Stability of submerged oil journal bearings under dynamic load

This paper analyses the stability characteristics of submerged oil journal bearings taking into account the oil film history. A linearized perturbation theory about the equilibrium point can predict the threshold of stability but does not reveal post-whirl orbit detail. For this reason a non-linear analysis of a rigid rotor supported on oil journal bearings under unidirectional constant load, unidirectional periodic load and variable rotating load is carried out. The time-dependent form of the Reynolds equation is solved by a finite difference method with a successive overrelaxation scheme to obtain the hydrodynamic forces. Using these forces, the equations of motion are solved by the fourth-order Runge-Kutta method to predict the transient behaviour of the rotor. Journal centre trajectories are obtained for different operating conditions using a high speed digital computer and graphics.