Coupled Simulation of Rotor Systems Supported by Journal Bearings

Oil whirl and whip phenomena are fundamental to rotor systems supported by journal bearings. Published studies opt for a reduced formulation of the Reynolds equation of lubrication in order to aid the computations. In the current study, the complete Reynolds equation is solved using Pseudo Spectral Methods (PSM) and results compared with reduced solutions. The possibility of certain trends being missed in reduced model simulations is also brought out using a simple example. Rotor shaft and journal bearing systems are numerically modelled and coupled simulations have been carried out for test rotors inspired from literature. A semi analytical derivative estimation method is demonstrated to be superior to conventional finite difference methods in terms of processor load. This will be a useful addition for iterative solvers applied on rotors with more complicated geometry. Time transient analysis is carried out for two test rotors in order to bring out the oil whirl and whip phenomena, where the second one, with an added nonlinear node, shows a whirl along a branch which went undetected in the published reference. In the light of the above trends, the importance of full model numerical simulation is further emphasized.