Experimental and numerical study on the ejector containing condensable species in the secondary flow for PEM fuel cell applications

Phase transitions in two-phase ejectors have gained attention in various applications, including refrigeration, desalination, and fuel cell systems. The phase transition of condensable components in the primary flow significantly affects the ejector performance. However, studies on the phase transition of condensable species in the secondary flow are scarce. Consequently, this study aims to investigate two-phase flow characteristics of the ejector containing condensable species in the secondary flow. A schlieren experimental system with a visual rectangular ejector was constructed, and a transient Eulerian-Lagrangian two-phase flow model incorporating non-equilibrium condensation was developed. The numerical simulations achieved an average deviation of 4.7% in the entrainment ratio compared to experimental measurements, with a maximum deviation of 11.6%. The schlieren experiment revealed that the condensable species in the secondary flow can condense when the primary pressure exceeds 0.30 MPa. The numerical results showed that the condensed droplets reach a minimum proximity of approximately 3 mm from the primary nozzle exit and exhibit a divergence angle ranging from 7° to 12° as they traverse with the gas flow. Additionally, increasing the primary flow pressure from 0.2 MPa to 0.5 MPa resulted in a noticeable lengthening of the first shock wave, from 1.45 mm to 3.00 mm.