Effect of ambient temperature and water content on emulsified heavy fuel oil droplets evaporation: Evaporation enhancement by droplet puffing and micro-explosion

In this study, the evaporation characteristics of emulsified heavy fuel oil (HFO) with water content from 0 to 30 % at the ambient temperatures of 673, 773, and 873 K are experimentally studied. Three distinguishing phases can be clarified and summarized, including initial heating, fluctuation evaporation, and steady evaporation phases. The fluctuation evaporation phase involves the two sub-phases of heat equilibrium and secondary heating, which are first discovered in the evaporation of emulsified HFO. And the heat equilibrium sub-phase is the distinguishing feature of emulsified HFO from other blended fuels. The duration of the initial heating phase and the fluctuation evaporation phase decreases with the elevated ambient temperature but increases with rising water content. However, the variation of micro-explosion intensity with ambient temperature and water content is the opposite. The time consumed in the fluctuation evaporation phase determines the droplet lifetime. The difference between the evaporation characteristics of HFO and emulsified HFO is that the fluctuation evaporation phase of HFO is not distinct, which is due to the violent and frequent micro-explosion occurring in the emulsified HFO droplet. Consequently, the droplet lifetime of emulsified HFO is significantly shorter than that of HFO. Eventually, a regression formula for the dependences of droplet lifetime from temperature and water content is proposed, which can provide a reference for the practical application of emulsified HFO.

Automated summary

This study experimentally investigates the evaporation characteristics of emulsified heavy fuel oil (HFO) with varying water content. Three distinct phases are identified: initial heating, fluctuation evaporation, and steady evaporation. The fluctuation evaporation of emulsified HFO involves two sub-phases and is characterized by heat equilibrium, which is unique to this fuel type. The duration of the initial heating and fluctuation evaporation phases is influenced by ambient temperature and water content. The evaporation characteristics of HFO and emulsified HFO differ due to the occurrence of frequent micro-explosions in the latter, resulting in a significantly shorter droplet lifetime. A regression formula is proposed to establish the relationship between droplet lifetime, temperature, and water content for practical application.