On the Theory of Thermal Elastohydrodynamic Lubrication at High Slide-Roll Ratios—Circular Glass-Steel Contact Solution at Opposite Sliding

2000 ◽  
Vol 123 (4) ◽  
pp. 816-821 ◽  
Author(s):  
Feng Guo ◽  
Peiran Yang ◽  
Shiyue Qu
Keyword(s):  
Steady State ◽  
Numerical Solution ◽  
Elastohydrodynamic Lubrication ◽  
Numerical Results ◽  
Operating Conditions ◽  
Theoretical Evidence ◽  
Thermal Ehl ◽  
Wedge Effect ◽  
Film Profile ◽  
Circular Contact

A full numerical solution for the thermal EHL problem in circular contact formed by steel-glass conjunctions with slide-roll ratios larger than 2 has been carried out. An anomalous film profile, which is similar to that reported by Kaneta et al. (1996), has been obtained. The numerical results by the authors, involving three basic kinds of film profiles, the kinematic conditions for the formation of dimples, and the variations of dimples and traction behavior with operating conditions, have been carefully compared with the experiments by Kaneta et al., and provided a sound theoretical evidence of the dimple phenomena under steady-state conditions. The present study indicates that the temperature-viscosity-wedge effect seems to be an essential mechanism for the dimple phenomena.

Size Effect on the Behavior of Thermal Elastohydrodynamic Lubrication of Roller Pairs

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Xiaoling Liu ◽  
Jinlei Cui ◽  
Peiran Yang
Keyword(s):  
Size Effect ◽  
Newtonian Fluid ◽  
Effective Viscosity ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Load Parameter ◽  
Performance Results ◽  
Thermal Ehl ◽  
Strong Size Effect

In order to investigate the size effect on elastohydrodynamic lubrication (EHL) of roller pairs, complete numerical solutions for both the Newtonian fluid and the Eyring fluid thermal EHL problems of roller pairs under steady state conditions have been achieved. It can be seen that there is no size effect on the isothermal EHL performance; however, there is a very strong size effect on the thermal EHL performance. Results show that the term of shearing heat is the most important factor for the film temperature when the size of a contact changes. Comparison between the Newtonian solution and the Eyring solution has been made under some operating conditions. It is interesting to see that the effective viscosity of the Eyring fluid is nearly the same as that of the Newtonian fluid when the size of a contact is large enough. The non-Newtonian effect, therefore, can be ignored when the size of a contact is very large. It is equally interesting to see that the thermal effect can be ignored when the size of a contact is very small. In addition, the influence of the velocity parameter, the load parameter, and the slide-roll ratio on the lubricating performance for various sizes of contacts has been investigated.

Thermal Elastohydrodynamic Lubrication of Rider Rings

1984 ◽  
Vol 106 (4) ◽  
pp. 492-498 ◽  
Author(s):  
Vilmos Simon
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Temperature Variation ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Oil Film ◽  
The Real ◽  
Ring Geometry

The full thermal elastohydrodynamic analysis of the lubrication of rider rings is presented. A numerical solution of the coupled Reynolds, elasticity, energy, and Laplace’s equations for the oil film thickness, pressure, and temperature and rider rings temperatures is obtained. The temperature variation across the oil film is included. The real rider ring geometry is treated. The effect of the operating conditions on the performance characteristics is discussed.

Progressive Mesh Densification Method for Numerical Solution of Mixed Elastohydrodynamic Lubrication

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Wei Pu ◽  
Jiaxu Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Numerical Solution ◽  
Numerical Solutions ◽  
Initial Conditions ◽  
Solution Process ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Machined Surface ◽  
Progressive Mesh ◽  
Wide Range

Numerical solution of mixed elastohydrodynamic lubrication (EHL) is of great importance for the study of lubrication formation and breakdown, as well as surface failures of mechanical components. However, converged and accurate numerical solutions become more difficult, and solution process with a fixed single discretization mesh for the solution domain appears to be quite slow, especially when the lubricant films and surface contacts coexist with real-machined roughness involved. Also, the effect of computational mesh density is found to be more significant if the average film thickness is small. In the present study, a set of sample cases with and without machined surface roughness are analyzed through the progressive mesh densification (PMD) method, and the obtained results are compared with those from the direct iteration method with a single fixed mesh. Besides, more numerical analyses with and without surface roughness in a wide range of operating conditions are conducted to investigate the influence of different compound modes in order to optimize the PMD procedure. In addition, different initial conditions are used to study the effect of initial value on the behaviors of this transient solution. It is observed that, no matter with or without surface roughness considered, the PMD method is stable for transient mixed EHL problems and capable of significantly accelerating the EHL solution process while ensuring numerical accuracy.

Elastohydrodynamic Lubrication of Hypoid Gears

1981 ◽  
Vol 103 (1) ◽  
pp. 195-203 ◽  
Author(s):  
V. Simon
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Temperature Variations ◽  
Hypoid Gears ◽  
Oil Film ◽  
Gear Teeth ◽  
Energy Equations

The full thermal elastohydrodynamic analysis of the lubrication of hypoid gears is presented. A numerical solution of the coupled Reynolds, elasticity and energy equations for the pressure, temperature and film thickness is obtained. The temperature variations across the oil film and in the pinion and gear teeth are included. The real tooth geometry of the modified hypoid gears is treated. The effect of the operating conditions on the performance characteristics is discussed.

Effect of angular speed of cam on oil film variation in the line contact thermal EHL of a cam-tappet pair

2020 ◽  
Vol 72 (6) ◽  
pp. 713-722
Author(s):  
Hongwei Tang ◽  
Jing Wang ◽  
Nannan Sun ◽  
Jianrong Zhu
Keyword(s):  
Film Thickness ◽  
Peer Review ◽  
Elastohydrodynamic Lubrication ◽  
Grid Method ◽  
Angular Speed ◽  
Content Type ◽  
Sliding Motion ◽  
Oil Characteristics ◽  
Thermal Ehl ◽  
Wedge Effect

Purpose The influence of the cam angular speed on the pressure, film thickness and temperature profiles at some selected angular positions together with the oil characteristics are investigated. Design/methodology/approach A high-order polynomial cam is used, and thermal elastohydrodynamic lubrication (EHL) calculations are carried out by the multi-grid method and line-line scanning technique. Findings It is found that the film thickness decreases with a decrease in angular speed. The depth of the dimple that occurred in the reverse motion is also reduced because of the recession in the “temperature–viscosity wedge” effect. Originality/value It is revealed that the reduction in the cam angular speed makes the classical big surface dimple evolve into a small centralized dimple during the opposite sliding motion. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0327

Formation Mechanism of Steady Multi-Dimples in Thermal EHL Point Contacts

2003 ◽  
Vol 125 (2) ◽  
pp. 241-251 ◽  
Author(s):  
M. Kaneta ◽  
P. Yang
Keyword(s):  
Steady State ◽  
Flow Model ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Pure Rolling ◽  
Pressure Spike ◽  
Thermal Ehl

With optical interferometry technique, an interesting multi-dimple phenomenon has been discovered under pure-sliding conditions in the point contact between a glass disk and a 3-inch diameter steel ball. At low sliding speeds, two or three stable dimples can be generated in the contact, but at higher sliding speeds, such multi-dimples become unstable. At even higher sliding speeds, however, dimples become stable again, but two dimples become single dimple, or three become two. Numerical solutions of the steady-state thermal elastohydrodynamic lubrication (EHL) theory based on the Newtonian flow model can simulate the stable multi-dimples very well. By changing the slide-roll conditions from pure-rolling to pure-sliding, the theoretical analysis shows clearly that the stable multi-dimples are produced by the thermal effect through the familiar EHL pressure spike.

Reynolds equation and elastohydrodynamic lubrication in metal seals

1976 ◽  
Vol 349 (1658) ◽  
pp. 383-396 ◽  
Keyword(s):  
Numerical Solution ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Hydraulic Jack ◽  
Oil Film ◽  
Metal Seal ◽  
Oil Films ◽  
Theoretical Results ◽  
Film Profile

Oil film profile and pressure distribution between a metal seal and a reciprocating hydraulic jack rod have been measured. A rapidly diverging oil film, which would normally be expected to cause rupture of the fluid and severe cavitation, was observed near the centre of the contact, but the corresponding pressure in this region was found to be high; the two measurements therefore appeared to be incompatible. A re-examination of the inverse Reynolds equation, however, shows that in certain circumstances rapidly diverging oil films are consistent with high values of hydrodynamic pressure; these circumstances are defined. Experimental results are presented which demonstrate that a metal seal may satisfy these conditions. A numerical solution of the elastohydrodynamic equations is described briefly, and the theoretical results are compared with those from the experiments. Reasons why these unusual conditions should exist in the seal are discussed. It is concluded that working in this elastohydrodynamic régime is undesirable.

Effect of Viscous Dissipation on MHD Williamson Nanofluid Flow in a Porous Medium

2019 ◽  
Vol 8 (3) ◽  
pp. 5795-5802 ◽  
Keyword(s):  
Porous Medium ◽  
Steady State ◽  
Numerical Solution ◽  
Viscous Dissipation ◽  
Flow Problem ◽  
Numerical Study ◽  
Steady State Flow ◽  
Nanofluid Flow ◽  
Shooting Technique ◽  
Order Four

The main objective of this paper is to focus on a numerical study of viscous dissipation effect on the steady state flow of MHD Williamson nanofluid. A mathematical modeled which resembles the physical flow problem has been developed. By using an appropriate transformation, we converted the system of dimensional PDEs (nonlinear) into coupled dimensionless ODEs. The numerical solution of these modeled ordinary differential equations (ODEs) is achieved by utilizing shooting technique together with Adams-Bashforth Moulton method of order four. Finally, the results of discussed for different parameters through graphs and tables.

Validation of On-line Respiration Meter and its Applications by Computer Simulation

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1355-1363 ◽  
Author(s):  
C-W. Kim ◽  
H. Spanjers ◽  
A. Klapwijk
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Respiration Rate ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Mass Balances ◽  
Short Term ◽  
Respiration Rates ◽  
On Line ◽  
Made In

An on-line respiration meter is presented to monitor three types of respiration rates of activated sludge and to calculate effluent and influent short term biochemical oxygen demand (BODst) in the continuous activated sludge process. This work is to verify if the calculated BODst is reliable and the assumptions made in the course of developing the proposed procedure were acceptable. A mathematical model and a dynamic simulation program are written for an activated sludge model plant along with the respiration meter based on mass balances of BODst and DO. The simulation results show that the three types of respiration rate reach steady state within 15 minutes under reasonable operating conditions. As long as the respiration rate reaches steady state the proposed procedure calculates the respiration rate that is equal to the simulated. Under constant and dynamic BODst loading, the proposed procedure is capable of calculating the effluent and influent BODst with reasonable accuracy.

Steady-state Security Assessment Based on K-Means Clustering Algorithm and Phasor Measurement Units

2020 ◽  
Vol 13 (4) ◽  
pp. 559-570
Author(s):  
Bassam A. Hemade ◽  
Hamed A. Ibrahim ◽  
Hossam E.A. Talaat
Keyword(s):  
Steady State ◽  
Clustering Algorithm ◽  
System Security ◽  
Phasor Measurement Units ◽  
Operating Conditions ◽  
Security Assessment ◽  
State Security ◽  
Phasor Measurement ◽  
Measurement Units ◽  
Silhouette Analysis

Background: The security assessment plays a crucial role in the operation of the modern interconnected power system network. Methods: Hence, this paper addresses the application of k-means clustering algorithm equipped with Principal Component Analysis (PCA) and silhouette analysis for the classification of system security states. The proposed technique works on three principal axes; the first stage involves contingency quantification based on developed insecurity indices, the second stage includes dataset preparation to enhance the overall performance of the proposed method using PCA and silhouette analysis, and finally the application of the clustering algorithm over data. Results: The proposed composite insecurity index uses available synchronized measurements from Phasor Measurement Units (PMUs) to assess the development of cascading outages. Considering different operational scenarios and multiple levels of contingencies (up to N-3), Fast Decoupled Power Flow (FDPF) have been used for contingency replications. The developed technique applied to IEEE 14-bus and 57-bus standard test system for steady-state security evaluation. Conclusion: The obtained results ensure the robustness and effectiveness of the established procedure in the assessment of the system security irrespective of the network size or operating conditions.

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