Study Of Critical Speed And Nonlinear Dynamics Of Turbocharger Rotor System

The turbine compresses the fresh air intake to increase intake airflow rate, to improve fuel economy and increase power performance to achieve energy saving and environmental protection.The turbocharger is a slight high-speed rotating machinery, its working speed is between100,000rpm and200,000rpm,or even hundreds of thousands of rpm. Its core component is a rotor system with double disc and double support, and it is particularly important to do research for the motion stability of rotor bearing system.The paper is based on related research background and theoretical basis, and a series of research has been done from a sample turbocharger of gasoline engine. Firstly, the mathematical model to find turbocharger critical speed is established, the second and third critical speeds of rotor system are calculated respectively by transfer matrix method and Riccati transfer matrix method. The effects of brace stiffness and the mass of turbine and impeller for the first and second critical speeds of rotor system are analysed. Secondly, the turbocharger dynamic differential equations without floating ring are established and the motion stability is analysed based on related theories of the nonlinear dynamics. Lastly, the turbocharger dynamic differential equations including floating ring are established. The phenomenon of limit cycle that is caused by oil whip is analysed based on the Hopf bifurcation theory and the influence of structure parameters on the limit cycle is also analysed. The purpose is to provide theoretical basis when the designer is designing the structure parameters of the turbocharger rotor system.