Nonlinear Dynamic Analysis Of Bearing-Rotor-Box System Under Multiple Fault Coupling

The rotor system is a major component of large rotating machinery which is similar to aero engines.Because it usually works in a harsh working environment,it is inevitable that a variety of faults will occur.In this dissertation,single-span and double-span rolling bearingrotor systems under multiple faults are taken as the research object.Faults such as rubbing,cracks,and loosening,airflow vibration forces,and bolt flange structural factors are comprehensively considered,and the failure mechanism of some system parameters is combined.The simulation research is done.The research in this paper is mainly divided into the following aspects:Comprehensive consideration of rubbing fault,crack fault,loosening fault.Based on the research of scholars at home and abroad,the three faults coupled to do the research.The single fault and then the influence of the coupling fault on the system stability are analyzed.The research shows that: the rubbing fault can increase the first-order critical speed of the system,and the acquisition signal exhibits a higher continuous spectral component;the crack failure can reduce the first-order critical speed,and the acquired signal exhibits a higher fractional frequency component;Without changing the first-order critical speed,the acquired signal shows a higher third-frequency component.Considering the effects of airflow excitation forces generated by the blades on the rotor.The traditional Alford airflow excitation force was improved,and the formulas of straight and twisted blade airflow excitation forces derived agreed well with actual conditions.The different combinations of the two rotor blades were explored.Research shows that when the two rotor blades are of the same shape,the movement is relatively stable.With the increasing of the intake air speed and blade height,the stability of the "double-straight" blades changes significantly in the super-first-order critical speed range,and the stability of the "doubletwisted" blades changes in the range of lower-first-speed and super-second-speed speeds.Obviously,the stability of the "straightened" blade changes significantly over the entire speed range.With the changing of the inlet and outlet angles,it is significant that the difference between the outlet angle and the inlet angle has a effect on the stability of the system for "double-straight" blades.The difference in intake angle has a significant effect on system stability.Consider bolted flange connection structures.The structural equation of single-span boltflange connection is established,and the influence of some system parameters on system stability is analyzed.The results show that: as the speed increasing,a large amount of chaos appears in the super-second-order speed;under the premise of considering the air flow excitation force,the twisted blade can make the rotor move more stable in the high speed region;The amount of deformation increases,the second-order speed of the system increases,and the movement is more stable in the range below the first-order speed;As the bearing clearance increases,the second-order critical speed of the system decreases.As the eccentricity of the rotor increases,the second-order speed of the system increases,and the chaotic range in the super-second-order speed range becomes larger.