Closure to “Discussion of ‘Effects of Turbulence and Viscosity Variation on the Dynamic Coefficients of Fluid Film Journal Bearings’” (1985, ASME J. Tribol., 107, p. 261)

1985 ◽  
Vol 107 (2) ◽  
pp. 262-262
Author(s):  
D. F. Wilcock ◽  
O. Pinkus
Keyword(s):  
Journal Bearings ◽  
Fluid Film ◽  
Dynamic Coefficients ◽  
Viscosity Variation

Effects of Turbulence and Viscosity Variation on the Dynamic Coefficients of Fluid Film Journal Bearings

1985 ◽  
Vol 107 (2) ◽  
pp. 256-261 ◽  
Author(s):  
D. F. Wilcock ◽  
O. Pinkus
Keyword(s):  
High Speed ◽  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Fluid Film ◽  
Turbulent Regime ◽  
Dynamic Coefficients ◽  
Damping Characteristics ◽  
Fluid Film Bearings ◽  
Viscosity Variation ◽  
Stiffness And Damping

Many high-speed or large fluid film bearings operate in the turbulent regime. However, relatively little consideration has been given to the effects of turbulence and of the variation in viscosity on the dynamic stiffness and damping characteristics of the bearings. Since the dynamic behavior of the rotor supported on such bearings is often closely tied to the bearing dynamic coefficients, knowledge of them may be critical to both the design and the in-place correction of rotor instabilities. These effects are here considered in some detail on the basis of computer calculated analytical results, both in general dimensionless terms and with regard to a specific numerical example.

Theoretical Condition for the Cxy=Cyx Relation in Fluid Film Journal Bearings

1989 ◽  
Vol 111 (3) ◽  
pp. 426-429 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Finite Width ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Cross Terms ◽  
Linear Damping ◽  
Theoretical Condition

A computer program for calculating dynamic coefficients of journal bearings is necessary in designing fluid film journal bearings and an accuracy of the program is sometimes checked by the relation that the cross terms of linear damping coefficients of journal bearings are equal to each other, namely “Cxy = Cyx”. However, the condition for this relation has not been clear. This paper shows that the relation “Cxy = Cyx” holds in any type of finite width journal bearing when these are calculated under the following condition: (I) The governing Reynolds equation is linear in pressure or regarded as linear in numerical calculations; (II) Film thickness is given by h = c (1 + κcosθ); and (III) Boundary condition is homogeneous such as p=0 or dp/dn=0, where n denotes a normal to the boundary.

Influence of Fluid Film Boundary Migration on Dynamic Coefficients of Journal Bearings and Behavior of Rotor System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Zezeng Dai ◽  
Jianhua Cheng
Keyword(s):  
Journal Bearing ◽  
Boundary Migration ◽  
Dynamical Behavior ◽  
Journal Bearings ◽  
Rotor System ◽  
Fluid Film ◽  
Dynamic Coefficients ◽  
Film Boundary ◽  
Rotor Bearing ◽  
Stiffness And Damping

Abstract The position of fluid film in journal bearing will change while the journal moving in bearing, which can be named fluid film boundary migration (FFBM). It is usually ignored in the calculation of linear dynamic coefficients. While, the errors brought by this neglection was not ever investigated in detail. In this paper, the influence of FFBM on bearing dynamic coefficients and rotor system dynamic behaviors are investigated. A new perturbation-based model is proposed to take the FFBM into account by modifying the boundary conditions of governing equations. It is then verified by the experimental results and analytical results from previous research. Furthermore, the effects of FFBM on stiffness and damping in two typical journal bearings are investigated. The result indicates that the FFBM has a significant influence on dynamic coefficients of full circular journal bearing but little impact on journal bearing with axial grooves. Moreover, it affects the stiffness and damping more significantly in the cases of large length-to-diameter ratios or small eccentricity ratios in full circle bearing. Finally, the dynamical behavior of a rotor-bearing system with considering the FFBM is also investigated. The result shows that the FFBM of oil film has remarkable influences on the instability threshold and imbalance responses of the rotor system, which should not be ignored. The conclusions obtained in this research are expected to be helpful for the design of full circular journal bearings or rotor-bearing systems.

Review of the Concept of Dynamic Coefficients for Fluid Film Journal Bearings

1987 ◽  
Vol 109 (1) ◽  
pp. 37-41 ◽  
Author(s):  
J. W. Lund
Keyword(s):  
Rotor Dynamics ◽  
Journal Bearings ◽  
Fluid Film ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Unbalance Response

The development of the concept of spring and damping coefficients for journal bearings is briefly reviewed. Methods for computing the coefficients are described, and their use in rotor dynamics calculations (unbalance response, stability) is discussed. The limitations imposed by nonlinearities on the application of the coefficients is illustrated by examples.

An analytical study of the fluid film force in finite-length journal bearings. Part I

2001 ◽  
Vol 13 (4) ◽  
pp. 329-340 ◽  
Author(s):  
V. D'Agostino ◽  
D. Guida ◽  
A. Ruggiero ◽  
A. Senatore
Keyword(s):  
Finite Length ◽  
Analytical Study ◽  
Journal Bearings ◽  
Fluid Film
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