Analysis And Research On Nonmetal Anti-sloshing Baffle And Its Effect On Liquid Sloshing Suppression

The sloshing of liquid in the container is a common phenomenon in the application of actual project, such as oil tank truck, aircraft fuel tank, tanker, rocket, missile, and so on. And this is a complex phenomenon with a high degree of nonlinearity and randomness. It is also a periodic motion, if the sloshing frequency of the liquid is close to the natural frequency of the tank structure, the resonance phenomenon will happen, which could cause a damage of the tank structural. Thus, during the design of the structure of the liquid containers, the dynamic response of the structure induced by the sloshing of the liquid should be considered.The analysis of the sloshing of liquid is a very important research topic in the aerospace, even a slight oscillation of the propellant could induce a migration of its center of mass, which will affect the dynamic performance of the entire structure. So the sloshing of the liquid must be suppressed to ensure the safety and reliability of the rocket. One of the most measures is installing baffles in the tank, and most of them are made of metal. However, the nonmetal baffle can reduce the weight of the anti-sloshing structure; it hasn’t obtained wide range of application. The related research is not so much, and the requirement of the surrounding environment of liquid oxygen is the severest, so the selection of the material for the baffle in the LOX tank and the effect of the baffle on suppressing the sloshing of the liquid are conducted in this paper.First, the mechanism of LOX compatibility and the selection principles of the materials were introduced. And the LOX compatibility tests for different materials were conducted. It was found that F46and PTFE were compatible with LOX, and that further study should be conducted to define the compatibility of PI. Mechanical analysis of circular baffle was carried out, and according to the safety factor, the equation for calculating the thickness of the baffle was given.Second, the problem of fluid-structure interaction was described, and based on the finite element software, the mode analysis of part-filled LOX tank was conducted; also the antisymmetric modes were chosen to compare with the theoretical value. The effect of the baffle on the mode of the liquid in the tank was analyzed; the comparison of it with the mode without baffles was made. It was found that the sloshing frequency for the tank with baffle was a little lower than the case of without baffle. Last, the energy dissipation rate of the viscous liquid was analyzed from theoretical aspects to explain the essence of the decay of the energy, and the equation for calculating the damping factor produced by baffles was deduced. The dynamic analysis of the FSI system was conducted based on the software ADINA to study the dynamic response of the liquid in the tank. The comparisons of the different conditions--with baffle and without baffle, the different depth of baffle, different layers of baffle were carried out, and found that the damping factor of nonmetal baffle was no less than the factor of metal baffle. The nonmetal baffle could not only suppress the sloshing of the liquid, but also reduce the weight of the anti-sloshing structure.