大型LNG储罐连续泄漏扩散过程影响因素的分析

Analysis on influencing factors of LNG continuous release & dispersion process from large scale tank

考虑接收站内大型液化天然气(LNG)储罐泄漏射流、液池蒸发、气云扩散3个过程的特点,结合相平衡原理和气体连续扩散高斯模型,采用欧拉多相流模型进行数值模拟,并开展风速、泄漏速率和地面粗糙度对其影响的研究。结果表明:大型LNG储罐连续泄漏气云扩散过程按泄漏扩散的形态可分为重气扩散(气云受热)、被动扩散、稀释消散3个阶段;在LNG储罐背风面泄漏口附近形成24m区域内的回流和大尺度漩涡,该区域的风速减小了70%~80%;随着风速增加,甲烷浓度0.5LFL水平扩散距离在3个阶段分别减小了20%,增大了50%,减小了23%,且甲烷浓度为0.5LFL的水平扩散最远距离和液池扩展长度均随风速的增加而减小;随着泄漏速率的增加,射流长度、池长和池径均有所增加,甲烷浓度0.5LFL水平扩散距离在3个阶段分别增加了42m、33m和45m;随着地面粗糙度的增加,池径和池长均减小,气云前端扩散面高度分别增加了15.5m、25m和16m。另外,通过研究风速、泄漏速率、地面粗糙度3个因素对LNG气云扩散的影响,确定LNG气云扩散水平方向和高度方向上的敏感影响因素。

Considering the characteristics of three processes of large scale LNG tank leakage jet,pool evaporation and gas cloud dispersion in receiving terminal,combined with phase equilibrium principle and gas continuous diffusion Gauss model,Euler multiphase flow model was used to simulate the process.By studying on the effects of wind speed,spill rate and ground roughness of it,the results showed that the diffusion process of continuous leaking gas cloud in large LNG storage tank can be divided into three stages according to the form of spilling dispersion:heavy gas diffusion(heating of gas cloud),passive diffusion and dilution dissipation.The backflow and large-scale eddies in the area of 24m near the leakage hole of LNG tank were formed,and the wind speed in this area was reduced by 70%—80%.With the increase of wind speed,the 0.5LFL downwind distance of methane concentration decreased by 20%,increases by 50%and decreases by 23%in the three stages,respectively.the maximum 0.5LFL downwind distance of methane concentration and pool length expansion decreased with increase of wind speed.With increasing spill rate,the jet length,pool length and pool radius all increased and the 0.5LFL downwind distance of methane concentration increased by 42m,33m and 45m in three stages.With the increase of surface roughness,the pool radius and length all decreased.The height of dispersion surface at the front of gas cloud increased by 15.5m,25m and 16m.In addition,by studying the influence of wind speed,spill rate and ground roughness on LNG gas cloud dispersion,the sensitive factors in horizontal direction and altitude direction of LNG gas cloud dispersion were determined.