Dynamic Performance And Durability Of PEM Fuel Cell For Vehicle

Proton exchange membrane fuel cell (PEMFC) is the most probable for automobile, bus, electrical equipment, portable power and stationary product, and it has a very good foreground. However, some of its mechanism and durability problems especially the durability is still unsolved. This thesis will use computational fluid dynamics software such as Fluent, Matlab/Simulink and ANSYS to simulate the dynamic performance of fuel cell based on its internal mechanism, dynamic characteristics and durability.At first, the basic theory of fuel cell is described and a three dimension mathematical model is built by Fluent to model the performance of PEMFC. It can be found that 2 atm operating pressure acquires the best performance. Then, the dynamics of water distribution is studied by varying operating pressure from 1 atm to 2 atm. The result shows that water content in the membrane increases with the increasing operating pressure, it takes about 0.5s to reach a new steady-state in the central line of the membrane and the whole membrane reaches the steady-state at the same time, thus improving the performance of fuel cell.Subsequently, a Matlab/Simulink single-cell model with 25cm~2 active area is built to study the performance of fuel cells aroused by partial operating pressure of hydrogen and oxygen. The results show that, when the operating pressure rises higher, the output power and efficiency get increased, but equivalent resistance becomes lower oppositely. At 2 atm operating pressure, the output power, efficiency and equivalent resistance reaches 10.1042W, 57.57% and 0.0331Ωrespectively. It can be also found that, Simulink software is more suitable for larger fuel cell and stack.Finally, ANSYS software is used to establish the plane strain model of PEMFC. The simulation result shows: if only the assembly is considered, PEMFC yielding phenomenon occurs in a displacement loading of 6.55μm which is equal to 4.59MPa loading pressure. When temperature field is imposed on fuel cell, it yields under 3.95μm displacement loading which is equal to 4.336MPa loading pressure. Thermal load has great effect on the center of the membrane while mechanical load has strong effect on the other side of the membrane. After applying loads to the model, the equivalent stress of bilateral region of membrane is maximum, and leading directly to the failure of fuel cell.Based on computer simulation, the primary research of this thesis concentrates on the internal mechanism and durability of PEMFC. The results provide certain instruction to PEMFC design and manufacture.