Combustion and evaporation characteristics of fuel droplets containing suspended energetic nanoparticles

Nanofluid fuel is a novel concept and has drawn great attentions in combustion and propulsion community recently. The focus of this research is to gain a fundamental understanding of the combustion and evaporation characteristics of nanofluids fuels. This study starts with the investigation of the physical and chemical methods to form a homogenous and stable nanofluid with low levels of agglomeration and the morphology of nanostructures were characterized. Then, we investigated the combustion characteristics of nanofluid fuel droplets using high-speed photography with and without backlight respectively. Droplet diameters and temperature histories were simultaneously measured. The emphasis is to explore the effects of particle size, materials, loading rate, surfactant concentration and type of base fuel on droplet combustion characteristics. Besides the combustion characteristics, we also studied the effect of added nanostructures on the evaporation characteristics of nanofluid fuel droplets. The evaporation rates of nanofluid droplets under well-controlled convection and radiation were measured and the effect of particle size, materials, loading rate and type of base fuel on the evaporation rates were analyzed. Theoretical studies were conducted to understand the particle transportation and aggregation mechanisms in the nanofluids. The importance of different aggregation mechanisms was evaluated to explain the different combustion behavior of liquid fuels droplet with nano- and micron particles. Furthermore, the nanoparticle aggregation history was numerically modeled by solving population balance equation in order to understand the potential role of particle aggregation on droplet evaporation rate under convection. In addition, the radiative properties of various nanofluid fuels were determined theoretically and further validated by the experimental data from spectroscopy analysis. Then, their effects on droplet evaporation rates under radiation were determined quantitatively