Analysis of the three dimensional rotor dynamics characteristic of the turbocharger

Constituted the three dimension analysis model of the turbocharger rotor considering the stiffness of the impellers and the torsional stiffness of the shaft. The 3D model dynamic characters of the turbocharger rotor were analyzed by the FEM (finite element method). Developing the analysis of the critical speed, the validity of the three dimensional model was verified by the transfer matrix method and FEM using the beam element. The result of the critical speed analysis shows that the bending stiffness will be reduced when the rotor with thick impeller is simplified by the lumped mass method. The unbalance response analysis of the rotor system shows that the rotor system exists the coupled flexural and torsional vibration. The coupled flexural and torsional vibration represents non-synchronous half-frequency vibration phenomenon. The coupled flexural and torsional vibration will be more observable as faster as the rotor rotates. When the rotation speed is near the coupled flexural and torsional vibration frequency, the rotor system vibration is the coupled flexural and torsional vibration. When the rotation speed is on the other whirl frequency the rotor system shows the flexural vibration.