Research On Water Management Of Air-cooled Fuel Cells Based On Anode Exhaust And Cathode Heat Dissipation Strategies

A Proton exchange membrane fuel cell(PEMFC)is a power generation device that converts hydrogen energy directly into electric energy.It has the advantages of zeroemission and low noise and is considered an ideal new energy technology solution.Aircooled PEMFC is an open cathode structure that sends air to the cathode and takes away the heat generated by the electrochemical reaction through the forced convection of DC fans.There is no need for redundant auxiliary components,so it has a more streamlined system structure and lighter weight and broad prospects in electric UAV and backup power supply.However,due to the simple structure and the direct exposure of the cathode to the ambient air,there are some problems in further development of the air-cooled PEMFC,such as a single controllable amount,difficulty in water management,and easy to be affected by the environment,which limit its further commercial development.The performance of air-cooled PEMFC is directly related to its internal water content.A good water management strategy can effectively improve its performance and life.Based on the water management strategy of air-cooled PEMFC,research is carried out from both sides of the anode and cathode.The main contents are as follows:Firstly,a dynamic mechanical model of air-cooled PEMFC is established,including three sub-models: water transfer,electrochemistry,heat generation-dissipation.An innovative solution is proposed to calculate the internal water content of the cell.In order to verify the accuracy of the model,dynamic experiments are designed and carried out under multiple conditions,and the experimental data are compared with the simulation data.The results show that the simulation data can fit the experimental data well,and the error is less than 2%.Based on verifying the accuracy of the model,the factors affecting the output performance of air-cooled PEMFC are analyzed theoretically,providing a theoretical basis for future experiments.Secondly,water management characteristics on both sides of the anode and cathode of air-cooled PEMFC are investigated,including the characteristics of anode exhaust and cathode heat dissipation characteristics.By comparing the AC impedance spectra corresponding to different anode exhaust strategies,it is found that the curve characteristics of the low-frequency band of AC impedance spectra can be used to determine whether the anode needs to exhaust gas.Comparative experiments in different environments show that the cathode heat dissipation strategy with fixed reference temperature does not have environmental adaptability.The concept of the control domain of the cathode heat dissipation strategy is innovatively proposed,and the upper bounds of the control domain under different loads are measured experimentally.Finally,designing and implementing an anode and cathode water management strategy for air-cooled PEMFC is completed from the perspective of performance optimization and environmental adaptability.Based on the curve characteristics of the low-frequency band of the AC impedance spectrum,the anode exhaust strategy based on mass transfer arc identification is innovatively proposed.Based on the concept of the control domain,the cathode cooling strategy based on the restricted disturbance observation method is innovatively proposed.An online AC impedance measuring device with multiple frequency points is developed,providing a hardware basis for implementing the proposed strategy.Finally,verification experiments are carried out.The results show that the proposed water management strategy can achieve the established control objectives under fixed and variable load conditions,effectively improving the system output performance.At the same time,its control effect has solid environmental adaptability,which is of great significance for the commercial application of air-cooled fuel cells.