Effect of texture geometry on the performance of noncircular aerodynamic journal bearings

Abstract

Today, considerable uses of aerodynamic journal bearings have attracted the attention of many researchers in the field of tribology. Therefore, the theoretical and experimental analysis of their performance has been the subject of many researches. Growing application of the gas journal bearings is due to their capability in various engineering fields such as instrumentation and high-speed machines like spindles, small-scale turbomachines, and precision gyroscopes, dental milling machines, and many other rotor-bearing systems. Upgrading the performance of gas bearings by changing their geometry or using new compressible lubricants has always been one of the suggestions proposed by the tribology researchers. Recently, the development of new technologies such as laser milling and lithography increased the possibility of creating textured surfaces as a way to improve the performance of journal bearings. So, in this study, the effects of texture geometry on the steady-state performance of two-lobe noncircular aerodynamic journal bearings are presented. For this purpose, the governing Reynolds equation of hydrodynamic gas lubrication is analyzed by finite element method according to the changes of the lubricant film thickness in presence of the cubical, cylindrical, and ellipsoidal surface textures. Results show that the creation of textures on the lower lobe compared to the upper lobe or the whole surface is more effective on the performance of two-lobe aerodynamic bearings. Also, increasing both the dimple depth and the amount of bearings noncircularity, especially at shallow texture depth, cause more significant changes in the lubricant film pressure distribution and the bearing performance parameters such as load-carrying capacity, attitude angle, and frictional power loss. Further, it is obvious that the creation of cubical, cylindrical and ellipsoidal textures especially at shallow depth with an increase in the noncircularity of bearings’ geometry have a higher impact on the steady-state performance of the studied rotor-bearing system, respectively.