Comprehensive evaluation and analysis of anodic gas state parameters of hydrogen recirculation ejector for PEM fuel cells

Abstract Hydrogen ejectors in proton exchange membrane fuel cell (PEMFC) systems can reliably recover hydrogen without parasitic power, making them an ideal alternative to pumps. However, improving fuel utilization, enhancing ejector efficiency, and extend the ejector’s operating range are important issues currently faced by PEMFC systems. In this study, a comprehensive evaluation system including four indicators (hydrogen entrainment ratio (ωH 2 ), ejector outlet relative humidity ( RH c ), ejector outlet temperature ( T c ), and ejector efficiency ( η ejector )) are established based on the operating conditions and structural parameters characteristics of the ejector. The influence of secondary flow relative humidity ( RH s ) and secondary flow temperature ( T s ) on ejector performance are analyzed. The results show that the hydrogen entrainment ratio decreases as the secondary flow relative humidity or temperature increases. RH c increases and T c decreases as the gas mixture reaches the outlet of the ejector. Ts should be controlled below 353K and RH s below 57% to prevent condensation of water vapor at the ejector outlet, at which point the ejector efficiency is 55.82%. To improve the ejector efficiency, the secondary flow temperature can be further increased, but the secondary flow relative humidity must be controlled accordingly. A theoretical basis for the development of high-temperature PEMFC is also provided.