Lubrication Characteristics Of Journal Bearing Of Water Turbogenerator

Due to the presence of various abnormal vibrations in rotating mechanical systems, a lot of catastrophic accident happened, which is difficult to be explained by linear theory, thus the nonlinear dynamics theory is used to analyze this problem. Multi tilting pad bearings are often used in water turbogenerators and other rotating machinery, and their performance directly affects the operation status of the entire machie, therefore, it is necessary to study the lubrication characteristics of journal bearing of waterturbogenerator.In part1, the engineering background of study of lubrication characteristics of journal bearing was described.Related methods and conclusions of the research at home and abroad were reviewed. The research status and progress was presented in three parts:dynamics of rotor-bearing system, the thermal distortion of pad and the transient lubrication performance of journal bearings. Finally, the topics of this thesis were proposed.In part2, a thermo-elastohydrodynamic lubrication (TEHD) model considering manufacturing tolerances for multi tilting pad journal bearing was established, and the film thickness, film pressure and pad face temperature distributions of each pad were analyzed, then the lubrication performances of the bearings were comparatively examined with respect to effects of manufacturing tolerances on lubrication state with the TEHD model.In part3, a thermal distortion model for multi tilting pad journal bearing was established, and the lubrication performances of the multi-tilting-pad journal bearings were comparatively examined with thermal elastohydrodynamic lubrication (TEHD) model with and without consideration of the thermal distortion of pad faces, and the influences of thermal distortion of pad faces on lubrication state were computed in detail.In part4, a mathematical model of the short bearings under dynamic load is established, and the lubrication performance of short bearing under different dynamic loads was examined, which are the impact load, rotary load and arbitrary dynamic load. The arbitrary dynamic load can be considered as the superimposition of impact load and the rotary load. The orbits of shaft center under different dynamic loads were obtained with numerical analyses.In part5, a mathematical model of the multi-tilting-pad journal bearings in terms of thermal elastohydrodynamic lubrication (TEHD) was established, and the transient lubrication performance of multi-tilting-pad journal bearings was analyzed. The orbit of shaft center from initial position to equilibrium position was obtained with full numerical simulation, and the lubrication performance at equilibrium position was studied, which includes film thickness, hydrodynamic pressure, temperature and thermal distortion and elastic deflection of pad faces.Finally, the conclusions of this thesis were summarized, and the shortage of this work and the research topics in the future were briefly proposed.