Influence of Lubricant Inlet Film Thickness on Elastohydrodynamically Lubricated Contact Starvation

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
David Kostal ◽  
Petr Sperka ◽  
Petr Svoboda ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Flow Resistance ◽  
Experimental Validation ◽  
Theoretical Models ◽  
Research Area ◽  
Theoretical Studies ◽  
Point Contacts ◽  
Lubricated Contact ◽  
Side Flow

The paper deals with an experimental study of an elastohydrodynamic contact under insufficient lubricant supply. Theoretical studies published in this research area focus mainly on the development of theoretical models, and there is a lack of experimental validation of the theoretical models. This paper presents original experimental results and aims to describe the starvation severity level as a function of the inlet film thickness and contact geometry. Experimental data are compared with an analytical model for point contacts published by Chevalier. The study was also extended to elliptical contacts to achieve a comparison with the different parameters of the side-flow resistance used by Damiens. Both models agree well with the experiments.

An Experimental Evaluation of the Hamrock and Dowson Minimum Film Thickness Equation for Fully Flooded EHD Point Contacts

1981 ◽  
Vol 103 (2) ◽  
pp. 284-294 ◽  
Author(s):  
K. A. Koye ◽  
W. O. Winer
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Film Thickness ◽  
Experimental Evaluation ◽  
Point Contact ◽  
Major Axis ◽  
Point Contacts ◽  
Lubricant Film Thickness ◽  
Minimum Film Thickness ◽  
Ellipticity Ratio

Fifty-seven measurements of the minimum lubricant film thickness separating the elastohydrodynamically lubricated point contact of a steel crowned roller and a flat sapphire disk were made by an optical interferometry technique. The data collected were used to evaluate the Hamrock and Dowson minimum EHD film thickness model over a practical range of contact ellipticity ratio where the major axis of the contact ellipse is aligned both parallel and perpendicular to the direction of motion. A statistical analysis of the measured film thickness data showed that the experimental data averaged 30 percent greater film thickness than the Hamrock and Dowson model predicts.

Film Thickness in Starved EHL Point Contacts

1998 ◽  
Vol 120 (1) ◽  
pp. 126-133 ◽  
Author(s):  
F. Chevalier ◽  
A. A. Lubrecht ◽  
P. M. E. Cann ◽  
F. Colin ◽  
G. Dalmaz
Keyword(s):  
Film Thickness ◽  
Numerical Study ◽  
Thickness Distribution ◽  
Experimental Studies ◽  
Thickness Reduction ◽  
Complete Analysis ◽  
Point Contacts ◽  
Governing Parameter ◽  
Experimental Findings ◽  
Side Flow

This paper presents a numerical study of the effects of inlet supply starvation on film thickness in EHL point contacts. Generally this problem is treated using the position of the inlet meniscus as the governing parameter; however, it is difficult to measure this in real applications. Thus, in this paper an alternative approach is adopted whereby the amount of oil present on the surfaces is used to define the degree of starvation. It is this property which determines both meniscus position and film thickness reduction. The effect of subsequent overrollings on film thickness decay can also be evaluated. In the simplest case a constant lubricant inlet film thickness in the Y direction is assumed and the film thickness distribution is computed as a function of the oil available. This yields an equation predicting the film thickness reduction, with respect to the fully flooded value, from the amount of lubricant initially available on the surface, as a function of the number of overrollings n. However, the constant inlet film thickness does not give a realistic description of starvation for all conditions. Some experimental studies show that the combination of side flow and replenishment action can generate large differences in local oil supply and that the side reservoirs play an important role in this replenishment mechanism. Thus the contact centre can be fully starved whilst the contact sides remain well lubricated. In these cases, a complete analysis with a realistic inlet distribution has been carried out and the numerical results agree well with experimental findings.

scholarly journals Theoretical and Experimental Analysis of Aerodynamic Noise in Small Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 727
Author(s):  
José R. Dorrego ◽  
Armando Ríos ◽  
Quetzalcoatl Hernandez-Escobedo ◽  
Rafael Campos-Amezcua ◽  
Reynaldo Iracheta ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Speed ◽  
Wind Turbine ◽  
Experimental Validation ◽  
Sound Pressure ◽  
Turbine Blades ◽  
Theoretical Models ◽  
Maximum Error ◽  
Aerodynamic Noise ◽  
Small Wind Turbine

This paper presents an analysis of sound pressure levels through theoretical modeling and experimental validation in a 1 kW small wind turbine. The models used in the theoretical analysis are BPM (Brooks, Pope, and Marcolini) and BM (Brooks and Marcolini), where wind turbine blades are divided in sections, and each section has its own contribution with respect to the total emitted sound pressure level. The noise propagation study and its experimental validation were accomplished within the requirements of the standard IEC 61400-11 Ed.3 and the standard NOM-081-SEMARNAT-1994. The comparative study of theoretical and experimental results showed that the BPM and BM methods have a maximum error of 5.5% corresponding to the rated wind speed of 10 m/s. However, at low wind speeds, the theoretical models fit well to experimental data, for example, in the range from 5 to 8 m/s. The experimental data showed that the rotor’s aerodynamic noise is more evident at low wind speed, because under these conditions, environmental noise is much less than wind turbine noise. Finally, to prevent possible negative effects on people’s health, there is a recommended minimum and suitable distance between small wind turbine installations and buildings.

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

scholarly journals Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1205
Author(s):  
Ruiqi Wang ◽  
Riqiang Duan ◽  
Haijun Jia
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Experimental Validation ◽  
Particle Image ◽  
Velocity Fields ◽  
Number Range ◽  
Comparison Results ◽  
Image Velocimetry ◽  
Experimental Particle

This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6–52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt’s theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method’s fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.

Effect of Rolling Velocity and Maximum Hertzian Pressure on Fluid Film in Steady State EHL Line Contact with Rough Surface and Linear Piezoviscosity

2014 ◽  
Vol 592-594 ◽  
pp. 1371-1375
Author(s):  
Nitesh Talekar ◽  
Punit Kumar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Rough Surface ◽  
Computer Code ◽  
Fluid Film ◽  
Line Contact ◽  
Rolling Velocity ◽  
Load Carrying ◽  
Lubricated Contact

Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (ph) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

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