Effect of secondary flow relative molecular mass on the performance of the ejector for PEMFC anode system: A quantitative analysis

Abstract

ABSTRACT Anode gas recirculation systems have a critical impact on the performance and hydrogen utilization efficiency of proton-exchange membrane fuel cells. The ejector is one of the main devices of the anode gas recirculation system, and offers advantages such as low cost, no parasitic power, and simple structure. In this study, a two-dimensional ejector model was adopted, and its performance was investigated using computational fluid dynamics (CFD). The effect of the secondary flow relative molecular mass (SFRMM) on the ejector performance was quantified. A regression model that describes the relationship between the SFRMM and entrainment ratio (ER) was proposed. The flow field characteristics, such as the pressure and velocity inside the ejector, were also analyzed. The results show that the higher the SFRMM, the greater the ER, and the lower the hydrogen recirculation ratio. Among the 90 sets of ER data under all operating conditions, the relative errors between the predicted values of the regression model and the simulated values from CFD are generally within 11%, with an average relative error of 6.1%.