Dynamics of Rotor/Bearing System With Flexible Rotor and Flexible Bearing Support

1997 ◽  
Author(s):  
Agnes Muszynska ◽  
Alex Petchenev ◽  
Paul Goldman
Keyword(s):  
Dynamic Stiffness ◽  
Stability Study ◽  
Modal Testing ◽  
Flexible Rotor ◽  
Dynamic Features ◽  
Sweep Frequency ◽  
Response Data ◽  
Lateral Modes ◽  
Force Excitation ◽  
Bearing System

Abstract The paper analyzes, theoretically and experimentally, the lowest four lateral modes of an isotropic rotor/fluid-lubricated bearing system with flexible rotor and flexible bearing support. The parameters of the analytical model of the system are identified using sweep-frequency modal testing of the rotor rig. A nonsynchronous, circular-rotating-force excitation was applied sequentially at the rotor and at the fluid-lubricated bearing casing, in order to generate the response data. The approach used in this study emphasizes the dynamic features of the system which are invariant to the choice of coordinate system. The system is described using Dynamic Stiffness matrix. This provides an advantage of simplicity, allowing a comprehensive stability study for various system parameters.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

Multi-State Transient Rotor Vibration Control Using Sampled Harmonics

2002 ◽  
Vol 124 (2) ◽  
pp. 186-197 ◽  
Author(s):  
P. S. Keogh ◽  
M. O. T. Cole ◽  
C. R. Burrows
Keyword(s):  
Magnetic Bearing ◽  
Measured Data ◽  
Rapid Decrease ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Transient Vibration ◽  
Stability Boundaries ◽  
Vibration Attenuation ◽  
Harmonic Components ◽  
Bearing System

A technique is introduced to achieve transient vibration attenuation in a multi-input, multi-output flexible rotor/magnetic bearing system. The strategy employs feedback control of measured harmonic components of rotor vibration. Whereas previous harmonic controllers have been based only on steady state vibration characteristics, the new controller also incorporates the transient dynamics. The controller may still be designed from measured data and is determined from target transient vibrational responses arising from step changes in particular disturbances. Account is taken of delays arising from evaluation of harmonic components. Furthermore, stability boundaries for the controller are shown to have significant tolerance to measurement error. The controller is validated experimentally in a flexible rotor/magnetic bearing system and mass loss tests are used to demonstrate rapid decrease in vibration levels with near elimination of transient overshoot.

Ventilatory response to randomly modulated hypercapnia and hypoxia in humans

1994 ◽  
Vol 76 (5) ◽  
pp. 2216-2223 ◽  
Author(s):  
F. Yang ◽  
M. C. Khoo
Keyword(s):  
Ventilatory Response ◽  
Test Procedure ◽  
Estimation Algorithm ◽  
Data Sets ◽  
Dynamic Features ◽  
Adequate Description ◽  
Response Data ◽  
Central Chemoreceptors ◽  
Interaction Component ◽  
Error Method

We have developed a new method for characterizing the ventilatory response to combined hypercapnia and hypoxia (HCVR-HVR) based on the results of a single test procedure. The method is designed to evoke both hypercapnic and hypoxic responses simultaneously and to enable quantification of their static and dynamic features using an estimation algorithm based on the prediction error method. In six healthy subjects, we measured HCVR-HVR by modulating the CO2 and O2 content of the inhaled mixture in the form of two statistically independent random sequences. A two-component dynamic model was found to provide an adequate description of the stimulation-response data sets. The model consisted of a CO2 subsystem and a CO2-O2 subsystem in which a multiplicative interaction between hypercapnia and hypoxia was assumed. The steady-state gains were 2.08 +/- 0.68 (SD) 1.min-1.Torr-1 for the CO2 subsystem and 0.10 +/- 0.05 l.min-1.Torr-1 for the CO2-O2 subsystem, and the corresponding time constants were 116.7 +/- 32.3 and 19.0 +/- 4.4 s, respectively. Our results suggest that the hypercapnic component of HCVR-HVR is mediated primarily by the central chemoreceptors, whereas the interaction component is mediated largely by the peripheral chemoreceptors.

Nonlinear Vibration Prediction of a Highly Flexible Rotor Supported by an Axial Groove Journal Bearing Considering Journal Angular Whirling Motion

2019 ◽  
Author(s):  
Nuntaphong Koondilogpiboon ◽  
Tsuyoshi Inoue
Keyword(s):  
Nonlinear Vibration ◽  
Ball Bearing ◽  
Journal Bearing ◽  
Flexible Rotor ◽  
Large Disk ◽  
Subcritical Bifurcation ◽  
Whirling Motion ◽  
Vibration Prediction ◽  
Rotor Bearing ◽  
Bearing System

Abstract In this study, the difference in dynamic behavior of the rotor-bearing system supported by the bearing model that considers both lateral and angular whirling motions of the journal (model A), and the model that considers only lateral whirling motion (model B) is investigated. The rotor model consists of a slender shaft, a large disk and two small disks supported by a self-aligning ball bearing and an axial groove journal bearing of L/D = 0.6. Three positions of the large disk: 410, 560, and 650 mm measured from the ball bearing, are investigated. Numerical integration of the rotor-bearing system which is modally reduced to the 1st forward mode is performed at above the onset speed of instability until either a steady state journal orbit or contact between the journal and the bearing occurs to identify the bifurcation type. Numerical results using model A indicate subcritical bifurcation with the contact between the journal and the inboard side of the bearing in all three large disk positions, whereas those of model B indicate subcritical bifurcation when the large disk position is at 410 mm, and supercritical bifurcation is observed in the other two cases. Lastly, the experiments at the same three large disk positions are performed. Subcritical bifurcation with the contact between the journal and the inboard side of the bearing is observed in all large disk positions, which conforms with the calculation result of model A. As a result, model A is essential in nonlinear vibration analysis of a highly flexible rotor system.

scholarly journals Balancing of a Flexible Rotor : 4th Report, Some Experiments on a Seven-Disked Flexible Rotor / Bearing System

1974 ◽  
Vol 40 (332) ◽  
pp. 934-944
Author(s):  
Shuzo MIWA ◽  
Takafumi NAKAI ◽  
Ichiro MIMURA ◽  
Yuichi MINAMI
Keyword(s):  
Flexible Rotor ◽  
Rotor Bearing ◽  
Bearing System

Robust optimization of a flexible rotor-bearing system using the Campbell diagram

2011 ◽  
Vol 43 (1) ◽  
pp. 77-96 ◽  
Author(s):  
T. G. Ritto ◽  
R. H. Lopez ◽  
R. Sampaio ◽  
J. E. Souza de Cursi
Keyword(s):  
Robust Optimization ◽  
Flexible Rotor ◽  
Campbell Diagram ◽  
Rotor Bearing ◽  
Bearing System

Robust Control for Flexible Rotor of Magnetic Bearing System

2018 ◽  
Vol 2018.67 (0) ◽  
pp. 111
Author(s):  
Takemitsu TAKAGI ◽  
Chen GAN ◽  
isao TAKAMI
Keyword(s):  
Robust Control ◽  
Magnetic Bearing ◽  
Flexible Rotor ◽  
Bearing System
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