Dynamics Stability Analysis And Experimental Verification Of High Speed Journal Bearing-Rotor System

With the development of the industry, the increasing of load and the speed of the rotating machinery, constantly improve the performance and rolling bearing performance could not meet the design requirements, the journal bearing by its strong carrying capacity is strong and able to withstand the impact to make the first selection of designers. But when the machine is running at high speed, the motion of journal bearing oil film may result in rotor system vibration. Slight vibration can produce noise, reduce the working efficiency of the machine; severe vibration can make the parts fault, cause an accident. Therefore, high speed journal bearing, dynamic stability analysis of rotor system and how to optimize, monitoring the journal bearing, the dynamic stability of the rotor system becomes an important topic of the design and manufacture of high-speed rotating machinery.In this paper, based on high speed gear box as the research object, first of all, static and dynamic characteristics analysis of the journal bearing, and then according to the principle of dynamic rotor, the high-speed journal bearing- rotor system’s dynamic stability is analyzed, and calculate the critical speed of the rotor system. Finally, through the dynamic simulation of the gear box and vibration test, verify the dynamic stability of the journal bearing- rotor system and the overall dynamic performance of gear box.The main research contents are as follows:(1) Based on the relevant theory of engineering fluid mechanics, analysis of dynamic and static characteristics of journal bearing, and according to the boundary conditions of dynamic pressure oil film, calculate the force of dynamic oil film and the stiffness matrix and damping matrix of journal bearing;(2) Sliding bearing dynamic pressure oil film force is the main reason for instability of the high speed journal bearing-rotor system, so it’s necessary to analysis the instability of the rotor system caused by dynamic pressure oil film;(3) Based on the lumped mass method, to simplify the high-speed sliding bearing rotor system for a multi disc rotor system, and according to the related theory of rotor dynamics, considering the stiffness of the bearing, sliding bearing dynamic pressure oil film stiffness matrix and the influence of the gyroscopic effect, it is concluded that the stiffness matrix and mass matrix of the rotor system, establish the motion differential equations of rotor system;(4) For the high speed journal bearing-rotor system, gyroscopic effect on the system had a greater influence on the critical speed. Comprehensively considering the influence of gyroscopic effect and journal bearing stiffness, the critical speed of the rotor system is solved, and analyze the critical speed’s sensitivity of the system’s structural parameters;(5) According to the comprehensive modal synthesis method, analysing this type high speed gear box by dynamic software, through the virtual sensor monitoring the vibration of the high-speed shaft. Finally through vibration testing device, vibration test was carried out on the reduction gear box, verify the high speed rotor dynamic stability and accuracy of the dynamic characteristics of the whole system.