Analysis of Dynamic Load Characteristics on Hydrostatic Bearing with Variable Viscosity and Temperature using Simulation Technique

The paper reflects the common design and calculation methods and shows their limitations in regard to the calculation of hydrostatic bearings at high velocities. It analyzes the results of complex dynamic flow simulations of hydrostatic bearings and presents a new design and optimization concept of hydrostatic bearings. This concept analyses the oil flow at high bearing velocities and it optimizes the bearing geometry, the restrictor geometry as well as the geometry of the main mechanical components. Expressions are obtained for the temperature distribution in an externally pressurized thrust bearing for the condition when one bearing surface is rotated. The influence of centripetal acceleration and the combined effect of rotational and radial inertia terms are included in the analysis. Rotation of the bearing causes the lubricant to have a velocity component in an axial direction towards the rotating surface as it spirals radically outwards between the bearing surfaces. This results in an increase in the pumping losses and a decrease in the load capacity of the bearing. A further loss in the performance of the bearing is found when the radial inertia term in addition to the rotational inertia term is included in the analysis. Application of hydrostatic bearings is limited by friction and therewith by velocity. Typical characteristics of the hydrostatic system (load, stiffness, flow) are calculated without a velocity dependency. The geometry of the hydrostatic bearing pockets and their restrictors are optimized by using time continuous pressure distribution at the bearing pocket, laminar flow behavior as well as constant velocity of the bearing. The dynamic effects of the flow at high velocities are not considered. The proposed design has higher load capacity, higher stiffness and damping coefficients, lower flow rate and uniform pressure distribution by using the HTGA/Gray method. A Hydrostatic bearings test bench has been designed, built and setup. The test bench has been monitored with pressure, flow-rate, temperature, displacement and force sensors. Keywords: Hydrostatic Bearing, Pressure, Temperature, Viscosity, Load Capacity, Damping