Effect of Eccentricity on the Force Response of a Hybrid Bearing

Abstract

The effect of journal eccentricity on the static and dynamic performance of a water lubricated, five-recess hybrid bearing is presented. The hydrostatic bearing has been designed to operate at a high speed and with a large level of external pressurization. The operating conditions determine the flow in the bearing to be highly turbulent and strongly dominated by fluid inertia effects. The analysis covers the range of journal center displacements directed toward the middle of a recess and toward the mid-land portion between two consecutive recesses. Predicted dynamic force coefficients are constant for small to moderate eccentricities. For large eccentricities, fluid cavitation and recess position determine large changes in the bearing dynamic performance. The effect of fluid inertia force coefficients on the threshold speed of instability and whirl frequency ratio of a single mass flexible rotor is discussed.