Flow Distribution Measurements at the Exit of Bipolar Plates in a PEM Fuel Cell Stack by a Scanning Light Sheet Method

Kurzfassung

This paper summarizes two different experimental approaches which concentrate on capturing the exit flow distribution of the anode side of a prototype fuel cell stack operated with air at realistic flow rates. The first approach intends to visualize the penetration depth of the millimetre-sized exit jets in a laminar mixing flow by introducing oil-based tracer particles to the exit header and leaving the bipolar plates and exit jets unseeded. The second approach concentrates on measuring the exit jet velocity field downstream of the channel exits by particle image velocimetry (PIV) and by applying a water-based micron-sized droplet seeding to the bipolar plate channels. The traversal of the imaged plane along the bipolar plate exits finally allowed the reconstruction of the complete three-dimensional, time-averaged flow field in high resolution (restricted to two components of velocity). An overview of the experimental setup, including the implementation of a miniaturized light sheet probe, and the data evaluation are given. In addition, the application of a robust PIV evaluation algorithm based on multi-grid, multi-pass correlation averaging methods is described which had to be applied at higher flow rates due to highly dynamic fluctuations of the flow, lower particle image density and regionally significant background signal due to laser flare on the stack plates.