Theoretical Prediction of Journal Center Motion Trajectory

1976 ◽  
Vol 98 (4) ◽  
pp. 620-628 ◽  
Author(s):  
D. V. Singh ◽  
R. Sinhasan ◽  
S. P. Tayal
Keyword(s):  
Theoretical Prediction ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Equations Of Motion ◽  
Motion Trajectory ◽  
Rotor Bearing ◽  
The Stability ◽  
Insight Into ◽  
Bearing System

By discretizing time and numerically integrating the equations of motion either for the linearized or the nonlinear journal bearing system, the locus of journal center can be predicted in the wake of a disturbance which upsets the equilibrium. From this locus, not only the stability of the system can be readily checked but also a greater insight into the dynamic characteristics of the rotor bearing systems can be obtained. Systems of solid bearings and porous bearings with journal bearing axes parallel as well as skewed have been studied.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

Dynamic Analysis of a Motorized Spindle With Externally Pressurized Air Bearings

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Chundong Xu ◽  
Shuyun Jiang
Keyword(s):  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Forced Response ◽  
Air Bearings ◽  
Motorized Spindle ◽  
Static And Dynamic Characteristics ◽  
Rotating Speed ◽  
Rotor Bearing ◽  
Bearing System

The purpose of this paper is to investigate the dynamic characteristics of a motorized spindle with externally pressurized air bearings. The externally pressurized air bearings consist of a journal bearing and a double pad thrust bearing with orifice restrictors. The equations of motion for the rotor-bearing system are established considering five degrees-of-freedom (DOF). The perturbation method and the finite difference method are introduced to calculate the static and dynamic characteristics of the air bearings; and the effects of the rotating speed and tilt angle of the rotor on the dynamic characteristics of the air bearings are analyzed. With the dynamic coefficients of the air bearings and the 5DOF rotor-dynamic model obtained, the stability, the unbalance response, and the forced response of the rotor-bearing system are investigated. Finally, the static and dynamic characteristics of the spindle are verified by an experimental study.

Parametric Study of Stability Criteria for Rotor Bearing Model With Viscoelastic Support

2017 ◽  
Author(s):  
S. Chandraker ◽  
J. K. Dutt ◽  
H. Roy
Keyword(s):  
Classical Method ◽  
Equations Of Motion ◽  
Weight Ratio ◽  
High Strength ◽  
Point Of View ◽  
Stability Criteria ◽  
Engineering Structures ◽  
Rotor Bearing ◽  
The Stability ◽  
Bearing System

In the last few decades, intensive research has been carried out on viscoelastic materials. Among them, most importantly polymers and composites thereof find extensive applications in engineering structures and rotors primarily due to quite high strength to weight ratio in comparison with metals. In dynamic modeling of rotor bearing system, incorporation of damping is very important as stationary (external) damping always helps in stability, however rotary damping (internal) promotes instability of rotors above a certain speed. Therefore for modeling point of view, it is very important to consider both internal or external damping effect. For this reason, the dissipation mechanism has been handled in such a way that it provides proper forces irrespective of its presence in a stationary or a rotary frame. Also in present work, both classical method and operator multiplier method are suggested to derive the equations of motion. The analysis also shows the stability zones of the rotor bearing system for various parametric values of different viscoelastic supports. It is found that choosing a right viscoelastic support can increase the stability criteria of the system to some extent.

Effect of Flexible Damped Bearing-Supports on the Dynamic Stability of High-Speed Turbochargers

2013 ◽  
Author(s):  
A. Alsaeed ◽  
G. Kirk ◽  
S. Bashmal
Keyword(s):  
Dynamic Stability ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Element Model ◽  
Dynamic Coefficients ◽  
Speed Range ◽  
Rotor Bearing ◽  
The Stability ◽  
The Finite Element Model ◽  
Bearing System

The aim of this study is to analytically design flexible damped bearing-supports in order to improve the dynamic characteristics of the rotor-bearing system. The finite-element model of the turbocharger rotor with linearized bearing dynamic coefficients is used to solve for the logarithmic decrements and hence the stability map. The design process attempts to find the optimum dynamic characteristics of the flexible damped bearing-support that would give best dynamic stability of the rotor-bearing system. The method is successful in greatly improving the dynamic stability of the turbocharger and may also lead to a total linear stability throughout the entire speed range when used besides the enhanced-performance hydrodynamic bearings.

Stability Analysis of a Whirling Rigid Rotor Supported by FDBs Considering Five Degrees of Freedom of a General Rotor-Bearing System

2014 ◽  
Author(s):  
M. H. Lee ◽  
J. H. Lee ◽  
G. H. Jang
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Time Varying ◽  
Algebraic Equations ◽  
Dynamic Coefficients ◽  
Mass Unbalance ◽  
Whirling Motion ◽  
Rotor Bearing ◽  
The Stability ◽  
Bearing System

A rotor supported by fluid dynamic bearings (FDBs) has a whirling motion by centrifugal force due to the mass unbalance or by the flexibility of shaft. This whirling motion also generates periodic time-varying oil-film reaction and dynamic coefficients even in case of the stationary grooved FDBs. This paper proposes a method to determine the stability of a whirling rotor supported by stationary grooved FDBs considering five degrees of freedom of a general rotor-bearing system. Dynamic coefficients are calculated by using the finite element method and the perturbation method, and they are represented as periodic harmonic functions by considering whirling motion. Because of the periodic time-varying dynamic coefficients, the equations of motion of the rotor supported by FDBs can be represented as a parametrically excited system. The solution of the equations of motion can be assumed as the Fourier series so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Hill’s infinite determinant is calculated by using these algebraic equations in order to determine the stability. The stability of the FDBs decreases with the increase of rotational speed. The stability of the FDBs increases with the increase of whirl radius, because the average and variation of Cxx increase faster than those of Kxx. The proposed method is verified by solving the equations of motion by using the forth Runge-Kutta method to determine the convergence and divergence of whirl radius.

Lyapunov’s Stability of Nonlinear Misaligned Journal Bearings

1995 ◽  
Vol 117 (3) ◽  
pp. 576-581 ◽  
Author(s):  
P. G. Nikolakopoulos ◽  
C. A. Papadopoulos
Keyword(s):  
Journal Bearing ◽  
Direct Method ◽  
Equations Of Motion ◽  
Orbital Stability ◽  
Element Formulation ◽  
Nonlinear Stiffness ◽  
Lyapunov Direct Method ◽  
Rotor Bearing ◽  
The Stability ◽  
General Method

In this paper the stability of nonlinear misaligned rotor-bearing systems is investigated, using the Lyapunov direct method. A finite element formulation is used to determine the journal bearing pressure distribution. Then the linear and nonlinear stiffness, damping, and hybrid (depending on both displacement and velocity) coefficients are calculated. A general method of analysis based on Lyapunov’s stability criteria is used to investigate the stability of nonlinear misaligned rotor bearing systems. The equations of motion of the rigid rotor on the nonlinear bearings are used to find a Lyapunov function using some of these coefficients, which depend on L/D ratio and the misalignment angles ψx, ψy. The analytical conditions for the stability or instability of some examined cases are given and some examples for the orbital stability are also demonstrated.

Nonlinear dynamic characteristics of marine rotor-bearing system under coupled heave and pitch ship motions

2020 ◽  
pp. 095440622097756
Author(s):  
Wenzhuo Zhang ◽  
Ming Li
Keyword(s):  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Ship Motions ◽  
Analytical Mechanics ◽  
Periodic State ◽  
Head Waves ◽  
Nonlinear Dynamic Characteristics ◽  
Rotor Bearing ◽  
The Stability ◽  
Bearing System

The coupled heave and pitch motions of a ship sailing in head waves affect the stability of the marine rotor-bearing system. Based on the theory of analytical mechanics, this study establishes a dynamic model of the rotor-bearing system subjected to the coupled motions of heave and pitch, considering nonlinear oil film moments produced by the tilting of the rotor in the bearings. The nonlinear dynamic behaviours of the system are analysed using numerical methods to obtain Poincaré sections, bifurcation diagrams, and the largest Lyapunov exponents. The results show that dynamic bifurcation characteristics reveal complex quasi-periodic motion of upper and lower branches after the initial instability of the system, and the speed of second instability increase markedly. At high speeds, the amplitude of the rotor system increases sharply, which can cause the rotor to touch the inner wall of the bearings in the quasi-periodic state and a failure to transition to the chaotic state. Additionally, the effects of heave and pitch amplitude variations on the dynamic characteristics of the system are also discussed.

Nonlinear transient response of rough symmetric two lobe hole entry hybrid journal bearing system

2016 ◽  
Vol 23 (2) ◽  
pp. 190-219 ◽  
Author(s):  
Satish C Sharma ◽  
Prashant B Kushare
Keyword(s):  
Surface Roughness ◽  
Transient Response ◽  
Journal Bearing ◽  
Equations Of Motion ◽  
Point Of View ◽  
Stability Point ◽  
Nonlinear Transient ◽  
The Stability ◽  
Bearing System ◽  
Nonlinear Transient Response

The present paper describes the effect of surface roughness orientation pattern on the nonlinear transient response of symmetric two lobe capillary compensated hole entry hybrid journal bearing. Nonlinear equations of motion have been solved with the Runge-Kutta method. The stability of the journal bearing system has been studied by obtaining the journal center motion trajectories. The results of the study reveal that the surface roughness pattern significantly changes the stability of capillary compensated two lobe hole entry hybrid journal bearing. Hence, from the bearing stability point of view, a proper selection of the surface roughness pattern and bearing geometry is essential.

The effect of active control on stability characteristics of hydrodynamic journal bearings with an axial groove

2002 ◽  
Vol 216 (9) ◽  
pp. 939-946 ◽  
Author(s):  
B-H Rho ◽  
K-W Kim
Keyword(s):  
Active Control ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Linear Dynamic ◽  
Conventional Analysis ◽  
Theoretical Investigations ◽  
Rotor Bearing ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Bearing System

Results of theoretical investigations on stability characteristics of an actively controlled hydrodynamic journal bearing are presented. Proportional, derivative and integral controls are adopted for a hydrodynamic journal bearing with an axial groove. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film more accurately than the conventional analysis, which uses the Reynolds condition. Using the bearing's linear dynamic coefficients, which are evaluated from the perturbation method, the stability characteristics of a rotor-bearing system are investigated using the Routh-Hurwitz criteria. It is shown that the instability threshold speed of a rotor-bearing system can be greatly increased and the unbalanced responses of the system can be markedly decreased by both proportional and derivative control of the bearing. Results show that active control of a hydrodynamic journal bearing can be adopted for stability improvement and reduction of the unbalanced whirl amplitude of a rotor-bearing system.

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