Experiment And Numerical Study On Ice Formation Of Cryogenic Liquid Leaking Underwater

A collision accident with an LNG ship caused the cargo tank to rupture,possibly causing LNG leakage.According to the location of the rupture of the LNG ship accident,the leakage can be divided into surface leakage and underwater leakage.This paper uses liquid nitrogen instead of LNG for underwater leakage experiments.Designed and built an experimental system of cryogenic liquid leakage into ice.The platform system can be used to conduct underwater leakage ice formation experiments with different leakage apertures,leakage pressures,rotating flow fields,and the addition of nucleating agents.It can also monitor underwater phenomena and changes in water temperature.Based on the basic jet theory and jet instability theory,the phenomenon of liquid nitrogen leaking into ice was analyzed.The concept of "blocking" of liquid nitrogen into ice is defined,and the time during which liquid nitrogen leaks into ice is counted.The liquid nitrogen underwater leakage jet is divided into four parts:ice layer,initial section,main section and floating section.The phenomenon of liquid nitrogen leaking into water under different pore diameters and pressures was analyzed,and the thickness of ice formation at the leak hole and the position of ice breakage were analyzed.By comparing and analyzing the change of the living distance of the cryogenic liquid column,it is found that the pore diameter of the leak hole is relatively small when the pore diameter is 1mm and 2mm,and the impact of the pressure change on the living distance of the cryogenic liquid is greater than that of the pore,diameter;Relatively large,the effect of the pore size on the survival distance of the cryogenic liquid column is greater than the change in pressure.Compared with the nucleating agent with and without nucleating agent,the low-temperature liquid survival distance,plugging time and water temperature changes.The experimental results show that the addition of nucleating agent can increase the probability of liquid nitrogen leaking into ice underwater.By adding the nucleating agent and the whole water area are nucleating agents,the temperature curve of the water area changes,it is obtained that when the leakage pressure is low(the pressure is less than 3.0bar),the addition of the nucleating agent provides a different phase for the water near the leakage hole The impact of the nucleation point and the flow of the nucleating agent causes the liquid nitrogen interface to break,which is the main reason for the increase in the probability of ice formation at the leak hole;when the leakage pressure is high(pressure greater than 3.0 bar),the nucleating agent provides a heterogeneous nucleation point for water,Thereby reducing the supercooling of water,is the main reason for the increase in the probability of freezing.Different types of propellers were carried out,and liquid nitrogen underwater leakage experiments and rotating flow fields were simulated at different speeds and positions.It was concluded that the rotation of the propeller can increase the probability of ice formation near the leak hole,and its change is mainly related to the propeller speed.Through experimental research,it is found that the environmental flow field has a great influence on the underwater leakage process of cryogenic liquids.In view of this,this study uses FLUENT software to simulate the environmental flow field such as rotating flow field,water flow velocity and direction,etc.mechanism.Through the use of FLUENT to simulate the rotating flow field,it is found that the change in pressure under the rotation of the propeller is a factor that leads to an increase in the probability of ice formation near the liquid nitrogen leakage hole.By simulating the icing process under water flow,the effects of parallel wall flow and vertical wall flow on ice thickness are analyzed,and it is concluded that the parallel horizontal wall flow has a greater effect on the wall icing ice thickness than the flow perpendicular to the wall direction Influence;In the experiment of adding nucleating agent,the impact of the nucleating agent flow on the liquid nitrogen flow caused the interface instability of the liquid nitrogen flow,which was the key factor for the nucleating agent flow to promote the freezing of regional water.In addition,FLUENT software was used to simulate the distribution of the multi-phase flow pattern of low-temperature liquid underwater leakage,and the accuracy and reliability of the model were verified by comparison with the experimental results.