煤油贮箱冷氦鼓泡增压过程数值研究

火箭飞行过程中，约90 K的低温氦气用以加压室温下的煤油贮箱使煤油流出，保障发动机燃料供应。为尽可能减少氦气用量，设计低温氦气从液相中喷入，使得氦气在贮箱内上升过程先和液态煤油充分换热升温，再进入气相空间增压。但该过程可能引起两个不利的结果，首先浸没在煤油中的低温氦气管路表面可能结冰，结冰沉底或可能堵塞发动机滤网；其次氦气可能被煤油携带，从而排出口位置可能出现气液两相流。这两种情况都对火箭发动机稳定运行造成负面影响，因此是不允许的。对低温氦气在贮箱中心喷入和环向多孔喷入两种结构的气液两相流过程进行了数值研究，构建了基于Euler-Euler模型的两相传热非稳态模型，数值结果与地面实验观察到的现象进行了定性对比，定性验证了模型的准确性。重点考察了煤油排出过程两种喷入结构的气液两相流分布以及煤油结冰可能性。研究结果从机理上解释了实验现象，并为煤油贮箱增压排出方案设计提供了参考。

Numerical investigation on cold helium pressurization process in kerosene tank

During the flight of the rocket, a low temperature helium gas of about 90 K is used to pressurize the kerosene tank at room temperature to allow kerosene to flow out to ensure the supply of engine fuel. In order to reduce the amount of helium, the cryogenic gas is designed to inject into the tank under the liquid level, in which way it can absorb the heat from the liquid kerosene in the tank while rising, and then enters the gas phase to pressurize the tank. However, this process may lead to two unfavorable results. First, the surface of the cryogenic helium gas line immersed in kerosene may freeze, and the ice may sink to the bottom to block the engine screen. Second, the helium gas may be carried by kerosene, thus two-phase flow will appear at the discharge port. Both of the circumstances have an adverse impact on the operation of the rocket engine, and therefore neither of them is allowed. In this paper, numerical simulation study on two-phase flow of the cryogenic helium gas injecting into the liquid kerosene is performed through two injection ways, including the central injection from a core and circumferential injection from three cores. The unsteady two-phase heat transfer process is modeled based on the Euler-Euler model. The numerical results are qualitatively compared and verified with the experimental observations on the ground. The phase distribution and the possibility of kerosene icing in the two injection structures during the discharge process are investigated. The results provide more insights into the experimental phenomena and also a reference for the scheme of kerosene discharge.