Abstract:The gas excitation force on vehicular ball bearing turbocharger consists of sealing fluid excitation force and tip clearance gas excitation force. Therefore, sealing fluid excitation force and tip clearance gas excitation force in a certain vehicular turbocharger can be calculated with the application of Black model and Alford model. The model was simulated with the calculation results so that the influence of sealing fluid excitation force and tip clearance gas excitation force on the critical speed, stability and instability response of the rotor system can be concluded. After that, the simulation was compared with the outcome of critical speed experiment, model without tip clearance gas excitation force solely and model without sealing fluid excitation force and tip clearance gas excitation force jointly. The final result shows that: the sealing fluid excitation force has a damping matrix, which decreases the amplitude and improves the stability of ball bearing-rotor system in turbocharger; gas excitation increases the cross-coupled stiffness and lowers the amplitude in steady system.