scholarly journals Unbalance Vibration of a Rotor-Bearing System Supported by Floating-Ring Journal Bearings

1973 ◽  
Vol 16 (93) ◽  
pp. 503-512 ◽  
Author(s):  
Eiichi NAKAGAWA ◽  
Hiroshi AOKI
Keyword(s):  
Journal Bearings ◽  
Rotor Bearing ◽  
Bearing System

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.

Rotor Bearing System Design on Magnetic Bearings

1995 ◽  
Author(s):  
Pranabesh De Choudhury
Keyword(s):  
System Design ◽  
High Speed ◽  
Journal Bearings ◽  
Magnetic Bearings ◽  
Ball Bearings ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Multistage Centrifugal Compressor ◽  
Tilting Pad Journal Bearings ◽  
Bearing System

Abstract The rotordynamic analysis of a high speed multistage centrifugal compressor supported on radial magnetic bearings, which has been running successfully in the field for 9000 hours to date, is presented. Iterations required to achieve an acceptable rotor configuration using magnetic bearings are discussed. The results of the rotor-bearing system on standard fluid film five shoe tilting pad journal bearings are compared to the dynamics of the rotor on magnetic bearings. Correlation of the observed peak responses with those predicted on magnetic bearings is presented. The actual orbit plots and frequency plots during the coastdown of the rotor-bearing system on auxiliary ball bearings are discussed.

Bifurcation and Chaos Behavior of Rotor-Bearing System With Crack and Pedestal Looseness Faults

2007 ◽  
Author(s):  
Yuegang Luo ◽  
Songhe Zhang ◽  
Feng Wen ◽  
Bangchun Wen
Keyword(s):  
Critical Speed ◽  
Journal Bearings ◽  
Cracked Rotor ◽  
Bifurcation And Chaos ◽  
Coupling Faults ◽  
Speed Range ◽  
Rotor Bearing ◽  
Set Up ◽  
Bearing System ◽  
Main Influence

A dynamic model was set up for the two-span rotor-bearing system with coupling faults of crack and pedestal looseness supported on three plain journal bearings. The nonlinear dynamic behaviors that induced by crack, pedestal looseness and coupling faults are numerically studied. There is quasi-periodic motion appearing in the cracked rotor-bearing system, and it within the sub-critical speed range in the pedestal looseness rotor-bearing system. There is chaotic motion appearing within the supper-critical speed range in the pedestal looseness rotor-bearing system. The pedestal looseness fault is the main influence on the coupling faults system, and there is Period-3 motion appearing in the system. The results may bring up theoretical references for fault diagnoses, dynamic design, and security running to rotor-bearing system.

scholarly journals Bifurcation analysis of rotor/bearing system using third-order journal bearing stiffness and damping coefficients

2021 ◽  
Author(s):  
T. A. El-Sayed ◽  
Hussein Sayed
Keyword(s):  
Equations Of Motion ◽  
Journal Bearings ◽  
Third Order ◽  
Damping Coefficients ◽  
The Third ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Rotor Stiffness ◽  
Stiffness And Damping ◽  
Bearing System

AbstractHydrodynamic journal bearings are used in many applications which involve high speeds and loads. However, they are susceptible to oil whirl instability, which may cause bearing failure. In this work, a flexible Jeffcott rotor supported by two identical journal bearings is used to investigate the stability and bifurcations of rotor bearing system. Since a closed form for the finite bearing forces is not exist, nonlinear bearing stiffness and damping coefficients are used to represent the bearing forces. The bearing forces are approximated to the third order using Taylor expansion, and infinitesimal perturbation method is used to evaluate the nonlinear bearing coefficients. The mesh sensitivity on the bearing coefficients is investigated. Then, the equations of motion based on bearing coefficients are used to investigate the dynamics and stability of the rotor-bearing system. The effect of rotor stiffness ratio and applied load on the Hopf bifurcation stability and limit cycle continuation of the system are investigated. The results of this work show that evaluating the bearing forces using Taylor’s expansion up to the third-order bearing coefficients can be used to profoundly investigate the rich dynamics of rotor-bearing systems.

Experimental and Numerical Rotordynamic Analysis of a 1500 KW Turbocharger

2020 ◽  
Author(s):  
Behzad Zamanian Yazdi ◽  
Dung L. Tran ◽  
Chinmay Deshpande
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
High Speed ◽  
Journal Bearings ◽  
Acid Gas ◽  
Test Loop ◽  
Gas Removal ◽  
Rotor Bearing ◽  
Simulation Results ◽  
Bearing System

Abstract Hydraulic turbochargers are used in sea water reverse osmosis or acid gas removal cycles to recover wasted pressure energy, decrease operating cost, and increase the overall process efficiency. This paper presents rotordynamic analysis of a large hydraulic turbocharger developed for the acid gas removal process (1500 KW output power, shaft diameter of 101 mm, and operating speed of 8,000 rpm). The hydraulic turbocharger has significant advantages when compared to a reverse running pump such as high speed, compact hydraulics, seal-less design and process lubricated bearings. Utilizing a hydraulic turbocharger in acid gas removal cycles results in a much smaller footprint and no external lubrication oil skid and support system for mechanical seals. The turbocharger rotor consists of a hydraulic turbine runner directly coupled to a pump impeller in a back-to-back arrangement. The shaft is supported in the middle by a set of rigid-walled process-lubricated journal bearings resulting in an overhung configuration (bearing span = 180 mm, rotor mass = 50 kg). For a large high-speed rotor-bearing system, the bearing load-carrying capacity and rotordynamic stability are crucial to ensure a stable performance and to avoid catastrophic failure. In the presented study, rotordynamic performance of a rotor-bearing system is evaluated analytically and experimentally. An analytical model is developed to simulate the rotordynamic performance of a shaft supported by a set of journal bearings. The analytical model simulates the rotor’s orbit in the time domain by solving the rotor’s equation of motion, and solving the transient Reynold equation for each bearing simultaneously. In addition, the model considers the effect of turbulence. An in-house test loop is developed and used to evaluate the turbocharger’s hydraulic and mechanical performance. The test loop runs on a LabView-based control system. The rotor vibration is measured by a set of eddy-current probes, oriented perpendicular to each other. The simulation results from the analytical model are compared against measured experimental data. Comparison of the simulated waterfall and bode plots with experimental data shows that the simulation results agree with the measured data for the frequency and amplitude of vibration. Moreover, the effect of turbulence on the rotordynamic performance of the hydraulic turbocharger is investigated, and it is shown that the turbulence significantly changes the rotordynamic behavior of the system.

Computer Optimization of External Fixation and Initial Clamping of a Bushing With Respect to Static and Dynamic Properties and Journal Bearings

1994 ◽  
Vol 116 (4) ◽  
pp. 690-697 ◽  
Author(s):  
J. Kicin´ski ◽  
R. Haller
Keyword(s):  
Computer Program ◽  
External Fixation ◽  
Dynamic Properties ◽  
Journal Bearings ◽  
Work Analysis ◽  
Rotor Bearing ◽  
Computer Optimization ◽  
System Properties ◽  
Special Computer Program ◽  
Bearing System

Various models of external fixation of the bushing, including models which take deformation of the fixation itself into account, have been presented in this work. Analysis of static and dynamic properties of the bearing and of the simple rotor-bearing system as dependent on the bush fixation variant has been performed. Investigations on the influence of preliminary assembly of the bush on the system properties have been performed as well. Calculations were based upon a complex thermoelastohydrodynamic model and a special computer program worked out for this purpose. Obtained results point to wide possibilities of improvement of the system properties by optimization of fixation and clamping the bush in the bearing supports.

A Finite Element Approach to Pad Flexibility Effects in Tilt Pad Journal Bearings: Part II—Assembled Bearing and System Analysis

1990 ◽  
Vol 112 (2) ◽  
pp. 178-182 ◽  
Author(s):  
L. L. Earles ◽  
A. B. Palazzolo ◽  
R. W. Armentrout
Keyword(s):  
Finite Element ◽  
System Analysis ◽  
Journal Bearings ◽  
Complex Eigenvalue ◽  
Finite Element Approach ◽  
Rotor Bearing ◽  
Element Approach ◽  
Bearing System

Pad flexibility effects are studied in an actual bearing. This flexibility is shown to decrease the predicted instability onset speed of the rotor bearing system. The use of complex eigenvalue dependent bearing coefficients as compared with using synchronously reduced coefficients is seen to produce a more significant decrease in the instability onset speed. Further reductions in the instability onset speed are obtained by including pivot stiffness in the complex eigenvalue dependent bearing coefficients.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part II: Numerical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Nonlinear Stability ◽  
Nonlinear Dynamic ◽  
Shooting Method ◽  
Monodromy Matrix ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Rotor Bearing ◽  
Bearing System

The nonlinear stability of a flexible rotor-bearing system supported on finite length journal bearings is addressed. A perturbation method of the Reynolds lubrication equation is presented to calculate the bearing nonlinear dynamic coefficients, a treatment that is suitable to any bearing geometry. A mathematical model, nonlinear coefficient-based model, is proposed for the flexible rotor-bearing system for which the journal forces are represented through linear and nonlinear dynamic coefficients. The proposed model is then used for nonlinear stability analysis in the system. A shooting method is implemented to find the periodic solutions due to Hopf bifurcations. Monodromy matrix associated to the periodic solution is found at any operating point as a by-product of the shooting method. The eigenvalue analysis of the Monodromy matrix is then carried out to assess the bifurcation types and directions due to Hopf bifurcation in the system for speeds beyond the threshold speed of instability. Results show that models with finite coefficients have remarkably better agreement with experiments in identifying the boundary between bifurcation regions. Unbalance trajectories of the nonlinear system are shown to be capable of capturing sub- and super-harmonics which are absent in the linear model trajectories.

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