Active and passive fuel recirculation for solid oxide and proton exchange membrane fuel cells

摘要

Fuel recirculation is extremely important to fuel cell performance and durability, but it seems not to receive enough consideration so far. We thoroughly reviewed active and passive fuel recirculation for solid oxide fuel cells (SOFCs) and proton exchange membrane fuel cells (PEMFCs). The structure and derivatives of ejectors were introduced, and the critical design criteria from the geometry size were also provided to achieve high entrainment ratio. Three working zones were discussed to better understand the flow behavior and dynamics of primary and secondary flows. We also listed some examples on recirculation pumps as a model of active fuel recirculation from very limited open reports. And then, the application of fuel recirculation in fuel cells, specifically the characteristic functions and effects of fuel recirculation, were comprehensively discussed which include the efficiency, gas management, the steam to carbon ratio (STCR) for SOFCs, and the efficiency, gas management, nitrogen crossover, humidification, flooding and water drainage for PEMFCs. The numerical modeling coupled with experimental results were also reviewed due to its exceptional advantages in exploring the basics and fundamentals related to flows, device design and fuel cell performance. (C) 2020 Elsevier Ltd. All rights reserved.