Anode flooding characteristics as design boundary for a hydrogen supply system for automotive polymer electrolyte membrane fuel cells

• The critical Reynolds number for water removal from a PEM fuel cell anode is obtained.
• Various automotive hydrogen supply systems are compared with the resulting requirements.
• Only active recirculation systems achieve the requirements for all fuel cell load points.
• Passive systems require a hybridization strategy of the fuel cell system.

An automotive fuel cell is investigated to define the design boundaries for an automotive hydrogen supply system with regard to anode flooding. The flooding characteristics of the fuel cell anode at various operating conditions (hydrogen flow rate, pressure, temperature, current density) are analyzed by in-situ and ex-situ measurements. Stable operation conditions are identified and a relation to the operating conditions is established. For adequate water removal, a minimum Reynolds number in the gas channels has to be adjusted. Using this information, different hydrogen supply system designs are compared in their compliance with the stability requirements. It is shown that passive hydrogen supply systems do not achieve all fuel cell requirements regarding power density, lifetime and robustness.