Load Effect on the Perturbed Oscillation Damping Ability of an Unbalanced Rotor in Three Lobe Bearings

Oscillation disturbances of the rotor in turbomachines, compressors, combustion engines and other rotary equipment are affected by various factors which cause the wear of the rotor and bearing surfaces such as the mass unbalance factor. This phenomenon always leads to the failure of parts and interruptions of the equipment performance. Therefore, to improve efficiency of the system in controlling the rotor fluctuations, recognition of the factors affecting the strength of journal bearings is important, as they are the most common type of rotor support in such rotary machines. In this study, the effect of external load, as an indicator of mass unbalanced rotor eccentricity ratio in the bearing clearance space, on the dynamic behavior of noncircular three lobe bearings with micropolar lubricant is investigated. For this purpose, the governing Reynolds equation and the equation of rotor motion have been rewritten and evaluated using FEM and 4th order Runge-Kutta methods in static conditions and successive time steps after the occurrence of rotor disturbances. The results indicate that the amplitude and intensity of rotor disturbances are developed in the form of periodic, KT periodic and quasiperiodic motions in the mean values of eccentricity ratio and they are changed to limited cyclic oscillations with small amplitudes in low or especially high values of the eccentricity ratios.