Optimization of Key Structural Parameters of Nozzle-Lengthened Ejector for Low-Power Proton Exchange Membrane Fuel Cell

Aiming at the problems of low ejection rate, poor hydrogen circulation effect, and complex structure of the mixing pump system of the ejector under the low-power condition of the fuel cell, this paper proposes a nozzle-lengthened ejector. The computational fluid dynamics (CFD) simulation analysis method is adopted to numerically analyze the high- and low-pressure flows and mixing process inside the lengthened ejector, study the influence law of key parameters on ejection performance, and carry out optimization. The results showed that the nozzle-lengthened ejector can effectively constrain the flow of the primary flow, reduce the turbulent flow characteristics of the primary flow after leaving the nozzle, and increase the injection ratio by about 10% compared with traditional injectors. With the changes of lengthened nozzle d, outlet L of diversion nozzle, inlet β of diversion nozzle, and mixing chamber Lm, the ejection performance shows a trend of first increasing and then decreasing. With the change of outlet α of diversion nozzle, it shows an m-shaped change trend. Additionally, when d=1.2 mm, α=60°, L=0.95 mm, β=25°, and Lm=30 mm, the ejector has relatively better ejection performance. It is suitable for fuel cells in the power range of 13.5 to 54 kW, and it can provide an ejection ratio exceeding 1 in the power range of 15.5 to 34.5 kW.