Numerical Study Of Transient Flow In Pipeline Transporting Liquefied Natural Gas

In recent years,the market of international trade of liquefied natural gas(LNG)is developing faster and getting bigger.So is it in China,which has greatly reduced the tension relationship of energy supply and consume in east of China.The LNG receiving terminate is the core part of LNG trade.The high flow rate,large pipeline diameter and low temperature property of LNG make the process of transferring LNG from cargo ship to storage tank in land much more dangerous.Thus,we need pay much attention on the transient flow in transferring pipeline and choose the proper and safe pipeline parameters.In general,engineers employee the commercial software to get the pipeline parameters and working parameters.However,we do not know how the software calculates the parameters in details and the results from commercial software are conservative.In this paper,a numerical calculating model by Method of Characteristics(MOC)is developed to simulate the pressure fluctuation in pipeline and offer guidelines to the design of transferring system.First,the new model is evaluated by comparing results from numerical method with experimental data in reference.Secondly,a pump-valve-tank calculating model is developed to study how to lower the pressure fluctuation in pipeline by adjusting the valve closure rule.Thirdly,the calculating model based on parameters in project of Zhoushan receiving terminate in China is developed to verify the rationality of project design.At last,two different designs are calculated and compared with that in real project: installation of 2/7s two stage closure valve at the outlet of pump and installation of tank of stabilizing pressure at the outlet of pump.The results show that the model based on MOC could accurately capture the maximum and minimum pressure in LNG transferring pipeline.The pressure fluctuation in pipeline could be well controlled by keeping the fast close time of valves uniform in pipeline.We also prove that the design pressure of the pipeline and working pressure in LNG cargo ship are correct and proper.At last,it proves that installation of 2/7s two stage close valve could lower the maximum pressure in pipeline but rise the maximum of pressure reduction.The maximum pressure reduced 21%.In designing of transferring system,this method could be considered and employed.The second method,installation of tank of stabilizing pressure,can not only reduce the maximum pressure in pipeline but also lower the maximum pressure reduction.The maximum pressure reduced 27%,and minimum pressure increased 32%.At the same time,it could serve as the storage tank in LNG receiving terminate.Thus,this method is suggested to be adopted in real project,which could greatly reduce the investment of transferring pipeline system.