Some Dynamic Properties of Oil-Film Journal Bearings With Reference to the Unbalance Vibration of Rotors

1956 ◽  
Vol 23 (2) ◽  
pp. 302-306
Author(s):  
A. C. Hagg ◽  
G. O. Sankey
Keyword(s):  
Dynamic Properties ◽  
Journal Bearings ◽  
Oil Film ◽  
Critical Speeds ◽  
Rotor Systems ◽  
Vibration Behavior ◽  
At Resonance ◽  
Oil Films

Abstract Some dynamic properties of oil films have been determined experimentally and their significance in the problem of unbalance vibration and critical speeds of rotor systems is illustrated by an example. It is shown that oil films have an important role in the imbalance-vibration behavior of rotor systems, particularly the vibration magnification at resonance.

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.

Hydrodynamic Journal Bearings Optimization Considering Rotor Dynamics Restrictions

2018 ◽  
Author(s):  
Leonid Moroz ◽  
Leonid Romanenko ◽  
Roman Kochurov ◽  
Evgen Kashtanov
Keyword(s):  
Film Thickness ◽  
Induction Motor ◽  
Rotor Dynamics ◽  
Journal Bearings ◽  
Oil Film ◽  
Critical Speeds ◽  
Bearing Clearance ◽  
Rotor Bearing ◽  
Dynamics Analyses ◽  
Bearing System

In this study, optimal designs of hydrodynamic journal bearings for 13.5 MW induction motor prototype is developed based on the design of experiment approach and best sequences method which involves entire rotor-bearing system multidisciplinary simulations. These simulations consist of bearing hydrodynamic characteristics calculation and optimization and rotor dynamics analyses for a rotor-bearing system. The results of rotor dynamics analyses are taken into account as the constraints during optimization. Several journal bearings such as plain cylindrical with a different configuration of pockets, elliptical type, and 4-lobe fixed pad have been considered to select the most appropriate design for the application. The bearing clearance, length, diameter, pockets positions, lobe width, oil viscosity, are applied as design input variables. To find the bearing optimal design, following objective functions were considered: 1) Minimum oil film thickness. Optimal bearing clearance is designed to produce the maximum possible level of minimum oil film thickness in order to avoid or reduce possible metal-to-metal contact; 2) Maximization of the performance is done by minimization of friction power loss. 3) Rotor dynamics simulation for the rotor-bearing system is embedded in the optimization process in order to avoid resonances by providing sufficient critical speeds separation margins from operating speed. The methodology for the bearing simulation is based on the mass-conserving mathematical model, proposed by Elrod & Adams and numerical solution for the equations is generated using finite difference method. Rotor dynamics analyses are performed using finite element method. As the result of the study, optimized bearing designs for 13.5 MW induction motor were generated. Optimized bearings provide sufficient frequency margins for critical speeds for the rotor-bearing system and, at the same time, improved hydrodynamic bearing characteristics: maximized oil film thickness and increased efficiency compared to the starting design. Through the considered bearings examples, the study shows how different parameters, such as bearing clearance, length, diameter, and etc., influence key performance characteristics like bearing minimum oil film thickness, friction power losses, rotor-bearing system critical speeds.

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.

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