| High efficiency,low energy waste,little pollution are always the targets of the development of automotive engine,applying turbocharger technology is one of the effective measures to achieve these goals. The rotor of turbocharger has high rotary speed,and its support structure is very complex,so there are particularities in the dynamic model and analysis of the rotor system of turbocharger. Furthermore,the operating environment of the turbocharger is execrable,and the crack is easy to appear in the shaft when engine running. Now,the study on the nonlinear dynamic behavior of the rotor of turbocharger with foundation excitation and crack isn't enough,it can't satisfied with the requirements of the actual design of turbocharger. This paper completed the following study with the background of the actual engineering project:Considering the effect of shaft whirl speed on the open and close of the crack, two-disk catilevel rotor system with transverse crack in near left disk of some type turbocharger was studied in this article. The dynamic equations was solved by Runge-Kutta method in this article. The bifurcation rules of period response of cracked rotor system with multi-degree of freedom are obtained. The motion characteristics of the rotor system is determined according to the fractal dimension of Poincarémap of phase aspect,the trajectory of the shaft center and frequency spectrum at certain speed and physical parameters of rotor system.The nonlinear dynamic model of two-disk catilevel rotor-bearing system that was supported by two sliding bearing was builded.The nonlinear dynamic behavior of rotor system of turbocharger with transverse crack and foundation excitation come from the vibration of the operating engine was synthetical analysed.Considering the effect of foundation excitation and nonlinear oilfilm force respectively,the dynamic characteristics of rotor system was contrastive analysed,the effect of two factors for the dynamic behavior of cracked rotor system was studied.
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