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Numerous engineering applications have been proposed to exploit the load-carrying and non-contact nature of noncoalescing and nonwetting systems. One such application is a lab-on-a-chip , or LOC, in which liquid samples would be delivered from point-to-point by sliding over a film of air without requiring either the large driving forces required to pump liquid through a microchannel or liquid-solid contact that could lead to sample-to-sample contamination. Due to the axisymmetry of the flow fields in both the lubricating gas and droplet associated with a stationary nonwetting droplet, such a situation has a vanishing coefficient of static friction. However, once motion is imparted, droplet deformation requires that a force be applied to sustain such motion. The program of research in this dissertation focuses on investigating the lubrication force between a drop of silicone oil and a moving unwetted substrate due to the presence of a gas lubricating film driven by a rotating disk. The frictional (or lubrication) force was measured using an optical-lever technique as a function of: (1) linear velocity of the moving solid; (2) relative displacement of the drop toward the solid; (3) drop volume; and (4) viscosity. The data reveal an increase in magnitude of the measured force with either increasing relative squeezing of the drop against the glass or increasing speed of the rotating disk. Contrary to initial expectations, no pattern could be isolated regarding drop volume or viscosity of the oil. The experimental data collected will serve to validate numerical work as further models are developed.

The development of Environmentally Adapted Lubricants (EALs) and their use has been gaining momentum over the last decade. It has been shown that raw EALs degrade in the environment in about one tenth the time of an equivalent mineral based lubricant. Estimates and findings such as these serve to highlight the potential benefits of the EAL products, it is also important however to investigate the by-products of their use to ensure that the benefits are not cancelled by an increase of, for instance, combustion by-products. This thesis compares the emissions from a two-stroke outboard engine when using an EAL and an equivalent mineral lubricant, where the primary objective of the study is to characterise and quantify the pollutants that remain within the water column after combustion. To accomplish this, tests were conducted both in the laboratory (freshwater) and in the field (seawater) for a range of throttle settings. A 1.9kW two-stroke outboard engine was set-up in a test tank and water samples were taken from the tank after the engine had been run for a period at each of the throttle settings. The tests were repeated for a 5.9kW four-stroke engine, however, the experiments were only conducted in the laboratory (freshwater) and using only a standard mineral lubricant. Statistical analyses of the results were conducted using a Principal Components Analysis (PCA). A simple dilution model was used to estimate the initial outboard engine emission concentrations, which was extended to determine the concentrations at distances of 1, 10 and 100 metres from the source. An investigation of the Total Toxicity Equivalence of the PAH pollutant concentrations (TEQPAH) was conducted using Toxicity Equivalent Factors (TEFs). Results for both types of engine and in both fresh and seawater showed that even the initial concentrations at the source, in almost all instances, were well below the ANZECC water quality guidelines trigger levels. At a distance of 1 metre from the source all concentrations were well below, and therefore, the Total Toxicity Equivalents of the PAHs were found to be even lower. It is concluded that the emissions from a single outboard engine when using either an EAL or a mineral based lubricant are similar. However, the use of EALs has further reaching advantages in that spilt raw lubricants will degrade in the environment up to 10 times faster than a mineral lubricant. Also EALs are less toxic to aquatic and marine organisms and therefore the benefits of using them has to be viewed from a wider perspective. The results in this thesis for a single outboard engine now form the basis for a more detailed environmental assessment of their impacts.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 244-259).

Thesis (Ph. D.)--Universiteit Twente, 1987.