Dynamic Stiffness and Damping Characteristics of Compensated Hydrostatic Thrust Bearings

1982 ◽  
Vol 104 (4) ◽  
pp. 491-496 ◽  
Author(s):  
M. K. Ghosh ◽  
B. C. Majumdar
Keyword(s):  
Load Capacity ◽  
Dynamic Stiffness ◽  
Fluid Inertia ◽  
Thrust Bearings ◽  
Continuity Equations ◽  
Damping Characteristics ◽  
Oil Flow ◽  
Stiffness And Damping ◽  
Compressibility Effects ◽  
Fluid Compressibility

This paper deals with an analysis of the dynamic behavior of compensated hydrostatic circular step thrust bearings taking into account fluid inertia and recess volume fluid compressibility effects. The Reynolds equation for fluid film and the recess flow continuity equations are linearized using perturbation methods. Results in terms of dimensionless load capacity, oil flow rate, stiffness, and damping are presented for capillary and orifice compensated bearings. Results show a marked influence of fluid inertia and recess volume fluid compressibility on the performance of the bearing.

Numerical analysis of the dynamic performance of aerostatic thrust bearings with different restrictors

2018 ◽  
Vol 233 (3) ◽  
pp. 406-423 ◽  
Author(s):  
Hailong Cui ◽  
Yang Wang ◽  
Xiaobin Yue ◽  
Yifei Li ◽  
Zhengyi Jiang
Keyword(s):  
Load Capacity ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Dynamic Mesh ◽  
Eccentricity Ratio ◽  
Thrust Bearings ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping ◽  
The Impact ◽  
The Relationship

This study utilizes a dynamic mesh technology to investigate the dynamic performance of aerostatic thrust bearings with orifice restrictor, multiple restrictors, and porous restrictor. An experiment, which investigates the bearing static load capacity, was carried out to verify the calculation accuracy of dynamic mesh technology. Further, the impact of incentive amplitude, incentive frequency, axial eccentricity ratio, and non-flatness on the bearing dynamic performance was also studied. The results show incentive amplitude effect can be ignored at the condition of amplitude less than 5% film thickness, while the relationship between dynamic characteristics and incentive frequency presented a strong nonlinear relationship in the whole frequency range. The change law of dynamic stiffness and damping coefficient for porous restrictor was quite different from orifice restrictor and multiple restrictors. The bearing dynamic performance increased significantly with the growth of axial eccentricity ratio, and the surface non-flatness enhanced dynamic performance of aerostatic thrust bearings.

Analysis of Static and Dynamic Characteristic of Hydrostatic Spherical Hinge

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Chundong Xu ◽  
Shuyun Jiang
Keyword(s):  
Power Loss ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Spherical Coordinate ◽  
Damping Coefficients ◽  
Oil Flow ◽  
New Perspective ◽  
Stiffness And Damping ◽  
Spherical Hinge ◽  
Rate Dynamic

A new hydrostatic spherical hinge is developed in this paper to provide a large load capacity. The static and dynamic Reynolds equations in spherical coordinate system for incompressible Newtonian fluid were established using the perturbation method. Finite difference method was employed to solve the load capacity, power loss, oil flow rate, dynamic stiffness, and damping coefficients. This paper provides a new perspective for analysis on the dynamic characteristics of the spherical hinge.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearing: Part 4 — Fitted Type of Bearings

Tribology ◽  
2006 ◽  
Author(s):  
A. W. Yacout ◽  
A. S. Ismaeel ◽  
S. Z. Kassab
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Major Effect ◽  
Design Parameters ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Spherical Bearing ◽  
Stiffness And Damping ◽  
Fluid Compressibility

Analytical solutions are not available for spherical bearing problems except for very specialized cases. However, this study offers a theoretical analysis, using the first order perturbations, to evaluate the frequency dependent stiffness and damping characteristics of compensated hydrostatic thrust spherical bearing including the surface roughness, the shaft rotation and the recess volume fluid compressibility effects. The dynamic stiffness and damping coefficients are presented for capillary tube and/or office compensated bearing. Results are obtained for various vibration frequencies or squeeze parameters (frequency parameters) and recess volume fluid compressibility parameters in addition to the other usual bearing design parameters. The study shows that both of the surface roughness and the centripetal inertia have slight effect on the stiffness and the damping coefficients while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

Modelling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications

1993 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Momentum Equation ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Radial Acceleration ◽  
Damping Characteristics ◽  
Energy Approximation ◽  
Form Model ◽  
Fluid Inertia Effect ◽  
Stiffness And Damping ◽  
Inertia Forces

Abstract It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartezian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.

scholarly journals Dynamic Stiffness and Damping Characteristics of a Shaft Damping Ring: A Combined Hyperelastic and Viscoelastic Constitutive Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Miaomiao Li ◽  
Jian Chen ◽  
Rupeng Zhu ◽  
Cheng Duan ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Constitutive Models ◽  
Operating Conditions ◽  
Uniaxial Tensile ◽  
Bending Vibrations ◽  
Damping Characteristics ◽  
Shaft System ◽  
Stiffness And Damping

At higher velocities, the helicopter tail transmission system encounters notable difficulties due to excessive bending vibrations. The shaft damping ring installed on the shaft system was shown to effectively suppress the shaft system vibrations. In this paper, the dynamic stiffness and damping characteristics of polyurethane shaft damping rings were studied using hyperelastic and viscoelastic constitutive models. The constitutive model and the damping ring material parameters were determined using uniaxial tensile and double-shear frequency scanning tests. Based on the test results, the dynamic damping ring characteristics were simulated and verified by dynamic stiffness tests; the influence of structural parameters and operating conditions on the dynamic stiffness and damping characteristics of the damping ring were obtained. The results provide a theoretical basis for the design of shaft systems with reduced sensitivity to vibrations.

scholarly journals Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing

2001 ◽  
Vol 44 (4) ◽  
pp. 657-663 ◽  
Author(s):  
Samuela Howard ◽  
Christopher Dellacorte ◽  
Mark J. Valco ◽  
Joseph M. Prahl ◽  
Hooshang Heshmat
Keyword(s):  
High Temperature ◽  
Journal Bearing ◽  
Dynamic Stiffness ◽  
Damping Characteristics ◽  
Stiffness And Damping

Dynamic Reynolds equation for micropolar fluids and the analysis of plane inclined slider bearings with squeezing effect

2007 ◽  
Vol 221 (7) ◽  
pp. 823-829 ◽  
Author(s):  
N. B. Naduvinamani ◽  
G. B. Marali
Keyword(s):  
Reynolds Equation ◽  
Coupling Parameter ◽  
Dynamic Stiffness ◽  
Closed Form Solution ◽  
Form Solution ◽  
Squeezing Effect ◽  
Micropolar Fluids ◽  
Slider Bearings ◽  
Damping Characteristics ◽  
Stiffness And Damping

The general dynamic Reynolds equation of sliding-squeezing surfaces with micro-polar fluids is derived for the assessment of dynamic characteristics of bearings with general film thickness. The detailed analysis is presented for the plane inclined slider bearings by using perturbation method. Two Reynolds-type equations corresponding to steady performance and perturbed characteristics are obtained. The closed form solution of these equations is obtained. The numerical computations of the results show that, the micropolar fluids provide an improved characteristics for both steady-state and the dynamic stiffness and damping characteristics. It is found that the maximum steady-load-carrying capacity is function of coupling parameter and is achieved at smaller values of profile parameter for larger values of the coupling parameter.

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