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- The Addition of Particles to an Alternative Jet FuelPublication . Ferrão, Inês; Mendes, Miguel; Moita, A. S.; Silva, AndréThe expansion of the research on nanoscale particles demonstrates several advantages in terms of stability and an increased surface area to volume ratio compared to micron-sized particles. Based on this, the present work explores the addition of aluminum particles in hydrotreated vegetable oil (HVO), an alternative jet fuel. To evaluate the influence of particle sizes, nano and micron particles (40 nm and 5 μm) in a particle concentration of 0.5 wt.% were stably suspended in HVO. This study evaluates droplet combustion with an initial diameter of 250 μm in a drop tube furnace under different furnace temperatures (600, 800, 1000 °C). A high magnification lens coupled with a high-speed camera provides qualitative and quantitative data regarding droplet size evolution and micro-explosions. Pure HVO and Jet A-1 were also tested for comparison purposes. The results reveal that the addition of aluminum particles enhances the alternative jet fuel combustion. Furthermore, decreasing the particle size and increasing the furnace temperature enhances the burning rate compared to the pure HVO. Pure HVO presents a burning rate nearly to 1.75 mm2/s until t/D20 = 0.35 s/mm2 at T = 1000 °C. When nanoparticles are added to HVO in a particle concentration of 0.5 wt.%, an improvement of 24% in burning rate is noticed. Conventional jet fuel and pure HVO do not present any disruptive burning phenomena. However, when aluminum particles were added to HVO, micro-explosions were detected at the end of droplet lifetime, regardless of the particle size.
- Combustion characteristics of a single droplet of hydroprocessed vegetable oil blended with aluminum nanoparticles in a drop tube furnacePublication . Ferrão, Inês; Silva, André; Moita, A. S.; Mendes, Miguel; Costa, MárioThis study examines the burning characteristics and disruptive burning phenomena of single droplets of aluminum nanoparticles (n-Al) stably suspended in a biofuel (HVO). The biofuel used in the present work is a promising alternative fuel already tested in the aviation sector to reduce greenhouse gas and pollutant emissions. Experiments were conducted with two particle sizes (40nm and 70nm) and two particle concentrations (0.5 wt.% and 1.0 wt.%) to study its influence when added to the biofuel. The effect of size and concentration of the aluminum nanoparticles was studied at 1100 °C in a drop tube furnace. This experimental facility allows the study of combustion characteristics of falling droplets, ensuring there is no influence of the supporting fiber on the burning rate and disruptive burning phenomena occurrence. A CMOS high - speed camera coupled with a high magnification lens was used to evaluate the droplet size, burning rate, and micro-explosions. Based on this procedure, pure biofuel droplets were compared with those of biofuel blended with nanoparticles. The results suggest that the combustion characteristics of pure HVO can be enhanced with the addition of aluminum nanoparticles. Furthermore, by decreasing the particle size, a slight increase in the burning rate of nanofuels was noticed. Additionally, an increase in the particle concentration leads to a pronounced increase in the burning rate. The particle concentration also influences the delay and intensity of micro-explosions, disruptive burning phenomena detected at the end of the droplet lifetime.
- Single droplet combustion of aluminum nanoparticles added to a biofuel: effect of particle concentration and ambient temperaturePublication . Ferrão, Inês; Mendes, Miguel; Moita, A. S.; Silva, AndréThe fast expansion and growth of the aviation sector, coupled with the greenhouse gas andpollutant emissions, requires urgent solutions. A starting point to change this sector paradigmcould be a new energy source for aviation gas turbines, focused on potential carbon neutral fu-els, e.g., biofuels. A possible solution is nanoparticles addition to improve the biofuel propertiesand mitigate the problems inherent to their use. The present work experimentally evaluates thecombustion characteristics of single droplets of HVO (NExBTL) with aluminum nanoparticles.The ambient temperature was varied from600°Cto1000°C. Three particle concentrations (0.2,0.5, and 1.0 wt.%) were investigated with a fixed particle size of 40nm. This study examinedthe combustion of droplets with an initial diameter of 250μmusing a falling droplet method.The results reveal that for nanofuels, the droplet size evolution curve is not in agreement withD2– law and display a unique disruptive burning phenomenon at the end of the droplet life-time. It was noticed that the burning rate of biofuel is considerably enhanced with the addition ofnanoparticles, being the highest value for the nanofuel with a particle concentration of 1.0 wt.%.