Diffusion Numerical Simulation Of Storage Tank Leak On LNG Bunkering Pontoon

The Yangtze River and other inland waterways are laying out plenty of Liquefied Natural Gas(LNG)Bunkering Pontoons.It is easy to form flammable and explosive vapor cloud to diffuse in the atmosphere and pose a serious threat to the safety of inland waterways,when storage tanks on the LNG Bunkering Pontoons leak.In order to analyze the diffusion characteristics and affected areas of vapor cloud that forms from the continuous leakage of storage tank on LNG Bunkering Pontoon,for the services of water transportation safety security work,choosing Computational Fluid Dynamics(CFD)method to carry out the diffusion distribution simulation research.First,typical leakage modes of storage tank are analyzed,and a simulation calculate method for storage tank continuous leakage strength is established.Using the established simulation calculation method,the storage tank continuous leakage process of a large LNG Bunkering Pontoon is simulated,and the two-phase flow leakage strength data of the storage tank under different storage conditions are obtained.Based on the analysis of the leakage forms of LNG storage tank and the data of leakage mass flow rate,vapor mass fraction calculated from dynamic simulation,the control equations of LNG flash vapor aerosol diffusion are established.Second,the calculation basin model for numerical simulation is built based on the theory of calculate wind engineering and the simulation experiments results of wind field.The discrete quality of the computational space is control by using split structure hybrid grid generation technique,obtaining a high quality hybrid grids.The wind field of the Bunkering Pontoon environment is simulated and a stable atmosphere of LNG flash vapor aerosol diffusion is established.The wind field calculation results show that air develops fully in the calculation basin outlet,complex flow characteristics including flow around,separation flow,vortex and wall stagnation are formed around Bunkering Pontoon.Based on the control equations of LNG flash vapor aerosol diffusion established and the wind field built before,by defining parameters such as leakage mass flow rate the diffusion process is calculated in transient.And the data of the maximum distance of downwind,maximum width,affected areas of LNG vapor at different times and different volume concentration are obtained,the characteristics of LNG flash vapor aerosol diffusion are analyzed by processing the calculate results.Analyzing the influences of wind speed on flash vapor aerosol diffusion find that: the smaller the wind speed,the larger the maximum width of the vapor cloud,the larger the area affected and the longer the time to reach steady state are;class 3 and below wind speed are the most dangerous situation of LNG Bunkering Pontoons leakage diffusion;downwind distance of LNG vapor cloud diffusion will be largest under class 2-3 wind condition.The analysis of flash vapor aerosol diffusion characteristics and wind speed effects,as well as the data of accident simulation obtained can be used to the safety security work of inland waterway transportation,such as guiding the work of LNG Bunkering Pontoons layout,navigation safety management and accident emergency treatments,et al.