Sloshing Analysis And Anti-Sloshing Structure Design Optimization Of A Rocket Tank

The propellant sloshing of the Rocket Tank refers to the movement change of the free surface of the propellant caused by the external disturbance or excitation.The sloshing of the propellant has two main effects.One is that the frequency center of gravity of the rocket body changed by the sloshing of the propellant,which affects the control system of the attitude and orbit of the rocket.The other is that the sloshing load caused by the large and violent sloshing of the propellant will affect the internal structure,resulting in strength and fatigue problems.Due to the large volume and mass of the propellant,the sloshing load of the heavy launch vehicle increases a lot.For the anti-sloshing structure inside the tank,compared with the small tank,its radial width also increases several times.Under the impact load,it is difficult to meet the strength and stability of the anti-sloshing structure.Therefore,it is necessary to analyze the sloshing of the propellant of the heavy launch vehicle,at the same time,the new design and optimization of anti-sloshing structure are carried out.Firstly,smooth particle hydrodynamics(SPH)is used to simulate the sloshing of propellant,and Ls-Dyna is used to establish the sloshing dynamic model.During the sloshing process,the influence of structural deformation is not considered.Both the tank and the anti-sloshing plate are treated as rigid body,and the liquid level change of the pushing agent is analyzed.The maximum impact dynamic load is obtained by extracting the load time history curve on the anti-sloshing plate,after that,the uniform treatment is simplified to static analysis load.Secondly,based on the sloshing load obtained,three different anti sloshing supporting schemes are designed,i.e.support plate,brace and longitudinal plate.Through the establishment of finite element model,the support characteristics of different schemes are analyzed.Finally,with the strength and rigidity as the constraints,according to the principle of the lightest weight,the best anti-sloshing supporting structure is obtained by comparison.Then,based on the preliminary design,in order to reduce the total weight of the structure,taking the strength and stiffness as the constraints,the size and topology of the triangle support plate are optimized.At the same time,the aluminum honeycomb structure is used to optimize the structure of the anti-sloshing plate,which improves the bending stiffness of the structure.Finally,considering the connection details of the structure,the sub model method is used to cut out the local structure from the overall structure for the connection details analysis,the fastener element is used to simulate the bolt connection,and the number of bolts meeting the connection strength is obtained by extracting the bolt load.At the same time,in view of the uneven stress of the bolts connecting the tank and the support plate,according to the stress characteristics,keep the end bolts unchanged,gradually reduce the number of intermediate bolts,analyze the minimum number of bolts,and further reduce the structure weight.