Three segments distribution of gas diffusion layer porosity in a proton exchange membrane fuel cell

•A 3D, two-phase flow, non-isothermal agglomerate is established.•Averages of optimal porosity in three directions decrease with voltage increase.•The reaction rate is influenced by charge transfer near inlet region at low voltages.•The reaction rate is affected by reactant content near outlet region at middle voltages.•The porosity distributions along various directions can produce different effects. Porosity is the main parameter of gas diffusion layer and has a great influence on cell output performance. The electrochemical reaction rate is various in different region within the cell and the porous electrode may deform because of extrusion during assembly. So non-uniform distribution of porosity may be more similar to the real structure and can change cell performance. Thus, a 3D, two-phase agglomerate model is established to explore the optimal three segments distributions of porosity both in anode and cathode sides along three directions at different voltages using the optimization algorithm without constrains, and the reasons for these results at 0.2 V, 0.6 V and 0.8 V are also emphatically analyzed. The results indicate that the average of optimal porosity in three directions decreases with voltage increasing. With voltage increasing, optimal porosity increases from inlet to outlet, and the value increases along width direction. When cell voltage is 0.2 V, the reaction rate is mainly determined by reactant content, but it is influenced by charge transfer near inlet region. At 0.6 V, the rate is related to charge transmission, but it is affected by reactant content near outlet region.