Vibration analysis of a dual-rotor-bearing-double casing system with pedestal looseness and multi-stage turbine blade-casing rub

Research and applications of active bearings: A state-of-the-art review

Model based analysis and identification of multiple fault parameters in coupled rotor systems with offset discs in the presence of angular misalignment and integrated with an active magnetic bearing

Finite element modelling, analysis and identification using novel trial misalignment approach in an unbalanced and misaligned flexible rotor system levitated by active magnetic bearings

Dynamic analysis and identification of unbalance and misalignment in a rigid rotor with two offset discs levitated by active magnetic bearings: a novel trial misalignment approach

Application of active magnetic bearings in flexible rotordynamic systems - A state-of-the-art review

Coupled turbine–generator rotor systems are unique in their vibration behavior compared to individual rotor systems. Changes in geometric and dynamic parameters of individual rotor systems and coupling affect the overall response. Since there is also bound to be inherent misalignment at the coupling location, along with residual unbalance in the system, the rotor response contains harmonics corresponding to both unbalance and misalignment. A coupled Jeffcott rotor system with central discs integrated with active magnetic bearing (AMB) is considered in this work. The mathematical model is formulated from four degrees of freedom coupled Jeffcott rotor systems using Lagrange’s equations. A SIMULINKTM model is created to generate vibration and current responses in the time domain. Secondly, a full-spectrum FFT analysis of the time-domain signal is performed to examine the harmonics of the rotor’s vibration response and AMB’s current response. The change in the nature of rotors’ response for various permutations of unbalance and angular misalignment is studied. The advantage of full spectrum over time-domain signals and orbit plots in diagnosing misalignment has been demonstrated.

Some Numerical Studies on Coupled Turbine–Generator Rotor System Models

In the present work, a rotor train system is connected by a flexible coupling and integrated with an auxiliary active magnetic bearing. Due to angular misalignment that exists between the shafts, coupling stiffness varies with shaft rotation. A mathematical function that is time-dependent and which can yield integer harmonics has been chosen to numerically model coupling additive stiffness. The equations of motion have been obtained from Lagrange’s equation. The amplitude and phase of peaks of rotor vibration and AMB current signatures have been obtained in time and frequency domains using least-squares regression technique and full spectrum technique, respectively. They are eventually utilized to identify the intact and additive stiffness of coupling, viscous damping, unbalance magnitude and phase, and the AMB displacement and current stiffness. A SIMULINKTM has been built to generate time domain responses of discs and AMB current. From the EOM of rotors regression equations have been formed in frequency domain to create an inverse problem. The identification algorithm has been found to be robust against noise levels up to 5%.

Identification of Coupling Parameters in Flexibly Coupled Jeffcott Rotor Systems with Angular Misalignment and Integrated Through Active Magnetic Bearing

Misalignment is one of the commonly encountered faults in rotor systems. The standard techniques that are used to detect misalignment are loopy orbits, multiple harmonics with predominant 2X and high axial vibration. In real rotor systems, it is caused due to improper seating of bearing housing on foundation or lack of concentricity between bearing and its housing. This chapter presents a numerical model of the coupling, which mimics the forces/moments produced due to parallel and angular misalignment. The coupling connects two rotor systems each with a centrally mounted disk and simply supported on two flexible bearings. The rotor train is modeled with two-node Timoshenko beam finite elements. An AMB is used as an auxiliary support on rotor-2. The coupling connecting the two rotor systems is modeled by a stiffness matrix, which has both static and additive components. While the static component is unchanging during operation, the additive component displays multi-harmonic behavior and exists only in the presence of misalignment. The multi-harmonic nature of coupling’s misalignment force/moment is mathematically modeled by an appropriate steering function. The development of mathematical model is followed by some response analysis, which shows lateral vibration of rotor, current signal of AMB and the orbit plots of rotor in the presence of misalignment and unbalance.

R. Siva Srinivas

Papers

Application of active magnetic bearings in flexible rotordynamic systems - A state-of-the-art review

Model based analysis and identification of multiple fault parameters in coupled rotor systems with offset discs in the presence of angular misalignment and integrated with an active magnetic bearing

Some Numerical Studies on Coupled Turbine–Generator Rotor System Models

Identification of Coupling Parameters in Flexibly Coupled Jeffcott Rotor Systems with Angular Misalignment and Integrated Through Active Magnetic Bearing

Finite Element Modeling and Analysis of Coupled Rotor System Integrated with AMB in the Presence of Parallel and Angular Misalignments