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.

Effect of Scratches on a Tilting-Pad Journal Bearing

2020 ◽  
Author(s):  
Steven Chatterton ◽  
Paolo Pennacchi ◽  
Andrea Vania ◽  
Mohamed Amine Hassini ◽  
Antoine Kuczkowiak
Keyword(s):  
Film Thickness ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Hydrodynamic Performance ◽  
Axial Position ◽  
Steam Turbines ◽  
Local Pressure ◽  
Oil Film ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

Abstract Many industrial rotating machines are equipped with hydrodynamic journal bearings, such as centrifugal compressors, steam turbines, pumps and motors. After some time from the installation, however, the surface of the bearings often presents imperfections and slight damages mainly caused by the presence of harder particles in the lubricant during start-ups and shut-downs, when the hydrodynamic mechanism is not well developed and the mixed lubrication can occur. The presence of scratches on a bearing can lead to variations of the oil film thickness which, in turn, causes significant degradation of the bearing hydrodynamic performance. For example, the reduction of the minimum oil-film thickness can lead to the increase in the local temperature, to local pressure peaks and, finally, to the failure of the bearing. Experimental data relating to scratches on journal bearings are extremely limited in the literature especially for tilting-pad journal bearings (TPJBs). An experimental activity was carried out to study the effect of artificial scratches on pads on the static and dynamic behaviors of a TPJB. The number of scratches, the depth and the axial position have been investigated and the dynamic coefficients have been estimated as well. The experimental results confirmed a degradation of the dynamic performance of the bearing in case of scratches, that it has has been also confirmed by means of numerical simulations.

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.

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.

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.

KEMPER C688

Alloy Digest ◽  
2017 ◽  
Vol 66 (12) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Copper Alloy ◽  
High Performance ◽  
High Conductivity ◽  
Bend Strength ◽  
Very High

Abstract Alloy C688 is a high-performance copper alloy with very high conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming and joining. Filing Code: Cu-867. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

KEMPER KHP7025

Alloy Digest ◽  
2017 ◽  
Vol 66 (10) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Copper Alloy ◽  
High Performance ◽  
High Conductivity ◽  
Bend Strength ◽  
Very High

Abstract Alloy KHP 7025 (UNS C70250) is a high-performance copper alloy with very high conductivity. Uses include connector springs, tabs, contact springs, switches, relays, and leadframes. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming, machining, and joining. Filing Code: Cu-865. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

Use of activated carbon to remove undesirable residual amylase from refinery streams

2017 ◽  
pp. 96-103 ◽  
Author(s):  
Gillian Eggleston ◽  
Isabel Lima ◽  
Emmanuel Sarir ◽  
Jack Thompson ◽  
John Zatlokovicz ◽  
...  
Keyword(s):  
Activated Carbon ◽  
High Temperature ◽  
High Performance ◽  
Activated Carbons ◽  
Amylase Activity ◽  
Sugar Industry ◽  
End User ◽  
Customer Complaints ◽  
Carry Over ◽  
Very High

In recent years, there has been increased world-wide concern over residual (carry-over) activity of mostly high temperature (HT) and very high temperature (VHT) stable amylases in white, refined sugars from refineries to various food and end-user industries. HT and VHT stable amylases were developed for much larger markets than the sugar industry with harsher processing conditions. There is an urgent need in the sugar industry to be able to remove or inactivate residual, active amylases either in factory or refinery streams or both. A survey of refineries that used amylase and had activated carbon systems for decolorizing, revealed they did not have any customer complaints for residual amylase. The use of high performance activated carbons to remove residual amylase activity was investigated using a Phadebas® method created for the sugar industry to measure residual amylase in syrups. Ability to remove residual amylase protein was dependent on the surface area of the powdered activated carbons as well as mixing (retention) time. The activated carbon also had the additional benefit of removing color and insoluble starch.

scholarly journals Numerical Investigation on Hydrodynamic Performance of a Portable AUV

2021 ◽  
Vol 9 (8) ◽  
pp. 812
Author(s):  
Lin Hong ◽  
Renjie Fang ◽  
Xiaotian Cai ◽  
Xin Wang
Keyword(s):  
Numerical Investigation ◽  
Dynamic Model ◽  
Autonomous Underwater Vehicle ◽  
Dynamic Performance ◽  
Plane Motion ◽  
Hydrodynamic Performance ◽  
Wave Forces ◽  
Modeling And Control ◽  
Experiment Platform ◽  
Cfd Method

This paper conducts a numerical investigation on the hydrodynamic performance of a portable autonomous underwater vehicle (AUV). The portable AUV is designed to cruise and perform some tasks autonomously in the underwater world. However, its dynamic performance is strongly affected by hydrodynamic effects. Therefore, it is crucial to investigate the hydrodynamic performance of the portable AUV for its accurate dynamic modeling and control. In this work, based on the designed portable AUV, a comprehensive hydrodynamic performance investigation was conducted by adopting the computational fluid dynamics (CFD) method. Firstly, the mechanical structure of the portable AUV was briefly introduced, and the dynamic model of the AUV, including the hydrodynamic term, was established. Then, the unknown hydrodynamic coefficients in the dynamic model were estimated through the towing experiment and the plane-motion-mechanism (PMM) experiment simulation. In addition, considering that the portable AUV was affected by wave forces when cruising near the water surface, the influence of surface waves on the hydrodynamic performance of the AUV under different wave conditions and submerged depths was analyzed. Finally, the effectiveness of our method was verified by experiments on the standard models, and a physical experiment platform was built in this work to facilitate hydrodynamic performance investigations of some portable small-size AUVs.

Machine learning-based performance analysis of two-axial-groove hydrodynamic journal bearings

2021 ◽  
pp. 135065012199289
Author(s):  
Biswajit Roy ◽  
Sudip Dey
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Hydrodynamic Performance ◽  
Support Vector ◽  
Oil Viscosity ◽  
Hydrodynamic Analysis ◽  
Supply Pressure ◽  
Input Parameters ◽  
Precise Prediction ◽  
Output Behavior

The precise prediction of a rotor against instability is needed for avoiding the degradation or failure of the system’s performance due to the parametric variabilities of a bearing system. In general, the design of the journal bearing is framed based on the deterministic theoretical analysis. To map the precise prediction of hydrodynamic performance, it is needed to include the uncertain effect of input parameters on the output behavior of the journal bearing. This paper presents the uncertain hydrodynamic analysis of a two-axial-groove journal bearing including randomness in bearing oil viscosity and supply pressure. To simulate the uncertainty in the input parameters, the Monte Carlo simulation is carried out. A support vector machine is employed as a metamodel to increase the computational efficiency. Both individual and compound effects of uncertainties in the input parameters are studied to quantify their effect on the steady-state and dynamic characteristics of the bearing.

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