Dynamic Analysis of Electrically Assisted Turbocharger Rotor Considering Contact Effects in Nut Structures

The rotor system of an electrically assisted turbocharger (EAT) is composed of multiple shaft components; The nonlinear connection and contact effects make it difficult to determine the system dynamic characteristics. To improve the modeling accuracy of EAT rotor system and evaluate the influence of contact between multi‐axis components and preload parameters on the dynamic characteristics of the EAT rotor system, a finite element model of an EAT rotor system is developed, and the vibration response is determined by numerical integration. A test bench is constructed and relevant experiments are conducted to validate the accuracy of numerical results. The results indicate: (1) contact effects weaken system stiffness, reducing natural frequencies and critical speeds. Preloading enhances structural stiffness, with a “preload saturation” phase occurring as the preload increases; (2) contact effects increase rotor vibration amplitude and advance bifurcation. The oil‐film whirl of floating ring bearing occurs earlier. Nut structure discontinuities reduce rotor system stability; and (3) increasing nut torque enhances the stability of the rotor system and improves the oil‐film stability. Reducing torque expands the rotor operational speed range. Investigating the influence of nut structure and contact effects on the dynamics of EAT rotor systems provides a theoretical basis for establishing assembly parameter guidelines and facilitates stability‐oriented structural design of EAT system.