Experimental Analysis of Dynamic Oil Film Pressure of Tilting-Pad Journal Bearings

With the increase in capacity demand, the development of rotating machinery is toward larger scale, higher speed, and intellectualization. In order to achieve a safer and more reliable operation, a better vibration performance of the rotor-bearing system is expected. Tilting-pad journal bearings have many advantages such as improved dynamic performance and drastic reduction in instability; therefore, they are widely used in rotating machinery. The nonlinearity of the dynamic oil film force is one of the fundamental parameters for an oil film bearing supported rotor system. A mounts of scholars and technicians have conducted theoretical research in this field. This paper focuses on the experimental research of the nonlinearity of dynamic oil film force. Oil film force was measured in various experiments, where relevance and sensitivity to vibration responses were evaluated under different operation speeds and excitation frequencies. The research was mainly divided into three steps. Firstly, experimental measurements data of oil film pressure under different speeds and static loads were verified by theoretical numerical calculation. Secondly, the feature information of displacement and pressure under different dynamic loads and excitation frequency was obtained from experiments. In addition, the frequency compositions of displacement and pressure were compared. Finally, a newly developed time–frequency analysis tool, named the synchrosqueezing wavelet transform, was employed to characterize the displacement and pressure features. Through the comparison between the time–frequency compositions of these two features,there are more signal characteristics presented in the time–frequency spectrums of dynamic oil film force. Characteristics like amplitude of both excitation frequency and half-frequency whirl frequency are more obvious in those spectrums. It can be concluded that the measurement of dynamic oil film force is an effective method to monitor the real-time status of the rotor-bearing system vibration.