Multiphysics Simulation And Performance Analysis Of MOLB-type SOFC

Due to the substantial growth of population round the world,the problems of environmental pollution and energy shortage become more and more serious.The development and utilization of new alternative energy sources are imminent.As an efficient and clean energy conversion device,solid oxide fuel cell(SOFC)has become the fourth generation of generating electricity after hydropower,thermal power,and nuclear power.The research object of this paper is the mono-block-layer built type(MOLB-type)SOFC.Based on the principle of electrochemical kinetics,COMSOL is used to couple the multiphysics of MOLB-type SOFC model,from species transmission,temperature distribution,current density,fuel utilization,etc.The analysis of the built model is carried out in various aspects,and the main research contents are as follows.Firstly,the mathematical models of the MOLB-type SOFC and planar SOFC in steady state are established,and the distribution of species,temperature,current density and polarization loss is analyzed.It is found that the distribution of current density of the MOLB-type SOFC is more uniform,and the overall value is higher.There is no concentration polarization phenomenon at high current density of MOLBtype SOFC and the overpotential is smaller than planar SOFC.The maximum temperature difference of MOLB-type SOFC is higher than that of planar SOFC,but the position of maximum temperature is above the anode slope,which is convenient for heat transfer through the interconnect.The performance difference of MOLB-type SOFC with different structural parameters is obtained.The increase of cell length can improve the fuel utilization,but when the cell length is gradually increased from 40 mm to 100 mm,the average increase of fuel utilization decreases,which is 36.09%,22.26% and 14.09%respectively.The increase of porosity in the porous electrodes can increase the diffusion of hydrogen to the reaction surface,but the increase of electrical performance decreases sharply at high porosity.Increasing the flow channel angle can weaken the "corner effect",reduce the ohmic loss and heat load,and reduce the average value of maximum temperature difference by 6.18%.But when the angle increases from 135° to 150°,the decrease of average current density increases sharply,and the optimal channel angle is 135°.Finally,the mathematical model of MOLB-type SOFC with different operation parameters is solved,and the changes of species distribution,temperature distribution,fuel utilization and electrical efficiency are analyzed.The results show that the oxygen mole fraction in cathode decreases by 1.46% when the fuel inlet velocity increase from 0.5 m/s to 0.75 m/s,which enhances the diffusion of oxygen to the reaction surface,but leads to a sharp decrease in fuel utilization and electrical efficiency.The hydrogen at the anode outlet decreases by 8.12%,4.05% and 2.83%respectively when the air inlet velocity increases from 1.0 m/s to 4.0 m/s,which improves the fuel utilization and avoids the concentration polarization.However,the improvement effect of high speed on the electrical performance and fuel utilization will be weakened.When the mole fraction of oxygen in the air at the cathode inlet increases from 0.11 to 0.41,the hydrogen at the anode outlet decreases by 26.3%,and the average current density and power density of MOLB-type SOFC are improved,which is more obvious when the mole fraction of oxygen is small.