Nonlinear Analysis and Characteristic Variation of Self-Excited Vibration in the Vertical Rotor System Due to the Flexible Support of the Journal Bearing

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Atsushi Nishimura ◽  
Tsuyoshi Inoue ◽  
Yusuke Watanabe
Keyword(s):  
Journal Bearing ◽  
Vibration Characteristics ◽  
The Self ◽  
Radial Clearance ◽  
Fluid Viscosity ◽  
Rotating Shaft ◽  
Flexible Support ◽  
Characteristic Variation ◽  
Excited Vibration ◽  
Pump Shaft

Various vibration problems occur in rotating machinery. Specifically, the large amplitude vibration may occur in the vertical pump using a journal bearing. In an actual vertical pump, the stator's structure supporting the pump shaft may be relatively flexible. In such a case, rotor's motion such as amplitude of the self-excited vibration is not able to be predicted accurately without considering the nonlinear fluid film force reacting in the relative motion between the shaft and the flexibly supported bearing stator. However, the vibration characteristics in such situations have not been explained theoretically so far. In this paper, the vibration characteristics of a vertical rotating shaft with journal bearing are investigated. The nonlinear steady-state vibration analysis of the self-excited vibration is demonstrated, and the influences of the parameters, such as fluid viscosity, radial clearance, and stiffness and damping coefficients of the flexible support of bearing stator, on the vibration characteristics of the system are explained. Moreover, these theoretical results of the self-excited vibration in the vertical rotating shaft with journal bearing are verified both numerically and experimentally.

Characteristic Variation of Self-Excited Vibration in the Vertical Rotor System due to the Flexible Support of the Journal Bearing

2016 ◽  
Author(s):  
Atsushi Nishimura ◽  
Tsuyoshi Inoue ◽  
Yusuke Watanabe
Keyword(s):  
Journal Bearing ◽  
Vibration Characteristics ◽  
Rotor System ◽  
The Self ◽  
Radial Clearance ◽  
Fluid Viscosity ◽  
Rotating Shaft ◽  
Characteristic Variation ◽  
Excited Vibration ◽  
Pump Shaft

Various vibration problems occur in rotating machinery. Specifically, the amplitude of shaft motion can be large in the case of vertical pump using a journal bearing. In such case, rotor motion such as self-excited vibration is not able to be predicted accurately without considering both rotordynamic fluid force and contact phenomena to the bearing surfaces or boundary lubrication condition. Moreover, in an actual vertical pump, the stationary side structure that supports the pump shaft may be relatively flexible. However, the vibration characteristics in such situations have not been so far explained simply. The purpose of this paper is a development of the simple and quantitative method for evaluating vibration characteristics of a vertical rotating shaft with journal bearing. In this study, the rotor system flexibly supported by a journal bearing at the axial center is considered. Eigenvalue analysis is demonstrated for the linearized system, and steady-state vibration analysis of the self-excited vibration is carried out for the nonlinear system. As a result, the effect on the vibration characteristics of the system by changing fluid viscosity, radial clearance, stiffness and damping of the support is clarified. Moreover, the obtained experimental results correspond to the theoretical results of the self-excited vibration qualitatively.

The Investigation of the Influence of Structure Parameters on the Friction-Induced Self-Excited Vibration

2011 ◽  
Vol 66-68 ◽  
pp. 933-936
Author(s):  
Xian Jie Meng
Keyword(s):  
Nonlinear Dynamics ◽  
Numerical Method ◽  
Calculation Result ◽  
Dry Friction ◽  
Vibration Amplitude ◽  
The Self ◽  
Structure Parameters ◽  
Dynamics Model ◽  
Excited Vibration ◽  
Nonlinear Dynamics Model

A one degree of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction was built firstly, the numerical method was taken to study the impacts of structure parameters on self-excited vibration. The calculation result shows that the variation of stiffness can change the vibration amplitude and frequency of the self-excited vibration, but can not eliminate it, Along with the increase of system damping the self-excite vibration has the weakened trend and there a ritical damping, when damping is greater than it the self-excite vibration will be disappeared.

The Effect of Shear Flow and Dissolved Gas Diffusion on the Cavitation in a Submerged Journal Bearing

2000 ◽  
Vol 123 (3) ◽  
pp. 494-500 ◽  
Author(s):  
M. Groper ◽  
I. Etsion
Keyword(s):  
Mass Transfer ◽  
Shear Flow ◽  
Mass Transport ◽  
Transport Mechanism ◽  
Journal Bearing ◽  
Gas Diffusion ◽  
Gas Bubble ◽  
Dissolved Gas ◽  
Rotating Shaft ◽  
Mass Transfer Mechanism

Two possible, long standing speculated mechanisms are theoretically investigated in an attempt to understand previous experimental observations of pressure build up in the cavitation zone of a submerged journal bearing. These mechanisms are (1) the shear of the cavity gas bubble by a thin lubricant film dragged through the cavitation zone by the rotating shaft and (2) the mass transfer mechanism which dictates the rate of diffusion of dissolved gas out of and back into the lubricant. A comparison with available experimental results reveals that while the cavitation shape is fairly well predicted by the “shear” mechanism, this mechanism is incapable of generating the level of the experimentally measured pressures, particularly towards the end of the cavitation zone. The “mass transport” mechanism is found inadequate to explain the experimental observations. The effect of this mechanism on the pressure build up in the cavitation zone can be completely ignored.

Influence of geometric parameters and operating conditions on the thermohydrodynamic behaviour of plain journal bearings

2000 ◽  
Vol 214 (5) ◽  
pp. 445-457 ◽  
Author(s):  
I Pierre ◽  
M Fillon
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Radial Clearance ◽  
Geometric Factors ◽  
Essential Components ◽  
Mass Flowrate

Hydrodynamic journal bearings are essential components of high-speed machinery. In severe operating conditions, the thermal dissipation is not a negligible phenomenon. Therefore, a three-dimensional thermohydrodynamic (THD) analysis has been developed that includes lubricant rupture and re-formation phenomena by conserving the mass flowrate. Then, the predictions obtained with the proposed numerical model are validated by comparison with the measurements reported in the literature. The effects of various geometric factors (length, diameter and radial clearance) and operating conditions (rotational speed, applied load and lubricant) on the journal bearing behaviour are analysed and discussed in order to inform bearing designers. Thus, it can be predicted that the bearing performance obtained highly depends on operating conditions and geometric configuration.

Self-Vibration Characteristics of Plane Gate in Inverted Siphon Project

2012 ◽  
Vol 160 ◽  
pp. 64-68
Author(s):  
Hui Fang Xue ◽  
You Wang
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Element Model ◽  
Vibration Characteristics ◽  
The Self ◽  
Vibration Modes ◽  
Vibration Frequencies ◽  
Small Opening ◽  
First Order ◽  
Inverted Siphon

Based on the vibration problem of the plane gate in the inverted siphon exit of a large-scale hydraulic project in northern Xinjiang, the software ANSYS is used to build the entity model and finite element model. Considering the influence of fluid-solid coupling, the self-vibration characteristics of the gate in the water and without water are analyzed. The first six self-vibration frequencies and vibration modes of the gate are calculated. The results show that the height of water has a significant impact on the self-vibration frequencies of the plane gate. The first order natural frequency on the condition of small opening is decreased by 28.5%. It shows that the structure of the plane gate must be improved.

Experimental study on vertical vibration characteristics of medium-low speed maglev vehicle when standing still on steel beams

2021 ◽  
pp. 095440972110324
Author(s):  
Miao Li ◽  
Xiaohao Chen ◽  
Shihui Luo ◽  
Weihua Ma ◽  
Cheng Lei ◽  
...  
Keyword(s):  
Coupled System ◽  
Vertical Vibration ◽  
Vibration Characteristics ◽  
Steel Beams ◽  
Steel Beam ◽  
Air Spring ◽  
Low Speed ◽  
Maglev Vehicle ◽  
Excited Vibration ◽  
Eigen Frequencies

Levitation stability is the very basis for the dynamic operation of Electromagnetic Suspension (EMS) medium-low speed maglev trains (MSMT). However, self-excited vibration tends to occur when the vehicle is standing still above the lightweight lines, which remains a major constraint to the promotion of medium-low speed maglev technology. In order to study the vertical vibration characteristics of the coupled system of MSMT when it is standing still above lightweight lines, levitation tests were carried out on two types of steel beams: steel beam and active girder of the turnout, with a newly developed maglev vehicle using levitation frames with mid-set air spring. Firstly, modal tests were carried out on the steel beam to determine its natural vibration characteristics; secondly, the acceleration signals and the dynamic displacement signals of the air spring obtained at each measurement point were analyzed in detail in both the time and frequency domains, and the vertical ride comfort was assessed by means of the calculated Sperling index. Subsequently, theoretical explanations were given for the occurrence of self-excited vibration of coupled system from the perspective of the vehicle-to-guideway vibration energy input. Results show that the eigen frequencies of the vehicle on the steel beam and the turnout are 9.65 Hz and 2.15 Hz, respectively, the former being close to the natural frequency of the steel beam while the latter being close to the natural frequency of the air spring suspension system, thus causing the self-excited vibration of the coupled system. It is recommended to either avoid the main eigen frequencies of the coupled system or to increase the damping of the corresponding vibration modes to guarantee a reliable coupled system for its long-term performance. These results may provide valuable references for the optimal design of medium-low speed maglev systems.

Self-excited Vibration Characteristics and Exciting Fluid Force of Multiple Plates Supported by Air Pressure

2020 ◽  
Vol 2020 (0) ◽  
pp. 610
Author(s):  
Shunsuke YAMAZAKI ◽  
Masakazu TAKEDA ◽  
Keiichi HIROAKI ◽  
Masahiro WATANABE
Keyword(s):  
Vibration Characteristics ◽  
Air Pressure ◽  
Fluid Force ◽  
Excited Vibration
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