Dynamic analysis of liquid-lubricated hydrostatic journal bearings

Hybrid bearings offer advantages that hydrodynamic bearings cannot. By combining the hydrostatic and hydrodynamic effects, a hybrid bearing reduces the dependency of its behavior on the lubricant viscosity, bearing clearance, bearing surface area, or other common parameters that develop the forces in hydrodynamic bearings. The combination permits the hybrid bearing to be incorporated into rotor designs where externally supplied lubrication is impractical. In place of turbine oil or other externally supplied lubricants, the working fluid of the rotor may be used. Adding in the possibility of unlimited life and a superior dynamic behavior over anti-friction bearings explains their attractiveness. It is for these reasons that they are now being pursued for use in the Space Shuttle main engine pumps and in future delivery systems. The current interest and lack of adequate analytical tools highlight the need for this type of study.; An effective and practical method to predict the static and dynamic behavior of hybrid bearings is developed. As a by-product of the research, a computer code is generated to enable rapid solutions of the method. The model includes the three major fluid effects in the bearing; the orifice restriction, inertia losses at the pocket edges, and hydrodynamic effects on the bearing land regions. Lubrication is modeled and calculated using a finite element solution of Reynolds equation with turbulence corrections. Nuclear coolant pump bearings and liquid hydrogen fuel pump bearings are some of the examples studied. Besides radial, a capability to analyze thrust bearings is also demonstrated.; A rocket motor bearing similar in design to that proposed for the space main engine fuel pumps is examined in detail. Changes in the static and dynamic behavior of the bearing are tracked for variations in the shaft speed, bearing clearance, orifice diameter, shaft position, and hydrostatic pocket arrangement. The flow rate, average pocket pressures, stiffness, and damping are employed as a measure of the static and dynamic characteristics of the bearing.