Theoretical And Experimental Research On Axis Trajectory Of Flexible-Pivot Tilting Pad Bearings

Tilting pad journal bearing is a kind of sliding bearing,which has the characteristics of low noise,small friction consumption and smooth operation.However,this kind of bearing has caused a lot of accidents due to structural defects,so it needs to improve its structure.Flexible-pivot tilting pad journal bearing is a new form of tilting pad bearing.The bearing pads and the bearing body are connected by a flexible pivot as a whole,instead of the fulcrum.This structure not only eliminates a lot of shortcomings of ordinary tilting pad bearing,but also inherited the stable characteristics of tilting pad bearing,which has obvious advantages.Based on the flexible-pivot tilting pad journal bearing,the flexible-pivot structure,dynamic and static characteristics and active control are studied in detail,and the nonlinear axis trajectory of the rotor is obtained by using the experimental bench.The main research contents are as follows:First of all,the paper makes use of the Reynolds equation to obtain the pressure distrubution and joint force of oil film.The structural characteristics of the pads are analyzed by using the finite element method.The natural:frequency of the pad is measured by the experimental method.According to the experimental and the theoretical results,the stiffness and damping of the flexible-pivot are calculated.Secondly,the rotor motion model of the flexible-pivot tilting pad journal bearing is established based on the rotor gravity,the nonlinear oil film force and the applied load.The Euler algorithm is used to obtain the complete nonlinear axis trajectory of the rotor for a period of time.The Runge-Kutta-Fehlberg algorithm is used to derive the angle of the pads.The eight dynamic coefficients of the bearing are calculated under the premise of considering the freedom of the pad wobble.The nonlinear orbit trajectory and the dynamic characteristic calculation method are used to calculate the continuous dynamic characteristic coefficients of the system under certain working conditions.Then,this paper puts forward the active control method of installing piezoelectric brake device on the back of the bearing pads.The rotor vibration is suppressed by controlling the pads angle.The influence of the change of the angle on the axis trajectory is calculated,and the relationship between the applied force of the piezoelectric device and the angle of the pad is deduced.The calculation method of angle of the pad based on the predetermined trajectory is proposed,the swing law of the pad is calculated according to the predetermined trajectory,and the simulation is carried out.Finally,a flexible-pivot tilting pad journal bearing bench is designed.The eddy current sensor and the test instrument are used to test the nonlinear axis trajectory of the rotor at different rotational speeds.The measured data are analyzed by designing the filter.And the nonlinear axis trajectory under the actual working condition is obtained.The research of this paper has great practical significance for the practical application and active control of flexible-pivot tilting pad journal bearing.