Nitrogen Influence on The Performance of Ejector Based PEMFC Hydrogen Recirculation System

Ejector has been applied for hydrogen recirculation in the proton exchange membrane fuel cell due to its small volume, low cost, and no parasitic power consumption. The unconsumed hydrogen coming from the stack usually contains a lot of nitrogen, and the effect of nitrogen mole fraction on the recirculation performance of the ejector needs to be studied. In this study, a two-dimensional Computational Fluid Dynamics model is developed to study the influence of nitrogen mole fraction in the secondary flow on the ejector’s performance. The results show that the recirculation performance of the ejector is sensitive to nitrogen mole fraction in the secondary flow, which is because of the influence of nitrogen on the fluid mixing inside the ejector. The recirculation ratio and nitrogen mole fraction show a linear positive correlation, while the hydrogen recirculation ratio shows a linear negative correlation. The minimum values of recirculation ratio and hydrogen recirculation ratio are 238 and 0.4 indicating that the recirculation performance of the ejector is acceptable.