Influence of Lubricant Film Cavitation on the Vibration Behavior of a Semifloating Ring Supported Turbocharger Rotor With Thrust Bearing

Abstract

This contribution investigates the influence of outgassing processes on the vibration behaviour of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly non-linear bearing properties, the rotor can be excited via the lubricating film, which results in sub-synchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend both on the kinematic state of the supporting elements and the thermal condition as well as the occurrence of outgassing processes. For modelling the bearing behaviour, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the 3D energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (Half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction and the thermal bearing condition are discussed.

Nonlinear vibration phenomena in hydrodynamically supported rotor systems

“…Further improvement could be accomplished due to considering 3d temperature solution for radial [31][32][33], full floating ring [34,80], squeeze film dampers [17], thrust bearings [81,[83][84][85] and full floating disc thrust bearings [47]. A so far missing bearing type are bearings with tilting pads, which are handled in the next section.…”

Analysis of Thermo-Hydrodynamic Lubrication of Three-Lobe Semi-Floating Ring Bearing Considering Temperature–Viscosity Effect and Static Pressure Flow

“…Shuai et al [26] established a thermal fluid model for FRBs with deep and shallow cavities and analyzed the influence of laminar flow and turbulence on stability. Ziese et al [27] adopted the Reynolds equation with mass-conserving cavitation according to the two-phase model to analyze the influence of cavitation on the performance of SFRBs. Based on the written simulation program, Xie and Zhu [28] calculated the static and dynamic characteristics of FRBs considering various coupling factors in a comprehensive and detailed manner.…”