液氮贮箱常压停放实验与数值仿真

Experiment and numerical simulation of liquid nitrogen tank atmospheric ground parking

为研究低温推进剂的常压停放过程,设计了可视化液氮贮箱实验系统。实验中研究充填率和环境温度对液氮汽化量的影响,并测量贮箱内流体和贮箱外壁面的温度随时间和位置的变化。实验得出贮箱常压停放过程,相变主要在壁面和气液界面产生,并且气枕区存在温度分层,距出口位置越近温度越高;而液体区温度基本一致,处于饱和状态。贮箱外壁面在轴向的温度分布显著不同,处于液体区壁面温度低。运用分子动力学推导出的HertzKnudsen公式作为气液相变的传热传质源项,并据实验测得温度边界条件,采用混合物模型对贮箱常压停放状态进行30 min的数值仿真。仿真得到结果显示体积汽化速率与实验数据的偏差在5%以内,液体区的温度仿真与实验的偏差在0.15 K左右。

In order to study the progress of the cryogenic propellant during atmospheric ground parking, a visualization liquid nitrogen tank experiment system was designed. The experiment researched how the filling rate and ambient temperature affected the evaporation mass of liquid nitrogen, and measured the fluid inside tank and the wall temperature outside tank which changed with the time and location. The experimental results show that during atmospheric ground parking the phase transition mainly happens in the wall and gas-liquid in- terface, air pillow zone has temperature levels, and the air pillow temperature increases with the decrease of the distance from the exit. The liquid stays in the saturated state with almost consistent temperature, and the outer wall temperature distribution of the tank is significantly different in the axial direction and lower in liquid zone. The heat and mass transfer between liquid and gas is deduced from the Hertz-Knudsen equation based on the molecular dynamics theory. According to the temperature boundary conditions acquired from the experi- ment, physical process of 30 min in liquid nitrogen tank during atmospheric ground parking was simulated using mixture model. The simulation results show that the deviation of volume vaporization rate between simu- lation and experiment is within 5% , and the deviation of temperature simulation and experiment in the liquid zone is about 0.15 K.