Investigation on the wet compression performance of a co-rotating scroll hydrogen recirculation pump for fuel cell engine systems

The scroll-type hydrogen recirculation pump is critical for fuel cell vehicle powertrain systems, yet its performance under multiphase conditions remains poorly understood. This study proposes a co-rotating scroll hydrogen pump with array scrolls and investigates its aerodynamic performance, including volumetric efficiency, isentropic efficiency, and power consumption, under varying inlet humidity through 3D transient numerical simulations. Additionally, the effects of operational and geometric parameters (rotational speed, radial clearance, and axial clearance) on the wet compression performance of the pump at the maximum inlet humidity are carried out. Results show that inlet humidity primarily affects the compression and discharge processes of the pump. Increasing inlet humidity suppresses tangential leakage, improving volumetric efficiency, while reducing isentropic efficiency. With inlet humidity increasing from 0% to 100%, the volumetric and isentropic efficiencies change by + 1.84% and −2.3%, respectively, with a power consumption increase of approximately 8.9 W. Higher rotational speeds significantly decrease the isentropic efficiency, while axial clearance has a more pronounced impact on both efficiencies compared to radial clearance. Specifically, increasing rotational speed from 5000 r/min to 15,000 r/min enhances volumetric efficiency by 9.27% and reduces isentropic efficiency by 6.72%. Similarly, increasing radial clearance from 20 μm to 40 μm reduces volumetric efficiency by 5.51% and isentropic efficiency by 0.87%. Raising axial clearance from 20 μm to 40 μm results in a 17.86% drop in volumetric efficiency and 10.7% in isentropic efficiency. These findings offer design insights for high-efficiency co-rotating scroll hydrogen pumps.