Numerical study on purge characteristics and purge strategy for PEMFC hydrogen system based on exhaust hydrogen recirculation

The lumped parameter model of the hydrogen system based on exhaust hydrogen recirculation and the CFD model of PEMFC stack were established in this paper. The system simulation results were used as the input of the stack model. The purge characteristics of the stack were studied and the purge strategy was formulated considering the hydrogen utilization and performance characteristics. The results show that during anode purging, the anode pressure fluctuated significantly and the nitrogen concentration decreased rapidly. The output voltage of the stack fluctuates greatly, and the fluctuation of volt-age intensifies with the extension of emission duration. In addition, the voltage fluctuation range of unit cell decreases gradually from inlet to outlet. After the system stabilizes, the component distribution of anode was improved and the stack performance was recovered to the initial state. During the purge interval, the performance of the stack degrades due to the increase of anode nitrogen concentration. The hydrogen utilization rate of the hydrogen system was directly related to the purge strategy, and the purge strategy of short period-short duration was beneficial to reduce the fluctuation of the stack performance in the purging process, and reduce the differences of performance and component distribution of different single cell.