Investigation on the Electrostatics Saturation of Flow Electrification in the Liquid Hydrogen Transportation

Research on the flow electrification characteristic is of paramount importance for ensuring the electrostatic safety of liquid hydrogen transportation systems. However, the discussion about electrostatic saturation in flow electrification has been lacking. To address this gap, a theoretical model governing the process of flow electrification is constructed which couples the charge conservation equation with the Navier-Stokes equations and applies the Neumann boundary conditions at the solid-liquid interface, and the application of this model is validated by existing experimental data with the simulation parameters of At and n being 9.08 Chi 10(12) and 0.85 for liquid hydrogen. A comparison with benzene reveals that benzene almost reaches the electrostatic saturation state after flowing one meter, whereas the flow of liquid hydrogen remains in the linear growth stage. However, with an increase in pipe length, a gradual saturation trend emerges in the curves of streaming current versus flow distance when the flow distance exceeds 10 m. At the outlet, the corresponding streaming current and charge density are approximately 160 pA and 3 mu C/m(3), respectively, significantly higher than those observed at one-meter flow distance. Furthermore, the influences of pipe radius and flow velocity on the arrival of electrostatic saturation are analyzed, and the results show that increasing both the pipe radius and flow velocity leads to a delay in the arrival of electrostatic saturation and enhances the saturation value of the streaming current. In conclusion, this study thoroughly discusses the development of flow electrification along with the flow distance and the phenomenon of electrostatic saturation in the long-distance flow of liquid hydrogen, which is crucial for the safe transportation of liquid hydrogen over extended distances.