Thermodynamic Characteristics of Cryogenic Liquid Krypton Tank in Microgravity

The cryogenic liquid krypton tank will be in microgravity environment for more than several hundred seconds during MECO (Main Engine Cut-off) phase, its internal heat transfer and phase change have an important impact on the performance of the storage and supply system of the large orbit transfer vehicle. To investigate the pressure variation and temperature distribution of on orbit cryogenic liquid krypton tank in microgravity conditions, establishing a CFD model of cryogenic liquid krypton tank, the effects of gravity level, initial liquid krypton temperature and initial filling rate on the thermal stratification and pressure variation of liquid krypton tank in microgravity conditions were studied by using VOF method and Lee gas-liquid phase change theory. The results show that, in the microgravity conditions, the tank pressure rise rate are lower than that in the ground condition, a smaller gravity causes a smaller tank pressure, and the pressure rise rate of tank under g₀ is 1.84 times, 1.98 times and 2.04 times of 10^–4 g₀, 10^–5 g₀ and 10^–6 g₀ respectively, and the degree of temperature stratification (2~3 K) is much lower than that of ground condition (90 K). Under the microgravity level of 10^–4 g₀, the tank pressure decreases first and then increases gradually with time at different initial liquid krypton temperatures (133.5 K, 134 K, 134.5 K), and the lower the initial liquid krypton temperature is, the smaller the pressure rise rate of the cryogenic liquid krypton tank is. Under the microgravity level of 10^–4 g₀, there is a critical initial fill ratio (70%) of the cryogenic liquid krypton tank. When the initial fill ratio is larger than the critical value, the pressure rise rate increases with the increase of the initial fill ratio, and when the initial fill ratio is lower than the critical value, the pressure rise rate of the tank decreases with the increase of the initial fill ratio.