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Numerical calculations based on large eddy simulation were performed in order to investigate mixture formation, ignition, and combustion processes in a diesel spray formed by fuel injection into a constant-volume vessel under high-temperature and high-pressure conditions. Fuel concentration distributions in a spray and local non-homogeneous mixture distributions were compared with experimental results to verify the accuracy of the calculations. In addition, calculations were carried out to examine the effect of injection parameters, namely, injection pressure and nozzle orifice diameter. Ignition and combustion processes were also investigated using Schreiber's model for calculating the progress of oxidation reactions.

A single nano-spark back light photography method has been developed to record the image of non-evaporating diesel sprays injected into high pressure nitrogen gas. Relatively clear image of fine droplets and spray was obtained. An image analysis method has been developed to quantify the droplet characteristics which are in focus, such as droplet size and shape. Spatial and temporal distribution of droplets has been clarified. It was observed that the number of droplets around the nozzle tip region decreases by time, however a large number of droplets were observed at X=13∼25 mm from nozzle tip at t=300∼700 μs from injection start. Double-nano spark photography of diesel sprays was carried out and relatively clear double exposure images of droplets were obtained on the same film. Two dimensional size and velocity measurement of droplets were simultaneously carried out based on these photographs.

Single-excite dual-fluorescence PLIF was applied to a diesel spray of a two-component fuel, the components of which have different boiling points. The spray was formed by injecting fuel into a constant-volume vessel under high-temperature, high-pressure conditions. The fluorescence emitted from the two tracers for the fuel was optically separated to measure the concentration of each component. Mixture formation was investigated based on the concentration distributions of each fuel component. The fuel concentration was derived based on the change in fluorescence intensity due to temperature and the assumption of adiabatic mixing of fuel and the surrounding fluid. The variation in the mixture distribution due to differences in the vaporization characteristics was investigated, and the results revealed that the two components have similar distribution. The concentration of the high-boiling-point component increased upstream region in a spray.