# Analysis on Influences of Squeeze Film Damper on Vibrations of Rotor System in Aeroengine
## 5 Conclusions  
In this paper, the high-pressure rotor system of an aeroengine is taken as the object. By taking the stiffness and damping of squeeze film damper, the dynamic model of the high-pressure rotor system is established. By comparing the unbalanced vibration responses before and after the introduction of SFD into the high-pressure rotor system, the following conclusions can be drawn:  
(1) After introducing SFD into the rotor system, when the unbalance of the rotor increases from 4 \(\times\) 10\({}^{-4}\) kg\(\cdot\)m to 4 \(\times\) 10\({}^{-3}\) kg\(\cdot\)m or decreases from 4 \(\times\) 10\({}^{-4}\) kg\(\cdot\)m to 4 \(\times\) 10\({}^{-5}\) kg\(\cdot\)m, the orbits all change from unstable to stable, indicating that the unbalance has a great influence on the stability of the rotor. The appropriate unbalance can effectively improve the stability of the rotor.  
(2) The rotor vibration response will appear as a bistable or unstable vibration at high speed and small unbalance. If the unbalance is properly increased, the vibration amplitude becomes larger, but the vibration response becomes a single-frequency stable vibration. The numerical simulation results also show that high and low rotational speeds and different unbalances lead to different steady-state characteristics.  
(3) The unbalanced vibration of the rotor system with squeeze film damper is special. The bounded complex vibration will appear in the case of high rotational speed and small unbalanced mass. By increasing the unbalanced mass, the unstable vibration can be converted into stable state, and the stability of rotor vibration can be improved.  
Figure 13: Vibration response under speed of \(r_{n}\) = 12,800 r/min and unbalanced mass of \(m_{e}\) = 4 \(\times\) 10\({}^{-5}\) kg\(\cdot\)m. (**a**) time domain response; (**b**) frequency domain response; (**c**) displacement.  
Through this dynamic model, the steady-state characteristics and sudden unbalance response characteristics of rotor system can be studied and analyzed quickly and accurately. Although the current unbalanced mass control is relatively strict, we need to know the influence of unbalanced mass on the vibration characteristics of the rotor system. Using the analysis method in this paper, in the design stage of the rotor system, engineers can analyze the influence of the allowable value of unbalance on the vibration and stability of the rotor, and provide a reference for the final design parameters. This article only puts forward the influence of the unbalanced mass value on rotor vibration, and provides a theoretical reference for engineering practice.  
Conceptualization, Q.H., Y.Z. and H.W.; data curation, Y.Z.; formal analysis, H.W.; funding acquisition, Q.H.; investigation, H.W.; methodology, Y.Z. and H.W.; project administration, Q.H.; resources, Q.H. and Z.L.; software, Y.Z.; supervision, H.W. and Y.Z.; validation, Y.Z.; visualization, H.W.; writing--original draft, H.W.; writing--review and editing, Y.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
This work was financially supported by the National Natural Science Foundation of China [grant No. 12072069].  
The authors declare that they have no conflict of interest.