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Oil loss mechanisms in internal combustion engines have been subject to many researches. By the help of technological developments effects of several problems due to oil losses were examined and tried to be reduced. Environmental pollution and performance loss are important issues that oil consumption in internal combustion engines contribute. In this study the effects of individual parameters on the oil accumulation in 2nd land crevice of internal combustion engines, volume between top compression rings, were investigated. The study aimed to investigate the effects of oil film thickness and oil film temperature on the oil accumulation in the 2nd land which contributes to one of the mechanisms of oil consumption in internal combustion engines. Controlled experiments were performed on a modeled piston cylinder assembly. It was seen that oil accumulated in the 2nd land crevice by blow-by gases was affected by the film thickness of lubricating oil and the temperature of the lubricating oil. The amount of oil accumulated increased with increasing oil film thickness. The results also showed that below oil film thickness of 45 &amp / #956 / m / amount of oil accumulated increased with the increase of oil temperature.

<p>Engine development is now driven by cost, performance, governmental regulations and customer demands. Several of the requirements have tribological associations. Tribological improvements which consist in lowering friction and improving wear resistance in engines, will play a major role to increase reliability and life cycle.</p><p>The components studied here are parts of the valvetrain mechanism of heavy-duty Diesel engines. The injection cam is one of the most problematic parts of the camshaft, as it is subjected to high pressures from the fuel injector. Lubrication is of significant importance in the prevention of cam failure caused by wear. However, the satisfactory lubrication of the cam and roller contact has proved to be one of the most difficult tribological design challenges to take up.</p><p>For a lubricated contact, the degree of separation between surfaces has a very strong influence on the type and amount of wear. This degree of separation is termed as specific film thickness ; its value provides a measure of the severity of asperities interaction in the lubricated contact. In this report, attention is drawn on the evaluation of oil film thickness in the cam-roller contact, in order to predict regimes of lubrication and thus to identify the probable wear zones of the injection cam. Then, confrontation with experimental results is performed(observation of worn cam surfaces). Future work to achieve is to discover the influence of the different parameters on oil film thickness, by performing a multivariate analysis. The next step will focus on modelling the wear of injection cams, and finally establishing quantified correlations between wear and specific film thickness.</p>

Engine development is now driven by cost, performance, governmental regulations and customer demands. Several of the requirements have tribological associations. Tribological improvements which consist in lowering friction and improving wear resistance in engines, will play a major role to increase reliability and life cycle. The components studied here are parts of the valvetrain mechanism of heavy-duty Diesel engines. The injection cam is one of the most problematic parts of the camshaft, as it is subjected to high pressures from the fuel injector. Lubrication is of significant importance in the prevention of cam failure caused by wear. However, the satisfactory lubrication of the cam and roller contact has proved to be one of the most difficult tribological design challenges to take up. For a lubricated contact, the degree of separation between surfaces has a very strong influence on the type and amount of wear. This degree of separation is termed as specific film thickness ; its value provides a measure of the severity of asperities interaction in the lubricated contact. In this report, attention is drawn on the evaluation of oil film thickness in the cam-roller contact, in order to predict regimes of lubrication and thus to identify the probable wear zones of the injection cam. Then, confrontation with experimental results is performed(observation of worn cam surfaces). Future work to achieve is to discover the influence of the different parameters on oil film thickness, by performing a multivariate analysis. The next step will focus on modelling the wear of injection cams, and finally establishing quantified correlations between wear and specific film thickness.

This work is focused on the aerodynamics for a proprietary laminar flow airfoil for Unmanned Aerial Vehicle (UAV) applications. The two main focuses are (1) aerodynamic performance at Reynolds number on the order of 10,000, (2) the effect of a conventional hot-wire probe on laminar separation bubbles. For aerodynamic performance, pressure and wake velocity distributions were measured at Re = 40,000 and 60,000 for a range of angles of attack. The airfoil performed poorly for these Reynolds numbers due to laminar boundary layer separation. 2-D boundary layer trips significantly improved the lift-to-drag ratio. For probe effects, three Reynolds numbers were investigated (Re = 100,000, 150,000, and 200,000), with three angles of attack for each. Pressure and surface shear distributions were measured. Flow upstream of the probe tip was not affected. Transition was promoted downstream due to the additional disturbances in the separated shear layer.

This work is focused on the aerodynamics for a proprietary laminar flow airfoil for Unmanned Aerial Vehicle (UAV) applications. The two main focuses are (1) aerodynamic performance at Reynolds number on the order of 10,000, (2) the effect of a conventional hot-wire probe on laminar separation bubbles. For aerodynamic performance, pressure and wake velocity distributions were measured at Re = 40,000 and 60,000 for a range of angles of attack. The airfoil performed poorly for these Reynolds numbers due to laminar boundary layer separation. 2-D boundary layer trips significantly improved the lift-to-drag ratio. For probe effects, three Reynolds numbers were investigated (Re = 100,000, 150,000, and 200,000), with three angles of attack for each. Pressure and surface shear distributions were measured. Flow upstream of the probe tip was not affected. Transition was promoted downstream due to the additional disturbances in the separated shear layer.

Viscous drag reduction plays a vital role in increasing the performance of vehicles. However, there are only so many measurement techniques that can quickly and accurately measure this when compared to pressure drag measurement techniques. The current study makes use of one of the direct and robust measurement techniques that exist, called the Oil Film Interferometry (OFI) to estimate skin friction on the NASA/Virginia Tech BeVERLI (Benchmark Validation Experiment for RANS and LES Investigations) hill. This project aims to develop a detailed database of non-equilibrium, separated turbulent boundary layer flows obtained through wind tunnel experiments for CFD validation. Skin friction measurements are obtained at specific critical locations on the hill and in its close proximity. The challenges involved in obtaining skin friction data from these locations are discussed in detail. Detailed discussions on the experimental setup and data processing methodology are presented. Qualitative and quantitative results from each measurement location are discussed along with uncertainties to explain certain key flow physics. Additionally, skin friction coefficients from selected overlapping measurement locations from another experimental flow measurement technique called Laser Doppler Velocimetry (LDV) are compared with OFI, and a cross-instrument study is performed. Finally, results from well-refined RANS CFD simulations are assessed with the experimental results, and critical improvement areas are identified. / Master of Science / Drag force is a parameter that significantly contributes to the performance efficiency of any vehicle moving in a fluid. This force is categorised into two types - pressure and viscous drag- both of which need to be minimised as much as possible to contribute towards higher vehicle performance. While there are numerous measurement techniques and documentation currently available to measure pressure drag, this is not the case with the measurement of viscous drag. Skin friction measurement directly relates to the estimation of viscous drag, but accurate and quick measurement of this quantity highly challenging with countable measurement techniques currently available. Through this project, BeVERLI (Benchmark Validation Experiment for RANS and LES Investigations), a detailed documentation is developed for accurate measurement of skin friction through Oil Film Interferometry (OFI). The results obtained through this measurement is explained with a detailed experimental procedure as well as using a data processing code. The accuracy of these results are then discussed with the results from another flow measurement technique called Laser Doppler Velocimetry (LDV) and from Computational Fluid Dynamics (CFD).

In case of metalworking operations, the purpose of lubrication is served by a complex mixture of two or more phases, these mixtures are known as metalworking fluids (MWFs). For many decades oil-in-water emulsions have been used as metalworking fluids. The particular advantage of using oil-in-water emulsion in metalworking operations is that it combines the cooling property of water and the lubrication property of the oil. To explain the lubrication mechanism for oil-in-water emulsions as metalworking fluids a variety of models and theories has been proposed. To understand the lubrication mechanism, the role of each ingredient in the tribological process needs to be studied. In the present study a model for lubrication which determines force and proximity regimes of droplets based on the droplet size distribution is proposed. Dynamic light scattering (DLS) is used to characterize the emulsions. The small droplets are found to be the ones which enhance lubricity. DLVO (Derjaguin-Landau-Verwey-Overbeek) theory is used to validate the results. The concentration and type of surfactant is found to be the performance controlling parameter. A further analysis of the three interfacial energetics; oil/water, oil/substrate, water/substrate, is studied in the presence and absence of surfactants with the help of a Goniometer, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM). Such energetics reflects the rate at which the excess surfactant molecules accumulate at the water/oil interface and desorb into the phases. The tribological response is recorded using AFM and the nanotribometer (NTR). Frictional response of the chemisorbed self-assembled monolayer of surfactant (sodium oleate) on the steel substrate reflects that a tribofilm helps in lubricating the contact under boundary lubrication by creating a low shear strength material. Water being the continuous phase in oil/water emulsion a thin water layer adjacent to steel substrate is always present. This thin layer on the solid substrate acts as a barrier to the lubricating oil droplets to reach the metal surface. The focus of the present work is also to investigate conditions which permit the disjoining of the water film to allow the oil to lubricate the metal substrate. AFM is used to study the interaction force between an oil droplet and the steel substrate through water. An oil encapsulated SiO2 colloidal probe used to simulate the oil droplet. The charge regulatory status of the substrates and interfaces are found to be critical in mapping the force characteristics when DLVO interaction is considered. The condition for activation of non-DLVO (hydration, hydrophobic, capillary) forces are also identified and found to be dependent on the physical states of surfaces. Disjoining of the thin film can be controlled by selecting surfactants based on interfacial energetics and attractive force characteristic can be achieved to facilitate lubrication.

No description available.

High-Frame-Rate Oil Film Interferometry Jonathan Charles White This thesis presents the design and implementation of a high-frame-rate oil film interferometry technique (HOFI) used to directly measure skin friction in time dependent flows. Experiments were performed to determine the ability of a high-speed camera to capture oil film interferometry images. HOFI was found to be able to capture these interferometry images at frequencies up to 105 Hz. Steady laminar and turbulent flows were tested. Transient flows tested consisted of a wind tunnel ramping up in velocity and a laminar boundary layer which was intermittently tripped to turbulence by puffing air out of a pressure tap. Flow speeds ranged from 0 to 108 ft/sec and 10 and 50 cSt Dow Corning 200 dimethylpolysiloxane silicone oil was used. The skin friction was determined from the rate of change of the height of the oil film using lubrication theory. The height of the oil film was determined from the high speed camera interferogram images using a MATLAB script which determined fringe spacing by fitting a four-parameter sine wave to the intensity levels in each image. The MATLAB script was able to determine the height of the oil film for thousands of interferogram images in only a few minutes with sub-pixel error in fringe spacing. The skin friction was calculated using the oil film height history allowing for the direct measurement of skin friction in time dependent flows.