Micro-Explosion of Compound Drops

In this study, compound drops were generated by using a coaxial nozzle in which the outer tube and the inner tube delivered different liquids. In comparison with an emulsion drop, a water-in-oil compound drop consists of a water core and an oil shell. There is an interface between water and oil inside of the compound drop. Owing to this distinct nature, combustion characteristics and micro-explosion phenomena of compound drops were examined in this study. The liquid tested in the experiment included dodecane, hexadecane, 95.5% ethanol and water. The water content of water-in-dodecane compound drop (beta(12)) varied from 25% to 85% in volume. The water content of water-in-hexadecane compound drop (beta(16)) was fixed at 25% and 40% in volume. The ethanol content of ethanol-in-dodecane compound drop (beta(e)) was fixed at 25% and 40% in volume. The drop diameter (d(i)) and the drop spacing (S/d(i)) was fixed at 500 mu m and 10, respectively. In the experiment, the variation of flame streak changed from yellow to blue flame with increasing the inner core water content of compound drop. The micro-explosion of compound drop had one model only. The micro-explosion phenomenon occurred because of bubble expansion from water (or ethanol) vapor inside the compound drop. The time history of micro-explosion from nucleation to bursting were in the order of beta(e) > beta(12)> beta(16). The micro-explosion intensity of compound drop were in the order beta(e) <= beta(12)< beta(16).