A nonlinear contraction channel design inspired by typical mathematical curves: Boosting net power and water discharge of PEM fuel cells

The next-generation fuel cell needs to fit high current density operating conditions, necessitating improved flow fields with superior capabilities in mass transfer and drainage. This study introduces four innovative nonlinear contraction channels aimed at enhancing net power and mitigating waterflooding under high current density. This design draws inspiration from classical mathematical curves, which can provide targeted mass transfer enhancement contingent upon species distribution. Multiple quantitative indicators are employed to evaluate the efficacy of nonlinear structures in cross-scale mass transfer, drainage, temperature uniformity, and power consumption. Numerical results indicate that the exponential-like curve channel exhibits notably superior overall performance. Its nonlinear contraction region induces purge airflow at the tail of channel, facilitating drainage and boosting the local mass transfer flux in oxygen-starved region by 48.75%. The utilization of nonlinear contraction structures alters the diffusion-convection distribution mechanism and increases the convective mass transfer proportion. Under conditions of high current density, there is a noticeable rise in the Peclet number. Considering the pumping power loss, the hyperbolic tangent, quarter-ellipse, parabolic, and exponential-like curve flow channels can enhance the net power by 3.10%, 6.82%, 8.57%, and 10.04% over straight channels. Additionally, the exponential-like curve channel enhances temperature uniformity in the catalyst layer under rated working conditions, whereas the hyperbolic tangent flow channel demonstrates superior uniformity in higher current density.