升空过程中低温液氧贮箱压力变化及热分层研究

Research on Pressure Change and Thermal Stratification of Cryogenic Liquid Oxygen Tank during the Ascent Process

针对火箭升空过程,通过编写用户自定义程序详细考虑了气动热以及空间辐射热的影响,数值研究了低温液氧箱体压力变化及流体热分层现象。在计算过程中,着重考虑了大气物性参数随高度的变化、飞行过程中加速度变化与气液界面相变对箱体压力以及箱内流体温度分布的影响。模拟结果表明:气动热对箱体控压频率产生了较大的影响。随着气动热流的增加,箱体增压时间变短,降压时间变长。在飞行120s时,气动热流达到最大,其对箱体压增性能的影响也最为突出,此时箱体增压时间最短为4s,箱体降压时间最长,约13s。在无排液阶段,箱体压力呈现波动变化,气液界面处气枕被冷凝。在该过程中,液相质量增加了11.05kg,气相质量减少了1.52kg。在增压排液阶段,尽管增压气体持续注入箱内,箱体压力仍逐渐减小,而气相质量则呈波动增加。随着时间的延长,气液相温度均向温度升高的方向推进。由于空间辐射漏热造成了排液温度的升高,给发动机运行带来安全隐患,应采取有效绝热措施来减少空间漏热。

A numerical simulation method was adopted to study the pressure change and fluid thermal stratification in liquid oxygen tank during the ascent process by a user-defined function （UDF） considering the aerodynamic heat and space radiations. The influences of atmosphere physical parameters, flight acceleration and phase change occurring in the liquid-vapor interface on the tank pressure and fluid temperature distribution were taken into account in the present numerical model. The calculation results showed that aerodynamic heat has great influence on the tank pressurization frequency and with the increase of aerodynamic heat flux, the tank pressurization time increases and depressurization time reduces gradually. After 120 s flight, the aerodynamic heat flux reaches its maximum value, and its influence on the tank pressurization behavior becomes most prominent. At this moment, the minimum tank pressure rise time and the maximum tank pressure reduction time are 4 s and 13 s, respectively. During the pressurizationprocess without outflow, the tank pressure fluctuates within the set pressure range, and the phase change is condensation at the interface. The liquid mass increases about 11.05 kg while the ullage mass decreases about 1.52 kg in this process. When it is in the outflow period, the tank pressure decreases with the continuous injection of pressurized gas, and the ullage mass shows a fluctuating increase. Both the gas and liquid temperatures boost to higher temperatures with time. As the space radiation leakage leads to the temperature increase of drainage liquid, and hence resulting in safety issues for the rocket engine, some effective measures should be taken to reduce the space leakage.