A typical cryogenic upper stage mission requires a reliable liquid–gas phase separation prior to engine restart in space, and auxiliary engines are usually used to provide positive acceleration effect to satisfy vapor-free liquid supplement purpose. To assist thruster logic design for an upper stage, bubble distribution inside a delivery tube and bubble spilling behaviors should be known previously. In the present paper, a CFD approach is adopted to numerically study the bubble generation and bubble movement in liquid hydrogen (LH₂) delivery tube under microgravity, and the bubble spilling upward behaviors under different situations are significantly analyzed. The results show that space heat from surroundings brings about liquid evaporation inside the delivery tube, and weak convection effect induced by bubble generation process could result in random bubble distribution in the whole tube range. The maximum bubble reaches the size of tube inner diameter. Under positive acceleration effect, the bubbles spill upward and bring about gas amount decrease in the delivery tube range. Moreover, the bubble spilling upward is not a continuous process, and only the big bubble discharge exerts a significant contribution to the gas amount decrease. In addition, the tube layout and the initial gas amount have slight influence on the bubble discharge performance, but the space acceleration level plays the primary effect on this process. For the present objective, the acceleration with 10⁻³g₀ could drive the bubble to be discharged within 700 s. When the acceleration increases to 10⁻¹g₀, the required time correspondingly decreases to less than 100 s. Under the acceleration level of 10⁻⁴g₀, however, the bubble could not spill upward any more but a vapor amount increase phenomenon is observed. Generally, the present work provides an opportunity to understand the bubble properties inside the cryogenic delivery tube in microgravity, and the results on acceleration influence as well as acceleration period are beneficial to the sequence design of space engine restart.

典型的低温上级任务需要在发动机在太空重新启动之前进行可靠的液-气相分离，通常使用辅助发动机提供正加速效果以满足无汽液体补充目的。为了协助上级的推进器逻辑设计，应事先了解输送管内的气泡分布和气泡溢出行为。在本文中，采用 CFD 方法数值研究了液氢 (LH ₂) 输送管在微重力作用下，对不同情况下气泡向上溢出的行为进行了显着分析。结果表明，来自周围环境的空间热导致输送管内的液体蒸发，气泡产生过程引起的弱对流效应会导致整个管范围内的气泡随机分布。最大气泡达到管内径尺寸。在正加速作用下，气泡向上溢出，导致输送管范围内的气体量减少。而且，气泡向上溢出并不是一个连续的过程，只有大气泡的排放对气体量的减少有显着的贡献。此外，管子布局和初始气体量对气泡排放性能的影响很小，但空间加速度水平对这个过程起主要影响。对于目前的目标，加速度为 10⁻³ g ₀可以驱动气泡在700 s内排出。当加速度增加到10 ^-1 g _{0 时}，所需时间相应减少到小于100 s。然而，在10 ^-4 g ₀的加速度水平下，气泡不再向上溢出，而是观察到蒸汽量增加的现象。总的来说，目前的工作为了解微重力条件下低温输送管内气泡的特性提供了机会，加速影响和加速周期的结果有利于空间发动机重启的序列设计。