Investigation of hydrogen recirculation ratios in individual ejectors under various operating conditions for a 110 kW PEMFC

Ejectors, characterized by a simple structure and zero parasitic power consumption, are reliable hydrogen supply mechanisms for fuel cells. Nevertheless, the ejector’s recirculation performance is typically inadequate under low power conditions, with variations in operating variables influencing its operating range. To mitigate this limitation, the present study examines the effects of three key operating variables—primary flow inlet temperature, secondary flow inlet temperature, and secondary flow water vapor mass fraction—on the recirculation ratio. The study compares hydrogen recirculation ratios under both rated and expanded operating conditions. Within the power range of 20 to 110 kW, the total recirculation ratio exhibits a slight increase with primary inlet temperatures rising from $\mathbf{2 8 0}$ to 340 K and a slight decrease as secondary inlet temperatures escalate from 320 to 370 K. With secondary inlet pressure held constant for a given stack power, an increase in secondary inlet temperature may decrease the fluid’s average density. An increase in water vapor mass fraction from $\mathbf{3 0 \%}$ to $\mathbf{9 0 \%}$ leads to a substantial rise in the total recirculation ratio. However, the hydrogen recirculation ratio experiences a marked decrease of $\mathbf{7 6. 2 2 \%}$ at 60 kW and $75.47 \%$ at 20 kW. Maintaining the secondary flow water vapor mass fraction at or below $\mathbf{3 0 \%}$ effectively guarantees a hydrogen recirculation ratio of at least 0.5 across the $20-110 \mathrm{~kW}$ power range.