大型液化天然气储罐内液体内分层和翻滚影响因素分析

Analysis of influential factors on liquid stratification and rollover in large-scale LNG container

液化天然气(LNG)的储存温度和组分的变化都会引发诸多问题,如分层、翻滚、蒸发等。基于双扩散理论和黏性流体方程,建立了紊流态LNG分层和翻滚演变的数学模型。模型的模拟计算结果可以直观地看到LNG分层和翻滚演变过程。模拟结果表明,LNG的分层是产生翻滚现象的根本原因,储罐内LNG受热后的热边界层的流动是产生翻滚的直接原因,利用紊流态LNG分层与翻滚演变模型对影响LNG分层、产生翻滚的各种因素进行了分析,得出当漏热强度超过30W.m-2后,改变漏热强度,对翻滚现象的产生时间影响不大;当储罐的充满率均为70%时,储罐的容积越大,储罐内的LNG分层发生翻滚的时间越长。为预防LNG储罐发生翻滚的各种措施提供了理论依据。

Many problems would be induced by the change in LNG tank temperature or components. Such as the stratification and rollover phenomena in large-scale LNG container, and the evaporation in closed small-scale container, etc. A mathematical model for LNG stratification and rollover under the condition of disturbed flow is established based on the equation of viscous fluid. Through numerical simulation, the developing processes of LNG stratification and rollover can be visually observed. The numerical simulation results revealed that the stratification of LNG is the basic reason for the rollover phenomenon, and the flow of thermal boundary layer inside the LNG tank is the direct cause for the rollover of the LNG stratification. By virtue of the disturbed flow model, various factors which affect the rollover phenomenon were analyzed. When the heat leakage is greater than 30 W · m^- 2, the changes in heat leakage value has little effect on the rollover time. When the tank is 70% full, the rollover happening takes longer time as the container volume increases. The measures for preventing LNG stratification are proposed.