Optimization Of Interconnect Structure Of Solid Oxide Fuel Cell Based On Multi-physical Modeling

Solid oxide fuel cell(SOFC)is a high-efficiency,clean,promising energy conversion device.The challenges in commercialization are the improving power density,long-term operating stability and service life.The poor stability of SOFC is mainly induced by uneven distribution of the gases,which will result in uneven temperature distribution and uneven stress distribution,leading to cracks within the cells,materials failure or other structural damage.The gas distribution of SOFC depends on flow structure and is affected by a variety of internal physical and chemical processes.Solid oxide fuel cells are small in scale,and various physical quantities in the cell interact with each other.It is difficult to study the coupling physics mechanism using experimental method.Moreover,it takes long time and high costs.Multi-physics simulation is an efficient method to study SOFC and design the interconnect structure.In this thesis,mass conservation,momentum conservation,charge conservation and electrochemistry are coupled to establish a 3D numerical model for anode-supported SOFC based on the finite element analysis software COMSOL.The multi-physical model validated with experimental data is used to explore pressure distribution,gas distribution,current distribution and performance of SOFC with different flow structures.The channel size will be optimized and a new interconnect flow structure will be designed to obtain uniform gas distribution.Experiments will be conducted to test the performance of the new designed structure.For channels optimization,it mainly involves the balance between gas diffusion and conductivity.The optimization of channel size considers the effect of channel width and height on gas transport,and the influence of contact resistance on the charge transfer.Based on an anode-supported SOFC provided by Huatsing co.Ltd,a three-dimensional multi-physical model was established and validated.The performance of cells with different width and height are compared to find out the optimal size and corresponding ratio.Considering different situation of assembly,performance of cells with different contact resistance are analyzed to illuminate the influence of contact resistance.For flow structure of interconnect plate,it influences the uniformity of gas distribution among different channels.This study explores the impact of the flow structure before channels on gas flow with main attention of overall electrical performance,uniformity of gas distribution and current distribution.After a comparison of pressure distribution,gas distribution,current distribution and cell performance between the unit cell structure for test and the flow structure in a stack,the reason for performance degradation of the unit cell structure is clear.The position of inlet and outlet pipe as well as the narrow flow zone before channels influence the gas flow,resulting in non-uniform gas distribution.The accompanying non-uniform current density distribution leads to lower overall cell performance.Based on the conclusions,a new diversion structure is designed based on the current flow structure for single-cell test.The good performance of the new structure is obtained by analysis of multi-physical modeling and the experiment.