Rotor-Dynamic Computer Simulations of Rolling Bearing in High-Speed Rotating Machinery

In recent years, the use of rolling bearings in high-speed rotating machinery has become increasingly frequent. Applications where hydrodynamic bearings were traditionally employed are now switching to rolling element bearings. The compressor industry is a notable example. Compared to hydrodynamic bearings, rolling bearings offer the important advantage of reduced friction. However, their use in high speed applications must be carefully evaluated. In fact, the system rotor-dynamics depends heavily on the bearing stiffness and this can change greatly depending on the operating conditions. In this paper, the rolling bearing impact on the stiffness of a high rotating speed shaft system is examined. Bearing stiffness is studied as a function of three important design parameters: load, rotational speed and bearing internal clearance. Although these results are, in principle, applicable to all turbo-machineries, a selected case study will be presented that is best suited for centrifugal compressor applications.