Nonlinear Dynamic Characteristics of Rod Fastening Rotor with Preload Relaxation

Abstract

Compared to ordinary rotor, rod fastening rotor has the advantages of lighter weight, higher strength and easier installation, so it is widely used in gas turbine. However, in the process of a long-term operation, the rod may be deformed due to the influence of alternating load, high temperature and other uncertain factors. In serious cases, it can even lead to a major accident. The discontinuous characteristic of rod fastening rotor leads to great differences in dynamic characteristics compared to ordinary rotor. Based on the Herz contact theory and GW contact model, the contact effect between two discs was studied, and the relationship among the contact load, the distance between two disks and the equivalent bending stiffness was obtained. Findings show the bending stiffness to decrease nonlinearly with the decrease in contact load. The lumped mass method was used to establish the rotor model. The contact effect was considered and the Runge–Kutta method was used to solve the model. Combined with the bifurcation diagram, time domain diagram and spectrum diagram, the influence of contact stiffness on rotor dynamic characteristics was analyzed. The results show that the dynamic characteristics of the rod fastening rotor are rich due to the influence of nonlinear factors. In the case of uniform relaxation, the contact stiffness has different effects on the response state and frequency doubling amplitude of the system at different speeds, which is mainly related to the motion state of the system. In the case of non-uniform relaxation, the degree of relaxation does not affect the motion state of the system, but only changes the amplitude of vibration. The results provide theoretical support for condition monitoring and fault diagnosis of rod fastening rotor.

DDAGCN: an unsupervised cross-domain identification method for tie rod bolt loosening in a rod-fastening rotor system under different working conditions

“…However, as the core rotating component of gas turbines, the RFR system has been running under harsh and variable load conditions, and the effect of long-term vibration and fatigue loads will inevitably lead to the preloads of tie rod bolts being detuning, resulting in the loosening of tie rod bolts and aggravating the risk of misalignment and rub-impact of the rotor system [7,[23][24][25]. Some literatures have studied the effect of tie rod bolt loosening on the dynamic behaviors and characteristics of RFR systems [6,[26][27][28][29][30]. Therefore, it is necessary and crucial to study the intelligent diagnosis of tie rod bolt loosening for the safe operation of RFR systems.…”

Research on the Influence of Disc–Drum Connection Bolt Preloading Rotor Assembly Modal Characteristics and Diagnosis Technology

“…Finally, the frequency spectrum and orbit of the shaft center of the rotor were obtained via experimental analysis, which verified the accuracy of the numerical analysis. Li [11] established a rotor model of the rod-fastened rotor using the lumped mass method, considering the contact effect, and solved the model using the Runge-Kutta method. The influence of contact stiffness on the dynamic characteristics of the rotor was studied.…”