This study experimentally investigates the mechanism of the ignition of the supersonic liquid fuel jet by the visualization. NHexadecane\r\nhaving the cetane number of 100 was used as a liquid for the jet in order to enhance the ignition potential of the\r\nliquid fuel jet. Moreover, the heat column and the high intensity CO2 laser were applied to initiate the ignition. The ignition over\r\nthe liquid fuel jet was visualized by a high-speed digital video camera with a shadowgraph system. From the shadowgraph images,\r\nthe autoignition or ignition of the supersonic liquid fuel jet, at the velocity of 1,186 m/s which is a Mach number relative to the air\r\nof 3.41, did not take place.The ignition still did not occur, even though the heat column or the high intensity CO2 laser was alone\r\napplied. The attempt to initiate the ignition over the liquid fuel jet was achieved by applying both the heat column and the high\r\nintensity CO2 laser. Observing the signs of luminous spots or flames in the shadowgraph would readily indicate the presence of\r\nignitions. The mechanism of the ignition and combustion over the liquid fuel jet was clearly clarified. Moreover, it was found that\r\nthe ignition over the supersonic liquid fuel jet in this study was rather the force ignition than being the auto-ignition induced by\r\nshock wave heating.
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