Experimental and simulation study of LN2 active-pressurization in onboard LH2 storage and supply systems

Abstract

To prevent insufficient pressure within the onboard LH₂ storage tank during supply, which could lead to significant residual LH₂ that cannot be supplied, the design of the onboard LH₂ storage and supply system needs to consider the active-pressurization method of the LH₂ tank. To investigate whether the active-pressurization method can meet the active-pressurization performance requirements for low-temperature fluids in onboard LH₂ storage tanks, this study uses LN₂ as the working fluid. Experiments on active-pressurization and supply in the onboard LH₂ storage system were conducted, exploring the impact of different LN₂ fill levels on the active-pressurization rate and the pressure stability during the active-pressurization supply process. Based on the parameters of the LH₂ tank, a system simulation model was established. The maximum active-pressurization flow rate of the simulation model was calibrated according to the active-pressurization experimental data, further exploring the active-pressurization storage and supply characteristics of the onboard LH₂ tank. The results indicate that the active-pressurization supply simulation results, calibrated with the active-pressurization flow rate, show good consistency with the experimental data. As the supply flow rate increases, the active-pressurization maintaining pressure slightly decreases. When the liquid level drops too low and transitions to gaseous supply, the pressure inside the tank rapidly declines. At an ambient temperature of −10 °C, the active-pressurization can still offset the pressure drop caused by the supply. However, higher ambient temperatures increase the temperature difference during, leading to a higher evaporation rate inside the tank. The active-pressurization flow rate was corrected by the ratio of the densities and viscosities of LN₂ and LH₂ to investigate the situation of active-pressurization to exceed the critical pressure. When the LH₂ tank is actively pressurized to the critical pressure, there is still a return gas temperature difference close to 170 K, which is much higher than the 0 K of LN₂, thereby promoting the active-pressurization rate. This study explored the active-pressurization capability and influencing factors of onboard LH₂ storage tanks through LN₂ experiments and system simulation methods, providing a foundation for precise control of the active-pressurization supply in onboard LH₂ systems.