Improvement of air distribution consistency in large-scale proton exchange membrane fuel cell stack manifold

Abstract

The development of PEMFC (proton exchange membrane fuel cell, PEMFC) a higher power stack in buses and commercial transport vehicles is a growing trend at present. However, the higher power stack requires increasingly consistent flow distribution. In this manuscript, a new air manifold type design of X-shape has been proposed. The differences between the X-shape manifold and the U-shape manifold have been investigated using the CFD (Computational Fluid Dynamics, CFD) model. The model is simultaneously and quantitatively validated with two different variables, precisely, mass flow rate and pressure drop, to ensure its accuracy. The CV (coefficient of variance, CV) value of the X-shape manifold is much lower in comparison to that of the U-shape manifold. A mathematical model was established to explain the key factor responsible for a more uniform distribution of X-shaped manifolds in comparison to-shaped manifolds. The key factor is precisely the smaller magnitude of the pressure drop at the inlet and outlet of the X-shaped manifold in comparison to that of the U-shaped manifold. Based on this, the size reduction of the air entering the bipolar plates is the strategy to improve air distribution consistency. This viewpoint has also been proven by the derivation of a mathematical model and an optimal reduction in size has been observed. The CV of U-shape, X-shape, and X2-shape-50%In-100%Out (entrance geometry narrowed to 50%) are 5.82%,1.32%, and 0.45%, respectively.