Optimization of hydrogen ejector structure in proton exchange membrane fuel cell system under wide operating conditions

Abstract

ABSTRACT Considering the characteristics of the hydrogen ejector for proton exchange membrane fuel cell system used in vehicles, with the aim of expanding the operating range, the ejector structure parameters are comprehensively analyzed and optimized. The results indicate that reducing the throat diameter can expand its operating range. When the working conditions change significantly, the convergent nozzle should be selected, the convergence length and throat length of the nozzle have little effect on the ejection performance. There are optimal suction chamber convergence length (8 mm), diffuser divergent angle (7.1°) and length (33.8 mm), nozzle exit position (−7 mm) in variable working conditions to achieve good ejection performance. Reducing the diameter and length of the mixing chamber is beneficial for expanding the operating range. Before ejector optimization, when the primary fluid mass flow rate is less than the design value, the ejection performance deteriorates sharply with the decrease of the flow rate. When the primary fluid mass flow rate is lower than 0.4 g/s, the non-optimization ejector is backflow, the maximum ejection ratio is about 1.8 and the maximum hydrogen ejection ratio is about 0.67 in the operating range. After optimization, the ejector performance is stable. Under the set operating conditions, the hydrogen ejection ratio is greater than 0.75, the maximum ejection ratio is 3.8, and the maximum hydrogen ejection ratio is 1.01.