The Minimum Film Thickness of Piston Ring and Cylinder Liner Pair in Partial Elastohydrodynamic Lubrication

2009 ◽  
Author(s):  
Chenbo Ma ◽  
Hua Zhu
Keyword(s):  
Film Thickness ◽  
Piston Ring ◽  
Elastohydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Minimum Film Thickness

scholarly journals The Piston Ring-Cylinder Bore Interface Leakage of Bent-Axis Piston Pumps Based on Elastohydrodynamic Lubrication and Rotation Speed

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lvjun Qing ◽  
Lichen Gu ◽  
Yan Wang ◽  
Wei Xue ◽  
Zhufeng Lei
Keyword(s):  
Film Thickness ◽  
Piston Ring ◽  
Rotation Speed ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Proposed Model ◽  
Minimum Film Thickness ◽  
Oil Flow ◽  
Discharge Pressure ◽  
Cylinder Bore

The bent-axis piston pump is the core component of electrohydrostatic actuators (EHA) in aerospace applications, and its wear of key friction interfaces is greatly related to the healthy operation of pumps. The leakage of the piston ring-cylinder bore interface (PRCB), as the important part of the return oil flow of the pump house that commonly assesses the wear of key friction interfaces in piston pumps, is changed with the rotation speed. Thus, the wear of key friction interfaces is usually inaccurate by using the leakage of PRCB. In order to obtain the relationship between the PRCB leakage and the rotation speed, an elastohydrodynamic lubrication model is proposed. First, the proposed model includes a minimum film thickness model of PRCB to analyze the dynamic change of oil film of PRCB when subject to the elastohydrodynamic lubrication. After that, a mathematical model of PRCB is induced by combining the minimum film thickness model with the flow equation, which helps produce the effects of the oil film on the leakage of PRCB. The proposed model is verified by numerical simulation and experiment. The results show that the leakage of PRCB has a negative effect on the return oil flow of the pump case in the range of rotation speed of 700–1300 r/min and discharge pressure of 10–20 MPa. Furthermore, the leakage of PRCB is proportional to the rotation speed, but the return oil flow of the pump case is decreased. The effects of rotation speed are enhanced under the high discharge pressure conditions.

Predictive tool for frictional performance of piston ring-pack/liner conjunction

2019 ◽  
Vol 13 (3) ◽  
pp. 5513-5527
Author(s):  
J. W. Tee ◽  
S. H. Hamdan ◽  
W. W. F. Chong
Keyword(s):  
Film Thickness ◽  
Mathematical Models ◽  
Piston Ring ◽  
Published Data ◽  
Predictive Tool ◽  
Frictional Losses ◽  
Fundamental Understanding ◽  
Minimum Film Thickness ◽  
Piston Ring Pack ◽  
Ring Pack

Fundamental understanding of piston ring-pack lubrication is essential in reducing engine friction. This is because a substantial portion of engine frictional losses come from piston-ring assembly. Hence, this study investigates the tribological impact of different piston ring profiles towards engine in-cylinder friction. Mathematical models are derived from Reynolds equation by using Reynolds’ boundary conditions to generate the contact pressure distribution along the complete piston ring-pack/liner conjunction. The predicted minimum film thickness is then used to predict the friction generated between the piston ring-pack and the engine cylinder liner. The engine in-cylinder friction is predicted using Greenwood and Williamson’s rough surface contact model. The model considers both the boundary friction and the viscous friction components. These mathematical models are integrated to simulate the total engine in-cylinder friction originating from the studied piston ring-pack for a complete engine cycle. The predicted minimum film thickness and frictional properties from the current models are shown to correlate reasonably with the published data. Hence, the proposed mathematical approach prepares a simplistic platform in predicting frictional losses of piston ring-pack/liner conjunction, allowing for an improved fundamental understanding of the parasitic losses in an internal combustion engine.

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

Film thickness in elastohydrodynamically lubricated slender elliptic contacts: Part I – numerical studies of central film thickness

2021 ◽  
pp. 135065012110477
Author(s):  
Marius Wolf ◽  
Sergey Solovyev ◽  
Fatemi Arshia
Keyword(s):  
Film Thickness ◽  
State Of The Art ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Large Parameter ◽  
Numerical Studies ◽  
Minimum Film Thickness ◽  
Subsequent Publication ◽  
New Formula ◽  
Increasing Load

In this paper, analytical equations for the central film thickness in slender elliptic contacts are investigated. A comparison of state-of-the-art formulas with simulation results of a multilevel elastohydrodynamic lubrication solver is conducted and shows considerable deviation. Therefore, a new film thickness formula for slender elliptic contacts with variable ellipticity is derived. It incorporates asymptotic solutions, which results in validity over a large parameter domain. It captures the behaviour of increasing film thickness with increasing load for specific very slender contacts. The new formula proves to be significantly more accurate than current equations. Experimental studies and discussions on minimum film thickness will be presented in a subsequent publication.

Roughness Amplitude Reduction Under Non-Newtonian EHL Conditions

2005 ◽  
Author(s):  
A. D. Chapkov ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Fluctuations ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Quantitative Prediction ◽  
Point Contacts ◽  
Minimum Film Thickness ◽  
Roughness Amplitude ◽  
Average Film Thickness ◽  
Ehl Contact

The influence of surface roughness on the performance of bearings and gears operating under ElastoHydrodynamic Lubrication (EHL) conditions has become increasingly important over the last decade, as the average film thickness decreased due to various influences. Surface features can reduce the minimum film thickness and thus increase the wear. They can also increase the temperature and the pressure fluctuations, which directly affects the component life. In order to describe the roughness geometry inside an EHL contact, the amplitude reduction of harmonic waviness has been studied over the last ten years. This theory currently allows a quantitative prediction of the waviness amplitude and includes the influence of wavelength and contact operating conditions. However, the model assumes a Newtonian behaviour of the lubricant. The current paper makes a first contribution to the extension of the roughness amplitude reduction for EHL point contacts including non-Newtonian effects.

Effect of oil starvation on the isothermal impact problem

2017 ◽  
Vol 232 (10) ◽  
pp. 1332-1339
Author(s):  
Duohuan Wu ◽  
Jing Wang ◽  
Peiran Yang ◽  
Ton Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Gradient ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Pressure ◽  
Numerical Techniques ◽  
Minimum Film Thickness ◽  
The Impact ◽  
Impact Motion ◽  
Impact Problem

In this study, the effect of oil starvation on isothermal elastohydrodynamic lubrication of an impact motion is explored with the aid of numerical techniques. During the impact process, on comparison with the fully lubricated results, the pressure and film thickness are much lower and the entrapped film shape does not happen. The rebound is delayed by the oil starvation assumption. During the rebound process, a periphery entrapment is seen in the starved film thickness distribution. Under the starved condition, the maximum pressure gradient is higher. The central film thickness and minimum film thickness exhibit different variations compared with the results by fully flooded assumption.

The elastohydrodynamic lubrication of piston rings

1983 ◽  
Vol 386 (1791) ◽  
pp. 409-430 ◽  
Keyword(s):  
Film Thickness ◽  
Combustion Chamber ◽  
Diesel Engines ◽  
Elastohydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Piston Rings ◽  
Lubrication Regimes ◽  
Piston Seal ◽  
Cylinder Liners ◽  
Lubricant Viscosity

The piston seal that separates the hostile environment of the combustion chamber from the crankcase that contains the lubricant is an essential machine element in reciprocating engines. The sealing force pressing the piston rings against the cylinder liner varies with the combustion chamber pressure to form an effective self-adjusting mechanism. The conjunctions between piston rings and cylinder liners are thus subjected to cyclic variations of load, entraining velocity and effective lubricant temperature as the piston reciprocates within the cylinder. Recent theoretical and experimental studies have confirmed that piston rings enjoy hydrodynamic lubrication throughout most of the engine cycle, but that a transition to mixed or boundary lubrication can be expected near top dead centre. The purpose of the present paper is to examine the suggestion that elastohydrodynamic lubrication might contribute to the tribological performance of the piston seal, particularly near top dead centre. The mode of lubrication in eight four-stroke and six two-stroke diesel engines is assessed in terms of the dimensionless viscosity and elasticity parameters proposed by Johnson (1970), and the associated map of lubrication régimes. The survey indicates unequivocally that elastohydrodynamic action can be expected during part of the stroke in all the engines considered. In the second part of the paper a detailed examination of the influence of elastohydrodynamic action in one particular engine is presented to confirm the general findings recorded in the study of lubrication régimes. Current analysis of the lubrication of rigid piston rings already takes account of the variation of surface temperature along the cylinder liner and its influence upon lubricant viscosity. It is shown that, when the enhancing influence of pressure upon viscosity is added to the analysis of rigid piston rings, the predicted cyclic minimum film thickness is more than doubled. Full elastohydrodynamic action, involving both local distortion of the elastic solids and the influence of pressure upon viscosity, results in a fourfold increase in film thickness. It is further shown that it is necessary to take account of the variation of squeeze-film velocity throughout the lubricated conjunction at each crank angle if reliable predictions of film shape and thickness are to be achieved. It is thus concluded that the wave of elastic deformation, which ripples up and down the cylinder liners many times each second in diesel engines, together with the associated local elastic deformations on the piston rings themselves, combine with the influence of pressure upon lubricant viscosity to enhance the minimum oil film thickness in the piston seal by elastohydrodynamic action.

3-D Numerical Simulation and Experiment Study on the Wear of Piston Ring-Cylinder Liner

2010 ◽  
Vol 139-141 ◽  
pp. 1036-1039 ◽  
Author(s):  
Jian Ping Zhang ◽  
Yan Kun Jiang ◽  
Xin Liu ◽  
Zhe Lin Dong
Keyword(s):  
Diesel Engine ◽  
Piston Ring ◽  
Elastohydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Effect Of Temperature ◽  
Wear Loss ◽  
Asperity Contact ◽  
Warm Start ◽  
Deformation Equation ◽  
Marine Diesel

Aiming at a large marine diesel engine, a mathematical model for the 3-D elastohydrodynamic lubrication analysis of piston ring-cylinder liner was presented. The average Reynolds equation and asperity contact approach were combined with the elastic deformation equation. The asymmetry in the circumferential direction, gas blowby and the effect of temperature and pressure on the oil density and viscosity were considered. The 3-D wear simulation of piston ring-cylinder liner was performed when the diesel engine was operated under warm start and cold start conditions, respectively. The 3-D distribution rules show that the first gas ring has the biggest wear loss, and the maximum wear loss of cylinder liner occurs in the vicinity of TDCF. Finally, the results matched well with the wear measurements, and it indicates the present method is effective and can help engineers to improve the tribological performance of the diesel engine.

Numerical Simulation on the Lubrication Performance of Surface Textured Piston Rings

2011 ◽  
Vol 199-200 ◽  
pp. 734-738 ◽  
Author(s):  
Qiu Ying Chang ◽  
Xian Liang Zheng ◽  
Qing Liu
Keyword(s):  
Numerical Simulation ◽  
Film Thickness ◽  
Friction Force ◽  
Friction And Wear ◽  
Piston Ring ◽  
Hydrodynamic Lubrication ◽  
Cylinder Liner ◽  
Area Density ◽  
Oil Film ◽  
Lubrication Performance

Surface texturing has been successfully employed in some tribological applications in order to diminish friction and wear. This technology may be used in a piston ring to decrease the friction and wear of the contact between a piston ring and cylinder liner. A numerical simulation of lubrication between a surface textured piston ring and cylinder liner based on the hydrodynamic lubrication theory was conducted. The influence of surface texture parameters on piston ring lubrication performance was obtained by solving the mathematical equations with a multi-grid method. The results show that under the micro-dimple area density of 5%-40% the minimum oil film thickness increases and the dimensionless friction force decreases with the increasing of it. Under the dimple area density of 40%-60%, the minimum oil film thickness and the dimensionless friction force change slightly. Under various dimple area densities the optimum dimple depth at the given working condition in this paper is about 5µm.

Debris Effects on EHL Contact

2000 ◽  
Vol 122 (4) ◽  
pp. 711-720 ◽  
Author(s):  
Young S. Kang ◽  
Farshid Sadeghi ◽  
Xiaolan Ai
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Force Balance ◽  
Time Dependent ◽  
Elasticity Equations ◽  
Minimum Film Thickness ◽  
Bounding Surfaces ◽  
Force Balance Equation ◽  
Ehl Contact

A model was developed to study the effects of a rigid debris on elastohydrodynamic lubrication of rolling/sliding contacts. In order to achieve the objectives the time dependent Reynolds equation was modified to include the effects of an ellipsoidal shaped debris. The modified time dependent Reynolds and elasticity equations were simultaneously solved to determine the pressure and film thickness in EHL contacts. The debris force balance equation was solved to determine the debris velocity. The model was then used to obtain results for a variety of loads, speeds, and debris sizes. The results indicate that the debris has a significant effect on the pressure distribution and causes a dent on the rolling/sliding bounding surfaces. Depending on the size and location of the debris the pressure generated within the contact can be high enough to plastically deform the bounding surfaces. Debris smaller than the minimum film thickness do not enter the contact and only large and more spherical debris move toward the contact. [S0742-4787(11)00501-7]

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