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The objective of this investigation is to characterize the influence of injection parameters and spray-wall interaction on atomization and gas entrainment processes of high-pressure non-evaporative sprays injected into a high-pressure vessel using several imaging techniques. The effects of injection pressure on the droplet distribution, size and velocity were quantified using single and double nano second exposure photography techniques. A laser-sheet imaging method was employed to measure the two-dimensional gas velocity around the spray and to clarify the effects of the above parameters on the gas entrainment into the impinging sprays. It was found that increasing the injection pressure causes an increase in droplet number in both free and wall-jet regions of the sprays. Spray-wall impingement creates a large-scale gas vortex around the spray, which promotes the gas entrainment into sprays typically at the impinging zone, and it also affects the spatial distribution of droplets.

The aim of this study is to develop a plasma-assisted after-treatment system for simultaneous reduction of NOx and PM in diesel exhaust, which is less sensitive to the fuel sulfur. The work presented focuses on development of a high-frequency dielectric barrier discharge reactor for oxidation of NO to NO2 in diesel exhaust and low-temperature oxidation of diesel soot with NO2. The first part of this paper describes the combustion characteristics of carbonaceous matters with pure NO2 and discusses the difference when oxygen is used as oxidation agent. The second part focuses on the development of a high-frequency dielectric barrier plasma reactor and describes the effects of plasma reactor configuration, energy density and gas composition on the NO conversion into NO2, and last part describes the soot oxidation with the plasma gas. The results reveal that NO can be efficiently oxidized into NO2 using the developed plasma reactor.

A fundamental study on spray behavior for small quantity injection under high boosting and high temperature conditions was carried out by applying dual nano-spark shadowgraph photography method to constant volume spray chamber filled with inert gas. The study showed macro-scale and micro-scale spray structures and dynamic changes of diesel spray affected by ambient density and temperature right after the pilot injection. Detailed observation and analysis of the images showed that high density surrounding gas decreases the mainstream velocity of the spray after injection, which restrains air entrainment into the spray. There is a change of flying direction of the droplets at spray boundary under high density condition. Many droplets move outward from the spray after the lapse of time. Spray evaporation is promoted by vaporization of droplets at spray boundary. High density condition greatly promotes droplets evaporation at spray boundary.