Simulation Study Of Liquid Hydrogen Tank Filling Characteristics And Thermal Stress Of Inner Liner

Liquid hydrogen has the advantages of high calorific value of combustion,high density of hydrogen storage,fast refilling and convenient transportation,etc.It is one of the most promising hydrogen energy storage and transportation methods at present.In the future,filling fixed or mobile liquid hydrogen tanks with liquid hydrogen will be a routine operation in the civilian sector.In order to achieve safe,efficient and economic liquid hydrogen filling,research on liquid hydrogen filling characteristics and structural stability of the liner is needed to provide technical support for liquid hydrogen filling.Therefore,in this paper,a small vertical liquid hydrogen storage tank with 34 L inner water volume is used as the research object,and the research on the characteristics of liquid hydrogen filling and the stability change law of inner tank structure under different filling process conditions is carried out,and the research results have important reference significance for the liquid hydrogen filling process and tank structure design optimization.(1)Firstly,a numerical model of liquid hydrogen refueling was established based on FLUENT software,and the Lee model and selfcompiled UDF program were introduced to simulate the phase change problems such as evaporation,condensation and flash evaporation of liquid hydrogen in refueling.The results show that the pressure change in the tank during the liquid hydrogen filling process can be divided into three stages: initial rapid pressure rise,relatively stable stage and final rapid pressure rise.When the inlet fluid temperature increases,it is found that the more intense the flashing in the pre-filling period,the higher the initial stage pressure rise.Initial wall temperature affects the wall vaporization pressurization effect at the beginning of refilling.The initial pressure has a large influence on the pressure change at the beginning of the refill.When the initial pressure is higher than the saturation pressure corresponding to the liquid hydrogen,no flash effect occurs in the tank.(2)Secondly,the indirect coupling method was used to load the temperature field of CFD numerical solution as thermal boundary conditions into the structural analysis,and the study of thermal deformation and thermal stress on the inner liner wall was carried out with the help of ANSYS Workbench static structural analysis module.The results show that the maximum deformation of the inner liner wall axially and radially does not exceed 2.4mm and 1mm respectively,and the maximum stress is less than the permissible stress of the inner liner material within the range of the filling process conditions set in this paper.The connection parts of upper and lower heads and cylinder have high stress level,the stress in the middle annular area of lower head and half height of cylinder is relatively small,and the stress in the middle annular area of upper head increases significantly when the initial wall temperature is greater than 70 K.In terms of the degree of influence on the amount of deformation and stress in the liner,the initial wall temperature > inlet fluid temperature > inlet fluid flow > initial pressure.(3)Based on the results of the study,the optimization of the liquid hydrogen refueling process is based on the following ideas: to ensure a high inlet flow rate to achieve a short refueling time;to reasonably lower the inlet temperature and/or increase the initial pressure to control the flash boosting effect at the initial stage of refueling;to reasonably lower the initial wall temperature to weaken the vaporization boosting effect at the initial stage of refueling.