在轨运行低温液氢箱体蒸发量计算与增压过程研究

Evaporation Calculation and Pressurization Process of on-Orbit Cryogenic Liquid Hydrogen Storage Tank

为了研究低温箱体在外部漏热下的在轨增压过程,采用FLUENT软件中的流体体积(VOF)方法,对AS-203飞行试验中低温液氢箱体进行数值模拟。通过对默认可实现k-ε模型进行参数调整,并与试验结果对比发现,调整参数后的模型可较好地预测低温液氢箱体在轨增压过程。因此,采用该模型对所研究低温液氢箱体进行500s增压数值模拟,计算结果表明:与气枕接触的壁面漏热绝大部分用来使箱体增压,小部分用来产生相变;在外部漏热下低温箱体压增速率约49.6Pa/s,箱体气液界面的蒸发率约为0.101 6%/h;在一定的微重力水平下,自然对流作用依然存在,其对流强弱主要取决于箱体尺寸以及外部漏热热流大小;在整个模拟过程中,气枕区热分层较之液相区更为严重;随着重力水平的降低,表面张力的作用逐渐凸显,界面形状变为曲面。

To investigate the on-orbit pressurization of cryogenic storage tank, the volume of fluid method in FLUENT is chosen to simulate the AS-203 flight experimental liquid hydrogen tank. Improving the original realizable κ-ε turbulence model and comparing with the experiment data, the modified model successfully predicts the on-orbit pressurization process of cryogenic liquid hydrogen storage tank. Therefore the calibrated realizable κ-ε model is adopted to research the liquid hydrogen storage tanks on-orbit pressurization for 500 seconds. The calculation shows that most of wall heat leakage increases the storage tank pressure, only a small part of external heat leakage facilitates vapor-liquid phase change. The pressure increase rate of the liquid hydrogen tank and the evaporation rate happened in the gas-liquid interracial, for the effect of external heat leakage, are about 49.6 Pa/s and 0. 1016%/hour respectively. Natural convection still exists under certain microgravity, and its intensity depends on the tank size and the external heat flux density. The thermal stratification of vapor region is more obvious than liquid region in the whole pressurization process. With the decreasing gravity level, the effects of surface tension are gradually prominent, and the gas-liquid interface shape becomes curved surface.