℃左右到达最大值，之后又逐渐降低，这是因为电池性能受到氧气浓度和膜润湿性两个因素的影响.在温度较低时，液态水容易生成，催化层中液态水相饱和度较高，使得膜润湿性较好，内阻较低；但同时较高的液态水相饱和度阻碍了反应气体的传输，不利于电化学反应的进行；温度继续增加，两种作用的趋势相反，膜逐渐变得过于干枯，内阻增加，电池性能下降；在75 ℃左右时这种综合作用得到了最佳的性能.图4为300 kPa下不同温度时催化层中间平面液态水相饱和度分布.沿气体流道从进口到出口方向，水汽逐渐积累，相饱和度也逐渐增加；右半边处于冷却水流道下而左半边处于气体流道下，温度差异导致右边液相饱和度总体高于左半边.在50 ℃时，液相饱和度(即液态水占据的孔隙体积比例)高达17%，并且范围较大，这种状态必然有利于膜的润湿而阻碍氧气的传输.随着温度的升高，液相饱和度逐渐降低，80 ℃时仅局部有少量液态水，90 ℃时所有反应面积上都为干的.图5为300 kPa下膜中中间平面上磺酸基团水含量分布.其总体分布和液相饱和度的分布是一致的，随着温度的升高，水含量降低，即膜的润湿性降低，质子电阻升高.图6是过量系数为2.5，温度为70 ℃时Δq随着操作压力的变化关系，Δq定义为反应生产水与阴极出口气体以饱和状态带走的水的差值.由图6可知，Δq随着压力升高而增加，说明升高操作压力可以使较多的水保留在MEA中，有益于膜的润湿；降低操作压力，被空气带走的水增加，MEA剩余的水分减少，因此膜容易变干，为保持膜较佳的润湿状态进而保持膜的性能，需要操作降低温度.在操作压力为200 kPa和150 kPa时，电池性能最优时对应的温度分别为60 ℃和55 ℃，这些点构成了电池性能最优的温度控制曲线，见图3.图7是操作压力为100 kPa下不同温度膜中间平面水含量.同样的电流密度与温度下，与图5相比较，膜的润湿状态显著下降，反应在图3中，是电池性能显著下降.图3中在100 kPa等操作压力下电池性能并非单调变化，温度增高时阴极侧膜润湿性降低，但阳极侧保持100%加湿，实际带入的水汽量增加，膜阳极侧以及膜整体的润湿有所改善；即使膜中水含量一定，随着温度的升高，水在膜内扩散系数会增加，水在膜内的分布会更加均匀，因此性能反而有增高趋势，但总体上增量不大.人们除了希望PEM电池能有最佳的电输出性能外，同时也希望在活性面积上电流密度等各物理场能均匀分布，这样才可以使得电池长久、稳定运行.图7和图5对比，同样的温度下，压力较高时膜中水含量分布较为均匀；同样的压力下，在温度较低时因催化层液态水较多，使得膜中水含量较高且分布较为均匀.图8为50 ℃与75 ℃时不同压力膜中间面的电流密度分布.其中横坐标为活性面积上出现的电流密度范围，从0.9到2.1 A/cm2，以0.1 A/cm2分档计算.在50 ℃、 300 kPa下，大部分区域工作电流密度为1.5～1.8 A/cm2，而随着操作压力的降低，工作电流密度逐渐分散在更大区域内，也即分布更加不均匀，这和前面分析的膜的水含量分布规律是一致的.在75 ℃ 100 kPa下，大部分区域工作电流密度为1.5～1.8A/cm2，显得比较均匀，这是因为此时膜偏干，膜干的“比较均匀”，而随着操作压力的增加，膜总体的润湿性提高，但并不均匀，使得工作电流密度逐渐在更大区域内分散，也即分布更加不均匀，这种分布状态不利于对电池长久、温度运行，因此还需要在结构设计和运行管理方面进行改进.1) 在1.5 A/cm2、阳极100%加湿、阴极无加湿条件下，随着操作压力的增加，电池性能增加.2) 对于给定的操作压力，存在一个最佳性能温度，压力增加，最佳温度也随之增加，在压力为100，200，300 kPa时，最佳性能温度分别为75，60，50 ℃.3) 由于阴极不加湿，在最佳温度时膜中的含水量分布及电流密度分布不均匀；在较低温度下运行时电流密度分布均匀性随着压力的增加逐渐提高，但在较高温度下运行时则相反.【相关文献】[1]YUN W, KEN S, CHEN Y, et al. A review of polymer electrolyte membrane fuel cells: technology, applications, and needs on fundamental research[J]. AppliedEnergy,2011,88:981-1007.[2]DONG H J, KWANG N K, SEUNG M B, et al. The effect of relative humidity of the cathode on the performance and the uniformity of PEM fuel cells[J]. International Journal of Hydrogen Energy,2011,36:12499-12511.[3]SU A, FERNG Y M, SHIH J C. CFD investigating the effects of different operating conditions on the performance and the characteristics of a high-temperature PEMFC[J]. Energy,2010,35:16-27.[4]SUKKEE U, WANG C Y. Computational study of water transport in proton exchange membrane fuel cells[J]. Journal of Power Sources,2006,156:211-223.[5]KIM H Y, KIM K. Numerical study on the effects of gas humidity on proton-exchange membrane fuel cell performance[J]. Hydrogen Energy,2016(1)：1-8.[6]AMIRINEJAD M, ROWSHANZAMIR S, MOHAMMAD H, et al. Effects of operating parameters on performance of a proton exchange membrane fuel cell[J]. Journal of Power Sources,2006,161:872-875.[7]SANTARELLI M G, TORCHIO M F. Experimental analysis of the effects of the operating variables on the performance of a single PEMFC[J]. Energy Conversion and Management,2007,28:40-51.[8]JANG J H, CHIU H C, YAN W M, et al. Effects of operating conditions on the performances of individual cell and stack of PEM fuel cell[J]. Journal of Power Sources,2008,180:476-483.[9]CORINNA H, FRANK K, ALEXANDER D. Study of the influence of key test parameters on the performance of a PEMFC stack[J]. Solid State Ionics,2015,275:75-79.[10]HOMAYOON K, MEHRZAD S, MOHAMMADREZA H, et al. Model development and optimization of operating conditions to maximize PEMFC performance by response surface methodology[J]. Energy Conversion and Management,2015,93:9-22.[11]HUANG C P, JIANG R C, ELBACCOUCH M, et al. On-board removal of CO and other impurities in hydrogen for PEM fuel cell applications[J]. J Power Sources,2006,162:563-71.[12]MIN C H, HE Y L, LIU X L, et al. Parameter sensitivity examination and discussion of PEM fuel cell simulation model validation part II: results of sensitivity analysis and validation of the model[J]. Journal of Power Sources,2006,160:374-385.。

质子交换膜燃料电池耐久性测试分析梁高新;朱东;姚汛【摘要】为了研究燃料电池的耐久性，并对其衰退机理进行分析，本文在Greenlight平台上，对20片单体组成的功率为1 kW的电堆在DOE循环工况下进行90 h的耐久性实验。

通过分析电堆在DOE循环工况下进行不同时段的电堆衰退曲线，整体的电堆衰退曲线以及电堆的极化曲线来考察电堆在DOE循环工况下的性能衰退。

分析了电堆的衰退机理，并提出了自己的猜想并加以验证，得出催化剂的表面氧化造成的催化剂活性下降是引起质子交换膜燃料电堆的性能衰退的主要原因。

%In order to study the durability of fuel cells and analyze the mechanism of recession , the Green-lightg500 test station platform was use to test the durability of the fuel cells which is consisted by 20 pieces of fuel cell monomer with 1kW stack power in DOE cycle durability test for 90h.Throughsurvey the recession curves in different times and the Polarization curves using the DOE MEA/Stack Durability Protocol , we analysis the Mech-anism of recession and raise our ownhypotheses .Finally, we conclude that catalyst activity decline caused by catalyst surface oxidation state change is the main source of performance degradation of the stack .【期刊名称】《佳木斯大学学报（自然科学版）》【年(卷),期】2014(000)004【总页数】5页(P530-533,537)【关键词】质子交换膜燃料电池;加速老化实验耐久性;极化曲线【作者】梁高新;朱东;姚汛【作者单位】同济大学新能源汽车工程中心，上海 20180;同济大学新能源汽车工程中心，上海 20180;同济大学新能源汽车工程中心，上海 20180【正文语种】中文【中图分类】U473.40 引言质子交换膜燃料电池是一种电化学的发电装置，它与一些传统的动力装置相比，具有电流密度高，能源效率高，生成物是水，所以对环境无任何污染，被认为是环境友好型的发电装置，未来会在交通运输以及固定基站等方面发挥巨大的潜力[1，2]．PEMFC发动机也被认为是最有可能替代现有的发动机作为汽车的动力源．最近几年国内外的在这方面投入了大量的精力，在提高性能，成本和耐久性方面都有了实质性的进展．但是，PEMFC电池的耐久性一直是阻碍燃料电池商业化生产的原因．众所周知，燃料电池要想商业化，电池的耐久性一直都是应该首先被提升．一直以来国内对于PEMFC电堆的耐久性研究比较欠缺，一方面因为对电池的耐久性考察是非常耗时的工作，另一方面耐久性测试的耗费巨大．近年来，对于PEMFC的耐久性研究日益迫切，许多机构已经进行相关的耐久性实验．到目前为止，大多数燃料电池耐久性实验都是在恒电流条件下进行的．Knight[3]等在2004 年完成了 PEMFC 的12000 h 的寿命实验，其性能衰退为0．5μV/h．S．J．C．Cleghorn等[4]对 PEMFC 单电池进行了寿命试验，该PEMFC在800mA/cm2．电流密度条件下连续运行三年，性能衰减率为 4 －6μV/h．S．Y．Ahn[5]等考察了一个由40片单电池组成的PEMFC电堆的耐久性．Ballard公司使用Mk600型小功率PEMFC电堆连续运行了8 000 h．本文就是基于此环境下，通过Greenlight平台对燃料电池进行加速老化试验，找出燃料电池电堆的衰退机理．1 实验1．1 实验目的燃料电池的耐久性和稳定性是燃料电池能否走上商业化之路的关键因素．高的耐久性可以保证燃料电池系统工作很长时间不出现故障．稳定性也是燃料电池性能的一个重要的评价指标．本实验就是通过在DOE工况测试燃料电池堆的衰退性能，进而分析燃料电池衰退性的机理．1．2 燃料电池电堆本实验采用的是由20片单电池组成的功率为1kW的燃料电池电堆Pt．该电堆的质子交换膜采用的是Nafion112膜，用/C作为阴阳极的电催化剂，阴极的的浓度为0．5mg/cm2，阳极的的浓度为0．1mg/cm2．阴极和阳极的流道是单蛇形流道．1．3 实验平台该系统的测试平台是加拿大Greenlight公司的G500燃料电池测试系统．该系统的测试功率为12kW，但是可以利用的极限功率为30kW．该测试平台可以对参数进行精确的控制，如:负载类型，反应气的流量及其加湿度，温度，冷却水流量等．1．4 实验工况本实验采用DOE循环工况[6]对燃料电池进行加速老化测试实验，该工况谱图的单循环有16个步骤，包含开路、低电流、中电流和高电流等阶段．实验的工况如表1所示．表1 DOE循环工况步骤时间(s) CXX 1 15 OCV 2 20 C80 20 C75 4 15 C88 5 24C80 6 20 C75 7 15 C88 8 25 C80 9 20 C75 10 15 C88 11 35 C80 12 20 C60 13 35 C65 14 8 C88 15 35 C75 16 40 C 3 88注:该工况谱图的单循环有16个步骤，包含开路、低电流、中电流和高电流等阶段，其中，CXX表示电压在XX时的电堆电流．DOE测试工况下各系统参数如下:氢/空进压力:60/60 KPa;氢/空湿度:0/80%;氢/空进温度:55/55℃;水出温度:60℃;氢气化学计量比:1．5;空气化学计量比:2．5．1．5 耐久性测试实验测试的实验步骤如下所示:(1)启动平台，进行电堆活化，活化的最高电流达400A．(2)测试电堆的极化曲线，并设置DOE循环工况下的工作电压．C88=10A，C80=50A，C75=100A，C65=200A，C60=250A．(3)按照DOE工况谱进行自动循环加载，进行加速老化实验测试．(4)期间按照DOE标准运行10．5h之后，由于氮气不足，系统停机．之后重新启动，活化电堆，测试极化曲线，恢复DOE测试工况．(5)按照DOE测试工况运行37．5h之后测试电堆的极化曲线，然后关闭氢气和空气的供应，用氮气进行扫气，之后系统停机．(6)系统再次开机，进行电堆活化，测试极化曲线，由于氮气不足，系统停机．(7)系统开机，重复上述操作，DOE循环工况加载，期间运行30小时，系统关闭．(8)整个期间按照DOE循环工况加载89h．2 实验结果与分析2．1 电压衰退曲线第一阶段:系统在DOE工况下运行10．5h，以200A工作点为例，电堆的平均单体电压与时间的关系如图1所示:图1 第一阶段电堆衰退曲线系统在开始的2h内，电堆的性能衰退很快，平均单体电压的衰退率为5mV/h，之后趋于平缓，基本上呈线性衰退，衰退率在0．625mV/h．第二阶段:系统停机之后，很短的时间内系统重新启动，在DOE工况下继续运行了37．5h，性能衰退曲线如图2所示:图2 第二阶段电堆的衰退曲线系统开机运行之后，电堆平均电压相对于停机之前的电压有一定的回升，大概上升了0．011V．在前10h电堆的性能衰退相对很快，衰退率为2．3mV/h．之后电堆的衰退相对平缓，在20h之后衰退率为 0．457mV/h．第三阶段:系统停机一段时间，重新开机启动到氮气不足导致停机，电堆运行时间为12h，电堆的平均衰退曲线如图3所示:图3 第三阶段电堆的衰退曲线开机时平均单体电压相对于第二阶段末的平均单体电压有了很明显的提升，电压从0．622V上升到0．645V，电压上升了 0．023V．在前两个小时电堆性能衰退很快，衰退率为4mV/h，之后进入稳定的平缓的衰退期，衰退率大概在0．635mV/h．第四阶段:系统氮气不足导致停机，之后系统在短时间重新启动，运行了30h．在前5h内，系统衰退率为2mV/h，在之后趋于稳定，衰退率为0．3mV/h．衰退曲线如图4所示:图4 第四阶段电堆衰退曲线开机时的电压相对于第三阶段末电压有小幅上升，大概上升了5mV．在前5h内，系统衰退率为2mV/h，在之后趋于稳定，衰退率为0．3mV/h．总的衰退曲线如图5所示:图5 运行89h电堆的衰退曲线从图中可以看出，电堆整体上是呈现衰退的趋势，但是在每次停机，重启之后性能都会有一定的提升，呈现出一种“锯齿形”的形状．且在刚启动的一段时间内，电堆的衰退很快，之后趋于平缓．2．2 结果分析为了解释上述电堆性能衰退曲线呈现的“锯齿形”的形状，提出如下三个猜想:1)催化剂表面氧化状态的改变;2)催化剂表面的清洗;3)水管理．(1)催化剂表面的氧化状态的改变阴极表面的催化剂在特殊的操作环境下可能会受到氧化，在燃料电池阴极会产生水而且有大量的空气，因此催化剂可能会发生如下的反应:催化剂表面的颗粒在接近开路电压的时候会被氧化成PtOx和PtOH．这两种产物都会使催化剂的活性降低，并且覆盖在催化剂表面，降低活化面积．但是当燃料电池关断之后，电压从1V降低到0V，同时经过氮气扫气，流道中的水和空气被氮气吹走，水和氧气的浓度下降的很多，这将会使PtOx和PtOH发生可逆反应重新生成活性较强的．当燃料电池重新启动的时候，增长的燃料电池的电压是因为阴极的PtOx和PtOH几乎没有，催化剂重新恢复活性导致．但是当燃料电池重新正常运行的时候，PtOx和PtOH又会重新生成，导致电压的衰退．(2)催化剂表面的清洗催化剂表面必须是没有污染物覆盖才可以保持很高的活性．普通的Pt电极吸附物包括 CO，NOx，H2S以及碳氢化合物等．在燃料电池工作过程中，空气过滤器不可能将所有的污染物都过滤掉，这些污染物通过空气附着在催化剂表面，降低了催化剂的活性．但是在开路电压的情况下，阴极的电势会接近1V，在有氧气的状况下，这个电压可以使上述的污染物氧化，从而达到催化剂表面的清洗，恢复活性．(3)水管理水管理在燃料电池的性能上起到一个至关重要的作用[7～9]．燃料电池在阴极会产生水．在开机启动的时候，膜电解液需要适当的水化来充分传输质子．但是如果生成的水不能及时的排出的话，会影响催化剂层，甚至会影响催化剂的活性，如上所述．以及气体扩散层和流道．如果流道积水的话，就会影响气体的在整个催化剂表面的分布，导致浓度不均，影响燃料电池的性能，特别是在像交指型流道这样出口被封堵的流道下，水更不容易排除，容易造成水淹，影响性能．在系统关断和重启的时候，通过氮气扫气，将流道内多余的水分排出，从而在开机的时候恢复燃料电池的性能．通过上述总的衰退曲线，进一步的验证上述几个猜想．通过分析第二阶段与第三阶段之间电压回升和第三阶段与第四阶段之间的电压回升之间的差异，我们可以得出水管理所带来的燃料电池性能的衰退相对来说很小．因为在第三阶段系统关断道第四阶段系统开启，之间时间很短，但是通过氮气的扫气，排出了电池流道中的积水，而催化剂的性能还没来的及恢复，燃料电池性能的回升主要是积水得到改善造成．而在第二阶段和第三阶段之间停机时间较长，催化剂有足够的时间来恢复活性．从而使电堆的性能有较大的回升．在开机启动之后，印记又会有大量的水和空气，导致平衡向生成PtOx和PtOH的方向发生反应．导致电堆的性能一开始衰退很快，经过一段时间之后，该反应达到一个平衡，则电堆就会呈现一个稳定的衰退．上图很好的验证了这一猜想．对于催化剂表面的污染，由于DOE工况中，有开路电压的情况，所以在电堆运行的过程中不断地自清洗，对电堆的性能的衰退不是很明显，本实验也无法明确的验证．2．3 极化曲线由图6和图7可以得到:图6 不同阶段电堆的极化曲线图 7 不同阶段电堆的功率曲线(1)两阶段的衰退程度基本相同，即初始性能到48h的衰退与48h活化后到90h 的衰退几乎相当．(2)48h活化后的性能相当于电堆运行10．5h后的性能．可以看出重新活化可以显著增强电堆的性能．3 结论由20片单体组成的功率为1kW的质子交换膜燃料电池电堆在greenlight平台上应用DOE循环工况进行89h的加速老化试验，加速老化的曲线呈现出“锯齿形”的形状．为了分析这种衰退性能，提出了三个猜想，通过分析可以得出催化剂的表面氧化是这种“锯齿形”形状的最主要的原因，而水管理造成的影响相对来说很小．而催化剂表面的自清洗无法的得到明确的验证．通过极化曲线也可以看出电堆的性能随着电堆运行的时间的不断增加，电堆的极化曲线逐渐的下降，电堆的功率也逐渐的下降，但是在停机一段时间进行活化之后，电堆的性能又会重新恢复．参考文献:[1] Barbir F．PEM Fuel Cells:Theory and Practice．New York:Elsevier Academic Press，2005．[2] Wang C，Mao ZQ，Bao FY，Li XG，Xie XF．International Journal of Hydrogen Energy，2005;30:1031 －4．[3] KNIGHTS S D，COLBOW K M，PIERRE J S T，et a1．Aging Mechanisms and Lifetime of PEFC and DMFC[J]．Journa1 of Power Sources，2004，127:127 － l34．[4] CLEGHORN S J C，MAYFIELD D K，MOORE D A，et a1．A polymer Electrolyte Fuel Cell Life Test:3 Years of Continuous Operation[J]．Journal ofPower Sources，2005，158:446 －454．[5] AHN SY，SHIN S J，HAHY，et a1．Performance and Lifetime A-nalysisof the kW—Class PEMFC Stack[J]．Journal of Power Sources，2002，106:295 －303．[6] DOE．DOE Cell Component Accelerated Stress Test Protocols for PEM Fuel Cells，＜http://www1．eere．energy．gov/hydrogenandfuelcells/fuelcells/pdfs/co mponent_durability_profile．pdf＞．[7] G．Pourcelly，A．Oikonomou，C．Gavach，J．Electroanal．Chem．287(1990)43．[8] M．Watanabe，Y．Satoh，C．Shimura，J．Electrochem．Soc．140(1993)3190．[9] T．E．Springer，M．S．Wilson，S．Gottesfeld，J．Electrochem．Soc．140(1993)3513．。

PEMFC 引射器的设计及特性分析刘英;许思传;常国峰【摘要】According to a high-pressure proton exchange membrane fuel cell system , the size of the ejec-tor and did the CFD simulation was designed on basis of the Sokolov ejector design theories , research on the ejec-tor potential performance was carried out .The results showthat:①Increasing the ejector outlet pressure and e-jector fluent presser will improve the ejecting factor .②the working fluid impact on the performance of the ejector is more complex , and cannot simply be summarized as increased or decreased , but depends on the value of the outlet pressure of the ejector .%以索科洛夫的引射器设计方法为基础，对一个高压质子交换膜燃料电池系统（ PEM-FC ）的引射器进行结构设计以及CFD仿真分析，研究了引射器的使用特性。

研究表明：随着压缩流体出口压力和引射流体压力的增加，引射器的引射系数随之增大；工作流体压力对引射器性能的影响随引射器出口所处工况的变化而变化。

【期刊名称】《佳木斯大学学报（自然科学版）》【年(卷),期】2014(000)002【总页数】4页(P198-201)【关键词】质子交换膜燃料电池;引射器;索科洛夫【作者】刘英;许思传;常国峰【作者单位】同济大学汽车学院，上海201804; 同济大学新能源汽车工程中心，上海201804;同济大学汽车学院，上海201804; 同济大学新能源汽车工程中心，上海201804;同济大学汽车学院，上海201804; 同济大学新能源汽车工程中心，上海201804【正文语种】中文【中图分类】TK4320 引言与传统的内燃机汽车相比，氢燃料电池汽车在排放方面，燃料利用率方面以及燃料来源方面有着巨大优势，因而氢燃料电池汽车是最具发展潜力的新能源汽车之一[1].但PEMFC汽车作为一种新型汽车要想得到产业化还有许多问题需要解决，其氢气供应系统便是问题之一[2].为了保证燃料电池的正常、稳定运行，又能将燃料电池中生成水排放到电池外部，通常采用氢气循环的方法，把电池内部生成的水带出电池后经过水气分离装置将液态水分出后，再将氢气循环回到电池重复使用，以提高氢气利用率.燃料电池氢气循环供应系统有多种形式[3]，目前比较常见的是氢气循环泵和回氢引射装置.氢气循环泵的使用虽然可以有效改善氢循环但需消耗额外的电以维持其运转[4]，相比而言引射器无移动部件，具有结构简单、运行可靠、无污染等优点，而且能够避免产生寄生功率[5].1 PEMFC引射器工作原理在PEMFC汽车中，氢气存储在高压瓶中，从储氢瓶中出来的氢气具有很高的压力，引射器可以将储氢瓶中出来的高压力低流速的氢气通过工作喷嘴进行减压增速，在喷嘴出口处达到超声速.当带有一定动能的喷射气体从喷嘴喷出时，与周围被喷射的气体进行动量交换，从而带动了气体向前运动，两种气体在混合室内混合，在有限的混合室内，当前面的气体被推向前进时，后面的气体变得稀少而使压力下降，即在吸入管出口附近和混合管入口段的一定范围内，造成一定负压，促使被喷射气体不断被吸入混合管内，又不断被喷射气体带走(如下图1所示).图1 引射器原理示意图2 PEMFC引射器的设计本文采用目前应用比较广泛的索科洛夫引射器设计方法[6]，根据能量守恒质量守恒和动量守恒定理结合经验公式对一高压系统所用引射器进行结构设计.对于PEMFC用引射器提出以下假设:1)氢气压力在进入引射器喷嘴入口前由减压阀减至500kPa;2)PEMFC阳极出口侧的压力约为为240kPa;3)PEMFC阳极入口侧温度为20℃，出口侧温度为80℃;4)引射器内部气体绝热指数和气体常数相同，k=1.41，R=4121J/kg·k.引射器的设计工况点参数如下表1:表1 设计工况点参数压力(kPa) 温度(℃) 质量流量(g/s)500 20 1.1引射端 200 80出口端入口端240 40图2 引射器装配图根据索科洛夫引射器设计方法进行尺寸设计，最终完成的引射器如图2所示.压力PC不变的情况下，增大引射器的入口压力PP，此时引射比的变化情况同A点相同，运行稳定但是引射比降低;增大引射器的入口压力PP，会发现，引射器会从稳定状态变为不稳定状态，出口压力将高于新工作流体压力所对应的临界出口压力，并且引射系数将先增大后迅速下降，直至出现负值.图3 不同入口压力下出口压力Pc与引射比u的关系曲线3 PEMFC引射器使用特性研究由于引射器的设计工况是固定的，而其实际应用往往是变工况运行状态，因此研究其在全负荷范围内的使用性能就显得极为重要.3.1 入口压力对引射器的影响分别设定入口压力为 6.0bar，5.5bar，5.0bar，4.5bar，引射端压力为 2.0bar，计算所得引射器出口压力与引射器引射比的关系曲线如图3所示.以引射压力为5.5bar为例，假设引射器在A点工况下工作，此时，引射器处于稳定工作状态，引射器的引射比处于最高值，此时，在保持引射端压力PH和出口压力PC不变的情况下，增大引射器的入口压力PP，不难发现，在变化过程中，引射器一直处于稳定工作状态，同时引射比在不断的减小.在保持引射端压力PH和出口压力PC不变的情况下，减小引射器的入口压力PP，则发现会发现，在引射器的入口压力PP减小量不大的情况下，引射器仍然会处于稳定工作状态，同时引射比在变化的过程中不断增大;在引射器的入口压力PP进一步减小的情况下，引射器此时的出口压力会等于新工作流体引射比关系曲线上的临界出口压力，此时引射器的引射比仍在增大;引射器的入口压力PP再次减小时，引射器则会处于新工作流体引射比关系曲线上的不稳定工作状态，此时引射器的引射比已经在减小，直至引射比变为负值，引射器出现倒流现象.假设引射器在B点工况下工作，此时，引射器处于临界工作状态，当保持引射端压力PH和出口当引射器在C点工况下工作，此时引射器处于非稳定工作状态.工作流体压力增加不大时，引射器继续处于非稳定工作状态，并且引射比减小;当工作流体压力增大到一定值时，引射器出口压力会达到引射器出口临界压力，引射器处于稳定工作状态，继续增大工作流体压力，引射器会一直处于稳定工作状态，但是引射比减小.减小引射压力，引射器处于不稳定工作状态，引射比会先增大之后迅速减小，直到为负值出现回流现象.综上所述，引射器引射比与引射器工作流体入口压力的关系是复杂的，这同时取决于混合流体的出口压力，当混合流体的出口压力不同时，改变引射器工作流体入口压力造成引射器引射比的变化规律时不同的.图4 不同引射压力下出口压力Pc与引射比u的关系曲线3.2 出口压力对引射器的影响在引射器入口压力保持不变，改变引射端压力的情况下，研究引射器出口压力和引射器引射比的关系，通过在上述条件下引射器出口压力和引射器引射比的关系曲线来研究引射器入口压力对引射器工作性能的影响.在计算中，设定入口压力为5.0bar，引射端压力分别为 1.8bar，2.0bar，2.2bar，计算所得引射器出口压力与引射器引射比的关系曲线如图4所示从图4中可以看出，各工况下的引射器工作变化规律基本相同，都存在一个出口临界压力Pcr，出口临界压力Pcr是随着引射流体压力的增加而增大的.在保持工作流体入口压力和引射端压力不变的情况下，随着引射器混合流体出口压力的减小，引射器的引射比会逐渐增大，直至最大值后，几乎保持不变.反之，随着引射器混合流体出口压力的增大，引射器的引射比会先保持不变，然后逐渐减小，直至变为负值.图5 引射器仿真沿轴线压力变化3.3 引射压力对引射器的影响从图4中可以看出，出口临界压力Pcr和最大引射比都随着引射流体压力的增加而增大的.这是因为，引射流体与喷嘴出口截面上工作流体间的压差会随着引射端流体压力的升高而增大，从而增强了工作流体对引射流体的卷吸能力，在入口工作流体质量流量不变的情况下，带走更多的引射流体质量流量，增大了引射器的引射比;另一方面，增加了混合流体的能量，增强了克服出口压力的能力，所以，使临界出口压力有所提高.4 引射器CFD仿真分析引射器结构虽然简单，但其内部流场比较复杂，引射流动实际上是一种复杂的粘性流动形式，属于高雷诺数、强剪切湍流射流.通过CFD软件可以观察引射器内的流场分布，并研究引射器各尺寸对于引射器工作特性的影响，进而对引射器进行优化改进.4.1 引射器仿真模型假设结合理论分析，为了简化模型，节省演算时间增加计算精确度，对引射器模型进行合理的假设，本课题所做的假设如下:1)将引射流体的侧向入口简化成轴向环形入口由于三维模型对计算机的配置要求较高，考虑到引射气体入口段流速与喷嘴出口段工作气体的流速相比很小，所以在优化模型中可以将引射流体的侧向入口简化成轴向环形入口，从而将引射器的结构简化成二维轴对称模型.2)将喷嘴进口时的初速度和引射口的初速度设为0由于工作和引射流体在进入引射器时的初速度与它们在混合室中的速度相比较是很小的，所以可以把该初始速度忽略不计.3)整个模拟过程为绝热过程本文主要研究气体的混合流动，因此，可以不需要考虑引射器壁面的散热.图6 引射器仿真压力场分布图7 引射器仿真速度场分布4.1 引射器数值模拟仿真图5是入口压力为 5.0bar，引射压力为 2.0bar，出口压力为2.4bar时引射器沿轴线方向的压力分布情况.可以发现，引射器内沿轴线分布压力变化较大，尤其是喷嘴部分，压力梯度最大.氢气从圆管进入喷嘴缩口一段距离接近喉口时，压力梯度开始急剧下降，伴随着速度的上升，图中可以看出，在扩口部分，氢气压力仍然在下降，说明氢气在喷嘴喉口达到临界速度，但喷嘴出口的压力低于理论设计时的喷嘴出口压力.在离开喷嘴出口截面后，即在锥形混合室中，氢气压力有一定的提升.在设计过程中，由于使氢气在离开喷嘴出口截面时的压力等于引射端压力，故在离开引射器喷嘴出口截面后的一段距离中，压力变化不大，而仿真结果显示这段距离氢气压力已经上升到大于引射端压力.氢气此后分别在锥形混合室接近圆柱形混合室部分和刚出混合室至扩压室一段距离有较大的压力提升.图6和图7分别是引射器仿真压力场分布以及引射器仿真速度场分布，从中可以看出，压力最小值出现在喷嘴扩口处，说明喷嘴尺寸设计符合理论设计要求，即氢气在喷嘴喉口处达到临界值，经过喷嘴扩口，氢气继续减压增速，压力进一步下降，在离开喷嘴扩口时，氢气压力值明显小于引射端入口压力值，随后进入预混合室、混合室以及扩压室氢气压力上升到一定值.5 总结本文分析了引射器的工作原理，以索科洛夫的计算方法为依据，假设流动为一维稳态流动，根据能量守恒质量守恒和动量守恒定理设计了应用于PEMFC的引射器.在此基础上研究引射器各工作参数对引射器工作的影响，并对其进行了CFD仿真分析.通过分析可知，工作流体入口压力和引射流体压力存在一个出口临界压力，当PC值大于临界压力时，引射比将随着压力PC的增大而减小，继续提高出口压力PC甚至可能导致引射比为负值(即部分工作流体会从引射口流出引射器)，然而，当PC小于临界压力时，引射比为最大值且保持不变，这个时候引射器达到给定工作流体和引射流体初始参数下的最佳工作能力.引射器的工作能力并不是简单的随入口压力的增大而变好或变坏.需要根据不同的情况即不同的引射压力和出口压力来单独研究.随着引射流体压力的增加，引射器的引射系数随之增大.虽然实际运行状况和理论计算存在一定偏差，但对引射器使用性能的研究具有很好的理论指导意义.参考文献:[1]衣宝廉.燃料电池——原理.技术.应用[M].北京:化工出版社，2003.[2]任庚坡.质子交换膜燃料电池性能仿真与水管理的实验研究[D].上海:上海交通大学，2008.[3]Paul Rodatz，AkinoriTsukada，Michael Mladek，LinoGuzzella.Efficiency Improvements by Pulsed Hydrogen Supply in PEM Fuel Cell Systems，15th Triennial World Congress，2002.[4]P.Rodatz，A.Tsukada，M.Mladek，et al.Proceedings of the 15th IFAC Triennial World Congress IFAC(2002).[5]王洪卫，王伟国.质子交换膜燃料电池阳极燃料循环方法[J].电源技术，2007，31(7):559－561.[6]索科洛夫ЕЯ，津格尔H M(著)，黄秋云(译).喷射器[M].北京:科学出版社，1977:17－78.。