Abstract: Leakage and explosion accidents are often caused by gasket aging,perforated corrosion of pipeline,weld crack,outside force bump,poor management and other reasons in applications of liquefied natural gas(LNG).Research on LNG leak diffusion process will greatly reduce personal and economic loss.A study on LNG diffusion process is conducted for continuous leakage.The diffusion process is divided into two stages,heavy gas diffusion in initial stage and passive diffusion in the following stage.The first stage is described by SLAB steady plume dispersion model and the second stage uses Gaussian plume model.The transformation of heavy gas diffusion and passive diffusion is indicated by a stage transformation criterion.For vertical jet source,the releasing gas rises because of its initial momentum before gravitational diffusion.The rising height of plume is calculated.The mathematical model of LNG diffusion process is set up and used to simulate the diffusion of vertical leakage LNG under two environmental conditions.The concentration profile,temperature profile and other characteristic parameters of mixing clouds after leaking are calculated.The heat and mass transfer between LNG and the environment is analyzed.The influence of heavy air on the diffusion process is explained.These results are helpful in determination of damage range of accident,evacuation of people and guidance of rescue work.

Key words: LNG, continuous leakage, vertical jet release, heavy gas diffusion, passive diffusion

摘要： 对液化天然气(LNG)扩散的物理过程进行了理论分析。针对垂直喷射源连续泄漏扩散特点,将液化天然气扩散过程分为重气扩散与被动扩散两个阶段。结合烟羽抬升计算,在两个阶段分别采用SLAB稳态烟羽模型与高斯烟羽模型,建立了液化天然气扩散过程数学模型。研究了垂直喷射源泄漏形式和不同环境条件下的扩散情形。对液化天然气泄漏后混合云团扩散形成的浓度场、温度场和其他特征参数进行了模拟。得到重气扩散阶段随下风向距离增大,扩散云团高度、宽度、温度、密度、云团中液化天然气蒸气含量、水含量的变化规律,被动扩散阶段云团中液化天然气质量分数的变化情况。可以为事故危害范围的测定、事故后人员的疏通和补救工作的指导提供帮助。

关键词: 液化天然气, 连续泄漏, 垂直喷射源, 重气扩散, 被动扩散