Estimation of Rotor-Bearing Parameters by a Global Optimization Method

2006 ◽  
Author(s):  
E. A. Khorshid ◽  
A. H. Falah
Keyword(s):  
Journal Bearing ◽  
Optimization Methods ◽  
Optimization Method ◽  
Air Gap ◽  
Outer Diameter ◽  
Rotor Bearing ◽  
Vibration Responses ◽  
Optimized Model ◽  
Stiffness And Damping ◽  
Good Agreement

Modeling, experiments and system identification of the linear dynamics of a flexible multi-bearing rotor with two concentrated disks are presented in this paper. Both rotor unbalanced vibration responses through critical speeds were experimentally obtained through accurate control of journal bearing static load. Vibration simulations of this laboratory rotor-bearing system were performed as a linear system. The simulation and the experimental results have large differences for both rotors. These differences occur because of (1)The errors in estimating the journal bearing damping and stiffness coefficients, and, (2)The neglect of the effect of the small radial air gap (20 Mils) at the two disks' outer diameter which provides some additional bearing-like radial stiffness and damping effects. An estimate of these coefficients for both the journal bearing and the rotor-radial air gap is obtained using optimization methods. Good agreement was found between the experimental and the optimized model.

Dynamic Characteristics of TEHD Tilt Pad Journal Bearing Simulation Including Multiple Mode Pad Flexibility Model

1993 ◽  
Author(s):  
Jinsang Kim ◽  
Alan Palazzolo
Keyword(s):  
Heat Transfer ◽  
Elastic Deformation ◽  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Variable Viscosity ◽  
Global Analysis ◽  
Analysis Method ◽  
Stiffness And Damping ◽  
Modal Coordinates ◽  
Good Agreement

Abstract An approach for incorporating the heat transfer and elastic deformation effects into dynamic coefficient calculation is presented. A global analysis method is used, which finds the equilibrium pad tilt angles at each eccentricity position and includes cross-film variable viscosity, heat transfer effects in the lubricant, elastic deformation, heat conduction effects in the pads, and elastic deformation effect in the pivots. Deflection modes are used to approximate deformation of the top surface of the pads. The dynamic coefficients of a single pad are calculated at the equilibrium state of the bearing, based on numerical perturbation with respect to the bearing degrees of freedom. These include journal position, pad rotation, pivot deformation, and modal coordinates. The stiffness and damping coefficients are calculated and show very good agreement with experimental and numerical results from the existing literature.

A method to obtain the linear dynamic coefficients for journal bearing in vertical rotors

2019 ◽  
Vol 72 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong
Keyword(s):  
Coordinate System ◽  
Linear Models ◽  
Journal Bearing ◽  
Leading Edge ◽  
Content Type ◽  
Linear Dynamic ◽  
Dynamic Coefficients ◽  
Vertical Rotor ◽  
Rotor Bearing ◽  
Stiffness And Damping

Purpose The infinitesimal perturbation (IP) method is commonly used in calculating stiffness and damping of journal bearing in horizon rotor systems. The boundary condition (BC) for the perturbed pressure is assumed being zero at leading edge of film, although it is usually not zero because of nonzero pressure gradient. This assumption is sufficiently accurate for most purpose in horizon rotors. However, for journal bearing in vertical rotor-bearing systems, the BC with the assumption in IP method will bring in significant errors in calculating linear dynamic coefficients. This paper aims to propose a method to obtain the dynamic coefficients of journal bearing in vertical rotors. Design/methodology/approach The stiffness and damping are approached based on IP method and the modified BC of perturbed pressure. As it is difficult to predict perturbed pressure at leading edge at a fixed coordinate system using IP method, a dynamic coordinate system is introduced in this method, of which the origin on circumferential direction is defined as the leading edge of film. Findings The effectiveness and accuracy of proposed IP method in dynamic coordinate (IPMDC) system are verified by comparing the obtained results with analytical solutions. The comparison shows that the results from IPMDC present a good agreement with the analytic solutions. Originality/value The proposed method can be applied in obtaining linear dynamic coefficients of journal bearing in vertical rotors with high precisions. Instead of the usual nonlinear analysis of vertical rotors, this method provides a feasibility of predicting the instability threshold of vertical rotor-bearing systems via linear models.

Thermohydrodynamic Analysis of Process-Liquid Hydrostatic Journal Bearings in Turbulent Regime, Part II: Numerical Solution and Results

1995 ◽  
Vol 62 (3) ◽  
pp. 679-684 ◽  
Author(s):  
Zhou Yang ◽  
L. San Andres ◽  
D. W. Childs
Keyword(s):  
Journal Bearing ◽  
Nonlinear Differential Equations ◽  
Flow Characteristics ◽  
Turbulent Regime ◽  
Fluid Temperature ◽  
Numerical Predictions ◽  
Exit Temperature ◽  
Direct Stiffness ◽  
Stiffness And Damping ◽  
Good Agreement

A finite difference scheme is implemented to solve the nonlinear differential equations describing the turbulent bulk-flow on the film lands of a hydrostatic journal bearing (HJB). A Newton-Raphson scheme is used to update the recess pressures and to satisfy the mass continuity requirement at each bearing recess. Comparisons of numerical predictions from the thermohydrodynamic (THD) model with experimental measurements of mass flow rate, fluid temperature, and static stiffness coefficient from a LH2 test HJB article show very good agreement. In particular, the exit temperature of the bearing is lower than the supply temperature; i.e., the liquid temperature decreases along the bearing length. Similar values of direct stiffness and damping coefficients are predicted by the adiabatic THD model and other considering isothermal flow characteristics. However, the THD model predicts lower cross-coupled stiffness and whirl frequency ratio (WFR < 0.5). The results show that for the application presented, the LH2 hydrostatic bearing is more stable than previously thought.

scholarly journals A Vibration Suppression Method for the Multistage Rotor of an Aero-Engine Based on Assembly Optimization

Machines ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 189
Author(s):  
Yue Chen ◽  
Jiwen Cui ◽  
Xun Sun
Keyword(s):  
Vibration Suppression ◽  
Optimization Methods ◽  
Optimization Method ◽  
Rotor System ◽  
Vibration Velocity ◽  
Transfer Model ◽  
Dynamics Model ◽  
Aero Engine ◽  
Vibration Responses ◽  
Optimal Assembly

The assembly quality of the multistage rotor is an essential factor affecting its vibration level. The existing optimization methods for the assembly angles of the rotors at each stage can ensure the concentricity and unbalance meet the requirements, but it cannot directly ensure its vibration responses meet the indexes. Therefore, in this study, we first derived the excitation formulas of the geometric and mass eccentricities on the multistage rotor and introduced it into the dynamics model of the multistage rotor system. Then, the coordinate transfer model of the geometric and mass eccentricities errors, including assembly angles of the rotors at all stages, was established. Moreover, the mathematical relationship between the assembly angles of the rotors at all stages and the nodal vibration responses was established by combining the error transfer model with the dynamics model of the multistage rotor system. Furthermore, an optimization function was developed, which takes the assembly angles as the optimization variables and the maximum vibration velocity at the bearings as the optimization objective. Finally, a simplified four-stage high-pressure rotor system was assembled according to the optimal assembly angles calculated in the simulations. The experimental results showed that the maximum vibration velocity at the bearings under the optimal assembly was reduced by 69.6% and 45.5% compared with that under the worst assembly and default assembly. The assembly optimization method proposed in this study has a significant effect on the vibration suppression of the multistage rotor of an aero-engine.

The Influence of Pad Flexibility on the Dynamic Coefficients of a Tilting Pad Journal Bearing

1987 ◽  
Vol 109 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Jorgen W. Lund ◽  
Lars Bo Pedersen
Keyword(s):  
Approximate Method ◽  
Small Amplitude ◽  
Journal Bearing ◽  
Damping Properties ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Hydrodynamic Solution ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing ◽  
Good Agreement

An approximate method is developed to include the flexibility of the pad in the calculation of the stiffness and damping properties of a tilting pad journal bearing. It is a small-amplitude perturbation solution in which the pad deformation is accounted for solely by the change in clearance. A comparison of results with those obtained from a more complete elasto-hydrodynamic solution shows good agreement.

Influence of Fluid Film Boundary Migration on Dynamic Coefficients of Journal Bearings and Behavior of Rotor System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Zezeng Dai ◽  
Jianhua Cheng
Keyword(s):  
Journal Bearing ◽  
Boundary Migration ◽  
Dynamical Behavior ◽  
Journal Bearings ◽  
Rotor System ◽  
Fluid Film ◽  
Dynamic Coefficients ◽  
Film Boundary ◽  
Rotor Bearing ◽  
Stiffness And Damping

Abstract The position of fluid film in journal bearing will change while the journal moving in bearing, which can be named fluid film boundary migration (FFBM). It is usually ignored in the calculation of linear dynamic coefficients. While, the errors brought by this neglection was not ever investigated in detail. In this paper, the influence of FFBM on bearing dynamic coefficients and rotor system dynamic behaviors are investigated. A new perturbation-based model is proposed to take the FFBM into account by modifying the boundary conditions of governing equations. It is then verified by the experimental results and analytical results from previous research. Furthermore, the effects of FFBM on stiffness and damping in two typical journal bearings are investigated. The result indicates that the FFBM has a significant influence on dynamic coefficients of full circular journal bearing but little impact on journal bearing with axial grooves. Moreover, it affects the stiffness and damping more significantly in the cases of large length-to-diameter ratios or small eccentricity ratios in full circle bearing. Finally, the dynamical behavior of a rotor-bearing system with considering the FFBM is also investigated. The result shows that the FFBM of oil film has remarkable influences on the instability threshold and imbalance responses of the rotor system, which should not be ignored. The conclusions obtained in this research are expected to be helpful for the design of full circular journal bearings or rotor-bearing systems.

Paper 15: Determination and Application of the Dynamic Properties of a Turbo-Rotor Bearing Oil Film

1969 ◽  
Vol 184 (12) ◽  
pp. 111-119
Author(s):  
J. S. Woodcock ◽  
R. Holmes
Keyword(s):  
Journal Bearing ◽  
Dynamic Properties ◽  
Damping Properties ◽  
Experimental Assessment ◽  
Oil Film ◽  
Rotor Bearing ◽  
Stiffness And Damping ◽  
Oil Films

This paper presents a theoretical and experimental assessment of the eight coefficients which describe the stiffness and damping properties of journal bearing oil films, together with their subsequent use in predicting the performance of a real rotor. The performance is checked experimentally.

Dynamic Characteristics of TEHD Tilt Pad Journal Bearing Simulation Including Multiple Mode Pad Flexibility Model

1995 ◽  
Vol 117 (1) ◽  
pp. 123-135 ◽  
Author(s):  
J. Kim ◽  
A. Palazzolo ◽  
R. Gadangi
Keyword(s):  
Heat Transfer ◽  
Elastic Deformation ◽  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Variable Viscosity ◽  
Global Analysis ◽  
Analysis Method ◽  
Stiffness And Damping ◽  
Modal Coordinates ◽  
Good Agreement

An approach for incorporating the heat transfer and elastic deformation effects into dynamic coefficient calculation is presented. A global analysis method is used, which finds the equilibrium pad tilt angles at each eccentricity position and includes cross-film variable viscosity, heat transfer effects in the lubricant, elastic deformation, heat conduction effects in the pads, and elastic deformation effect in the pivots. Deflection modes are used to approximate deformation of the top surface of the pads. The dynamic coefficients of a single pad are calculated at the equilibrium state of the bearing, based on numerical perturbation with respect to the bearing degrees of freedom. These include journal position, pad rotation, pivot deformation, and modal coordinates. The stiffness and damping coefficients are calculated and show very good agreement with experimental and numerical results from the existing literature.

Optimization of Axially Magnetized Stack Structured Permanent Magnet Thrust Bearing Using Three-Dimensional Mathematical Model

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Siddappa I. Bekinal ◽  
Mrityunjay Doddamani ◽  
Soumendu Jana
Keyword(s):  
Mathematical Model ◽  
Permanent Magnet ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Optimization Method ◽  
Air Gap ◽  
Geometrical Parameters ◽  
Outer Diameter ◽  
Element Analysis ◽  
Cylindrical Volume

This work deals with optimization of axially magnetized stack structured permanent magnet (PM) thrust bearing using generalized three-dimensional (3D) mathematical model having “n” number of ring pairs. The stack structured PM thrust bearing is optimized for the maximum axial force and stiffness in a given cylindrical volume. matlab codes are written to solve the developed equations for optimization of geometrical parameters (axial offset, number of ring pairs, air gap, and inner radius of inner and outer rings). Further, the results of proposed optimization method are validated using finite element analysis (FEA) and further, generalized by establishing the relationship between optimal design variables and air gap pertaining to cylindrical volume constraint of bearing's outer diameter. Effectiveness of the proposed method is demonstrated by optimizing PM thrust bearing in a given cylindrical volume. Mathematical model with optimized geometrical parameters dealt in the present work helps the designer in developing PM thrust bearings effectively and efficiently for variety of applications.

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