Dynamic stability analysis of a high-speed diesel engine turbocharger subjected to aerodynamic loads and engine-induced vibration

The dynamics of a high-speed turbocharger supported on floating-ring bearings is investigated numerically under the effect of engine-induced vibrations and aerodynamic loads. The finite-element model predicts the nonlinear response while engine excitations are simulated as time-varying force functions on the rotor-bearings. The bearing parameters are estimated by solving the 2-D Reynolds equation. Modified noncircular volute theory is used to calculate radial thrust loads due to aerodynamic effects. The numerical predictions agree with the experimental observations of a fully-loaded turbocharger that show no significant second harmonic amplitudes of the engine frequency. However, the engine frequencies are at comparable amplitudes with the Sub High and 1X amplitudes at higher speeds, where the aerodynamic loads are not significant. In the subsynchronous region, amplitudes at the engine-excitation frequency are observed at the second harmonic for high speeds. Moreover, the dynamic stability is significantly influenced by the variation in the magnitude of the engine-induced vibration.