A Deterministic Mixed Lubrication Model for Mechanical Seals

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Christophe Minet ◽  
Noël Brunetière ◽  
Bernard Tournerie
Keyword(s):  
Flow Model ◽  
Hydrodynamic Lubrication ◽  
Industrial Applications ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Mechanical Seals ◽  
Optimal Point ◽  
Lubrication Regimes ◽  
Face Seals ◽  
Stribeck Curves

Mechanical seals are commonly used in industrial applications. The main purpose of these components is to ensure the sealing of rotating shafts. Their optimal point of operation is obtained at the boundary between the mixed and hydrodynamic lubrication regimes. However, papers focused on this particular aspect in face seals are rather scarce compared with those dealing with other popular sealing devices. The present study thus proposes a numerical flow model of mixed lubrication in mechanical face seals. It achieves this by evaluating the influence of roughness on the performance of the seal. The choice of a deterministic approach has been made, this being justified by a review of the literature. A numerical model for the generation of random rough surfaces has been used prior to the flow model in order to give an accurate description of the surface roughness. The model takes cavitation effects into account and considers Hertzian asperity contact. Results for the model, including Stribeck curves, are presented as a function of the duty parameter.

Profile Design for Misaligned Journal Bearings Subjected to Transient Mixed Lubrication

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Thomas Gu ◽  
Q. Jane Wang ◽  
Shangwu Xiong ◽  
Zhong Liu ◽  
Arup Gangopadhyay ◽  
...  
Keyword(s):  
Film Thickness ◽  
Performance Metrics ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Industrial Applications ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Minimum Film Thickness ◽  
Profile Design

Misalignment between the shaft and the bearing of a journal bearing set may be inevitable and can negatively impact journal bearing performance metrics in many industrial applications. This work proposes a convex profile design of the journal surface to help counteract the negative effects caused by such a misalignment. A transient mass-conserving hydrodynamic Reynolds equation model with the Patir–Cheng flow factors and the Greenwood–Tripp pressure–gap relationship is developed to conduct the design and analysis. The results reveal that under transient impulse loading, a properly designed journal profile can help enhance the minimum film thickness, reduce mean and peak bearing frictions, and increase bearing durability by reducing the asperity-related wear load. The mechanism for the minimum film thickness improvement due to the profile design is traced to the more even distribution of the hydrodynamic pressure toward the axial center of the bearing. The reason for the reductions of the friction and wear load is identified to be the decreased asperity contact by changing the lubrication regime from mixed lubrication to nearly hydrodynamic lubrication. Parametric studies and a case study are reported to highlight the key points of the profile design and recommendations for profile height selection are made according to misalignment parameters.

The influence of surface texturing on the transition of the lubrication regimes between a piston ring and a cylinder liner

2016 ◽  
Vol 18 (8) ◽  
pp. 785-796 ◽  
Author(s):  
Chunxing Gu ◽  
Xianghui Meng ◽  
Youbai Xie ◽  
Di Zhang
Keyword(s):  
Piston Ring ◽  
Surface Texturing ◽  
Cylinder Liner ◽  
Mixed Lubrication ◽  
Textured Surface ◽  
Asperity Contact ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Mixed Lubrication Regime ◽  
Stribeck Curves

This article employs a mixed lubrication model to investigate the performance of the textured surface. The Jakobsson–Floberg–Olsson model is used to obtain the hydrodynamic support of the textured conjunction, while the calculation of the asperity contact load is based on the load-sharing concept. Based on the simulated Stribeck curves of the smooth surface and the textured surface, comparisons are conducted to study the effect of texturing under different lubrication regimes. It appears that the transition of lubrication regimes is influenced by the texturing parameters and the convergence degrees of conjunction. The presence of textures delays the appearance of the mixed lubrication regime and the boundary lubrication regime.

Mixed Lubrication Modelling in Mechanical Face Seals

2008 ◽  
Author(s):  
C. Minet ◽  
N. Brunetie`re ◽  
B. Tournerie
Keyword(s):  
Friction Coefficient ◽  
Numerical Model ◽  
Hydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Mechanical Seal ◽  
Deterministic Approach ◽  
Lubrication Regimes ◽  
Face Seals ◽  
Non Gaussian

This paper presents a numerical model of mechanical seal operating in mixed lubrication. It is based on a deterministic approach using realistic roughness description. This model is able to simulate the transition from mixed to hydrodynamic lubrication regimes corresponding to a minimum of the friction coefficient. Moreover it is able to work with non Gaussian surfaces and oriented surfaces.

scholarly journals Mixed and Fluid Film Lubrication Characteristics of Worn Journal Bearings

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Toshiharu Kazama ◽  
Yukihito Narita
Keyword(s):  
Frictional Coefficient ◽  
Journal Bearings ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Fluid Film ◽  
Asperity Contact ◽  
Lubrication Regimes ◽  
Lubrication Characteristics ◽  
Film Lubrication ◽  
Fluid Film Lubrication

The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically examined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and Williamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation is applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal center, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions are drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For smaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure and coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate continuously increases.

An EHD-mixed lubrication analysis of main bearings for diesel engine based on coupling between flexible whole engine block and crankshaft

2015 ◽  
Vol 67 (2) ◽  
pp. 150-158 ◽  
Author(s):  
Lidui Wei ◽  
Haijun Wei ◽  
Shulin Duan ◽  
Yu Zhang
Keyword(s):  
Diesel Engine ◽  
Flow Model ◽  
Mixed Lubrication ◽  
Engine Block ◽  
Contact Theory ◽  
Asperity Contact ◽  
Block Model ◽  
Content Type ◽  
Oil Film ◽  
Average Flow Model

Purpose – The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings – Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and so does friction loss. Therefore, coordination deformation ability of whole engine block is favorable to mean load. In the whole block model, friction contact happens on both upper shell and lower shell positions. In addition, average oil film fill ratio at the key position becomes smaller in the whole engine block model, and consequently increases the chances of cavitations erosion more. So, wearing resistance of both upper and lower shells and anti-cavitations erosion ability must be enhanced simultaneously. Originality/value – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the CMS method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an EHD-mixed lubrication model of the main bearings for the diesel engine is built, which can predict the lubrication of journal bearings more accurately.

Research on Mixed Lubrication Problems of the Non-Gaussian Rough Textured Surface With the Influence of Stochastic Roughness in Consideration

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Chunxing Gu ◽  
Xianghui Meng ◽  
Shuwen Wang ◽  
Xiaohong Ding
Keyword(s):  
Tribological Properties ◽  
Friction And Wear ◽  
Mixed Lubrication ◽  
Textured Surface ◽  
Asperity Contact ◽  
Textured Surfaces ◽  
Negative Skewness ◽  
Non Gaussian ◽  
Stribeck Curves ◽  
Average Flow Model

Abstract In order to find the effects of surface topography on the tribological properties of the rough textured surfaces, an improved mixed lubrication model allowing specifying the standard deviation, the skewness, and the kurtosis was developed. In this model, by considering the non-Gaussian properties of rough surfaces, an improved average flow model was combined with a modified statistical elastoplastic asperity contact model. The performances of the slider bearings with two arrays of anisotropic textures were studied in terms of Stribeck curves. It appears that the tribological properties of the anisotropic textures are sensitive to the sliding direction. Meanwhile, the surfaces with more negative skewness or the lower kurtosis can obtain better tribological performances related to friction and wear.

Elastohydrodynamic Lubrication: A Gateway to Interfacial Mechanics—Review and Prospect

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Dong Zhu ◽  
Q. Jane Wang
Keyword(s):  
Hydrodynamic Lubrication ◽  
Film Formation ◽  
Elastohydrodynamic Lubrication ◽  
Numerical Approach ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Interfacial Mechanics ◽  
Special Cases ◽  
Dry Contact ◽  
Film Lubrication

Elastohydrodynamic Lubrication (EHL) is commonly known as a mode of fluid-film lubrication in which the mechanism of hydrodynamic film formation is enhanced by surface elastic deformation and lubricant viscosity increase due to high pressure. It has been an active and challenging field of research since the 1950s. Significant breakthroughs achieved in the last 10–15 years are largely in the area of mixed EHL, in which surface asperity contact and hydrodynamic lubricant film coexist. Mixed EHL is of the utmost importance not only because most power-transmitting components operate in this regime, but also due to its theoretical universality that dry contact and full-film lubrication are in fact its special cases under extreme conditions. In principle, mixed EHL has included the basic physical elements for modeling contact, or hydrodynamic lubrication, or both together. The unified mixed lubrication models that have recently been developed are now capable of simulating the entire transition of interfacial status from full-film and mixed lubrication down to dry contact with an integrated mathematic formulation and numerical approach. This has indeed bridged the two branches of engineering science, contact mechanics, and hydrodynamic lubrication theory, which have been traditionally separate since the 1880s mainly due to the lack of powerful analytical and numerical tools. The recent advancement in mixed EHL begins to bring contact and lubrication together, and thus an evolving concept of “Interfacial Mechanics” can be proposed in order to describe interfacial phenomena more precisely and collaborate with research in other related fields, such as interfacial physics and chemistry, more closely. This review paper briefly presents snapshots of the history of EHL research, and also expresses the authors’ opinions about its further development as a gateway to interfacial mechanics.

A New Approach to Determine Lubrication Regimes of Piston-Ring Assemblies

1997 ◽  
Vol 119 (4) ◽  
pp. 808-816 ◽  
Author(s):  
Naeim A. Henein ◽  
Shengqiang Huang ◽  
Walter Bryzik
Keyword(s):  
Piston Ring ◽  
Hydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Spark Ignition Engine ◽  
Frictional Torque ◽  
New Approach ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Mixed Lubrication Regime ◽  
And Shifts

A new approach is developed to determine piston-ring assembly lubrication regimes from the instantaneous frictional torque measured for the whole engine. This is based on the variation of the friction coefficient with the duty parameter in the Stribeck diagram over the mixed and hydrodynamic lubrication regimes. The derived equation determines the lubrication regimes from the slope of the line in the Stribeck diagram. A single cylinder spark ignition engine was instrumented to determine the total instantaneous frictional torque of the engine. Experiments were conducted under different loads at a constant speed. Results show that the regime is mixed lubrication near the top dead center (TDC) and shifts to the hydrodynamic lubrication regime as the piston moves away from TDC. The extent of the mixed lubrication regime depends on engine load and speed.

Experimental and numerical studies of positive texture effect on friction reduction of sliding contact under mixed lubrication

2020 ◽  
pp. 135065012093091 ◽  
Author(s):  
P Venkateswara Babu ◽  
Syed Ismail ◽  
B Satish Ben
Keyword(s):  
Numerical Study ◽  
Mixed Lubrication ◽  
Friction Reduction ◽  
Asperity Contact ◽  
Textured Surfaces ◽  
Area Density ◽  
Surface Textures ◽  
Lubrication Regimes ◽  
Numerical Predictions ◽  
Pin On Disc

Textured surfaces have been remarkable in improving the frictional performance of sliding contacts, particularly at instances such as boundary or mixed lubrication regimes. This article reports the results of an experimental and numerical study carried out by introducing surface textures in the form of protrusions to investigate its effects on friction performance under a mixed lubrication regime. The surface textures produced by the chemical etching process are tested on the pin on disc test rig by varying area density and height of the texture. In numerical simulation, the modified Reynolds equation (Patir–Cheng flow model) and asperity contact model (Greenwood–Tripp model) are solved for hydrodynamic and asperity pressures, respectively. The results indicate that the experimental measurements are qualitatively in good agreement with numerical predictions. Furthermore, the simulations are performed for different texture shapes by varying texture area density, height, and sliding velocity. The results depict that a maximum friction reduction of 87% with elliptical textures compared to the un-textured case.

Hydrodynamic Lubrication in Wavy Contacting Face Seals—A Two Dimensional Model

1981 ◽  
Vol 103 (4) ◽  
pp. 578-586 ◽  
Author(s):  
A. O. Lebeck
Keyword(s):  
Hydrodynamic Lubrication ◽  
Fluid Pressure ◽  
Asperity Contact ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Wear Rates ◽  
Face Width ◽  
Two Dimensional Model ◽  
Face Seals

The role of circumferential surface waviness in contacting mechanical face seals is examined. First, a two dimensional model is developed. The model considers waviness amplitude, surface roughness, asperity contact, hydrodynamic and hydrostatic pressures, and fluid cavitation. Given waviness, roughness, number of waves, geometry, and sealed fluid, the model predicts the fraction of load supported by fluid pressure, the relative wear rate, friction coefficient, and leakage rate. A numerical method for solving this problem is presented. Using this model, the effects of waviness amplitude, roughness, number of waves, face width, and sealed pressure on seal performance are examined. Based on these results, certain conclusions are reached concerning the role of waviness in commercial face seals. Finally, using the model, it is shown how waviness can be applied to advantage to reduce seal friction and wear rates.

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