Simulation Of Thermal Protection Effect Of Metal Diaphragm Tank Coating Based On Multi Field Coupling Analysis

The space propellant tank upper cavity was filled with the exhaust gas with high temperature and high pressure,then the diaphragm could be reversed deformation and extrude out low temperature propellant.It is very important to reduce the heat insulating and heat exchanging between the gas and propellant,one of the most effective way is spraing some thermal protection material on the inner wall of the upper cavity,the temperature increasing of propellant can be control within an allowable range.Obviously,thicker heat shields means better heat protection for low temperature propellant.However,thicker heat shields will affect the ability of turnover of diaphragm and increase the dead weight of the tank.In order to determine the reasonable thickness of heat shield,coupling analysis method of multi-physics field with structure,fluid and thermal was applied and finished by using MSC.MARC and ANSYS FLUENT.Firstly,a full tank model including metal diaphragm,inlet of gas,outlet of propellant,tank shell,heat shields,gas and propellant was established.According to the propellant liquid discharge curve,the curve for relationship between overturn data and load increment steps of diaphragm with heat shields was obtained and transferred into the curve for relationship between the displacement of heat shield,diaphragm and time.Secondly,the diaphragm was forced to deform under the high pressure of gas while the tank working in the space.It is a very complicated problem coupling with large nonlinear structure deformation,fluid flow and thermal exchange.It is almost impossible to solve the fluid structure coupling problem directly.In this paper,a solution is proposed to solve the problem of multi field coupling of tank: Based on the first step,the motion of the diaphragm was treated as known parameters,then thus complicated coupling problem could be transfer into a simple coupling problem.That is,diaphragm moved first,then the gas was pumped into the upper cavity from the inlet,meanwhile the propellant was extruded from the outlet.The motion of the diaphragm was calculated with a UDF in the simulation.Thirdly,the multi-field physics coupling problem of a certain space propellant tank was numerically calculated.The temperature distribution of the tank was gained and the temperature changes along the complete working process of the tank was obtained.The temperature increasing of propellant with different thickness of heat shields in the whole process was evaluated.And a reasonable thickness of heat shields was found for such space propellant tank.Fourthly,the typical thermal protection layer thickness was selected to study its thermal protection effect,meanwhile consider its temperature rise curve.The thickness of heat shield and the effect of heat protection are discussed.Finally,a multidisciplinary analysis software for tank are designed and developed.Users only need to input the metal diaphragm,tank shell and heatshields geometric parameters,gas,tank shell,propellant and thermal protection layer and the metal diaphragm material parameters,import the real discharge curve,automatic analysis the whole tank discharge process.As result,gain the temperature rise curves of propellant with time.