NUMERICAL STUDY ON FLASHING FRONT PROPAGATION PHENOMENON IN VERTICAL TUBE

The flashing front propagation phenomenon is a special kind of flashing phenomenon, which widely exists in the liquid discharge process of spacecraft in vacuum environment. The in-depth study of flashing front propagation is an important prerequisite for improving the research of flashing mechanism, predicting the liquid discharge process in vacuum, and promoting the controllability and safety of space activities. At present, the study of flashing front propagation phenomenon relies on experimental observation and lacks practical numerical methods. In order to avoid the huge amount of calculation brought by the cross-scale simulation, the calculation domain is divided into different regions, and an interfacial area concentration model is established in each region, thus realizing the two-dimensional numerical simulation of flashing front propagation under a single working condition. On this basis, this paper also proposes a modified gas-phase Weber number model for flashing front interfacial area concentration. This model characterizes the micromorphology of the interface under different temperature and pressure conditions, so that the numerical simulation can calculate and predict the superficial velocity of flashing front propagation under different temperature and pressure conditions. Finally, this paper simulates the cases under constant outlet pressure and different nominal superheat, and the cases under constant superheat and different outlet pressure. The results show that when the outlet pressure keeps constant, both the real superheat at flashing front and the superficial velocity of flashing front propagation increases with the increase of the nominal superheat. And under low superheat, both real superheat and nominal superheat are approximately linear with the superficial velocity of flashing front. For cases under constant nominal superheat, the superficial propagation velocity is positively correlated with the outlet pressure.