Optimization of geometric parameters of ejector for fuel cell system based on multi-objective optimization method

In this study, the multi-objective orthogonal experiment is employed to optimize the geometric parameters of the ejector. The optimization objective is determined by applying linear weighting to the entrainment ratios for 100 SLPM and 990 SLPM operating conditions. Four geometric parameters are optimized, including the nozzle exit diameter, nozzle exit position, mixing chamber length, the mixing chamber diameter. Moreover, Computational Fluid Dynamics simulations are performed, and the effects of each geometric parameter and the interaction between parameters on the performance of the ejector are ranked by range analysis. The results show that the mixing chamber diameter has the most significant impact on the optimization objective, and the degree of influence of the other factors and interactions on the entrainment ratio varies for different operating conditions. Compared with the initial parameters, the parameters obtained by the multi-objective optimization method have an average improvement of 96% in entrainment ratio over the full operating range, and the experimental results are in general agreement with the simulation results. The adaptability analysis of the ejector performance indicates that the ejector optimized by the multi-objective optimization method can meet the hydrogen excess ratio requirements for the full operating range of the fuel cell system.