Study On Structure And Performance Optimization Of Planar Solid Oxide Fuel Cell

With the increasing demand for energy and the exhaustion of fossil energy,solid oxide fuel cell(SOFC)has attracted extensive attention due to the advantages of low pollution and high efficiency.Anode supported planar SOFC was taken as the research object to study the influence of macro structure and operating conditions on the performance of the cell in this paper.Heat and mass transfer,fluid flow and electrochemical reaction were coupled.A three-dimensional non-isothermal model was established in COMSOL,and the solution calculation was carried out.The output performance,temperature variation and gas diffusion were analyzed and discussed,and the variation law was summarized.Specific studies are as follows.(1)Aiming at the problem of uneven distribution of reactants in porous electrode and impaired output performance,the influence of structural parameters on the operation of SOFC was studied.The new connector structures and cathode structures were designed.The effects of connector rib width,cell pitch width,connector arrangements,channel length and height on the comprehensive performance of SOFC were also studied.It was found that for anode supported SOFC,the loss can be effectively reduced by using smaller rib width and cell pitch width on the cathode side and larger rib width and cell pitch width on the anode side,which increases the maximum output power density of the cell by 20%.The uniformity of oxygen concentration distribution can be improved by increasing the thickness of cathode diffusion layer in the area covered by the connector,and the maximum output power density of the cell is increased by 29.14%.Output performance is improved by increasing the height of the flow channel,but optimization is capped at 1.5 mm.As the length of the flow channel increases,the output performance of SOFC decreases significantly.(2)The influence of operating conditions and parameters on the operation of SOFC was studied aiming at the problem of large temperature rise and difficult cell sealing during operation.New gas flow modes were designed.In addition,the effects of heat dissipation boundary,stack number and gas flow rate on the operating performance of SOFC were also studied.The results show that the overall temperature rise of SOFC stack can be reduced by 26 K by changing the flow mode.The number of SOFC stack layers will affect the relative heat dissipation area of each cell,and then affect the temperature distribution of the stack.With the increase of layers,the resistance generated by the connector will also increase,and the loss in the process of current collection and conduction will increase.As the fuel flow rate increases,the output current and power gradually increase,and the overall temperature of the cell gradually increases,but there is an upper limit to this increase.As the air flow rate increases,the output performance gradually improves,and the overall temperature of SOFC gradually increases and then decreases.When the air flow rate exceeds 3 m/s,the reaction reaches saturation,and further increasing the air flow rate mainly plays a role in reducing the temperature.(3)Considering the operating cost and engineering practicability of SOFC,the performance of using methane as fuel was studied to provide guidance for practical application.With the change of voltage,the trends of species concentration,reaction rate,current density and temperature of SOFC change significantly before and after0.7 V,which is related to the relative intensity of methane reforming reaction and electrochemical reaction.At high operating voltage,the electrochemical reaction is weak and methane reforming reaction is dominant,while at low operating voltage,the electrochemical reaction is sharply enhanced.