Investigation of Weight Effects on the Critical Speed of Inclined Turbocharger Rotor System

Turbochargers have been widely used in various base conditions, such as horizontal, vertical, or inclined. The prediction of the dynamics is of utmost importance to inclined turbocharger designers. In this paper, the effect of weight on the critical speed of an inclined turbocharger rotor coupled with floating ring bearings is investigated. The inclined turbocharger rotor is modeled by lumped mass model. The nonlinear floating ring bearing model is derived using Capone’s model. Then the nonlinear dynamic model of the turbocharger rotor system is obtained. The balance position of the turbocharger rotor system is obtained by solving the nonlinear static equation. Linear system of the turbocharger rotor system is derived based on the balance position, and the critical speed is obtained by solving an eigenvalue problem. Three vibration modes, i.e. conical whirl, cylindrical whirl, and bending are obtained. Increasing the inclined angle would decrease the critical speed. Increasing the inclined angle would decrease the critical speed. Among the three vibration modes, the critical speed of cylindrical whirl furnishes the highest decrease while the critical speed of bending attains the lowest decrease. The vertical turbocharger rotor has a more wide operating speed range than the horizontal turbocharger rotor.