液化天然气排放形成的羽流过程数值研究

大量LNG溢出蒸发后将形成低温云团,对风向下游地面人员可能造成冻伤、燃烧以及缺氧窒息等危险。基于计算流体力学方法,构建了深低温两相多组分流动的Navier-Stokes方程以及湍流封闭方程,考虑了空气中水蒸气由于温度降低到饱和温度以下而相变传质过程。由于气相中氧气等非液化气体的存在,修正了计算水蒸气相变率的Hertz-Knudsen方程。详细给出了计算过程边界条件设置,评估了地球自转引起的科里奥利力影响特性。数值模拟了美国LLNL完成的Burro系列LNG排放羽流实验,发现考虑水蒸气相变的计算结果,相比于未考虑水蒸气相变的计算,更接近实验结果。研究结果对LNG接收终端等安全环境评估及设计有指导意义。

Numerical study on plume characteristics of liquefied natural gas spills

When a large number of LNG suddenly leaks and evaporates, it will form a low temperature cloud in the wind downstream, which may cause frostbite, burn and oxygen deficit hazard to the ground personnel. Based on the computational fluid dynamics (CFD) method, the two-phase multicomponent flow mathematical framework together with the turbulence closure are built to model the cryogenic flow. The phase-change mass transfer of water vapor in the air due to the temperature depression is considered. Because of the existence of non-liquefied gases such as oxygen, the Hertz-Knudsen equation for calculating the mass transfer rate of water vapor is modified. Detailed methods for setting the boundary conditions of the computational domain are presented and the influence of Coriolis force caused by the earth rotation is evaluated. The Burro experimental series of LNG released by LLNL are simulated and the results are used to evaluate the numerical models. It is found that the results using models with the phase change of water vapor are closer to the experimental results than that without the phase change. The studies are of directive significance for the safety environment assessment and design of LNG received terminal.