Disruption and microexplosion mechanisms of burning alcohol droplets with the addition of nanoparticles
Journal
Combustion and Flame
Journal Volume
256
Date Issued
2023-10-01
Author(s)
Lai, Yen Wei
Abstract
Microexplosions of burning liquid fuels have been actively investigated and considered due to the advantage for substantially increasing the overall burning rate. This study concerns possible control of microexplosion occurrence by adding nanoparticles in alcohol fuel without effects of surfactant and ignitable particles as usually seen in the literature. In addition, the essential characteristics and differences between various particles on combustion are discussed. Specifically, we have added three types of ceramic nanoparticles into butanol and isopropanol droplets under different convection environments, i.e., forced convection and natural convection in normal gravity, and free convection in microgravity. A suspended droplet method was performed under convection-free and natural convective conditions while a free-falling droplet method provided a forced convection environment. It was observed that the combustion characteristics of droplets changed from extinction to burnout or from burnout to microexplosion by using different base fuels, by increasing the intensity of flow convection, or by using different kinds of nanoparticles. During combustion, droplets would deform due to the presence of gelation in the outer layer when Al2O3 or SiO2 nanoparticles were added, but not for TiO2. This yielded one of the key factors leading to microexplosions, in addition to the amount of heat absorption during the burning. For the latter, specifically, microexplosions happened when butanol/SiO2 droplets were tested, but not for butanol/Al2O3 droplets. By comparing the infrared absorptivity of Al2O3 and SiO2, distinct amount of absorbed infrared radiation was demonstrated. Such a difference in heat absorption was also key to the creation of microexplosion. As a consequence, microexplosions could be generated when nanoparticles were added into the fuel and formed gelation on the droplet surface, which trapped bubbles in the droplet, while sufficient heat was absorbed by the particles during the burning. The resulted consumption rate had increased by 46% compared to that of pure fuel.
Subjects
Alcohol | Droplet combustion | Heterogeneous | Microexplosion | Nanoparticle
SDGs
Type
journal article