Simulation And Experimental Study Of Magnetofluid Capillary Flow Under Magnetic Compensation Microgravity

China's space industry is entering a new stage-the earth orbiting space station,lunar exploration,and Mars exploration.Microgravity environment is an important factor in the storage and management of new spacecraft cryogenic propellants and basic hydrodynamics research of space station.Under the condition of microgravity,due to the dominant of surface tension,the shape of the liquid-gas interface and the interaction with the solid wall are different from the experimental law under the constant gravity.Therefore,for the technology of in-orbit storage and management of cryogenic propellants under microgravity conditions,the gas-liquid interface of the propellant in the tank and the climbing process along the tank wall and the liquid acquisition device(LAD)are likely to show many special rules,which have a significant impact on the in-orbit propellant management.The study of capillary flow of fluid under microgravity is of fundamental value for the development of space technology in the new stage.The primary condition for conducting experimental studies on microgravity characteristics of propellants is to obtain a microgravity environment with long duration,high stability,low cost,easy visual observation and measurement,and permissible intervention operation.In the past,the experimental research on the thermal state of fluid in microgravity environment was basically realized by dropping tower,parabola flight,sounding rocket,space shuttle and international space station.The first two experimental approaches can only provide short duration microgravity environment(in the order of several seconds to tens of seconds)and the existing conditions are usually unable to carry low-temperature equipment and maintain low-temperature environment,which cannot meet the requirements of low-temperature thermal experiment;the second three experimental approaches are expensive to achieve,and the task queuing cycle is long,which cannot obtain sufficient experimental data.At the same time,no matter the traditional ground microgravity test conditions or the current space in-orbit microgravity test conditions,it is difficult to conduct microgravity environmental experiments on cryogenic fluids such as liquid hydrogen and liquid oxygen.Therefore,it is necessary to develop a new method for simulating microgravity environment.This new microgravity test method should have these important characteristics: low cost,longtime maintenance,and be applicable to liquid hydrogen,liquid oxygen and other cryogenic fluids.Using magnetic field to compensate gravity field is a competitive technique.This paper will introduce the design,construction and experiment of magnetic fluid compensation microgravity environment system.And then numerical simulation of capillary flow in microgravity environment and the realization scheme of superconducting magnetic field microgravity environment for liquid oxygen and the discussion on the consistency between earth and sky of magnetic compensation microgravity experiment are also discussed.The details are as follows:First,the magnetic characteristics of ferromagnetic fluid are used to obtain a homogeneous microgravity environment similar to space orbit by applying an external magnetic field to counteract the gravity of each particle of the liquid.The scheme uses a combination of Maxwell coil and Helmholtz coil to generate a uniform gradient magnetic field in its central region,thus providing a uniform magnetic force which opposite to the direction of gravity for the magnetic fluid located at the design point.The scheme has the advantages of easy implementation,low cost,repeatability,adjustable gravity level and long experiment duration.On the basis of detailed magnetic field scheme design and simulation calculation,a magnetic compensation microgravity experiment system is built,which can realize the microgravity environment with uniformity better than 95% in the area of ? 40 mm × 80 mm,and basically meet the needs of preliminary microgravity experiment.Then,a series of tests were carried out on the above microgravity experimental table for two common storage and diversion units(screen and floor)in space propellant management technology,and the storage capacity of screen and floor under different gravity levels was investigated.It is found that a relatively small mesh number within the measured range can obtain a strong flow storage capacity.For the floor,under the condition of internal flow,the smaller the internal Angle or the smaller the fluid contact Angle,the stronger the flow storage capacity of the floor.At the same time,numerical simulation and partial differential equation analysis were used to analyze and simulate the flow process of internal capillary flow in microgravity environment,and the effects of different internal angles and different contact angles on internal capillary flow were studied.Finally,a microgravity experimental system of superconducting magnet for low temperature propellant oxidizer liquid oxygen is proposed.We designed a magnetic field structure to realize homogeneity magnetic compensation and then We propose a magnetic field scheme to simulate microgravity environment and variable acceleration environment.Theoretically,the inhomogeneity of magnetic compensation force less than 1% in the ? 100mm×195mm cylinder area can be realized.The feasibility of superconducting magnetic compensation microgravity and the consistency between space and ground are analyzed.It is found that when the inhomogeneity of simulated magnetic field force is less than 0.1%,the ground magnetic compensation liquid oxygen microgravity experiment can achieve a better consistency between space and ground.This study will provide a preliminary reference and empirical basis for the ground microgravity simulation experiment of cryogenic propellant in the future.