Qualitative and quantitative diagnosis of internal hydrogen leakage in fuel cell based on air flowrate control and open-circuit voltage measurements

Internal hydrogen leakage faults in fuel cells can cause severe performance loss and safety risks. The aim of this study is to achieve qualitative and quantitative diagnoses of internal leakage in fuel cell based on air flowrate control and transient voltage measurements. The hydrogen crossover characteristics of a fault-free and defective fuel cell are both investigated, and the effectiveness of the diagnosis method is evaluated by comparing and analyzing the results before and after the leakage fault introduction. The results suggest that hydrogen leakage failure inside fuel cell is dominated by convection processes. In airflow interruption tests, where the fuel cell is operated under open-circuit conditions with given anode overpressures, the fall time of the cell voltage is used as a qualitative measure of internal hydrogen leakage, and fault occurrence can be recognized by a considerable decrease in this indicator. Through cyclic staircase flowrate sweep tests, we obtain good estimates of internal leakage rates in the defective fuel cell. These diagnostic methods can be performed directly under hydrogen/air conditions, and there is no need for additional power source equipment dedicated to generating excitation signals for fuel cell, giving them great potential in on-board applications.