运载火箭圆柱形贮箱中推进剂大幅晃动的数值模拟

Numerical Simulation of Large Sloshing of Propellant in Cylinder Tank of Launch Vehicle

关键词:  液体火箭发动机  贮箱  晃动  波面破碎  非线性  含液率

Key words:  Liquid rocket engine  Tank  Sloshing  Wave surface breaking  Nonlinear  Liquid rate

摘要:

运载火箭飞行过程中，贮箱内推进剂晃动及波面破碎现象会对燃料贮箱产生较大的干扰力，控制不当会影响飞行稳定性。为了研究推进剂大幅晃动对贮箱结构的影响，建立了圆柱形贮箱内液体晃动非线性动力学模型，利用流体体积函数与水平集法解决了大幅晃动过程中产生的破碎波的描述及自由液面的追踪问题，并对三维圆柱形贮箱在多种含液状态下，由俯仰运动产生的大幅晃动进行了数值计算，得到了晃动过程中自由液面的变化、液体对壁面的作用力、液体的晃动速度以及液体质心变化情况。通过对含液率为30%，50%，70%三种含液状态下计算结果的对比，发现飞行中运载火箭贮箱中液体会经历由线性晃动到非线性晃动的变化历程。含液率直接影响晃动的剧烈程度、对壁面的作用力，以及液面破碎等非线性现象的产生，其中含液率为50%的状态是一种相对危险的工作状态。

Abstract:

During the flight of the launch vehicle， the propellant sloshing and wave surface breaking in the fuel tank impose a large disturbance force to the fuel tank. The disturbance will affect the flight stability if it is not effectively controlled. To study the effects of propellant sloshing on the tank structure， a nonlinear dynamic model of liquid sloshing in a cylinder tank is established. The proposed model combining Fluid Volume Method and Level Set Method is used to describe the breaking wave. Besides， the numerical calculation is carried out for analyzing the large sloshing of a 3D cylinder tank under various liquid rates. Then the changes of the free surface area， the force of the liquid on the wall， the sloshing velocity of the liquid and the center of liquid mass are obtained. Through the comparison of the calculation results under three liquid rates of 30%， 50% and 70%， it is found that the liquid in the launch vehicle tank changes from linear sloshing to nonlinear sloshing during the flight. Moreover， the liquid rate directly affects the sloshing intensity， the force on the wall， and the occurrence of nonlinear phenomena such as liquid wave breaking. The liquid rate of 50% is a relatively dangerous working condition.