Investigation On The Forced-flow Stability In Asymmetry Channels Under Microgravity Condition

The development and application of the on-orbit refueling technology plays a significant role not only in largely enhancing the flexibility and extending the lifetime of spacecrafts but also in making them be more capable of doing various tasks. Space liquid management is one of the important technologies in realizing the on-orbit refueling of the spacecrafts. In microgravity, liquid transportation dominated by surface tension force performs much differently from that in the ground condition. Good knowledge of characteristics of liquid flow in microgravity condition is critical to smooth advancement of on-orbit propellant transportation. During propellant venting, to prevent gas from entering the liquid inside the tank, there exists the flow rate limitation of peak value. Once exceed the critical flow rate, the capillary pressure can no longer offset the pressure difference between liquid and gas on the surface. In that case, surface collapses and gas enters the propellant, leading to a failure in propellant refueling. This is the so-called forced flow stability problem in propellant venting. As a kind of widely used propellant management devices(PMDs), the asymmetryical interior corner capillary channels play an important role in satellite surface tension tanks. Despite this, so far, there are few literatures that focus on the flow stability in the asymmetry channels.Setting in this technology, the paper is concerned with the stability and collapse behavior of liquid free surface dominated by the surface tension force in the flow in the asymmetrical interior corners. In this paper, the one-dimensional governing equation system is established, based on which the optimization has been conducted to achieve better propellant management for vanes. Moreover, we have designed the microgravity experiment of drop tower to verify the theoretical model. Work in this paper includes:(1) Establish the theoretical model for the flow stability in the asymmetrical interior corner. By introducing an equivalent interior corner, the asymmetrical corner is converted to an equivalent symmetrical one, both of which share the same surface, overcoming difficulty of modeling brought about by geometrical complexity of asymmetrical interior corner. In this part, we analyze the mechanics of liquid flow driven by surface tension force in microgravity. Derived from the momentum equation, the mass conservation equation and the Young-Laplace equation, the one-dimensional theoretical model is developed. Through numerical solutions to the equation system, surface parameters and the critical flow rate can be determined. By applying Fluent simulation software, numerical simulation verification is conducted to verify the theoretical model.(2) Characteristic analysis of the capillary flow stability in asymmetrical interior corners. The influence of geometrical factors of the vanes like width, length, and radius of the tank on the flow stability is explored based on the forced flow model of unsymmetrical interior corners. The influence of the propellant viscosity on flow stability is also analyzed, which shows that, different viscosity causes different surface parameters and different locations that go unsteady.(3) Optimization of vanes to improve the flow stability. Based on the analysis of the one-dimensional capillary flow model and its characteristics, optimization is conducted to maximize the critical flow rate during propellant venting process. The width, length and number of the vanes as well as the tank radius are chosen as the designed variables. Tanks with single outer vanes, single inner vanes, and with both inner and outer vanes are considered. This work can be served as a reference for practicing design and optimization in tank engineering.(4) Experiment design for the drop tower. We have designed the experiment device system and the experiment scheme for the microgravity drop tower equipment based on current experiment conditions provided by Chinese Academy of Sciences. This work aims to validate the theoretical model by experiment means. Despite the delayed conduction of the experiment due to problems in device manufacturing, this work has laid solid foundation for the upcoming microgravity experiments.The paper investigates the flow stability during propellant venting in the satellite surface tension tank on theoretical, numerical and experimental front. The work in the paper enriches the interior corner flow theory, provides valuable reference to propellant management device designers, which enjoys great significance both for theoretical study and engineering practice.