Designing and performance investigations on an ejector with auxiliary inlet for PEMFC hydrogen recirculation system

The ejector driven by the high-pressure gas potential energy can reliably recirculate the unreacted hydrogen without consuming parasitic power in proton exchange membrane fuel cell (PEMFC) system. The ejector-driven hydrogen recirculation system must maintain sufficient recirculate capacity to take out the water generated in the fuel cell to ensure the stable operation of the PEMFC system. However, when the output power of the fuel cell system is relatively large, the inside of the ejector may be blocked, causing the recirculation performance of the ejector to decrease. In this paper, an ejector with auxiliary entrainment is developed for the hydrogen recirculation system to improve the performance under the larger output power. The ejector is numerically investigated, using a two-dimensional numerical model verified by experiment, to reveal the flow structure and evaluate its performance. The simulation results show that the ability of recirculation performance of the ejector is improved about 18% than the traditional ejector at 84 kW output power. Furthermore, as the increase of the auxiliary secondary flow inlet diameter, the recirculation performance of the ejector gradually increases. When the diameter of the auxiliary secondary inlet is above 6mm, the recirculation ratio of the ejector does not increase significantly. The developed ejector has better performance than the traditional ejector in the PEMFC system, which significantly promotes the development of fuel cell being widely adopted in automobiles.