Impact of fuel oxygen on morphology and nanostructure of soot particles from a diesel engine

© 2018 Australasian Fluid Mechanics Society. All rights reserved. Diesel engines are often preferred over gasoline engines because of their fuel efficiency and reliability; however, there are significant issues around their environmental pollution which is controlled by emission regulations. To meet the ever more stringent regulations, reduction in diesel particle matter emissions can be addressed by minimising particle formation and by optimising particle oxidation in the combustion chamber and in the exhaust and diesel particulate filter systems. Soot formation and oxidation processes are the predecessors to the physicochemical properties of diesel particulate matter and are characterised by morphology and nanostructure. These characteristics principally include primary particle size, fractal dimension, fringe length, fringe tortuosity and fringe separation distance. Thus, understanding of these characteristics is necessary for an efficient reduction of particle emissions from diesel engines. Furthermore, understanding these characteristics is important because they affect the aerodynamic behaviour of the diesel particulate matter in the exhaust system, diesel particulate filter systems, and the environment. This study aims to investigate the impact of butanol on morphology and nanostructure of soot particles from a 5.9 L turbocharged diesel engine at different engine loads. The oxygen content in the fuel was varied from 0% to 4.32% and 6.48% by using diesel, 20 and 30 % of butanol blends with diesel (Bu0, Bu20 and Bu30). The results indicate that the oxygenated fuels made by blending with butanol had a significant impact on the aerodynamic behaviour of soot particles. This could result in different lung deposition patterns and therefore different toxicity, as well as the change in the diesel particle filters’ filtration efficiency. As oxygen content increased, the corresponding nano-structural characteristics of fringe length and separation distance increased, whereas fringe tortuosity decreased. The change of the nanostructure properties will further influence the diesel particle filters through the changes in the regeneration processes, and will therefore have a significant influence on implementing these fuels in modern diesel vehicles.