Experimental Research Regarding the Influence of Pocket Pressure Values on the Stiffness of Hydrostatic Guideways

2014 ◽  
Vol 657 ◽  
pp. 544-548
Author(s):  
Marius Pascu ◽  
Gheorghe Stan
Keyword(s):  
Film Thickness ◽  
Hydraulic Resistance ◽  
Experimental Research ◽  
Load Capacity ◽  
New Method ◽  
Important Criterion ◽  
Supply Pressure ◽  
High Stiffness ◽  
Very High

A very important parameter which must be considered when designing a hydrostatic guideway of high stiffness is the pressure from the hydrostatic pockets. Modifications of this parameter during functioning are caused by variations of flow and supply pressure and also by the defective geometry of the hydrostatic pockets. The pocket pressure has a major importance for achieving the hydraulic sustentation, because it determines the load capacity, which thenceforth determines the film thickness and the flow. The latter is used for determining the hydraulic resistance of lands and also for deciding the geometry of the hydrostatic guideway as a whole. Based on these considerations, the analysis of the pocket pressure variations represents an important criterion which should be taken into account when designing a hydrostatic guideway with a very high stiffness. The present paper contains a new method for analysing the hydrostatic guideway behaviour with regard to its stiffness, for different pocket pressure values. The experimental research was carried out on a closed hydrostatic guideway, with the moving element having the dimensions of 500x260 [m and the pocket dimensions of 150x88 [m.

Theoretical Research on Aerostatic Rectangular Guideways with Finite Difference Method

2007 ◽  
Vol 339 ◽  
pp. 371-376 ◽  
Author(s):  
Xiao Feng Zhang ◽  
Bin Lin
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Difference Method ◽  
Load Capacity ◽  
Theoretical Research ◽  
Orifice Diameter ◽  
Supply Pressure ◽  
Design And Manufacture

The load capacity and stiffness of the aerostatic rectangular guideways, which apply annular orifice restrictor and porous restrictor respectively, were analyzed with finite difference method in this paper. A program for solving the pressure distribution, load capacity and stiffness is programmed with VB. The calculated results show that the rise of supply pressure is good for improving the load capacity and stiffness of guideways. The decrease of the orifice diameter in annular orifice restriction and the permeability in porous restriction is advantageous to improve the stiffness of guideways, but both the corresponding bearing clearance and load capacity decrease. In both the annular restriction and porous restriction, the best film thickness which make the stiffness maximum exists under the definite supply pressure and parameter of the restrictor. Under the same supply pressure, the load capacity and stiffness of porous restriction is higher than the orifice restriction. Meanwhile, the design and manufacture of porous restrictor is simple. The porous restrictor is the perfect restrictor of aerostatic guideways.

scholarly journals Rational Design and Porosity of Porous Alumina Ceramic Membrane for Air Bearing

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 872
Author(s):  
Jianzhou Du ◽  
Duomei Ai ◽  
Xin Xiao ◽  
Jiming Song ◽  
Yunping Li ◽  
...  
Keyword(s):  
Film Thickness ◽  
Ceramic Membrane ◽  
Load Capacity ◽  
Porous Alumina ◽  
Ceramic Membranes ◽  
Alumina Ceramic ◽  
Air Bearing ◽  
Supply Pressure ◽  
Simulation Results ◽  
Gas Supply

Air bearing has been widely applied in ultra-precision machine tools, aerospace and other fields. The restrictor of the porous material is the key component in air bearings, but its performance is limited by the machining accuracy. A combination of optimization design and material modification of the porous alumina ceramic membrane is proposed to improve performance within an air bearing. Porous alumina ceramics were prepared by adding a pore-forming agent and performing solid-phase sintering at 1600 °C for 3 h, using 95-Al2O3 as raw material and polystyrene microspheres with different particle sizes as the pore-forming agent. With 20 wt.% of PS50, the optimum porous alumina ceramic membranes achieved a density of 3.2 g/cm3, a porosity of 11.8% and a bending strength of 150.4 MPa. Then, the sintered samples were processed into restrictors with a diameter of 40 mm and a thickness of 5 mm. After the restrictors were bonded to aluminum shells for the air bearing, both experimental and simulation work was carried out to verify the designed air bearing. Simulation results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25% at a fixed gas supply pressure of 0.5 MPa and a fixed gas film thickness of 25 μm. When the gas film thickness and porosity were fixed at 100 μm and 11.8%, respectively, the load capacity increased from 8.6 N to 40.8 N with the gas supply pressure having been increased from 0.1 MPa to 0.5 MPa. Both experimental and simulation results successfully demonstrated the stability and effectiveness of the proposed method. The porosity is an important factor for improving the performance of an air bearing, and it can be optimized to enhance the bearing’s stability and load capacity.

scholarly journals Stellar magnetic imaging from spectropolarimetric data

1996 ◽  
Vol 176 ◽  
pp. 53-60 ◽  
Author(s):  
J.-F. Donati
Keyword(s):  
Small Amplitude ◽  
High Accuracy ◽  
Spectral Lines ◽  
New Method ◽  
Doppler Imaging ◽  
Magnetic Imaging ◽  
Active Stars ◽  
Surface Fields ◽  
Very High

In this paper, I will review the capabilities of magnetic imaging (also called Zeeman-Doppler imaging) to reconstruct spot distributions of surface fields from sets of rotationnally modulated Zeeman signatures in circularly polarised spectral lines. I will then outline a new method to measure small amplitude magnetic signals (typically 0.1% for cool active stars) with very high accuracy. Finally, I will present and comment new magnetic images reconstructed from data collected in 1993 December at the Anglo-Australian Telescope (AAT).

scholarly journals A New Method to Calculate Water Film Stiffness and Damping for Water Lubricated Bearing with Multiple Axial Grooves

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Guojun Ren
Keyword(s):  
Analytical Procedure ◽  
Load Capacity ◽  
Water Film ◽  
New Method ◽  
Hard Materials ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Hydro Turbines

Abstract Water lubricated guide bearings for hydro turbines and pumps are conventionally designed with multiple axial grooves to provide effectively cooling and flushing away abrasives. Due to the variety of groove configuration in terms of number and size, a predication of their performance is difficult. This paper deals with an analytical procedure to investigate groove effect on load capacity, stiffness and damping for this type of bearing where it is considered as an assembly of many inclined slide bearings. The result can be applied to bearings made of hard materials combined with low bearing pressure.

scholarly journals Effective Method for Diagnosing Continuous Welded Track Condition Based on Experimental Research

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2889
Author(s):  
Jacek Kukulski ◽  
Piotr Gołębiowski ◽  
Jacek Makowski ◽  
Ilona Jacyna-Gołda ◽  
Jolanta Żak
Keyword(s):  
Experimental Research ◽  
Thermal Stresses ◽  
Longitudinal Force ◽  
Climatic Conditions ◽  
Traffic Load ◽  
Empirical Formulas ◽  
Correct Operation ◽  
Temperature Changes ◽  
Track Condition ◽  
Very High

The correct operation of the continuous welded track requires diagnosing its condition and preparation of track metrics requiring measurements of displacements of rail under operation. This is required as there are additional thermal stresses in the rails with values depending on the temperature changes of the rails. Therefore, the climatic conditions are important. This paper presents the original effective analytical method for diagnosing the condition of continuous welded track based on experimental research. The method allows for an appropriate repair or maintenance recommendation. In the experimental research, the authors considered track diagnostic conditions for two conditions: track under load and track without load. This paper presents empirical formulas for calculating rail temperature and longitudinal force based on ambient temperature, developed from long-term measurements. The formulas were developed for a track located on a straight section—both for a rail loaded and unloaded with a passing train under the following conditions: 60E1 rail, not on an engineering structure, conventional surface, wooden sleepers and very high train traffic load. The obtained results in the value of the correlation coefficient R2 ≥ 0.995 attest to very high accuracy of the calculations performed with the method proposed by the authors.

Influencing Factors on Dynamic Response of Hydrostatic Guideways

2011 ◽  
Vol 418-420 ◽  
pp. 2095-2101 ◽  
Author(s):  
Zhi Wei Wang ◽  
Wan Hua Zhao ◽  
Bing Heng Lu
Keyword(s):  
Film Thickness ◽  
Damping Ratio ◽  
Pressure Ratio ◽  
Settling Time ◽  
Lubricating Oil ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
Maximum Value ◽  
Small Perturbation Method ◽  
Stiffness And Damping

Stiffness and damping of hydrostatic guideways are calculated by small perturbation method based on Reynolds equation in dynamic regime. The hydrostatic guideway is considered as a system which consists of the mass, the spring and the damper. The effects of some main parameters on stiffness, damping and damping ratio are analyzed which include the supply pressure, the film thickness, the pad dimension, the pressure ratio, the lubricating oil volume and the lubricating oil viscosity. The relationships between the settling time of the hydrostatic guideways and these parameters are investigated under a step load. It is shown that the slide block returns to equilibrium without overshooting under a step load, and the amplitude of the block vibration has not a maximum value under a cyclic load, due to the large damping effect( ξ>1). In addition, the settling time can be shorten with the increase of the supply pressure, the film thickness and the lubricating oil volume, and also with the decrease of the pressure ratio and the lubricating oil viscosity. The settling time get the shortest value when recess parameter( α) is 0.55.

Improved Method Based on Fluid Mechanics Analysis for Buoy Gauge Design and Experimental Research

2012 ◽  
Vol 163 ◽  
pp. 133-137
Author(s):  
Ao Yu Chen ◽  
Xu Dong Pan ◽  
Guang Lin Wang
Keyword(s):  
Fluid Mechanics ◽  
Experimental Research ◽  
Traditional Method ◽  
New Method ◽  
Improved Method ◽  
Advanced Method ◽  
Inner Surface ◽  
Mechanics Analysis ◽  
Linear Property

Traditional method of buoy gauge design is rather complicated, so an advanced method by building and solving fluid mechanics equations is proposed in this paper. The curve of the taper pipe inner surface is calculated, according to different buoy gravity and diameter. In order to examine the effect of this improved method, an experiment is carried out. Results show that linear property of the buoy gauge improved by new method is excellent.

An Accurate Solution of the Gas Lubricated, Flat Sector Thrust Bearing

1977 ◽  
Vol 99 (1) ◽  
pp. 82-88 ◽  
Author(s):  
I. Etsion ◽  
D. P. Fleming
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Thickness Distribution ◽  
Maximum Load ◽  
Accurate Solution ◽  
Operating Conditions ◽  
Thrust Bearings ◽  
Practical Design ◽  
Minimum Film Thickness

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

Experimental Research on Cavitation Characteristics of a Novel Hybrid Journal Bearing

2013 ◽  
Vol 420 ◽  
pp. 74-77
Author(s):  
Ying Yang ◽  
Jing Hua Dai ◽  
Xu Li
Keyword(s):  
Experimental Research ◽  
High Speed ◽  
Work Performance ◽  
Journal Bearing ◽  
Rupture Zone ◽  
Oil Film ◽  
Rotating Speed ◽  
Supply Pressure ◽  
Experimental Rig

Under high and super high speed, the oil film of a journal bearing is easy to crack and then becomes cavitation. The existence of cavitation has a great effect on the work performance of the bearing. The cavitation mechanism of a spiral oil wedge journal bearing was investigated on the experimental rig. The effects of rotating speed and supply pressure on the cavitation shape of oil film and the number of cavitation strip in the rupture zone were analyzed. The results show that the cavitation shape of oil film is a long strip. The number of cavitation strip increases when supply pressure has been improved, and the location of oil outlet must be designed optimally.

Static Characteristics of Gas Foil Thrust Bearing Based on Gas Rarefaction Model

2015 ◽  
Author(s):  
Jiajia Yan ◽  
Guanghui Zhang ◽  
Zhansheng Liu ◽  
Fan Yang
Keyword(s):  
Film Thickness ◽  
Optimization Design ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Rarefied Gas ◽  
Load Capacity ◽  
Structural Parameters ◽  
Lubricating Film ◽  
Lift Off ◽  
Foil Thrust Bearing

A modified Reynolds equation for bump type gas foil thrust bearing was established with consideration of the gas rarefaction coefficient. Under rarefied gas lubrication, the Knudsen number which was affected by the film thickness and pressure was introduced to the Reynolds equation. The coupled modified Reynolds and lubricating film thickness equations were solved using Newton-Raphson Iterative Method and Finite Difference Method. By calculating the load capacity for increasing rotor speeds, the lift-off speed under certain static load was obtained. Parametric studies for a series of structural parameters and assembled clearances were carried out for bearing optimization design. The results indicate that with gas rarefaction effect, the axial load capacity would be decreased, and the lift-off speed would be improved. The rarefied gas has a more remarkable impact under a lower rotating speed and a smaller foil compliance coefficient. When the assembled clearance of the thrust bearing rotor system lies in a small value, the lift-off speed increases dramatically as the assembled clearance decreases further. Therefore, the axial clearance should be controlled carefully in assembling the foil thrust bearing. It’s worth noting that the linear uniform bump foil stiffness model is not exact for large foil compliance ∼0.5, especially for lift-off speed analysis, due to ignoring the interaction between bumps and bending stiffness of the foil.

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