Supersonic Ejectors in Hydrogen Refueling Stations and Fuel Cell Systems: A Review

Hydrogen fueling stations are becoming more widespread due to the global shift toward net zero emissions. This drives the need to improve their efficiency and reduce their energy consumption. Supersonic ejectors offer a passive alternative to traditional mechanical valves and compressors. Their integration into hydrogen fueling stations can lower compression costs and reduce refueling energy; however, the efficiency significantly drops when operating within the subcritical region resulting in an unstable system or reverse flow. Despite the advancements in ejector system analysis through numerical modeling and computational fluid dynamics (CFD), the performance limitations highlight the need for experimental validation under real-world conditions. Evaluating safety risks, adaptability to variable flow and system fluctuations is needed through an ejector system set up with instrumentation and monitoring. This review explores ejector research developments with a focus on parameters affecting efficiency such as the entrainment ratio, compression ratio, and coefficient of performance. The important role of supersonic ejectors for hydrogen recirculation in Fuel Cell systems is also discussed. Future research should focus on addressing scalability, geometry limitations, control strategies, and experimental validation to enhance ejectors’ potential to be incorporated into hydrogen fueling applications and enhanced performance in Fuel Cell applications.