低温推进剂贮箱压力变化的CFD仿真

为预示低温推进剂贮箱在地面停放阶段的压力变化并研究贮箱内物理过程的相互作用关系,建立了包含液体推进剂和混合气体两相的二维轴对称volume of fluid(VOF)计算流体力学(CFD)模型,并引入了基于热力学平衡假设的推进剂相变模型.对实验液氢贮箱进行仿真得到的压力上升速率与实验结果相差9.1%.通过对地面加压停放阶段下的液氢和液氧贮箱的仿真发现:造成液氢贮箱压力上升的主要因素是壁面漏热对气枕的加热作用,而液氢蒸发影响更小,液氧贮箱在加压停放阶段初期明显受到液氧相变的影响.两个贮箱中液面附近的对流运动在不同的气液传热过程作用下有不同的变化趋势,对流运动会影响推进剂的相变进而影响贮箱的压力变化.

CFD simulation of cryogenic propellant tank pressure variation

In order to predict the pressure variation and investigate the interrelation among the physical processes in cryogenic propellant tanks during ground parking, a 2-D axial symmetry volume of fluid (VOF) computational fluid dynamic (CFD) model was established, including a liquid propellant phase and a mixture gas phase. The propellant phase change model was cited based on the assumption of thermodynamic equilibrium. The difference between the simulated pressure rise rate and the test data of a test liquid hydrogen tank was 9.1%. The simulation results of the pressurized stage of liquid hydrogen tank and liquid oxygen tank during ground parking indicate that the heating on the ullage by the heat leakage from the inner surface is the key factor of the pressure rise in the liquid hydrogen tank, and the liquid hydrogen vaporization has comparatively less influence. However, the pressure in the liquid oxygen tank varies as the liquid oxygen phase transition changes at the beginning of the propellant pressurized parking stage. The pressure variations in these two tanks are both under the influence of the propellant phase change affected by the different change trends of the propellant convection induced by the heat transfer between the gas and the liquid.