CFD-Based Performance Comparison of Ejector Geometric Configurations for PEMFC Systems

This study systematically analyzed the performance of three ejector configurations, namely conventional, coaxial dual-nozzle, and multinozzle ejectors, in proton exchange membrane fuel cell (PEMFC) hydrogen recirculation systems, with a focus on performance comparison and optimization. Three-dimensional (3D) computational fluid dynamics (CFD) simulation models were developed for each configuration to optimize critical geometric parameters: the nozzle area ratio and axial offset of the secondary nozzle for the coaxial dual-nozzle ejector, and the number of nozzles for the multinozzle ejector. Corresponding control strategies were formulated, and a comprehensive full-range performance analysis was conducted. The results show that the coaxial dual-nozzle ejector achieved optimal performance at a nozzle area ratio of 1 ∶ 1 with a 0.75-mm axial offset, and the multinozzle ejector performed best with three nozzles. Overall, the coaxial dual-nozzle ejector exhibited superior performance, with an average entrainment ratio 17.21% higher than that of the conventional ejector and 9.09% higher than the multinozzle ejector. This study clarifies the performance advantages of different ejector configurations through systematic performance comparison and supplies a theoretical rationale for optimizing PEMFC hydrogen recirculation system design.