The Study Of Water Transport Process In The Flow Channel Of Proton Exchange Membrane Fuel Cell

As a new type power generation device,Proton Exchange Membrane Fuel Cells(PEMFC)have high power generation efficiency and no pollution to the environment.Water management is a key technology that affects the performance,stability and reliability of PEMFC.The efficient transmission and quick removal of water in PEMFC flow channels is an important aspect of PEMFC water management.Researching and analyzing the distribution,transmission and removal process of water in the flow channel is of great significance for deep understanding of the transmission characteristics and removal mechanism of liquid water in the microscopic flow channel and guiding the design of PEMFC flow channel.Based on the PEMFC flow channel,the water transfer phenomena in the bionic flow channel and the micro-channels of Gas Diffusion Layer(GDL)deformation was studied in this thesis.Based on Murray’s law,a new novel bionic flow channel structure was designed by simulating vein structure in this thesis.And three-dimensional geometric models of bionic flow cell and serpentine flow cell were established.Professional meshing software was applied to divide the cell model into structural grids.Finally,finite element software was used to simulate the two cells under the same conditions.Through the results of the cell simulation,it can be seen that the structure of the bionic flow channel is more reasonable than that of the serpentine flow channel,the performance of cell is better,and the water management performance of the bionic flow path is better at high current density and low current density.Two kinds of cathode micro-channel models were established in this thesis: the channel of GDL deformation and the channel of GDL with no deformation.There were hydrophilic grooves in the channel of GDL deformation.The VOF method was used to simulate the dynamic transmission of liquid water in two flow channel models.The influence of the deformation of GDL and the air velocity on the water transfer in the micro-channel was studied by comparing the pressure drop,the liquid water content and the discharge time of the liquid water in the flow channel.The results showed that the hydrophilic grooves in the flow channel of GDL deformation obstruct the transport of liquid water in the flow channel,resulting in the accumulation of water in the flow channel.Increasing the air velocity can speed up the discharge of liquid water and reduce the liquid water content in the flow channel.In the flow channel of GDL deformation,liquid water still accumulated in the hydrophilic grooves when the air velocity was increased.In this thesis,visual flow channels were used to directly observe the distribution and morphology of liquid water in bionic flow channels and serpentine flow channels.The fiber grating(FBG)sensor was applied to detect of liquid water in the flow channel,this made preliminary preparations for the application of fiber grating sensor in the in situ experiments of cells.The experimental results showed that liquid water forms the droplet and slug in the flow channel.In the serpentine flow channel,the accumulation of liquid water occurred at the corners of the flow channel,and the distribution of liquid water in the bionic flow channel was more uniform,and no water accumulated at the outlet.The experiment also verified the accuracy of the detection of the liquid water signal in the flow channel by the FBG sensor,showed that the FBG sensor can be used for the detection of the two-phase flow in the flow channel.