A twin-nozzle ejector for hydrogen recirculation in wide power operation of polymer electrolyte membrane fuel cell system

•A twin-nozzle ejector for PEMFC hydrogen circulation with dynamic loads is proposed.•The influence of boundary conditions on the circulation performance is discussed.•The circulation performance of twin-nozzle ejector’s two working modes is analyzed.•The proposed twin-nozzle ejector can be used in a wider power output range of PEMFC. The ejector-driven hydrogen recirculation in the polymer electrolyte membrane fuel cell (PEMFC) system is a promising alternative to the pump-driven approach due to its advantages of small volume, low cost, parasitic power free, and low noise. However, the fixed structure of the ejector limits its application to the dynamic operation of the PEMFC system. To overcome this drawback, a twin-nozzle ejector with two nozzles placed symmetrically in the suction chamber is proposed for hydrogen recirculation under different PEMFC power outputs. A three-dimensional Computational Fluid Dynamics model for the proposed twin-nozzle ejector is developed and verified with experiment results. The hydrogen recirculation performance of single-nozzle and two-nozzle working modes is analyzed by a simulation study. The simulation results indicate that the single-nozzle mode can provide acceptable recirculation performance under low power outputs of the PEMFC system, and the two-nozzle mode is more suitable for the high-power outputs with lower supply hydrogen pressure. Compared with conventional ejector, the proposed twin-nozzle ejector can be used in a wider power output range from 17.00 to 85.00 kW with supply hydrogen pressure from 250 to 700 kPa by switching the two working modes. The proposed ejector provides an effective way to extend the application of ejector in hydrogen recirculation of PEMFC system.