Gavelli Filippo, Bullister Edward, Kytomaa Harri
Exponent, Inc., 17000 Science Drive, Suite 200, Bowie, MD 20715, United States.
J Hazard Mater. 2008 Nov 15;159(1):158-68. doi: 10.1016/j.jhazmat.2008.02.037. Epub 2008 Feb 17.
Recent discussions on the fate of LNG spills into impoundments have suggested that the commonly used combination of SOURCE5 and DEGADIS to predict the flammable vapor dispersion distances is not accurate, as it does not account for vapor entrainment by wind. SOURCE5 assumes the vapor layer to grow upward uniformly in the form of a quiescent saturated gas cloud that ultimately spills over impoundment walls. The rate of spillage is then used as the source term for DEGADIS. A more rigorous approach to predict the flammable vapor dispersion distance is to use a computational fluid dynamics (CFD) model. CFD codes can take into account the physical phenomena that govern the fate of LNG spills into impoundments, such as the mixing between air and the evaporated gas. Before a CFD code can be proposed as an alternate method for the prediction of flammable vapor cloud distances, it has to be validated with proper experimental data. This paper describes the use of Fluent, a widely-used commercial CFD code, to simulate one of the tests in the "Falcon" series of LNG spill tests. The "Falcon" test series was the only series that specifically addressed the effects of impoundment walls and construction obstructions on the behavior and dispersion of the vapor cloud. Most other tests, such as the Coyote and the Burro series, involved spills onto water and relatively flat ground. The paper discusses the critical parameters necessary for a CFD model to accurately predict the behavior of a cryogenic spill in a geometrically complex domain, and presents comparisons between the gas concentrations measured during the Falcon-1 test and those predicted using Fluent. Finally, the paper discusses the effect vapor barriers have in containing part of the spill thereby shortening the ignitable vapor cloud and therefore the required hazard area. This issue was addressed by comparing the Falcon-1 simulation (spill into the impoundment) with the simulation of an identical spill without any impoundment walls, or obstacles within the impoundment area.
最近关于液化天然气（LNG）泄漏到蓄水池中的后果的讨论表明，常用的SOURCE5和DEGADIS组合来预测可燃蒸汽扩散距离并不准确，因为它没有考虑风对蒸汽的夹带作用。SOURCE5假设蒸汽层以静止饱和气体云的形式均匀向上生长，最终溢出蓄水池壁。溢出速率然后用作DEGADIS的源项。一种更严格的预测可燃蒸汽扩散距离的方法是使用计算流体动力学（CFD）模型。CFD代码可以考虑控制LNG泄漏到蓄水池中的后果的物理现象，例如空气与蒸发气体之间的混合。在将CFD代码作为预测可燃蒸汽云距离的替代方法提出之前，必须用适当的实验数据进行验证。本文描述了使用广泛使用的商业CFD代码Fluent来模拟LNG泄漏测试“Falcon”系列中的一项测试。“Falcon”测试系列是唯一专门研究蓄水池壁和建筑障碍物对蒸汽云行为和扩散的影响的系列。大多数其他测试，如Coyote和Burro系列，涉及泄漏到水和相对平坦的地面上。本文讨论了CFD模型准确预测几何复杂区域中低温泄漏行为所需的关键参数，并比较了Falcon-1测试期间测量的气体浓度与使用Fluent预测的气体浓度。最后，本文讨论了蒸汽屏障在遏制部分泄漏从而缩短可燃蒸汽云以及因此所需危险区域方面的作用。通过将Falcon-1模拟（泄漏到蓄水池中）与相同泄漏但没有任何蓄水池壁或蓄水池区域内障碍物的模拟进行比较，解决了这个问题。
