Analysis Of The Oil Whirl Fault Based On Nonlinear Frequency Modulation Component Decomposition

Rotating machinery plays an important role in modern industry,and it is the key equipment of large ships,aerospace,electric power and machinery.As an important component of the large rotating machinery,sliding bearing is widely used because it can effectively improve the stability of the rotor system and has the advantages of simple structure and strong bearing capacity.Bearing failure will directly affect the performance of the whole machine,so it is of great significance to analyze and study the fault signal of the sliding bearing to ensure the normal operation of the equipment and reduce the economic loss caused by the failure.However,due to the existence of variable speed,unstable load,defect,fault and other reasons,the vibration signal of the rotor often represents non-stationary characteristics and is companied with the secondary harmonic and high frequency component.Traditional time domain analysis and frequency domain analysis can't accurately describe the characteristics of the signal and can't analyze the nature and occurrence reason of each component.Based on the lumped mass model of the rotor-bearing system,the oil whirl fault signal is simulated and the influence of the parameters of the rotor-bearing system on the dynamic response of the system is analyzed in detail.By combining the orbit of shaft center,the spectrum and the time-frequency spectrum,the paper analyzes and summarizes the characteristics of oil whip and oil whirl,which lays a theoretical foundation for the fault diagnosis.The simulation and experimental oil whirl signal of the sliding bearing are taken as the main research objects.Firstly,the instantaneous frequency parameters of the signal are estimated by optimizing the spectral concentration index.With the estimated parameters,the Nonlinear FM signal is used as a stationary signal.Finally,the demodulation signal is extracted with the band pass filter.It is a method of instantaneous frequency estimation without relying on time-frequency representation,and has good noise immunity.The simulation and experimental results verify the validity of the nonlinear frequency modulation signal decomposition method to extract the features of the fault signal.The accurate extraction of components is beneficial to the early diagnosis of oil film instability,and it can reveal the process and severity of oil whirl and oil whip.On this basis,the vibration characteristics of oil film instability fault with nonlinear FM component decomposition are summarized systematically.As the diagnostic basis of oil whirl and oil whip fault,it is instructive for the oil film instability fault diagnosis in engineering.