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Auto-ignition of a non-homogeneous mixture was fundamentally investigated by means of a numerical calculation based on chemical kinetics and the stochastic approach. In the present study, the auto-ignition process of n-heptane is calculated by means of a reduced mechanism developed by Seiser et. al. The non-uniform states of turbulent mixing are statistically described using probability density functions and the stochastic method, which was originally developed from Curl's model. The results show that the starting points of the low-temperature oxidation and ignition delay period are hardly affected by the equivalence-ratio variation; however, combustion duration increases with increasing variance of equivalence ratio. Furthermore, combustion duration is mainly affected by the non-homogeneity at the ignition and not very much affected by the mixing rate.

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.