Performance Research And Structure Optimization Of Baffled Serpentine Flow Field In Fuel Cells

In recent years,with the deepening of the earth's atmospheric pollution and fossil fuel crisis,clean and efficient new energy research upsurge has been set off worldwide.In a variety of new energy technologies,hydrogen energy has rapidly become the focus and hotspot of people's research because of its advantages of cleanliness,efficiency and large reserves.As the main way of hydrogen energy utilization,fuel cells can not only replace traditional engines to reduce automobile emissions and environmental pollution,but also be widely used in military and civil fields as energy conversion devices in distributed power generation system.As an important component of hydrogen fuel cell,bipolar plate accounts for about 80% of the total mass and 40%of the total cost of fuel cell stack.The optimization of bipolar plate has always been the focus of fuel cell performance research.The structure of the channel is an important factor affecting the performance of the bipolar plate.Reasonable channel layout and channel size can fully improve the concentration distribution of reaction gas,promote the diffusion of reaction gas to the diffusion layer,improve the reaction rate of fuel cell,and thus improve the power density of fuel cell.At the same time,the proper flow channel layout and size can also timely discharge the liquid water generated by the reaction from the flow channel,so as to avoid water flooding affecting the life of fuel cell.In this thesis,based on the previous research on flow channel baffle,the performance of fuel cell was studied by installing baffle in multi-channel serpentine flow field,and the optimization and improvement measures were proposed.First of all,at home and abroad for proton exchange membrane fuel cell flow have investigated the current situation of the study,especially to the port configuration form and a lot of research on size structure,then designed a multi-channel serpentine flow field,and on the basis of multi-channel serpentine flow field with baffle flow field,research baffle for serpentine flow field effects on the electrochemical properties of the fuel cell.Then,COMSOL Multiphysics was used to build a simulation model of baffle snake-like flow field in fuel cells,and the calculation assumptions,boundary conditions and physical field parameters were defined in the simulation.In order to ensure the reliability and accuracy of the model,the mathematical model was verified by using parallel dc channel and multi-channel serpentine channel fuel cell single cell test rig,and the experimental results were compared with the numerical simulation results.Finally,the design of baffle snake flow field is studied and optimized from five main aspects(number of baffle installation,installation position of baffle,cross-section shape of baffle,size of baffle and inlet speed).Number of baffles are installed in the different influence on the performance of the fuel cell research process,the calculation of the same assumptions,boundary conditions and physical parameters,the number of damper under the working voltage of 0.5 V by3,5,7,9 of the fuel cell performance study and contrast found that installing a nine baffle in the flow field,fuel cells have the best electrochemical performance.On the basis of the optimization of baffle number,9 baffle fuel cells were taken as the research object,and baffle installation positions were set as three schemes: installation below the flow passage,above the flow passage,and cross-installation below and above the flow passage.The different installation positions of baffle were compared and analyzed.The results show that the fuel cell with baffle mounted above the flow channel has better electrochemical performance under the same parameters.Under the condition of the same parameters,the maximum current density of fuel cells with three different baffle installation positions is in the order of baffle installation above the flow passage > cross installation > below the flow passage.The maximum power density shows the same rule.At the same time,by comparing the oxygen concentration distribution and water concentration distribution at the baffle of fuel cell with different baffle installation positions,it is found that the fuel cell with baffle installed above the flow passage has better gas distribution characteristics and stronger drainage capacity at the baffle.To baffle in the study of cross section shape,under the condition of ensure the same block ratio,respectively for square,rectangular panel,circular baffle,baffle are octagon baffle,trapezoidal baffles are analyzed,the results found that baffle shape of square,baffle the maximum increase of the performance of fuel cell,the electrochemical performance of the fuel cell is better;Oxygen is more evenly distributed;Better drainage at the baffle.After the baffle shape was determined,the study on the influence of baffle with different blocking ratio and thickness on the performance of fuel cell found that when the square baffle side length was set as 0.79 mm and the thickness was 0.4mm,the baffle could improve the performance of fuel cell best.When the intake speed is set to 3m/s,it is enough to give full play to the performance of the baffle fuel cell and meet the intake requirements of the fuel cell.