Influences of operational conditions and geometric parameters on the stiffness of aerostatic journal bearings

The stiffness of various geometric designs of aerostatic journal bearings for high-speed spindles was investigated under different operating conditions. First, the stiffness of the front and rear journal bearings was evaluated experimentally using the relationship of force and displacement at different supply pressures (6-9 bar). A numerical model was then developed to simulate journal-bearing stiffness under the same pressure range to validate the results. The model was extended to calculate the stiffness of the designs with various geometric parameters, including bearing length/diameter (L/D) ratios of 0.5, 1.0, and 1.5; different types of restrictor designs (e.g., pocketed orifice versus inherent orifice); supply orifice diameter; radius gap; supply pressures of 6, 7, 8, and 9 bar. These parameters are believed to be crucial to the performance of gas bearings. It was found that gas-bearing geometries had a significant effect on stiffness. The results also provide helpful design guidelines for gas-bearing spindles in high-precision machine applications. (C) 2010 Elsevier Inc. All rights reserved.