Improved PEM fuel cell system operation with cascaded stack and ejector-based recirculation

An automotive fuel cell system combining a variable-geometry ejector and a fuel cell stack with cascaded anode is presented. It allows to decrease the minimum operational power range by increasing recirculation performance of the ejector. Design boundaries for the fuel cell anode are used to investigate four different designs of fuel cell stack with cascaded anode. For these designs, ejectors with variable-geometry are developed and their performance in combination with the fuel cell stacks are investigated using CFD simulations. A combination of a variable-geometry ejector with a two stage cascaded stack design is shown to exhibit a better recirculation performance at low power outputs than systems with conventional stack design. It is demonstrated experimentally that the new fuel cell design achieves similar performance and stability on a test bench compared to conventional stack design.