Hydrodynamic Lubrication and Bearing Behavior with Impulsive Loads

Abstract

The problem of hydrodynamic lubrication under conditions of suddenly applied loads is of practical importance and theoretical interest. For example, such conditions may occur if a turbine blade fractures. From a theoretical point of view, the classical theory of Reynolds, which is quasi-steady, may not be applicable. Reynolds' equation does not depend on bearing surface accelerations, which may be considerable, but only on bearing surfaces1 velocities. A theory is developed and compared to known exact solutions in the simple squeeze-film case. The theory is then applied to the case of a massive rotor simply supported by a short bearing, to which a large impulsive load is applied about the steady condition. Rotor trajectories are computed and in many instances a large difference is observed between the behavior predicted by the Reynolds equation and the improved theory. Results show that fluid inertia, not included in Reynolds' theory, has the desirable effect of suppressing the trajectory amplitude due to...