Modeling And Optimizing Of High Temperature Proton Exchange Membrane Fuel Cell

The research on high-temperature proton exchange membrane fuel cell has become a hot spot recently because of not only its high energy efficiency, low noise, fast startup, zero pollution, etc, but also its high operating temperature, the endurance to CO of the catalyst is enhanced, the fuel processing system and external humidification system are simple.At first, the basic theory of high-temperature proton exchange membrane fuel cell is described and the mathematical models of computer simulation are introduced in the thesis, including the control equations of computational fluid dynamics (CFD), electrochemical reaction equations and the gas diffusion in the fuel cells. Secondly, the high-temperature proton exchange membrane fuel cell engine and its equipments are presented. According to the analysis and calculation, a scheme of the high temperature proton exchange fuel cell engine is designed.Thirdly, a three-dimensional model of single cell is built to study the differences between the high-temperature proton exchange fuel cell and the traditional one by using computer simulation techniques. The result showed that there was little liquid water in the high-temperature fuel cells, so there is no need to consider drainage issues during the design of the flow field and the uniformity of gas distribution is the point. The influences of design and operating parameters on the performance of fuel cell are studied, which showed that the thicknesses of gas diffusion layer and operating conditions has much affection on cell performance. With the increasing of the gas diffusion layer thickness, the membrane can absorb more water, which increased the cell performance. On the other hand, the polarization is severely with the thicknesses of gas diffusion layer increased, which made the cell performance depressed. So the thickness of gas diffusion layer has an optimal value in a certain range. The cell performance increased with the increase of operation pressure and fuel gas relative humidity.Finally, three simulation models are set up and optimized by using commercial CFD software in order to obtain the optimal channel dimensions and geometry. The results show that the dimensions and geometry of the channel appears to have significant influence on the gas distribution and cell performance. The fuel cell with the channel cross-section of trapezoidal performs better than that of the fuel cell with channel cross-section of rectangular. The fuel cell with different flow field of parallel straight channels and multi-serpentine channels are also modeled. The result is represented that the gas distribution is wicked in the multi-serpentine channel, which result to a poor cell performance and the performance of cell with parallel straight channels is better. Considering the academic calculation aforementioned and the simulation work, the parallel straight channels is the best design for high-temperature proton exchange membrane fuel cell.