An Electroviscous Damper for Rotor Applications

1990 ◽  
Vol 112 (4) ◽  
pp. 440-443 ◽  
Author(s):  
J. L. Nikolajsen ◽  
M. S. Hoque
Keyword(s):  
Rotor System ◽  
Damping Capacity ◽  
Flexible Rotor ◽  
Vibration Damper ◽  
Friction Damping ◽  
Electric Voltage ◽  
Rotor Systems ◽  
Oil Supply ◽  
Coulomb Type ◽  
New Type

A new type of vibration damper for rotor systems has been developed and tested. The damper contains electroviscous fluid which solidifies and provides Coulomb-type friction damping when an electric voltage is imposed across the fluid. The damping capacity is controlled by the voltage. The damper has been incorporated in a flexible rotor system and found to be able to reduce high levels of unbalance excited vibrations. Other proven advantages include controllability, simplicity, and no requirement for oil supply. The anticipated capabilities to circumvent the critical speeds and to suppress rotor instabilities are still unconfirmed.

A Virtual Bearing Method for Optimal Bearing Placement of Flexible Rotor Systems

2017 ◽  
Author(s):  
Shibing Liu ◽  
Bingen Yang
Keyword(s):  
Optimization Problem ◽  
Optimization Method ◽  
Rotor System ◽  
Problem Solution ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Real Coded Genetic Algorithm ◽  
Minimum Number ◽  
Distributed Transfer Function ◽  
Flexible Rotor Systems

Flexible multistage rotor systems have a variety of engineering applications. Vibration optimization is important to the improvement of performance and reliability for this type of rotor systems. Filling a technical gap in the literature, this paper presents a virtual bearing method for optimal bearing placement that minimizes the vibration amplitude of a flexible rotor system with a minimum number of bearings. In the development, a distributed transfer function formulation is used to define the optimization problem. Solution of the optimization problem by a real-coded genetic algorithm yields the locations and dynamic coefficients of bearings, by which the prescribed operational requirements for the rotor system are satisfied. A numerical example shows that the proposed optimization method is efficient and accurate, and is useful in preliminary design of a new rotor system with the number of bearings unforeknown.

Optimal Vibration Reduction of Flexible Rotor Systems by the Virtual Bearing Method

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Shibing Liu ◽  
Bingen Yang
Keyword(s):  
Optimization Problem ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Rotor Design ◽  
Design Variables ◽  
Real Coded Genetic Algorithm ◽  
Minimum Number ◽  
Unique Method ◽  
Distributed Transfer Function

This paper presents a new approach to optimal bearing placement that minimizes the vibration amplitude of a flexible rotor system with a minimum number of bearings. The thrust of the effort is the introduction of a virtual bearing method (VBM), by which a minimum number of bearings can be automatically determined in a rotor design without trial and error. This unique method is useful in dealing with the issue of undetermined number of bearings. In the development, the VBM and a distributed transfer function method (DTFM) for closed-form analytical solutions are integrated to formulate an optimization problem of mixed continuous-and-integer type, in which bearing locations and bearing index numbers (BINs) (specially defined integer variables representing the sizes and properties of all available bearings) are selected as design variables. Solution of the optimization problem by a real-coded genetic algorithm yields an optimal design that satisfies all the rotor design requirements with a minimum number of bearings. Filling a technical gap in the literature, the proposed optimal bearing placement approach is applicable to either redesign of an existing rotor system for improvement of system performance or preliminary design of a new rotor system with the number of bearings to be installed being unforeknown.

Period-1 Motion to Chaos in a Nonlinear Flexible Rotor System

2020 ◽  
Vol 30 (05) ◽  
pp. 2050077 ◽  
Author(s):  
Yeyin Xu ◽  
Zhaobo Chen ◽  
Albert C. J. Luo
Keyword(s):  
Period Doubling ◽  
Rotor System ◽  
Harmonic Amplitude ◽  
Flexible Rotor ◽  
Periodic Motions ◽  
Bifurcation Tree ◽  
Rotor Systems ◽  
Saddle Node ◽  
Jeffcott Rotor ◽  
And Control

In this paper, a bifurcation tree of period-1 motion to chaos in a flexible nonlinear rotor system is presented through period-1 to period-8 motions. Stable and unstable periodic motions on the bifurcation tree in the flexible rotor system are achieved semi-analytically, and the corresponding stability and bifurcation of the periodic motions are analyzed by eigenvalue analysis. On the bifurcation tree, the appearance and vanishing of jumping phenomena of periodic motions are generated by saddle-node bifurcations, and quasi-periodic motions are induced by Neimark bifurcations. Period-doubling bifurcations of periodic motions are for developing cascaded bifurcation trees, however, the birth of new periodic motions are based on the saddle-node bifurcation. For a better understanding of periodic motions on the bifurcation tree, nonlinear harmonic amplitude characteristics of periodic motions are presented. Numerical simulations of periodic motions are performed for the verification of semi-analytical predictions. From such a study, nonlinear Jeffcott rotor possesses complex periodic motions. Such results can help one detect and control complex motions in rotor systems for industry.

Investigation on the Excitation Characteristics and Dynamic Response of the Multi-Support Flexible Rotor With Misalignment

2017 ◽  
Author(s):  
Sen Xiao ◽  
FaYong Wu ◽  
YanHong Ma ◽  
Jie Hong
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Structural Characteristics ◽  
Rotation Frequency ◽  
Frequency Component ◽  
Typical Feature ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Response Characteristics

Aiming at the misaligned problems of high-speed flexible multi-supported rotor system, considering the structural characteristics and load characteristics of the rotor, the unbalanced excitation of the rotor with misalignment is presented and quantitatively described. The mechanical model of the high-speed flexible rotor system with multi-support under misaligned excitation is established. Based on the finite element method, the dynamic equation of the rotor system is given and the dynamic response characteristics of rotor systems are studied. The results show that the misalignment for the highspeed multi-support flexible rotor system can not only lead to 2X excitation and support stiffness nonlinearity, but also bring additional unbalanced excitation to the rotor system. The 2X frequency component is one typical feature for the rotor system with bearing misalignment. The vibration response of the rotor showed a trend of “increased slowly first, then reduced quickly as the rotation frequency increased”, and it turns to be more obvious with the increasing of the nonlinear stiffness and unbalance.

Experimental Investigation With Wireless Sensors of the Nonlinear Interaction Between Rotational Motions and Torsional Vibrations in a Coupled Rigid Rotor-Flexible Rotor System

2013 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Broad Band ◽  
Low Frequency ◽  
Modern Technology ◽  
Rotor System ◽  
Fast Time ◽  
Torsional Vibrations ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Vibrating System ◽  
Modeling Analysis

This work presents an experimental study focused on a challenging signal interpretation issue arising in using wireless tri-axial sensors to measure acceleration components in rotating flexible rotor systems. Experiments with state of-the-art (modern technology microsystems) wireless accelerometers reveal that the dynamics of a rotating and-at the same time torsionally vibrating-flexible rotor system is perceived by the rotating sensor as a fast amplitude modulation of a slowly varying vibration. It is observed that the typical signal furnished by the rotating sensor consists of two distinct zones of harmonics: one is a broad band low frequency zone and is associated with the rigid body rotational motion, whereas the other zone contains distinct higher frequencies associated with torsional vibrations. The interesting result is the fact that in the frequency domain the fast torsional vibrations can be extracted sharply from the overall sensor signal. This is due to fact that the dynamics of the sensor output are characterized by slow and fast time scales. It turns out that the high harmonics of the rotating-and-vibrating system (generic motion) are very close to those of the non-rotating-but-torsionally vibrating system. A definite answer to a physics interpretation of the typical output of a rotating accelerometer (oscillator-based) is established by modeling the whole flexible rotor-sensor system as a singular perturbation coupled oscillators problem. This geometric mechanics modeling-analysis approach presents a global picture of the acceleration sensing property of stiff linear oscillators attached on rotating structures.

Dynamics of a Mechatronic System with Flexible Vertical Rotor

2006 ◽  
Vol 113 ◽  
pp. 223-228 ◽  
Author(s):  
Vytautas Barzdaitis ◽  
Vytautas Žemaitis ◽  
R. Jonušas ◽  
Vytautas Kazimieras Augustaitis ◽  
Vytautas Bučinskas
Keyword(s):  
Angular Speed ◽  
Technical Condition ◽  
Theoretical Modeling ◽  
Rotor System ◽  
Flexible Rotor ◽  
Mechatronic System ◽  
Rotor Systems ◽  
Fatigue Development ◽  
Resonance Frequencies ◽  
Flexible Rotor Systems

The paper is dedicated to research on flexible rotor systems with anisotropic rotor material properties. In addition, the anisotropy of rotor supports alters the rotor system resonance frequencies and the machine has to pass till it attains the operating angular speed. This phenomenon of rotor vibration is observed in vertical rotors. The aim of this work is to compare experimental vibration measurements and results of theoretical modeling. In the paper theoretical model, created from physical one of really existing rotor system is described. Collected experimental data of rotor vibrations in bearings are compared with results of theoretically derived equations. The results of theoretical modeling and research enables for estimation of a more precise technical condition of the rotor system both after the overhaul and during the maintenance and thus to avoid unexpected breakdowns, especially concerning the fatigue development in ball bearing elements.

Hybrid Torsional Vibration Damper Incorporating Conventional Centrifugal Pendulum Vibration Absorber and Magnetorheological Damper

2014 ◽  
Author(s):  
Ehab Abouobaia ◽  
Rama Bhat ◽  
Ramin Sedaghati
Keyword(s):  
Torsional Vibration ◽  
Mr Damper ◽  
Analytical Investigation ◽  
Rotor System ◽  
Magnetorheological Damper ◽  
Vibration Absorber ◽  
Vibration Damper ◽  
Power Requirement ◽  
Rotor Systems ◽  
Centrifugal Pendulum Vibration Absorber

A hybrid torsional vibration damper is proposed in this study incorporating a conventional Centrifugal Pendulum Vibration Absorber (CPVA) and a Magnetorheological (MR) damper. While CPVAs are simple and reliable passive torsional vibration absorbers, their performance is limited to the designed tune conditions. MR dampers have recently received considerable attention due to their inherent fail-safe feature, low power requirement and capability to attenuate vibration under unpredictable environmental conditions. The present research aims at developing a novel hybrid torsional vibration damper combining conventional CPVA with the MR damper capable of suppressing torsional vibration at varying excitation frequencies. This research presents results from analytical investigation of rotor systems integrated with the proposed hybrid torsional vibration damper. The system under investigation consists of a rotor with attached hybrid torsional MR damper subjected to an external harmonic torque. The CPVA has been connected to the cylindrical housing of the MR damper. Different cases have been investigated including: 1- Rotor system without any damper, 2- Rotor system with only CPVA, 3- Rotor system with only torsional MR damper and 4- Rotor system with the hybrid torsional damper. Results for each case have been illustrated and compared against one another.

Modelling of Misaligned Rotor Systems in Aero-Engines

2012 ◽  
Author(s):  
Jun Li ◽  
Jie Hong ◽  
Yanhong Ma ◽  
Dayi Zhang
Keyword(s):  
Dynamic Model ◽  
Rotor System ◽  
Flexible Rotor ◽  
Lagrange Equations ◽  
Rotor Systems ◽  
Nonlinear Properties ◽  
Aero Engine ◽  
Series Of Experiments ◽  
Aero Engines ◽  
Good Agreement

Based on the analysis of structural and dynamic characteristics, a dynamic model of flexible rotor system under misalignment and unbalance excitation in aero-engine was developed through Lagrange equations. The model describes the mechanism and influencing factors of nonlinear properties of misaligned rotors. Then some numerical simulations were performed in order to get the vibration response in time and frequency domain. The results suggest that the rotor system and its coupling may behave in a complex and nonlinear way with the excitation of misalignment and unbalance. The response of the system contains 1× and 2× harmonics, and the spectrum signature closely relate to the misalignment magnitude and the distribution of unbalance mass. A series of experiments were also designed to verify the dynamic model. Their characteristics of response are in good agreement.

scholarly journals An analytical investigation for optimizing the support stiffness and positions of the bearings of a flexible rotor system

2020 ◽  
Author(s):  
Jing Liu ◽  
Changke Tang
Keyword(s):  
Optimization Design ◽  
Rotor System ◽  
Mode Shapes ◽  
Rotational Inertia ◽  
Fe Model ◽  
Flexible Rotor ◽  
Fe Method ◽  
Critical Speeds ◽  
Rotor Systems ◽  
Flexible Rotor Systems

Abstract The support stiffness and positions of the bearings can greatly affect the vibrations of flexible rotor systems. However, most previous works only focused on the effect of the support stiffness of the bearings on the critical speeds of the rigid rotor systems or modal characteristics including natural frequencies and mode shapes, which missed the combine effects of the support stiffness and positions of the bearings. To overcome this issue, an analytical dynamic model of a flexible rotor system based on the finite element (FE) method is proposed. The model considers the support stiffness of the bearings and rotational inertia of the rotor system. The frequency equation of the rotor system is established for solving the critical speeds. The critical speeds and modal deformations of the system from the presented model and the numerical model based on a commercial software are compared to verify the effectiveness of the proposed FE model. The effects of the support stiffness and positions of the bearings on the critical speeds of the flexible rotor system are analyzed. The results show that the critical speeds are positively correlated with the support stiffness. The critical speeds of the flexible rotor system are also greatly affected by the support positions of the bearing. This study can provide some guidance for the optimization design method of the support stiffness and positions of the bearings in the flexible rotor systems.

ACCURACY RATING MEASUREMENT OF VIBRATION ELECTROMECHANICAL DEVICES

2019 ◽  
Vol 1 (7) ◽  
pp. 42-45
Author(s):  
V. A. Golubkov ◽  
V. F. Shishlakov ◽  
A. G. Fedorenko ◽  
E. Yu. Vataeva
Keyword(s):  
Technical Condition ◽  
Rotor System ◽  
Vibration Measurement ◽  
Random Errors ◽  
Mass Ratio ◽  
Signal Flow Graph ◽  
Bond Graphs ◽  
Rotor Systems ◽  
Electromechanical Devices ◽  
Main Components

Electromechanical devices consist mainly of rotor systems. Vibration is the result of the interaction of the elements of the rotor system and is largely determined by the accuracy of manufacturing elements at the production stage and defects arising in the process of operation. The main components of the rotor systems that affect vibration are bearings. To determine the technical condition of the bearings and the service life of the rotor system, it is necessary to accurately measure the unobservable vibrations of the rotor. The article describes the model of the channel for measuring the vibration of an electromechanical system, built using the apparatus of bond graphs. The transfer function is obtained by analyzing the signal flow graph. The systematic and random errors of vibration measurement are analyzed depending on the mass ratio between the system case and the vibration transducer for various sensor masses and attachment rigidity.

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