Transient Run-Up Simulations of Rotors in Journal Bearings Considering Mass-Conserving Cavitation Approaches

Abstract

The influence of mass-conserving cavitation modeling approaches on the stability of rotors in journal bearings is investigated. The model consists of a rotor represented by a flexible multibody system and the bearings discretized with finite elements. An approach for the pressure-dependent mixture density and mixture viscosity is made. Due to this mass-conserving cavitation approach, the Reynolds equation becomes explicitly time-dependent. Both subsystems – the multibody system for the rotor and the finite element system for the bearings – are coupled by means of an explicit co-simulation approach. Two different axial boundary conditions for the bearings are considered, namely a bearing submerged in an oil bath and an oil film free to air. The differences are studied in a stationary simulation. Then, the results of transient run-up simulations of a Jeffcott rotor and a turbocharger are discussed.