基于LBM方法的低温介质相变模拟研究

发布时间：2018-04-28 21:30

本文选题：低温 + 相变　；参考：《东南大学》2015年硕士论文

【摘要】：随着低温技术的发展,诸如液氢、液氧等低温液体越来越得到普及,特别作为低温推进剂在液体火箭中得到应用,所以低温液体的制取以及贮存方面的安全问题也越来越得到重视。贮存安全问题主要研究的是低温相变问题,而和常温相变问题不同,对于低温相变问题因为低温气液分子之间的相互作用力更加会影响到相变发生,所以低温液体的贮存相变方面的研究必然要深入到微观机理方面,所以本文利用基于微观的格子Boltzmann方法(Lattice Boltzmann Method简称LBM)中粒子与粒子之间的相互作用力来促使气液相变和相分离来研究低温相变问题。本文首先阐述了LBM演化方程、边界条件设置、两相流模型及编程思路。然后基于LBM多相模型利用Fortran编制程序模拟出液滴的聚集,证明了LBM相界面的存在。利用相界面结合相变模型发展了LBM多相模型,模拟出低温液滴的蒸发过程,分析在低温环境下不同的过热度下,液滴的蒸发速率会随着过热度变大而变快。在给定了具有重力的实际过程中,模拟出液滴在垂直管道中不断进行气液相变的现象,初步将格子Boltzmann理论应用于低温液体复杂相变领域。本文最后将LBM与实际的低温流体进行相结合分析,利用Fortran编制程序,基于引入状态方程的参数可调整型单组分相变模型,将PT状态方程引入该模型发展了单组分多相模型并进行了验证,通过模型成功对氮、氢、氧、氦,这四种典型的低温实际流体进行模拟研究,将模拟结果与Maxwell理论解进行比较分析,得出基于PT状态方程的模型最优值。在最优值的基础上,将液滴和气泡置于计算区域中,分析得出界面密度梯度与温度之间成反比关系。LBM多相模型第一次应用到实际的低温流体工质中,同时利用作用力模型解决了理论解与模拟值的偏差问题,具有非常重要的工程意义,也为揭示低温工程相变现象的机理奠定了LBM理论基础。
[Abstract]:With the development of cryogenic technology, cryogenic liquids such as liquid hydrogen and liquid oxygen are becoming more and more popular, especially used as cryogenic propellants in liquid rockets. Therefore, more and more attention has been paid to the production and storage of cryogenic liquids. Storage safety is mainly concerned with phase transition at low temperature, but different from phase transition at room temperature, phase transition at low temperature is more affected by interaction between gas and liquid molecules at low temperature. Therefore, the research on the storage phase transition of cryogenic liquids must go deep into the microscopic mechanism. Therefore, the interaction between particles and particles in lattice Boltzmann Method based on microcosmic lattice Boltzmann method is used to promote the gas-liquid phase transition and phase separation to study the phase transition at low temperature. In this paper, the evolution equation of LBM, the setting of boundary conditions, the model of two-phase flow and the programming idea are introduced. Then the aggregation of droplets is simulated by using Fortran program based on LBM multiphase model, which proves the existence of LBM phase interface. The LBM multiphase model is developed by using the phase interface and phase transformation model, and the evaporation process of the droplet at low temperature is simulated. It is analyzed that the evaporation rate of the droplet will become faster with the increase of the superheat at different superheat degrees in the low temperature environment. In the given actual process with gravity, the phenomenon of continuous gas-liquid phase transition of droplets in vertical pipes is simulated, and the lattice Boltzmann theory is applied to the complex phase transition field of cryogenic liquids. In the end, the LBM is combined with the actual low-temperature fluid, and the program is compiled by Fortran, based on the parameter adjustable one-component phase transition model with the introduction of the equation of state. The PT equation of state was introduced into the model to develop and verify the multiphase model. The simulation of nitrogen, hydrogen, oxygen, helium and four typical low-temperature real fluids was carried out. The simulation results are compared with the Maxwell theoretical solution and the optimal value of the model based on PT equation of state is obtained. On the basis of the optimum value, the droplets and bubbles are placed in the calculation area, and the inverse relationship between the interface density gradient and the temperature is obtained. The LBM multiphase model is applied to the practical low-temperature fluid for the first time. At the same time, the problem of deviation between the theoretical solution and the simulated value is solved by using the force model, which has very important engineering significance and lays the LBM theoretical foundation for revealing the mechanism of phase transition in low temperature engineering.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V511.6

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