Numerical Investigations of Various Surface Roughness Parameters on the Performance of Profiled Hydrostatic Thrust Bearing

2005 ◽  
Author(s):  
Kirat Shah ◽  
Robert E. Johnson ◽  
Harish P. Cherukuri
Keyword(s):  
Surface Roughness ◽  
Thrust Bearings ◽  
Lubrication Equation ◽  
Load Carrying ◽  
Minimum Film Thickness ◽  
Order Of Magnitude ◽  
Auto Correlation Function ◽  
Non Gaussian ◽  
Gaussian Surface ◽  
Lubrication Conditions

Measurements of surface roughness on hydrostatic bearing slipper indicate that the surfaces are not always Gaussian. Previous studies in this area were primarily concerned with Gaussian surfaces. In this research the effects of non-Gaussian surface roughness on the performance of profiled hydrostatic thrust bearings are analyzed. This study is applicable to the lubrication conditions where the surface roughness is of the same order of magnitude as the minimum film thickness. Surfaces with different skewness, kurtosis, mean, auto-correlation function and standard deviation are generated numerically using a combination of Fast Fourier Transform (FFT) and Johnson translatory system. The finite difference method is used to solve the Reynolds lubrication equation. The effect of roughness on the load carrying capacity is investigated and compared with the results for ideal smooth surfaces.

Influence of new surface micro-structures on the performance behaviours of fluid film tilting pad thrust bearings

2021 ◽  
pp. 095440622110309
Author(s):  
JC Atwal ◽  
RK Pandey
Keyword(s):  
Mass Conservation ◽  
Performance Parameters ◽  
Algebraic Equations ◽  
The Finite Element Method ◽  
Thrust Bearings ◽  
Lubrication Equation ◽  
Tilting Pad ◽  
Minimum Film Thickness ◽  
Newton Raphson ◽  
Micro Structures

Performance parameters such as power loss, minimum film thickness, and maximum oil temperature of the sector-shaped tilting pad thrust bearings employing the new micro-structural geometries on pad surfaces have been investigated. The lubrication equation incorporating the mass-conservation issue is discretized using the finite element method and the solution of resulting algebraic equations is obtained employing a Newton-Schur method. The pad equilibrium in the analysis is established using the Newton-Raphson and Braydon methods. The influence of attributes of micro-structures such as depth, circumferential and radial positioning extents have been explored on the performance behaviours. It is found that with the new micro-structured pad surfaces, the performance parameters significantly improved in comparison to conventional plain and conventional rectangular pocketed pads.

The Effect of Two Sided Surface Roughness on Ultra-Thin Gas Films

1983 ◽  
Vol 105 (1) ◽  
pp. 131-137 ◽  
Author(s):  
J. W. White
Keyword(s):  
Surface Roughness ◽  
Current Method ◽  
Solution Procedure ◽  
Lubrication Equation ◽  
Write Heads ◽  
Stationary Surface ◽  
Simple Geometry ◽  
Load Carrying ◽  
Bearing Number ◽  
Gas Bearing

The influence of two sided striated surface roughness on bearing load carrying capacity is analyzed for very low clearance gas films. As was done for the case of stationary surface roughness [1], a model lubrication equation appropriate for extremely high gas bearing number films is solved analytically for several simple geometry bearings. The analytic solution provides information on the exact relationship between pressure and roughness which makes it possible to ensemble average the lubrication equation before solution, greatly simplifying the solution procedure. It is found that the translating surface roughness has an influence on load similar to that caused by the stationary surface. Exact solutions with the current method are compared with those of the theory attributed to Christensen and To̸nder. The results are strikingly different and serve to bring attention to the fact that for high bearing number compressible lubrication, the Christensen-To̸nder theory is inappropriate. The results reported here should find application in the computer peripherals area where read/write heads now routinely hover over a spinning disk at clearances of 0.25 micron.

Surface Roughness Effects on the Load Carrying Capacity of Very Thin Compressible Lubricating Films

1980 ◽  
Vol 102 (4) ◽  
pp. 445-451 ◽  
Author(s):  
J. W. White
Keyword(s):  
Surface Roughness ◽  
Exact Solutions ◽  
Carrying Capacity ◽  
Current Method ◽  
Previous Method ◽  
Finite Width ◽  
Load Carrying Capacity ◽  
Roughness Effects ◽  
Lubrication Equation ◽  
Load Carrying

The effect of surface roughness on load carrying capacity of very low clearance gas bearings is analyzed. A model lubrication equation appropriate for high bearing number, finite width films is first derived. Then, by obtaining exact solutions to several simple geometry bearings, the “closure problem” or statistical relationship of pressure and spacing is revealed. The lubrication equation is then ensamble averaged and solved for several test cases. The seemingly subtle differences in ensamble averaging the transverse terms in the lubrication equation are compared for the current theory and a previous method and are shown to produce vast differences in load carrying capacity. The current method is expected to be the correct approach since it is based on a generalization of exact solutions.

scholarly journals EFFECT OF SURFACE ROUGHNESS ON STEADY PERFORMANCE OF HYDROSTATIC THRUST BEARINGS: RABINOWITSCH FLUID MODEL

2019 ◽  
Author(s):  
Udaya Pratap Singh
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Load Capacity ◽  
Numerical Results ◽  
Integral Approach ◽  
Load Carrying Capacity ◽  
Film Pressure ◽  
Thrust Bearings ◽  
Longitudinal Roughness ◽  
Load Carrying

Purpose of the present theoretical investigation is to analyze the effects of surface roughness on the steady-state performance of stepped circular hydrostatic thrust bearings lubricated with non-Newtonian Rabinowitsch type fluids. Results for film pressure and load-carrying capacity have been plotted and analyzed on the basis of numerical results. To take the effects of surface roughness into account, Christensen theory of rough surface has been adopted. The expression for pressure gradient has been derived by means of the energy integral approach. This approach avoids the derivation of Reynolds’ equation. The numerical results for film pressure and load capacity have been obtained using Mathematica. It was observed that in comparison with smooth surfaces, dimensionless film pressure and load capacity is lower for longitudinal roughness and higher for circular roughness patterns with and the variations are significant. Load carrying capacity decreases with the increase of longitudinal roughness and, increases with the increase of circular roughness. Further, the effects of surface roughness and non-Newtonian lubricants are significant for larger values of inertia parameter. Because of the closeness of results to the experimental values, this study will be helpful in the design of circular hydrostatic thrust bearings.

Surface Roughness Effects in the Region Between High Wave Number and High Bearing Number Limited Lubricant Flows

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
James White
Keyword(s):  
Surface Roughness ◽  
Roughness Length ◽  
Wave Number ◽  
Roughness Effects ◽  
High Wave Number ◽  
High Wave ◽  
Lubrication Equation ◽  
Order Of Magnitude ◽  
Bearing Number ◽  
Gas Bearing

The ability to predict surface roughness effects is now well established for gas bearings that satisfy the requirements for either high wave number–limited or high bearing number–limited conditions. However, depending on the parameters involved, a given bearing configuration may not satisfy either of these limited requirements for analysis of roughness effects. Well-established methods for the analysis of surface roughness effects on gas lubrication are not yet available outside of these two limited regions. With that as motivation, this paper then reports an analytical investigation of rough surface gas-bearing effects for the region bounded on one side by high wave number–limited conditions and on the other by high bearing number–limited effects. It emphasizes the gas-bearing region, where shear-driven flow rate and pressure-driven flow rate due to surface roughness are of the same order of magnitude. This paper makes use of the compressible continuum form of the Reynolds equation of lubrication together with multiple-scale analysis to formulate a governing lubrication equation appropriate for the analysis of striated roughness effects collectively subject to high bearing number (Λ→∞), high inverse roughness length scale (β→∞), and unity order of magnitude-modified bearing number based on roughness length scale (Λ2=Λ/β=O(1)). The resulting lubrication equation is applicable for both moving and stationary roughness and can be applied in either averaged or un-averaged form. Several numerical examples and comparisons are presented. Among them are results that illustrate an increased sensitivity of bearing force to modified bearing number for Λ2=O(1). With Λ2 in this range, bearings with either moving or stationary roughness exhibit increased force sensitivities, but the effects act in opposite ways. That is, while an increase in modified bearing number causes a decrease in force for stationary roughness, the same increase in modified bearing number causes an increase in force for moving roughness.

The Influence of Surface Topography on Energy Dissipation and Compliance in Tangentially Loaded Elastic Contacts

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Simon Medina ◽  
Andrew V. Olver ◽  
Daniele Dini
Keyword(s):  
Surface Roughness ◽  
Energy Dissipation ◽  
Partial Slip ◽  
Fast Calculation ◽  
Numerical Solution Method ◽  
Correlation Lengths ◽  
Loading Method ◽  
Non Gaussian ◽  
Gaussian Surface ◽  
Tangential Directions

The influence of non-Gaussian surface roughness on elastic contacts loaded in both normal and tangential directions has been investigated. A numerical solution method based on the multilevel scheme and incorporating the theorem of Ciavarella/Jaeger has been implemented, which allows fast calculation of partial slip loading conditions, including the energy dissipation for a fully reversed tangential loading cycle. The effect of varying roughness rms, skewness, kurtosis, and correlation lengths on contact areas, stiffness values, and energy dissipation is presented, and the significance of these parameters and of the loading method are discussed. It was found that the energy dissipation can be greatly increased by greater surface roughness. Maps showing how the energy dissipation is distributed within the contact are presented, which provide some explanation for this observation and the scatter that may occur for surfaces of nominally similar roughness. The suitability of these parameters for predicting the contact behavior of rough surfaces is also considered.

Performance Characteristic Analysis of Sector-Shaped Pad Thrust Bearings in Turbulent Inertial Flow Regime Under Three Types of Lubrication Conditions

1990 ◽  
Vol 112 (3) ◽  
pp. 477-484 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Carrying Capacity ◽  
Control Volume ◽  
Linearization Method ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Load Carrying Capacity ◽  
Characteristic Analysis ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Lubrication Conditions

An influence of lubrication conditions on the performance characteristics of sector-shaped pad thrust bearings, which are subjected to the effects of both turbulence and fluid film inertia, is investigated theoretically and experimentally. The momentum equations in terms of pressure and stream function are solved by applying a numerical calculation technique combining control volume integration and the Newton-Raphson linearization method, under three kinds of inlet boundary conditions in relation to three types of lubrication conditions, namely: the flooded condition, the over flooded condition, and the starved condition. Sample numerical results pertaining to the pressure distribution, load carrying capacity and inlet flow rate are obtained for θ = 60 deg, R1 = 0.5, Re = 2000, Re* = 0 to 1.6 and A = 1.0 to 2.0, and the results of the load-carrying capacity are compared with experimental results. From the theoretical and experimental results, the relationships between the lubrication conditions and the static performance characteristics of the bearings are clarified.

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