Flow Field Improvement And Design Of Proton Exchange Membrane Fuel Cell

With the rapid development of global economy and the background of "carbon neutrality",the development and utilization of clean energy has become a research hotspot.Hydrogen energy is considered as the "ultimate energy" in the future and the most promising renewable energy.Proton exchange membrane fuel cell(PEMFC)is a kind of energy conversion device which can directly convert chemical energy in hydrogen into electric energy.Because PEMFC has the advantages of low operating temperature,high efficiency,fast start-up,zero pollution and so on,it has a broad application prospect in transportation and power generation.At present,critical issues such as water management and output performance limit the commercial use of PEMFC.Flow field,as the key structure of PEMFC,is responsible for the transport of reactants and the discharge of products.Optimization and new design of flow field can improve the water management and thermal management of PEMFC,improve the uniformity of internal distribution and power output performance.Numerical simulation is one of the main research methods of PEMFC,which can realize the visualization of PEMFC and improve the efficiency of flow field development.In order to improve the comprehensive performance of PEMFC,this paper designed a variety of improved flow fields and new flow fields,and carried out numerical simulation for PEMFC with different flow fields.The main research work is as follows:Firstly,a steady-state,two-phase,non-isothermal numerical simulation model of PEMFC with parallel flow field was established,and the effects of horizontal and vertical inlets on the performance of parallel flow field were studied.The results show that the reaction gas flow resistance of the parallel flow field with the horizontal inlet is smaller and the transmission capacity is stronger.The peak power of the parallel flow field with the horizontal inlet is 9.49%higher than that of the parallel flow field with the vertical inlet.The distribution of components in PEMFC with parallel flow field with horizontal inlet is more uniform.Secondly,a new flow field with spiral structure is proposed,and a comparative study is made on the spiral flow field and the improved parallel flow field with spiral structure.The results show that the spiral structure increases the peak power of traditional parallel flow field PEMFC by 1.46% and 7.22% respectively,and relieves the problem of low oxygen concentration in some internal areas.The performance of the improved parallel flow field increases with the increase of the spiral structure,and its polarization curve is between the parallel flow field and the serpentine flow field.In the spiral flow field,the inlet channel and outlet channel are arranged alternately,and the distribution of gas pressure,oxygen,hygrogen and current density in PEMFC is more uniform than that in the traditional flow field.Then,in order to improve the internal uniformity of PEMFC,a new three-dimensional flow field is designed.The flow field has two layers,and the gas flow direction is divided into two directions: perpendicular and parallel to the gas diffusion layer.Numerical simulation method is used to compare the internal distribution uniformity of the new three-dimensional flow field and the traditional flow field.The results show that the inlet and outlet pressure drop of the new three-dimensional flow field is much smaller than that of the traditional flow field with the same size,and the parasitic loss is reduced.Compared with parallel flow field and serpentine flow field,the new three-dimensional flow field improves the uniformity of gas pressure distribution,water distribution and reactant distribution in PEMFC.Finally,the conclusion of flow field research in this thesis is summarized and the prospect is put forward.