质子交换膜燃料电池多物理量动态测量及性能优化研究

RESEARCH ON DYNAMIC MEASUREMENTS AND PERFORMANCE OPTIMIZATION OF PROTON EXCHANGE MEMBRANE FUEL CELL

王亚军

11649004

博士

机械工程

王海江

2020-06-03

2020-07-25

哈尔滨工业大学

深圳

燃料电池成本高和寿命不足是车用燃料电池产业化亟待解决的两大难题。为了提升燃料电池性能和缓解其寿命衰减，必须深入研究燃料电池的动态行为和失效机理，并提出实际可用的应对策略，尽可能地缓解电池性能和寿命的衰减。目前，国内外研究学者对实验级单电池的单一参数的原位测量进行了大量研究，没有同时对燃料电池内部的“气-水-热-电”的耦合行为进行研究，特别是对商业级电池或电堆内部多个物理量同时进行原位测量还未有公开文献报道。本文针对目前燃料电池测试存在的不足，研发了高精度燃料电池内部电流密度、温湿度和压强同时测量的原位动态测量系统，借助原位测量研究了操作条件对电池性能的影响，揭示了电池内部物理量的分布特性和典型失效现象的失效机理，并提出了性能优化和寿命衰减缓解措施。本文的主要研究内容如下：明确燃料电池原位动态测量系统的检测要求，研制了200 cm2 的商业级测试电堆，研发了36 分区电流密度、温湿度和压强检测双极板并给出了相应的检测原理和方案。根据传感器的信号采集类型研发了燃料电池内部多物理量的原位高精度测量系统，为后续燃料电池的动态测量和性能优化提供了研究基础。通过原位测量研究了不同操作条件对燃料电池性能的影响，对不同进气方式和湿度条件下电池内部的水热管理效果进行了评估，对典型工况下电池内部的电流密度、温湿、相对湿度、压强的分布特性进行了揭示和分析，并采用正交实验对典型工况下的操作条件进行了优化。研究表明燃料电池的最佳操作温度为70 C；气体的最优相对湿度为80%；在低电流密度下，采用逆流进气方式燃料电池具有更好的输出性能和内部一致性；而在高电流密度下，采用平行流的进气方式具有更好的输出性能和水热管理效果。在启动工况，最优温度操作条件为60 C，阴阳极进气相对湿度为60%，空气计量比为2.0；在其他运行工况下，燃料电池的最佳操作温度为70 C，阴阳极进气湿度为80%，空气计量比为2.5。结合原位动态测试对引起燃料电池失效的反极动态过程进行了深入研究，设计严密的对比实验全面揭示了抗反极膜电极的反极失效的机理，并对反极条件下燃料电池的相对湿度进行了优化，提出了抗反极膜电极的梯度化优化设计方法，用以提高燃料电池的反极耐久性。研究发现抗反极膜电极组件的失效是电子传导通路的破坏引起的，而不是IrO2失活。反极测试后阳极催化层、气体扩散层和双极板呈现不同程度腐蚀。反极情况发生时，燃料电池内相对湿度超过55% 对抗反极膜电极的耐久性不利。在保持IrO2催化剂含量相同时，通过梯度化设计增加高湿度区域的IrO2含量可有效提高燃料电池的抗反极耐久性。采用原位动态测量电池系统地研究了燃料电池的停机过程，对比分析了三种虚拟停机载荷对燃料电池内部一致性和电池寿命的影响，提出了组合停机策略的优化设计方法，用以优化停机过程和延长电池寿命。结果表明采用恒功率和恒电流的组合停机策略可以缩短停机时间，有效地减少停机过程的反向电流和阴极高电位，并且使电池获得良好的内部一致性。

The high cost and the poor durability are two main barriers to the large-scale commercialization of proton exchange membrane fuel cells. In order to improve the cell performance and enhance its durability, it is necessary to study the dynamic behavior and failure mechanism of fuel cells furtherly and put forward practical countermeasures to alleviate the degradation of cell performance and life as much as possible. At present, domestic and foreign researchers have conducted a large number of studies on the internal behaviors of small single fuel cells, however, without studying the coupling behavior in the fuel cell simultaneously. In particular, there is no published literature report on in-situ measurements of multi-physical parameters in a commercial-size fuel cell or fuel cell stack simultaneously.In this dissertation, an in-situ dynamic measurement system that suitable for current density, temperature, relative humidity and pressure measurements simultaneously in commercial-size fuel cells was developed. Adopting the in-situ measurement system, the effect of operating conditions on the fuel cell performance was studied, the internal behavior and failure mechanisms of the fuel cell were revealed, and the corresponding mitigation strategies were put forward. The main research work of this dissertation are as follows: The detection requirements of the fuel cell dynamic measurement system was identified based on the research purposes. The commercial fuel cell with an active area of 200 cm2 was developed. The segmented in-situ measurement bipolar plates were developed and the corresponding detection principles for current density, temperature humidity and pressure measurements were presented in detail. In addition, a high-precision data acquisition system for the fuel cell was developed, which provides a research basis for the subsequent dynamic measurements and performance optimization of the fuel cell.In addition, the influences of different operating conditions on the cell performance were researched via in-situ measurements. The hydrothermal management effect and coupling characteristics inside the cell were analyzed under different gas arrangements and gas relative humidities (RHs). The distribution characteristics of current density, temperature, relative humidity and pressure under different operating conditions were revealed and studied. Besides, the operating conditions under different operating modes were optimized by adopting the orthogonal experiments. The results show that the optimal operating temperature and gas RH of the cell are 70 C and 80%, respectively. Under low current density, the cell with counter-flow mode has a better performance and internal consistency. However, the cell in co-flow mode has a better performance and hydrothermal management effect under high current density. Under start-up operation, the optimal level of the fuel cell temperature is 60 C, the optimal level of RH of the inlet gases is 60% and the optimal level of air stoichiometric ratio is 2.0. Under other operating modes, the optimal level of the fuel cell temperature is 70 C, the optimal level of inlet gases RH is 80% and the optimal level of air stoichiometric ratio is 2.5.Moreover, the dynamic process of voltage reversal was studied systematically by employing the in-situ dynamic measurement system. The failure mechanism of reversal tolerant anode (RTA) was revealed through a series of rigorous experiments. Besides, the relative humidity that benefits the RTA durability during voltage reversal process was optimized. The optimization design method of RTA membrane-electrode assembly (MEA) was proposed based on the research findings for enhancing the cell durability. It was found that the failure of the RTA MEA was caused by the destruction of the electron conduction pathway, rather than the deactivation of IrO2. The catalyst coated membrane, gas diffusion layer and bipolar plate on the anode side were corroded in different degrees after the voltage reversal testing. An RH over 55% adversely affects the durability of RTA when hydrogen starvation occurs. While maintaining the same content of IrO2 catalyst, increasing the content of IrO2 in the high RH area by gradient design of RTA MEA can improve the voltage reversal durability of fuel cells effectively.Finally, the shutdown processes of the fuel cell were studied deeply adopting the in-situ dynamic measurement system. The shutdown processes under three kinds of shut-down loads were compared. The influences of different shut-down loads on the cell internal consistency and durability were evaluated. Also, the combined shut-down strategy was proposed for improving the cell internal uniformity and prolonging cell life. The results show that adopting the combined shut-down strategy of constant power load and constant current load can not only shortens the shut-down time, but also reduces the reverse current and cathode high potential in the cell effectively. Besides, the fuel cell also obtained a good internal uniformity when adopting the combined shut-down strategy.

质子交换膜燃料电池 多物理量 动态测量 性能优化 反极 停机

proton exchange membrane fuel cell multi-physical parameters dynamic measurement performance optimization voltage reversal shut-down

中文

联合培养

南方科技大学

王亚军. 质子交换膜燃料电池多物理量动态测量及性能优化研究[D]. 深圳. 哈尔滨工业大学,2020.