Dynamic Modeling and Stability Analysis of the Rod-Fastening Rotor System with the Different Preload Status

With the development of gas turbine technology, disk-distributed rod-fastening combined rotor systems are widely used in power machines such as heavy-duty gas turbines and aero engines. The connection structure in rod-fastening combined rotor is subjected to high temperature, unbalanced forces, and moments during operation, which can affect the vibration characteristics and dynamic stability of the combined rotor. However, few studies have been conducted to investigate the rotor vibration characteristics considering the dynamic parameters of the rod-fastening connection structure. Therefore, this paper establishes the dynamic equations of the rod-fastening combined rotor, which considers the contact effect between disks and the equivalent simplification of the rod preload force. The New-mark-β method is applied to numerically solve the kinetic equations to investigate the kinetic and bifurcation characteristics of rotor systems with different preload states under nonlinear oil film forces. The time-domain vibration waveform, three-dimensional spectrograms, the bifurcation diagram, and the poincaré section are applied to investigate the dynamic behavior of the rod-fastening rotor under different preload conditions. The results show that different preload states cause various frequency components of the system, and insufficient preload raises the system’s instability threshold, which even leads to oil whip. The research results help to detect the state of the rod-fastening rotor-bearing system and prevent failures due to changes in the preload state of the fastened rod.