Experimental study on nucleation and micro-explosion characteristics of emulsified heavy fuel oil droplets at elevated temperatures during evaporation

The application of emulsified fuels can improve atomization quality which mainly benefits from the micro -explosion phenomenon. To explore bubble behaviors and droplet micro-explosion characteristics of emulsified heavy fuel oil (HFO) droplets during evaporation, the suspended droplet method was adopted. A water content of 0-30 % was used at atmospheric pressure and ambient temperatures of 573-873 K. Three trigger conditions for heterogeneous nucleation in the emulsified HFO droplet were proposed based on the properties of emulsified HFO. The dual-mode micro-explosion of emulsified HFO was defined as local and global micro-explosion. It is of great interest to mention that dual-mode micro-explosion accompanied by a honeycomb-like structure was clarified for the first time. Based on the experimental results, the working conditions of the droplet breakup modes and the appearance of a honeycomb-like structure were summarized. A regression formula was introduced to express the dependence of micro-explosion intensity on ambient temperature and water content. The tem-perature characteristic curve of the evaporation process presented an obvious plateau, which was a typical feature of emulsified HFO droplets in the evaporation process. Secondary droplets that entrapped bubble nuclei inside were also captured with an occurrence of droplet micro-explosion. This experimental investigation on bubble behaviors and micro-explosion characteristics during evaporation is expected to provide guidance for the application of emulsified HFO.