Simulation Of Skin Effect In Proton Exchange Membrane Fuel Cell

Skin effect is the electromagnetic phenomenon caused by alternate current. When the alternate current goes through the conductor, the current density distribution is not average on the cross section, but mostly concentrate at the edge of the conductor. In the middle of the conductor there is almost no current.Proton Exchange Membrane Fuel Cell(PEMFC) becomes the hot research because it has many advantages, such as rapid start at room temperature, no electrolyte wastage, simple configuration, high specific power and energy. Skin effect may be emerged on the conductive material of the PEMFC, and makes the current density distribution unequal in PEMFC, so it is harmful for the life of the PEMFC.In this thesis the skin effect in the PEMFC was studied based on the mathematical simulation. The computational model of skin effect was developed according to Maxwell Electromagnetic Theory. The simulation results agreed well with the experiment results. The skin effects in the stainless steel and graphite bipolar plates are numerically investigated, and the skin effects in fuel cell bipolar plates with different materials and shapes are also numerically investigated. The skin effect in the conductor with diffierent materials seriesly connected are also studied. The simulation results show that:(1) Under the same calculation condition, for the bipolar plates with equal area and different section shapes, such as square rectangle and circular, the skin effect with rectangle section shape bipolar plate is the least obvious. (2) For the bipolar plates with rectangle section shape, the skin effect of current density reduces with the increase of the ratio between the length and the width of the bipolar plate cross section. (3) When the conductors with diffierent materials are connected in series, the different conductivities of the conductors'both sides will lead to diffierent current density distribution in the middle conductor. When both sides of the conductor have the same conductivity, the current density distribution in the middle cunductor is different with different length.Based on the above results, the skin effect calculation model of single fuel cell is developed, and the current density distributions inside the fuel cell under three different current frequencies(10kHz,5kHz,1kHz) are studied. The simulation results show that:(1) For the straight channel fuel cell with 20cm x 3.8cm active area, the skin effect in the fuel cell is not obvious when the current frequency is under 1kHz. (2) There is no skin effect on the Gas Diffusion Layer(GDL) because the GDL is very thin. (3) The skin effect on the bipolar plates is very obvious; The skin effect on the middle section of the bipolar plate is the most obvious; The edge and the interface of the electrode rib and the channel of the bipolar plate have greater current density.