Numerical investigation into hydrogen supply stability and I-V performance of PEM fuel cell system with passive Venturi ejector

Abstract

In traditional PEM fuel cells (PEMFCs), the unreacted hydrogen gas at the anode outlet is recovered using a mechanical pump or centrifuge and returned to the inlet side for reuse. However, the energy consumed by the pump reduces the system efficiency. Accordingly, the present study considers a 3-kW PEMFC in which the unreacted hydrogen gas is recovered passively from the exhaust stream using a Venturi ejector. An integrated simulation framework is constructed consisting of a COMSOL model of the ejector unit and a MATLAB/Simulink model of the hydrogen recovery system. The simulation framework is used to examine the temperature, pressure and velocity distributions within the ejector for various values of the inlet hydrogen pressure. The stability of the hydrogen supply in PEMFC systems incorporating a passive ejector system and a traditional mechanical hydrogen recovery system, respectively, is then investigated and compared. It is shown that the ejector stabilizes the hydrogen supply more quickly than the traditional mechanical system. As a result, it not only improves the hydrogen utilization rate and environmental safety of the PEMFC system, but also reduces the overall hydrogen consumption. The simulation results for the I-V performance of the PEMFC with the Venturi ejector are shown to be in good qualitative agreement with the experimental results. Overall, the numerical framework constructed in the present study provides a useful tool for exploring the effects of the ejector design parameters on the hydrogen recovery performance and determining the operating conditions which maximize the performance of the PEMFC system.