On the Transient Response of the Thrust Bearing

The transient response of the thrust slider bearing has been studied numerically. Of greatest interest is the mode of boundary layer formation and the subsequent development of the pressure in the supporting film in the slider bearing as it is subject to tangential acceleration. It is planned to study two basic types of bearings — the first being the fixed-shoe type, while the second is the tilting-pd bearing. The bearings are subjected to types of loading (a) a constant load and (b) an inertial load due to the displacement or load on the runner. The computer solution is based on a simplified form of the Navier-Stokes equation in the tangential direction to determine the velocity distribution and a modified form of Reynolds’ equation to determine the pressure distribution along the pad or shoe of the bearing. The resulting formulation is a simple explicit tangential velocity difference equation in time and a fully implicit difference equation solution for the pressure, which is independent of time. The results of this endeavor are quite interesting and significant. For a simple fixed geometry case which allows the supported load to vary, the load versus time curves compare extremely well with previous findings by other investigators using an entirely different mathematical approach. The supporting film is found to be fully developed in the course of a few milliseconds for a step acceleration. For a step deceleration, the squeeze film concept is demonstrated in the flow field. In cases considering inertial loading due to the thrust runner, a tangential acceleration may produce a damped oscillation in the transverse direction. But in all probability, the most interesting discovery was that in a tilting-pad bearing or any simple slider bearing, the center of pressure which corresponds to the pivot point is a function of the film ratio (see equation (I 1)).