Experimental investigation on the sputtering and micro-explosion of emulsion fuel droplets during impact on a heated surface

Micro-explosion has been concerned for decades due to its potential effect on fuel atomization and combustion. In this work, the characteristics of sputtering and micro-explosion induced by water-diesel emulsion fuel droplets impact on a heated surface under different water content (from 5% to 20% with an interval of 2.5%) and surface temperature conditions was investigated by a high speed camera synchronized with backlit technique. It was found that the secondary droplets was still heated by the environment to induce sputtering. It was observed the secondary droplets induced by sputtering would trigger further sputtering. Higher water content and higher temperature are necessary to induce sputtering and micro-explosion. The variation of an emulsion fuel droplet impacts on the surface from 100 °C to 320 °C was investigated. Typical Leidenfrost phenomenon was observed when the temperature was above the range when temperature was more than 300 °C. Various types of bubbles depending on the specific temperature value will generate when the surface temperature is below the range, while no bubble generates for neat diesel droplet.