液氢泄漏事故中氢气可燃云团的扩散规律研究

Investigation on the Hydrogen Flammable Cloud Dispersion in Liquid Hydrogen Leakage Accident

针对液氢生产、储存、运输过程中发生瞬时大流量泄漏的问题,对美国国家航空航天局进行的液氢泄放实验进行了数值模拟。采用非均相的混合模型,考虑气液相间速度滑移,对氢气、空气云团内部浓度、温度、密度等物理量的动态变化规律,以及可燃云团在竖直方向的扩散范围进行研究,揭示了可燃云团在开放空间的动态扩散行为,其扩散行为分为重气扩散、浮升扩散和被动扩散3个阶段。浮升扩散阶段为可燃云团扩散的最主要阶段,发生在停止泄放后大约8s的很短时间内,氢气浓度急剧下降,云团快速脱离地表并升高至约30m,在被动扩散阶段可燃云团扩散最慢,却占据大部分时间,即大约60s的时间,此阶段可燃云团维持在约40m的高空并且随风飘移。在风速较低的工况下,温差导致的低温氢气与空气的局部湍流相混合,是可燃云团扩散的主要动力。

Aiming at the problem of massive liquid hydrogen leakage in the processes of production,storage and transportation,a CFD model was built based on an assumed large scale leakage accident,and the liquid hydrogen leakage experiment of NASA(National Aeronautics and Space Administration)was simulated,where the non-homogeneous equilibrium model was adopted considering the slip velocity between liquid phase and vapor phase.The dispersion behavior of the flammable cloud was revealed based on the analyses on the concentration,temperature and density of H 2/air mixture cloud.There are three phases in the flammable cloud dispersion,i.e.,dense gas dispersion,drift dispersion and passive dispersion,among them the drift dispersion is the major phase occurring shortly(about 8 s)after the tapping of liquid hydrogen is shut off.At this time,the concentration of hydrogen decreases dramatically,and the cloud gets off the ground quickly and arises to a height of approximately 30 m.The hydrogen disperses most slowly in the passive dispersion phase,taking approximately 60 s,and the cloud is driven by the wind at a height of almost 40 m.At a relatively low wind speed,the major drive force of the dispersion is the local turbulent mixing caused by the great temperature difference between the cryogenic hydrogen gas and air.