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A single cylinder engine was modified to study the potential of reducing fuel consumption and emissions in stratified, direct injection, spark ignition engines with the use of air-assisted nozzles. The spray angle of the nozzle was varied (60° and 90°), and two injection strategies were investigated: (I) the fuel was injected in the nozzle prior to transportation into the chamber via the air flow and (II) the fuel was injected directly into the air flow. The results of the engine experiments were compared with the spray characteristic of each configuration. To facilitate the comparison, two-dimensional images of the sprays were recorded under atmospheric conditions. The fuel was visualized using Planar Laser-Induced Fluorescence (PLIF). The optical chamber was equipped with three optical accesses and a standard injection system from a production engine.

In this study, we report experimental investigations on the air/fuel distribution in the combustion chamber of a spark ignition engine during the first stage of combustion, and prior to ignition. Several modifications were made to a single cylinder to give optical access to the combustion chamber via a glass cylinder. These modifications included the addition of electro-magnetic valves, with a strategic placement for internal exhaust gas recirculation (EGR), and a quartz glass cylinder for optical access. With the placement and timing of the electro-magnetic valves and exhaust gas recirculation rates up to 40 % mass, the engine's combustion process was greatly improved. These improvements included a reduction of fuel consumption by 8 % and a reduction in NOx emissions of 90 %. The flow of air/fuel mixture into the combustion chamber was visualized by Planar Laser-Induced Fluorescence (PLIF) and captured as 8-bit gray scale images.