阴极相对湿度对PEMFC电解质水含量及性能的影响

Effect of cathode relative humidity on membrane water content and performance of PEMFC

质子交换膜燃料电池(PEMFC)工作过程中必须确保电解质的充分水合,且要避免凝结的液态水阻塞传质通道。为探究进气相对湿度对PEMFC电解质水含量及输出性能的影响,提出了阴极进气水含量(CIWC)模型。该模型考虑了膜电阻受温度和水含量的影响,推导了电解质水含量计算公式,将CIWC模型耦合进计算流体力学软件Fluent中进行计算。搭建了燃料电池测试平台,在工作温度为60℃,阳极相对湿度100%,阴极相对湿度50%、75%、100%工况下进行实验。将CIWC模型、Fluent内置模型的仿真值与实验值进行比较,并分析阴极侧电解质水含量、膜的电导率、水的摩尔分数分布。结果表明:当阴极相对湿度50%,电压为0.739 V时,CIWC模型精度比Fluent模型提高了17.67%;当阴极相对湿度100%时,CIWC模型与实验值最大相对误差为5.66%。随着阴极进气相对湿度的增加,电解质水含量在电压为0.75 V时不断增大,电压为0.6 V时趋于饱和,从空气入口到出口,电解质水含量、质子电导率、催化层水的摩尔分数沿着流场方向逐渐增大;当阴极相对湿度75%时,电解质水含量分布更均匀,电池输出功率密度最高为272.08 mW/cm^(2)。

The proton exchange membrane fuel cell(PEMFC)must ensure adequate hydration of the proton exchange membrane during operation while preventing condensed liquid water from blocking the mass transfer channel.To analyze the effect of cathode relative humidity on membrane water content and PEMFC's output performance,a cathode inlet water content(CIWC)model was developed.First,this model considers the influence of temperature and water content on membrane resistance,derives a formula for calculating membrane water content,and couples the CIWC model with the computational fluid dynamics software FLUENT for computation.Second,a fuel cell test bench was constructed to perform experiments at an operating temperature of 60℃,100%anode relative humidity,and 50%,75%,and 100%cathode relative humidity,respectively.Finally,the simulated data of the CIWC model and the FLUENT built-in model were compared with experimental values.The species distribution of membrane water content,membrane conductivity,and molar water fraction in the catalytic layer on the cathode side were analyzed.The results show that at a cathode relative humidity of 50%,the CIWC model's accuracy improved by 17.67%compared to the FLUENT model at a voltage of 0.739 V.The maximum relative error between the CIWC model and experimental value was 5.66%at 100%cathode relative humidity.As the cathode's relative humidity increases,the membrane water content continuously rises at a voltage of 0.75 V and approaches saturation at 0.6 V.The membrane water content,proton conductivity,and molar water fraction in the catalytic layer gradually increase in the flow field directly from the air inlet to the outlet.At a cathode relative humidity of 75%,the fuel cell output power density reaches 272.08 mW/cm^(2),and the membrane water content distribution becomes more uniform.