Load Support and Leakage from Microasperity-Lubricated Face Seals

1969 ◽  
Vol 91 (4) ◽  
pp. 726-731 ◽  
Author(s):  
J. N. Anno ◽  
J. A. Walowit ◽  
C. M. Allen
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Poiseuille Flow ◽  
Linear Velocity ◽  
Channel Height ◽  
Face Seal ◽  
Rotor Rotation ◽  
Lubricant Films ◽  
Face Seals ◽  
Lubricant Viscosity

Observations of load support from various shapes of microasperities placed on the surface of a rotary-shaft face seal indicate that all are comparable in this respect and generally follow the theory developed previously for cylindrical asperities. Both positive (protrusions) and negative (valleys) asperities produce similar load support, developing stable hydrodynamic lubricant films of the order of 10−5 in. for linear velocity of at least 50 in./sec, lubricant viscosity as low as 1 cp, and loads of the order of 100 pounds or higher. Variations in the film thickness with these parameters is predicted by the theory developed on the basis that an effective small tilt exists on the tops of the asperities. Leakage from microasperity-lubricated seals on the average follows the predictions of Poiseuille flow, with the exception that a significant effect of rotor rotation is observed. For a leakage channel height of 10−4 in., leakage was typically of the order of 0.2 in.3/hr for a pressure drop of 10 psi across the seal.

scholarly journals Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Vincenzo Petrone ◽  
Adolfo Senatore ◽  
Vincenzo D'Agostino
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Free Volume ◽  
Experimental Studies ◽  
Line Contact ◽  
Volume Model ◽  
Free Volume Model ◽  
Pressure Area ◽  
New Formulation ◽  
Lubricant Viscosity

This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations.

Numerical Analysis of Dry Gas Face Seals With Spiral Groove and Inner Annular Groove

2008 ◽  
Author(s):  
Xu-Dong Peng ◽  
Li-Li Tan ◽  
Ji-Yun Li ◽  
Song-En Sheng ◽  
Shao-Xian Bai
Keyword(s):  
Reynolds Equation ◽  
Geometric Parameters ◽  
Axial Stiffness ◽  
Face Seal ◽  
Optimization Principle ◽  
Face Seals ◽  
The Face ◽  
Gas Face Seal ◽  
Film Stiffness ◽  
Spiral Grooves

A two-dimensional Reynolds equation was established for isothermal compressible gas between the two faces of a dry gas face seal with both spiral grooves and an inner annular groove onto the hard face. The opening force, the leakage rate, the axial film stiffness and the film stiffness to leakage ratio were calculated by finite element method. The comparisons with the sealing performances of a typical gas face seal only with spiral grooves onto its hard face were made. The effects of the face geometric parameters on the static behavior of such a seal were analyzed. The optimization principle for geometric parameters of a dry gas face seals with spiral grooves and an inner annular groove was presented. The recommended geometric parameters of spiral grooves and circular groove presented by optimization can ensure larger axial stiffness while lower leakage rates.

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

Quantification of the Surface Morphology of Lubricant Films With Polar End Groups Using Molecular Dynamics Simulation: Periodic Changes in Morphology Depending on Film Thickness

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Susumu Ogata ◽  
Hedong Zhang ◽  
Kenji Fukuzawa ◽  
Yasunaga Mitsuya
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Surface Morphology ◽  
Film Thickness ◽  
Film Surface ◽  
Dynamics Simulation ◽  
Molecular Probe ◽  
Coarse Grained ◽  
End Groups ◽  
Lubricant Films

Using a coarse-grained molecular dynamics simulation based on the bead-spring polymer model, we reproduced the film distribution of molecularly thin lubricant films with polar end groups coated on the disk surface and quantified the film-surface morphology using a molecular-probe scanning method. We found that the film-surface morphology changed periodically with increasing film thickness. The monolayer of a polar lubricant that entirely covers the solid surface provides a flat lubricant surface by exposing its nonpolar backbone outside of the monolayer. By increasing film thickness, the end beads aggregate to make clusters, and bulges form on the lubricant surface, accompanying an increase in surface roughness. The bulges continue to grow even though the averaged film thickness reaches or exceeds the bilayer thickness. With further increases in film thickness, the clusters start to be uniformly distributed in the lateral direction to clearly form a third layer. As for the formation of fourth and fifth layers, the process is basically the same as that for the second and third layers. Through our calculations of the intermolecular potential field and the intermolecular force field, these values are found to change periodically and are synchronized with the formation of molecule aggregations, which explains the mechanism of forming the layered structure that is inherent to a polar lubricant.

Experimental Studies of Adiabatic Flow Boiling in Fractal-Like Branching Micro-Channels

2008 ◽  
Author(s):  
Brian J. Daniels ◽  
James A. Liburdy ◽  
Deborah V. Pence
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Channel Length ◽  
Channel Height ◽  
Channel Network ◽  
Adiabatic Flow ◽  
Numerical Predictions ◽  
Micro Channels

Experimental results of adiabatic boiling of water flowing through a fractal-like branching microchannel network are presented and compared to numerical simulations for identical flow conditions. The fractal-like branching channel network had channel length and width ratios between adjacent branching levels of 0.7071, a total flow length of 18 mm, a channel height of 150 μm and a terminal channel width of 100 μm. The channels were DRIE etched into a silicon disk and pyrex was anodically bonded to the silicon to form the channel top and allowed visualization of the flow within the channels. The water flowed from the center of the disk where the inlet was laser cut through the silicon to the periphery of the disc. The flow rates ranged from 100 to 225 g/min and the inlet subcooling levels varied from 0.5 to 6 °C. Pressure drop across the channel as well as void fraction in each branching level were measured for each of the test conditions. The measured pressure drop ranged from 20 to 90 kPa, and the measured void fraction ranged from 0.3 to 0.9. The pressure drop results agree well with the numerical predictions. The measured void fraction results followed the same trends as the numerical results.

Hydrodynamic Lubrication and Wear in Wavy Contacting Face Seals

1978 ◽  
Vol 100 (1) ◽  
pp. 81-90 ◽  
Author(s):  
A. O. Lebeck ◽  
J. L. Teale ◽  
R. E. Pierce
Keyword(s):  
Surface Roughness ◽  
Hydrodynamic Lubrication ◽  
Surface Profile ◽  
Operating Conditions ◽  
Face Seal ◽  
Hydrodynamic Load ◽  
Surface Waviness ◽  
Wear Rates ◽  
Elastic Deflection ◽  
Face Seals

A model of face seal lubrication is proposed and developed. Hydrodynamic lubrication for rough surfaces, surface waviness, asperity load support, elastic deflection, and wear are considered in the model. Predictions of the ratio of hydrodynamic load support to asperity load support are made for a face seal sealing a low viscosity liquid where some contact does occur and surface roughness is important. The hydrodynamic lubrication is caused by circumferential surface waviness on the seal faces. Waviness is caused by initial out of flatness or any of the various distortions that occur on seal ring faces in operation. The equilibrium solution to the problem yields one dimensional hydrodynamic and asperity pressure distributions, mean film thickness, elastic deflection, and friction for a given load on the seal faces. The solution is found numerically. It is shown that the fraction of hydrodynamic load support depends on many parameters including the waviness amplitude, number of waves around the seal, face width, ring stiffness, and most importantly, surface roughness. For the particular seal examined the fraction of load support would be small for the amount of waviness expected in this seal. However, if the surface roughness were lower, almost complete lift-off is possible. The results of the analysis show why the initial friction and wear rates in mechanical face seals may vary widely; the fraction of hydrodynamic load support depends on the roughness and waviness which are not necessarily controlled. Finally, it is shown how such initial waviness effects disappear as the surface profile is altered by wear. This may take a long or short time, depending on the initial amount of hydrodynamic load support, but unless complete liftoff is achieved under all operating conditions, the effects of initial waviness will vanish in time for steady state conditions. Practical implications are drawn for selecting some seal parameters to enhance initial hydrodynamic load support without causing significant leakage.

Pumping Action of Aligned Smooth Face Seals Due to Axial Vibrations—Theory

1984 ◽  
Vol 106 (3) ◽  
pp. 344-351
Author(s):  
M. Kaneta ◽  
Y. Jinnouchi ◽  
M. Fukahori
Keyword(s):  
Film Thickness ◽  
Flow Resistance ◽  
Analytical Study ◽  
Sinusoidal Oscillation ◽  
Periodic Fluctuation ◽  
Face Seals ◽  
Axial Vibrations

This is an analytical study of the mechanism of pumping action produced in two axially symmetrical disks. The disks have a continuous parallel film thickness between them, and one of them has a recess at the center and is subjected to a normal sinusoidal oscillation. It is found out that whether the pumping action is inward or outward depends upon a shift of phase between a variation of flow resistance due to a periodic fluctuation of the film thickness between seal faces and a variation of pressure in the recess.

Thermoelastohydrodynamic Behavior of Mechanical Gas Face Seals Operating at High Pressure

2007 ◽  
Vol 129 (4) ◽  
pp. 841-850 ◽  
Author(s):  
Sébastien Thomas ◽  
Noël Brunetière ◽  
Bernard Tournerie
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Numerical Modeling ◽  
Face Seal ◽  
Inertia Effects ◽  
Real Gas ◽  
Choked Flow ◽  
Face Seals ◽  
Mechanical Face Seal ◽  
Gas Expansion

A numerical modeling of thermoelastohydrodynamic mechanical face seal behavior is presented. The model is an axisymmetric one and it is confined to high pressure compressible flow. It takes into account the behavior of a real gas and includes thermal and inertia effects, as well as a choked flow condition. In addition, heat transfer between the fluid film and the seal faces is computed, as are the elastic and thermal distortions of the rings. In the first part of this paper, the influence of the coning angle on mechanical face seal characteristics is studied. In the second part, the influence of the solid distortions is analyzed. It is shown that face distortions strongly modify both the gap geometry and the mechanical face seal’s performance. The mechanical distortions lead to a converging gap, while the gas expansion, by cooling the fluid, creates a diverging gap.

A two-dimensional-three-component model for spanwise rotating plane Poiseuille flow

2019 ◽  
Vol 880 ◽  
pp. 478-496 ◽  
Author(s):  
Shengqi Zhang ◽  
Zhenhua Xia ◽  
Yipeng Shi ◽  
Shiyi Chen
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Reynolds Shear Stress ◽  
Streamwise Velocity ◽  
Channel Height ◽  
Neutral Stability ◽  
Two Dimensional ◽  
Plane Poiseuille Flow ◽  
Rotation Numbers ◽  
3C Model

Spanwise rotating plane Poiseuille flow (RPPF) is one of the canonical flow problems to study the effect of system rotation on wall-bounded shear flows and has been studied a lot in the past. In the present work, a two-dimensional-three-component (2D/3C) model for RPPF is introduced and it is shown that the present model is equivalent to a thermal convection problem with unit Prandtl number. For low Reynolds number cases, the model can be used to study the stability behaviour of the roll cells. It is found that the neutral stability curves, critical eigensolutions and critical streamfunctions of RPPF at different rotation numbers ($Ro$) almost collapse with the help of a rescaling with a newly defined Rayleigh number $Ra$ and channel height $H$. Analytic expressions for the critical Reynolds number and critical wavenumber at different $Ro$ can be obtained. For a turbulent state with high Reynolds number, the 2D/3C model for RPPF is self-sustained even without extra excitations. Simulation results also show that the profiles of mean streamwise velocity and Reynolds shear stress from the 2D/3C model share the same linear laws as the fully three-dimensional cases, although differences on the intercepts can be observed. The contours of streamwise velocity fluctuations behave like plumes in the linear law region. We also provide an explanation to the linear mean velocity profiles observed at high rotation numbers.

scholarly journals Lubrication and Wear Characteristics of Mechanical Face Seals under Random Vibration Loading

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1285
Author(s):  
Wentao He ◽  
Shaoping Wang ◽  
Chao Zhang ◽  
Xi Wang ◽  
Di Liu
Keyword(s):  
Dynamic Model ◽  
Random Vibration ◽  
Experimental Studies ◽  
Lumped Parameter Model ◽  
Axial Stiffness ◽  
Face Seal ◽  
Wear Characteristics ◽  
Vibration Loading ◽  
Face Seals ◽  
Mechanical Face Seal

The service life of mechanical face seals is related to the lubrication and wear characteristics. The stable analytical methods are commonly used, but they cannot address effects of random vibration loading, which, according to experimental studies, are important factors for lubrication and wear of mechanical face seals used in air and space vehicles. Hence, a dynamic model for mechanical face seals is proposed, with a focus on the effects of random vibration loading. The mechanical face seal in the axial direction is described as a mass-spring-damping system. Spectrum analysis specified for random vibration is then performed numerically to obtain the response power spectral density (PSD) of the mechanical face seal and calculate the root mean square (RMS) values under random vibration conditions. A lumped parameter model is then developed to examine how dynamic parameters such as stiffness and damping affect the lubrication regimes of mechanical face seals. Based on the dynamic model and Archard wear equation, a numerical wear simulation method is proposed. The results elucidated that the increase of input acceleration PSDs, the decrease of axial damping, and the increase of axial stiffness lead to the probability of the mechanical face seal operating under full film lubrication regime increase and finally the decrease of wear. This research provides a guideline for improving the adaptability of mechanical face seals under random vibration environments.

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