金属网幕通道低温两相流体选择性迁移机理与相分离特性研究

The orbital gas-liquid separation and single phase liquid acquisition of cryogenic propellants is a key unsolved technology for the modern developing aerospace engineering. In this project, aiming at a screen channel liquid acquisition device (LAD) relying on the surface tension effect, theoretical analysis, numerical simulation and experimental investigation are coherently adopted to conduct the study. The force relationships for gas and liquid phases through the complex microscopic structure, the selective migration characteristics of two phases in the channel, and the different reactions among the solid, gas and liquid are analyzed and illustrated for three aspects including the fluid penetration through the screen, the wicking performance along the screen and the flow characteristics within the LAD channel. Furthermore, the phase separation mechanism based on the surface tension and the hydrodynamics characteristics under microgravity would be clearly revealed, and a better understanding of the gas-liquid separation performance and liquid flow regularity in the complex microscale structure would be obtained. Finally, based on the well knowledge of the single phase liquid acquisition performance and the main factors, an optimization method of the LAD structure within cryogenic propellant tanks would be proposed. The work in this project would provide the theoretical and technical support for the practical application of this new technology in future aerospace engineering.

低温推进剂空间在轨气液分离与全液体获取是现代航天工程发展中亟待解决的核心关键技术。本项目针对基于流体表面张力作用的网幕通道式液体获取装置（LAD），采用理论分析、数值求解与实验研究相结合的方法，分别对流体垂直通过网幕的穿透特性、沿网幕方向的浸润特性以及LAD通道内的流动特性三个层面，分析气液相通过微尺度复杂结构通道时的受力关系，揭示气、液相在微通道内的选择性迁移行为以及气液固相间作用差异。通过研究，明确在轨环境下利用表面张力实现气液分离的工作机理与流体动力学特性，掌握微尺度复杂结构内气液分离性能和液体输运规律。获得LAD实现全液体获取的工作效果，掌握决定网幕通道式LAD液体获取性能的关键因素及其影响规律，提出低温推进剂贮箱内LAD结构的优化技术方案。为此项新技术在我国航天工程中的实际应用提供理论依据和技术支持。

低温推进剂在轨气液分离与纯液相获取是现代航天工程发展中亟待解决的关键技术。本项目针对网幕通道式取液装置所涉及到的科学问题开展了研究，内容主要包括：液体沿着网幕平面的芯吸流动过程、气体穿透润湿网幕的泡破过程、网幕通道的取液特性、装置的优化设计。结果表明，绝热芯吸与伴蒸发芯吸性能均受重力水平、网幕结构参数与布置方位、流体物性的影响，伴蒸发芯吸性能还受控于气体过热度，且对过热度非常敏感。研究发现，变径结构的孔隙的泡破压差取决于流体表面张力系数、液体与壁面材料的接触角、当地孔径、以及壁面倾角。荷兰斜纹型网幕的孔隙为特殊的三孔喉变径结构，该结构导致了网幕的“二级泡破”特性：网幕有高、低两级泡破压差，当增压前驱动压差小于临界值时，泡破阈值为较高的一级泡破压差；反之，泡破阈值为较低的二级泡破压差。一级泡破压差取决于直径较小的一级孔喉，而二级泡破压差取决于直径较大的二级孔喉。在无重力、无气泡堵塞网幕的理想工作条件下，装置的取液率受三个因素的影响：驱动压差、通道长高比、网幕选型。保持条件不变时，取液率与驱动压差、通道长高比正相关；通道长高比较大时宜选用细孔网幕，反之宜选用粗孔网幕。重力沿着通道长度方向存在分量时，取液装置的性能会受到影响：反向重力会降低取液率；正向重力会提高泡破风险，且会改变取液率。当部分网幕被气泡堵塞后，装置的取液率会降低，降低的程度只与堵塞面积有关，而与堵塞位置无关，而且驱动压差越大、通道长高比越大、网幕孔隙越粗，则取液率受影响的程度越小。研究表明，降低通道长高比、联合使用粗细网幕、将通道型线改为渐扩形，这三种优化方案可以改善装置的性能，降低装置质量的同时提高取液率。此外，本项目还额外研究了低温推进剂过冷技术、低温管路预冷问题、低温加注管路中的间歇泉问题，均取得了满意的结果。该项目为我国低温推进剂在轨管理提供了理论和技术支持。