竖直管道内闪蒸界面传播现象的数值研究

NUMERICAL STUDY ON FLASHING FRONT PROPAGATION PHENOMENON IN VERTICAL TUBE

闪蒸界面传播是一种特殊的闪蒸现象,广泛存在于航天器真空环境下的排液过程中.闪蒸界面传播规律的深入研究是完善闪蒸机制,预测真空排液过程,提升航天活动可控性、安全性的重要前提.闪蒸界面传播现象研究目前主要依赖于实验观测,缺乏适合的数值方法.为了避免跨尺度模拟带来的庞大计算量,文章对计算域进行分区,在各分区内建立面密度模型,实现了单一工况下的闪蒸界面传播二维数值模拟.在此基础上,还提出闪蒸界面面密度的气相Weber数修正模型.该模型对不同温度压力条件下的界面微观形态特征进行代数表征,从而令数值模拟能够计算预测不同温度和压力工况条件下的闪蒸界面传播表观速度.最后,模拟了相同出口压力、不同名义过热度条件下的闪蒸界面传播现象,以及相同名义过热度、不同出口压力条件下的传播现象.计算结果表明,当出口压力恒定时,闪蒸界面处的真实过热度以及界面传播表观速度都随名义过热度的增加而增加.且在过热度较小时,真实过热度以及名义过热度都与闪蒸界面传播表观速度之间近似呈线性关系.当名义过热度恒定时,闪蒸界面传播表观速度会随出口压力的增加而增加.

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.