An ultralightweight anode-exhaust-driven micro-ejector enabling zero-parasitic-power cathode air supply for compact fuel cell systems

An ultralightweight (0.2 g) stereolithographically fabricated micro-ejector was developed for passive cathode air supply in compact proton exchange membrane fuel cell (PEFC) systems. Unlike conventional miniature fuel cell systems that rely on mechanical air pumps and incur significant parasitic power consumption, the proposed ejector utilizes anode exhaust gas as the driving flow and requires no additional electrical power. CFD simulations were conducted to optimize the ejector geometry under practical operating pressures below 100 kPa, and additively manufactured ejectors achieved entrainment ratios (ERs) exceeding 4, with a maximum ER of 12, under low-pressure operating conditions (<100 kPa). The optimized ejector was successfully integrated with a PEFC, enabling stable fuel cell operation with a maximum power output of 0.28 W. Furthermore, 12 h constant-current operation exhibited voltage fluctuations below 5 mV, demonstrating stable cathode air supply without active flow control. The proposed approach provides a lightweight and compact balance-of-plant solution for portable and distributed fuel cell applications.