Numerical Investigation of Static and Dynamic Characteristics of Water Hydrostatic Porous Thrust Bearings

2011 ◽  
Vol 5 (6) ◽  
pp. 773-779 ◽  
Author(s):  
Yuki Nishitani ◽  
◽  
Shigeka Yoshimoto ◽  
Kei Somaya
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Measuring Equipment ◽  
Load Capacity ◽  
Damping Coefficient ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Hydrostatic Bearings ◽  
Aerostatic Bearings

A moving table supported by aerostatic bearings can achieve excellent accuracy of motion because of its noncontact support and, hence, it is used in various precision machine tools and measuring equipment. However, because of low viscosity of air, the damping coefficient of aerostatic bearings is not very high, causing vibration with nanometer-order amplitudes. The accuracy of machine tools and measuring equipment could deteriorate because of this vibration. It is expected that water hydrostatic bearings would have a higher damping coefficient than aerostatic bearings due to the higher viscosity of water. In addition, water, like air, does not pollute the environment. In this paper, the static and dynamic characteristics of water hydrostatic thrust bearings using porous material were numerically investigated and comparedwith conventional pocket hydrostatic bearings with a capillary restrictor. Hydrostatic porous bearings can be easily constructed because the porous material becomes a viscous restrictor itself. It was consequently found that water hydrostatic porous thrust bearings have higher maximum load capacity and slightly lower stiffness than water bearings with a capillary restrictor.

Static and Dynamic Characteristics of Aerostatic Circular Porous Thrust Bearings (Effect of the Shape of the Air Supply Area)

2000 ◽  
Vol 123 (3) ◽  
pp. 501-508 ◽  
Author(s):  
S. Yoshimoto ◽  
K. Kohno
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Thrust Bearing ◽  
Aerostatic Bearing ◽  
Bearing Surface ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Porous Bearing ◽  
Air Supply ◽  
Bearing Design

Recently, graphite porous material has been used successfully in an aerostatic bearing. In actual bearing design, it is often necessary to reduce the thickness of porous material to make the bearing smaller. However, a reduction in thickness results in a reduction in the strength of the porous material. In particular, when the diameter of porous material is large, it is difficult to supply the air through the full pad area of porous material because it deforms. Therefore, in this paper, two types of air supply method (the annular groove supply and the hole supply) in a circular aerostatic porous thrust bearing are proposed to avoid the deflection of the bearing surface. The static and dynamic characteristics of aerostatic porous bearing with these air supply methods are investigated theoretically and experimentally. In addition, the effects of a surface restricted layer on the characteristics are clarified.

scholarly journals Theoretical Efficiency Study of Output Lubricant Flow Rate Regulating Principle on the Example of a Two-Row Aerostatic Journal Bearing with Longitudinal Microgrooves and a System of External Combined Throttling

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1698
Author(s):  
Vladimir Kodnyanko ◽  
Stanislav Shatokhin ◽  
Andrey Kurzakov ◽  
Yuri Pikalov ◽  
Lilia Strok ◽  
...  
Keyword(s):  
Flow Rate ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Theoretical Study ◽  
Load Capacity ◽  
Finite Difference Methods ◽  
Output Flow ◽  
Aerostatic Bearings ◽  
Dynamic Quality ◽  
Active Flow

Due to their vanishingly low air friction, high wear resistance, and environmental friendliness, aerostatic bearings are used in machines, machine tools, and devices that require high accuracy of micro-movement and positioning. The characteristic disadvantages of aerostatic bearings are low load capacity, high compliance and an increased tendency for instability. In radial bearings, it is possible to use longitudinal microgrooves, which practically exclude circumferential air leakage, and contributes to a significant increase in load-bearing capacity. To reduce compliance to zero and negative values, inlet diaphragm and elastic airflow regulators are used. Active flow compensation is inextricably linked to the problem of ensuring the stability of bearings due to the presence of relatively large volumes of gas in the regulator, which have a destabilizing effect. This problem was solved by using an external combined throttling system. Bearings with input flow regulators have a number of disadvantages-they are very energy-intensive and have an insufficiently stable load capacity. A more promising way to reduce compliance is the use of displacement compensators for the movable element. Such bearings also allow for a decrease in compliance to zero and negative values, which makes it possible to use them not only as supports, but also as active deformation compensators of the technological system of machine tools in order to reduce the time and increase the accuracy of metalworking. The new idea of using active flow compensators is to regulate the flow rate not at the inlet, but at the outlet of the air flow. This design has the energy efficiency that is inherent to a conventional bearing, but the regulation of the lubricant output flow allows the compliance to be reduced to zero and negative values. This article discusses the results of a theoretical study of the static and dynamic characteristics of a two-row radial aerostatic bearing with longitudinal microgrooves and an output flow regulator. Mathematical modeling and theoretical study of stationary modes have been carried out. Formulas for determining static compliance and load capacity are obtained. Iterative finite-difference methods for determining the dynamic characteristics of a structure are proposed. The calculation of dynamic quality criteria was carried out on the basis of the method of rational interpolation of the bearing transfer function, as a system with distributed parameters, developed by the authors. It was found that the volumes of the microgrooves do not have a noticeable effect on the bearing dynamics. It is shown that, in this design, the external combined throttling system is an effective means of maintaining stability and high dynamic quality of the design operating in the modes of low, zero and negative compliance.

The Static and Dynamic Characteristics of the Spiral-Grooved Thrust Bearing

1965 ◽  
Vol 87 (3) ◽  
pp. 547-555 ◽  
Author(s):  
S. B. Malanoski ◽  
C. H. T. Pan
Keyword(s):  
Phase Angle ◽  
Dynamic Characteristics ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Radius Ratio ◽  
Oscillatory Motion ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Rotor Bearing ◽  
Oscillating Motion

A generalized analysis for spiral-grooved thrust bearings is presented. The effects of local radius are considered. For the same grooving geometry and the same inside-to-outside radius ratio, the inflow design is shown to be superior in both stiffness and load capacity. The analysis also treats a relative, transverse, oscillatory motion of the bearing surfaces. Both the magnitude and phase angle (in the temporal sense) of the bearing reaction are dependent on the frequency of the motion. The results for the oscillating motion reveal the possibility of a self-excited, rotor-bearing instability. The criterion for determining the onset of this type of instability is given.

Identification of Dynamic Characteristics of Gas Foil Thrust Bearings Using Base Excitation

2016 ◽  
Author(s):  
Tae Ho Kim ◽  
Moon Sung Park ◽  
Jongsung Lee ◽  
Young Min Kim ◽  
Kyoung-Ku Ha ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Loss Factor ◽  
Load Capacity ◽  
Excitation Frequency ◽  
Vibrational Amplitude ◽  
Test Rig ◽  
Thrust Bearings ◽  
Bearing Plate ◽  
Bearing Stiffness

Gas foil bearings (GFBs) have clear advantages over oil-lubricated and rolling element bearings, by virtue of low power loss, oil-free operation in compact units, and rotordynamic stability at high speeds. However, because of the inherent low gas viscosity, GFBs have lower load capacity than the other bearings. In particular, accurate measurement of load capacity and dynamic characteristics of gas foil thrust bearings (GFTBs) is utmost important to widening their applications to high performance turbomachinery. In this study, a series of excitation tests were performed on a small oil-free turbomachinery with base excitations in the rotor axial direction to measure the dynamic load characteristics of a pair of six-pad, bump-type GFTBs, which support the thrust collar. An electromagnetic shaker provided dynamic sine sweep loads to the test bench (shaking table), which held rigidly the turbomachinery test rig for increasing excitation frequency from 10 Hz to 200 Hz. The magnitude of the shaker dynamic load, represented as an acceleration measured on the test rig, was increased up to 9 G (gravity). An eddy current sensor installed on the test rig housing measured the axial displacement (or vibrational amplitude) of the rotor thrust collar during the excitation tests. The axial acceleration of the rotor relative to the test rig was calculated using the measured displacement. A single degree-of-freedom base excitation model identified the frequency-dependent dynamic load capacity, stiffness, damping, and loss factor of the test GFTB for increasing shaker dynamic loads and increasing bearing clearances. The test results show that, for a constant shaker force and the test GFTB with a clearance of 155 μm, an increasing excitation frequency increases the dynamic load carried by the test GFTB, i.e., bearing reaction force, until a certain value of the frequency where it jumps down suddenly because of the influence from Duffing’s vibrations of the rotor. The bearing stiffness increases and the damping decreases dramatically as the excitation frequency increases. Generally, the bearing loss factor ranges from 0.5 to 1.5 independent of the frequency. As the shaker force increases, the bearing dynamic load, stiffness, damping, and loss factor increase depending on the excitation frequency. Interestingly, the agreements between the measured GFTB dynamic load versus the thrust runner displacement, the measured GFTB static load versus the structural deflection, and the predicted static load versus the thrust runner displacement are remarkable. Further tests with increasing GFTB clearances of 155, 180, 205, and 225 μm revealed that the vibrational amplitude increases and the jump-down frequency decreases with increasing clearances. The bearing load increases, but the bearing stiffness, damping, and loss factor decrease slightly as the clearance increases. The test results after a modification of the GFTB by rotating one side bearing plate by 30° relative to the other side bearing plate revealed insignificant changes in the dynamic characteristics. The present dynamic performance measurements provide a useful database of GFTBs for use in microturbomachinery.

An Experimental Study of Static and Dynamic Characteristics of a 580mm(22.8in.) Diameter Direct Lubrication Tilting Pad Journal Bearing

2005 ◽  
Vol 128 (1) ◽  
pp. 146-154 ◽  
Author(s):  
Kazunori Ikeda ◽  
Toshio Hirano ◽  
Tatsuo Yamashita ◽  
Makoto Mikami ◽  
Hitoshi Sakakida
Keyword(s):  
Dynamic Characteristics ◽  
Large Scale ◽  
Load Capacity ◽  
Metal Temperature ◽  
Film Pressure ◽  
Static And Dynamic Characteristics ◽  
Oil Film ◽  
Analysis And Design ◽  
Tilting Pad ◽  
Oil Film Pressure

Direct lubrication tilting pad journal bearings (DLTPJ bearings) have rarely been applied to large-scale rotating machinery, such as turbines or generators, whose journal diameters are more than 500mm. In this paper, static and dynamic characteristics of a 580mm(22.8in.) diameter DLTPJ bearing were studied experimentally using a full-scale bearing test rig. In the static test, distribution of metal temperature, oil film pressure, and bearing loss were measured in changing oil flow rate, with mean bearing pressure ranging up to 2.9MPa. The maximum metal temperature of the DLTPJ bearing was compared to that of a conventional flood lubrication bearing, and it was confirmed that the direct lubrication could increase load capacity. In the dynamic test, spring and damping coefficients of oil film were obtained by exciting the bearing casing that was floated by air bellows. These data will be used for analysis and design of steam turbine rotors and their bearing systems. Also, vibration of pads was investigated because metal failure on upper pads due to vibration has been found in some actual machines. In order to generate oil film pressure on the surface of upper pads, a Rayleigh-step was machined there, and it was confirmed that vibration was reduced by the Rayleigh-step.

scholarly journals Experimental test of static and dynamic characteristics of tilting-pad thrust bearings

2015 ◽  
Vol 7 (7) ◽  
pp. 168781401559387 ◽  
Author(s):  
Annan Guo ◽  
Xiaojing Wang ◽  
Jian Jin ◽  
Diann Y Hua ◽  
Zikai Hua
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Test ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Tilting Pad

Performance Analysis of High Speed Floating Ring Hybrid Bearing in the Laminar and Turbulent Regimes

2011 ◽  
Vol 197-198 ◽  
pp. 1776-1780 ◽  
Author(s):  
Hong Guo ◽  
Bo Qian Xia ◽  
Shao Qi Cen
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Load Capacity ◽  
Flow Equation ◽  
The Finite Element Method ◽  
Static And Dynamic Characteristics ◽  
Hybrid Bearing

This paper presents a theoretical study concerning the static and dynamic characteristics of high speed journal floating ring hybrid bearing compensated by interior restrictor under laminar flow and turbulent flow respectively. The turbulent flow fluid film control equations and the pressure boundary conditions of this floating ring bearing together with the restrictor flow equation are solved by using the Finite Element Method. The variation regularity of static and dynamic characteristics such as load capacity, friction power loss, stiffness, damping etc. is analyzed. By comparing the laminar flow results and turbulent flow results, it is found that the characteristics coefficients are adjacent under small Reynolds number (laminar flow is dominant). But the characteristics coefficients are discrepant under big Reynolds number (turbulent flow is dominant). So turbulence lubrication theory is more accurate to high speed floating ring bearing.

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