Analysis of liquid sloshing under variable thrust, variable filling liquid ratio, and tilted tank state
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摘要:
随着航天技术的发展，新型深空探测器在起飞时会遇到2种特殊工况：发动机推力矢量的大小和方向随时间变化；发射初期，重力方向和航天器主轴线不重合。同时，飞行过程中，液体燃料不断消耗。面对上述3种工况，针对航天器贮箱内液体晃动问题，提出解决方案：在动力学建模阶段，考虑航天器平动加速度的影响，分析推力不沿航天器轴线方向的液体晃动情况；借助变等效力学模型参数方法，计算变充液比工况下的液体晃动问题；通过设定等效力学模型中单摆存在一个初始摆角，模拟贮箱倾斜时液面与贮箱轴线不垂直的状态。以Cassini贮箱为例，在半充液状态，分别计算上述3种工况下的晃动力和晃动力矩。以某型号航天器液体贮箱为例，在实际发射条件下进行晃动分析，计算结果与商用软件Flow-3D计算结果吻合较好，验证了所提计算方法的可行性。
Abstract:With the development of aerospace technology, new deep space probes will encounter two special operating conditions during takeoff: the magnitude and direction of the engine thrust vector changing over time; the direction of gravity during the initial launch does not coincide with the main axis of the spacecraft. During the flight, liquid fuel will be continuously consumed. This article suggests a new solution for the problem of liquid sloshing in spacecraft storage tanks to the aforementioned three working conditions: taking into account the impact of spacecraft translational acceleration during the dynamic modeling stage and then analyzing the sloshing situation of thrust not along the spacecraft axis direction; calculating the liquid sloshing problem under variable charge to liquid ratio conditions using the method of variable equivalent mechanical model parameters; and simulating the situation where the liquid level is not perpendicular to the tank axis when the tank tilts by setting an initial swing angle for a single pendulum in the equivalent mechanics model. This article takes the Cassini storage tank as an example to calculate the sloshing force and moment under the three working conditions mentioned above in a semi filled state. Finally, taking a certain type of spacecraft liquid storage tank as an example, sloshing analysis is carried out under actual launch conditions. The practicality of the calculation approach presented in this article is confirmed by the calculation results, which are in good agreement with the results of calculations made using commercial software Flow-3D.
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图 1 充液航天器三维运动等效系统
Figure 1. Three-dimensional motion equivalent system for liquid filled spacecraft
图 3 变充液比工况晃动计算流程
Figure 3. Flowchart for sloshing calculating under the variable filling liquid ratio operating condition
图 6 变推力工况下液体对贮箱的作用力在本体坐标系下的分量
Figure 6. The component of the force exerted by a liquid on a storage tank under variable thrust conditions in the body coordinate system
图 7 变推力工况下液体对贮箱的作用力矩在本体坐标系下的分量
Figure 7. The component of the torque exerted by a liquid on a storage tank under variable thrust conditions in the body coordinate system
图 9 变充液比时液体对贮箱的作用力在本体坐标系下的分量
Figure 9. The component of the force of liquid on the storage tank under the condition of variable filling ratio in the body coordinate system
图 10 变充液比时液体对贮箱的作用力矩在本体坐标系下的分量
Figure 10. The component of the torque of liquid on the storage tank under the condition of variable filling ratio in the body coordinate system
图 11 贮箱倾斜姿态下液体CAD模型
Figure 11. CAD model of liquid under tilted posture of storage tank
图 12 贮箱倾斜时液体对贮箱的作用力在本体坐标系下的分量
Figure 12. The component of the force exerted by the liquid on the storage tank when the storage tank is tilted in the body coordinate system
图 13 贮箱倾斜时液体对贮箱的作用力矩在本体坐标系下的分量
Figure 13. The component of the torque exerted by the liquid on the storage tank when the storage tank is tilted in the body coordinate system
图 14 液体对贮箱的作用力在本体坐标系下的分量
Figure 14. The component of the force of liquid on the storage tank in the body coordinate system
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