Minai O. M. "The dependence of the design parameters of capillary means of ensuring the integrity of the fuel on the term of their operation" – Qualification scientific work on the rights of the manuscript.
Dissertation for the degree of Doctor of Philosophy in specialty 134 – Aviation and rocket-space engineering in the field of knowledge 13 – Mechanical engineering – Yuzhnoye State Design Office, Dnipro, 2024.
The flight of space aircraft with a long service life and multiple activation of the propulsion system: space stations, space tugs, telecommunication satellites, space telescopes, research probes, etc., is characterized by alternating active sections of the trajectory, when the propulsion system is operating, and passive sections, on which liquid components fuel in the tanks are under the influence of weightlessness (microgravity) and due to various disturbing factors can occupy any position in them. To ensure the normal functioning of the propulsion system, in particular, in microgravity conditions, special means of ensuring the integrity of the fuel are installed at the entrance to the flow line. At the same time, a situation is not excluded when the gas phase will get to the means of ensuring the integrity of the fuel, and from there to the consumption line, which may subsequently lead to a failure of the re-start of the propulsion system and an emergency termination of the mission.
In this case, the condition for ensuring the integrity of the fuel components at the entrance to the engine is to prevent the gas phase from entering the volume of the fuel component, which is located in the area of the means for ensuring the integrity of the fuel, and directly in it, during the start-up and subsequent operation of the engine.
One of the systems that effectively ensure the supply of the fuel component to the entrance to the propulsion system without the presence of a gas phase in it, and the possibility of its multiple launch in conditions of weightlessness (microgravity), are capillary means of ensuring the integrity of the fuel.
The main functional element of such systems is a capillary phase separator, the functioning of which is based on the use of the surface tension of the liquid. The existence of a capillary pressure drop when passing through the surface of the phase distribution ensures that the fuel is kept in a certain place in the tank.
Most often, the role of the main or auxiliary capillary phase separator in various types of capillary intake devices is performed by metal woven meshes with micron-sized cells, which in this case are called mesh phase separators.
The main design parameter of the mesh phase separator is the capillary retention capacity. It is responsible for the maximum static pressure drop, at which gas phase does not penetrate through the grid cells. When designing, they try to maximize the capillary retention capacity, but in such a way that the hydraulic pressure losses during the flow of the fuel component through the mesh phase separator, on the contrary, are minimal.
In spacecraft with a long service life under the influence of aggressive fuels in the fuel tanks, for example: nitrogen tetroxide and unsymmetrical dimethylhydrazine, the capillary retention capacity of mesh phase separators can change. The reasons for this are a decrease in the diameters of the mesh wires, the formation of films, gels, and precipitates on the surface of the wire due to corrosion processes. This leads to the fact that with long-term exposure of aggressive fuels and their vapors to the construction materials of the grids, there is a change in the geometric dimensions of the wire and cells of the grid, as well as a possible change in the contact angle of fuel wetting with the grid material. Together, all this can contribute to a critical decrease in capillary retention capacity.
The pores of fine meshes have a very complex shape, which makes it impossible to determine the capillary retention capacity of mesh phase separators by calculation. A promising direction in improving the perfection, efficiency, and reliability of the operation of the structures of capillary means of ensuring the integrity of the fuel is to determine the effect of long-term storage of mesh phase separators in components and under vapors of liquid rocket fuels: nitrogen tetroxide and asymmetric dimethylhydrazine on the change of their main design parameter - the capillary retention capacity by her experimental research.
Thus, establishing the patterns of changes in the design parameters of mesh phase separators depending on the duration of action of liquid rocket fuel components: nitrogen tetroxide and unsymmetrical dimethylhydrazine on their structural materials and creating a methodology for their calculation and design is an urgent and timely scientific task.
