Calculation of Static and Dynamic Characteristics of Multi Wounded Radial Foil Bearing Based on Leakage Flow Induced Vibration Theory

2006 ◽  
Author(s):  
Shigehiko Kaneko ◽  
Xiaoshan Wu
Keyword(s):  
Dynamic Characteristics ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Design Guidelines ◽  
Leakage Flow ◽  
Flow Induced Vibration ◽  
Static And Dynamic Characteristics ◽  
Foil Bearings ◽  
Vibration Theory ◽  
Foil Bearing

Dynamic pressure type foil bearings are expected to serve as shaft bearings for Micro Gas Turbines (MGT). In this study, in order to establish design guidelines of radial foil bearings, dynamical modeling of multi wounded foil bearing was carried out employing leakage flow induced vibration theory. Taking frictional forces due to attached part of the foil and the protrusion, etc. into consideration, static and dynamic characteristics were analyzed to examine the performance and the stability of radial foil bearings.

The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 3: Rotation in Foil Bearings of Reduced Length, With Starting and Stopping Unaided by External Pressurization

1972 ◽  
Vol 94 (3) ◽  
pp. 211-220 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Experimental Methods ◽  
Wear Characteristics ◽  
Foil Bearings ◽  
Foil Bearing

Experiments and analysis, reported in detail in references [1] through [5], demonstrated that high-speed rotors, supported by foil bearings, were free from whirl-instability and sensitivity to excitation at frequency equal one half the speed of rotation. It was shown also that the foil bearing could accommodate thermal and geometrical distortions, combining this attribute with excellent wipe-wear characteristics and tolerance of particles. The present investigation was directed toward the solution of two important problems: (a) the reduction of foil bearing length without detriment to rotor performance, and (b) the elimination of the foil-lift system and attainment of multiple start-stops without the aid of external pressurization. A description of experimental methods, which lead to the realization of the foregoing objectives, is given.

scholarly journals The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 2: Operation With Heating and Thermal Gradients

1970 ◽  
Vol 92 (4) ◽  
pp. 650-659 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Elevated Temperatures ◽  
Load Capacity ◽  
Temperature Gradients ◽  
Thermal Gradients ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Geometrical Imperfections ◽  
The Stability

A high-speed rotor, supported by gas-lubricated foil bearings, is free from self-excited whirl and displays no loss of load capacity when vibrated at frequency equal half the rotational speed [1]. It is demonstrated here that in addition to tolerance of geometrical imperfections, misalignment, and foreign particles [3, 4], the foil bearing performs well at elevated temperatures and accommodates appreciable temperature gradients. The foil bearing is endowed with superior wipe-wear characteristics, and the flexibility of the foil accounts not only for the stability of the foil bearing but also for its forgiveness with respect to distortion, contamination, and contact.

Performance of textured foil journal bearing considering the influence of relative texture depth

2022 ◽  
pp. 135065012110729
Author(s):  
Guanghui Zhang ◽  
Kefan Xu ◽  
Jiazhen Han ◽  
Yanzhong Huang ◽  
Wenjie Gong ◽  
...  
Keyword(s):  
Iterative Method ◽  
Dynamic Characteristics ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Surface Texturing ◽  
Static And Dynamic Characteristics ◽  
Foil Bearing ◽  
Newton Raphson ◽  
Maximum Increment

Both foil structure and surface texturing have been widely used to improve bearing performance. However, there is little research on their combination, namely, textured gas foil bearing. This paper adopts the Reynolds equation as the pressure governing equation of bump-type foil journal bearing to study the influence of textures located on the top foil. The Newton-Raphson iterative method and the perturbation method are employed to obtain static and dynamic characteristics, respectively. Thereafter, based on three texture distribution types, further analysis about the effect of the relative texture depth and the textured portion is carried out. The results indicate that an appropriate arrangement of textures could improve the performance of gas foil bearing. For #1 texture distribution, the maximum increment of load capacity could exceed 10% when ω  =  1.4 × 105 r/min, ε  =  0.2.

Test Results for the Static and Rotordynamic Characteristics of a Long (L/D = 0.75) Smooth Seal in Two-Phase (Mainly Gas) Conditions With a 62-Bar Inlet Pressure

2020 ◽  
Author(s):  
Dung L. Tran ◽  
Dara W. Childs ◽  
Hari Shrestha ◽  
Min Zhang
Keyword(s):  
Dynamic Characteristics ◽  
Gas Turbines ◽  
Flow Model ◽  
Dynamic Stiffness ◽  
Bulk Flow ◽  
Liquid Volume ◽  
Test Results ◽  
Two Phase ◽  
Static And Dynamic Characteristics ◽  
San Andres

Abstract Recent multiphase-pump developments encountered several rotordynamic issues with smooth balance-piston seals, creating a need to better understand the performance of annular seals under multiphase-flow operation. This paper presents measurements of static and dynamic characteristics of a long smooth seal (L/D = 0.75, D = 114.686 mm, and Cr = 0.200 mm) operating under pure- and mainly air condition in which air is mixed with silicone oil (PSF-5cSt). Tests are performed at a supply pressure of 62.1 bars-a, three rotation speeds (5, 10, 15 krpm), three pressure ratios (PRs) (0.6, 0.5, 0.4), for a range of inlet liquid volume fraction (LVFi) from 0% to 8%. The results are then compared to: (1) the previous test reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” J. Eng. Gas Turbines Power, 139(12), p. 122504) with similar testing condition but a different seal geometry (L/D = 0.65, D = 89.306 mm, and Cr = 0.188 mm) and (2) the predictions from a bulk-flow model developed by San Andrés (2012, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503). Results show a significant increase of direct dynamic stiffness KΩ as LVFi increases, especially at low PR. Test results reported by Zhang et al. (2017) has an opposite tendency of KΩ as an impact of increasing LVFi. Concerning cross-coupled dynamic stiffness kΩ and cross-coupled damping c, the results from Zhang et al. (2017) and the present results agree to the effects of changing speed, PR, and LVFi under pure- and mainly air conditions. As LVFi increases, direct damping C increases while test results reported by Zhang et al. (2017) showed no significant increase. Except for the direct dynamic stiffness and the impact of changing LVFi on the cross-coupled dynamic stiffness, the bulk-flow model of San Andrés (2012) predicts decently the tendencies and magnitudes of the rotordynamic coefficients.

Numerical and Experimental Analyses of Static and Dynamic Characteristics for Partially Helically Grooved Liquid Annular Seals

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Keisuke Nagai ◽  
Kazuki Koiso ◽  
Satoru Kaneko ◽  
Hiroo Taura ◽  
Yusuke Watanabe
Keyword(s):  
Flow Rate ◽  
Dynamic Characteristics ◽  
Smooth Surface ◽  
Reaction Force ◽  
Leakage Flow ◽  
Dynamic Reaction ◽  
Static And Dynamic Characteristics ◽  
Whirling Motion ◽  
Leakage Flow Rate ◽  
Experimental Analyses

Numerical and experimental analyses of the static and dynamic characteristics of the liquid annular seals with axially partial helical grooves were conducted to investigate the effects of the axial length gal of a helically grooved section in a seal stator. The numerical solution and experimental procedures were applied in the same manner as in previous studies on through-helically grooved seals, wherein the grooves extend across the seal length. The numerical results qualitatively agreed with the experimental results, demonstrating the validity of the numerical analysis. The leakage flow rate Q was lower in the partially helically grooved seals than that of conventional through-helically grooved seals across a small range of rotor spinning velocities. In contrast, the reduction in Q due to the pumping effect caused by the spin of the rotor diminished with the decrease in gal. For a small concentric whirling motion of the rotor, the radial dynamic reaction force Fr and magnitude of variation in the tangential dynamic reaction force Ft with the whirling angular velocity increased with the decrease in gal, and their values approached the corresponding values for the smooth-surface seal. Under the same rotor whirling velocity, the Ft for the partially helically grooved seals became lower than that for the smooth-surface seal (similar to the case for the through-helically grooved seal), although decreasing gal tended to increase Ft. These results suggest that partially helically grooved seals can improve the efficiency and stability margin of the pumps because of the reduction in leakage flow rate and suppression of the rotor forward whirling motion (with large radial and tangential dynamic reaction forces) as compared to conventional through-helically grooved seals.

On the Coupling of Foil Bearing Supported Rotors: Part 1 — Analysis

2007 ◽  
Author(s):  
Hooshang Heshmat ◽  
James F. Walton ◽  
Crystal A. Heshmat
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Ball Bearing ◽  
Dynamic Performance ◽  
Rotor Systems ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Flexible Rotors ◽  
Coupling Dynamic ◽  
Bearing System

The expanded application of high-speed rotor systems operating on compliant foil bearings will be greatly enhanced with the ability to adequately couple multiple shaft systems with differing bearing systems and dynamic performance. In this paper the results of an analytical tradeoff study assessing coupling dynamic characteristics and their impact on coupled rotor-bearing system dynamics are presented. This analysis effort was completed in an effort to establish the form of characteristics needed to couple foil bearing supported rotors to ball bearing supported rotors, other foil bearing supported rotors as well as coupling rigid and flexible rotors both supported on foil bearings. The conclusions from this study indicate that with appropriate coupling design, a wide array of foil bearing supported rotor systems may be successfully coupled.

Identification of Dynamic Characteristics of Hybrid Bump-Metal Mesh Foil Bearings

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Zilong Zhao ◽  
Kai Feng ◽  
Xueyuan Zhao ◽  
Wanhui Liu
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Load Test ◽  
Dynamic Force ◽  
Static Load Test ◽  
Metal Mesh ◽  
Force Coefficients ◽  
Foil Bearings ◽  
Foil Bearing

The stability of oil-free high-speed turbo-machinery can be effectively improved by increasing the damping characteristic of the gas foil bearing (GFB). Novel hybrid bump-metal mesh foil bearings (HB-MFBs) have been previously developed. Prior experimental results show that the parallel combination of bump structure and metal mesh not only can improve the structure stiffness but also provide better damping property compared with the bump-type foil structure. To investigate the dynamic behavior of floating HB-MFBs and promote its application, this study measured the dynamic force coefficients of HB-MFBs on a rotating test rig. The vibrations of HB-MFBs with different mesh densities (40%, 32.5%, and 25%) and a generation І bump-type foil bearing (BFB) with similar size are measured under static and impact loads to estimate the bearing characteristics. Static load test results show that the linear stiffness decreases when the air film is generated (from 0 rpm to 20 krpm) but increases gradually with speed (from 20 krpm to 30 krpm, and 40 krpm). Moreover, the dynamic force coefficients of HB-MFBs indicate the significant influence of metal mesh density on bearing dynamic characteristics. The growth in block density increases the dynamic stiffness and damping coefficients of bearing. The comparison of HB-MFB (32.5% and 40%) and BFB emphasizes the good damping characteristics of HB-MFB.

The influences of bump foil structure parameters on the static and dynamic characteristics of bump-type gas foil bearings

2020 ◽  
Vol 234 (10) ◽  
pp. 1642-1657
Author(s):  
Haojie Xu ◽  
Jiapeng Yang ◽  
Lei Gao ◽  
Qi An
Keyword(s):  
Dynamic Characteristics ◽  
Heat Dissipation ◽  
Thickness Distribution ◽  
Friction Torque ◽  
Foil Thickness ◽  
Deformation Model ◽  
Structure Parameters ◽  
Static And Dynamic Characteristics ◽  
Foil Bearing ◽  
Limiting Load

Bump-type gas foil bearing is a special type of sliding bearing, especially suitable for supporting rotors with light loads and high speeds. In this paper, a deformation model of bump foil is established by using elastic mechanics theory. A fluid-structure interaction algorithm is proposed according to Reynolds equation of compressible gas. On this basis, a method for calculating the static and dynamic characteristics of the bump-type gas foil bearing is established considering the structure parameters of the bump foil. The presented model is validated using the data reported in the existing research. The gas film pressure distribution, gas film thickness distribution of the bearing, and the influences of bump foil structure parameters on the static and dynamic characteristics of the bearing are studied with an example. Results show that, decreasing the bump foil thickness tB or increasing the bump pitch s will increase the limiting load-carrying capacity W and decrease the attitude angle β. And increasing tB or decreasing s will decrease the friction torque Tr and increase the side leakage flow of gas Qz, resulting in less friction heat generation and faster heat dissipation. Increasing tB or decreasing s will increase the absolute values of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] of the gas film, leading to higher equivalent stiffness of the gas film [Formula: see text].

Dynamic Characteristics of a High-Speed Rotor With Radial and Axial Foil-Bearing Supports

1981 ◽  
Vol 103 (3) ◽  
pp. 361-370 ◽  
Author(s):  
L. Licht ◽  
W. J. Anderson ◽  
S. W. Doroff
Keyword(s):  
Support System ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Journal Bearing ◽  
Foil Bearings ◽  
Flexible Support ◽  
Foil Bearing ◽  
Experimental Apparatus ◽  
Asymmetric Rotor

An asymmetric rotor (19N; 4.3 lb), supported radially and axially by compliant bearings (foil bearings), is subjected to severe excitation by rotating unbalance (43 μm.N; 6100 μin.oz) in the “pitching” mode, at speeds to 50,000 rpm. The resilient, air-lubricated bearings provide very effective damping, so that regions of resonance and instability can be traversed with impunity, with amplitudes and limit-trajectories remaining within acceptable bounds. A novel journal bearing is introduced, in which a resilient support is furnished by the outer turn of the coiled foil-element, initially bent to form an open polygon. The experimental apparatus and procedure are described, and the response of the rotor and flexible support system are copiously documented by oscilloscope records of motion.

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