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.

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.

Vibration Analysis of the Self-Excited Vibration in the Rotor System Due to Ball Balancer

2009 ◽  
Author(s):  
Tsuyoshi Inoue ◽  
Hideaki Niimi ◽  
Yukio Ishida
Keyword(s):  
Vibration Suppression ◽  
Rotor System ◽  
The Self ◽  
Excited Vibration ◽  
Amplitude Vibration ◽  
Speed Range ◽  
Large Amplitude Vibration ◽  
Fundamental Equations ◽  
Ball Mass ◽  
Ball Motion

The ball balancer has been used as the vibration suppression device in rotor system. It has a superior characteristic that the vibration amplitude is reduced to zero at the rotational speed range higher than the major critical speed. However, the ball balancer may cause a self-excited vibration when the balls rotate in the balancer, and this self-excited vibration results in the large amplitude vibration. In this paper, the occurrence region and vibration characteristics of the self-excited vibration are investigated. The theoretical analysis is performed and a set of the fundamental equations governing the self-excited vibration is obtained. The influences of the parameters, such as, damping of the ball motion, ball mass, and radius of the ball orbit are explained. As the result, it is shown that the damping of the ball motion and the ball mass have the effect on decreasing the occurrence region of the self-excited vibration.

Rotor Stability Evaluation for High Pressure Multi-Stage Pump by Excitation Diagnosis Method

2017 ◽  
Author(s):  
Shichao Peng ◽  
Akira Arai ◽  
Takaki Fukuchi ◽  
Taiju Katayama ◽  
Osami Matsushita
Keyword(s):  
High Pressure ◽  
Rotor System ◽  
The Self ◽  
System Stability ◽  
Circumferential Velocity ◽  
High Rotational Speed ◽  
Multi Stage ◽  
Excited Vibration ◽  
Annular Seal ◽  
Water Test

High pressure multi-stage pump is one of the most important machinery in various plants. Due to the high rotational speed, there are cases where excessive vibration problems occur. Especially, the self-excited vibration arises from the fluid force, which exists within the clearance of the oil film bearings and balancing drum (annular seal). In order to evaluate the rotor system stability, we developed an excitation method based on Bently-Muszynska model, and applied this method to the air test and water test. Through the test results, the onset (threshold) of instability (self-excited vibration) can be evaluated by the rotor system natural frequency and the fluid average angular circumferential velocity within the clearance of the bearings and balancing drum. Moreover, the balancing drum had a significant effect on the rotor stability, and the resulting frequency of the self-excited vibration matched the fluid average angular circumferential velocity in the balancing drum.

Self-Excited Vibration of a Rotating Hollow Shaft Partially Filled with Liquid

1980 ◽  
Vol 102 (1) ◽  
pp. 185-192 ◽  
Author(s):  
S. Saito ◽  
T. Someya
Keyword(s):  
Viscous Liquid ◽  
Rotor System ◽  
The Self ◽  
Hollow Shaft ◽  
Excited Vibration ◽  
Negative Damping ◽  
The Stability

The self-excited vibration of a rotating hollow shaft partially filled with viscous liquid is investigated. The motion of liquid and the liquid force is analyzed. The stability of the rotor system is calculated and the influences of factors on the stability are studied. Moreover, the mechanism causing the negative damping which is the reason for the instability is discussed.

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.

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