scholarly journals Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent

2022 ◽  
Vol 12 (1) ◽  
pp. 485
Author(s):  
Xichun Liu ◽  
Wei Chen
Keyword(s):  
Liquid Metal ◽  
High Performance ◽  
Journal Bearing ◽  
Structural Parameters ◽  
Constant Width ◽  
Dynamic Performance ◽  
Helix Angle ◽  
Groove Depth ◽  
Journal Bearings ◽  
Design And Optimization

In order to improve the performance of the traditional constant-width herringbone grooved journal bearing in a computed tomography tube under a high-temperature environment, the present study designed a convergent herringbone grooved journal bearing (HGJB) structure lubricated by liquid metal. The bearing oil film thickness and the Reynolds equation considering the influence of turbulence are established and solved by using the finite difference method in the oblique coordinate system. The performance of the two bearings was compared, and the static and dynamic performance change trends of the two bearing structures under different eccentricities were systematically studied. The results show that the convergent herringbone grooved journal bearings are superior to the constant-width herringbone grooved journal bearings in terms of bearing capacity and stiffness coefficient. At the same time, the influence of structural parameters, such as the number of grooves, helix angle, groove to ridge ratio, groove depth on the performance of the constant-width herringbone grooved journal bearings, and the convergent herringbone grooved journal bearings was studied. Finally, we conclude that the performance of the convergent herringbone grooved journal bearings is optimal when the number of grooves is 15–20, the helix angle is 30–45°, the ratio of the groove to ridge is 1, and the groove depth is 0.02 mm −0.024 mm. This research has provided the thinking and reference basis for the design of liquid metal bearings for high-performance CT equipment.

A Review of Journal Bearing Induced Nonlinear Rotordynamic Vibrations

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Sitae Kim ◽  
Dongil Shin ◽  
Alan B. Palazzolo
Keyword(s):  
High Performance ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Thermally Induced ◽  
Frequency Domain Methods ◽  
Vibration Responses ◽  
Numerical Tools ◽  
Rotordynamic Forces ◽  
Solution Methodology

Abstract Nonlinear elements found in fluid film journal bearings and their surrounding structures are known to induce sub- and super-synchronous, chaos and thermally induced instability responses in rotor-bearing systems. The current review summarizes the literature on journal bearing induced nonlinear, rotordynamic forces, and responses. Nonlinear, thermo-elasto-hydrodynamic (TEHD) aspects of journal bearings has become increasingly important in high-performance turbomachines. These have significant influence on bearing dynamic performance and thermally induced, rotordynamic instability problems. Techniques for developing TEHD bearing models are discussed in the second section. Nonlinear solution methodology, including bifurcation determination and time and frequency domain methods such as harmonic balance, shooting and continuation, etc., is presented in the third section. Numerical tools to determine nonlinear vibration responses, including chaos, along with examples of bearing induced nonlinear vibrations are presented in the fourth and fifth sections, respectively.

Characteristics of Herringbone-Grooved, Gas-Lubricated Journal Bearings

1965 ◽  
Vol 87 (3) ◽  
pp. 568-576 ◽  
Author(s):  
J. H. Vohr ◽  
C. Y. Chow
Keyword(s):  
Differential Equation ◽  
Journal Bearing ◽  
Groove Depth ◽  
Radial Force ◽  
Journal Bearings ◽  
Speed Ratio ◽  
Plain Bearing ◽  
Relative Speed ◽  
Whirl Speed ◽  
Limiting Case

A differential equation is obtained for the smoothed “overall” pressure distribution around a herringbone-grooved, gas-lubricated journal bearing operating with a variable film thickness. The equation is based on the limiting case of an idealized bearing for which the number of grooves approaches an infinite number. A numerical solution to the differential equation is obtained valid for small eccentricities. This solution includes the case where the journal is undergoing steady circular whirl. In addition to the usual plain bearing parameters L/D, Λ, and whirl speed ratio ω3/(ω1 + ω2), the behavior of a grooved bearing also depends on four additional parameters: The groove angle β, the relative groove width α, the relative groove depth H0, and a compressibility number, Λs, which is based on the relative speed between the grooved and smooth members of the bearing. Results are presented showing bearing radial force and attitude angle as functions of β, α, H0, Λs, Λ, and whirl speed ratio.

scholarly journals On Error Torques of Squeeze-Film Cylindrical Journal Bearings

1968 ◽  
Vol 90 (1) ◽  
pp. 191-198
Author(s):  
C. H. T. Pan ◽  
T. Chiang
Keyword(s):  
Radial Displacement ◽  
High Performance ◽  
Journal Bearing ◽  
Rotational Symmetry ◽  
Mathematical Problem ◽  
Journal Bearings ◽  
Squeeze Film

The squeeze-film bearing has been considered for the output axis of high performance gyroscopes. Viewing this application, it is important that the parasitic torque of the bearing be very small. In the case of a squeeze-film journal bearing, parasitic torque can result from tolerance effects which disrupt rotational symmetry of the bearing. This problem has been studied by assuming ellipses for the tolerances of the journal and bearing surfaces as well as the squeeze motion, respectively. Each tolerance effect is assumed to be axially uniform. The mathematical problem is linearized with respect to each of the tolerances and the radial displacement of the journal. It was found that the parasitic torques do not depend on the radial displacement of the journal. The parasitic torques result from interactions among the three types of tolerance effects while each of the tolerances alone will not lead to any torque. Numerical estimates based on the geometry of a typical gyroscope and current fabrication practice shows such parasitic torques can seriously impair the accuracy of the gyroscope.

scholarly journals Advanced Classical Optical Filters with Three Waveguide Coupled Sagnac Loop Reflectors

2021 ◽  
Author(s):  
Hamed Arianfard ◽  
Jiayang Wu ◽  
Saulius Juodkazis ◽  
David Moss
Keyword(s):  
High Performance ◽  
Structural Parameters ◽  
Spectral Response ◽  
Optical Filters ◽  
Practical Applications ◽  
Design And Optimization ◽  
Fabrication Tolerances ◽  
Spectral Ranges ◽  
The Impact ◽  
Mode Interference

Abstract We theoretically investigate advanced multi-functional integrated photonic filters formed by three waveguide coupled Sagnac loop reflectors (3WC-SLRs). By tailoring the coherent mode interference, the spectral response of the 3WC-SLR resonators is engineered to achieve diverse filtering functions with high performance. These include optical analogues of Fano resonances that yield ultrahigh spectral extinction ratios (ERs) and slope rates, resonance mode splitting with high ERs and low free spectral ranges, and classical Butterworth, Bessel, Chebyshev, and elliptic filters. A detailed analysis of the impact of the structural parameters and fabrication tolerances is provided to facilitate device design and optimization. The requirements for practical applications are also considered. These results theoretically verify the effectiveness of using 3WC-SLR resonators as multi-functional integrated photonic filters for flexible spectral engineering in diverse applications.

Hydrodynamic Performance of Meso Scale Gas Journal Bearings

2004 ◽  
Author(s):  
Daejong Kim ◽  
Michael D. Bryant
Keyword(s):  
High Performance ◽  
Dynamic Performance ◽  
Laser Scanner ◽  
Journal Bearings ◽  
Hydrodynamic Performance ◽  
Gas Bearings ◽  
Rotor Mass ◽  
Very High ◽  
Meso Scale ◽  
Rarefaction Effects

Recent advancement of micro machining technology enabled a fabrication of micro scale gas bearings for high performance miniature scale rotating machinery. This paper presents recent development of micro gas bearings fabricated through X-ray lithography, and suggests fabrication method of various meso scale (~mm) gas journal bearings, which include Rayleigh step gas journal bearings, pressure dam bearings, grooved pressure dam bearings. Also presented are simulations performed using orbit method for the suggested meso scale gas bearings with diameter of 2mm, length of 2mm, and clearance of 1~2 micron. Pan’s first order slip model was adopted to simulate molecular rarefaction effects. The rotor mass was 0.3g, simulating very small Laser scanner unit. From the simulations, Rayleigh step journal bearing had highest threshold speed reaching 300,000 rpm. Effects of molecular rarefaction in sub micron bearing clearance on the dynamic performance at very high bearing numbers, were also investigated.

Identification of dynamic coefficients of the journal bearing considering velocity slip of cavitation zone in the rotating spindle unit

2018 ◽  
Vol 232 (10) ◽  
pp. 1304-1317
Author(s):  
Feng Cheng ◽  
Weixi Ji
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Velocity Slip ◽  
Journal Bearings ◽  
Identification Accuracy ◽  
Identification Algorithm ◽  
Dynamic Coefficients ◽  
Displacement Error ◽  
Spindle Unit ◽  
Cavitation Erosion Resistance

A rotating spindle unit, supported by the journal bearings, is developed to improve the cavitation erosion resistance of the journal bearing as well as the spindle dynamic performance. The turbulent lubrication model considering velocity slip in cavitation zone is derived, and the static and dynamic parameters of the journal bearing are obtained. An identification algorithm is further derivated to identify simultaneously the 16 dynamic coefficients of the two journal bearings in the spindle unit. The available experimental results reveal that the journal bearing coefficients are well predicted and estimated by the present model, and the estimated bearing parameters by regularization solution are in good agreement with the assumed values, while it has opposite effect by directed solution for discrete ill-posed problems. It is concluded that the identification accuracy of bearing parameters is governed by the displacement error, and the percentage deviation of dynamic coefficients decreases with the decrease of the displacement error.

The Rolling-Pad Journal Bearing: A Promising Antiwhirl Configuration

1981 ◽  
Vol 23 (3) ◽  
pp. 131-141
Author(s):  
M. Malik ◽  
R. Sinhasan ◽  
D. V. Singh
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Tilting Pad ◽  
The Comparative Study ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings ◽  
Theoretical Performance

The rolling-pad journal bearing is a kinematic variation of the well-known tilting-pad journal bearing. In rolling-pad bearings, the pads, instead of tilting about fixed pivots, roll at their back surfaces on the inside surface of a common sleeve to accommodate changes in the operating conditions of the bearing. This paper presents a comparison of the theoretical performance characteristics of rolling-pad journal bearings with those of tilting-pad journal bearings. The comparative study indicates that the dynamic performance characteristics of the rolling-pad bearing configuration are superior to those of the tilting-pad bearing.

scholarly journals Advanced Three Waveguide Sagnac Loop Reflectors for High Performance Optical Filters

2021 ◽  
Author(s):  
David Moss
Keyword(s):  
High Performance ◽  
Structural Parameters ◽  
Spectral Response ◽  
Optical Filters ◽  
Resonance Mode ◽  
Practical Applications ◽  
Design And Optimization ◽  
Mode Splitting ◽  
Fabrication Tolerances ◽  
Spectral Ranges

We theoretically investigate advanced multi-functionalintegrated photonic filters formed by three waveguide coupledSagnac loop reflectors (3WC-SLRs). By tailoring the coherentmode interference, the spectral response of the 3WC-SLRresonators is engineered to achieve diverse filtering functionswith high performance. These include optical analogues of Fanoresonances that yield ultrahigh spectral extinction ratios (ERs)and slope rates, resonance mode splitting with high ERs and lowfree spectral ranges, and classical Butterworth, Bessel,Chebyshev, and elliptic filters. A detailed analysis of the impactof the structural parameters and fabrication tolerances isprovided to facilitate device design and optimization. Therequirements for practical applications are also considered.These results theoretically verify the effectiveness of using 3WCSLRresonators as multi-functional integrated photonic filters forflexible spectral engineering in diverse applications.

Design and Test of Hydrostatic Gas Bearings for a Hybrid Cryogenic Refrigerator

2003 ◽  
Author(s):  
Jonathan C. Evans ◽  
Gregory F. Nellis
Keyword(s):  
Mass Flow ◽  
High Performance ◽  
Journal Bearing ◽  
High Reliability ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Pulse Tube ◽  
Gas Bearings ◽  
Lower Stage ◽  
Upper Stage

A hybrid pulse-tube/reverse-Brayton cryocooler is being developed that integrates a regenerative, pulse-tube upper stage with a recuperative, reverse-Brayton lower stage using a flow rectification system consisting of check-valves and buffer volumes. This system shows the potential for high performance with high reliability and low mass, and simple electrical, mechanical, and thermal integration. The turbine in the reverse-Brayton stage will be supported on hydrostatic gas bearings. The performance of the hybrid cryocooler system is strongly dependent upon the performance of these bearings; in particular their stiffness and mass flow consumption. This is a unique application of hydrostatic bearings; the miniature bearings are operating at cryogenic temperatures using high pressure helium. This paper describes the theoretical model that was developed to predict journal bearing performance as geometry and operating conditions change. The model is verified against experimental measurements of stiffness and mass flow consumption for a prototypical set of journal bearings. The model is subsequently used to optimize a set of journal bearings for the cryogenic turbine and parametrically investigate the effect of journal bearing clearance on system performance.

Combined Influence of Wear and Misalignment of Journal on the Performance Analysis of Three-Lobe Three-Pocket Hybrid Journal Bearing Compensated With Capillary Restrictor

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Satish C. Sharma ◽  
Vikas M. Phalle ◽  
S. C. Jain
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Fluid Film ◽  
Wear Depth ◽  
Fluid Film Thickness ◽  
Film Stiffness ◽  
Offset Factor ◽  
Bearing System

The multirecess noncircular hybrid journal bearings have been receiving wide importance in order to overcome the adverse effects on performance characteristics of multirecess circular journal bearings. During the lifetime of a machine, bearings are quite often required to be operated over a number of years and are subjected to several start and stop operations. As a consequence of this, the bush becomes progressively worn out and thereby changing the clearance space between journal and bearing. The present paper presents an analytical study investigating the effect of wear along with both aligned and misaligned conditions of journal on the performance of a capillary compensated three-lobe three-pocket hybrid journal bearing system for the various offset factors δ = 0.8,1.0, and 1.2. The wear caused on the bearing surface due to the transient (start/stop) operations has been modeled using Dufrane’s wear model. The modified Reynolds equation governing the flow of lubricant in the clearance space of a three-lobe multirecess worn hybrid journal bearing system along with both aligned and misaligned conditions of journal has been solved using an iterative scheme based on FEM. The influence of offset factor (δ), the wear depth parameter (δ¯w), and journal misalignment factors (σ¯,δ¯) on the performance of the three-lobe three-pocket hybrid journal bearing and three-pocket circular hybrid journal bearing system have been investigated. The results have been presented for the capillary compensated three-lobe three-pocket hybrid journal bearing system. The simulated results suggest that a bearing with a higher value of offset factor (δ>1) provides better static and dynamic performance characteristics as compared with a three-pocket circular journal bearing but the bearing with offset factor (δ < 1) is predominantly affected by the wear defect and misalignment of journal. The numerically simulated results suggest that the wear defect and offset factors significantly affect the bearing performance. Therefore, it becomes imperative to account for the influence of wear and offset factors during the design process so as to generate accurate data of bearing performance. The numerically simulated results have been presented in terms of maximum fluid-film pressure, minimum fluid-film thickness, lubricant flow rate, direct fluid-film stiffness, damping coefficients, and stability threshold speed margin. The present study demonstrates that the performance of bearing is significantly affected by wear along with both aligned and misaligned conditions of journal and the loss is partially compensated by keeping the offset factor δ>1.

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