Research On Dynamic Performances Of High-Speed Rolling Bearing And Rotor System Of Aeroengine

Rolling bearing is widely used as support in aero-engine rotor system, and its dynamic mechanical performances have important influence on the dynamic performances of the rotor system. The influence becomes more and more prominent with the enhancement of the performance of aero-engine. Therefore, in order to optimize and upgrade the existing aero-engine dynamic performance to meet the development needs of new generation aero-engine, it is necessary to study the dynamic performances of high-speed rolling bearings and rotor system. The objects of the research are high-speed rolling bearings and rotor system of aero-engine. The quasi-dynamic models of rolling bearing, dynamic property models of rolling bearing and rotor system, nonlinear vibration models of rolling bearing and rotor system are established. The influence of operating parameters and structure parameters of rolling bearing to the dynamic performances of rolling bearings and rotor system are analyzed. Computer programs are developed. High-speed rolling bearing and rotor system experiments are performed to validate the theory on an existing small high-speed rolling bearing bench. The research provides theoretical foundation for analysis of high-speed rolling bearings and rotor system, and also provides technical reserves for the reliability of aero-engine.The dynamic performances of high-speed rolling bearing are investigated. Through the analysis of high-speed ball bearing and roller bearing using the quasi-dynamic models, it is found that the operating parameters and structure parameters of rolling bearing have evident influence on the performances of the bearing. For the ball bearing with radial load and bending moment, spin to roll ratio, PV value of balls and sliding ratio of cage are changed greatly in value and rule when compared to axial loaded or radial loaded bearing, and the influences of bending moment are more evident. PV value of balls and sliding ratio of cage are decreased evidently by small contact angle or large groove curvature. For the roller bearing with bending moment, peak of contact load and PV value become large. Bending moments have significant influence on the dynamic performances of high-speed light-loaded roller bearing. PV value of rollers and sliding ratio of cage are decreased evidently by non-circular ring or small radial clearance. The influence rules of the axial pre-load to the skid of ball bearing are studied. The definition of the critical axial load to prevent skid of ball bearing is given. For the ball bearing with axial load and radial load or bending moment, the axial load is the critical axial load when there aren't skidding in loaded balls and rotational speed of cage becomes stable. For the axial loaded ball bearing, the axial load is the critical axial load when loaded balls don't skid. The axial load of ball bearing also can be provided when skid ratio of cage is given.The dynamic characteristics of the rotor system are analyzed considering dynamic stiffness of bearing using Riccati transfer matrix method. Compared to certain stiffness computation method, it is found that there are great influences on critical speed, stability, instability threshold of rotor system when dynamic stiffness of bearing are considered. For instantaneous response of rotor system can influence dynamic performances of rolling bearing, the whole computation model of bearing rotor system is established. The couple rules of rotor response and dynamic property of bearing are analyzed using Newmark-βmethod, it is found that amplitude of the rotor and cage sliding rate will becomes great larger when change ratio of load or sudden unbalance force is large.In order to reveal the complex vibration behavior of rotor system supported by rolling bearing, a nonlinear vibration analysis model is established and solved by Runge-Kutta method. The results show that the nonlinear variable stiffness vibration will be induced by nonlinear bearing force, which resulting in periodic vibration and quasi-periodic, chaos vibration in the system. Select appropriate parameters, such as, contact angle, clearance, preload of bearing and damping, etc., can improve the nonlinear vibration behavior caused by nonlinear bearing force. When unbalance force exist in the rotor system, non-periodic vibration regions will increase and combined vibration constitute of variable stiffness vibration frequency and unbalance vibration frequency will occur. The relationship between vibration frequency caused by outer waviness, inner waviness, rolling element waviness of bearing and bearing structure parameters, waviness orders is given. Considering nonlinear vibration of rotor system, it is found that skid ratio and stiffness of bearing are changed greatly.A design and analysis software for rolling bearing has been developed using software integration technology. The software integrates parametric design of bearing, performance prediction of bearing rotor system, temperature field analysis and life prediction of bearing, which provide method for design and analysis of rolling bearing.The quasi-dynamic model of rolling bearing is validated by dynamic example which has been validated by test. The results in this dissertation are very close to the example and the difference is less than 5%, which shows that the model and method put forward in the dissertation to forecast the bearing characteristics is precise.At last, dynamic characteristics test researches of high-speed rolling bearing rotor system have been finished using the rolling bearing bench test. Critical speed, vibration displacement, axis orbit are obtained. The theoretical results in this dissertation are very close to test data and disclose the complex axis orbit of the rotor system, which shows that the model and method put forward in the dissertation to forecast dynamic property of rolling bearing rotor system is precise and credible.