Study on Evaporation Characteristics of Liquid Lithium Based on Underwater Unmanned Vehicle Surface Combustor

Abstract The novel energy propulsion system based on the Li/SF6 combustion reaction can be applied to an underwater unmanned vehicle (UUV). Investigating the evaporation characteristics of lithium in surface-type combustion chambers will significantly optimize the engineering design of the Li/SF6 power system's startup phase. This article, based on the operational requirements of the UUV surface-type combustion chambers, designs an E300 evaporation rate experiment apparatus, sets up an evaporation rate experiment system, conducts evaporation rate measurement experiments under different temperature conditions, and carries out a visual experimental study on the evaporation characteristics of lithium. Based on the experimental results and model validation results, the volume of fluid model and the Lee evaporation model coupled with the k–ω shear stress transport model, are used to conduct a numerical study on the evaporation process of liquid lithium inside the evaporation chamber, further analyzing the evaporation characteristics of liquid lithium within the chamber. The experimental results show that the evaporation rates of lithium are 0.14–0.71 g/m2·s in a pure argon atmosphere of 0.120 MPa at 1023–1373 K, respectively. It is observed that when liquid lithium is higher than 1023 K, an obvious thermal convection phenomenon exists on its surface. The simulation results show that there are surface heat accumulation, local turbulence, and transitional boiling phenomena in the evaporation process of liquid lithium.