Dynamic Behaviors of a Rotor-Bearing System under Base-Transferred Shock Excitations Considering Journal-Bearing Clearance

2010 ◽  
Vol 29-32 ◽  
pp. 703-708 ◽  
Author(s):  
Shao Hua He ◽  
Ping Hao Zhang ◽  
Xin Yue Wu
Keyword(s):  
Journal Bearing ◽  
Inhibitory Effect ◽  
Time Varying ◽  
Transient Responses ◽  
Oil Film ◽  
The Past ◽  
Bearing Clearance ◽  
Rotor Bearing ◽  
Residual Response ◽  
Bearing System

The past researches on the transient responses of rotor-bearing systems under shock excitations paid little attention on impact-contact-rub forces which would arise when taking journal- bearing clearance into account, and these forces’ influences on the overall responses remain unknown until now. In this paper, models of impact-contact force, rub force and oil-film force in a rotor-bearing system were built respectively. Numerical calculation was performed to obtain time-varying responses of those forces while the system suffers base-transferred shock excitations. Influences of those forces on system overall responses were investigated. The main conclusion is that the rub force has no obvious influence on the system responses during shock lasting time, whereas it shows an obvious inhibitory effect on the residual response, making time-varying amplitudes be smoother. Rub force maybe bigger in x direction than in y direction although shock energy in x direction is less than in the y direction. Influences of the oil-film force on response is similar to that of rub force but more severely. It has obvious influences on overall responses both during shock lasting time and residual time.

Hydrodynamic Journal Bearings Optimization Considering Rotor Dynamics Restrictions

2018 ◽  
Author(s):  
Leonid Moroz ◽  
Leonid Romanenko ◽  
Roman Kochurov ◽  
Evgen Kashtanov
Keyword(s):  
Film Thickness ◽  
Induction Motor ◽  
Rotor Dynamics ◽  
Journal Bearings ◽  
Oil Film ◽  
Critical Speeds ◽  
Bearing Clearance ◽  
Rotor Bearing ◽  
Dynamics Analyses ◽  
Bearing System

In this study, optimal designs of hydrodynamic journal bearings for 13.5 MW induction motor prototype is developed based on the design of experiment approach and best sequences method which involves entire rotor-bearing system multidisciplinary simulations. These simulations consist of bearing hydrodynamic characteristics calculation and optimization and rotor dynamics analyses for a rotor-bearing system. The results of rotor dynamics analyses are taken into account as the constraints during optimization. Several journal bearings such as plain cylindrical with a different configuration of pockets, elliptical type, and 4-lobe fixed pad have been considered to select the most appropriate design for the application. The bearing clearance, length, diameter, pockets positions, lobe width, oil viscosity, are applied as design input variables. To find the bearing optimal design, following objective functions were considered: 1) Minimum oil film thickness. Optimal bearing clearance is designed to produce the maximum possible level of minimum oil film thickness in order to avoid or reduce possible metal-to-metal contact; 2) Maximization of the performance is done by minimization of friction power loss. 3) Rotor dynamics simulation for the rotor-bearing system is embedded in the optimization process in order to avoid resonances by providing sufficient critical speeds separation margins from operating speed. The methodology for the bearing simulation is based on the mass-conserving mathematical model, proposed by Elrod & Adams and numerical solution for the equations is generated using finite difference method. Rotor dynamics analyses are performed using finite element method. As the result of the study, optimized bearing designs for 13.5 MW induction motor were generated. Optimized bearings provide sufficient frequency margins for critical speeds for the rotor-bearing system and, at the same time, improved hydrodynamic bearing characteristics: maximized oil film thickness and increased efficiency compared to the starting design. Through the considered bearings examples, the study shows how different parameters, such as bearing clearance, length, diameter, and etc., influence key performance characteristics like bearing minimum oil film thickness, friction power losses, rotor-bearing system critical speeds.

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.

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.

Effect of CSL on the characteristics of six-pocket hybrid irregular journal bearing

2020 ◽  
pp. 135065012093685
Author(s):  
Abhishake Chaudhary ◽  
Arvind K Rajput ◽  
Rajiv Verma
Keyword(s):  
Couple Stress ◽  
Reynolds Equation ◽  
Pressure Field ◽  
Journal Bearing ◽  
Characteristic Parameters ◽  
Galerkin’S Method ◽  
Bearing Clearance ◽  
Bell Mouth ◽  
Bearing Characteristic ◽  
Bearing System

This article examines the effect of couple stress lubricant on the characteristics of six-pocket hybrid irregular journal bearing system. Various shapes of irregular journals viz. barrel, bell-mouth, and undulated journal are considered in the analysis. To model the behavior of the flow of couple stress lubricant in bearing clearance space, the modified form of Reynolds equation is derived by using Stokes theory. The unknown pressure field in Reynolds equation is determined by using Galerkin's method. To illustrate the effect of couple stress lubricant on bearing system, the results for characteristics parameters of journal bearing system are presented. The results noticeably reveal that the presence of different geometrical irregularities in journal may ominously influence the performance of bearing system. Further, the use of couple stress lubricant instead of Newtonian lubricant offers a significant improvement in the value of bearing characteristic parameters of geometrically irregular hybrid journal bearing system viz. [Formula: see text], [Formula: see text] and [Formula: see text].

scholarly journals Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System

2011 ◽  
Vol 18 (1-2) ◽  
pp. 45-52 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen
Keyword(s):  
Nonlinear Dynamics ◽  
System Dynamics ◽  
Journal Bearing ◽  
Rotor System ◽  
Moment Of Inertia ◽  
Dynamics Analysis ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Tilting Pad Journal Bearing ◽  
Bearing System

The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.

Modelling and Analysis of the Dynamic Behavior of an Active Journal Bearing

1994 ◽  
Author(s):  
Linxiang Sun ◽  
Janusz M. Krodkiewski ◽  
Nong Zhang
Keyword(s):  
Pressure Distribution ◽  
Reynolds Equation ◽  
Hydrodynamic Pressure ◽  
Chamber Pressure ◽  
Oil Film ◽  
Simulation Based ◽  
Rotor Bearing ◽  
New Type ◽  
The Stability ◽  
Bearing System

Modelling and analysis of a rotor-bearing system with a new type of active oil bearing are presented. The active bearing basically consists of a flexible sleeve and a pressure chamber. The deformation of the sleeve can be controlled by the chamber pressure during the operation, and so can the pressure distribution of the oil film. Finite Element Methods (FEMs) and the Guyan condensation technique were utilised to create mathematical models for both the rotor and the flexible sleeve. The hydrodynamic pressure distribution of the oil film, for the instantaneous positions and velocities of the flexible sleeve and rotor, was approximated by Reynolds equation. The influence of the chamber pressure on the stability of the rotor system was investigated by numerical simulation based on the nonlinear model. The results showed that the stability of the rotor-bearing system can be improved effectively by implementation of the active bearing.

Non-linear dynamic behaviour of rotor—bearing system trained by bevel gears

2008 ◽  
Vol 222 (4) ◽  
pp. 617-627 ◽  
Author(s):  
M Li
Keyword(s):  
Equilibrium Points ◽  
Rotor System ◽  
Design Stage ◽  
Oil Film ◽  
Bevel Gears ◽  
Linear Dynamic ◽  
Non Linear ◽  
Rotor Bearing ◽  
Stability And Bifurcations ◽  
Bearing System

The vibrations of parallel geared rotor—bearing system have been intensively discussed; however, little attention has been paid to the dynamic analysis of angled bevel-geared system supported on journals. In the present work, the non-linear dynamics of a bevel-geared rotor system on oil film bearings is studied. First, the dynamic model is developed under some assumptions, such as rigid rotors, short-bearings, small teeth errors, and so forth. Then, the non-linear dynamic behaviours of both the balanced and unbalanced rotor system are analysed, respectively, in which the equilibrium points, limit cycles, their stability, and bifurcations are paid more attention. Numerical results show that in the bevel-geared rotor system under the action of non-linear oil film forces there exists a series of complex non-linear dynamic phenomena of rotor orbits, such as Hopf bifurcation, torus-doubling bifurcation, and jump phenomenon. All these features can help us to understand the dynamic characteristics of bevel-geared rotor—bearing system at design stage and during running period. Finally, some concerned problems during the investigation are also present.

Sign in / Sign up

Export Citation Format

Share Document