微小重力場を利用した複数燃料液滴の自発点火における液滴間干渉の研究

抄録

As a fundamental study on the droplet-interaction effect in the spontaneous ignition of fuel spray, spontaneous ignition of an n-decane droplet pair rapidly inserted into hot air was experimentally studied in the ambient temperature range where the low-temperature oxidation reactions are active. In order to exclude the effect of buoyancy, the experiments were performed in microgravity. Two droplets suspended on 14 μm SiC fibers initially at room temperature were inserted into a hot furnace. Droplet diameter was 1 mm. First, temperature near the droplets were measured by thermocouples, and cool-flame and hot-flame ignition delays were evaluated. Cool-flame ignition delay increased with decreasing inter-droplet distance. This is supposed to be mainly caused by the mutual cooling effect. On the other hand, the duration between coolflame appearance and hot-flame appearance (second induction time) decreased with decreasing inter-droplet distance. This is supposedly because of higher cool-flame temperature caused by the enhanced fuel supply through duplicated fuel sources. Next, density field around a droplet pair was qualitatively observed by interferometry with a high-speed camera, and the locations of cool-flame and hot-flame appearances were detected. Cool flame appeared on the outer side of the droplet pair, and hot flame appeared on the inner side of the droplet pair, which corresponds with the discussion on ignition delays.