scholarly journals Frequency Enhancement of Oil Whip and Oil Whirl in a Ferrofluid–Lubricated Hydrodynamic Bearing–Rotor System by Magnetic Field with Permanent Magnets

2018 ◽  
Vol 8 (9) ◽  
pp. 1687
Author(s):  
Liao-Yong Luo ◽  
Yi-Hua Fan ◽  
Jyh-Haw Tang ◽  
Ting-Yu Chen ◽  
Nai-Rong Zhong ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Journal Bearing ◽  
Rotor System ◽  
Hydrodynamic Bearing ◽  
System A ◽  
Oil Whip ◽  
Oil Whirl ◽  
Hydrodynamic Journal Bearing ◽  
Whirl Speed

The article describes the effect of a magnetic field applied to a ferrofluid–lubricated hydrodynamic journal bearing–rotor system. A rotor with a single journal bearing in one end was built to be the test rig. The experimental results showed that 3 to 8 permanent magnets, arranged by different methods, can all increase the instability threshold of the oil bearing. Especially, the magnetic field formed by eight magnets has the optimal effect. The whirl speed and the whip speed can be increased from 3024 rpm to 4480 rpm, and from 3184 rpm to 5268 rpm.

Pneumatic hammer instability in the aerostatic journal bearing–rotor system: A theoretical and experimental analyses

2020 ◽  
pp. 135065012090810
Author(s):  
Abdurrahim Dal ◽  
Tuncay Karaçay
Keyword(s):  
Dynamic Response ◽  
Journal Bearing ◽  
Instability Region ◽  
Rotor System ◽  
Pneumatic Hammer ◽  
Nonlinear Dynamic Response ◽  
System A ◽  
Differential Transform ◽  
Hole Configuration ◽  
Aerostatic Bearings

In this study, the pneumatic hammer instability phenomena in the aerostatic journal bearing–rotor system is analysed and discussed for different feeding hole configurations theoretically and experimentally. The influences of the configuration of the feeding holes on the nonlinear dynamics of the system are also investigated. The air flow between the surfaces is modelled with Reynold’s equation and it is numerically solved with differential transform and finite difference hybrid method. Three different aerostatic bearings are modelled and simulated to investigate the ınfluences of the configuration of the holes for different angular speeds. An experimental test rig is designed and tested for different rotor speeds to validate the obtained numerical results. The dynamic response of the system is analysed using waterfall plots, bifurcation diagrams, orbit plots, phase portrait and Poincaré map, which are drawn to determine the pneumatic hammer instability region of the modelled system. The results reveal a nonlinear dynamic response of the rotor centre. In addition, the analysis shows that the feeding hole configuration affects the rotor dynamics and the pneumatic hammer instability region.

Controlling Journal Bearing Instability Using Active Magnetic Bearings

2007 ◽  
Author(s):  
A. El-Shafei ◽  
A. S. Dimitri
Keyword(s):  
Journal Bearing ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Damping Characteristics ◽  
Oil Whip ◽  
Novel Approach ◽  
Oil Whirl ◽  
Load Carrying

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Influence of Lubricant Film Cavitation On the Vibration Behaviour of a Semi-Floating Ring Supported Turbocharger Rotor with Thrust Bearing

2021 ◽  
Author(s):  
Christian Ziese ◽  
Cornelius Irmscher ◽  
Steffen Nitzschke ◽  
Christian Daniel ◽  
Elmar Woschke ◽  
...  
Keyword(s):  
Squeeze Film ◽  
Two Phase ◽  
Hydrodynamic Bearing ◽  
Lubricating Film ◽  
Oil Whip ◽  
Oil Whirl ◽  
Bearing Stiffness ◽  
Run Up ◽  
Stiffness And Damping ◽  
The Impact

Abstract This contribution investigates the influence of outgassing processes on the vibration behaviour of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly non-linear bearing properties, the rotor can be excited via the lubricating film, which results in sub-synchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend both on the kinematic state of the supporting elements and the thermal condition as well as the occurrence of outgassing processes. For modelling the bearing behaviour, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the 3D energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (Half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction and the thermal bearing condition are discussed.

Reliability Analysis for Rotor System with Oil Whip and Resonance Based on Frequency

2012 ◽  
Vol 544 ◽  
pp. 110-114
Author(s):  
Chang Qing Su ◽  
Yi Min Zhang
Keyword(s):  
Failure Probability ◽  
Integration Method ◽  
Random Perturbation ◽  
Rotor System ◽  
Reliability Design ◽  
Rotor Systems ◽  
System A ◽  
Oil Whip ◽  
General Systems ◽  
Engineering Problems

Parameter uncertainty of general systems is inherent in most engineering problems. Based on the regularity of oil whip and resonance for rotor system, the reliability problem of rotor system with oil whip and resonance is studied by applying random perturbation technology and reliability theory considering the correlation of the multi-order natural frequency. The reliability mode and the failure probability of rotor systems are defined. The second-order joint failure probability is obtained by using the numerical integration method. The presented method provided the theoretic basis for the reliability design of the rotor system. A numerical example demonstrated that the proposed method is effective.

scholarly journals Dynamic Vibration Absorber with Negative Stiffness for Rotor System

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Hongliang Yao ◽  
Zidong Chen ◽  
Bangchun Wen
Keyword(s):  
Permanent Magnets ◽  
Vibration Suppression ◽  
Rotor System ◽  
Negative Stiffness ◽  
Vibration Absorber ◽  
Dynamic Vibration Absorber ◽  
Suppression Effect ◽  
System A ◽  
Control Frequency ◽  
Nonlinear Dynamic Characteristics

To suppress the vibration of a rotor system, a vibration absorber combining negative stiffness with positive stiffness together is proposed in this paper. Firstly, the negative stiffness producing mechanism using ring type permanent magnets is presented and the characteristics of the negative stiffness are analyzed. Then, the structure of the absorber is proposed; the principles and nonlinear dynamic characteristics of the absorber-rotor system are studied numerically. Finally, experiments are carried out to verify the numerical conclusions. The results show that the proposed vibration absorber is effective to suppress the vibration of the rotor system, the nonlinearity of the negatives stiffness affects the vibration suppression effect little, and the negative stiffness can broaden the effective vibration control frequency range of the absorber.

Active Self-Excited Vibration Elimination of Rotating Machine With an Electromagnetic Exciter

2009 ◽  
Author(s):  
Chen-Chao Fan ◽  
Min-Chun Pan
Keyword(s):  
Journal Bearings ◽  
Rotor System ◽  
Stable Method ◽  
Rotating Machine ◽  
Oil Whip ◽  
Control Scheme ◽  
Oil Whirl ◽  
Excited Vibration ◽  
Load Carrying ◽  
Auxiliary Device

Journal bearings are commonly used in large rotary machineries because they have excellent mechanical and geometric properties as well as large load-carrying capacities. Nevertheless, the oil whirl and oil whip instabilities limit their applications due to their insufficient stiffness at high running speeds. This paper presents a method to increase the stiffness of a rotating machine using an electromagnetic exciter (EE), which can raise the threshold of instability of the rotating machine and eliminate fluid-induced instability. The EE is a controllable auxiliary device that can provide additional stiffness to the bearings to increase the operating ranges of a rotating machine, while the journal bearings act as load-carrying devices. Together, the EE complements the JB to stiffen the rotor system and raise the threshold of instability. A simple control scheme is used to calculate the amount of supplemental stiffness supplied by the EE. The experimental results demonstrate that the oil whirl and oil whip instabilities of the rotating machine can be eliminated effectively, even at higher running speeds. The advantage of the EE is to offer a faster, more stable method to eliminate fluid-induced instability.

Stabilizing Hydrodynamic Bearing Oil Whip With μ-Synthesis Control of an Active Magnetic Bearing

2015 ◽  
Author(s):  
Alexander H. Pesch ◽  
Jerzy T. Sawicki
Keyword(s):  
Rotation Speed ◽  
Stability Limit ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Related Phenomenon ◽  
Test Rig ◽  
Hydrodynamic Bearing ◽  
Oil Whip ◽  
Oil Whirl ◽  
Excited Vibration

Oil whip is a self-excited vibration in a hydrodynamic bearing which occurs when the rotation speed is above approximately twice the first natural frequency. Because of this, the oil whip phenomenon limits the operational speed of a rotor system on hydrodynamic bearings. Below the oil whip threshold, the related phenomenon of oil whirl can cause large vibrations at frequencies below half the rotation speed. A method is presented for stabilizing oil whip and oil whirl in a hydrodynamic bearing with an active magnetic bearing (AMB). The AMB controller is designed with μ-synthesis model-based robust control utilizing the Bently-Muszynska fluid film bearing model, which predicts the unstable phenomena. Therefore, the resulting AMB controller stabilizes the natural instability in the hydrodynamic bearing. Rotor speed is taken into account by use of a parametric uncertainty such that the method is robust to changes in running speed. The proposed method is demonstrated on an experimental hydrodynamic bearing test rig. Details of the test rig and implementation of the AMB controller design are presented. Waterfall plots for the controlled and uncontrolled system are presented which demonstrate the improved stability limit.

Research on Circumferential Fluid Pressure Distribution and Whirl Stability of Rotor-Bearing System

2008 ◽  
Author(s):  
Ce Chen ◽  
JinFu Yang ◽  
ChaoQun Nie ◽  
Ying Cui ◽  
DaRen Yu ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Fluid Pressure ◽  
Pressure Change ◽  
Eccentricity Ratio ◽  
Oil Film ◽  
Oil Whip ◽  
Oil Whirl ◽  
Bearing Load ◽  
Whirl Speed ◽  
Oil Film Pressure

This paper presents a theoretical analysis of the mechanism of oil whirl, oil whip, and hysteresis in oil whip. A qualitative analysis of the interrelation between whirl frequency, natural frequency, and eccentricity ratio versus speed was conducted using the rotor-bearing load balance equation. By analyzing the interrelation among whirl speed, eccentricity ratio versus speed, rotating speed, oil supply pressure and bearing load, and observing the oil-film load circumferential fluid pressure distribution in the three phases of oil-film load attenuation, instability transition, and oil-film load instability, it was found that in the whirl instability transition phase, the amplitude of rotor whirl speed exceeds half the value of rotor rotation speed, which causes the pressure change in the oil convergent wedge to change from positive to negative, and the pressure change in the divergent wedge to change from negative to positive, and the change in oil-film pressure distribution causes the instability of oil whirl; These changes in oil film pressure distribution are the indicator of oil whirl instability. An experimental study on the whirl instability in a pump supported on fluid film bearings is also presented in this paper to validate the theoretical approach.

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