Influence of electromechanical coupling effects on rotor dynamics in electric-assisted turbochargers

The electrically assisted turbocharger (EAT) enhances engine responsiveness but introduces rotor vibration challenges due to motor integration. However, its electromagnetic effects are often overlooked. This study establishes a floating ring bearing-turbocharger rotor model to investigate these dynamics. Three configurations are compared: Model A (baseline), Model B (added motor mass), and Model C (incorporating electromagnetic effects). Results show Model B’s critical speeds decrease significantly (83%–96%) due to mass increase, whereas Model C’s electromagnetic effects restore the first-order critical speed by 274% compared to Model B. However, higher-order modes show limited electromagnetic compensation. Nonlinear transient analysis reveals Model B exhibits stable limit cycles at medium-high speeds, while Model C forms elliptical orbits at low speeds and chaotic motion at high speeds due to oil film nonlinearities. Waterfall plots demonstrate Model C suppresses sub-synchronous vibrations (0.12×) by 98.5% at 80,000 r/min and stabilizes synchronous vibration amplitude at 0.006 mm (only 0.6% of that in Model B), despite exhibiting a transient 0.6× vortex. Electromagnetic effects markedly improve stability but necessitate balancing multi-field coupling nonlinearities. This study elucidates the dynamic modulation mechanism of electromagnetic effects, bridging a theoretical gap in traditional research and providing crucial support for stability design in high-speed integrated powertrain systems.