Regulation of anode gas pressure for durable and secure operation of proton exchange membrane fuel cells with variable-flow-rate ejector

The anodic recirculation system (ARS) is an essential component of modern proton-exchange membrane fuel cells (PEMFCs). In order to address the limited working range issue of conventional ejectors, a variable-flow-rate ejector, whose working principle is based on the linear movement of the needle inside the nozzle throat, was proposed. In this research, a modeling case study of this ejector in a PEMFC was established, which reflected not only the dynamic response of the ARS using this special ejector but also its collaboration with the fuel cell stack. A control target was established to maintain the pressure difference between the anode and cathode inlets to protect the long-term operation of the PEMFC. Therefore, an investigation focusing on the thermodynamic properties of the ejector can be conducted. These findings suggest that employing an adjustable geometry ejector improves the stoichiometry, recirculation ratio, and operational safety of the fuel cell stack. In addition, the ejector facilitated the self-humidification process by taking advantage of the vapor fraction in the anode outlet flow. Furthermore, the stack dynamic response to the anode intake flow was examined using the PEMFC inner pressure and relative humidity relationship to determine the relationship between these parameters and actual cell voltage.