CFD Modeling And Influence Factor Analyzing Of Large-scale Liquid Hydrogen Spills

As an important clean energy source,hydrogen has been widely used in the fields such as chemical engineering,clean energy and aerospace propulsion in the past several decades.Hydrogen at room temperature is gaseous and has low energy density.For the large-scale storage,transportation and application,hydrogen in liquid form is more economical and feasible,and is expected to get rapid development.However,due to the physicochemical properties of hydrogen itself,once the stored liquid hydrogen leaks,the leaking liquid hydrogen will form a cryogenic liquid pool on the ground,and the hydrogen formed by rapid evaporation of liquid hydrogen will accumulate under certain circumstances.The formation of explosive mixtures constitutes the surrounding population and the environment a huge potential threat.It is of great significance to study the mechanism of leakage and diffusion of large-scale liquid hydrogen,to formulate contingency plans,to define emergency evacuation areas and to assess the consequences of accident hazards.In this paper,a numerical model for large-scale liquid hydrogen spills with the help of the CFD software FLUENT was established,based on the comprehensive study of related research achievements at home and abroad.Considering the significant influence of wind field on the dispersion of liquid hydrogen,the simulation is divided into two steps.Firstly,the wind field in the atmospheric boundary layer is numerically simulated.Secondly,the simulation for the spills with the results of the converged wind field taken as the initial condition.In the process of establishing the wind field model,the basic characteristics of wind,as well as the main properties of pulsating wind,were analyzed.The mathematical expressions for mean wind profile and turbulence parameters were determined,which are achieved by user-defined functions.After determining the computational domain and generating mesh,Realizable k-s model was chosen as the turbulence model of the wind field.Then the wind field in the large environment was simulated.With the simulation results of the wind field as the initial conditions,numerical simulation of large-scale liquid hydrogen leakage and dispersion process was carried out.The Mixture model is chosen as the multiphase flow model.Based on the ground conditions in the experiment,constant temperature condition was determined,with the physical properties of sand.The leakage and dispersion processes of liquid hydrogen were simulated in unsteady state.The accuracy of the model was verified by comparison with NASA's experimental results.The simulation results showed the dynamic processes of hydrogen dispersion figuratively.Based on the established model,the changes of air temperature,wind speed,ground temperature,ground roughness,liquid hydrogen leakage rate and cavitation rate on leakage outlet were analyzed.The results of this study are helpful to establish a more accurate numerical simulation model for the behavior of large-scale liquid hydrogen spills and to establish the follow-up remediation and protection measures for large-scale liquid hydrogen leakage accident.