Comparative Studies on the Dynamic Performances of High Speed Turbocharger Rotor Supported on Oil-Free Bearings Versus Conventional Floating Ring Systems

Present work focuses on the dynamic modelling of the dual-disc rotor supported on oil-free bearings idealizing a turbocharger rotor bearing system. The equations of motion of the rotor system are formulated and solved by finite element method to obtain the dynamic response of the system. The gas-foil bearing forces obtained from finite-difference approach at each time-step of solution. The same rotor model is used with the conventional floating ring bearing system where, the bearing forces are provided as displacement dependent time-varying oil and floating ring forces. As a practical environmental condition, the effect of temperature on the viscosity is studied using Dowson equation. The dynamic responses are illustrated both for rotor supported on both gas-foil and floating-ring type bearings. The effects of changes in bearing clearances on the overall dynamic characteristics of the rotor are reported. In order to utilize the gas foil bearing model, an identification study is performed to predict the operating clearance and air viscosity using dynamic response data.