Flow Characterization of a Polymer Electronic Membrane Fuel Cell Manifold and Individual Cells Using Particle Image Velocimetry

Detailed measurements of flow through a model of a fuel cell stack were made using particle image velocimetry (PIV). The objective was to obtain high caliber sets of velocity fields in both the inlet manifold and within the cells over a range of Reynolds numbers in order to provide a benchmark for computational fluid dynamics (CFD) data and to demonstrate relationships between flow distributions in the manifold and those along the cells of the stack. A scaled up model was built and placed in a wind tunnel under uniform inlet flow conditions. Using the PIV technique, instantaneous flowfields were captured which were then averaged to obtain mean and fluctuating velocity statistics. Based on analysis of the data, relationships were found between manifold and cell flow distributions. Within the inlet manifold, magnitudes of normalized streamwise velocities were found to increase towards the aft of the manifold with Reynolds number. This was believed to be associated with the more severe cell flow maldistributions which were found to exist with increasing Reynolds numbers. Examination of instantaneous velocity distributions in the manifold demonstrated the existence of discrete vortical structures and complex fluid motions towards the aft, resulting in increased velocity fluctuations in this region. Velocity fluctuations within the cells were also found to increase towards the aft of the stack, leading to higher flow unsteadiness in these cells.