Nonlinear thermo-mechanic coupling effect of a dual-rotor system with an intershaft bearing

The nonlinear thermo-mechanic coupling effect refers to the interaction between the nonlinear dynamic characteristics of a dual-rotor system and the thermal effect of an intershaft bearing. In this paper, the nonlinear thermo-mechanic coupling effect of the dual-rotor system is proposed and studied by the operating radial clearance and dynamic load of the intershaft bearing. A nonlinear dynamic model of the dual-rotor system under the thermal effect of the intershaft bearing is established by considering nonlinear factors such as the Hertzian contact force and the operating radial clearance of the intershaft bearing. The dynamic load of the intershaft bearing is obtained based on the dynamic responses of the system. Based on this, a thermal effect model of the intershaft bearing considering the nonlinear dynamic characteristics of the system is proposed. The operating radial clearance of the intershaft bearing is attained according to the temperature field of the intershaft bearing. The thermo-mechanic coupling model of the dual-rotor system is presented by connecting the dynamic model and the thermal effect model. The results solved by numerical iteration show that the nonlinear dynamic characteristics of the dual-rotor system are deeply coupled with the thermal effect of the intershaft bearing, and become weaker. In turn, a complex nonlinear thermal effect affects the bearing due to the nonlinear dynamic characteristics of the system. Furthermore, the operating radial clearance of the intershaft bearing is closely related to the thermo-mechanic coupling effect of the system. The operating radial clearance decreases with increasing temperature, decreases with decreasing initial radial clearance, and decreases sharply in the resonance regions. Thus, the “negative clearance” may affect the operating radial clearance of the intershaft bearing, which endangers the operation of the rotor system. Moreover, the nonlinear characteristics of the thermo-mechanic coupling effect become stronger as the ambient temperature increases. The results presented in this paper provide insight into the mechanism of the nonlinear thermo-mechanic coupling effect and new theoretical guidances for the dynamic and thermodynamic design of the intershaft bearing in the dual-rotor system.