Optimization of the Structure of a Dual-Nozzle Ejector for PEMFCs Based on CFD and Orthogonal Test

Aiming at the characteristics of hydrogen injector for automotive proton exchange membrane fuel cells (PEMFC) and with the goal of expanding the working range of the pilot injector, a comprehensive optimization analysis of the structural parameters of the pilot injector was carried out based on the orthogonal experiment method. In this study, computational fluid dynamics (CFD) numerical simulation was employed to investigate the cyclic performance of the dual-nozzle ejector, and a four-factor, four-level orthogonal test method was adopted to perform a multifactor analysis of the changes in the cyclic performance of the ejector caused by the key structural parameters given the three idling conditions, 60% of rated operating conditions and full load electric reactor operating conditions, respectively, to form a 16-group multiobjective optimization design scheme. The signal-to-noise ratio (SNR) analysis of variance was applied to find the main control parameters according to their contributions. Taking the hydrogen circulation efficiency as the target, the significant order of the structural parameters affecting the hydrogen circulation performance of the dual-nozzle ejector was obtained given the 120 kW system full power section operating conditions. The optimal combinations of isobaric mixing chamber contraction angle (αc=25°), isobaric mixing chamber radial length (Lm=19.5 mm), nozzle exit horizontal distance (NXP=5.85 mm), and diffuser chamber inclination angle (αd=4.5°) were finally obtained. This paper provides a new idea for the optimization of multiple sets of structural design parameters of the dual-nozzle ejector, which is of some reference value for the design and application of the dual-nozzle ejector.