Spontaneous Ignition of a Droplet Pair in Microgravity

概要

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As a fundamental study on the droplet-interaction effect in the fuel-spray ignition, spontaneous ignition of an n-decane droplet pair in hot air was experimentally studied. Two droplets initially at room temperature were brought into a hot furnace at atmospheric pressure. Droplet diameter was 1 mm. Three hot junctions of K-type thermocouples with a diameter of 25 μm were located near the droplet pair, and the cool-flame appearance was detected. The experiments were performed in microgravity in order to get rid of the effects of natural convection. Ignition delays and temperatures of cool flame were evaluated from the thermocouple outputs. Backlit droplet images were also recorded, and the vaporization rate was evaluated. Inter-droplet distance was varied, and ambient temperature (hot-air temperature) was fixed at either 600 K or 720 K, where only cool flame appears for n-decane droplets. Generally both cool-flame ignition delay and cool-flame temperature increased with decreasing inter-droplet distance, while cool-flame ignition delay took a minimal value at a certain inter-droplet distance.
THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCESの論文