Numerical Study On Vapor-Liquid Phase Change Of Cryogenic Medium Using LBM

With the development of cryogenic technology, cryogenic liquids such as hydrogen, oxygen have been widly used, especially in cryogenic propellant liquid rocket. The storage and safety issues of cryogenic liquid become a hot issue. Safe problem of storage actually is the problem of phase transition in low temperature. Due to the interaction between gas and liquid molecules, the phase change will be affected by the intermolecular interaction in low temperature more than in room temperature. The study on phase change of cryogenic liquid storage must be deep into the micro mechanism. Lattice Boltzmann Method (LBM) is very suitable to study the the mechanism of phase change and simulate the phase change process because it can display interactions between particles.A detailed description of the LBM including the boundary conditions, evolution equation, program implementation process and typical two-phase i.e. color model, energy model, pseudo potential model was introduced in this thesis. Based on LBM, a program was written and verified. The aggregation of droplets was predicted to to prove the existence of LBM phase interface. The evaporation of the droplet in low temperature was calculated by the phase change model with phase interface. The evaporation of the droplet could become faster with the increase of temperature. The transition phenomena of falling droplet under the actual gravity were also simulated.The LBM can be applied to the field of cryogenic liquid complex transformation.The LBM was combined with the actual cryogenic fluid. Based on the SC equation of state, the single component multiphase model integrated PT equation of state and the parameter adjustable force models was developed in this thesis to to study thermodynamic properties of cryogenic saturated fluid. The staturate density of four kind of typical cryogenic fluids,i.e. hydrogen, oxygen, nitrogen, helium was calculated by the model and verified by Maxwell theoretical solutions. The inverse relationship between the interfacial density gradient and the low temperature was obtained by analyzing the droplet and bubble in the calculating region. The LBM multiphase model was first applied to the actual cryogenic fluid. Furthermore, this thesis solved the problem that the simulation results and the theoretical values had deviation with different equations of state. The simulations using LBM have laid an important foundation for phase change in low temperature.