A Study of the Autoignition Process of a Diesel Spray via High Speed Visualization 920108

In this paper we present photographic and pressure data that describe the autoignition and combustion processes of transient fuel sprays under diesel-like conditions. The results were obtained in a constant-volume vessel that allowed complete optical access to the diesel spray ignition/combustion process. The combination of complete optical access and schlieren/luminosity visualization presents a unique view of the spray. From the data, a narrative of the features of diesel spray autoignition and combustion is constructed. Comparison of events at different gas-phase temperatures shows the effect of shifting the chemical induction time relative to the fluid mechanic transport time.
The data show that a key feature of the autoignition process is the formation and shedding of fuel eddies along the edges of the spray jet. These eddies provide an environment conducive to chemical reaction, without the disruptive effects of the spray core fluid mechanics. We speculate, based on our observations, that it is within these eddies that the initial sites of autoignition occur.


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