# Study on dynamics of rotor system

The nonlinear dynamic characteristics of rotor system have also been studied in China. In 2002, Li Songtao, et al. Studied the dynamic stability of rotor system under the action of seal, and studied Jeffcott of single disc The nonlinear dynamic characteristics of the rotor are calculated. It is found that under the influence of the sealing force, the rotor will start to lose stability after reaching a certain speed, and bifurcation will occur. When the rotating speed of the rotor continues to increase, due to the increase of vibration amplitude, it will eventually develop into a shaft rubbing fault In 1996, Xiao Zhonghui studied the dynamic characteristics of complex rotor system. He proposed a practical and perfect dynamic characteristics analysis model of rotor bearing seal coupling system. This model considered the influence of sliding bearing and gas seal on the system, and used several solving methods to solve the nonlinear dynamic characteristics of complex rotor system. By comparing the stability of rotor system with or without sealing force, it is pointed out that the influence of seal on dynamic stability of rotor system can not be ignored, and it is pointed out that seal exciting force is an important factor leading to rotor system instability.

In 2009, Liu Yanming and others carried out theoretical analysis on the nonlinear dynamic characteristics of the rotor bearing seal coupling system based on the sealing force model. The results show that the dynamic behavior of the coupling system presents complex phenomena due to the change of rotor speed; 2013 Zhang Hai studied the interaction between turbomachinery and rotors in, and his research showed that the vibration characteristics of rotors and the interaction between rotors and seals would have adverse effects on the operation of rotors.

In 2018, Li Shengyuan carried out theoretical and Numerical Research on the dynamic characteristics of sliding bearing and seal fluid of rotating machinery, established the theoretical solution model of dynamic characteristics of sliding bearing and seal fluid, and analyzed the influence of dynamic characteristics of sliding bearing and seal on the stability of rotor system by using the method of work done by fluid exciting force. In recent years, there are many literatures about nonlinear rotor dynamics, which are not listed here.

The above studies show that the research of rotor dynamic characteristics has its own emphasis, and the research depth is also different. With the development of rotor dynamics, more and more factors should be considered in the dynamic analysis of high-performance rotating machinery. In addition to the structure of the rotor and the role of bearings, the influence of transmission device and seals should also be considered in the research of rotor dynamics.

In conclusion, although the research on planetary gear transmission system and rotor system started earlier in foreign countries, and domestic research in recent years is also fruitful, there are still deficiencies in considering the system influencing factors and degree of freedom, and the research depth is also different. Therefore, in this paper, when studying the dynamic characteristics of the sealed rotor system considering gear meshing characteristics, combined with planetary gear transmission system and rotor system, considering various factors, according to the actual situation, a multi degree of freedom system dynamic model is established to study the dynamic characteristics of the rotor system under the influence of transmission device and sealing components.

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