scholarly journals Effect of the Texture Shape Aspect Ratio on Friction Reduction in a Hydrodynamic Lubrication Regime

2017 ◽  
Vol 16 (2) ◽  
pp. 63-68 ◽  
Author(s):  
Daehun Lee ◽  
◽  
Sang-Shin Park ◽  
Tae Jo Ko ◽  
Jaesool Shim
Keyword(s):  
Aspect Ratio ◽  
Hydrodynamic Lubrication ◽  
Friction Reduction ◽  
Lubrication Regime

Experimental Investigation of Surface Modifications for Piston-Ring/Cylinder-Liner Friction Reduction

2008 ◽  
Author(s):  
Marko S. Cater ◽  
Nathan W. Bolander ◽  
Farshid Sadeghi
Keyword(s):  
Hydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Surface Modifications ◽  
Friction Reduction ◽  
Analytical Models ◽  
Reciprocating Motion ◽  
Lubrication Regime ◽  
Average Coefficient ◽  
Lubrication Condition ◽  
Micro Dimples

Micro-dimples on the surface of lubricated sliding contacts can act as mini-hydrodynamic bearings. The pressure generated within these dimples tends to separate the surfaces and reduce the number of asperities in contact, thereby lowering the average coefficient of friction and moving the lubrication condition to the more stable hydrodynamic lubrication regime. An experimental study on the effects of laser surface modifications for friction reduction is presented through the use of several experimental test rigs. Micro-dimples were generated with an Nd-YAG laser on the surface of flat samples for testing in constant speed and reciprocating motion test rigs. These simple geometries were used to investigate the phenomenon and validate existing analytical models. Modifications to the top dead center region of an actual cylinder liner were evaluated with a motored, small-engine dynamometer. The results demonstrated that measurable friction reductions can be achieved using this approach.

scholarly journals The Rotating Liner Engine (RLE) Diesel Prototype: Reducing Internal Engine Friction by about 40% under Idle Conditions

2021 ◽  
Vol 11 (2) ◽  
pp. 779
Author(s):  
Dimitrios Dardalis ◽  
Amiyo Basu ◽  
Matt J. Hall ◽  
Ronald D. Mattthews
Keyword(s):  
Internal Combustion Engines ◽  
Hydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Friction Reduction ◽  
Contact Boundary ◽  
Metal Contact ◽  
Load Testing ◽  
Gas Leakage ◽  
Brake Mean Effective Pressure ◽  
Economy Benefit

The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2–4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential to eliminate the metal-to-metal contact/boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high. This paper describes the Diesel RLE prototype constructed from a Cummins 4BT and the preliminary observations from initial low load testing. The critical technical challenge, namely the rotating liner face seal, appears to be operating with negligible gas leakage and within the hydrodynamic lubrication regime for the loads tested (peak cylinder pressures of the order of 100 bar) and up to about 10 bar BMEP (brake mean effective pressure). Preliminary testing has proven that the metal-to-metal contact in the piston assembly mostly vanished, and a friction reduction at idle conditions of about 40% as extrapolated to a complete engine has taken place. It is expected that as the speed increases, the friction reduction percentage will diminish, but as the load increases, the friction reduction will increase. The fuel economy benefit over the US Heavy-Duty driving cycle will likely be of the order of 10% compared to a standard engine.

A Theory of Mixed Lubrication

1972 ◽  
Vol 186 (1) ◽  
pp. 421-430 ◽  
Author(s):  
H. Christensen
Keyword(s):  
Hydrodynamic Lubrication ◽  
Dynamic Properties ◽  
Mixed Lubrication ◽  
Rapid Rise ◽  
Operating Characteristics ◽  
Lubrication Regime ◽  
Lubricated Contact ◽  
Mixed Lubrication Regime ◽  
Lubrication Conditions ◽  
Lubrication Properties

The phenomena observed when a lubricated contact or bearing is operating under mixed lubrication conditions are assumed to arise from an interaction of the surface asperities or roughness as well as from hydro-dynamic action of the sliding surfaces. It is shown how one of the previously published stochastic models of hydrodynamic lubrication can be extended or generalized to deal with mixed lubricating conditions. As an illustration of the application of the theory to a concrete example the influence on the operating characteristics of a plane pad, no side-leakage bearing is analysed. It is found that in the mixed lubrication regime friction is mainly controlled by the boundary lubrication properties of the liquid–solid interface. Load, on the other hand, is almost entirely controlled by the hydro-dynamic properties of the bearing. It is demonstrated how transition to mixed lubrication conditions will cause a rapid rise in friction thereby producing a minimum point in the Stribeck type diagram.

scholarly journals Theoretical and Experimental Investigations on Transient Run-Up Procedures of Journal Bearings Including Mixed Friction Conditions

Lubricants ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 105 ◽  
Author(s):  
Maximilian Prölß ◽  
Hubert Schwarze ◽  
Thomas Hagemann ◽  
Philipp Zemella ◽  
Philipp Winking
Keyword(s):  
Experimental Data ◽  
Energy Equation ◽  
Hydrodynamic Lubrication ◽  
Frictional Coefficient ◽  
Journal Bearings ◽  
Numerical Code ◽  
Experimental Investigations ◽  
Lubrication Regime ◽  
Mixed Friction ◽  
Run Up

This paper focuses on the operating behavior of journal bearings for industrial machinery application during run-ups. For this purpose, a numerical simulation code that is based on a two-dimensional extended and generalized Reynolds equation and a full three-dimensional energy equation, was advanced by a theoretical model considering the effects of mixed friction and warming of journal components during start-up. The mixed friction routine contained the elastic half-spaces model proposed by Boussinesq, which considers the influence of rough surfaces by implementing flow factors and calculates additional stiffness and dissipation in areas with solid interactions. Furthermore, a transient term was added in the energy equation to consider the thermal inertia of journal, and bearing to ensure a realistic heating during run-ups. Results of the prediction were compared to experimental data taken from a special test rig built up for validation procedures. Besides the conventional sensors for temperature, oil flow, and relative motion between shaft and stator, a contact voltage measurement was installed to determine the intensity of mixed friction. The evaluation of experimental data by Stribeck curves, based on a shaft torsion measurement, indicated a significant influence of run-up time on frictional moment. The friction coefficient of the rotor bearing system was strongly influenced by the run-up time. A short run-up time reduced the frictional coefficient in the mixed lubrication regime while the opposite behavior was observed in the hydrodynamic lubrication regime. The numerical code predicted these tendencies in good agreement with experimental data, however, only if the transient energy model was applied.

Modelling Acoustic Emissions induced by dynamic fluid-asperity shearing in hydrodynamic lubrication regime

2021 ◽  
Vol 153 ◽  
pp. 106590 ◽  
Author(s):  
Jiaojiao Ma ◽  
Hao Zhang ◽  
Zhanqun Shi ◽  
Fulei Chu ◽  
Fengshou Gu ◽  
...  
Keyword(s):  
Hydrodynamic Lubrication ◽  
Acoustic Emissions ◽  
Lubrication Regime

Hydrodynamic Performance Produced by Nanotexturing in Submicrometer Clearance With Surface Roughness

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Tomoko Hirayama ◽  
Heinosuke Shiotani ◽  
Kazuki Yamada ◽  
Naoki Yamashita ◽  
Takashi Matsuoka ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Hydrodynamic Lubrication ◽  
Surface Texturing ◽  
Wave Model ◽  
Physical Models ◽  
Hydrodynamic Performance ◽  
Stribeck Curve ◽  
Spiral Groove ◽  
Transition Speed ◽  
Lubrication Regime

Surface texturing is a promising way to expand the hydrodynamic lubrication regime and thereby modify the tribological properties of sliding surfaces. Spiral-groove textures in particular have attracted much attention over the past several decades because they produce a thicker lubrication film in the gap. However, no research has been reported on the effect of periodic texturing with a several 100 nm depth on hydrodynamic performance in submicrometer clearance with surface roughness. The purpose of the study reported here was to investigate the effect of such nanotexturing on hydrodynamic performance. This was done by conducting ring-on-disk friction tests, focusing on the existence of surface roughness in the narrow clearance. The samples were rings with various degrees of surface roughness and disks with spiral-groove textures produced by femtosecond laser processing. The friction coefficients experimentally obtained were plotted as a Stribeck curve and compared with a theoretical one calculated using a Reynolds equation formulated from two physical models, the Patir–Cheng average flow model and a sinusoidal wave model. The results showed that surface roughness did not affect the friction coefficient in the hydrodynamic lubrication regime. However, the hydrodynamic lubrication regime gradually shrank with an increase in surface roughness, and mild transitions to the mixed lubrication regime were observed at higher rotational speeds. The minimum clearances reached at the transition speed were almost the same, about 200–300 nm, for all experiments regardless of surface roughness.

scholarly journals A coupled approach for rolling contact fatigue cracks in the hydrodynamic lubrication regime: The importance of fluid/solid interactions

Wear ◽  
2011 ◽  
Vol 271 (5-6) ◽  
pp. 720-733 ◽  
Author(s):  
Robbie Balcombe ◽  
Mark T. Fowell ◽  
Andrew V. Olver ◽  
Stathis Ioannides ◽  
Daniele Dini
Keyword(s):  
Hydrodynamic Lubrication ◽  
Fatigue Cracks ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Lubrication Regime

scholarly journals Theoretical model of the effect of dimple on friction behavior in hydrodynamic lubrication regime

2021 ◽  
Vol 264 ◽  
pp. 04076
Author(s):  
Auezhan Amanov ◽  
Xasan Turkmenov
Keyword(s):  
Theoretical Model ◽  
Hydrodynamic Lubrication ◽  
Renewable Energy Sources ◽  
Point Contact ◽  
Friction Behavior ◽  
Mechanical Parts ◽  
Research Areas ◽  
Lubrication Regime ◽  
Rigid Smooth ◽  
Film Lubrication

In this paper, full-film lubrication between the rigid smooth and dimpled surfaces was addressed. A theoretical model is developed to study the effect of a dimple on friction where the smooth surface is rotating while the dimpled surface is at rest. To simplify the problem, the magnified dimple cell is investigated along with some assumptions. Because dimples deploy periodically along with the x and y directions, the lubricant pressure also deploys periodically. A theoretical model can be developed for one cell and then extended to the whole surface. The main goal of this study is to understand the dimple effect on friction in a hydrodynamic lubrication regime. The main applications of this model are several types of bearings (point contact, line contact etc.) and mechanical parts where two surfaces interact in relative motion. Findings the optimum dimensions for the dimples also seem to be one of the interesting research areas in mechanization of agricultural and renewable energy sources.

scholarly journals Numerical investigation of the tribological performance of micro-dimple textured surfaces under hydrodynamic lubrication

2017 ◽  
Vol 8 ◽  
pp. 2324-2338 ◽  
Author(s):  
Kangmei Li ◽  
Dalei Jing ◽  
Jun Hu ◽  
Xiaohong Ding ◽  
Zhenqiang Yao
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Stokes Equations ◽  
Hydrodynamic Lubrication ◽  
Friction Pair ◽  
Hydrodynamic Pressure ◽  
Tribological Performance ◽  
Textured Surfaces ◽  
Texture Density ◽  
Micro Dimple

Surface texturing is an important approach for controlling the tribological behavior of friction pairs used in mechanical and biological engineering. In this study, by utilizing the method of three-dimensional computational fluid dynamics (CFD) simulation, the lubrication model of a friction pair with micro-dimple array was established based on the Navier–Stokes equations. The typical pressure distribution of the lubricant film was analyzed. It was found that a positive hydrodynamic pressure is generated in the convergent part of the micro-dimple, while a negative hydrodynamic pressure is generated in the divergent part. With suitable parameters, the total integration of the pressure is positive, which can increase the load-carrying capacity of a friction pair. The effects of the micro-dimple parameters as well as fluid properties on tribological performance were investigated. It was concluded that under the condition of hydrodynamic lubrication, the main mechanism for the improvement in the tribological performance is the combined effects of wedging and recirculation. Within the range of parameters investigated in this study, the optimum texture density is 13%, while the optimum aspect ratio varies with the Reynolds number. For a given Reynolds number, there exists a combination of texture density and aspect ratio at which the optimum tribological performance could be obtained. Conclusions from this study could be helpful for the design of texture parameters in mechanical friction components and even in artificial joints.

The Role of Geometrical Parameters in the Lubrication of the Swiss Lever Escapement

2021 ◽  
Vol 88 (6) ◽  
Author(s):  
Alejandro Roda-Buch ◽  
Valentine A. M. Magnin ◽  
Sandra Guadalupe Maldonado ◽  
Stefano Mischler
Keyword(s):  
Hydrodynamic Lubrication ◽  
Contact Forces ◽  
Geometrical Parameters ◽  
Inverse Dynamic ◽  
Technical Parameters ◽  
Lubrication Regimes ◽  
Multibody Model ◽  
Lubrication Regime ◽  
The Coefficient Of Friction

Abstract The lubrication regimes of a contact pair escapement-ruby pallet of a Swiss lever escapement have been investigated combining the theory of fluid lubrication with a well-established kinematic and inverse dynamic multibody model. The kinematic analytical results have been confronted with experimental measurements. The developed model allows to easily obtain, for the three operating phases of the Swiss lever escapement, the relative speed and the contact forces and, by considering a hydrodynamic lubrication regime, the lubricant minimum film thickness and the coefficient of friction. The presented formulation allows to study the influence of crucial technical parameters in the Swiss lever escapement lubrication. The spout radii of curvature have been identified as the optimal parameters to control the lubrication regimes in the pallet/escapement contacts. In that sense, an interesting result is that the lubrication regime moves away from the boundary lubrication by increasing these radii.

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