基于启停工况的质子交换膜燃料电池动态响应模型与计算方法研究

Polymer exchange membrane fuel cells (PEMFCs) have been known as one of the most clean and efficient power generation technologies because of their advantages such as low environmental impact, high power density and rapid start-up. It is a great challenge and urgent work to establish a dynamic model to study the operating principle for PEMFC. It comes at the same time involving multicomponent, multiphase and multidimensional flow in fuel cell process, accompanying by heat and mass transfer and electrochemical reaction, especially under variable working conditions. In the project we plan to study the attenuation influences of the startup-shutdown working condition to the performance of PEMFC, mainly including the following three aspects. (1) Based on the three-dimensional multiphysics multiphase transport model and collaborative simulation platform, a dynamic response model will be established with startup-shutdown operating condition. (2) By the finite element method-weighted upwind finite volume method, we design an efficient and stable numerical method to solve the unsteady nonlinear strong coupled differential equations, combining with the multigrid, domain decomposition, parallel and other methods. (3) Using the above model and algorithm, we analyze the influence of startup-shutdown operating condition to the fluid flow, the transfer of chemical composition, and the changes of current density distribution. Through the research of the project, we can clarify the influence factor of the attenuation theoretically, give the method of reducing the attenuation and provide reliable theoretical basis for optimizing the design fuel cells.

质子交换膜燃料电池（PEMFC）以其零排放、高效率、快启动等优点而被公认为本世纪首选的洁净高效发电技术之一。PEMFC经常处于变工况状态，内部多相流现象复杂，建立适当的动态数学模型，研究电池工作原理，是国内外开发新型能源急迫而又具挑战性的基础研究工作。本项目拟采用数值模拟的方法研究启停工况对PEMFC性能衰减的影响，主要包含以下三方面：1）基于三维非稳态多相模型与协同仿真平台，建立启停工况下PEMFC的动态响应模型；2）基于有限元-加权迎风有限体法，并采用多重网格、区域分解、并行等方法，设计高效稳定的计算方法用以求解模型中的非定常强耦合非线性微分方程组；3）利用上述模型与算法，分析启停工况对电池内流体流动、化学组分传递、电流密度分布等变化的影响。通过本项目的研究，从理论上阐明启停工况对电池性能衰减的影响因素，分析可能降低启停衰减的方法，为优化燃料电池的设计和运行提供可靠的理论依据。

燃料电池动态参数模型的特点主要包括：模型中方程的对流占优性及系数的非线性, 导致常规求解方法不易收敛；电化学反应所对应的方程组中的源项彼此相互强耦合; 求解过程涉及的大，尤其是对于电池堆模型的求解。因此找出高效稳定的计算方法必不可少。针对上述问题，本项目取得了以下成果：1）采用有限元-迎风有限体方法以及有限元-加权迎风有限体方法解决了燃料电池模型中的强对流占优问题，提高了数值模拟的计算精度，并将两重网格方法用于该类方程的求解，设计出高效稳定的离散格式，同时给出了该算法的收敛性及误差估计等相关理论证明。 2）对“4-cell”的模块化甲醇燃料电池堆进行了试验测试研究，预测了多个模块间连接的额外功率损耗，该电池堆可以自由组合，进行设计和制造，可应用于各种电子设备。3）给出了PNP模型和PNP-Stokes耦合模型的半离散与全离散格式及收敛性分析，从理论上与数值上验证了混合有限元方法可达到最优阶，提高了计算精度。