Study On The Influence Of Evaporation Of Liquefied Natural Gas Under Cargo Sloshing

When influenced by factors such as wind,ocean wave and currents,the offshore liquefied natural gas-floating storage and regasification units(LNG-FSRU),liquefied natural gas carriers and liquefied natural gas-floating production storage and offloading units(LNG-FPSO)are in the unstable condition of motion.LNG sloshing may happen in the tanks when LNG tanks are in partial filling levels.Sloshing causes problems such as the damage of tanks base structure in wave impact force.In the situation of tank sloshing,fluctuations of fluid pressure,temperature and gas flow velocity may affect the gasification of LNG and eventually lead to aggravate the evaporation rate of LNG.The cargo sloshing affects the Offshore LNG-FSRU cryogenic liquid storage and transportation performance of tanks containment system and reduce the economy and safety of LNG storage and transportation.Carrying out the research on the influence of LNG evaporation under cargo sloshing is significant to engineering security and economy and can provide theoretical basis for the safety and efficiency operation for LNG-FSRU.In order to study the influence of the evaporation of LNG on the liquid sloshing inside the tanks,this thesis simulates the LNG sloshing and evaporation respectively based on the large commercial Computational Fluid Dynamic software ANASY FLUENT.The specific contents are as follows:1)Based on the physical model test,VOF explicit multiphase flow model is adopted for LNG sloshing phenomenon inside the tanks.Compared with the test results of LNG free surface,the rolling torque and the pressure distribution,the numerical simulation model and algorithm of LNG sloshing analysis are designed;2)Based on the theory calculation formulas of LNG evaporation,user defined phase transformation model is used for static evaporation of LNG inside the tanks.Compared with the theoretical calculation results of the LNG evaporation rate,the LNG evaporation numerical simulation model and algorithm are determined;3)Combining the research of LNG sloshing numerical analysis with the numerical simulation of LNG static evaporation,the numerical study on the LNG evaporation under the sloshing condition is done.By calculating under conditions of different sloshing amplitude and different sloshing period,the thesis studies influences of sloshing amplitude and sloshing period on the evaporation of LNG.The results show that the evaporation of LNG increases with the sloshing amplitude increasing.And when the sloshing period is close to the natural period of the tank,the evaporation of LNG is large and if the sloshing period is more than the natural period the evaporation of LNG is small.