Nonlinear Flutter Response of Tilting 4 Pad Bearings-Rotor System

2011 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen ◽  
R. Gordon Kirk
Keyword(s):  
Transient Vibration ◽  
Oil Film ◽  
Rotor Systems ◽  
Tilting Pad ◽  
Jeffcott Rotor ◽  
Rotor Bearing ◽  
Nonlinear Transient ◽  
Rotor Center ◽  
Design Speed ◽  
Tilting Pad Journal Bearing

Nonlinear analysis is increasingly applied in the dynamics analysis of rotor bearing systems. The use of tilting-pad bearings is now a standard feature of many types of rotor systems. The concern for oil film excitation of the rotor lowest natural frequency is eliminated by the use of the tilting pad journal bearings. For new higher speed or larger low speed applications, the possibility of the pad flutter instability still remains and most commonly used design tools do not consider the pad inertia as a standard feature. In this paper, taking the Jeffcott rotor supported by two 4 pad bearings as an example, the influence of pad inertia and journal diameter were studied. The influence of shaft diameter and pad inertia was determined by the transient response of a simple rotor-bearing system operating over a wide design speed range. The tilting pad journal bearing oil-film force was calculated by a database method. The resulting nonlinear transient vibration is discussed using bifurcation diagrams, orbits, frequency spectrum plots, phase trajectories, and Poincare maps. The results directly show that journal diameter and pad inertia greatly influence the nonlinear vibrations of the journal and rotor center.

Nonlinear Transient Response of Tilting 4 Pad Bearings: Turbocharger Systems

2013 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen ◽  
R. Gordon Kirk ◽  
Yongxin Feng
Keyword(s):  
High Speed ◽  
High Performance ◽  
Dynamical Behavior ◽  
Transient Vibration ◽  
Nonlinear Dynamical ◽  
Rotor Systems ◽  
Tilting Pad ◽  
Speed Range ◽  
Nonlinear Transient ◽  
Tilting Pad Bearings

High speed and high performance engines are often equipped with turbochargers to increase power density over the operating speed range. Tilting pad bearings are now much more applied in many types of rotor systems. This paper presents nonlinear dynamical behavior of a typical turbocharger supported by two tilting 4 pad bearings. The bearing oil-film force was calculated by a database method and the influence of both pad offset and preload were studied. The nonlinear transient vibration is represented by bifurcation diagrams. The results directly show that pad offset and preload greatly influence the nonlinear vibrations of the turbocharger-tilting pad bearings system. In some certain speed range, the motions of the bearing pads are different from that of the bearing journal centerline.

The Analytical Imbalance Response of Jeffcott Rotor During Acceleration

2000 ◽  
Vol 123 (2) ◽  
pp. 299-302 ◽  
Author(s):  
Shiyu Zhou ◽  
Jianjun Shi
Keyword(s):  
Natural Frequency ◽  
Initial Condition ◽  
Constant Acceleration ◽  
Transient Vibration ◽  
Critical Speeds ◽  
Rotor Systems ◽  
Jeffcott Rotor ◽  
Physical Insight

Since many rotor systems normally operate above their critical speeds, the problem of accelerating the machine through its critical speeds without excessive vibration draws increasing attention. This paper provides an analytical imbalance response of the Jeffcott rotor under constant acceleration. The response consists of three parts: transient vibration due to the initial condition of the rotor, “synchronous” vibration, and suddenly occurring vibration at the damped natural frequency. This solution provides physical insight to the vibration of the rotor during acceleration.

Coupling of Rotor-Gear-Casing Vibrations During Extreme Operating Events

1992 ◽  
Vol 114 (4) ◽  
pp. 464-471 ◽  
Author(s):  
F. K. Choy ◽  
J. Padovan ◽  
Y. F. Ruan
Keyword(s):  
Element Model ◽  
Operating Conditions ◽  
Transient Vibration ◽  
Rotor Systems ◽  
Power Plant Equipment ◽  
Modal Synthesis ◽  
Operating Environments ◽  
Rotor Bearing ◽  
The Matrix ◽  
Plant Equipment

During extreme operating environments (i.e., seismic events, base motion-induced vibrations, etc.), the coupled vibrations developed between the rotors, bearings, gears and enclosing structure of gear-driven rotating equipment can be quite substantial. Generally, such large vibrational amplitudes may lead to failures in both the rotor-gearing system and/or the casing structure. This paper simulates the dynamic behavior of rotor-bearing-gear system resulting from motion of the enclosed structure. The modal synthesis approach is used in this study to synthesize the dynamics of the rotor systems with the vibrations of their casing structure in modal coordinates. Modal characteristics of the rotor-bearing-gear systems are evaluated using the matrix transfer technique, while the modal parameters for the casing structure are developed through a finite element model using NASTRAN. The modal accelerations calculated are integrated through a numerical algorithm to generate modal transient vibration analysis. Vibration results are examined in both time and frequency domains to develop representations for the coupled dynamics generated during extreme operating conditions. Typical three-rotor bull gear-driven power plant equipment (compressors, pumps, etc.) is used as an example to demonstrate the procedure developed.

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.

Stability of Rotor-Bearing Systems With Generalized Support Flexibility and Damping and Aerodynamic Cross-Coupling

1975 ◽  
Vol 97 (3) ◽  
pp. 461-469 ◽  
Author(s):  
R. E. Warner ◽  
A. I. Soler
Keyword(s):  
Cross Coupling ◽  
Frequency Dependent ◽  
Oil Film ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Single Mass ◽  
Tilting Pad Bearings

This paper examines stability of the flexible single mass rotor, acted on by motion induced forces due to aero-dynamic cross-coupling and supported most generally by oil film tilting pad bearings which are in turn mounted on flexible, damped supports. Plotted results include the frequency dependent spring and damping coefficients for the 4-pad tilting pad bearing, damping coefficients for the 360-deg squeeze bearing and stability plots of rotor-bearing systems including aerodynamic cross-coupling, the 4-pad tilting pad bearing and the 150-deg partial arc bearing with various support arrangements.

Tilting Pad Bearing Pivot Friction and Design Effects on Thermal Bow-Induced Rotor Vibration

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Dongil Shin ◽  
Alan B. Palazzolo
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Design Parameters ◽  
Flexible Beam ◽  
Thermally Induced ◽  
Tilting Pad ◽  
Speed Range ◽  
Transient Simulations ◽  
Nonlinear Transient ◽  
Tilting Pad Journal Bearing

Abstract The Morton effect (ME) is a thermally induced vibration problem observed in a rotor supported by hydrodynamic bearings. The journal’s synchronous orbiting induces nonuniform viscous heating on its circumference, and the ensuing thermal bow often causes unacceptable vibration levels in the rotor. This paper investigates the influence of the tilting pad journal bearing (TPJB)’s pivot design on the severity and instability speed range of ME vibration. Simulations are conducted with two different types of pivots: cylindrical (CYL) and spherical (SPH), which produce different pad degrees-of-freedom and nonlinear pivot stiffness due to their geometries. The friction between pad and pivot, which only exists with the spherical pivot, is modeled, and its impact on the ME is evaluated. The example rotor model, as obtained from the literature, is single overhung, with experimentally measured excessive vibration and large journal temperature differentials, near 8000 rpm. The bearing and journal are modeled with three-dimensional (3D) finite elements, and the shaft with flexible beam elements for ME simulation. Nonlinear transient simulations are carried out for a wide operating speed range with varying pivot design parameters. Simulation results indicate that the predicted ME instability is sensitive to the pivot shape, pivot flexibility, and pad-pivot friction.

Effect of Scratches on a Tilting-Pad Journal Bearing

2020 ◽  
Author(s):  
Steven Chatterton ◽  
Paolo Pennacchi ◽  
Andrea Vania ◽  
Mohamed Amine Hassini ◽  
Antoine Kuczkowiak
Keyword(s):  
Film Thickness ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Hydrodynamic Performance ◽  
Axial Position ◽  
Steam Turbines ◽  
Local Pressure ◽  
Oil Film ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

Abstract Many industrial rotating machines are equipped with hydrodynamic journal bearings, such as centrifugal compressors, steam turbines, pumps and motors. After some time from the installation, however, the surface of the bearings often presents imperfections and slight damages mainly caused by the presence of harder particles in the lubricant during start-ups and shut-downs, when the hydrodynamic mechanism is not well developed and the mixed lubrication can occur. The presence of scratches on a bearing can lead to variations of the oil film thickness which, in turn, causes significant degradation of the bearing hydrodynamic performance. For example, the reduction of the minimum oil-film thickness can lead to the increase in the local temperature, to local pressure peaks and, finally, to the failure of the bearing. Experimental data relating to scratches on journal bearings are extremely limited in the literature especially for tilting-pad journal bearings (TPJBs). An experimental activity was carried out to study the effect of artificial scratches on pads on the static and dynamic behaviors of a TPJB. The number of scratches, the depth and the axial position have been investigated and the dynamic coefficients have been estimated as well. The experimental results confirmed a degradation of the dynamic performance of the bearing in case of scratches, that it has has been also confirmed by means of numerical simulations.

Research on the Complete Dynamic Model of Tilting-Pad Journal Bearings Including Fluid Film Temperature Effect

2012 ◽  
Vol 157-158 ◽  
pp. 589-594
Author(s):  
Zhen Shan Zhang ◽  
Xu Dong Dai
Keyword(s):  
Journal Bearing ◽  
Dynamic Properties ◽  
Fluid Film ◽  
Effect Of Temperature ◽  
Rotor Systems ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Precise Prediction ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings

Considering the coupling moving of shaft and pads, a theoretical model for calculating the complete dynamic coefficients (CDCs) of tilting-pad journal bearing (TPJB) is described in this paper. The model includes the influence of fluid film temperature. Based on this model, the effect of fluid film temperature on journal equilibrium position, pads inclinations, and complete dynamic coefficients is investigated for given load cases. The numerical results indicate that the effect of temperature is not neglected for the dynamic properties of TPJB. The solution will provide useful tool for precise prediction of dynamic behavior of the rotor systems supported by TPJB.

Three-Dimensional Dynamic Model of TEHD Tilting-Pad Journal Bearing—Part II: Parametric Studies

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Junho Suh ◽  
Alan Palazzolo
Keyword(s):  
Dynamic Analysis ◽  
Numerical Integration ◽  
Equilibrium Condition ◽  
Journal Bearing ◽  
Fe Model ◽  
Time Step ◽  
Transient Dynamic ◽  
Tilting Pad ◽  
Nonlinear Transient ◽  
Tilting Pad Journal Bearing

This paper presents a new analysis method for a thermo-elasto-hydro-dynamic (TEHD) tilting pad journal bearing (TPJB) system to reach a static equilibrium condition adopting nonlinear transient dynamic solver, whereas earlier studies have used iteration schemes such as Newton–Raphson method. The theoretical TPJB model discussed in Part I of this research is combined into a newly developed algorithm to perform a bearing dynamic analysis and present dynamic coefficients. In the nonlinear transient dynamic solver, physical and modal coordinates coexist for computational efficiency, and transformation between modal and physical coordinate is performed at each numerical integration time step. Variable time step Runge–Kutta numerical integration scheme is adopted for a reliable and fast calculation. Nonlinear time transient dynamic analysis and steady thermal analysis are combined to find the static equilibrium condition of the TPJB system, where the singular matrix issue of flexible pad finite element (FE) model is resolved. The flexible pad TPJB model was verified by comparison with other numerical results. Simulation results corresponding with the theoretical model explained in Part I are presented and discussed. It explains how the TPJB dynamic behavior is influenced by a number of eigenvector of flexible pad FE model and pad thickness. Preload change under fluid and thermal load is examined.

Numerical Investigation for Characteristics and Oil-Air Distributions of Oil Film in a Tilting-Pad Journal Bearing

2018 ◽  
Author(s):  
Aoshuang Ding ◽  
Yaobing Xiao
Keyword(s):  
Shear Stress ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Side Wall ◽  
Mechanical Loss ◽  
Load Pressure ◽  
Oil Film ◽  
Air Volume ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

This paper analyzes the effects of air in the oil film of a tilting-pad journal bearing on oil-air distributions and characteristics. With a gaseous cavitation model and shear stress transport (SST) model with low-Re correction included, the air backflow from the outlet boundary is analyzed in numerical simulations of a titling-pad journal bearing at 3000 rpm rotation speed and under 180 kN load. The simulated bearing load, pressure and mechanical loss are in good accordance with the experimental data, indicating that the simulation results of the air backflow from the outlet boundary can catch the hydrodynamic characteristics accurately. Based on the analyses of simulated air volume fraction and shear stress, the shear stress of the high-pressure loaded area is mainly influenced by the velocity gradient in the normal direction to the rotor-side wall, not the air backflow and gaseous cavitation. In the unloaded area, the gaseous cavitation occurs around the center part, following the gaseous cavitation mechanisms. The backflow air flows into the low-pressure unloaded area from the outlet boundary and has a clear interval with the air from the gaseous cavitation. The air volume fraction increases with these two air sources and affects the mixture viscosity significantly, eventually influencing the shear stress on the rotor-side wall and bearing mechanical loss.

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