质子交换膜燃料电池组水管理研究

介绍了水管理对质子交换膜燃料电池组的重要性，对当前主要采用的外增湿、内增湿、自增湿技术进行综述，认为内增湿能为电池提供有效供水、减轻了电池组的体积和重量，具有良好的实用性。分析了双极板不同流场排水能力和动态排水技术，并对质子交换膜燃料电池水管理提出一些建议。     

质子交换膜燃料电池自增湿研究进展

概述了质子交换膜燃料电池自增湿研究状况，指出自增湿的出发点是有效利用电池阴极过程生成水。综述了薄电解质膜、新型自增湿膜、自增湿流场结构三种方法的研究进展及适用空间。对自增湿技术发展前景进行了探讨。     

车用氢燃料电池专用空压机

<正>车用氢燃料电池系统主要包括:电堆子系统、氢气供应子系统、空气供应子系统、热管理子系统、水管理子系统等五个子系统。空气供应子系统成本约占燃料电池系统成本的20%,能耗约占燃料电池输出功率的20%～30%。车用氢燃料电池专用空压机是燃料电池空气供应子系统的核心部件,通过对进堆空气进行增压可以提高燃料电池的功率密度和效率。车用氢燃料电池空压机     

小型质子交换膜燃料电池的增湿技术研究

分析了PEMFC电池内部水的生成和转移过程，列举了各种增湿方法，指出了几种外增湿法对小型氢空质子交换膜燃料电池进行增湿的优缺点和对电池性能的影响。     

空冷型PEMFC电源系统热耦合实验研究

空冷型质子交换膜燃料电池(PEMFC)电源系统中燃料电池系统和金属储氢器的热耦合管理对系统会产生重要的影响。本文通过实验分别研究将金属储氢器前置和后置这两种与燃料电池系统不同的耦合方式对燃料电池输出性能、单电池电压的均衡性以及风扇功耗的影响。结果表明,这两种不同的耦合方式对燃料电池输出性能、单电池电压的均衡性影响很小,但是对风扇功耗的影响比较明显。这主要是由于储氢器前置时空气先经过储氢器表面冷却再进入电堆,这有利于减少电堆散热所需的空气流量,从而降低风扇功耗。因此储氢器前置有利于降低系统辅助功耗,提高系统效率。     

蒸发冷却系统的能量流模型研究及其优化

为了解决蒸发冷却系统求解过程繁杂的问题,本文通过引入热阻、热动势,从热量输运的驱动力和阻抗的角度对蒸发冷却系统建立系统的能量流模型来描述系统中热量的整体输运规律,进而建立了系统性能与运行参数、结构参数的直接物理联系。利用新建立的能量流模型研究了空气预冷器里水-空气热容量流比值β、空气预冷器进口空气状态、用户换热器用户侧进水参数对系统的制冷能力及系统COP的影响。计算结果表明:在空气预冷器里水-空气热容量流比值为1附近时,系统制冷能力与系统COP取得极值,但二者不可能同时达到最优;较低含湿量、较高干球温度、用户换热器用户侧较高的进水温度、较高的进水流量均有利于增加系统的制冷能力和系统的COP。本文新建立的能量流模型,对蒸发冷却系统的性能分析及优化设计具有良好的准确性与便捷性。     

具有闭塞端阳极的燃料电池内液态水积聚研究

具有闭塞端的燃料电池阳极侧水的积聚是制约电池性能提高的关键难题。传统的宏观两相模型流道内普遍采用气液两相雾状流的假设,严重低估电池内水淹程度。文章采用毛细压力流道拓展模型,建立了二维、两相流、非等温数学模型,清晰地展示出二维空间的液态水传递和分布的特性,得到如下信息:沿流动方向液态水的饱和度不断升高,流道末端易发生水淹,阳极侧末端液态水的饱和度大于阴极侧。     

计及碳交易和需求响应的虚拟电厂低碳经济调度

为实现虚拟电厂的低碳经济运行,提出了一种考虑阶梯式碳交易和综合需求响应的虚拟电厂低碳经济调度方法。首先,研究多元柔性负荷的运行特性,建立了负荷侧综合需求响应模型;其次,在建立电转气两阶段运行模型基础上,引入氢燃料电池提高氢能利用效率;然后,将阶梯碳交易机制引入计及需求响应的虚拟电厂优化调度中,并建立了虚拟电厂低碳经济调度模型。最后,通过仿真分析表明所提方法和模型在提高系统运行灵活性的同时,改善了系统的经济性和碳排放水平。     

DF4C型机车中冷器CFD性能仿真分析

为了大幅度减少试验工作量建立了中冷器的CFD计算模型,采用标准k—ε湍流模型对中冷器的湍流流动和换热进行了仿真计算,对增压空气侧阻力性能和空气散热量进行了数值分析。仿真计算值与试验测试数据趋势吻合良好,该仿真方法可以有效地进行中冷器结构参数变化对流动传热性能的影响研究,有利于缩短设计周期和减少设计成本。     

间接内重整固体氧化物燃料电池的建模与仿真

建立了一维基于催化涂层重整器的间接内重整固体氧化物燃料电池的动态数学模型.在组分和能量守恒的基础上,考虑了电化学模型,建立了基于分布集总参数技术和模块化思想的间接内重整固体氧化物燃料电池的仿真模型.该模＃型不仅能反映燃料电池的分布参数特性,还可以满足动态仿真的需求.利用该模型分析了某一工况下固体氧化物燃料电池的稳态性能,并进行了动态过程的仿真,结果证明该模型可以反映间接内重整固体氧化物燃料电池的基本性能.     

Dynamic modeling of a proton exchange membrane fuel cell system with a shell-and-tube gas-to-gas membrane humidifier

The proton exchange membrane fuel cell (PEMFC) system with a shell-and-tube gas-to-gas membrane humidifier is considered to be a promising PEMFC system because of its energy-efficient operation. However, because the relative humidity of the dry air flowing into the stack depends on the stack exhaust air, this system can be unstable during transients. To investigate the dynamic behavior of the PEMFC system, a system model composed of a lumped dynamic model of an air blower, a two-dimensional dynamic model of a shell-and-tube gas-to-gas membrane humidifier, and a one-dimensional dynamic model of a PEMFC system is developed. Because the water management during transient of the PEMFC system is one of the key challenges, the system model is simulated at the step change of current. The variations in the PEMFC system characteristics are captured. To confirm the superiority of the system model, it is compared with the PEMFC component model during transients.     

Design of an air humidifier for a 5 kW proton exchange membrane fuel cell stack operated at elevated temperatures

Air humidification is a crucial issue for superior performance of proton exchange membrane fuel cell (PEM fuel cell) stacks. In this work, an air humidifier is proposed for a 5 kW PEM fuel cell stack working at elevated temperatures, e.g., 90–95 °C. The high temperature coolant exiting the stack is utilized to pre-heat the air in the heat exchanging tubes of the humidifier, and the heated air is humidified with deionized water supplied by a nozzle fixed in a top cavity. Both the tubes and the nozzle are properly designed to ensure sufficient heat transfer and superior atomization. Humidification performance is evaluated under different operation conditions. The nozzle is able to inject well-atomized water with uniform droplet diameter. With the variation of inlet air flow rate, the relative humidity (RH) of the outlet air increases at the beginning, then decreases gradually due to the attenuation of dew point (DP) temperature. However, the humidification performance can be improved when higher temperature deionized water is injected or high temperature coolant is supplied. At a coolant temperature of 95 °C, the outlet air DP temperature is maintained over 80 °C with 25 °C injection water. Moreover, better humidification performance is achieved when the injection water flow rate is controlled according to the working conditions of the stack.     

Analysis of the water and thermal management in proton exchange membrane fuel cell systems

Water and thermal management is essential to the performance of proton exchange membrane (PEM) fuel cell system. The key components in water and thermal management system, namely the fuel cell stack, radiator, condenser and membrane humidifier are all modeled analytically in this paper. Combined with a steady-state, one-dimensional, isothermal fuel cell model, a simple channel-groove pressure drop model is included in the stack analysis. Two compact heat exchangers, radiator and condenser are sized and rated to maintain the heat and material balance. The influence of non-condensable gas is also considered in the calculation of the condenser. Based on the proposed methodology, the effects of two important operating parameters, namely the air stoichiometric ratio and the cathode outlet pressure, and three kinds of anode humidification, namely recycling humidification, membrane humidification and recycling combining membrane humidification are analyzed. The methodology in this article is helpful to the design of water and thermal management system in fuel cell systems.     

Experimental study on dual recirculation of polymer electrolyte membrane fuel cell

Durability and start-up ability in sub-zero environment are two technical bottlenecks of vehicular polymer electrolyte membrane (PEM) fuel cell systems. With exhaust gas recirculation on the anode and cathode side, the cell voltage at low current density can be reduced, and the membrane can be humidified without external humidifier. They may be helpful to prolong the working lifetime and to promote the start-up ability. This paper presents an experimental study on a PEM fuel cell system with anodic and cathodic recirculation. The system is built up based on a 10 kW fuel cell stack, which consists of 50 cells and has an active area of 261 cm². A cathodic recirculation pump and a hydrogen recirculation pump are utilized on the cathode and anode side, respectively. Key parameters, e.g., stack current, stack voltage, cell voltage, air flow, relative humidity on the cathode side, oxygen concentration at the inlet and outlet of the cathode side, are measured. Results show that: 1) with a cathodic recirculation the system gets good self-humidification effect, which is similar to that with an external humidifier; 2) with a cathodic recirculation and a reduction of fresh air flux, the cell voltage can be obviously reduced; 3) with an anodic recirculation the cell voltage can also be reduced due to a reduction in the hydrogen partial pressure, the relative humidity on the cathode side is a little smaller than the case with only cathode recirculation. It indicates that, for our stack the cathodic recirculation is effective to clamp cell voltage at low current density, and a self-humidification system is possible with cathodic recirculation. Further study will focus on the dynamic model and control of the dual recirculation fuel cell system.     

Two dimensional dynamic modeling of a shell-and-tube water-to-gas membrane humidifier for proton exchange membrane fuel cell

Water management is a crucial factor in determining the performance of proton exchange membrane fuel cell (PEMFC) for automotive application. The shell-and-tube water-to-gas membrane humidifier is useful for humidifying the PEMFC due to its good performance. Shell-and-tube water-to-gas membrane humidifiers have liquid water on one side of the tube wall and a dry gas on the other. In order to investigate humidifier performance, a two-dimensional dynamic model of a shell-and-tube water-to-gas membrane humidifier is developed. The model is discretized into three control volumes – shell, tube and membrane – in the cross-sectional direction to resolve the temperature and species concentration of the humidifier. For validation, the dew point temperature of the simulation result is compared with that of experimental data and shows good agreement with only a slight difference. The distribution of humidification characteristics can be captured using the discretization along the air-flow direction. The humidification performance of two different flow configurations, counter and parallel, are compared under various operating conditions and geometric parameters. Finally, the dynamic response of the humidifier at the step-change of various air flow rates is investigated. These results suggest that the model can be used to optimize the inlet flow humidity of a PEMFC.     

Development of the novel control algorithm for the small proton exchange membrane fuel cell stack without external humidification

Small PEM (proton exchange membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feed-forward structure is defined and realized using a microcontroller. The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using a dual closed loop with a static feed-forward structure, thereby improving system efficiency and operation stability. The validity of the proposed method is confirmed by experiments using a 150-W PEM fuel cell stack. We expect the proposed algorithm to be widely used for controlling small PEM fuel cell stacks.     

Studies on the cathode humidification by exhaust gas recirculation for PEM fuel cell

For high efficiency and long durability of proton exchange membrane fuel cells (PEMFCs), polymer electrolyte membranes should be kept wet. Reactant gases should be humidified on this account. For the humidification, the PEMFC system uses an external or internal humidifier as a part of balance of plants (BOPs). However, external humidifiers have many disadvantages such as parasitic power loss, system complexity, high cost and bulky volume. As such, efforts have been made to remove the external humidifier or replace it with an advanced humidifier. In this work, to remove a humidifier, humidification by exhaust gas recirculation is investigated by theoretical analysis and experiments with 5-cell stack of an active area 250 cm². In the theoretical analysis, species conservation equations and energy conservation equation are solved to obtain the O₂ concentration, stoichiometric ratio, humidity ratio, temperature, amount of condensed water and so on. With the theoretical results, experiments with 5-cell, 250 cm² fuel cell stack were carried out in order to analyze the stack performance at the theoretical conditions of the cathode process stream of exhaust gas recirculation.     

Improving dynamic performance of proton-exchange membrane fuel cell system using time delay control

Transient behaviour is a key parameter for the vehicular application of proton-exchange membrane (PEM) fuel cell. The goal of this presentation is to construct better control technology to increase the dynamic performance of a PEM fuel cell. The PEM fuel cell model comprises a compressor, an injection pump, a humidifier, a cooler, inlet and outlet manifolds, and a membrane-electrode assembly. The model includes the dynamic states of current, voltage, relative humidity, stoichiometry of air and hydrogen, cathode and anode pressures, cathode and anode mass flow rates, and power. Anode recirculation is also included with the injection pump, as well as anode purging, for preventing anode flooding. A steady-state, isothermal analytical fuel cell model is constructed to analyze the mass transfer and water transportation in the membrane. In order to prevent the starvation of air and flooding in a PEM fuel cell, time delay control is suggested to regulate the optimum stoichiometry of oxygen and hydrogen, even when there are dynamical fluctuations of the required PEM fuel cell power. To prove the dynamical performance improvement of the present method, feed-forward control and Linear Quadratic Gaussian (LQG) control with a state estimator are compared. Matlab/Simulink simulation is performed to validate the proposed methodology to increase the dynamic performance of a PEM fuel cell system.