Finite-Element Modeling and Frequency-Domain Analysis of Liquid-Propulsion Launch Vehicle

In the flight process of liquid-propulsion launch vehicles, coupling effect exists among vibration of rocket system, pressure, and flux oscillation of propulsion system and thrust perturbation. This effect may lead to instability or large vibration response. Aiming at this problem, a virtual mass model based on three-dimensional potential flow theory is used to characterize the interaction between propellant and tank wall, reflecting the flow characteristics of propellant more accurately. Also axial symmetry is used to decrease the degree of freedom of the structure system. For each component of propulsion system, the time-domain relationship between pressure and flux is deduced. At last, governing equations of a propulsion-structure coupled system in the form of second-order system of ordinary differential equations are established. On this basis, characteristic properties and sensitivity of the coupled system can be calculated easily, making easy the optimal design of the system.