Stability analysis for a turbocharger rotor system under nonlinear hydrodynamic forces

Turbocharger is a high speed rotor system supported by a pair of floating ring bearings which comprise of double oil films. The stability of its rotor system is governed by not only the structure of the rotor but also by the nonlinear hydrodynamic force of two oil films. In this paper, a lumped dynamics model is developed for a turbocharger rotor system. In order to investigate the nonlinear behavior of the rotor system, the analytical expression of nonlinear hydrodynamic force of outer and inner oil films is derived on the basis of Capone oil film force model. Shooting method and continuation algorithm are used to obtain the periodic solution of the dynamics equation. Based on the numerical simulation results, the effects of rotor imbalance and lubricant feed pressure on the stability discipline and bifurcation behaviors are studied.