Investigation of Sub-Synchronous Noise & Vibration on Turbocharger Fully Floating Hydrodynamic Bearings – Test & Prediction
Automotive engines are facing increased design focus towards downsizing, higher performance and lower emissions, in the process challenging turbocharger (TC) technology to their limits. The rotor of such TC is most commonly supported by hydrodynamic fully-floating or semi-floating bearing systems. These hydro-dynamic bearings exhibit non-linear oil whirl and/or whip in the inner bearing clearance which could translate to objectionable constant tone noise at the vehicle interior. Two variants of fully floating journal bearings are evaluated both numerically and experimentally - hot gas stand and vehicle- and results are presented in this paper.
In numerical simulations, multi-body dynamics (MBD) of flexible rotor and housing structures coupled with Elasto-hydrodynamics (EHD) of the inner and outer oil films are considered. The energy equation for calculation of oil film temperature is considered in EHD using thermal boundary conditions obtained from 3D FE simulations. Detailed numerical investigations were conducted using EHD joint definitions in the above bearing systems. Key EHD indicators like minimum oil film thickness (MOFT), eccentricity ratio, ring speed ratio (RSR), oil flow rate and asperity contact are compared. Good agreement was obtained between testing and prediction, and finer source characterization was achieved using simulations.
KeywordsTurbocharger Rotor Dynamics Hydrodynamic bearings Numerical Simulation Sub-synchronous Vibration Noise
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