Innovative Strategies for Water-in-Diesel Emulsion Separation

The separation of water and particles from diesel is becoming an increasingly pressing issue for the diesel engine. This is as a result of the increase in environmental constraints forcing engine manufacturers to reduce the emissions of their engines (exhaust gasses and particulate matter). In order to do this high-pressure common rail systems were introduced, the increased pressure meant that the tolerances within the engine were made to be tighter. The tighter tolerances mean that the removal of particles and water to avoid the effect of abrasion and corrosion is even more imperative.
This thesis will first examine filters that have been fouled in real engines. The filters have been fouled in three different fuel markets (Sweden petroleum, Brazil petroleum and Brazil biodiesel). The chemical physical changes to the filter as a result of the fouling have been examined. Any differences between the different fuel markets have been noted. It was shown conclusively that there are two main factors that affect the water separation efficiency, the surface free energy and the trans filter pressure (shear force at the pore walls) The findings of this informed the development of a new coating intended to not only increase the immediate water separation efficiency of the filter, but the end-of-life performance as well.
The coating was formed using a modified Stöber process, in which a hydrophobic functionalising agent is used to create hydrophobic microspheres that were applied to the surface of the filter. Three different functionalising agents were examined, two silane-based agents and one acid based. It is shown that it is possible to create superhydrophobic silica spheres using a facile one-pot method for all the functionalising agents examined. It was found that the fluorine containing silane was the most hydrophobic followed by the hydrocarbon-based silane and finally the acid based functionalising agent.
Using a flow rig the immediate effect of the coatings was examined, this will be the most effective method for imitating the real running conditions for the filter. It is shown that all the coatings examined resulted in an increased instantaneous water separation efficiency when compared to an uncoated sample. A novel accelerated fouling technique was developed, this was vital in order to determine the end-of-life performance in a lab environment. It is shown that this technique is representative of what is seen in the samples returned from the field when applied to an uncoated sample. Once the filters were fouled, they were again tested in the flow rig to determine their end-of-life performance. The coated filters performed significantly better than the filter that was uncoated. The coatings formed with the fluorine containing functionalising agent had the greatest improvement when compared with the uncoated filter.