Comparative analysis of anode recirculation strategies and water separator integration for water management in proton exchange membrane fuel cell vehicle systems

Proton exchange membrane fuel cell (PEMFC) vehicles offer a promising zero-tailpipe-emission solution for heavy-duty transportation; however, anode water accumulation during prolonged high-load operation can compromise stack durability and hydrogen utilization. This study develops an integrated PEMFC vehicle system model, implemented and evaluated validated under the Heavy-Duty Urban Dynamometer Driving Schedule (HDUDDS), to compare ejector-only, recirculation pump-only, and hybrid hydrogen recirculation strategies and to evaluate the integration of a cyclone-type water separator. The hybrid configuration provides the most effective balance between hydrogen recovery and auxiliary-energy demand, achieving the highest cumulative hydrogen recirculation while reducing pump parasitic power by 11.9% through ejector-assisted operation at high loads. Incorporating the water separator at the anode outlet substantially limits liquid-water carryover, reducing the peak liquid-water recirculation flow rate by 73.4% and suppressing water accumulation in the anode manifold across all three configurations. These findings identify hybrid hydrogen recirculation combined with outlet water separation as the preferred architecture to enhance hydrogen utilization and mitigate flooding under transient heavy-duty driving conditions. This study provides a validated system-level framework for the coordinated design of hydrogen recirculation and anode water management in PEMFC vehicles.